Merge pull request #179 from hermeznetwork/feature/api-exits

Impl exit edpoint and refactor pagination

api/dbtoapistructs.go

@@ -7,36 +7,52 @@ import (
 
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/hermeznetwork/hermez-node/db"
 	"github.com/hermeznetwork/hermez-node/db/historydb"
 	"github.com/iden3/go-iden3-crypto/babyjub"
+	"github.com/iden3/go-merkletree"
 )
 
-// Commons of the API
+type errorMsg struct {
+	Message string
+}
 
-type pagination struct {
-	TotalItems       int `json:"totalItems"`
-	LastReturnedItem int `json:"lastReturnedItem"`
+func bjjToString(bjj *babyjub.PublicKey) string {
+	pkComp := [32]byte(bjj.Compress())
+	sum := pkComp[0]
+	for i := 1; i < len(pkComp); i++ {
+		sum += pkComp[i]
+	}
+	bjjSum := append(pkComp[:], sum)
+	return "hez:" + base64.RawURLEncoding.EncodeToString(bjjSum)
 }
 
-//nolint:govet this is a temp patch to avoid running the test
-type paginationer interface {
-	GetPagination() pagination
-	Len() int
+func ethAddrToHez(addr ethCommon.Address) string {
+	return "hez:" + addr.String()
 }
 
-type errorMsg struct {
-	Message string
+func idxToHez(idx common.Idx, tokenSymbol string) string {
+	return "hez:" + tokenSymbol + ":" + strconv.Itoa(int(idx))
 }
 
-// History Tx related
+// History Tx
 
 type historyTxsAPI struct {
 	Txs        []historyTxAPI `json:"transactions"`
-	Pagination pagination     `json:"pagination"`
+	Pagination *db.Pagination `json:"pagination"`
 }
 
-func (htx *historyTxsAPI) GetPagination() pagination { return htx.Pagination }
-func (htx *historyTxsAPI) Len() int                  { return len(htx.Txs) }
+func (htx *historyTxsAPI) GetPagination() *db.Pagination {
+	if htx.Txs[0].ItemID < htx.Txs[len(htx.Txs)-1].ItemID {
+		htx.Pagination.FirstReturnedItem = htx.Txs[0].ItemID
+		htx.Pagination.LastReturnedItem = htx.Txs[len(htx.Txs)-1].ItemID
+	} else {
+		htx.Pagination.LastReturnedItem = htx.Txs[0].ItemID
+		htx.Pagination.FirstReturnedItem = htx.Txs[len(htx.Txs)-1].ItemID
+	}
+	return htx.Pagination
+}
+func (htx *historyTxsAPI) Len() int { return len(htx.Txs) }
 
 type l1Info struct {
 	ToForgeL1TxsNum       *int64   `json:"toForgeL1TransactionsNum"`
@@ -57,6 +73,7 @@ type l2Info struct {
 type historyTxAPI struct {
 	IsL1        string              `json:"L1orL2"`
 	TxID        string              `json:"id"`
+	ItemID      int                 `json:"itemId"`
 	Type        common.TxType       `json:"type"`
 	Position    int                 `json:"position"`
 	FromIdx     *string             `json:"fromAccountIndex"`
@@ -75,6 +92,7 @@ func historyTxsToAPI(dbTxs []historydb.HistoryTx) []historyTxAPI {
 	for i := 0; i < len(dbTxs); i++ {
 		apiTx := historyTxAPI{
 			TxID:        dbTxs[i].TxID.String(),
+			ItemID:      dbTxs[i].ItemID,
 			Type:        dbTxs[i].Type,
 			Position:    dbTxs[i].Position,
 			ToIdx:       idxToHez(dbTxs[i].ToIdx, dbTxs[i].TokenSymbol),
@@ -124,20 +142,60 @@ func historyTxsToAPI(dbTxs []historydb.HistoryTx) []historyTxAPI {
 	return apiTxs
 }
 
-func bjjToString(bjj *babyjub.PublicKey) string {
-	pkComp := [32]byte(bjj.Compress())
-	sum := pkComp[0]
-	for i := 1; i < len(pkComp); i++ {
-		sum += pkComp[i]
-	}
-	bjjSum := append(pkComp[:], sum)
-	return "hez:" + base64.RawURLEncoding.EncodeToString(bjjSum)
+// Exit
+
+type exitsAPI struct {
+	Exits      []exitAPI      `json:"exits"`
+	Pagination *db.Pagination `json:"pagination"`
 }
 
-func ethAddrToHez(addr ethCommon.Address) string {
-	return "hez:" + addr.String()
+func (e *exitsAPI) GetPagination() *db.Pagination {
+	if e.Exits[0].ItemID < e.Exits[len(e.Exits)-1].ItemID {
+		e.Pagination.FirstReturnedItem = e.Exits[0].ItemID
+		e.Pagination.LastReturnedItem = e.Exits[len(e.Exits)-1].ItemID
+	} else {
+		e.Pagination.LastReturnedItem = e.Exits[0].ItemID
+		e.Pagination.FirstReturnedItem = e.Exits[len(e.Exits)-1].ItemID
+	}
+	return e.Pagination
+}
+func (e *exitsAPI) Len() int { return len(e.Exits) }
+
+type exitAPI struct {
+	ItemID                 int                             `json:"itemId"`
+	BatchNum               common.BatchNum                 `json:"batchNum"`
+	AccountIdx             string                          `json:"accountIndex"`
+	MerkleProof            *merkletree.CircomVerifierProof `json:"merkleProof"`
+	Balance                string                          `json:"balance"`
+	InstantWithdrawn       *int64                          `json:"instantWithdrawn"`
+	DelayedWithdrawRequest *int64                          `json:"delayedWithdrawRequest"`
+	DelayedWithdrawn       *int64                          `json:"delayedWithdrawn"`
+	Token                  historydb.TokenRead             `json:"token"`
 }
 
-func idxToHez(idx common.Idx, tokenSymbol string) string {
-	return "hez:" + tokenSymbol + ":" + strconv.Itoa(int(idx))
+func historyExitsToAPI(dbExits []historydb.HistoryExit) []exitAPI {
+	apiExits := []exitAPI{}
+	for i := 0; i < len(dbExits); i++ {
+		apiExits = append(apiExits, exitAPI{
+			ItemID:                 dbExits[i].ItemID,
+			BatchNum:               dbExits[i].BatchNum,
+			AccountIdx:             idxToHez(dbExits[i].AccountIdx, dbExits[i].TokenSymbol),
+			MerkleProof:            dbExits[i].MerkleProof,
+			Balance:                dbExits[i].Balance.String(),
+			InstantWithdrawn:       dbExits[i].InstantWithdrawn,
+			DelayedWithdrawRequest: dbExits[i].DelayedWithdrawRequest,
+			DelayedWithdrawn:       dbExits[i].DelayedWithdrawn,
+			Token: historydb.TokenRead{
+				TokenID:     dbExits[i].TokenID,
+				EthBlockNum: dbExits[i].TokenEthBlockNum,
+				EthAddr:     dbExits[i].TokenEthAddr,
+				Name:        dbExits[i].TokenName,
+				Symbol:      dbExits[i].TokenSymbol,
+				Decimals:    dbExits[i].TokenDecimals,
+				USD:         dbExits[i].TokenUSD,
+				USDUpdate:   dbExits[i].TokenUSDUpdate,
+			},
+		})
+	}
+	return apiExits
 }

api/handlers.go

@@ -2,23 +2,25 @@ package api
 
 import (
 	"database/sql"
-	"errors"
 	"net/http"
 
 	"github.com/gin-gonic/gin"
+	"github.com/hermeznetwork/hermez-node/db/historydb"
 )
 
-// maxLimit is the max permited items to be returned in paginated responses
-const maxLimit uint = 2049
+const (
+	// maxLimit is the max permited items to be returned in paginated responses
+	maxLimit uint = 2049
 
-// dfltLast indicates how paginated endpoints use the query param last if not provided
-const dfltLast = false
+	// dfltOrder indicates how paginated endpoints are ordered if not specified
+	dfltOrder = historydb.OrderAsc
 
-// dfltLimit indicates the limit of returned items in paginated responses if the query param limit is not provided
-const dfltLimit uint = 20
+	// dfltLimit indicates the limit of returned items in paginated responses if the query param limit is not provided
+	dfltLimit uint = 20
 
-// 2^32 -1
-const maxUint32 = 4294967295
+	// 2^32 -1
+	maxUint32 = 4294967295
+)
 
 func postAccountCreationAuth(c *gin.Context) {
 
@@ -45,45 +47,71 @@ func getAccount(c *gin.Context) {
 }
 
 func getExits(c *gin.Context) {
-
-}
-
-func getExit(c *gin.Context) {
-
-}
-
-func getHistoryTxs(c *gin.Context) {
 	// Get query parameters
-	// TokenID
-	tokenID, err := parseQueryUint("tokenId", nil, 0, maxUint32, c)
+	// Account filters
+	tokenID, addr, bjj, idx, err := parseAccountFilters(c)
 	if err != nil {
 		retBadReq(err, c)
 		return
 	}
-	// Hez Eth addr
-	addr, err := parseQueryHezEthAddr(c)
+	// BatchNum
+	batchNum, err := parseQueryUint("batchNum", nil, 0, maxUint32, c)
 	if err != nil {
 		retBadReq(err, c)
 		return
 	}
-	// BJJ
-	bjj, err := parseQueryBJJ(c)
+	// Pagination
+	fromItem, order, limit, err := parsePagination(c)
 	if err != nil {
 		retBadReq(err, c)
 		return
 	}
-	if addr != nil && bjj != nil {
-		retBadReq(errors.New("bjj and hermezEthereumAddress params are incompatible"), c)
+
+	// Fetch exits from historyDB
+	exits, pagination, err := h.GetExits(
+		addr, bjj, tokenID, idx, batchNum, fromItem, limit, order,
+	)
+	if err != nil {
+		retSQLErr(err, c)
+		return
+	}
+
+	// Build succesfull response
+	apiExits := historyExitsToAPI(exits)
+	c.JSON(http.StatusOK, &exitsAPI{
+		Exits:      apiExits,
+		Pagination: pagination,
+	})
+}
+
+func getExit(c *gin.Context) {
+	// Get batchNum and accountIndex
+	batchNum, err := parseParamUint("batchNum", nil, 0, maxUint32, c)
+	if err != nil {
+		retBadReq(err, c)
 		return
 	}
-	// Idx
-	idx, err := parseIdx(c)
+	idx, err := parseParamIdx(c)
 	if err != nil {
 		retBadReq(err, c)
 		return
 	}
-	if idx != nil && (addr != nil || bjj != nil || tokenID != nil) {
-		retBadReq(errors.New("accountIndex is incompatible with BJJ, hermezEthereumAddress and tokenId"), c)
+	// Fetch tx from historyDB
+	exit, err := h.GetExit(batchNum, idx)
+	if err != nil {
+		retSQLErr(err, c)
+		return
+	}
+	apiExits := historyExitsToAPI([]historydb.HistoryExit{*exit})
+	// Build succesfull response
+	c.JSON(http.StatusOK, apiExits[0])
+}
+
+func getHistoryTxs(c *gin.Context) {
+	// Get query parameters
+	tokenID, addr, bjj, idx, err := parseAccountFilters(c)
+	if err != nil {
+		retBadReq(err, c)
 		return
 	}
 	// BatchNum
@@ -99,15 +127,15 @@ func getHistoryTxs(c *gin.Context) {
 		return
 	}
 	// Pagination
-	offset, last, limit, err := parsePagination(c)
+	fromItem, order, limit, err := parsePagination(c)
 	if err != nil {
 		retBadReq(err, c)
 		return
 	}
 
 	// Fetch txs from historyDB
-	txs, totalItems, err := h.GetHistoryTxs(
-		addr, bjj, tokenID, idx, batchNum, txType, offset, limit, *last,
+	txs, pagination, err := h.GetHistoryTxs(
+		addr, bjj, tokenID, idx, batchNum, txType, fromItem, limit, order,
 	)
 	if err != nil {
 		retSQLErr(err, c)
@@ -116,21 +144,28 @@ func getHistoryTxs(c *gin.Context) {
 
 	// Build succesfull response
 	apiTxs := historyTxsToAPI(txs)
-	lastRet := int(*offset) + len(apiTxs) - 1
-	if *last {
-		lastRet = totalItems - 1
-	}
 	c.JSON(http.StatusOK, &historyTxsAPI{
-		Txs: apiTxs,
-		Pagination: pagination{
-			TotalItems:       totalItems,
-			LastReturnedItem: lastRet,
-		},
+		Txs:        apiTxs,
+		Pagination: pagination,
 	})
 }
 
 func getHistoryTx(c *gin.Context) {
-
+	// Get TxID
+	txID, err := parseParamTxID(c)
+	if err != nil {
+		retBadReq(err, c)
+		return
+	}
+	// Fetch tx from historyDB
+	tx, err := h.GetHistoryTx(txID)
+	if err != nil {
+		retSQLErr(err, c)
+		return
+	}
+	apiTxs := historyTxsToAPI([]historydb.HistoryTx{*tx})
+	// Build succesfull response
+	c.JSON(http.StatusOK, apiTxs[0])
 }
 
 func getBatches(c *gin.Context) {

api/parsers.go

@@ -9,56 +9,49 @@ import (
 
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
+	"github.com/hermeznetwork/hermez-node/db/historydb"
 	"github.com/iden3/go-iden3-crypto/babyjub"
 )
 
+// Query parsers
+
 type querier interface {
 	Query(string) string
 }
 
-func parsePagination(c querier) (*uint, *bool, *uint, error) {
-	// Offset
-	offset := new(uint)
-	*offset = 0
-	offset, err := parseQueryUint("offset", offset, 0, maxUint32, c)
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	// Last
-	last := new(bool)
-	*last = dfltLast
-	last, err = parseQueryBool("last", last, c)
+func parsePagination(c querier) (fromItem *uint, order string, limit *uint, err error) {
+	// FromItem
+	fromItem, err = parseQueryUint("fromItem", nil, 0, maxUint32, c)
 	if err != nil {
-		return nil, nil, nil, err
+		return nil, "", nil, err
 	}
-	if *last && (offset != nil && *offset > 0) {
-		return nil, nil, nil, errors.New(
-			"last and offset are incompatible, provide only one of them",
+	// Order
+	order = dfltOrder
+	const orderName = "order"
+	orderStr := c.Query(orderName)
+	if orderStr != "" && !(orderStr == historydb.OrderAsc || historydb.OrderDesc == orderStr) {
+		return nil, "", nil, errors.New(
+			"order must have the value " + historydb.OrderAsc + " or " + historydb.OrderDesc,
 		)
 	}
+	if orderStr == historydb.OrderAsc {
+		order = historydb.OrderAsc
+	} else if orderStr == historydb.OrderDesc {
+		order = historydb.OrderDesc
+	}
 	// Limit
-	limit := new(uint)
+	limit = new(uint)
 	*limit = dfltLimit
 	limit, err = parseQueryUint("limit", limit, 1, maxLimit, c)
 	if err != nil {
-		return nil, nil, nil, err
+		return nil, "", nil, err
 	}
-	return offset, last, limit, nil
+	return fromItem, order, limit, nil
 }
 
 func parseQueryUint(name string, dflt *uint, min, max uint, c querier) (*uint, error) { //nolint:SA4009 res may be not overwriten
 	str := c.Query(name)
-	if str != "" {
-		resInt, err := strconv.Atoi(str)
-		if err != nil || resInt < 0 || resInt < int(min) || resInt > int(max) {
-			return nil, fmt.Errorf(
-				"Inavlid %s. Must be an integer within the range [%d, %d]",
-				name, min, max)
-		}
-		res := uint(resInt)
-		return &res, nil
-	}
-	return dflt, nil
+	return stringToUint(str, name, dflt, min, max)
 }
 
 func parseQueryBool(name string, dflt *bool, c querier) (*bool, error) { //nolint:SA4009 res may be not overwriten
@@ -183,19 +176,105 @@ func parseQueryTxType(c querier) (*common.TxType, error) {
 	)
 }
 
-func parseIdx(c querier) (*uint, error) {
+func parseIdx(c querier) (*common.Idx, error) {
 	const name = "accountIndex"
-	addrStr := c.Query(name)
-	if addrStr == "" {
+	idxStr := c.Query(name)
+	return stringToIdx(idxStr, name)
+}
+
+func parseAccountFilters(c querier) (*common.TokenID, *ethCommon.Address, *babyjub.PublicKey, *common.Idx, error) {
+	// TokenID
+	tid, err := parseQueryUint("tokenId", nil, 0, maxUint32, c)
+	if err != nil {
+		return nil, nil, nil, nil, err
+	}
+	var tokenID *common.TokenID
+	if tid != nil {
+		tokenID = new(common.TokenID)
+		*tokenID = common.TokenID(*tid)
+	}
+	// Hez Eth addr
+	addr, err := parseQueryHezEthAddr(c)
+	if err != nil {
+		return nil, nil, nil, nil, err
+	}
+	// BJJ
+	bjj, err := parseQueryBJJ(c)
+	if err != nil {
+		return nil, nil, nil, nil, err
+	}
+	if addr != nil && bjj != nil {
+		return nil, nil, nil, nil,
+			errors.New("bjj and hermezEthereumAddress params are incompatible")
+	}
+	// Idx
+	idx, err := parseIdx(c)
+	if err != nil {
+		return nil, nil, nil, nil, err
+	}
+	if idx != nil && (addr != nil || bjj != nil || tokenID != nil) {
+		return nil, nil, nil, nil,
+			errors.New("accountIndex is incompatible with BJJ, hermezEthereumAddress and tokenId")
+	}
+	return tokenID, addr, bjj, idx, nil
+}
+
+// Param parsers
+
+type paramer interface {
+	Param(string) string
+}
+
+func parseParamTxID(c paramer) (common.TxID, error) {
+	const name = "id"
+	txIDStr := c.Param(name)
+	if txIDStr == "" {
+		return common.TxID{}, fmt.Errorf("%s is required", name)
+	}
+	txID, err := common.NewTxIDFromString(txIDStr)
+	if err != nil {
+		return common.TxID{}, fmt.Errorf("invalid %s", name)
+	}
+	return txID, nil
+}
+
+func parseParamIdx(c paramer) (*common.Idx, error) {
+	const name = "accountIndex"
+	idxStr := c.Param(name)
+	return stringToIdx(idxStr, name)
+}
+
+func parseParamUint(name string, dflt *uint, min, max uint, c paramer) (*uint, error) { //nolint:SA4009 res may be not overwriten
+	str := c.Param(name)
+	return stringToUint(str, name, dflt, min, max)
+}
+
+func stringToIdx(idxStr, name string) (*common.Idx, error) {
+	if idxStr == "" {
 		return nil, nil
 	}
-	splitted := strings.Split(addrStr, ":")
+	splitted := strings.Split(idxStr, ":")
 	const expectedLen = 3
-	if len(splitted) != expectedLen {
+	if len(splitted) != expectedLen || splitted[0] != "hez" {
 		return nil, fmt.Errorf(
 			"invalid %s, must follow this: hez:<tokenSymbol>:index", name)
 	}
+	// TODO: check that the tokenSymbol match the token related to the account index
 	idxInt, err := strconv.Atoi(splitted[2])
-	idx := uint(idxInt)
+	idx := common.Idx(idxInt)
 	return &idx, err
 }
+
+func stringToUint(uintStr, name string, dflt *uint, min, max uint) (*uint, error) {
+	if uintStr != "" {
+		resInt, err := strconv.Atoi(uintStr)
+		if err != nil || resInt < 0 || resInt < int(min) || resInt > int(max) {
+			return nil, fmt.Errorf(
+				"Inavlid %s. Must be an integer within the range [%d, %d]",
+				name, min, max)
+		}
+		res := uint(resInt)
+		return &res, nil
+	}
+	return dflt, nil
+}

api/parsers_test.go

@@ -111,52 +111,46 @@ func TestParseQueryBool(t *testing.T) {
 func TestParsePagination(t *testing.T) {
 	c := &queryParser{}
 	c.m = make(map[string]string)
-	// Offset out of range
-	c.m["offset"] = "-1"
+	// fromItem out of range
+	c.m["fromItem"] = "-1"
 	_, _, _, err := parsePagination(c)
 	assert.Error(t, err)
-	c.m["offset"] = strconv.Itoa(maxUint32 + 1)
+	c.m["fromItem"] = strconv.Itoa(maxUint32 + 1)
 	_, _, _, err = parsePagination(c)
 	assert.Error(t, err)
-	c.m["offset"] = ""
-	// Limit out of range
-	c.m["limit"] = "0"
+	c.m["fromItem"] = ""
+	// Bad order
+	c.m["order"] = "0"
 	_, _, _, err = parsePagination(c)
 	assert.Error(t, err)
-	c.m["limit"] = strconv.Itoa(int(maxLimit) + 1)
-	_, _, _, err = parsePagination(c)
-	assert.Error(t, err)
-	c.m["limit"] = ""
-	// Last and offset
-	c.m["offset"] = "1"
-	c.m["last"] = "true"
+	c.m["order"] = strconv.Itoa(int(maxLimit) + 1)
 	_, _, _, err = parsePagination(c)
 	assert.Error(t, err)
 	// Default
-	c.m["offset"] = ""
-	c.m["last"] = ""
+	c.m["fromItem"] = ""
+	c.m["order"] = ""
 	c.m["limit"] = ""
-	offset, last, limit, err := parsePagination(c)
+	fromItem, order, limit, err := parsePagination(c)
 	assert.NoError(t, err)
-	assert.Equal(t, 0, int(*offset))
-	assert.Equal(t, dfltLast, *last)
+	assert.Nil(t, fromItem)
+	assert.Equal(t, dfltOrder, order)
 	assert.Equal(t, dfltLimit, *limit)
 	// Correct
-	c.m["offset"] = ""
-	c.m["last"] = "true"
+	c.m["fromItem"] = ""
+	c.m["order"] = "ASC"
 	c.m["limit"] = "25"
-	offset, last, limit, err = parsePagination(c)
+	fromItem, order, limit, err = parsePagination(c)
 	assert.NoError(t, err)
-	assert.Equal(t, 0, int(*offset))
-	assert.True(t, *last)
+	assert.Nil(t, fromItem)
+	assert.Equal(t, "ASC", order)
 	assert.Equal(t, 25, int(*limit))
-	c.m["offset"] = "25"
-	c.m["last"] = "false"
+	c.m["fromItem"] = "25"
+	c.m["order"] = "DESC"
 	c.m["limit"] = "50"
-	offset, last, limit, err = parsePagination(c)
+	fromItem, order, limit, err = parsePagination(c)
 	assert.NoError(t, err)
-	assert.Equal(t, 25, int(*offset))
-	assert.False(t, *last)
+	assert.Equal(t, 25, int(*fromItem))
+	assert.Equal(t, "DESC", order)
 	assert.Equal(t, 50, int(*limit))
 }
 

api/swagger.yml

@@ -7,31 +7,27 @@ info:
     * Explorer: List transactions, slots, batches, ...
     * Exchange integrations
     
+    ### Pagination
+    
+    #### Usage
+
     All the endpoints that return a list of undefined size use pagination. Unless the opposite is explicitly said.
-    All the retunred items are ordered by ascending chronological order. 
-    This may not be trivial to deduce as the atributes used to order are not timestamps but the protocol ensures that those atributes follow the mentioned chronological order.
-    Each endpoint description clarify this in the `offset` description.
+    In order to use pagination, three query parameters are used:
+    * `fromItem`: indicates the first item to be returned. In general, this parameter shouldn't be provided in the first call to the endpoint, and use the `itemId` of the last returned item (+/-) 1, if the order is (ascending/descending).
+    * `order`: all pginated items are ordered chronologicaly. However the specific fields to guarantee this order depend on each endpoint. For this purpose, `itemId` is used (itemId follows ascending chronological order except for unforged L1 user transactions). If the parameter is not provided, ascending order will be used by default. 
+    * `limit`: maximum amount of items to include in each response. Default is 20, maximum 2049.
+    
+    Responses for those endpoint will always include a `pagination` object. This object includes the total amount of items that the endpoint will return at a given time with the given filters. Apart from that, it also includes the `itemId` of the last and first items that will be returned (not in a single response but within the total items). These two properties can be used to know when to stop querying. 
 
-    The response of the calls to these endpoints will always include a `pagination` object that includes `totalItems` and `lastReturnedItem`.
-    To iterate over the items the following query parameters are used:
-      - `offset`: Indicates the first item that will be returned. Defaul 0. Incompatible with `last`.
-      - `limit`: Indicates the maximum number of returned items. Default 20. Maximum 2049.
-      - `last`: When true the last `limit` items are returned. Default false. Incompatible with `offset`.
+    #### Reorgs and safetyness
 
-    Iterate items in ascending chronological order:
+    Since all the items are ordered chronologicaly, there are no safety problems when fetching items in ascending order, except for reorgs (more on this later).
+    On the other hand, when iterating in descending order, new items will be added at the beginning. This doesn't cause any safety problem, but to get those new items, it's necessary to start queryng without the `fromItem` set to `pagination.lastItem`.
+    To handle reorgs, the `itemId` can be used since it will change. This is important since other identifiers may be the same but with different content. As an example, if the batch 424 get's reorged, it will be deleted, but eventualy, a new batch 424 will appear with potentialy different content.
 
-      1. Call the endpoint with no `offset` nor `last`.
-      2. Call the endpoint with `offset=<lastReturnedItem + 1>` until `lastReturnedItem == totalItems - 1`.
+    ### Signatures
 
-    Iterate items in descending chronological order:
-
-      1. Call the endpoint with `last`.
-      2. Call the endpoint with `offset=<min(0, lastReturnedItem - 2*limit)>`. Once the `calculated offset == 0`, it will be known that that call will return the first item and therefore no subsequent calls need to be done.
-    If the `totalItems` change while iterating, it means that new items have been added at the end of the list. To fetch this items, use the following: `offset=<first received lastReturnedItem + 1>`, and from there iterate as decribed in *Iterate items in ascending chronological order*.
-    
-    **Note:** The returned list will alway be in ascending chronlogical order, so the returned arrays must be iterated from end to start in order to achieve reverse chronological order.
-    
-    **Note:** Pagination safety can be affected by Ethereum reorgs. In most of the cases this means that the last page can be changed, but older items should be safe.
+    The POST endpoint require to be signed using BabyJubJub or Ethereum keys. TODO: add references to libraries / examples / ...
 
   version: "0.0.1"
   title: Hermez Network API
@@ -164,20 +160,22 @@ paths:
             type: string
             description: Comma separated list of token identifiers.
             example: "3,87,91"
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: accounts will be ordered by increasing account index.
-            - Default first item: the first account to be returned will be the one that has the smallest account index.
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Accounts will be ordered by increasing account index.
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -258,6 +256,12 @@ paths:
       description: Get exit information. This information is required to perform a withdraw.
       operationId: getExits
       parameters:
+        - name: tokenId
+          in: query
+          required: false
+          description: Only get exits of specific token
+          schema:
+            $ref: '#/components/schemas/TokenId'
         - name: hezEthereumAddress
           in: query
           description: Get exits associated to a Ethereum address. Incompatible with query `BJJ` and `accountIndex`.
@@ -272,7 +276,7 @@ paths:
             $ref: '#/components/schemas/BJJ'
         - name: accountIndex
           in: query
-          description: Get exits associated to a specific account. Incompatible with queries `hezEthereumAddress` and `BJJ`.
+          description: Get exits associated to a specific account. Incompatible with queries `tokenId`, `hezEthereumAddress` and `BJJ`.
           required: false
           schema:
             $ref: '#/components/schemas/AccountIndex'
@@ -282,20 +286,22 @@ paths:
           required: false
           schema:
             $ref: '#/components/schemas/BatchNum'
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: exits will be ordered by increasing (batchNum, accountIndex).
-            - Default first item: the first exit to be returned will be the one that has the smallest (baychNum, accountIndex).
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Exits will be ordered by increasing (batchNum, accountIndex).
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -459,7 +465,7 @@ paths:
       description: >-
         Get historical transactions. This endpoint will return all the different types of transactions except for:
           - Transactions that are still in the transaction pool of any coordinator. These transactions can be fetched using `GET /transactions-pool/{id}`.
-          - L1 transactions that have not been forged yet. These transactions can be fetched using `GET /transactions-history/{id}`.
+          - L1 transactions sent by users that have not been forged yet. These transactions can be fetched using `GET /transactions-history/{id}`.
       operationId: getHistoryTxs
       parameters:
         - name: tokenId
@@ -498,20 +504,22 @@ paths:
           description: Only get transactions of a specific type.
           schema:
             $ref: '#/components/schemas/TransactionType'
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: History transactions will be ordered by increasing (batchNum, position).
-            - Default first item: the first transaction to be returned will be the one that has the smallest (batchNum, position).
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. History transactions will be ordered by (batchNum, position).
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -612,20 +620,22 @@ paths:
           description: Include only batches forged by `forgerAddr`
           schema:
             $ref: '#/components/schemas/EthereumAddress'
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: batches will be ordered by increasing `batchNum`.
-            - Default first item: the first batch to be returned will be the one that has the smallest `batchNum`.
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Batches will be ordered by increasing `batchNum`.
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -773,20 +783,22 @@ paths:
           description: If set to true, only include slots whose auction has finished.
           schema:
             type: boolean
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: slots will be ordered by increasing `slotNum`.
-            - Default first item: the first slot to be returned will be the one that has the smallest `slotNum`.
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Slots will be ordered by increasing `slotNum`.
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -880,20 +892,22 @@ paths:
           required: false
           schema:
             $ref: '#/components/schemas/EthereumAddress'
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: bids will be ordered by increasing (slotNum, bidValue)`.
-            - Default first item: the first bid to be returned will be the one that has the smallest (slotNum, bidValue).
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Bids will be ordered by increasing (slotNum, bidValue)`.
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -1031,20 +1045,22 @@ paths:
           description: Include token(s) by their names (or a substring of the name).
           schema:
             type: string
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: tokens will be ordered by increasing tokenID.
-            - Default first item: the first token to be returned will be the one that has the smallest tokenID.
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Tokens will be ordered by increasing tokenID.
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -1146,20 +1162,22 @@ paths:
       description: Get information about coordinators.
       operationId: getCoordinators
       parameters:
-        - name: offset
+        - name: fromItem
           in: query
           required: false
-          description: |
-            - Order: coordinators will be ordered by increasing (ethereumBlock, forgerAddr).
-            - Default first item: the first token to be returned will be the one that has the smallest (ethereumBlock, forgerAddr).
+          description: Indicates the desired first item (using the itemId property) to be included in the response.
           schema:
             type: number
-        - name: last
+        - name: order
           in: query
           required: false
-          description: Get the last page.
+          description: Order of the returned items. Coordinators will be ordered by increasing (ethereumBlock, forgerAddr).
           schema:
-            type: boolean
+            type: string
+            default: ASC
+            enum:
+                - ASC
+                - DESC
         - name: limit
           in: query
           required: false
@@ -1228,13 +1246,16 @@ paths:
                 $ref: '#/components/schemas/Error500'
 components:
   schemas:
+    ItemId:
+      type: integer
+      description: Position of the item in the DB. This is useful for pagination, but has  nothing to do with the protocol.
     PostPoolL2Transaction:
       type: object
       properties:
         id:
           $ref: '#/components/schemas/TransactionId'
         type:
-          $ref: '#/components/schemas/TransactionType'
+          $ref: '#/components/schemas/TransactionTypeL2'
         tokenId:
           $ref: '#/components/schemas/TokenId'
         fromAccountIndex:
@@ -1341,7 +1362,7 @@ components:
         id:
           $ref: '#/components/schemas/TransactionId'
         type:
-          $ref: '#/components/schemas/TransactionType'
+          $ref: '#/components/schemas/TransactionTypeL2'
         fromAccountIndex:
           $ref: '#/components/schemas/AccountIndex'
         toAccountIndex:
@@ -1480,6 +1501,14 @@ components:
       - ForceExit
       - TransferToEthAddr
       - TransferToBJJ
+    TransactionTypeL2:
+      type: string
+      description: Type of transaction.
+      enum:
+      - Exit
+      - Transfer
+      - TransferToEthAddr
+      - TransferToBJJ
     TokenId:
       type: integer
       description: Identifier of a token registered in the network.
@@ -1556,6 +1585,8 @@ components:
             - L2
         id:
           $ref: '#/components/schemas/TransactionId'
+        itemId:
+          $ref: '#/components/schemas/ItemId'
         type:
           $ref: '#/components/schemas/TransactionType'
         position:
@@ -1655,6 +1686,7 @@ components:
       required:
         - L1orL2
         - id
+        - itemId
         - type
         - position
         - fromAccountIndex
@@ -1943,29 +1975,87 @@ components:
             - example: 7394
         accountIndex:
           $ref: '#/components/schemas/AccountIndex'
+        itemId:
+          $ref: '#/components/schemas/ItemId'
         merkleProof:
-          type: string
+          type: object
           description: Existence proof of a leaf in a given Merkle Root. Encoded as hexadecimal string.
-          example: "0x347089321de8971320489793a823470918fffeab"
+          properties:
+              Root:
+                type: array
+                items: 
+                  type: integer
+              Siblings:
+                type: array
+                items:
+                  type: integer
+              OldKey:
+                type: array
+                items:
+                  type: integer
+              OldValue:
+                type: array
+                items:
+                  type: integer
+              IsOld0:
+                type: boolean
+              Key:
+                type: array
+                items:
+                  type: integer
+              Value:
+                type: array
+                items:
+                  type: integer
+              Fnc:
+                type: integer
+          required:
+            - Root
+            - Siblings
+            - OldKey
+            - OldValue
+            - IsOld0
+            - Key
+            - Value
+            - Fnc
+          additionalProperties: false
+          example: {"Root":[0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"Siblings":[0,1,2],"OldKey":[0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"OldValue":[0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"IsOld0":true,"Key":[0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"Value":[0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],"Fnc":0}
         balance:
           $ref: '#/components/schemas/BigInt'
         instantWithdrawn:
-          allOf:
-            - $ref: '#/components/schemas/EthBlockNum'
-            - description: Block in which the exit balance was instantly withdrawn. Null indicates that an instant withdrawn hasn't been performed.
-            - example: 74747363
+          type: integer
+          description: Block in which the exit balance was instantly withdrawn. Null indicates that an instant withdrawn hasn't been performed.
+          minimum: 0
+          maximum: 1.84467440737096e+19
+          example: 74747363
+          nullable: true
         delayedWithdrawRequest:
-          allOf:
-            - $ref: '#/components/schemas/EthBlockNum'
-            - description: Block in which the exit balance was requested to delay withdraw. Null indicates that a delay withdraw hasn't been performed.
-            - example: null
+          type: integer
+          description: Block in which the exit balance was requested to delay withdraw. Null indicates that a delay withdraw hasn't been performed.
+          minimum: 0
+          maximum: 1.84467440737096e+19
+          example: null
+          nullable: true
         delayedWithdrawn:
-          allOf:
-            - $ref: '#/components/schemas/EthBlockNum'
-            - description: Block in which the exit balance was delayed withdrawn after a delay withdraw request. Null indicates that a delay withdraw hasn't been performed.
-            - example: null
+          type: integer
+          description: Block in which the exit balance was delayed withdrawn after a delay withdraw request. Null indicates that a delay withdraw hasn't been performed.
+          minimum: 0
+          maximum: 1.84467440737096e+19
+          example: null
+          nullable: true
         token:
           $ref: '#/components/schemas/Token'
+      required:
+          - batchNum
+          - accountIndex
+          - itemId
+          - merkleProof
+          - balance
+          - instantWithdrawn
+          - delayedWithdrawRequest
+          - delayedWithdrawn
+          - token
+      additionalProperties: false
     Exits:
       type: object
       properties:
@@ -1975,7 +2065,11 @@ components:
           items: 
             $ref: '#/components/schemas/Exit'
         pagination:
-          $ref: '#/components/schemas/PaginationInfo'    
+          $ref: '#/components/schemas/PaginationInfo'   
+      required:
+          - exits
+          - pagination
+      additionalProperties: false 
     Account:
       type: object
       description: State tree leaf. It contains balance and nonce of an account.
@@ -2217,10 +2311,14 @@ components:
           type: integer
           description: Amount of items that the endpoint can return given the filters and the current state of the database.
           example: 2048
-        lastReturnedItem:
+        firstItem:
+          type: integer
+          description: The smallest itemId that the endpoint will return with the given filters.
+          example: 50
+        lastItem:
           type: integer
-          description: Index of the last returned item. Useful to query next items.
-          example: 439
+          description: The greatest itemId that the endpoint will return with the given filters.
+          example: 2130
     Config:
       type: object
       description: Configuration parameters of the different smart contracts that power the Hermez network.

common/tx.go

@@ -3,8 +3,10 @@ package common
 import (
 	"database/sql/driver"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"math/big"
+	"strings"
 
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/iden3/go-iden3-crypto/babyjub"
@@ -56,6 +58,21 @@ func (txid TxID) String() string {
 	return "0x" + hex.EncodeToString(txid[:])
 }
 
+// NewTxIDFromString returns a string hexadecimal representation of the TxID
+func NewTxIDFromString(idStr string) (TxID, error) {
+	txid := TxID{}
+	idStr = strings.TrimPrefix(idStr, "0x")
+	decoded, err := hex.DecodeString(idStr)
+	if err != nil {
+		return TxID{}, err
+	}
+	if len(decoded) != TxIDLen {
+		return txid, errors.New("Invalid idStr")
+	}
+	copy(txid[:], decoded)
+	return txid, nil
+}
+
 // TxType is a string that represents the type of a Hermez network transaction
 type TxType string
 

db/historydb/historydb.go

@@ -18,6 +18,13 @@ import (
 	"github.com/russross/meddler"
 )
 
+const (
+	// OrderAsc indicates ascending order when using pagination
+	OrderAsc = "ASC"
+	// OrderDesc indicates descending order when using pagination
+	OrderDesc = "DESC"
+)
+
 // TODO(Edu): Document here how HistoryDB is kept consistent
 
 // HistoryDB persist the historic of the rollup
@@ -445,25 +452,47 @@ func (hdb *HistoryDB) addTxs(d meddler.DB, txs []txWrite) error {
 // 	return db.SlicePtrsToSlice(txs).([]common.Tx), err
 // }
 
+// GetHistoryTx returns a tx from the DB given a TxID
+func (hdb *HistoryDB) GetHistoryTx(txID common.TxID) (*HistoryTx, error) {
+	tx := &HistoryTx{}
+	err := meddler.QueryRow(
+		hdb.db, tx, `SELECT tx.item_id, tx.is_l1, tx.id, tx.type, tx.position, 
+		tx.from_idx, tx.to_idx, tx.amount, tx.token_id, tx.amount_usd, 
+		tx.batch_num, tx.eth_block_num, tx.to_forge_l1_txs_num, tx.user_origin, 
+		tx.from_eth_addr, tx.from_bjj, tx.load_amount, 
+		tx.load_amount_usd, tx.fee, tx.fee_usd, tx.nonce,
+		token.token_id, token.eth_block_num AS token_block,
+		token.eth_addr, token.name, token.symbol, token.decimals, token.usd,
+		token.usd_update, block.timestamp
+		FROM tx INNER JOIN token ON tx.token_id = token.token_id 
+		INNER JOIN block ON tx.eth_block_num = block.eth_block_num 
+		WHERE tx.id = $1;`, txID,
+	)
+	return tx, err
+}
+
 // GetHistoryTxs returns a list of txs from the DB using the HistoryTx struct
+// and pagination info
 func (hdb *HistoryDB) GetHistoryTxs(
 	ethAddr *ethCommon.Address, bjj *babyjub.PublicKey,
-	tokenID, idx, batchNum *uint, txType *common.TxType,
-	offset, limit *uint, last bool,
-) ([]HistoryTx, int, error) {
+	tokenID *common.TokenID, idx *common.Idx, batchNum *uint, txType *common.TxType,
+	fromItem, limit *uint, order string,
+) ([]HistoryTx, *db.Pagination, error) {
 	if ethAddr != nil && bjj != nil {
-		return nil, 0, errors.New("ethAddr and bjj are incompatible")
+		return nil, nil, errors.New("ethAddr and bjj are incompatible")
 	}
 	var query string
 	var args []interface{}
-	queryStr := `SELECT tx.is_l1, tx.id, tx.type, tx.position, tx.from_idx, tx.to_idx, 
-	tx.amount, tx.token_id, tx.batch_num, tx.eth_block_num, tx.to_forge_l1_txs_num, 
-	tx.user_origin, tx.from_eth_addr, tx.from_bjj, tx.load_amount, tx.fee, tx.nonce,
+	queryStr := `SELECT tx.item_id, tx.is_l1, tx.id, tx.type, tx.position, 
+	tx.from_idx, tx.to_idx, tx.amount, tx.token_id, tx.amount_usd, 
+	tx.batch_num, tx.eth_block_num, tx.to_forge_l1_txs_num, tx.user_origin, 
+	tx.from_eth_addr, tx.from_bjj, tx.load_amount, 
+	tx.load_amount_usd, tx.fee, tx.fee_usd, tx.nonce,
 	token.token_id, token.eth_block_num AS token_block,
 	token.eth_addr, token.name, token.symbol, token.decimals, token.usd,
-	token.usd_update, block.timestamp, count(*) OVER() AS total_items 
-	FROM tx 
-	INNER JOIN token ON tx.token_id = token.token_id 
+	token.usd_update, block.timestamp, count(*) OVER() AS total_items, 
+	MIN(tx.item_id)  OVER() AS first_item, MAX(tx.item_id) OVER() AS last_item 
+	FROM tx INNER JOIN token ON tx.token_id = token.token_id 
 	INNER JOIN block ON tx.eth_block_num = block.eth_block_num `
 	// Apply filters
 	nextIsAnd := false
@@ -523,33 +552,164 @@ func (hdb *HistoryDB) GetHistoryTxs(
 		}
 		queryStr += "tx.type = ? "
 		args = append(args, txType)
-		// nextIsAnd = true
+		nextIsAnd = true
+	}
+	if fromItem != nil {
+		if nextIsAnd {
+			queryStr += "AND "
+		} else {
+			queryStr += "WHERE "
+		}
+		if order == OrderAsc {
+			queryStr += "tx.item_id >= ? "
+		} else {
+			queryStr += "tx.item_id <= ? "
+		}
+		args = append(args, fromItem)
+		nextIsAnd = true
 	}
+	if nextIsAnd {
+		queryStr += "AND "
+	} else {
+		queryStr += "WHERE "
+	}
+	queryStr += "tx.batch_num IS NOT NULL "
+
 	// pagination
-	if last {
-		queryStr += "ORDER BY (batch_num, position) DESC NULLS FIRST "
+	queryStr += "ORDER BY tx.item_id "
+	if order == OrderAsc {
+		queryStr += " ASC "
 	} else {
-		queryStr += "ORDER BY (batch_num, position) ASC NULLS LAST "
-		queryStr += fmt.Sprintf("OFFSET %d ", *offset)
+		queryStr += " DESC "
 	}
 	queryStr += fmt.Sprintf("LIMIT %d;", *limit)
 	query = hdb.db.Rebind(queryStr)
-	// log.Debug(query)
+	log.Debug(query)
 	txsPtrs := []*HistoryTx{}
 	if err := meddler.QueryAll(hdb.db, &txsPtrs, query, args...); err != nil {
-		return nil, 0, err
+		return nil, nil, err
 	}
 	txs := db.SlicePtrsToSlice(txsPtrs).([]HistoryTx)
 	if len(txs) == 0 {
-		return nil, 0, sql.ErrNoRows
-	} else if last {
-		tmp := []HistoryTx{}
-		for i := len(txs) - 1; i >= 0; i-- {
-			tmp = append(tmp, txs[i])
+		return nil, nil, sql.ErrNoRows
+	}
+	return txs, &db.Pagination{
+		TotalItems: txs[0].TotalItems,
+		FirstItem:  txs[0].FirstItem,
+		LastItem:   txs[0].LastItem,
+	}, nil
+}
+
+// GetExit returns a exit from the DB
+func (hdb *HistoryDB) GetExit(batchNum *uint, idx *common.Idx) (*HistoryExit, error) {
+	exit := &HistoryExit{}
+	err := meddler.QueryRow(
+		hdb.db, exit, `SELECT exit_tree.*, token.token_id, token.eth_block_num AS token_block,
+		token.eth_addr, token.name, token.symbol, token.decimals, token.usd, token.usd_update
+		FROM exit_tree INNER JOIN account ON exit_tree.account_idx = account.idx 
+		INNER JOIN token ON account.token_id = token.token_id 
+		WHERE exit_tree.batch_num = $1 AND exit_tree.account_idx = $2;`, batchNum, idx,
+	)
+	return exit, err
+}
+
+// GetExits returns a list of exits from the DB and pagination info
+func (hdb *HistoryDB) GetExits(
+	ethAddr *ethCommon.Address, bjj *babyjub.PublicKey,
+	tokenID *common.TokenID, idx *common.Idx, batchNum *uint,
+	fromItem, limit *uint, order string,
+) ([]HistoryExit, *db.Pagination, error) {
+	if ethAddr != nil && bjj != nil {
+		return nil, nil, errors.New("ethAddr and bjj are incompatible")
+	}
+	var query string
+	var args []interface{}
+	queryStr := `SELECT exit_tree.*, token.token_id, token.eth_block_num AS token_block,
+	token.eth_addr, token.name, token.symbol, token.decimals, token.usd,
+	token.usd_update, COUNT(*) OVER() AS total_items, MIN(exit_tree.item_id) OVER() AS first_item, MAX(exit_tree.item_id) OVER() AS last_item
+	FROM exit_tree INNER JOIN account ON exit_tree.account_idx = account.idx 
+	INNER JOIN token ON account.token_id = token.token_id `
+	// Apply filters
+	nextIsAnd := false
+	// ethAddr filter
+	if ethAddr != nil {
+		queryStr += "WHERE account.eth_addr = ? "
+		nextIsAnd = true
+		args = append(args, ethAddr)
+	} else if bjj != nil { // bjj filter
+		queryStr += "WHERE account.bjj = ? "
+		nextIsAnd = true
+		args = append(args, bjj)
+	}
+	// tokenID filter
+	if tokenID != nil {
+		if nextIsAnd {
+			queryStr += "AND "
+		} else {
+			queryStr += "WHERE "
+		}
+		queryStr += "account.token_id = ? "
+		args = append(args, tokenID)
+		nextIsAnd = true
+	}
+	// idx filter
+	if idx != nil {
+		if nextIsAnd {
+			queryStr += "AND "
+		} else {
+			queryStr += "WHERE "
+		}
+		queryStr += "exit_tree.account_idx = ? "
+		args = append(args, idx)
+		nextIsAnd = true
+	}
+	// batchNum filter
+	if batchNum != nil {
+		if nextIsAnd {
+			queryStr += "AND "
+		} else {
+			queryStr += "WHERE "
+		}
+		queryStr += "exit_tree.batch_num = ? "
+		args = append(args, batchNum)
+		nextIsAnd = true
+	}
+	if fromItem != nil {
+		if nextIsAnd {
+			queryStr += "AND "
+		} else {
+			queryStr += "WHERE "
 		}
-		txs = tmp
+		if order == OrderAsc {
+			queryStr += "exit_tree.item_id >= ? "
+		} else {
+			queryStr += "exit_tree.item_id <= ? "
+		}
+		args = append(args, fromItem)
+		// nextIsAnd = true
+	}
+	// pagination
+	queryStr += "ORDER BY exit_tree.item_id "
+	if order == OrderAsc {
+		queryStr += " ASC "
+	} else {
+		queryStr += " DESC "
+	}
+	queryStr += fmt.Sprintf("LIMIT %d;", *limit)
+	query = hdb.db.Rebind(queryStr)
+	// log.Debug(query)
+	exits := []*HistoryExit{}
+	if err := meddler.QueryAll(hdb.db, &exits, query, args...); err != nil {
+		return nil, nil, err
+	}
+	if len(exits) == 0 {
+		return nil, nil, sql.ErrNoRows
 	}
-	return txs, txs[0].TotalItems, nil
+	return db.SlicePtrsToSlice(exits).([]HistoryExit), &db.Pagination{
+		TotalItems: exits[0].TotalItems,
+		FirstItem:  exits[0].FirstItem,
+		LastItem:   exits[0].LastItem,
+	}, nil
 }
 
 // // GetTx returns a tx from the DB

db/historydb/historydb_test.go

@@ -213,6 +213,7 @@ func TestTxs(t *testing.T) {
 
 	/*
 		Uncomment once the transaction generation is fixed
+		!! test that batches that forge user L1s !!
 		!! Missing tests to check that historic USD is not set if USDUpdate is too old (24h) !!
 
 		// Generate fake L1 txs
@@ -333,9 +334,14 @@ func TestExitTree(t *testing.T) {
 	blocks := setTestBlocks(0, 10)
 	batches := test.GenBatches(nBatches, blocks)
 	err := historyDB.AddBatches(batches)
+	const nTokens = 50
+	tokens := test.GenTokens(nTokens, blocks)
+	assert.NoError(t, historyDB.AddTokens(tokens))
 	assert.NoError(t, err)
-
-	exitTree := test.GenExitTree(nBatches)
+	const nAccounts = 3
+	accs := test.GenAccounts(nAccounts, 0, tokens, nil, nil, batches)
+	assert.NoError(t, historyDB.AddAccounts(accs))
+	exitTree := test.GenExitTree(nBatches, batches, accs)
 	err = historyDB.AddExitTree(exitTree)
 	assert.NoError(t, err)
 }

db/historydb/views.go

@@ -7,6 +7,7 @@ import (
 	ethCommon "github.com/ethereum/go-ethereum/common"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/iden3/go-iden3-crypto/babyjub"
+	"github.com/iden3/go-merkletree"
 )
 
 // HistoryTx is a representation of a generic Tx with additional information
@@ -15,6 +16,7 @@ type HistoryTx struct {
 	// Generic
 	IsL1        bool             `meddler:"is_l1"`
 	TxID        common.TxID      `meddler:"id"`
+	ItemID      int              `meddler:"item_id"`
 	Type        common.TxType    `meddler:"type"`
 	Position    int              `meddler:"position"`
 	FromIdx     *common.Idx      `meddler:"from_idx"`
@@ -38,6 +40,8 @@ type HistoryTx struct {
 	// API extras
 	Timestamp        time.Time         `meddler:"timestamp,utctime"`
 	TotalItems       int               `meddler:"total_items"`
+	FirstItem        int               `meddler:"first_item"`
+	LastItem         int               `meddler:"last_item"`
 	TokenID          common.TokenID    `meddler:"token_id"`
 	TokenEthBlockNum int64             `meddler:"token_block"`
 	TokenEthAddr     ethCommon.Address `meddler:"eth_addr"`
@@ -86,3 +90,27 @@ type TokenRead struct {
 	USD         *float64          `json:"USD" meddler:"usd"`
 	USDUpdate   *time.Time        `json:"fiatUpdate" meddler:"usd_update,utctime"`
 }
+
+// HistoryExit is a representation of a exit with additional information
+// required by the API, and extracted by joining token table
+type HistoryExit struct {
+	ItemID                 int                             `meddler:"item_id"`
+	BatchNum               common.BatchNum                 `meddler:"batch_num"`
+	AccountIdx             common.Idx                      `meddler:"account_idx"`
+	MerkleProof            *merkletree.CircomVerifierProof `meddler:"merkle_proof,json"`
+	Balance                *big.Int                        `meddler:"balance,bigint"`
+	InstantWithdrawn       *int64                          `meddler:"instant_withdrawn"`
+	DelayedWithdrawRequest *int64                          `meddler:"delayed_withdraw_request"`
+	DelayedWithdrawn       *int64                          `meddler:"delayed_withdrawn"`
+	TotalItems             int                             `meddler:"total_items"`
+	FirstItem              int                             `meddler:"first_item"`
+	LastItem               int                             `meddler:"last_item"`
+	TokenID                common.TokenID                  `meddler:"token_id"`
+	TokenEthBlockNum       int64                           `meddler:"token_block"`
+	TokenEthAddr           ethCommon.Address               `meddler:"eth_addr"`
+	TokenName              string                          `meddler:"name"`
+	TokenSymbol            string                          `meddler:"symbol"`
+	TokenDecimals          uint64                          `meddler:"decimals"`
+	TokenUSD               *float64                        `meddler:"usd"`
+	TokenUSDUpdate         *time.Time                      `meddler:"usd_update"`
+}

db/migrations/0001.sql

@@ -28,17 +28,6 @@ CREATE TABLE batch (
     total_fees_usd NUMERIC
 );
 
-CREATE TABLE exit_tree (
-    batch_num BIGINT REFERENCES batch (batch_num) ON DELETE CASCADE,
-    account_idx BIGINT,
-    merkle_proof BYTEA NOT NULL,
-    balance BYTEA NOT NULL,
-    instant_withdrawn BIGINT REFERENCES batch (batch_num) ON DELETE SET NULL,
-    delayed_withdraw_request BIGINT REFERENCES batch (batch_num) ON DELETE SET NULL,
-    delayed_withdrawn BIGINT REFERENCES batch (batch_num) ON DELETE SET NULL,
-    PRIMARY KEY (batch_num, account_idx)
-);
-
 CREATE TABLE bid (
     slot_num BIGINT NOT NULL,
     bid_value BYTEA NOT NULL,
@@ -58,6 +47,25 @@ CREATE TABLE token (
     usd_update TIMESTAMP WITHOUT TIME ZONE
 );
 
+CREATE TABLE account (
+    idx BIGINT PRIMARY KEY,
+    token_id INT NOT NULL REFERENCES token (token_id) ON DELETE CASCADE,
+    batch_num BIGINT NOT NULL REFERENCES batch (batch_num) ON DELETE CASCADE,
+    bjj BYTEA NOT NULL,
+    eth_addr BYTEA NOT NULL
+);
+
+CREATE TABLE exit_tree (
+    item_id SERIAL PRIMARY KEY,
+    batch_num BIGINT REFERENCES batch (batch_num) ON DELETE CASCADE,
+    account_idx BIGINT REFERENCES account (idx) ON DELETE CASCADE,
+    merkle_proof BYTEA NOT NULL,
+    balance BYTEA NOT NULL,
+    instant_withdrawn BIGINT REFERENCES batch (batch_num) ON DELETE SET NULL,
+    delayed_withdraw_request BIGINT REFERENCES batch (batch_num) ON DELETE SET NULL,
+    delayed_withdrawn BIGINT REFERENCES batch (batch_num) ON DELETE SET NULL
+);
+
 -- +migrate StatementBegin
 CREATE FUNCTION set_token_usd_update() 
     RETURNS TRIGGER 
@@ -75,10 +83,13 @@ LANGUAGE plpgsql;
 CREATE TRIGGER trigger_token_usd_update BEFORE UPDATE OR INSERT ON token
 FOR EACH ROW EXECUTE PROCEDURE set_token_usd_update();
 
+CREATE SEQUENCE tx_item_id;
+
 CREATE TABLE tx (
     -- Generic TX
+    item_id INTEGER PRIMARY KEY DEFAULT nextval('tx_item_id'),
     is_l1 BOOLEAN NOT NULL,
-    id BYTEA PRIMARY KEY,
+    id BYTEA,
     type VARCHAR(40) NOT NULL,
     position INT NOT NULL,
     from_idx BIGINT,
@@ -103,8 +114,6 @@ CREATE TABLE tx (
     nonce BIGINT
 );
 
-CREATE INDEX tx_order ON tx (batch_num, position);
-
 -- +migrate StatementBegin
 CREATE FUNCTION fee_percentage(NUMERIC)
     RETURNS NUMERIC 
@@ -412,9 +421,10 @@ BEGIN
         usd / POWER(10, decimals), usd_update, timestamp FROM token INNER JOIN block on token.eth_block_num = block.eth_block_num WHERE token_id = NEW.token_id;
     IF _tx_timestamp - interval '24 hours' < _usd_update AND _tx_timestamp + interval '24 hours' > _usd_update THEN
         NEW."amount_usd" = (SELECT _value * NEW.amount_f);
-        NEW."load_amount_usd" = (SELECT _value * NEW.load_amount_f);
         IF NOT NEW.is_l1 THEN
             NEW."fee_usd" = (SELECT NEW."amount_usd" * fee_percentage(NEW.fee::NUMERIC));
+        ELSE 
+            NEW."load_amount_usd" = (SELECT _value * NEW.load_amount_f);
         END IF;
     END IF;
     RETURN NEW;
@@ -433,8 +443,13 @@ $BODY$
 BEGIN
     IF NEW.forge_l1_txs_num IS NOT NULL THEN
         UPDATE tx 
-        SET batch_num = NEW.batch_num
-        WHERE user_origin AND NEW.forge_l1_txs_num = to_forge_l1_txs_num;
+        SET item_id = nextval('tx_item_id'), batch_num = NEW.batch_num 
+        WHERE id IN (
+            SELECT id FROM tx 
+            WHERE user_origin AND NEW.forge_l1_txs_num = to_forge_l1_txs_num 
+            ORDER BY position
+            FOR UPDATE
+        ); 
     END IF;
     RETURN NEW;
 END;
@@ -444,14 +459,6 @@ LANGUAGE plpgsql;
 CREATE TRIGGER trigger_forge_l1_txs AFTER INSERT ON batch
 FOR EACH ROW EXECUTE PROCEDURE forge_l1_user_txs();
 
-CREATE TABLE account (
-    idx BIGINT PRIMARY KEY,
-    token_id INT NOT NULL REFERENCES token (token_id) ON DELETE CASCADE,
-    batch_num BIGINT NOT NULL REFERENCES batch (batch_num) ON DELETE CASCADE,
-    bjj BYTEA NOT NULL,
-    eth_addr BYTEA NOT NULL
-);
-
 CREATE TABLE rollup_vars (
     eth_block_num BIGINT PRIMARY KEY REFERENCES block (eth_block_num) ON DELETE CASCADE,
     forge_l1_timeout BYTEA NOT NULL,

db/utils.go

@@ -177,3 +177,18 @@ func SlicePtrsToSlice(slice interface{}) interface{} {
 	}
 	return res.Interface()
 }
+
+// Pagination give information on the items of a query
+type Pagination struct {
+	TotalItems        int `json:"totalItems"`
+	FirstItem         int `json:"firstItem"`
+	LastItem          int `json:"lastItem"`
+	FirstReturnedItem int `json:"-"`
+	LastReturnedItem  int `json:"-"`
+}
+
+// Paginationer is an interface that allows getting pagination info on any struct
+type Paginationer interface {
+	GetPagination() *Pagination
+	Len() int
+}

test/historydb.go

@@ -68,7 +68,7 @@ func GenBatches(nBatches int, blocks []common.Block) []common.Batch {
 		}
 		if i%2 == 0 {
 			toForge := new(int64)
-			*toForge = int64(i)
+			*toForge = int64(i + 1)
 			batch.ForgeL1TxsNum = toForge
 		}
 		batches = append(batches, batch)
@@ -142,7 +142,9 @@ func GenL1Txs(
 			panic(err)
 		}
 		tx = *nTx
-		if batches[i%len(batches)].ForgeL1TxsNum != nil {
+		if !tx.UserOrigin {
+			tx.BatchNum = &batches[i%len(batches)].BatchNum
+		} else if batches[i%len(batches)].ForgeL1TxsNum != nil {
 			// Add already forged txs
 			tx.BatchNum = &batches[i%len(batches)].BatchNum
 			setFromToAndAppend(fromIdx, tx, i, nUserTxs, userAddr, accounts, &userTxs, &othersTxs)
@@ -332,15 +334,15 @@ func GenBids(nBids int, blocks []common.Block, coords []common.Coordinator) []co
 
 // GenExitTree generates an exitTree (as an array of Exits)
 //nolint:gomnd
-func GenExitTree(n int) []common.ExitInfo {
+func GenExitTree(n int, batches []common.Batch, accounts []common.Account) []common.ExitInfo {
 	exitTree := make([]common.ExitInfo, n)
 	for i := 0; i < n; i++ {
 		exitTree[i] = common.ExitInfo{
-			BatchNum:               common.BatchNum(i + 1),
+			BatchNum:               batches[i%len(batches)].BatchNum,
 			InstantWithdrawn:       nil,
 			DelayedWithdrawRequest: nil,
 			DelayedWithdrawn:       nil,
-			AccountIdx:             common.Idx(i * 10),
+			AccountIdx:             accounts[i%len(accounts)].Idx,
 			MerkleProof: &merkletree.CircomVerifierProof{
 				Root: &merkletree.Hash{byte(i), byte(i + 1)},
 				Siblings: []*big.Int{
@@ -356,6 +358,20 @@ func GenExitTree(n int) []common.ExitInfo {
 			},
 			Balance: big.NewInt(int64(i) * 1000),
 		}
+		if i%2 == 0 {
+			instant := new(int64)
+			*instant = int64(batches[(i+1)%len(batches)].BatchNum)
+			exitTree[i].InstantWithdrawn = instant
+		} else if i%3 == 0 {
+			delayedReq := new(int64)
+			*delayedReq = int64(batches[(i+1)%len(batches)].BatchNum)
+			exitTree[i].DelayedWithdrawRequest = delayedReq
+			if i%9 == 0 {
+				delayed := new(int64)
+				*delayed = int64(batches[(i+2)%len(batches)].BatchNum)
+				exitTree[i].DelayedWithdrawn = delayed
+			}
+		}
 	}
 	return exitTree
 }