package main

import (
	"github.com/ethereum/ethutil-go"
	"github.com/obscuren/sha3"
	"hash"
	"math/big"
	"math/rand"
	"time"
)

type Dagger struct {
	hash *big.Int
	xn   *big.Int
}

var Found bool

func (dag *Dagger) Find(obj *big.Int, resChan chan int64) {
	r := rand.New(rand.NewSource(time.Now().UnixNano()))

	for i := 0; i < 1000; i++ {
		rnd := r.Int63()

		if dag.Eval(big.NewInt(rnd)).Cmp(obj) < 0 {
			// Post back result on the channel
			resChan <- rnd
			// Notify other threads we've found a valid nonce
			Found = true
		}

		// Break out if found
		if Found {
			break
		}
	}

	resChan <- 0
}

func (dag *Dagger) Search(hash, diff *big.Int) *big.Int {
	// TODO fix multi threading. Somehow it results in the wrong nonce
	amountOfRoutines := 1

	dag.hash = hash

	obj := ethutil.BigPow(2, 256)
	obj = obj.Div(obj, diff)

	Found = false
	resChan := make(chan int64, 3)
	var res int64

	for k := 0; k < amountOfRoutines; k++ {
		go dag.Find(obj, resChan)
	}

	// Wait for each go routine to finish
	for k := 0; k < amountOfRoutines; k++ {
		// Get the result from the channel. 0 = quit
		if r := <-resChan; r != 0 {
			res = r
		}
	}

	return big.NewInt(res)
}

func DaggerVerify(hash, diff, nonce *big.Int) bool {
	dagger := &Dagger{}
	dagger.hash = hash

	obj := ethutil.BigPow(2, 256)
	obj = obj.Div(obj, diff)

	return dagger.Eval(nonce).Cmp(obj) < 0
}

func (dag *Dagger) Node(L uint64, i uint64) *big.Int {
	if L == i {
		return dag.hash
	}

	var m *big.Int
	if L == 9 {
		m = big.NewInt(16)
	} else {
		m = big.NewInt(3)
	}

	sha := sha3.NewKeccak256()
	sha.Reset()
	d := sha3.NewKeccak256()
	b := new(big.Int)
	ret := new(big.Int)

	for k := 0; k < int(m.Uint64()); k++ {
		d.Reset()
		d.Write(dag.hash.Bytes())
		d.Write(dag.xn.Bytes())
		d.Write(big.NewInt(int64(L)).Bytes())
		d.Write(big.NewInt(int64(i)).Bytes())
		d.Write(big.NewInt(int64(k)).Bytes())

		b.SetBytes(Sum(d))
		pk := b.Uint64() & ((1 << ((L - 1) * 3)) - 1)
		sha.Write(dag.Node(L-1, pk).Bytes())
	}

	ret.SetBytes(Sum(sha))

	return ret
}

func Sum(sha hash.Hash) []byte {
	in := make([]byte, 32)
	return sha.Sum(in)
}

func (dag *Dagger) Eval(N *big.Int) *big.Int {
	pow := ethutil.BigPow(2, 26)
	dag.xn = N.Div(N, pow)

	sha := sha3.NewKeccak256()
	sha.Reset()
	ret := new(big.Int)

	for k := 0; k < 4; k++ {
		d := sha3.NewKeccak256()
		b := new(big.Int)

		d.Reset()
		d.Write(dag.hash.Bytes())
		d.Write(dag.xn.Bytes())
		d.Write(N.Bytes())
		d.Write(big.NewInt(int64(k)).Bytes())

		b.SetBytes(Sum(d))
		pk := (b.Uint64() & 0x1ffffff)

		sha.Write(dag.Node(9, pk).Bytes())
	}

	return ret.SetBytes(Sum(sha))
}