lightwalletd/common/common.go

package common

import (
	"bytes"
	"encoding/hex"
	"encoding/json"
	"strconv"
	"strings"

	"github.com/adityapk00/lightwalletd/parser"
	"github.com/adityapk00/lightwalletd/walletrpc"
	"github.com/btcsuite/btcd/rpcclient"
	"github.com/pkg/errors"
)

func GetSaplingInfo(rpcClient *rpcclient.Client) (int, string, string, error) {
	result, rpcErr := rpcClient.RawRequest("getblockchaininfo", make([]json.RawMessage, 0))

	var err error
	var errCode int64

	// For some reason, the error responses are not JSON
	if rpcErr != nil {
		errParts := strings.SplitN(rpcErr.Error(), ":", 2)
		errCode, err = strconv.ParseInt(errParts[0], 10, 32)
		//Check to see if we are requesting a height the zcashd doesn't have yet
		if err == nil && errCode == -8 {
			return -1, "", "", nil
		}
		return -1, "", "", errors.Wrap(rpcErr, "error requesting block")
	}

	var f interface{}
	err = json.Unmarshal(result, &f)
	if err != nil {
		return -1, "", "", errors.Wrap(err, "error reading JSON response")
	}

	chainName := f.(map[string]interface{})["chain"].(string)

	upgradeJSON := f.(map[string]interface{})["upgrades"]
	saplingJSON := upgradeJSON.(map[string]interface{})["76b809bb"] // Sapling ID
	saplingHeight := saplingJSON.(map[string]interface{})["activationheight"].(float64)

	consensus := f.(map[string]interface{})["consensus"]
	branchID := consensus.(map[string]interface{})["nextblock"].(string)

	return int(saplingHeight), chainName, branchID, nil
}

func getBlockFromRPC(rpcClient *rpcclient.Client, height int) (*walletrpc.CompactBlock, error) {
	params := make([]json.RawMessage, 2)
	params[0] = json.RawMessage("\"" + strconv.Itoa(height) + "\"")
	params[1] = json.RawMessage("0")
	result, rpcErr := rpcClient.RawRequest("getblock", params)

	var err error
	var errCode int64

	// For some reason, the error responses are not JSON
	if rpcErr != nil {
		errParts := strings.SplitN(rpcErr.Error(), ":", 2)
		errCode, err = strconv.ParseInt(errParts[0], 10, 32)
		//Check to see if we are requesting a height the zcashd doesn't have yet
		if err == nil && errCode == -8 {
			return nil, nil
		}
		return nil, errors.Wrap(rpcErr, "error requesting block")
	}

	var blockDataHex string
	err = json.Unmarshal(result, &blockDataHex)
	if err != nil {
		return nil, errors.Wrap(err, "error reading JSON response")
	}

	blockData, err := hex.DecodeString(blockDataHex)
	if err != nil {
		return nil, errors.Wrap(err, "error decoding getblock output")
	}

	block := parser.NewBlock()
	rest, err := block.ParseFromSlice(blockData)
	if err != nil {
		return nil, errors.Wrap(err, "error parsing block")
	}
	if len(rest) != 0 {
		return nil, errors.New("received overlong message")
	}

	return block.ToCompact(), nil
}

func GetBlock(rpcClient *rpcclient.Client, cache *BlockCache, height int) (*walletrpc.CompactBlock, error) {
	// First, check the cache to see if we have the block
	block := cache.Get(height)
	if block != nil {
		return block, nil
	}

	block, err := getBlockFromRPC(rpcClient, height)
	if err != nil {
		return nil, err
	}

	// Store the block in the cache, but test for reorg first
	prevBlock := cache.Get(height - 1)

	if prevBlock != nil {
		if !bytes.Equal(prevBlock.Hash, block.PrevHash) {
			// Reorg!
			reorgCount := 0
			cacheBlock := cache.Get(height - reorgCount)

			rpcBlocks := []*walletrpc.CompactBlock{}

			for ; reorgCount <= 100 &&
				cacheBlock != nil &&
				!bytes.Equal(block.PrevHash, cacheBlock.Hash); reorgCount++ {

				block, err = getBlockFromRPC(rpcClient, height-reorgCount-1)
				if err != nil {
					return nil, err
				}

				_ = append(rpcBlocks, block)

				cacheBlock = cache.Get(height - reorgCount - 2)

			}

			if reorgCount == 100 {
				return nil, errors.New("Max reorg depth exceeded")
			}

			// At this point, the block.prevHash == cache.hash
			// Store all blocks starting with 'block'
			for i := len(rpcBlocks) - 1; i >= 0; i-- {
				cache.Add(int(rpcBlocks[i].Height), rpcBlocks[i])
			}
		}
	}

	cache.Add(height, block)

	return block, nil
}

func GetBlockRange(rpcClient *rpcclient.Client, cache *BlockCache,
	blockOut chan<- walletrpc.CompactBlock, errOut chan<- error, start, end int) {

	// Go over [start, end] inclusive
	for i := start; i <= end; i++ {
		block, err := GetBlock(rpcClient, cache, i)
		if err != nil {
			errOut <- err
			return
		}

		blockOut <- *block
	}

	errOut <- nil
}