radiodiodio/playlist/playlist.go

package playlist

import (
	"log"
	"time"
	"errors"
	"strconv"
	"math/rand"
	"encoding/json"
	"../archive"
	"../config"
)

var pln = log.Println

type Playlist struct {
	NAME 		string
	CTRACK		config.Track_t	
	CALBUM		config.Album_t
	LIST		[]uint32
	MAX			int
}

type PrettyPlaylist struct {
	NAME 		string
	CTRACK		config.Track_t	
	CALBUM		config.Album_t
	LIST		[]config.Track_t
	MAX			int
}


func MakeRandom(name string, max int) (*Playlist, error) {
	err := archive.Build()
	if err != nil {
		return nil, err
	}

	p := &Playlist{NAME: name, MAX: max}
	p.LIST = make([]uint32, max)

	for i := 0; i < max; i++ {
		r, _ := Random()
		p.LIST[i] = r			// might duplicate
	}

	return p, nil;
}

func (p *Playlist) Encode() string {

	pp := p.Pretty()
	res, _ := json.Marshal(pp)
	return string(res)

}

func Decode(jsonstr string) (*Playlist, error) {

	pp := &PrettyPlaylist{}

	if err := json.Unmarshal([]byte(jsonstr), pp); err != nil {
		return nil, err
	}

	p := pp.Unpretty()
	return p, nil
}

func (p *Playlist) Pretty() *PrettyPlaylist {
	pp := &PrettyPlaylist{NAME: p.NAME, CTRACK: p.CTRACK, CALBUM: p.CALBUM, MAX: p.MAX}
	pp.LIST = make([]config.Track_t, len(p.LIST))
	for i := 0; i < len(p.LIST); i++ {
		pp.LIST[i] =  archive.Archive_map[p.LIST[i]]
	}	
	return pp
}

func (pp *PrettyPlaylist) Unpretty() *Playlist {
	p := &Playlist{NAME: pp.NAME, CTRACK: pp.CTRACK, CALBUM: pp.CALBUM, MAX: pp.MAX}
	p.LIST = make([]uint32, len(pp.LIST))
	for i := 0; i < len(pp.LIST); i++ {
		p.LIST = append(p.LIST, pp.LIST[i].ID)
	}
	return p	
}

// type PrettyPlaylist struct {
// 	NAME 		string
// 	CTRACK		config.Track_t	
// 	CALBUM		config.Album_t
// 	LIST		[]config.Track_t
// 	MAX			int
// }


func (pp *PrettyPlaylist) Print() {

	pln("Name: " + pp.NAME)
	pln("CTRACK: " + pp.CTRACK.NAME)
	pln("CALBUM: " + pp.CALBUM.NAME)
	pln("Next:")
	for i, r := range pp.LIST {
		pln("	" + strconv.Itoa(i) + " - " + r.NAME)
	}
}

func print(slice []uint32) {
	for i, r := range slice {
		pln("	" + strconv.Itoa(i) + " - " + archive.Archive_map[r].NAME)
	}

}

// https://github.com/golang/go/wiki/SliceTricks
// https://stackoverflow.com/questions/33834742/remove-and-adding-elements-to-array-in-go-lang

func (p *Playlist) Pop() error {
	if len(p.LIST) == 0 {
		return errors.New("Playlist is empty")
	} 

	t := p.LIST[0]
	if len(p.LIST) < 2 {	
		p.LIST = make([]uint32, 0)
	} else {
		p.LIST = p.LIST[1:]
	}

	p.CTRACK = archive.Archive_map[t]
	p.CALBUM = config.Xcfg.Archive.ALBUMS[p.CTRACK.AID]

	return nil
}

func (p *Playlist) Push(track_id uint32) error {
	if len(p.LIST) == p.MAX {
		return errors.New("Playlist is full")
	}
	p.LIST = append(p.LIST, track_id)
	return nil	
}

func (p *Playlist) PushFront(track_id uint32) error {
	if len(p.LIST) == p.MAX {
		return errors.New("Playlist is full")
	}
	p.LIST = append([]uint32{ track_id }, p.LIST...)		// don't forget '...''
	return nil	
}

func (p *Playlist) Insert(track_id uint32, at_index int) error {
	if at_index > p.MAX {
		return errors.New("Invalid insert index")
	}

	p.LIST = append(p.LIST, 0)
	copy(p.LIST[at_index+1:], p.LIST[at_index:])
	p.LIST[at_index] = track_id

	if len(p.LIST) > p.MAX {
		p.LIST = p.LIST[:p.MAX]
	}
	
	return nil	
}

func (p *Playlist) index(track_id uint32) int {
	k := -1
	for i := 0; i < len(p.LIST); i++ {
		if p.LIST[i] == track_id { k = i }
	}
	return k	
}

func (p *Playlist) Delete(track_id uint32) error {
	k := p.index(track_id);
	if k < 0 {
		return errors.New("Invalid track ID")
	}
	p.LIST = append(p.LIST[:k-1], p.LIST[k+1:]...)
	return nil
}

func (p *Playlist) Move(track_id uint32, at_index int) error {
	if at_index > p.MAX {
		return errors.New("Invalid insert index")
	}
	k := p.index(track_id);
	if k < 0 {
		return errors.New("Invalid track ID")
	}

	slice_head := p.LIST[:k]
	slice_move := p.LIST[k+1:at_index+1]
	slice_tail := make([]uint32, len(p.LIST[at_index+1:]))
	copy(slice_tail, p.LIST[at_index+1:])

	// slice_move = append(slice_move, track_id)

	pln("from_index: " + strconv.Itoa(k))
	pln("at_index: " + strconv.Itoa(at_index))
	pln("------")
	pln("slice head: ")
	print(slice_head)
	pln("slice move: ")
	print(slice_move)
	pln("** ")
	pln("slice tail: ")
	print(slice_tail)
	pln("...........................")

	p.LIST = append(slice_head, append(append(slice_move, track_id), slice_tail...)...)

	return nil
}


func Random() (uint32, string) {
	rand.Seed(time.Now().UTC().UnixNano())
	index := archive.Archive_map_keys[rand.Intn(len(archive.Archive_map_keys) - 1)]
	return archive.Archive_map[index].ID, archive.Archive_map[index].NAME
}