package snapshot

import (
	"fmt"
	"io"
	"os"
	"path/filepath"

	"github.com/hashicorp/raft"
	"github.com/rqlite/rqlite/db"
)

type Snapshot struct {
	walData []byte
	files   []string
}

func NewWALSnapshot(b []byte) *Snapshot {
	return &Snapshot{
		walData: b,
	}
}

func NewFullSnapshot(files ...string) *Snapshot {
	return &Snapshot{
		files: files,
	}
}

func (s *Snapshot) Persist(sink raft.SnapshotSink) error {
	stream, err := s.OpenStream()
	if err != nil {
		return err
	}
	defer stream.Close()

	_, err = io.Copy(sink, stream)
	return err
}

func (s *Snapshot) Release() {
	return
}

func (s *Snapshot) OpenStream() (*Stream, error) {
	if len(s.files) > 0 {
		return NewFullStream(s.files...)
	}
	return NewIncrementalStream(s.walData)
}

func ReplayDB(fullSnap *FullSnapshot, r io.Reader, path string) error {
	dbInfo := fullSnap.GetDb()
	if dbInfo == nil {
		return fmt.Errorf("got nil DB info")
	}

	sqliteBaseFD, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("error creating SQLite file: %v", err)
	}
	if _, err := io.CopyN(sqliteBaseFD, r, dbInfo.Size); err != nil {
		return fmt.Errorf("error writing SQLite file data: %v", err)
	}
	if err := sqliteBaseFD.Close(); err != nil {
		return fmt.Errorf("error closing SQLite file: %v", err)
	}

	// Write out any WALs.
	var walFiles []string
	for i, wal := range fullSnap.GetWals() {
		if wal == nil {
			return fmt.Errorf("got nil WAL")
		}

		walName := filepath.Join(filepath.Dir(path), baseSqliteWALFile+fmt.Sprintf("%d", i))
		walFD, err := os.Create(walName)
		if err != nil {
			return fmt.Errorf("error creating WAL file: %v", err)
		}
		if _, err := io.CopyN(walFD, r, wal.Size); err != nil {
			return fmt.Errorf("error writing WAL file data: %v", err)
		}
		if err := walFD.Close(); err != nil {
			return fmt.Errorf("error closing WAL file: %v", err)
		}
		walFiles = append(walFiles, walName)
	}

	// Checkpoint the WAL files into the base SQLite file
	if err := db.ReplayWAL(path, walFiles, false); err != nil {
		return fmt.Errorf("error checkpointing WAL: %v", err)
	}
	return nil
}