// Copyright (c) 2013-2014 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package blockchain_test

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

	"github.com/btcsuite/btcd/blockchain"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/wire"
	"github.com/btcsuite/btcutil"
)

// TestReorganization loads a set of test blocks which force a chain
// reorganization to test the block chain handling code.
// The test blocks were originally from a post on the bitcoin talk forums:
// https://bitcointalk.org/index.php?topic=46370.msg577556#msg577556
func TestReorganization(t *testing.T) {
	// Intentionally load the side chain blocks out of order to ensure
	// orphans are handled properly along with chain reorganization.
	testFiles := []string{
		"blk_0_to_4.dat.bz2",
		"blk_4A.dat.bz2",
		"blk_5A.dat.bz2",
		"blk_3A.dat.bz2",
	}

	var blocks []*btcutil.Block
	for _, file := range testFiles {
		blockTmp, err := loadBlocks(file)
		if err != nil {
			t.Errorf("Error loading file: %v\n", err)
		}
		blocks = append(blocks, blockTmp...)
	}

	t.Logf("Number of blocks: %v\n", len(blocks))

	// Create a new database and chain instance to run tests against.
	chain, teardownFunc, err := chainSetup("reorg", &chaincfg.MainNetParams)
	if err != nil {
		t.Errorf("Failed to setup chain instance: %v", err)
		return
	}
	defer teardownFunc()

	// Since we're not dealing with the real block chain set the coinbase
	// maturity to 1.
	chain.TstSetCoinbaseMaturity(1)

	expectedOrphans := map[int]struct{}{5: {}, 6: {}}
	for i := 1; i < len(blocks); i++ {
		_, isOrphan, err := chain.ProcessBlock(blocks[i], blockchain.BFNone)
		if err != nil {
			t.Errorf("ProcessBlock fail on block %v: %v\n", i, err)
			return
		}
		if _, ok := expectedOrphans[i]; !ok && isOrphan {
			t.Errorf("ProcessBlock incorrectly returned block %v "+
				"is an orphan\n", i)
		}
	}
}

// loadBlocks reads files containing bitcoin block data (gzipped but otherwise
// in the format bitcoind writes) from disk and returns them as an array of
// btcutil.Block.  This is largely borrowed from the test code in btcdb.
func loadBlocks(filename string) (blocks []*btcutil.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 *btcutil.Block

	err = nil
	for height := int64(1); 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 = btcutil.NewBlockFromBytes(rbytes)
		if err != nil {
			return
		}
		blocks = append(blocks, block)
	}

	return
}