/*
Copyright © 2023 Philipp Wolfer <phw@uploadedlobster.com>

This file is part of Scotty.

Scotty 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.

Scotty 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
Scotty. If not, see <https://www.gnu.org/licenses/>.
*/
package scrobblerlog

import (
	"bufio"
	"os"
	"sort"
	"time"

	"github.com/spf13/viper"
	"go.uploadedlobster.com/scotty/models"
)

type ScrobblerLogBackend struct {
	filePath       string
	includeSkipped bool
	append         bool
	file           *os.File
	log            ScrobblerLog
}

func (b *ScrobblerLogBackend) Name() string { return "scrobbler-log" }

func (b *ScrobblerLogBackend) FromConfig(config *viper.Viper) models.Backend {
	b.filePath = config.GetString("file-path")
	b.includeSkipped = config.GetBool("include-skipped")
	b.append = true
	if config.IsSet("append") {
		b.append = config.GetBool("append")
	}
	b.log = ScrobblerLog{
		Timezone: "UNKNOWN",
		Client:   "Rockbox unknown $Revision$",
	}
	return b
}

func (b *ScrobblerLogBackend) StartImport() error {
	flags := os.O_RDWR | os.O_CREATE
	if !b.append {
		flags |= os.O_TRUNC
	}
	file, err := os.OpenFile(b.filePath, flags, 0666)
	if err != nil {
		return err
	}

	if b.append {
		stat, err := file.Stat()
		if err != nil {
			file.Close()
			return err
		}

		if stat.Size() == 0 {
			// Zero length file, treat as a new file
			b.append = false
		} else {
			// Verify existing file is a scrobbler log
			reader := bufio.NewReader(file)
			err = ReadHeader(reader, &b.log)
			if err != nil {
				file.Close()
				return err
			}
			file.Seek(0, 2)
		}
	}

	if !b.append {
		err = WriteHeader(file, &b.log)
		if err != nil {
			file.Close()
			return err
		}
	}

	b.file = file
	return nil
}

func (b *ScrobblerLogBackend) FinishImport() error {
	return b.file.Close()
}

func (b *ScrobblerLogBackend) ExportListens(oldestTimestamp time.Time, results chan models.ListensResult, progress chan models.Progress) {
	defer close(results)
	file, err := os.Open(b.filePath)
	if err != nil {
		progress <- models.Progress{}.Complete()
		results <- models.ListensResult{Error: err}
		return
	}

	defer file.Close()

	log, err := Parse(file, b.includeSkipped)
	if err != nil {
		progress <- models.Progress{}.Complete()
		results <- models.ListensResult{Error: err}
		return
	}

	listens := log.Listens.NewerThan(oldestTimestamp)
	sort.Sort(listens)
	progress <- models.Progress{Elapsed: int64(len(listens))}.Complete()
	results <- models.ListensResult{Listens: listens}
}

func (b *ScrobblerLogBackend) ImportListens(export models.ListensResult, importResult models.ImportResult, progress chan models.Progress) (models.ImportResult, error) {
	lastTimestamp, err := Write(b.file, export.Listens)
	if err != nil {
		return importResult, err
	}

	importResult.UpdateTimestamp(lastTimestamp)
	importResult.ImportCount += len(export.Listens)
	progress <- models.Progress{}.FromImportResult(importResult)

	return importResult, nil
}