package importer

import (
	"fmt"
	"path/filepath"
	"strings"
	"unicode/utf8"
)

// Placement is where one file goes and the names written into its tags.
type Placement struct {
	File   int    // index into the files
	Dest   string // absolute
	Title  string
	Disc   int
	Discs  int
	Track  int
	Tracks int // on its disc
	// Recording is the MusicBrainz recording the file was matched to.
	Recording string
}

// Plan names every file's destination under root the way the library is
// already named (note #5527), so new arrivals sit beside what is there:
//
//	{Artist}/{Album} ({Year})/{Artist} - {Album} - {track:00} - {Title}.ext
//
// with a "{Medium Format} {medium:00}" folder between when the edition has
// more than one medium. A file the check paired to a track takes the track's
// name and place; one it did not (an "import anyway" with more files than
// tracks) keeps its own tags.
func Plan(root string, w Want, e *Edition, files []File, pairs []Pair) []Placement {
	album := w.Title
	if w.Year > 0 {
		album = fmt.Sprintf("%s (%d)", w.Title, w.Year)
	}
	dir := filepath.Join(root, Segment(w.Artist), Segment(album))
	media := 1
	if e != nil {
		media = max(e.Media(), 1)
	}
	perDisc := map[int]int{}
	if e != nil {
		for _, t := range e.Tracks {
			perDisc[t.Medium]++
		}
	}
	paired := map[int]Pair{}
	for _, p := range pairs {
		paired[p.File] = p
	}

	out := make([]Placement, 0, len(files))
	for i, f := range files {
		pl := Placement{File: i, Title: f.Title, Disc: max(f.Disc, 1), Track: f.Track, Discs: media}
		format := ""
		if p, ok := paired[i]; ok && e != nil {
			t := e.Tracks[p.Track]
			pl.Title, pl.Disc, pl.Track, pl.Recording, format = t.Title, max(t.Medium, 1), t.Position, t.RecordingMBID, t.Format
			pl.Tracks = perDisc[t.Medium]
		}
		if pl.Title == "" {
			pl.Title = strings.TrimSuffix(filepath.Base(f.Path), filepath.Ext(f.Path))
		}
		d := dir
		if media > 1 {
			if format == "" {
				format = "Disc"
			}
			d = filepath.Join(dir, Segment(fmt.Sprintf("%s %02d", format, pl.Disc)))
		}
		name := fmt.Sprintf("%s - %s - %02d - %s", w.Artist, w.Title, pl.Track, pl.Title)
		pl.Dest = filepath.Join(d, Segment(name)+strings.ToLower(filepath.Ext(f.Path)))
		out = append(out, pl)
	}
	return out
}

// segmentMax keeps a folder or file name inside the 255 bytes most
// filesystems allow, with room for an extension and a temp prefix.
const segmentMax = 200

var illegal = strings.NewReplacer(
	`\`, "+", "/", "+", "<", "", ">", "", "?", "!", "*", "-", "|", "", `"`, "",
	// The "smart" colon: "Title: Subtitle" reads "Title - Subtitle".
	": ", " - ", ":", "-",
)

// Segment makes a name safe as one path segment, the way the *arr programs
// clean file names: their illegal-character mapping, no leading or trailing
// spaces or dots, at most segmentMax bytes, never "" or "..".
func Segment(s string) string {
	s = illegal.Replace(s)
	s = strings.Map(func(r rune) rune {
		if r < 0x20 || r == 0x7f {
			return -1
		}
		return r
	}, s)
	s = strings.Trim(s, " .")
	for len(s) > segmentMax {
		_, size := utf8.DecodeLastRuneInString(s)
		s = strings.TrimRight(s[:len(s)-size], " .")
	}
	if s == "" {
		return "_"
	}
	return s
}