package flock

import (
	"errors"
	"os"
	"testing"
	"time"
)

func TestLock_basic(t *testing.T) {
	const path = "/tmp/fsutil-test-lock"

	f, err := Lock(path)
	if err != nil {
		t.Fatal(err)
	}

	// locked is closed once the goroutine acquires the lock.
	locked := make(chan struct{})
	go func() {
		f2, err := Lock(path) // blocks until f is unlocked
		if err != nil {
			t.Error(err)
			return
		}
		close(locked)
		Unlock(f2)
	}()

	// Goroutine should be blocked while we hold the lock.
	select {
	case <-locked:
		t.Fatal("goroutine acquired lock while we hold it")
	case <-time.After(50 * time.Millisecond):
	}

	Unlock(f)

	// Now the goroutine should unblock and acquire the lock.
	select {
	case <-locked:
	case <-time.After(time.Second):
		t.Fatal("goroutine never acquired lock after release")
	}
}

func TestLock_badPath(t *testing.T) {
	_, err := Lock("./dne/file.lock")
	if err == nil {
		t.Fatal("expected error for bad path")
	}
}

func TestTryLock(t *testing.T) {
	const path = "/tmp/fsutil-test-lock"

	f, err := TryLock(path)
	if err != nil {
		t.Fatal(err)
	}
	defer Unlock(f)

	// While f holds the lock, TryLock should return ErrLocked.
	_, err = TryLock(path)
	if !errors.Is(err, ErrLocked) {
		t.Fatalf("expected ErrLocked, got %v", err)
	}

	// After unlocking, TryLock should succeed.
	if err := Unlock(f); err != nil {
		t.Fatal(err)
	}

	f2, err := TryLock(path)
	if err != nil {
		t.Fatalf("expected lock after unlock, got %v", err)
	}
	Unlock(f2)
}

func TestTryLockFile(t *testing.T) {
	const path = "/tmp/fsutil-test-lockfile"

	f, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()

	if err := TryLockFile(f); err != nil {
		t.Fatal(err)
	}

	f2, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		t.Fatal(err)
	}
	defer f2.Close()

	if err := TryLockFile(f2); !errors.Is(err, ErrLocked) {
		t.Fatalf("expected ErrLocked, got %v", err)
	}

	if err := Unlock(f); err != nil {
		t.Fatal(err)
	}

	if err := TryLockFile(f2); err != nil {
		t.Fatalf("expected lock after unlock, got %v", err)
	}
}