package db

import (
	"path"
	"sync"
	"testing"
)

// TestKVInc tests that the KVInc function behaves correctly under concurrent access
func TestKVInc(t *testing.T) {
	posternDB, err := OpenDB(&Config{
		DBPath: path.Join(t.TempDir(), "meta.db"),
	})
	if err != nil {
		t.Fatal(err)
	}

	defer func(posternDB *DB) {
		err := posternDB.Close()
		if err != nil {
			t.Fatal(err)
		}
	}(posternDB)

	key := "test-concurrency-key"
	if err := posternDB.KVSet(t.Context(), key, 0); err != nil {
		t.Fatalf("KVSet setup failed: %v", err)
	}

	const numGoroutines = 50
	const incsPerGoroutine = 200

	var wg sync.WaitGroup
	wg.Add(numGoroutines)

	for range numGoroutines {
		go func(db *DB) {
			defer wg.Done()
			for range incsPerGoroutine {
				_, err := db.KVInc(t.Context(), key, 1)
				if err != nil {
					t.Errorf("KVInc failed during execution: %v", err)
					return
				}
			}
		}(posternDB)
	}

	wg.Wait()

	// Retrieve the final count
	val, err := posternDB.KVGet(t.Context(), key)
	if err != nil {
		t.Fatalf("KVGet failed to fetch final value: %v", err)
	}

	got, ok := val.(int64)
	if !ok {
		t.Fatalf("KVGet returned unexpected type: %T, expected int", val)
	}

	// Catch race conditions
	expected := int64(numGoroutines * incsPerGoroutine)
	if got != expected {
		t.Errorf("Race condition detected! Expected final value %d, got %d", expected, got)
	}

	// Check return value of next increment
	res, err := posternDB.KVInc(t.Context(), key, 1)
	if err != nil {
		t.Errorf("KVInc failed during execution: %v", err)
		return
	}

	if res != expected+1 {
		t.Errorf("Incrementation mismatch! Expected final value %d, got %d", expected+1, res)
	}
}

// TestKVList tests that the KVList function returns all stored key value pairs
func TestKVList(t *testing.T) {
	posternDB, err := OpenDB(&Config{
		DBPath: path.Join(t.TempDir(), "meta.db"),
	})
	if err != nil {
		t.Fatal(err)
	}

	defer func(posternDB *DB) {
		err := posternDB.Close()
		if err != nil {
			t.Fatal(err)
		}
	}(posternDB)

	want := map[string]any{
		"key-1": "value-1",
		"key-2": int64(42),
	}

	for key, val := range want {
		if err := posternDB.KVSet(t.Context(), key, val); err != nil {
			t.Fatalf("KVSet setup failed: %v", err)
		}
	}

	got, err := posternDB.KVList(t.Context())
	if err != nil {
		t.Fatalf("KVList failed: %v", err)
	}

	if len(got) != len(want) {
		t.Fatalf("Expected %d pairs, got %d", len(want), len(got))
	}

	for key, expected := range want {
		val, ok := got[key]
		if !ok {
			t.Errorf("Missing key %q in KVList result", key)
			continue
		}
		if val != expected {
			t.Errorf("Key %q: expected value %v, got %v", key, expected, val)
		}
	}
}

// TestKVIncString tests that the KVInc function does not increment invalid values
func TestKVIncString(t *testing.T) {
	posternDB, err := OpenDB(&Config{
		DBPath: path.Join(t.TempDir(), "meta.db"),
	})
	if err != nil {
		t.Fatal(err)
	}

	defer func(posternDB *DB) {
		err := posternDB.Close()
		if err != nil {
			t.Fatal(err)
		}
	}(posternDB)

	key := "test-key"
	if err := posternDB.KVSet(t.Context(), key, "value"); err != nil {
		t.Fatalf("KVSet setup failed: %v", err)
	}

	_, err = posternDB.KVInc(t.Context(), key, 1)
	if err == nil {
		t.Fatalf("KVInc should have failed during execution due to attempt incrementing a non-integer value")
	}
}

// TestKVDelete tests the KVDelete function
func TestKVDelete(t *testing.T) {
	posternDB, err := OpenDB(&Config{
		DBPath: path.Join(t.TempDir(), "meta.db"),
	})
	if err != nil {
		t.Fatal(err)
	}

	defer func(posternDB *DB) {
		err := posternDB.Close()
		if err != nil {
			t.Fatal(err)
		}
	}(posternDB)

	key := "test-key"
	var testVal int64 = 42
	if err := posternDB.KVSet(t.Context(), key, testVal); err != nil {
		t.Fatalf("KVSet setup failed: %v", err)
	}

	val, err := posternDB.KVPop(t.Context(), key)
	if err != nil {
		t.Fatalf("KVGet failed to fetch final value: %v", err)
	}
	if val != testVal {
		t.Errorf("Expected value %d, got %d", testVal, val)
	}

	_, err = posternDB.KVPop(t.Context(), key)
	if err == nil {
		t.Fatalf("KVDelete should have failed during execution due to missing key")
	}
}