/*
Copyright IBM Corp. 2016 All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

                 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package fileledger

import (
	"github.com/hyperledger/fabric/common/flogging"
	"github.com/hyperledger/fabric/common/ledger"
	"github.com/hyperledger/fabric/common/ledger/blockledger"
	cb "github.com/hyperledger/fabric/protos/common"
	ab "github.com/hyperledger/fabric/protos/orderer"

	"github.com/op/go-logging"
)

const pkgLogID = "common/ledger/blockledger/file"

var logger *logging.Logger

var closedChan chan struct{}

func init() {
	logger = flogging.MustGetLogger(pkgLogID)
	closedChan = make(chan struct{})
	close(closedChan)
}

// FileLedger is a struct used to interact with a node's ledger
type FileLedger struct {
	blockStore FileLedgerBlockStore
	signal     chan struct{}
}

// FileLedgerBlockStore defines the interface to interact with deliver when using a
// file ledger
type FileLedgerBlockStore interface {
	AddBlock(block *cb.Block) error
	GetBlockchainInfo() (*cb.BlockchainInfo, error)
	RetrieveBlocks(startBlockNumber uint64) (ledger.ResultsIterator, error)
}

// NewFileLedger creates a new FileLedger for interaction with the ledger
func NewFileLedger(blockStore FileLedgerBlockStore) *FileLedger {
	return &FileLedger{blockStore: blockStore, signal: make(chan struct{})}
}

type fileLedgerIterator struct {
	ledger         *FileLedger
	blockNumber    uint64
	commonIterator ledger.ResultsIterator
}

// Next blocks until there is a new block available, or until Close is called.
// It returns an error if the next block is no longer retrievable.
func (i *fileLedgerIterator) Next() (*cb.Block, cb.Status) {
	result, err := i.commonIterator.Next()
	if err != nil {
		logger.Error(err)
		return nil, cb.Status_SERVICE_UNAVAILABLE
	}
	// Cover the case where another thread calls Close on the iterator.
	if result == nil {
		return nil, cb.Status_SERVICE_UNAVAILABLE
	}
	return result.(*cb.Block), cb.Status_SUCCESS
}

// ReadyChan supplies a channel which will block until Next will not block
func (i *fileLedgerIterator) ReadyChan() <-chan struct{} {
	signal := i.ledger.signal
	if i.blockNumber > i.ledger.Height()-1 {
		return signal
	}
	return closedChan
}

// Close releases resources acquired by the Iterator
func (i *fileLedgerIterator) Close() {
	i.commonIterator.Close()
}

// Iterator returns an Iterator, as specified by an ab.SeekInfo message, and its
// starting block number
func (fl *FileLedger) Iterator(startPosition *ab.SeekPosition) (blockledger.Iterator, uint64) {
	var startingBlockNumber uint64
	switch start := startPosition.Type.(type) {
	case *ab.SeekPosition_Oldest:
		startingBlockNumber = 0
	case *ab.SeekPosition_Newest:
		info, err := fl.blockStore.GetBlockchainInfo()
		if err != nil {
			logger.Panic(err)
		}
		newestBlockNumber := info.Height - 1
		startingBlockNumber = newestBlockNumber
	case *ab.SeekPosition_Specified:
		startingBlockNumber = start.Specified.Number
		height := fl.Height()
		if startingBlockNumber > height {
			return &blockledger.NotFoundErrorIterator{}, 0
		}
	default:
		return &blockledger.NotFoundErrorIterator{}, 0
	}

	iterator, err := fl.blockStore.RetrieveBlocks(startingBlockNumber)
	if err != nil {
		return &blockledger.NotFoundErrorIterator{}, 0
	}

	return &fileLedgerIterator{ledger: fl, blockNumber: startingBlockNumber, commonIterator: iterator}, startingBlockNumber
}

// Height returns the number of blocks on the ledger
func (fl *FileLedger) Height() uint64 {
	info, err := fl.blockStore.GetBlockchainInfo()
	if err != nil {
		logger.Panic(err)
	}
	return info.Height
}

// Append a new block to the ledger
func (fl *FileLedger) Append(block *cb.Block) error {
	err := fl.blockStore.AddBlock(block)
	if err == nil {
		close(fl.signal)
		fl.signal = make(chan struct{})
	}
	return err
}