package main

import (
	"encoding/json"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"time"
)

// Tag is a normalized album tag: a lowercase free-text Name and its URL Slug.
type Tag struct {
	Name string
	Slug string
}

// Album is all photos sharing one tag, newest first.
type Album struct {
	Tag    Tag
	Count  int
	Photos []Photo
}

// parseTags normalizes raw tag strings into unique Tags. Each input may itself
// be comma-separated (as typed in the upload form), so entries are split on
// commas, lowercased, trimmed, de-duplicated by name, and given a URL slug via
// sanitiseSlug. Entries that are empty or slug to nothing are dropped.
func parseTags(raw ...string) []Tag {
	var tags []Tag
	seen := map[string]bool{}
	for _, entry := range raw {
		for _, part := range strings.Split(entry, ",") {
			name := strings.ToLower(strings.TrimSpace(part))
			if name == "" || seen[name] {
				continue
			}
			slug := sanitiseSlug(name)
			if slug == "" {
				continue
			}
			seen[name] = true
			tags = append(tags, Tag{Name: name, Slug: slug})
		}
	}
	return tags
}

// groupByTag collapses photos (already sorted newest first) into one Album per
// distinct tag name, preserving photo order within each album. Albums are
// returned sorted alphabetically by tag name. If two different names produce the
// same URL slug, the later one is suffixed (-2, -3, …) and a warning is logged,
// so album URLs stay unique.
func groupByTag(photos []Photo) []Album {
	byName := map[string][]Photo{}
	for _, p := range photos {
		for _, t := range p.Tags {
			byName[t.Name] = append(byName[t.Name], p)
		}
	}

	names := make([]string, 0, len(byName))
	for name := range byName {
		names = append(names, name)
	}
	sort.Strings(names)

	slugOwner := map[string]string{}
	albums := make([]Album, 0, len(names))
	for _, name := range names {
		slug := sanitiseSlug(name)
		if owner, taken := slugOwner[slug]; taken && owner != name {
			base := slug
			for n := 2; ; n++ {
				cand := base + "-" + strconv.Itoa(n)
				if _, t := slugOwner[cand]; !t {
					slug = cand
					break
				}
			}
			log.Printf("album slug collision: %q and %q both slug to %q; using %q for the latter",
				owner, name, base, slug)
		}
		slugOwner[slug] = name
		ps := byName[name]
		albums = append(albums, Album{
			Tag:    Tag{Name: name, Slug: slug},
			Count:  len(ps),
			Photos: ps,
		})
	}
	return albums
}

// baseData returns the profile-header and site-wide fields every page template
// expects, so the album templates stay in step with the others.
func (g *Generator) baseData() map[string]any {
	return map[string]any{
		"BaseURL":     g.baseURL,
		"Year":        time.Now().Year(),
		"Author":      g.author,
		"Handle":      g.handle,
		"Bio":         g.bio,
		"BioAlt":      g.bioAlt,
		"Initial":     g.initial(),
		"FontsURL":    g.fontsURL,
		"SerifFamily": g.serifFamily,
		"MlFamily":    g.mlFamily,
	}
}

// renderAlbumPages writes one paginated album per tag under public/album/<slug>/,
// a flat square grid like the grid view. total is the site-wide photo count, for
// the profile header.
func (g *Generator) renderAlbumPages(albums []Album, total int) error {
	for _, al := range albums {
		albumDir := filepath.Join(g.outputDir, "album", al.Tag.Slug)
		if err := os.MkdirAll(albumDir, 0755); err != nil {
			return err
		}
		base := "/album/" + al.Tag.Slug + "/"

		totalPages := (al.Count + g.pageSize - 1) / g.pageSize
		if totalPages == 0 {
			totalPages = 1
		}

		for i := 0; i < totalPages; i++ {
			start := i * g.pageSize
			end := start + g.pageSize
			if end > al.Count {
				end = al.Count
			}

			dst := filepath.Join(albumDir, "index.html")
			if i > 0 {
				dir := filepath.Join(albumDir, "page", strconv.Itoa(i+1))
				if err := os.MkdirAll(dir, 0755); err != nil {
					return err
				}
				dst = filepath.Join(dir, "index.html")
			}

			prev := ""
			next := ""
			switch i {
			case 0:
				// no prev
			case 1:
				prev = base
			default:
				prev = base + "page/" + strconv.Itoa(i) + "/"
			}
			if i+1 < totalPages {
				next = base + "page/" + strconv.Itoa(i+2) + "/"
			}

			data := g.baseData()
			data["Tag"] = al.Tag
			data["Count"] = al.Count
			data["Photos"] = al.Photos[start:end]
			data["Total"] = total
			data["Page"] = i + 1
			data["TotalPages"] = totalPages
			data["PrevURL"] = prev
			data["NextURL"] = next
			if err := g.render("album.html", dst, data); err != nil {
				return err
			}
		}
	}
	return nil
}

// renderAlbumsIndex writes public/albums/index.html — every tag with its count,
// linking to each album.
func (g *Generator) renderAlbumsIndex(albums []Album, total int) error {
	data := g.baseData()
	data["Albums"] = albums
	data["Total"] = total
	return g.render("albums.html", filepath.Join(g.outputDir, "albums", "index.html"), data)
}

type tagJSON struct {
	Tag   string `json:"tag"`
	Slug  string `json:"slug"`
	Count int    `json:"count"`
}

// renderTagsJSON writes public/tags.json — the machine-readable tag list, served
// statically like feed.xml.
func (g *Generator) renderTagsJSON(albums []Album) error {
	out := make([]tagJSON, 0, len(albums))
	for _, a := range albums {
		out = append(out, tagJSON{Tag: a.Tag.Name, Slug: a.Tag.Slug, Count: a.Count})
	}
	b, err := json.MarshalIndent(out, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(filepath.Join(g.outputDir, "tags.json"), b, 0644)
}