package tests

import (
	"context"
	"fmt"
	"net/http/httptest"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/alicebob/miniredis/v2"
	"github.com/gorilla/websocket"
	"github.com/jfraeys/fetch_ml/internal/api"
	"github.com/jfraeys/fetch_ml/internal/auth"
	"github.com/jfraeys/fetch_ml/internal/experiment"
	"github.com/jfraeys/fetch_ml/internal/logging"
	"github.com/jfraeys/fetch_ml/internal/queue"
	"github.com/stretchr/testify/require"
)

func TestWebSocketQueueEndToEnd(t *testing.T) {
	if testing.Short() {
		t.Skip("skipping websocket queue integration in short mode")
	}

	// Miniredis provides an in-memory Redis compatible server for realistic queue tests.
	redisServer, err := miniredis.Run()
	require.NoError(t, err)
	defer redisServer.Close()

	taskQueue, err := queue.NewTaskQueue(queue.Config{
		RedisAddr:            redisServer.Addr(),
		MetricsFlushInterval: 10 * time.Millisecond,
	})
	require.NoError(t, err)
	defer func() { _ = taskQueue.Close() }()

	expMgr := experiment.NewManager(t.TempDir())
	require.NoError(t, expMgr.Initialize())

	logger := logging.NewLogger(0, false)
	authCfg := &auth.Config{Enabled: false}
	wsHandler := api.NewWSHandler(authCfg, logger, expMgr, taskQueue)
	server := httptest.NewServer(wsHandler)
	defer server.Close()

	ctx, cancelWorkers := context.WithCancel(context.Background())
	defer cancelWorkers()

	const (
		jobCount          = 20
		workerCount       = 4
		clientConcurrency = 8
	)

	doneCh := make(chan string, jobCount)
	var workerWG sync.WaitGroup
	startFakeWorkers(ctx, t, &workerWG, taskQueue, workerCount, doneCh)

	// Submit jobs concurrently through the real WebSocket protocol.
	var submitWG sync.WaitGroup
	sem := make(chan struct{}, clientConcurrency)
	for i := 0; i < jobCount; i++ {
		submitWG.Add(1)
		go func(idx int) {
			sem <- struct{}{}
			defer submitWG.Done()
			defer func() { <-sem }()
			jobName := fmt.Sprintf("ws-load-job-%02d", idx)
			commitID := fmt.Sprintf("%064x", idx+1)
			queueJobViaWebSocket(t, server.URL, jobName, commitID, byte(idx%5))
		}(i)
	}
	submitWG.Wait()

	completed := 0
	timeout := time.After(30 * time.Second)
	for completed < jobCount {
		select {
		case <-timeout:
			t.Fatalf("timed out waiting for %d completions, only saw %d", jobCount, completed)
		case <-doneCh:
			completed++
		}
	}

	// Stop workers and ensure they exit cleanly.
	cancelWorkers()
	workerWG.Wait()

	nextTask, err := taskQueue.GetNextTask()
	require.NoError(t, err)
	require.Nil(t, nextTask, "queue should be empty after all jobs complete")
}

func startFakeWorkers(
	ctx context.Context,
	t *testing.T,
	wg *sync.WaitGroup,
	taskQueue *queue.TaskQueue,
	workerCount int,
	doneCh chan<- string,
) {
	for w := 0; w < workerCount; w++ {
		wg.Add(1)
		go func(workerID string) {
			defer wg.Done()
			for {
				select {
				case <-ctx.Done():
					return
				default:
				}

				task, err := taskQueue.GetNextTaskWithLease(workerID, 30*time.Second)
				if err != nil {
					t.Logf("worker %s queue error: %v", workerID, err)
					time.Sleep(5 * time.Millisecond)
					continue
				}
				if task == nil {
					time.Sleep(5 * time.Millisecond)
					continue
				}

				started := time.Now()
				completed := started.Add(10 * time.Millisecond)

				task.Status = statusCompleted
				task.StartedAt = &started
				task.EndedAt = &completed
				task.LeaseExpiry = nil
				task.LeasedBy = ""

				if err := taskQueue.UpdateTask(task); err != nil {
					t.Logf("worker %s failed to update task %s: %v", workerID, task.ID, err)
					continue
				}

				doneCh <- task.JobName
			}
		}(fmt.Sprintf("worker-%d", w))
	}
}

func queueJobViaWebSocket(t *testing.T, baseURL, jobName, commitID string, priority byte) {
	t.Helper()

	wsURL := "ws" + strings.TrimPrefix(baseURL, "http")
	conn, resp, err := websocket.DefaultDialer.Dial(wsURL, nil)
	if resp != nil && resp.Body != nil {
		defer func() {
			if err := resp.Body.Close(); err != nil {
				t.Logf("Warning: failed to close response body: %v", err)
			}
		}()
	}
	require.NoError(t, err)
	defer func() { _ = conn.Close() }()

	msg := buildQueueJobMessage(jobName, commitID, priority)
	require.NoError(t, conn.WriteMessage(websocket.BinaryMessage, msg))

	_, payload, err := conn.ReadMessage()
	require.NoError(t, err)
	require.NotEmpty(t, payload, "expected response payload")
	require.EqualValues(t, api.PacketTypeSuccess, payload[0], "queue job should return success packet")
}

func buildQueueJobMessage(jobName, commitID string, priority byte) []byte {
	jobBytes := []byte(jobName)
	if len(jobBytes) > 255 {
		jobBytes = jobBytes[:255]
	}

	if len(commitID) < 64 {
		commitID += strings.Repeat("a", 64-len(commitID))
	}

	buf := make([]byte, 0, 1+64+64+1+1+len(jobBytes))
	buf = append(buf, api.OpcodeQueueJob)
	buf = append(buf, []byte(strings.Repeat("0", 64))...)
	buf = append(buf, []byte(commitID[:64])...)
	buf = append(buf, priority)
	buf = append(buf, byte(len(jobBytes)))
	buf = append(buf, jobBytes...)
	return buf
}