// Copyright (c) 2013-2017 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package blockdag

import (
	"compress/bzip2"
	"encoding/binary"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/daglabs/btcd/dagconfig"
	"github.com/daglabs/btcd/dagconfig/daghash"
	_ "github.com/daglabs/btcd/database/ffldb"
	"github.com/daglabs/btcd/util"
	"github.com/daglabs/btcd/wire"
)

// loadBlocks reads files containing bitcoin block data (gzipped but otherwise
// in the format bitcoind writes) from disk and returns them as an array of
// util.Block.  This is largely borrowed from the test code in btcdb.
func loadBlocks(filename string) (blocks []*util.Block, err error) {
	filename = filepath.Join("testdata/", filename)

	var network = wire.MainNet
	var dr io.Reader
	var fi io.ReadCloser

	fi, err = os.Open(filename)
	if err != nil {
		return
	}

	if strings.HasSuffix(filename, ".bz2") {
		dr = bzip2.NewReader(fi)
	} else {
		dr = fi
	}
	defer fi.Close()

	var block *util.Block

	err = nil
	for height := 0; err == nil; height++ {
		var rintbuf uint32
		err = binary.Read(dr, binary.LittleEndian, &rintbuf)
		if err == io.EOF {
			// hit end of file at expected offset: no warning
			height--
			err = nil
			break
		}
		if err != nil {
			break
		}
		if rintbuf != uint32(network) {
			break
		}
		err = binary.Read(dr, binary.LittleEndian, &rintbuf)
		blocklen := rintbuf

		rbytes := make([]byte, blocklen)

		// read block
		dr.Read(rbytes)

		block, err = util.NewBlockFromBytes(rbytes)
		if err != nil {
			return
		}
		block.SetHeight(int32(height))
		blocks = append(blocks, block)
	}

	return
}

// loadUTXOSet returns a utxo view loaded from a file.
func loadUTXOSet(filename string) (UTXOSet, error) {
	// The utxostore file format is:
	// <tx hash><output index><serialized utxo len><serialized utxo>
	//
	// The output index and serialized utxo len are little endian uint32s
	// and the serialized utxo uses the format described in dagio.go.

	filename = filepath.Join("testdata", filename)
	fi, err := os.Open(filename)
	if err != nil {
		return nil, err
	}

	// Choose read based on whether the file is compressed or not.
	var r io.Reader
	if strings.HasSuffix(filename, ".bz2") {
		r = bzip2.NewReader(fi)
	} else {
		r = fi
	}
	defer fi.Close()

	utxoSet := NewFullUTXOSet()
	for {
		// Hash of the utxo entry.
		var hash daghash.Hash
		_, err := io.ReadAtLeast(r, hash[:], len(hash[:]))
		if err != nil {
			// Expected EOF at the right offset.
			if err == io.EOF {
				break
			}
			return nil, err
		}

		// Output index of the utxo entry.
		var index uint32
		err = binary.Read(r, binary.LittleEndian, &index)
		if err != nil {
			return nil, err
		}

		// Num of serialized utxo entry bytes.
		var numBytes uint32
		err = binary.Read(r, binary.LittleEndian, &numBytes)
		if err != nil {
			return nil, err
		}

		// Serialized utxo entry.
		serialized := make([]byte, numBytes)
		_, err = io.ReadAtLeast(r, serialized, int(numBytes))
		if err != nil {
			return nil, err
		}

		// Deserialize it and add it to the view.
		entry, err := deserializeUTXOEntry(serialized)
		if err != nil {
			return nil, err
		}
		utxoSet.utxoCollection[wire.OutPoint{Hash: hash, Index: index}] = entry
	}

	return utxoSet, nil
}

// TstSetCoinbaseMaturity makes the ability to set the coinbase maturity
// available when running tests.
func (dag *BlockDAG) TstSetCoinbaseMaturity(maturity uint16) {
	dag.dagParams.CoinbaseMaturity = maturity
}

// newTestDAG returns a DAG that is usable for syntetic tests.  It is
// important to note that this chain has no database associated with it, so
// it is not usable with all functions and the tests must take care when making
// use of it.
func newTestDAG(params *dagconfig.Params) *BlockDAG {
	// Create a genesis block node and block index index populated with it
	// for use when creating the fake chain below.
	node := newBlockNode(&params.GenesisBlock.Header, newSet(), params.K)
	index := newBlockIndex(nil, params)
	index.AddNode(node)

	targetTimespan := int64(params.TargetTimespan / time.Second)
	targetTimePerBlock := int64(params.TargetTimePerBlock / time.Second)
	adjustmentFactor := params.RetargetAdjustmentFactor
	return &BlockDAG{
		dagParams:           params,
		timeSource:          NewMedianTime(),
		minRetargetTimespan: targetTimespan / adjustmentFactor,
		maxRetargetTimespan: targetTimespan * adjustmentFactor,
		blocksPerRetarget:   int32(targetTimespan / targetTimePerBlock),
		index:               index,
		virtual:             newVirtualBlock(setFromSlice(node), params.K),
		genesis:             index.LookupNode(params.GenesisHash),
		warningCaches:       newThresholdCaches(vbNumBits),
		deploymentCaches:    newThresholdCaches(dagconfig.DefinedDeployments),
	}
}

// newTestNode creates a block node connected to the passed parent with the
// provided fields populated and fake values for the other fields.
func newTestNode(parents blockSet, blockVersion int32, bits uint32, timestamp time.Time, phantomK uint32) *blockNode {
	// Make up a header and create a block node from it.
	header := &wire.BlockHeader{
		Version:    blockVersion,
		PrevBlocks: parents.hashes(),
		Bits:       bits,
		Timestamp:  timestamp,
	}
	return newBlockNode(header, parents, phantomK)
}

func addNodeAsChildToParents(node *blockNode) {
	for _, parent := range node.parents {
		parent.children.add(node)
	}
}