// Copyright 2014 by Sascha L. Teichmann
// Use of this source code is governed by the MIT license
// that can be found in the LICENSE file.

package main

import (
	"flag"
	"fmt"
	"log"
	"os"
	"sync"

	"bitbucket.org/s_l_teichmann/mtsatellite/common"
)

func usage() {
	fmt.Fprintf(os.Stderr,
		"Usage: %s [<options>] <source database> <dest database>\n", os.Args[0])
	fmt.Fprintln(os.Stderr, "Options:")
	flag.PrintDefaults()
}

func selectKeySplitter(interleaved bool) common.KeySplitter {
	if interleaved {
		return common.InterleavedToCoord
	}
	return common.PlainToCoord
}

func selectKeyJoiner(interleaved bool) common.KeyJoiner {
	if interleaved {
		return common.CoordToInterleaved
	}
	return common.CoordToPlain
}

func selectKeyDecoder(interleaved bool) common.KeyDecoder {
	if interleaved {
		return common.DecodeFromBigEndian
	}
	return common.DecodeStringFromBytes
}

func selectKeyEncoder(interleaved bool) common.KeyEncoder {
	if interleaved {
		return common.EncodeToBigEndian
	}
	return common.EncodeStringToBytes
}

func copyProducerToConsumer(producer common.BlockProducer, consumer common.BlockConsumer) error {

	blocks := make(chan *common.Block)
	done := make(chan struct{})
	defer close(done)

	pool := sync.Pool{New: func() interface{} { return new(common.Block) }}

	go func() {
		defer close(blocks)
		for {
			block := pool.Get().(*common.Block)
			if err := producer.Next(block); err != nil {
				if err != common.ErrNoMoreBlocks {
					log.Printf("Reading failed: %s\n", err)
				}
				return
			}
			select {
			case blocks <- block:
			case <-done:
				return
			}
		}
	}()

	i := 0
	for block := range blocks {
		if err := consumer.Consume(block); err != nil {
			return err
		}
		block.Data = nil
		pool.Put(block)
		i++
		if i%1000 == 0 {
			log.Printf("%d blocks transferred.\n", i)
		}
	}
	log.Printf("%d blocks transferred in total.\n", i)

	return nil
}

func main() {
	var (
		srcBackend     string
		dstBackend     string
		srcInterleaved bool
		dstInterleaved bool
	)

	flag.Usage = usage

	flag.StringVar(&srcBackend, "source-backend", "sqlite",
		"type of source database (leveldb, sqlite)")
	flag.StringVar(&srcBackend, "sb", "sqlite",
		"type of source database (leveldb, sqlite). Shorthand")
	flag.StringVar(&dstBackend, "dest-backend", "leveldb",
		"type of destination database (leveldb, sqlite)")
	flag.StringVar(&dstBackend, "db", "leveldb",
		"type of destination database (leveldb, sqlite). Shorthand")
	flag.BoolVar(&srcInterleaved, "source-interleaved", false,
		"Is source database interleaved?")
	flag.BoolVar(&srcInterleaved, "si", false,
		"Is source database interleaved? Shorthand")
	flag.BoolVar(&dstInterleaved, "dest-interleaved", true,
		"Should dest database be interleaved?")
	flag.BoolVar(&dstInterleaved, "di", true,
		"Should source database be interleaved? Shorthand")

	flag.Parse()

	if flag.NArg() < 2 {
		log.Fatal("Missing source and/or destination database.")
	}

	var (
		producer common.BlockProducer
		consumer common.BlockConsumer
		err      error
	)

	if srcBackend == "sqlite" {
		if producer, err = NewSQLiteBlockProducer(
			flag.Arg(0),
			selectKeySplitter(srcInterleaved)); err != nil {
			log.Fatalf("Cannot open '%s': %s", flag.Arg(0), err)
		}
	} else { // LevelDB
		if producer, err = NewLevelDBBlockProducer(
			flag.Arg(0),
			selectKeySplitter(srcInterleaved),
			selectKeyDecoder(srcInterleaved)); err != nil {
			log.Fatalf("Cannot open '%s': %s", flag.Arg(0), err)
		}
	}
	defer producer.Close()

	if dstBackend == "sqlite" {
		if consumer, err = NewSQLiteBlockConsumer(
			flag.Arg(1),
			selectKeyJoiner(dstInterleaved)); err != nil {
			log.Fatalf("Cannot open '%s': %s", flag.Arg(1), err)
		}
	} else { // LevelDB
		if consumer, err = NewLevelDBBlockConsumer(
			flag.Arg(1),
			selectKeyJoiner(dstInterleaved),
			selectKeyEncoder(dstInterleaved)); err != nil {
			log.Fatalf("Cannot open '%s': %s", flag.Arg(1), err)
		}
	}
	defer consumer.Close()

	if err = copyProducerToConsumer(producer, consumer); err != nil {
		log.Fatalf("Database transfer failed: %s\n", err)
	}
}