package api

import (
	"testing"
	"time"

	"github.com/jackc/pgx/v5/pgtype"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

// missingRow builds a ListMissingTracksRow with just the fields the grouping
// fold reads, so a test case states its directory and title and nothing else.
func missingRow(dir, title string, missingAt time.Time) dbq.ListMissingTracksRow {
	return dbq.ListMissingTracksRow{
		ID:           pgtype.UUID{Bytes: [16]byte{1}, Valid: true},
		Title:        title,
		FilePath:     dir + "/" + title + ".flac",
		Directory:    dir,
		MissingSince: pgtype.Timestamptz{Time: missingAt, Valid: true},
		DurationMs:   180_000,
		AlbumTitle:   "Album",
		ArtistName:   "Artist",
	}
}

func TestGroupMissingByDirectory(t *testing.T) {
	base := time.Date(2026, 8, 6, 12, 0, 0, 0, time.UTC)

	t.Run("consecutive rows in one directory collapse to one group", func(t *testing.T) {
		groups := groupMissingByDirectory([]dbq.ListMissingTracksRow{
			missingRow("/music/Linkin Park/Minutes to Midnight", "Given Up", base),
			missingRow("/music/Linkin Park/Minutes to Midnight", "Leave Out All the Rest", base),
			missingRow("/music/Linkin Park/Minutes to Midnight", "Bleed It Out", base),
		})

		if len(groups) != 1 {
			t.Fatalf("want 1 group, got %d", len(groups))
		}
		if got := len(groups[0].Tracks); got != 3 {
			t.Errorf("want 3 tracks in the group, got %d", got)
		}
		if groups[0].Directory != "/music/Linkin Park/Minutes to Midnight" {
			t.Errorf("unexpected directory %q", groups[0].Directory)
		}
	})

	t.Run("distinct directories stay separate and keep query order", func(t *testing.T) {
		groups := groupMissingByDirectory([]dbq.ListMissingTracksRow{
			missingRow("/music/A/One", "a1", base),
			missingRow("/music/B/Two", "b1", base),
			missingRow("/music/B/Two", "b2", base),
			missingRow("/music/C/Three", "c1", base),
		})

		if len(groups) != 3 {
			t.Fatalf("want 3 groups, got %d", len(groups))
		}
		wantDirs := []string{"/music/A/One", "/music/B/Two", "/music/C/Three"}
		for i, want := range wantDirs {
			if groups[i].Directory != want {
				t.Errorf("group %d: want %q, got %q", i, want, groups[i].Directory)
			}
		}
		if got := len(groups[1].Tracks); got != 2 {
			t.Errorf("middle group: want 2 tracks, got %d", got)
		}
	})

	// The fold is run-length, not a map, so a directory that appears in two
	// non-adjacent runs legitimately produces two groups. That can only happen
	// if the query's ORDER BY directory is dropped — pinning it here means such
	// a change fails a test instead of silently fragmenting the UI.
	t.Run("a directory split by a foreign row yields two groups", func(t *testing.T) {
		groups := groupMissingByDirectory([]dbq.ListMissingTracksRow{
			missingRow("/music/A", "a1", base),
			missingRow("/music/B", "b1", base),
			missingRow("/music/A", "a2", base),
		})

		if len(groups) != 3 {
			t.Fatalf("want 3 groups from an unordered input, got %d", len(groups))
		}
	})

	t.Run("no rows yields an empty, non-nil slice", func(t *testing.T) {
		groups := groupMissingByDirectory(nil)
		if groups == nil {
			t.Fatal("want a non-nil slice so the JSON encoder emits [] not null")
		}
		if len(groups) != 0 {
			t.Errorf("want 0 groups, got %d", len(groups))
		}
	})

	t.Run("a never-played track carries a null last_played_at", func(t *testing.T) {
		groups := groupMissingByDirectory([]dbq.ListMissingTracksRow{
			missingRow("/music/A", "a1", base),
		})

		if groups[0].Tracks[0].LastPlayedAt != nil {
			t.Errorf("want nil last_played_at, got %v", *groups[0].Tracks[0].LastPlayedAt)
		}
	})

	t.Run("a played track carries its timestamp", func(t *testing.T) {
		row := missingRow("/music/A", "a1", base)
		row.LastPlayedAt = pgtype.Timestamptz{Time: base.Add(-48 * time.Hour), Valid: true}

		groups := groupMissingByDirectory([]dbq.ListMissingTracksRow{row})

		got := groups[0].Tracks[0].LastPlayedAt
		if got == nil {
			t.Fatal("want a last_played_at, got nil")
		}
		if want := "2026-08-04T12:00:00Z"; *got != want {
			t.Errorf("want %q, got %q", want, *got)
		}
	})

	t.Run("duration is reported in seconds", func(t *testing.T) {
		groups := groupMissingByDirectory([]dbq.ListMissingTracksRow{
			missingRow("/music/A", "a1", base),
		})

		if got := groups[0].Tracks[0].DurationSec; got != 180 {
			t.Errorf("want 180s from 180000ms, got %d", got)
		}
	})
}