//
//  pool-import
//
//  Copyright (C) 2016 Christian Pointner <equinox@helsinki.at>
//
//  This file is part of pool-import.
//
//  pool-import 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
//  any later version.
//
//  pool-import 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 pool-import. If not, see <http://www.gnu.org/licenses/>.
//

package main

import (
	"log"
	"math/rand"
	"os"
	"path/filepath"
	"sync"
	"time"
)

type MusicDir struct {
	root   string
	stdlog *log.Logger
	Files  map[string]string
}

func handleEntry(C chan<- string, path string, info os.FileInfo, err error, stdlog *log.Logger) error {
	if err != nil {
		return err
	}
	if info.IsDir() {
		stdlog.Printf("entering directory: %s", path)
		return nil
	}
	if !info.Mode().IsRegular() {
		stdlog.Printf(" - skipping special file: %s", path)
		return nil
	}
	// TODO: check file extensions
	C <- path
	return nil
}

func computeHash(file string) string {
	time.Sleep(time.Duration(rand.Float64() * float64(5*time.Second))) // TODO: faking it is nice but the real hash would be nicer
	return ""
}

func (d *MusicDir) collectHashes(C <-chan string, numThreads int) (wg *sync.WaitGroup) {
	wg = &sync.WaitGroup{}

	for i := 0; i < numThreads; i++ {
		wg.Add(1)
		d.stdlog.Printf("Starting hashing thread #%d", i)
		go func(num int) {
			defer wg.Done()
			for {
				file, ok := <-C
				if !ok {
					d.stdlog.Printf("Stopping hashing thread #%d", num)
					return
				}
				d.stdlog.Printf(" - hashing: %s", file)
				computeHash(file)
			}
		}(i)
	}
	return
}

func (d *MusicDir) ComputeHashes() (err error) {
	C := make(chan string, 10)

	wg := d.collectHashes(C, 4) // TODO: make number of hashing threads configurable

	err = filepath.Walk(d.root, func(path string, info os.FileInfo, err error) error {
		return handleEntry(C, path, info, err, d.stdlog)
	})
	close(C)

	if err != nil {
		return
	}

	wg.Wait()
	return
}

func NewMusicDir(root string, stdlog *log.Logger) (dir *MusicDir) {
	dir = &MusicDir{root: root, stdlog: stdlog}
	dir.Files = make(map[string]string)
	return
}