package library

import (
	"context"
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/fsnotify/fsnotify"
)

func expectCall(t *testing.T, ch <-chan struct{}, what string) {
	t.Helper()
	select {
	case <-ch:
	case <-time.After(3 * time.Second):
		t.Fatalf("no onChange after %s", what)
	}
}

func TestWatchDebouncesAndFollowsNewDirs(t *testing.T) {
	root := writeTree(t, map[string]string{"tokyo/a.jpg": "x"})
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	calls := make(chan struct{}, 10)
	if err := Watch(ctx, root, 100*time.Millisecond, func() { calls <- struct{}{} }); err != nil {
		t.Fatal(err)
	}

	for _, n := range []string{"b.jpg", "c.jpg", "d.jpg"} {
		os.WriteFile(filepath.Join(root, "tokyo", n), []byte("x"), 0o644)
	}
	expectCall(t, calls, "writes in existing album")
	select {
	case <-calls:
		t.Fatal("burst of writes produced more than one call")
	case <-time.After(300 * time.Millisecond):
	}

	os.Mkdir(filepath.Join(root, "iceland"), 0o755)
	expectCall(t, calls, "new album dir")
	time.Sleep(150 * time.Millisecond) // let the watcher add the new dir
	os.WriteFile(filepath.Join(root, "iceland", "a.jpg"), []byte("x"), 0o644)
	expectCall(t, calls, "write in new album")
}

func TestWatchLoopOverflowTriggersRescan(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	events := make(chan fsnotify.Event)
	errs := make(chan error)
	calls := make(chan struct{}, 1)
	go watchLoop(ctx, events, errs, func(string) error { return nil }, 50*time.Millisecond, func() { calls <- struct{}{} })

	errs <- fsnotify.ErrEventOverflow
	expectCall(t, calls, "event overflow")
}