package gocircomprover

import (
	"encoding/hex"
	"fmt"
	"math/big"
	"strings"

	bn256 "github.com/ethereum/go-ethereum/crypto/bn256/cloudflare"
)

func addZPadding(b []byte) []byte {
	var z [32]byte
	var r []byte
	r = append(r, z[len(b):]...) // add padding on the left
	r = append(r, b...)
	return r[:32]
}

func stringToBytes(s string) ([]byte, error) {
	if s == "1" {
		s = "0"
	}
	bi, ok := new(big.Int).SetString(s, 10)
	if !ok {
		return nil, fmt.Errorf("error parsing bigint stringToBytes")
	}
	b := bi.Bytes()
	if len(b) != 32 {
		b = addZPadding(b)
	}
	return b, nil

}

func arrayStringToG1(h [][]string) ([]*bn256.G1, error) {
	var o []*bn256.G1
	for i := 0; i < len(h); i++ {
		hi, err := stringToG1(h[i])
		if err != nil {
			return o, err
		}
		o = append(o, hi)
	}
	return o, nil
}

func arrayStringToG2(h [][][]string) ([]*bn256.G2, error) {
	var o []*bn256.G2
	for i := 0; i < len(h); i++ {
		hi, err := stringToG2(h[i])
		if err != nil {
			return o, err
		}
		o = append(o, hi)
	}
	return o, nil
}

func stringToG1(h []string) (*bn256.G1, error) {
	if len(h) <= 2 {
		return nil, fmt.Errorf("not enought data for stringToG1")
	}
	h = h[:2]
	hexa := false
	if len(h[0]) > 1 {
		if "0x" == h[0][:2] {
			hexa = true
		}
	}
	in := ""

	var b []byte
	var err error
	if hexa {
		for i := range h {
			in += strings.TrimPrefix(h[i], "0x")
		}
		b, err = hex.DecodeString(in)
		if err != nil {
			return nil, err
		}
	} else {
		// TODO TMP
		// TODO use stringToBytes()
		if h[0] == "1" {
			h[0] = "0"
		}
		if h[1] == "1" {
			h[1] = "0"
		}
		bi0, ok := new(big.Int).SetString(h[0], 10)
		if !ok {
			return nil, fmt.Errorf("error parsing stringToG1")
		}
		bi1, ok := new(big.Int).SetString(h[1], 10)
		if !ok {
			return nil, fmt.Errorf("error parsing stringToG1")
		}
		b0 := bi0.Bytes()
		b1 := bi1.Bytes()
		if len(b0) != 32 {
			b0 = addZPadding(b0)
		}
		if len(b1) != 32 {
			b1 = addZPadding(b1)
		}

		b = append(b, b0...)
		b = append(b, b1...)
	}
	p := new(bn256.G1)
	_, err = p.Unmarshal(b)

	return p, err
}

func stringToG2(h [][]string) (*bn256.G2, error) {
	if len(h) <= 2 {
		return nil, fmt.Errorf("not enought data for stringToG2")
	}
	h = h[:2]
	hexa := false
	if len(h[0][0]) > 1 {
		if "0x" == h[0][0][:2] {
			hexa = true
		}
	}
	in := ""
	var b []byte
	var err error
	if hexa {
		for i := 0; i < len(h); i++ {
			for j := 0; j < len(h[i]); j++ {
				in += strings.TrimPrefix(h[i][j], "0x")
			}
		}
		b, err = hex.DecodeString(in)
		if err != nil {
			return nil, err
		}
	} else {
		// TODO TMP
		bH, err := stringToBytes(h[0][1])
		if err != nil {
			return nil, err
		}
		b = append(b, bH...)
		bH, err = stringToBytes(h[0][0])
		if err != nil {
			return nil, err
		}
		b = append(b, bH...)
		bH, err = stringToBytes(h[1][1])
		if err != nil {
			return nil, err
		}
		b = append(b, bH...)
		bH, err = stringToBytes(h[1][0])
		if err != nil {
			return nil, err
		}
		b = append(b, bH...)
	}

	p := new(bn256.G2)
	_, err = p.Unmarshal(b)
	return p, err
}