package notifier

import (
	"fmt"
	"sort"
	"strings"

	"naviwatcher/internal/scanner"
)

// FormatDigest renders newly-found missing releases into a human-readable
// Telegram message grouped by artist, with per-artist counts and a link to
// the Web UI dashboard. It is deterministic: artists are sorted by label and
// releases within an artist are sorted by title.
//
// artistNames maps an ArtistID to its human-readable display name. Names are
// optional: if an ID is absent from the map (or the map itself is nil), the
// raw ArtistID is used as the label so the digest remains informative.
func FormatDigest(missing []scanner.MissingRelease, uiBaseURL string, artistNames map[string]string) string {
	if len(missing) == 0 {
		return "NaviWatcher: no new missing releases found."
	}

	type entry struct {
		title string
	}
	byArtist := make(map[string][]entry)
	order := make([]string, 0)
	for _, r := range missing {
		if _, ok := byArtist[r.ArtistID]; !ok {
			order = append(order, r.ArtistID)
		}
		byArtist[r.ArtistID] = append(byArtist[r.ArtistID], entry{title: r.Title})
	}
	// Stable ordering by display label (name if known, else ID).
	sort.Slice(order, func(i, j int) bool {
		return artistLabel(order[i], artistNames) < artistLabel(order[j], artistNames)
	})

	var b strings.Builder
	fmt.Fprintf(&b, "NaviWatcher: %d new missing release(s) found:\n\n", len(missing))
	for _, artistID := range order {
		entries := byArtist[artistID]
		titles := make([]string, 0, len(entries))
		for _, e := range entries {
			titles = append(titles, e.title)
		}
		sort.Strings(titles)
		fmt.Fprintf(&b, "%s (%d):\n", artistLabel(artistID, artistNames), len(titles))
		for _, t := range titles {
			fmt.Fprintf(&b, "  - %s\n", t)
		}
		b.WriteString("\n")
	}
	if uiBaseURL != "" {
		fmt.Fprintf(&b, "View details: %s\n", strings.TrimRight(uiBaseURL, "/"))
	}
	return strings.TrimRight(b.String(), "\n")
}

// artistLabel returns the human-readable display name for an artist ID when
// available, otherwise the raw ID. A non-empty name takes precedence so
// operators see recognizable artist names rather than opaque internal IDs.
func artistLabel(artistID string, names map[string]string) string {
	if names != nil {
		if name, ok := names[artistID]; ok && name != "" {
			return name
		}
	}
	return artistID
}