// Copyright (c) 2026 Jeremy Baxter.
// HTML builders

package server

import (
	"cmp"
	"embed"
	"fmt"
	"slices"
	"strings"

	"html/template"
	"math/rand"
	"net/http"
	"net/url"

	"git.baxters.nz/jeremy/records/musicindex"
	"git.baxters.nz/jeremy/records/util"
)

//go:embed static/*
var staticFS embed.FS

type Page interface {
	Body() template.HTML
	SourceFile() string
	Title() string
}

func writePage(p Page, w http.ResponseWriter) {
	t, err := template.ParseFS(staticFS, "static/templates/" + p.SourceFile())
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	err = t.Execute(w, p)
	if err != nil {
		w.Write([]byte(err.Error()))
	}
}

type IndexPage struct {
	Showcase string
}

func MakeIndexPage() (p IndexPage) {
	albums := musicindex.Albums()
	rand.Shuffle(len(albums), func(i, j int) {
		albums[i], albums[j] = albums[j], albums[i]
	})

	i := 0

	var b strings.Builder
	b.WriteString(`<div class="grid">`)

	for i < len(albums) {
		b.WriteString(`<div class="row">`)
		for range 3 {
			fmt.Fprintf(&b, `<a href="/%s"><img width="300" height="300" src="/media/%s"></a>`,
				util.EscapePath(albums[i].RelativeDirectory()),
				util.EscapePath(albums[i].RelativeCoverPath()))
			i++
			if i >= len(albums) {
				break
			}	
		}
		b.WriteString(`</div>`)
	}

	b.WriteString(`</div>`)
	p.Showcase = b.String()

	return
}

func (p IndexPage) SourceFile() string { return "base.html" }
func (p IndexPage) Title() string { return "records.baxters.nz" }
func (p IndexPage) Body() template.HTML {
	return template.HTML(p.Showcase)
}

func writeSortingWidget(b *strings.Builder, sortBy string, sortOptions []string, count int, itemDesc string) {
	b.WriteString(fmt.Sprintf(`<div class="sortby">sorting %d %s by %s;`,
		count, itemDesc, sortBy))
	for _, v := range sortOptions {
		if v == sortBy {
			continue
		}
		b.WriteString(` <a href="?by=` + v + `">` + v + `</a>`)
	}
	b.WriteString(`</div>`)
}

type ArtistsPage struct {
	bodyHTML string
}

func ArtistSortOptions() []string {
	return []string{"name", "albums", "songs"}
}

func MakeArtistsPage(sortBy string) (p ArtistsPage) {
	var b strings.Builder

	artistNames := musicindex.Artists()
	writeSortingWidget(&b, sortBy, ArtistSortOptions(), len(artistNames),
		"artist" + util.OptionalString(len(artistNames) != 1, "s"))

	b.WriteString(`<div class="artists"><ul>`)

	var artists []musicindex.Artist
	for _, name := range artistNames {
		artists = append(artists, musicindex.FindArtist(name))
	}

	switch sortBy {
	case "albums":
		slices.SortFunc(artists, func(a, b musicindex.Artist) int {
			return cmp.Compare(len(b.Albums), len(a.Albums))
		})
	case "songs":
		slices.SortFunc(artists, func(a, b musicindex.Artist) int {
			return cmp.Compare(b.Songs, a.Songs)
		})
	case "name":  // already sorted
		fallthrough
	default:
	}

 	for _, artist := range artists {
		albums := len(artist.Albums)
		b.WriteString(fmt.Sprintf(`<li class="artist"><a href="/%s">%s</a>`,
			url.QueryEscape(artist.Name), artist.Name))
		b.WriteString(fmt.Sprintf("<br>%d album%s, %d songs</li><br>",
			albums, util.OptionalString(albums != 1, "s"), artist.Songs))
	}

	b.WriteString(`</div>`)
	p.bodyHTML = b.String()

	return
}

func (p ArtistsPage) SourceFile() string { return "base.html" }
func (p ArtistsPage) Title() string { return "records.baxters.nz - artists" }
func (p ArtistsPage) Body() template.HTML { return template.HTML(p.bodyHTML) }

type AlbumsPage struct {
	bodyHTML string
}

func AlbumSortOptions() []string {
	return []string{"name", "artist", "songs"}
}

func writeAlbums(b *strings.Builder, sortBy string, albums []musicindex.Album, artistAlbums bool) {
	sortOptions := AlbumSortOptions()
	if artistAlbums {
		// remove the option to sort by "artist"
		sortOptions = slices.DeleteFunc(sortOptions, func(s string) bool {
			return s == "artist"
		})
	}

	writeSortingWidget(b, sortBy, sortOptions, len(albums),
		"album" + util.OptionalString(len(albums) != 1, "s"))
	b.WriteString(`<br><div class="albums"><table><tbody>`)

	switch sortBy {
	case "artist":
		slices.SortFunc(albums, func(a, b musicindex.Album) int {
			return cmp.Compare(a.Artist.Name, b.Artist.Name)
		})
	case "songs":
		slices.SortFunc(albums, func(a, b musicindex.Album) int {
			return cmp.Compare(len(b.TrackFiles), len(a.TrackFiles))
		})
	case "name":  // already sorted
		fallthrough
	default:
		slices.SortFunc(albums, func(a, b musicindex.Album) int {
			return cmp.Compare(a.Name, b.Name)
		})
	}

 	for _, album := range albums {
		b.WriteString(`<tr class="album"><td><img `)
		b.WriteString(fmt.Sprintf(`src="/media/%s" width="100" height="100"></td>`,
			url.QueryEscape(album.RelativeCoverPath())))
		b.WriteString(fmt.Sprintf(`<td><a href="/%s">%s</a><br><br>%s<br>%d songs</td></tr>`,
			util.EscapePath(album.RelativeDirectory()),
			album.Name, album.Artist.Name, len(album.TrackFiles)))
	}
	b.WriteString(`</tbody></table></div>`)
}

func MakeAlbumsPage(sortBy string) (p AlbumsPage) {
	var b strings.Builder

	writeAlbums(&b, sortBy, musicindex.Albums(), false)
	p.bodyHTML = b.String()

	return
}

func (p AlbumsPage) SourceFile() string { return "base.html" }
func (p AlbumsPage) Title() string { return "records.baxters.nz - albums" }
func (p AlbumsPage) Body() template.HTML { return template.HTML(p.bodyHTML) }

type ArtistPage struct {
	Artist musicindex.Artist
	bodyHTML string
}

func MakeArtistPage(sortBy string, name string) (p ArtistPage) {
	var b strings.Builder

	artist := musicindex.FindArtist(name)
	b.WriteString(`<h3>` + artist.Name + `</h3>`)

	writeAlbums(&b, sortBy, util.MapToValues(artist.Albums), true)

	p.Artist = artist
	p.bodyHTML = b.String()

	return
}

func (p ArtistPage) SourceFile() string { return "base.html" }
func (p ArtistPage) Title() string { return "records.baxters.nz - artist " + p.Artist.Name }
func (p ArtistPage) Body() template.HTML { return template.HTML(p.bodyHTML) }

type AlbumPage struct {
	Album musicindex.Album
	bodyHTML string
}

func MakeAlbumPage(album musicindex.Album) (p AlbumPage) {
	var b strings.Builder

	b.WriteString(`<br><div class="album"><div class="album-cover">`)
	b.WriteString(`<img width="300" height="300" src="/media/`)
	b.WriteString(album.RelativeCoverPath() + `"></div>`)
	b.WriteString(`<div class="album-data"><div class="album-meta"><h3>`)
	b.WriteString(album.Name + `</h3><a class="artist" href="/`)
	b.WriteString(url.QueryEscape(album.Artist.Name) + `">` + album.Artist.Name)
	b.WriteString(`</a></div><br><div class="album-tracks"><ul>`)

	for _, track := range album.TrackFiles {
		b.WriteString(`<li class="trackfile"><a href="/media/`)
		b.WriteString(album.RelativeDirectory() + `/` + track)
		b.WriteString(`">` + track + `</a></li>`)
	}

	tarball := album.Name + ".tar.gz"
	tarballURI := "/" + url.QueryEscape(album.Artist.Name) + "/" +
		url.QueryEscape(tarball)

	b.WriteString(`</ul><h4>Download album</h4><a class="tarball" href="`)
	b.WriteString(tarballURI + `">&#x2925; ` + tarball)
	b.WriteString(fmt.Sprintf(` (%d MiB)</a></div></div></div>`,
		album.TarballSize / (1024 * 1024)))

	p.Album = album
	p.bodyHTML = b.String()

	return
}

func (p AlbumPage) SourceFile() string { return "base.html" }
func (p AlbumPage) Title() string { return "records.baxters.nz - " + p.Album.Name }
func (p AlbumPage) Body() template.HTML { return template.HTML(p.bodyHTML) }