// Copyright 2014 The Cayley Authors. 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 db

import (
	"errors"
	"fmt"
	"io"

	"github.com/barakmich/glog"

	"github.com/google/cayley/graph"
	"github.com/google/cayley/internal/config"
	"github.com/google/cayley/quad"
)

var ErrNotPersistent = errors.New("database type is not persistent")

func Init(cfg *config.Config) error {
	if !graph.IsPersistent(cfg.DatabaseType) {
		return fmt.Errorf("ignoring unproductive database initialization request: %v", ErrNotPersistent)
	}

	return graph.InitQuadStore(cfg.DatabaseType, cfg.DatabasePath, cfg.DatabaseOptions)
}

func Open(cfg *config.Config) (*graph.Handle, error) {
	qs, err := OpenQuadStore(cfg)
	if err != nil {
		return nil, err
	}
	qw, err := OpenQuadWriter(qs, cfg)
	if err != nil {
		return nil, err
	}
	return &graph.Handle{QuadStore: qs, QuadWriter: qw}, nil
}

func OpenQuadStore(cfg *config.Config) (graph.QuadStore, error) {
	glog.Infof("Opening quad store %q at %s", cfg.DatabaseType, cfg.DatabasePath)
	qs, err := graph.NewQuadStore(cfg.DatabaseType, cfg.DatabasePath, cfg.DatabaseOptions)
	if err != nil {
		return nil, err
	}

	return qs, nil
}

func OpenQuadWriter(qs graph.QuadStore, cfg *config.Config) (graph.QuadWriter, error) {
	glog.Infof("Opening replication method %q", cfg.ReplicationType)
	w, err := graph.NewQuadWriter(cfg.ReplicationType, qs, cfg.ReplicationOptions)
	if err != nil {
		return nil, err
	}

	return w, nil
}

func Load(qw graph.QuadWriter, cfg *config.Config, dec quad.Unmarshaler) error {
	block := make([]quad.Quad, 0, cfg.LoadSize)
	count := 0
	for {
		t, err := dec.Unmarshal()
		if err != nil {
			if err == io.EOF {
				break
			}
			return err
		}
		block = append(block, t)
		if len(block) == cap(block) {
			count += len(block)
			err := qw.AddQuadSet(block)
			if err != nil {
				return fmt.Errorf("db: failed to load data: %v", err)
			}
			block = block[:0]
			if glog.V(2) {
				glog.V(2).Infof("Wrote %d quads.", count)
			}
		}
	}
	count += len(block)
	err := qw.AddQuadSet(block)
	if err != nil {
		return fmt.Errorf("db: failed to load data: %v", err)
	}
	if glog.V(2) {
		glog.V(2).Infof("Wrote %d quads.", count)
	}

	return nil
}