Add cmd to contribute to the ceremony (full flow)

It works, used it to contribute to the Ethereum KZG test Ceremony.

README.md

@@ -18,3 +18,17 @@ Why in Go? Ideally would have done this code using Rust & arkworks, but the offi
 Documents used for this implementation:
 - [KZG10-Ceremony-audit-report.pdf, section *3.1 Overview of PoT ceremonies*](https://github.com/ethereum/kzg-ceremony/blob/main/KZG10-Ceremony-audit-report.pdf)
 - [*Why and how zkSNARKs work*, by Maksym Petkus](https://arxiv.org/abs/1906.07221v1)
+
+### Usage
+Go into the `cmd` dir, and run:
+```
+> go run cmd.go
+
+eth-kzg-ceremony-alt
+====================
+
+Usage of /tmp/go-build4278582969/b001/exe/cmd:
+  -u, --url string       sequencer url (default "https://kzg-ceremony-sequencer-dev.fly.dev")
+  -r, --rand string      randomness
+  -s, --sleeptime uint   time (seconds) sleeping before trying again to be the next contributor (default 10)
+```

cmd/cmd.go

@@ -0,0 +1,176 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"kzgceremony"
+	"kzgceremony/client"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/fatih/color"
+	flag "github.com/spf13/pflag"
+)
+
+type Config struct {
+	sequencerURL string
+	randomness   string
+	sleepTime    uint64
+}
+
+func main() {
+	fmt.Println("eth-kzg-ceremony-alt")
+	fmt.Printf("====================\n\n")
+
+	red := color.New(color.FgRed)
+	redB := color.New(color.FgRed, color.Bold)
+	cyan := color.New(color.FgCyan)
+	cyanB := color.New(color.FgCyan, color.Bold)
+	green := color.New(color.FgHiGreen)
+	greenB := color.New(color.FgHiGreen, color.Bold)
+
+	config := Config{}
+	flag.StringVarP(&config.sequencerURL, "url", "u",
+		"https://kzg-ceremony-sequencer-dev.fly.dev", "sequencer url")
+	flag.StringVarP(&config.randomness, "rand", "r",
+		"", "randomness")
+	flag.Uint64VarP(&config.sleepTime, "sleeptime", "s",
+		10, "time (seconds) sleeping before trying again to be the next contributor")
+
+	flag.CommandLine.SortFlags = false
+	flag.Parse()
+
+	c := client.NewClient(config.sequencerURL)
+
+	// get status
+	msgStatus, err := c.GetCurrentStatus()
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	fmt.Println(msgStatus)
+
+	if config.randomness == "" {
+		cyanB.Println("To contribute to the ceremony, please set your randomness. Use -h to show the available flags.")
+		os.Exit(0)
+	}
+
+	if len([]byte(config.randomness)) < kzgceremony.MinRandomnessLen {
+		redB.Printf("Randomness must be longer than %d, current length: %d\n",
+			kzgceremony.MinRandomnessLen, len([]byte(config.randomness)))
+		os.Exit(1)
+	}
+
+	// Auth
+	msgReqLink, err := c.GetRequestLink()
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+
+	green.Printf("Please go to\n%s\n and authenticate with Github.\n", msgReqLink.GithubAuthURL)
+	fmt.Println("(currently only Github auth is supported)")
+
+	greenB.Printf("Paste here the RawData from the auth answer:\n")
+	s, err := readInput()
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	var authMsg client.MsgAuthCallback
+	if err = json.Unmarshal([]byte(s), &authMsg); err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	fmt.Print("Parsed auth msg: ")
+	cyan.Printf("%#v\n", authMsg)
+
+	// TODO this will be only triggered by a flag
+	// msg, err := c.PostAbortContribution(authMsg.SessionID)
+	// if err != nil {
+	//         red.Println(err)
+	//	   os.Exit(1)
+	// }
+	// fmt.Println("ABORT", string(msg))
+	// os.Exit(0)
+
+	// Get on queue
+	var prevBatchContribution *kzgceremony.BatchContribution
+	for {
+		fmt.Printf("%s sending try_contribute\n", time.Now().Format("2006-01-02 15:04:05"))
+		var retry bool
+		prevBatchContribution, retry, err = c.PostTryContribute(authMsg.SessionID)
+		if err != nil {
+			red.Println(err)
+		}
+		if !retry {
+			break
+		}
+		fmt.Printf("%s try_contribute unsuccessful, going to sleep %d seconds\n",
+			time.Now().Format("2006-01-02 15:04:05"), config.sleepTime)
+		time.Sleep(time.Duration(config.sleepTime) * time.Second)
+	}
+
+	// get latest state
+	// currentState, err := c.GetCurrentState()
+	// if err != nil {
+	//         red.Println(err)
+	//	   os.Exit(1)
+	// }
+
+	fmt.Println("starting to compute new contribution")
+	newBatchContribution, err := prevBatchContribution.Contribute([]byte(config.randomness))
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	// store contribution
+	fmt.Println("storing contribution.json")
+	b, err := json.Marshal(newBatchContribution)
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	err = ioutil.WriteFile("contribution.json", b, 0600)
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+
+	// send contribution
+	fmt.Println("sending contribution")
+	receipt, err := c.PostContribute(authMsg.SessionID, newBatchContribution)
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	fmt.Println("Receipt:")
+	green.Println(receipt)
+
+	// store receipt
+	fmt.Println("storing contribution_receipt.json")
+	b, err = json.Marshal(receipt)
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+	err = ioutil.WriteFile("contribution_receipt.json", b, 0600)
+	if err != nil {
+		red.Println(err)
+		os.Exit(1)
+	}
+}
+
+func readInput() (string, error) {
+	reader := bufio.NewReader(os.Stdin)
+	input, err := reader.ReadString('\n')
+	if err != nil {
+		return "", err
+	}
+	// remove the delimeter from the string
+	input = strings.TrimSuffix(input, "\n")
+	return input, nil
+}