package store

import (
	"context"
	"fmt"
	"os"
	"sync"
	"testing"
	"time"

	"github.com/google/uuid"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// TestEtcdStore tests the basic operations of the EtcdStore implementation
// This is an integration test that requires starting an embedded etcd server
func TestEtcdStore(t *testing.T) {
	// Create a temporary directory for etcd data
	tempDir, err := os.MkdirTemp("", "etcd-test-*")
	require.NoError(t, err)
	defer os.RemoveAll(tempDir)

	// Configure and start embedded etcd
	etcdConfig := EtcdEmbedConfig{
		Name:           "test-node",
		DataDir:        tempDir,
		ClientURLs:     []string{"http://localhost:0"}, // Use port 0 to get a random available port
		PeerURLs:       []string{"http://localhost:0"},
	}

	etcdServer, err := StartEmbeddedEtcd(etcdConfig)
	require.NoError(t, err)
	
	// Use a cleanup function instead of defer to avoid double-close
	var once sync.Once
	t.Cleanup(func() {
		once.Do(func() {
			if etcdServer != nil {
				// Wrap in a recover to handle potential "close of closed channel" panic
				func() {
					defer func() {
						if r := recover(); r != nil {
							// Log the panic but continue - the server was likely already closed
							t.Logf("Recovered from panic while closing etcd server: %v", r)
						}
					}()
					etcdServer.Close()
				}()
			}
		})
	})

	// Get the actual client URL that was assigned
	clientURL := etcdServer.Clients[0].Addr().String()

	// Create the store
	store, err := NewEtcdStore([]string{clientURL}, etcdServer)
	require.NoError(t, err)
	defer store.Close()

	// Test context with timeout
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	// Test Put and Get
	t.Run("PutAndGet", func(t *testing.T) {
		key := "/test/key1"
		value := []byte("test-value-1")

		err := store.Put(ctx, key, value)
		require.NoError(t, err)

		kv, err := store.Get(ctx, key)
		require.NoError(t, err)
		assert.Equal(t, key, kv.Key)
		assert.Equal(t, value, kv.Value)
		assert.Greater(t, kv.Version, int64(0))
	})

	// Test List
	t.Run("List", func(t *testing.T) {
		// Put multiple keys with same prefix
		prefix := "/test/list/"
		for i := 0; i < 3; i++ {
			key := fmt.Sprintf("%s%d", prefix, i)
			value := []byte(fmt.Sprintf("value-%d", i))
			err := store.Put(ctx, key, value)
			require.NoError(t, err)
		}

		// List keys with prefix
		kvs, err := store.List(ctx, prefix)
		require.NoError(t, err)
		assert.Len(t, kvs, 3)

		// Verify each key starts with prefix
		for _, kv := range kvs {
			assert.True(t, len(kv.Key) > len(prefix))
			assert.Equal(t, prefix, kv.Key[:len(prefix)])
		}
	})

	// Test Delete
	t.Run("Delete", func(t *testing.T) {
		key := "/test/delete-key"
		value := []byte("delete-me")

		// Put a key
		err := store.Put(ctx, key, value)
		require.NoError(t, err)

		// Verify it exists
		_, err = store.Get(ctx, key)
		require.NoError(t, err)

		// Delete it
		err = store.Delete(ctx, key)
		require.NoError(t, err)

		// Verify it's gone
		_, err = store.Get(ctx, key)
		require.Error(t, err)
	})

	// Test Watch
	t.Run("Watch", func(t *testing.T) {
		prefix := "/test/watch/"
		key := prefix + "key1"

		// Start watching before any changes
		watchCh, err := store.Watch(ctx, prefix, 0)
		require.NoError(t, err)

		// Make changes in a goroutine
		go func() {
			time.Sleep(100 * time.Millisecond)
			store.Put(ctx, key, []byte("watch-value-1"))
			time.Sleep(100 * time.Millisecond)
			store.Put(ctx, key, []byte("watch-value-2"))
			time.Sleep(100 * time.Millisecond)
			store.Delete(ctx, key)
		}()

		// Collect events
		var events []WatchEvent
		timeout := time.After(2 * time.Second)

	eventLoop:
		for {
			select {
			case event, ok := <-watchCh:
				if !ok {
					break eventLoop
				}
				events = append(events, event)
				if len(events) >= 3 {
					break eventLoop
				}
			case <-timeout:
				t.Fatal("Timed out waiting for watch events")
				break eventLoop
			}
		}

		// Verify events
		require.Len(t, events, 3)

		// First event: Put watch-value-1
		assert.Equal(t, EventTypePut, events[0].Type)
		assert.Equal(t, key, events[0].KV.Key)
		assert.Equal(t, []byte("watch-value-1"), events[0].KV.Value)

		// Second event: Put watch-value-2
		assert.Equal(t, EventTypePut, events[1].Type)
		assert.Equal(t, key, events[1].KV.Key)
		assert.Equal(t, []byte("watch-value-2"), events[1].KV.Value)

		// Third event: Delete
		assert.Equal(t, EventTypeDelete, events[2].Type)
		assert.Equal(t, key, events[2].KV.Key)
	})

	// Test DoTransaction
	t.Run("DoTransaction", func(t *testing.T) {
		key1 := "/test/txn/key1"
		key2 := "/test/txn/key2"

		// Put key1 first
		err := store.Put(ctx, key1, []byte("txn-value-1"))
		require.NoError(t, err)

		// Get key1 to get its version
		kv, err := store.Get(ctx, key1)
		require.NoError(t, err)
		version := kv.Version

		// Transaction: If key1 has expected version, put key2
		checks := []Compare{
			{Key: key1, ExpectedVersion: version},
		}
		onSuccess := []Op{
			{Type: OpPut, Key: key2, Value: []byte("txn-value-2")},
		}
		onFailure := []Op{} // Empty for this test

		committed, err := store.DoTransaction(ctx, checks, onSuccess, onFailure)
		require.NoError(t, err)
		assert.True(t, committed)

		// Verify key2 was created
		kv2, err := store.Get(ctx, key2)
		require.NoError(t, err)
		assert.Equal(t, []byte("txn-value-2"), kv2.Value)

		// Now try a transaction that should fail
		checks = []Compare{
			{Key: key1, ExpectedVersion: version + 100}, // Wrong version
		}
		committed, err = store.DoTransaction(ctx, checks, onSuccess, onFailure)
		require.NoError(t, err)
		assert.False(t, committed)
	})
}

// TestLeaderElection tests the Campaign, Resign, and GetLeader methods
func TestLeaderElection(t *testing.T) {
	// Create a temporary directory for etcd data
	tempDir, err := os.MkdirTemp("", "etcd-election-test-*")
	require.NoError(t, err)
	defer os.RemoveAll(tempDir)

	// Configure and start embedded etcd
	etcdConfig := EtcdEmbedConfig{
		Name:           "election-test-node",
		DataDir:        tempDir,
		ClientURLs:     []string{"http://localhost:0"},
		PeerURLs:       []string{"http://localhost:0"},
	}

	etcdServer, err := StartEmbeddedEtcd(etcdConfig)
	require.NoError(t, err)
	
	// Use a cleanup function instead of defer to avoid double-close
	var once sync.Once
	t.Cleanup(func() {
		once.Do(func() {
			if etcdServer != nil {
				// Wrap in a recover to handle potential "close of closed channel" panic
				func() {
					defer func() {
						if r := recover(); r != nil {
							// Log the panic but continue - the server was likely already closed
							t.Logf("Recovered from panic while closing etcd server: %v", r)
						}
					}()
					etcdServer.Close()
				}()
			}
		})
	})

	// Get the actual client URL that was assigned
	clientURL := etcdServer.Clients[0].Addr().String()

	// Create the store
	store, err := NewEtcdStore([]string{clientURL}, etcdServer)
	require.NoError(t, err)
	defer store.Close()

	// Test context with timeout
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	// Test Campaign and GetLeader
	t.Run("CampaignAndGetLeader", func(t *testing.T) {
		leaderID := "test-leader-" + uuid.New().String()[:8]

		// Campaign for leadership
		leadershipCtx, err := store.Campaign(ctx, leaderID, 5)
		require.NoError(t, err)
		require.NotNil(t, leadershipCtx)

		// Wait a moment for leadership to be established
		time.Sleep(100 * time.Millisecond)

		// Verify we are the leader
		currentLeader, err := store.GetLeader(ctx)
		require.NoError(t, err)
		assert.Equal(t, leaderID, currentLeader)

		// Resign leadership
		err = store.Resign(ctx)
		require.NoError(t, err)

		// Wait a moment for resignation to take effect
		time.Sleep(500 * time.Millisecond)

		// Verify leadership context is cancelled
		select {
		case <-leadershipCtx.Done():
			// Expected
		default:
			t.Fatal("Leadership context should be cancelled after resign")
		}

		// Verify no leader or different leader
		currentLeader, err = store.GetLeader(ctx)
		require.NoError(t, err)
		assert.NotEqual(t, leaderID, currentLeader, "Should not still be leader after resigning")
	})

	// Test multiple candidates
	t.Run("MultipleLeaderCandidates", func(t *testing.T) {
		// Create a second store client
		store2, err := NewEtcdStore([]string{clientURL}, nil) // No embedded server for this one
		require.NoError(t, err)
		defer store2.Close()

		leaderID1 := "leader1-" + uuid.New().String()[:8]
		leaderID2 := "leader2-" + uuid.New().String()[:8]

		// First store campaigns
		leadershipCtx1, err := store.Campaign(ctx, leaderID1, 5)
		require.NoError(t, err)

		// Wait a moment for leadership to be established
		time.Sleep(100 * time.Millisecond)

		// Verify first store is leader
		currentLeader, err := store.GetLeader(ctx)
		require.NoError(t, err)
		assert.Equal(t, leaderID1, currentLeader)

		// Second store campaigns but shouldn't become leader yet
		leadershipCtx2, err := store2.Campaign(ctx, leaderID2, 5)
		require.NoError(t, err)

		// Wait a moment to ensure leadership state is stable
		time.Sleep(100 * time.Millisecond)

		// Verify first store is still leader
		currentLeader, err = store.GetLeader(ctx)
		require.NoError(t, err)
		assert.Equal(t, leaderID1, currentLeader)

		// First store resigns
		err = store.Resign(ctx)
		require.NoError(t, err)

		// Wait for second store to become leader
		deadline := time.Now().Add(3 * time.Second)
		var leaderFound bool
		for time.Now().Before(deadline) {
			currentLeader, err = store2.GetLeader(ctx)
			if err == nil && currentLeader == leaderID2 {
				leaderFound = true
				break
			}
			time.Sleep(100 * time.Millisecond)
		}

		// Verify second store is now leader
		assert.True(t, leaderFound, "Second candidate should have become leader")
		assert.Equal(t, leaderID2, currentLeader)

		// Verify first leadership context is cancelled
		select {
		case <-leadershipCtx1.Done():
			// Expected
		default:
			t.Fatal("First leadership context should be cancelled after resign")
		}

		// Second store resigns
		err = store2.Resign(ctx)
		require.NoError(t, err)

		// Verify second leadership context is cancelled
		select {
		case <-leadershipCtx2.Done():
			// Expected
		default:
			t.Fatal("Second leadership context should be cancelled after resign")
		}
	})
}

// TestEtcdStoreWithMockEmbeddedEtcd tests the EtcdStore with a mock embedded etcd
// This is a unit test that doesn't require starting a real etcd server
func TestEtcdStoreWithMockEmbeddedEtcd(t *testing.T) {
	// This test would use mocks to test the EtcdStore without starting a real etcd server
	// For brevity, we'll skip the implementation of this test
	t.Skip("Mock-based unit test not implemented")
}