package idempotency

import (
	"os"
	"path/filepath"
	"sync"
	"testing"
)

func TestPutGet(t *testing.T) {
	s, err := Open(filepath.Join(t.TempDir(), "idem.log"))
	if err != nil {
		t.Fatal(err)
	}
	defer s.Close()

	if _, ok := s.Get("a"); ok {
		t.Fatal("unexpected hit on empty store")
	}
	if err := s.Put("a", 42); err != nil {
		t.Fatal(err)
	}
	if id, ok := s.Get("a"); !ok || id != 42 {
		t.Fatalf("Get(a) = %d,%v; want 42,true", id, ok)
	}
}

func TestFirstWriterWins(t *testing.T) {
	s, _ := Open(filepath.Join(t.TempDir(), "idem.log"))
	defer s.Close()
	_ = s.Put("a", 1)
	_ = s.Put("a", 2) // ignored
	if id, _ := s.Get("a"); id != 1 {
		t.Fatalf("got %d, want first value 1", id)
	}
}

func TestDurableAcrossReopen(t *testing.T) {
	path := filepath.Join(t.TempDir(), "idem.log")
	s, _ := Open(path)
	_ = s.Put("checkout-x", 1001)
	_ = s.Put("checkout-y", 1002)
	_ = s.Close()

	// A fresh process (the restart case the in-memory map failed) must still see
	// the recorded keys — this is the duplicate-order bug the durable store fixes.
	s2, err := Open(path)
	if err != nil {
		t.Fatal(err)
	}
	defer s2.Close()
	if id, ok := s2.Get("checkout-x"); !ok || id != 1001 {
		t.Fatalf("after reopen Get(checkout-x) = %d,%v; want 1001,true", id, ok)
	}
	if id, ok := s2.Get("checkout-y"); !ok || id != 1002 {
		t.Fatalf("after reopen Get(checkout-y) = %d,%v; want 1002,true", id, ok)
	}
}

func TestCorruptTrailingLineSkipped(t *testing.T) {
	path := filepath.Join(t.TempDir(), "idem.log")
	s, _ := Open(path)
	_ = s.Put("good", 7)
	_ = s.Close()

	// Simulate a torn write from a crash mid-append.
	f, _ := os.OpenFile(path, os.O_APPEND|os.O_WRONLY, 0o644)
	_, _ = f.WriteString(`{"k":"bad","id":`)
	_ = f.Close()

	s2, err := Open(path)
	if err != nil {
		t.Fatalf("open with corrupt tail: %v", err)
	}
	defer s2.Close()
	if id, ok := s2.Get("good"); !ok || id != 7 {
		t.Fatalf("good key lost after corrupt tail: %d,%v", id, ok)
	}
	if _, ok := s2.Get("bad"); ok {
		t.Fatal("corrupt line should not have loaded")
	}
}

func TestLockSerialisesKey(t *testing.T) {
	s, _ := Open(filepath.Join(t.TempDir(), "idem.log"))
	defer s.Close()

	// Two goroutines contend on the same key; the lock must serialise the
	// check→create→record so exactly one writes and both agree on the value.
	var wg sync.WaitGroup
	for i := 0; i < 2; i++ {
		wg.Add(1)
		go func(v uint64) {
			defer wg.Done()
			unlock := s.Lock("k")
			defer unlock()
			if _, ok := s.Get("k"); !ok {
				_ = s.Put("k", v)
			}
		}(uint64(i + 1))
	}
	wg.Wait()
	if _, ok := s.Get("k"); !ok {
		t.Fatal("expected a value recorded under contention")
	}
}