/*
 * Wiki - A wiki with editor
 * Copyright (c) 2021-2021 Peter Stuifzand
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package main

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
)

type BlockRepository interface {
	Save(id string, block Block) error
	Load(id string) (Block, error)
}

type blockSaveMessage struct {
	id    string
	block Block
}

type blockRepo struct {
	dirname string
	saveC   chan blockSaveMessage
	errC    chan error
}

func saveBlock(dirname, id string, block Block) error {
	f, err := os.OpenFile(filepath.Join(dirname, BlocksDirectory, id), os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
	if err != nil {
		return err
	}
	defer f.Close()
	enc := json.NewEncoder(f)
	enc.SetIndent("", "  ")
	err = enc.Encode(&block)
	if err != nil {
		return err
	}
	return nil
}

func NewBlockRepo(dirname string) BlockRepository {
	saveC := make(chan blockSaveMessage, 1)
	errC := make(chan error)
	go func() {
		for msg := range saveC {
			err := saveBlock(dirname, msg.id, msg.block)
			errC <- err
		}
	}()
	return &blockRepo{
		dirname: dirname,
		saveC:   saveC,
		errC:    errC,
	}
}

func (br *blockRepo) Save(id string, block Block) error {
	br.saveC <- blockSaveMessage{id, block}
	err := <-br.errC
	return err
}

func (br *blockRepo) Load(id string) (Block, error) {
	f, err := os.Open(filepath.Join(br.dirname, BlocksDirectory, id))
	if err != nil {
		return Block{}, fmt.Errorf("%q: %w", id, BlockNotFound)
	}
	defer f.Close()
	var block Block
	err = json.NewDecoder(f).Decode(&block)
	if err != nil {
		return Block{}, fmt.Errorf("%q: %w", id, err)
	}
	return block, nil
}