// newBlockManager returns a new bitcoin block manager.
// Use Start to begin processing asynchronous block and inv updates.
func newBlockManager(s *server) (*blockManager, error) {
	bm := blockManager{
		server:           s,
		blockPeer:        make(map[btcwire.ShaHash]*peer),
		requestedTxns:    make(map[btcwire.ShaHash]bool),
		requestedBlocks:  make(map[btcwire.ShaHash]bool),
		lastBlockLogTime: time.Now(),
		msgChan:          make(chan interface{}, cfg.MaxPeers*3),
		quit:             make(chan bool),
	}
	bm.blockChain = btcchain.New(s.db, s.btcnet, bm.handleNotifyMsg)
	bm.blockChain.DisableCheckpoints(cfg.DisableCheckpoints)
	if cfg.DisableCheckpoints {
		log.Info("BMGR: Checkpoints are disabled")
	}

	log.Infof("BMGR: Generating initial block node index.  This may " +
		"take a while...")
	err := bm.blockChain.GenerateInitialIndex()
	if err != nil {
		return nil, err
	}
	log.Infof("BMGR: Block index generation complete")

	return &bm, nil
}

// newBlockImporter returns a new importer for the provided file reader seeker
// and database.
func newBlockImporter(db btcdb.Db, r io.ReadSeeker) *blockImporter {
	return &blockImporter{
		db:           db,
		r:            r,
		processQueue: make(chan []byte, 2),
		doneChan:     make(chan bool),
		errChan:      make(chan error),
		quit:         make(chan bool),
		chain:        btcchain.New(db, activeNetwork, nil),
	}
}

// newBlockImporter returns a new importer for the provided file reader seeker
// and database.
func newBlockImporter(db btcdb.Db, r io.ReadSeeker) *blockImporter {
	return &blockImporter{
		db:           db,
		r:            r,
		processQueue: make(chan []byte, 2),
		doneChan:     make(chan bool),
		errChan:      make(chan error),
		quit:         make(chan struct{}),
		chain:        btcchain.New(db, activeNetParams, nil),
		lastLogTime:  time.Now(),
	}
}

// newBlockManager returns a new bitcoin block manager.
// Use Start to begin processing asynchronous block and inv updates.
func newBlockManager(s *server) (*blockManager, error) {
	newestHash, height, err := s.db.NewestSha()
	if err != nil {
		return nil, err
	}

	bm := blockManager{
		server:           s,
		blockPeer:        make(map[btcwire.ShaHash]*peer),
		requestedTxns:    make(map[btcwire.ShaHash]bool),
		requestedBlocks:  make(map[btcwire.ShaHash]bool),
		lastBlockLogTime: time.Now(),
		msgChan:          make(chan interface{}, cfg.MaxPeers*3),
		headerList:       list.New(),
		quit:             make(chan bool),
	}
	bm.blockChain = btcchain.New(s.db, s.btcnet, bm.handleNotifyMsg)
	bm.blockChain.DisableCheckpoints(cfg.DisableCheckpoints)
	if !cfg.DisableCheckpoints {
		// Initialize the next checkpoint based on the current height.
		bm.nextCheckpoint = bm.findNextHeaderCheckpoint(height)
		if bm.nextCheckpoint != nil {
			bm.resetHeaderState(newestHash, height)
		}
	} else {
		bmgrLog.Info("Checkpoints are disabled")
	}

	bmgrLog.Infof("Generating initial block node index.  This may " +
		"take a while...")
	err = bm.blockChain.GenerateInitialIndex()
	if err != nil {
		return nil, err
	}
	bmgrLog.Infof("Block index generation complete")

	// Initialize the chain state now that the intial block node index has
	// been generated.
	bm.updateChainState(newestHash, height)

	return &bm, nil
}

// This example demonstrates how to create a new chain instance and use
// ProcessBlock to attempt to attempt add a block to the chain.  As the package
// overview documentation describes, this includes all of the Bitcoin consensus
// rules.  This example intentionally attempts to insert a duplicate genesis
// block to illustrate how an invalid block is handled.
func ExampleBlockChain_ProcessBlock() {
	// Create a new database to store the accepted blocks into.  Typically
	// this would be opening an existing database and would not use memdb
	// which is a memory-only database backend, but we create a new db
	// here so this is a complete working example.
	db, err := btcdb.CreateDB("memdb")
	if err != nil {
		fmt.Printf("Failed to create database: %v\n", err)
		return
	}
	defer db.Close()

	// Insert the main network genesis block.  This is part of the initial
	// database setup.  Like above, this typically would not be needed when
	// opening an existing database.
	genesisBlock := btcutil.NewBlock(btcnet.MainNetParams.GenesisBlock)
	_, err = db.InsertBlock(genesisBlock)
	if err != nil {
		fmt.Printf("Failed to insert genesis block: %v\n", err)
		return
	}

	// Create a new BlockChain instance using the underlying database for
	// the main bitcoin network and ignore notifications.
	chain := btcchain.New(db, &btcnet.MainNetParams, nil)

	// Process a block.  For this example, we are going to intentionally
	// cause an error by trying to process the genesis block which already
	// exists.
	isOrphan, err := chain.ProcessBlock(genesisBlock, btcchain.BFNone)
	if err != nil {
		fmt.Printf("Failed to process block: %v\n", err)
		return
	}
	fmt.Printf("Block accepted. Is it an orphan?: %v", isOrphan)

	// Output:
	// Failed to process block: already have block 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
}

// findCandidates searches the chain backwards for checkpoint candidates and
// returns a slice of found candidates, if any.  It also stops searching for
// candidates at the last checkpoint that is already hard coded into btcchain
// since there is no point in finding candidates before already existing
// checkpoints.
func findCandidates(db btcdb.Db, latestHash *btcwire.ShaHash) ([]*btcchain.Checkpoint, error) {
	// Start with the latest block of the main chain.
	block, err := db.FetchBlockBySha(latestHash)
	if err != nil {
		return nil, err
	}

	// Setup chain and get the latest checkpoint.  Ignore notifications
	// since they aren't needed for this util.
	chain := btcchain.New(db, activeNetwork, nil)
	latestCheckpoint := chain.LatestCheckpoint()
	if latestCheckpoint == nil {
		return nil, fmt.Errorf("unable to retrieve latest checkpoint")
	}

	// The latest known block must be at least the last known checkpoint
	// plus required checkpoint confirmations.
	checkpointConfirmations := int64(btcchain.CheckpointConfirmations)
	requiredHeight := latestCheckpoint.Height + checkpointConfirmations
	if block.Height() < requiredHeight {
		return nil, fmt.Errorf("the block database is only at height "+
			"%d which is less than the latest checkpoint height "+
			"of %d plus required confirmations of %d",
			block.Height(), latestCheckpoint.Height,
			checkpointConfirmations)
	}

	// Indeterminate progress setup.
	numBlocksToTest := block.Height() - requiredHeight
	progressInterval := (numBlocksToTest / 100) + 1 // min 1
	fmt.Print("Searching for candidates")
	defer fmt.Println()

	// Loop backwards through the chain to find checkpoint candidates.
	var candidates []*btcchain.Checkpoint
	numTested := int64(0)
	for len(candidates) < cfg.NumCandidates && block.Height() > requiredHeight {
		// Display progress.
		if numTested%progressInterval == 0 {
			fmt.Print(".")
		}

		// Determine if this block is a checkpoint candidate.
		isCandidate, err := chain.IsCheckpointCandidate(block)
		if err != nil {
			return nil, err
		}

		// All checks passed, so this node seems like a reasonable
		// checkpoint candidate.
		if isCandidate {
			candidateHash, err := block.Sha()
			if err != nil {
				return nil, err
			}
			checkpoint := btcchain.Checkpoint{
				Height: block.Height(),
				Hash:   candidateHash,
			}
			candidates = append(candidates, &checkpoint)
		}

		prevHash := &block.MsgBlock().Header.PrevBlock
		block, err = db.FetchBlockBySha(prevHash)
		if err != nil {
			return nil, err
		}
		numTested++
	}
	return candidates, nil
}

// chainSetup is used to create a new db and chain instance with the genesis
// block already inserted.  In addition to the new chain instnce, it returns
// a teardown function the caller should invoke when done testing to clean up.
func chainSetup(dbName string) (*btcchain.BlockChain, func(), error) {
	if !isSupportedDbType(testDbType) {
		return nil, nil, fmt.Errorf("unsupported db type %v", testDbType)
	}

	// Handle memory database specially since it doesn't need the disk
	// specific handling.
	var db btcdb.Db
	var teardown func()
	if testDbType == "memdb" {
		ndb, err := btcdb.CreateDB(testDbType)
		if err != nil {
			return nil, nil, fmt.Errorf("error creating db: %v", err)
		}
		db = ndb

		// Setup a teardown function for cleaning up.  This function is
		// returned to the caller to be invoked when it is done testing.
		teardown = func() {
			db.Close()
		}
	} else {
		// Create the root directory for test databases.
		if !fileExists(testDbRoot) {
			if err := os.MkdirAll(testDbRoot, 0700); err != nil {
				err := fmt.Errorf("unable to create test db "+
					"root: %v", err)
				return nil, nil, err
			}
		}

		// Create a new database to store the accepted blocks into.
		dbPath := filepath.Join(testDbRoot, dbName)
		_ = os.RemoveAll(dbPath)
		ndb, err := btcdb.CreateDB(testDbType, dbPath)
		if err != nil {
			return nil, nil, fmt.Errorf("error creating db: %v", err)
		}
		db = ndb

		// Setup a teardown function for cleaning up.  This function is
		// returned to the caller to be invoked when it is done testing.
		teardown = func() {
			dbVersionPath := filepath.Join(testDbRoot, dbName+".ver")
			db.Sync()
			db.Close()
			os.RemoveAll(dbPath)
			os.Remove(dbVersionPath)
			os.RemoveAll(testDbRoot)
		}
	}

	// Insert the main network genesis block.  This is part of the initial
	// database setup.
	genesisBlock := btcutil.NewBlock(&btcwire.GenesisBlock)
	_, err := db.InsertBlock(genesisBlock)
	if err != nil {
		teardown()
		err := fmt.Errorf("failed to insert genesis block: %v", err)
		return nil, nil, err
	}

	chain := btcchain.New(db, btcwire.MainNet, nil)
	return chain, teardown, nil
}