package docker

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"regexp"
	"strings"
	"time"

	"github.com/docker/docker/api/types/container"
	"github.com/docker/docker/api/types/image"
	"github.com/docker/docker/client"
	"github.com/google/uuid"
	"go.uber.org/zap"

	"github.com/RyanCopley/skybridge/faas/internal/domain"
	"github.com/RyanCopley/skybridge/faas/internal/runtime"
)

type SimpleDockerRuntime struct {
	logger *zap.Logger
	client *client.Client
}

func NewSimpleDockerRuntime(logger *zap.Logger) (*SimpleDockerRuntime, error) {
	var cli *client.Client
	var err error
	
	// Try different socket paths with ping test
	socketPaths := []string{
		"unix:///run/user/1000/podman/podman.sock", // Podman socket (mounted from host)
		"unix:///var/run/docker.sock",              // Standard Docker socket
	}
	
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	
	for _, socketPath := range socketPaths {
		logger.Info("Attempting to connect to socket", zap.String("path", socketPath))
		
		cli, err = client.NewClientWithOpts(
			client.WithHost(socketPath),
			client.WithAPIVersionNegotiation(),
		)
		if err != nil {
			logger.Warn("Failed to create client", zap.String("path", socketPath), zap.Error(err))
			continue
		}

		// Test connection
		if _, err := cli.Ping(ctx); err != nil {
			logger.Warn("Failed to ping daemon", zap.String("path", socketPath), zap.Error(err))
			continue
		}
		
		logger.Info("Successfully connected to Docker/Podman", zap.String("path", socketPath))
		break
	}
	
	// Final fallback to environment
	if cli == nil {
		logger.Info("Trying default Docker environment")
		cli, err = client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
		if err != nil {
			return nil, fmt.Errorf("failed to create Docker client: %w", err)
		}
		
		if _, err := cli.Ping(ctx); err != nil {
			return nil, fmt.Errorf("failed to ping Docker/Podman daemon: %w", err)
		}
	}
	
	if cli == nil {
		return nil, fmt.Errorf("no working Docker/Podman socket found")
	}

	return &SimpleDockerRuntime{
		logger: logger,
		client: cli,
	}, nil
}

func (s *SimpleDockerRuntime) Execute(ctx context.Context, function *domain.FunctionDefinition, input json.RawMessage) (*domain.ExecutionResult, error) {
	startTime := time.Now()

	// Create container
	containerID, err := s.createContainer(ctx, function, input)
	if err != nil {
		return nil, fmt.Errorf("failed to create container: %w", err)
	}

	// Start container
	if err := s.client.ContainerStart(ctx, containerID, container.StartOptions{}); err != nil {
		s.cleanupContainer(ctx, containerID)
		return nil, fmt.Errorf("failed to start container: %w", err)
	}

	// Create timeout context based on function timeout
	var timeoutCtx context.Context
	var cancel context.CancelFunc
	if function.Timeout.Duration > 0 {
		timeoutCtx, cancel = context.WithTimeout(ctx, function.Timeout.Duration)
		defer cancel()
	} else {
		timeoutCtx = ctx
	}


	// Wait for container to finish with timeout
	statusCh, errCh := s.client.ContainerWait(timeoutCtx, containerID, container.WaitConditionNotRunning)
	
	var timedOut bool
	select {
	case err := <-errCh:
		s.cleanupContainer(ctx, containerID)
		return nil, fmt.Errorf("error waiting for container: %w", err)
	case <-statusCh:
		// Container finished normally
	case <-timeoutCtx.Done():
		// Timeout occurred
		timedOut = true
		
		// Stop the container in the background - don't wait for it to complete
		go func() {
			// Use a very short timeout for stopping, then kill if needed
			if err := s.client.ContainerStop(context.Background(), containerID, container.StopOptions{
				Timeout: &[]int{1}[0], // Only 1 second grace period for stop
			}); err != nil {
				s.logger.Warn("Failed to stop timed out container gracefully, attempting to kill", 
					zap.String("container_id", containerID),
					zap.Error(err))
				// If stop fails, try to kill it immediately
				if killErr := s.client.ContainerKill(context.Background(), containerID, "SIGKILL"); killErr != nil {
					s.logger.Error("Failed to kill timed out container", 
						zap.String("container_id", containerID),
						zap.Error(killErr))
				}
			}
		}()
	}

	var logs []string
	var stats *container.InspectResponse
	
	// For timed-out containers, skip log retrieval and inspection to return quickly
	if timedOut {
		logs = []string{"Container execution timed out"}
	} else {
		// Get container logs
		var err error
		logs, err = s.getContainerLogs(ctx, containerID)
		if err != nil {
			s.logger.Warn("Failed to get container logs", zap.Error(err))
			logs = []string{"Failed to retrieve logs"}
		}

		// Get container stats
		statsResponse, err := s.client.ContainerInspect(ctx, containerID)
		if err != nil {
			s.logger.Warn("Failed to inspect container", zap.Error(err))
		} else {
			stats = &statsResponse
		}
	}

	// Get execution result
	result := &domain.ExecutionResult{
		Logs:     logs,
		Duration: time.Since(startTime).Truncate(time.Millisecond),
	}

	// Handle timeout case
	if timedOut {
		result.Error = fmt.Sprintf("Function execution timed out after %v", function.Timeout.Duration)
		result.Output = json.RawMessage(`{"error": "Function execution timed out"}`)
	} else {
		// Try to get output from container for successful executions
		if stats.State != nil {
			if stats.State.ExitCode == 0 {
				// Try to get output from container
				output, err := s.getContainerOutput(ctx, containerID)
				if err != nil {
					s.logger.Warn("Failed to get container output", zap.Error(err))
					result.Output = json.RawMessage(`{"error": "Failed to retrieve output"}`)
				} else {
					result.Output = output
				}
			} else {
				result.Error = fmt.Sprintf("Container exited with code %d", stats.State.ExitCode)
				result.Output = json.RawMessage(`{"error": "Container execution failed"}`)
			}
		} else {
			s.logger.Warn("Container state not available")
		}
	}

	// Cleanup container - for timed-out containers, do this in background
	if timedOut {
		go func() {
			s.cleanupContainer(context.Background(), containerID)
		}()
	} else {
		s.cleanupContainer(ctx, containerID)
	}

	return result, nil
}

func (s *SimpleDockerRuntime) Deploy(ctx context.Context, function *domain.FunctionDefinition) error {
	s.logger.Info("Deploying function image",
		zap.String("function_id", function.ID.String()),
		zap.String("image", function.Image))

	// Pull the image if it doesn't exist
	_, _, err := s.client.ImageInspectWithRaw(ctx, function.Image)
	if err != nil {
		// Image doesn't exist, try to pull it
		s.logger.Info("Pulling image", zap.String("image", function.Image))
		reader, err := s.client.ImagePull(ctx, function.Image, image.PullOptions{})
		if err != nil {
			return fmt.Errorf("failed to pull image %s: %w", function.Image, err)
		}
		defer reader.Close()

		// Wait for pull to complete (we could parse the output but for now we'll just wait)
		buf := make([]byte, 1024)
		for {
			_, err := reader.Read(buf)
			if err != nil {
				break
			}
		}
	}

	return nil
}

func (s *SimpleDockerRuntime) Remove(ctx context.Context, functionID uuid.UUID) error {
	s.logger.Info("Removing function resources", zap.String("function_id", functionID.String()))
	// In a real implementation, we would remove any function-specific resources
	// For now, we don't need to do anything as containers are cleaned up after execution
	return nil
}

func (s *SimpleDockerRuntime) GetLogs(ctx context.Context, executionID uuid.UUID) ([]string, error) {
	// In a real implementation, we would need to store container IDs associated with execution IDs
	// For now, we'll return a placeholder
	return []string{
		"Function execution logs would appear here",
		"In a full implementation, these would be retrieved from the Docker container",
	}, nil
}

func (s *SimpleDockerRuntime) HealthCheck(ctx context.Context) error {
	_, err := s.client.Ping(ctx)
	return err
}

func (s *SimpleDockerRuntime) GetInfo(ctx context.Context) (*runtime.RuntimeInfo, error) {
	info, err := s.client.Info(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to get Docker info: %w", err)
	}

	return &runtime.RuntimeInfo{
		Type:      "docker",
		Version:   info.ServerVersion,
		Available: true,
		Endpoint:  s.client.DaemonHost(),
		Metadata: map[string]string{
			"containers":      fmt.Sprintf("%d", info.Containers),
			"images":          fmt.Sprintf("%d", info.Images),
			"docker_root_dir": info.DockerRootDir,
		},
	}, nil
}

func (s *SimpleDockerRuntime) ListContainers(ctx context.Context) ([]runtime.ContainerInfo, error) {
	containers, err := s.client.ContainerList(ctx, container.ListOptions{})
	if err != nil {
		return nil, fmt.Errorf("failed to list containers: %w", err)
	}

	var containerInfos []runtime.ContainerInfo
	for _, c := range containers {
		containerInfo := runtime.ContainerInfo{
			ID:     c.ID,
			Status: c.State,
			Image:  c.Image,
		}

		if len(c.Names) > 0 {
			containerInfo.ID = c.Names[0]
		}

		containerInfos = append(containerInfos, containerInfo)
	}

	return containerInfos, nil
}

func (s *SimpleDockerRuntime) StopExecution(ctx context.Context, executionID uuid.UUID) error {
	s.logger.Info("Stopping execution", zap.String("execution_id", executionID.String()))
	// In a real implementation, we would need to map execution IDs to container IDs
	// For now, we'll just log that this was called
	return nil
}

// Helper methods

func (s *SimpleDockerRuntime) createContainer(ctx context.Context, function *domain.FunctionDefinition, input json.RawMessage) (string, error) {
	// Prepare environment variables
	env := []string{}
	for key, value := range function.Environment {
		env = append(env, fmt.Sprintf("%s=%s", key, value))
	}

	// Add input as environment variable
	inputStr := string(input)
	if inputStr != "" {
		env = append(env, fmt.Sprintf("FUNCTION_INPUT=%s", inputStr))
	}

	// Add function code as environment variable for dynamic languages
	env = append(env, fmt.Sprintf("FUNCTION_CODE=%s", function.Code))
	env = append(env, fmt.Sprintf("FUNCTION_HANDLER=%s", function.Handler))

	// Create container config with proper command for runtime
	config := &container.Config{
		Image:        function.Image,
		Env:          env,
		AttachStdout: true,
		AttachStderr: true,
	}

	// Set command based on runtime
	switch function.Runtime {
	case "nodejs", "nodejs18", "nodejs20":
		config.Cmd = []string{"sh", "-c", `
			echo "$FUNCTION_CODE" > /tmp/index.js && 
			echo "const handler = require('/tmp/index.js').handler; 
			const input = process.env.FUNCTION_INPUT ? JSON.parse(process.env.FUNCTION_INPUT) : {}; 
			const context = { functionName: '` + function.Name + `' }; 
			console.log('<stdout>'); 
			handler(input, context).then(result => { 
				console.log('</stdout>'); 
				console.log('<result>' + JSON.stringify(result) + '</result>'); 
			}).catch(err => { 
				console.log('</stdout>'); 
				console.error('<result>{\"error\": \"' + err.message + '\"}</result>'); 
				process.exit(1); 
			});" > /tmp/runner.js &&
			node /tmp/runner.js
		`}
	case "python", "python3", "python3.9", "python3.10", "python3.11":
		config.Cmd = []string{"sh", "-c", `
			echo "$FUNCTION_CODE" > /tmp/handler.py && 
			echo "import json, os, sys; sys.path.insert(0, '/tmp'); from handler import handler; 
			input_data = json.loads(os.environ.get('FUNCTION_INPUT', '{}')); 
			context = {'function_name': '` + function.Name + `'}; 
			print('<stdout>'); 
			try: 
				result = handler(input_data, context); 
				print('</stdout>'); 
				print('<result>' + json.dumps(result) + '</result>'); 
			except Exception as e: 
				print('</stdout>'); 
				print('<result>{\"error\": \"' + str(e) + '\"}</result>', file=sys.stderr); 
				sys.exit(1);" > /tmp/runner.py &&
			python /tmp/runner.py
		`}
	default:
		// For other runtimes, assume they handle execution themselves
		// This is for pre-built container images
	}

	// Create host config with resource limits
	hostConfig := &container.HostConfig{
		Resources: container.Resources{
			Memory: int64(function.Memory) * 1024 * 1024, // Convert MB to bytes
		},
	}

	// Apply timeout if set
	if function.Timeout.Duration > 0 {
		// Docker doesn't have a direct timeout, but we can set a reasonable upper limit
		// In a production system, you'd want to implement actual timeout handling
		hostConfig.Resources.NanoCPUs = 1000000000 // 1 CPU
	}

	resp, err := s.client.ContainerCreate(ctx, config, hostConfig, nil, nil, "")
	if err != nil {
		return "", fmt.Errorf("failed to create container: %w", err)
	}

	return resp.ID, nil
}

func (s *SimpleDockerRuntime) getContainerLogs(ctx context.Context, containerID string) ([]string, error) {
	// Get container logs
	logs, err := s.client.ContainerLogs(ctx, containerID, container.LogsOptions{
		ShowStdout: true,
		ShowStderr: true,
		Tail:       "100", // Get last 100 lines
	})
	if err != nil {
		return nil, fmt.Errorf("failed to get container logs: %w", err)
	}
	defer logs.Close()

	// Read the actual logs content
	logData, err := io.ReadAll(logs)
	if err != nil {
		return nil, fmt.Errorf("failed to read log data: %w", err)
	}

	// Parse Docker logs to remove binary headers
	rawOutput := parseDockerLogs(logData)
	
	// Parse the XML-tagged output to extract logs
	parsedLogs, _, err := s.parseContainerOutput(rawOutput)
	if err != nil {
		s.logger.Warn("Failed to parse container output for logs", zap.Error(err))
		// Fallback to raw output split by lines
		lines := strings.Split(strings.TrimSpace(rawOutput), "\n")
		cleanLines := make([]string, 0, len(lines))
		for _, line := range lines {
			if trimmed := strings.TrimSpace(line); trimmed != "" {
				cleanLines = append(cleanLines, trimmed)
			}
		}
		return cleanLines, nil
	}

	// If no logs were parsed from <stdout> tags, fallback to basic parsing
	if len(parsedLogs) == 0 {
		lines := strings.Split(strings.TrimSpace(rawOutput), "\n")
		for _, line := range lines {
			if trimmed := strings.TrimSpace(line); trimmed != "" && !strings.Contains(trimmed, "<result>") && !strings.Contains(trimmed, "</result>") {
				parsedLogs = append(parsedLogs, trimmed)
			}
		}
	}

	return parsedLogs, nil
}

func (s *SimpleDockerRuntime) getContainerOutput(ctx context.Context, containerID string) (json.RawMessage, error) {
	// Get container logs as output
	logs, err := s.client.ContainerLogs(ctx, containerID, container.LogsOptions{
		ShowStdout: true,
		ShowStderr: true,
		Tail:       "100", // Get last 100 lines
	})
	if err != nil {
		return nil, fmt.Errorf("failed to get container logs: %w", err)
	}
	defer logs.Close()

	// Read the actual logs content
	logData, err := io.ReadAll(logs)
	if err != nil {
		return nil, fmt.Errorf("failed to read log data: %w", err)
	}

	// Parse Docker logs to remove binary headers
	rawOutput := parseDockerLogs(logData)
	
	// Parse the XML-tagged output to extract the result
	_, result, err := s.parseContainerOutput(rawOutput)
	if err != nil {
		s.logger.Warn("Failed to parse container output for result", zap.Error(err))
		// Fallback to legacy parsing
		logContent := strings.TrimSpace(rawOutput)
		if json.Valid([]byte(logContent)) && logContent != "" {
			return json.RawMessage(logContent), nil
		} else {
			// Return the output wrapped in a JSON object
			fallbackResult := map[string]interface{}{
				"result": "Function executed successfully",
				"output": logContent,
				"timestamp": time.Now().UTC(),
			}
			resultJSON, _ := json.Marshal(fallbackResult)
			return json.RawMessage(resultJSON), nil
		}
	}

	// If no result was found in XML tags, provide a default success result
	if result == nil {
		defaultResult := map[string]interface{}{
			"result": "Function executed successfully",
			"message": "No result output found",
			"timestamp": time.Now().UTC(),
		}
		resultJSON, _ := json.Marshal(defaultResult)
		return json.RawMessage(resultJSON), nil
	}

	return result, nil
}

// parseDockerLogs parses Docker log output which includes 8-byte headers
func parseDockerLogs(logData []byte) string {
	var cleanOutput strings.Builder
	
	for len(logData) > 8 {
		// Docker log header: [STREAM_TYPE, 0, 0, 0, SIZE1, SIZE2, SIZE3, SIZE4]
		// Skip the first 8 bytes (header)
		headerSize := 8
		if len(logData) < headerSize {
			break
		}
		
		// Extract size from bytes 4-7 (big endian)
		size := int(logData[4])<<24 + int(logData[5])<<16 + int(logData[6])<<8 + int(logData[7])
		
		if len(logData) < headerSize+size {
			// If the remaining data is less than expected size, take what we have
			size = len(logData) - headerSize
		}
		
		if size > 0 {
			// Extract the actual log content
			content := string(logData[headerSize : headerSize+size])
			cleanOutput.WriteString(content)
		}
		
		// Move to next log entry
		logData = logData[headerSize+size:]
	}
	
	return cleanOutput.String()
}

// parseContainerOutput parses container output that contains <stdout> and <result> XML tags
func (s *SimpleDockerRuntime) parseContainerOutput(rawOutput string) (logs []string, result json.RawMessage, err error) {
	// Extract stdout content (logs) - use DOTALL flag for multiline matching
	stdoutRegex := regexp.MustCompile(`(?s)<stdout>(.*?)</stdout>`)
	stdoutMatch := stdoutRegex.FindStringSubmatch(rawOutput)
	if len(stdoutMatch) > 1 {
		stdoutContent := strings.TrimSpace(stdoutMatch[1])
		if stdoutContent != "" {
			// Split stdout content into lines for logs
			lines := strings.Split(stdoutContent, "\n")
			// Clean up empty lines and trim whitespace
			cleanLogs := make([]string, 0, len(lines))
			for _, line := range lines {
				if trimmed := strings.TrimSpace(line); trimmed != "" {
					cleanLogs = append(cleanLogs, trimmed)
				}
			}
			logs = cleanLogs
		}
	}

	// Extract result content - use DOTALL flag for multiline matching
	resultRegex := regexp.MustCompile(`(?s)<result>(.*?)</result>`)
	resultMatch := resultRegex.FindStringSubmatch(rawOutput)
	if len(resultMatch) > 1 {
		resultContent := strings.TrimSpace(resultMatch[1])
		if resultContent != "" {
			// Validate JSON
			if json.Valid([]byte(resultContent)) {
				result = json.RawMessage(resultContent)
			} else {
				// If not valid JSON, wrap it
				wrappedResult := map[string]interface{}{
					"output": resultContent,
				}
				resultJSON, _ := json.Marshal(wrappedResult)
				result = json.RawMessage(resultJSON)
			}
		}
	}

	// If no result tag found, treat entire output as result (fallback for non-tagged output)
	if result == nil {
		// Remove any XML tags from the output for fallback
		cleanOutput := regexp.MustCompile(`(?s)<[^>]*>`).ReplaceAllString(rawOutput, "")
		cleanOutput = strings.TrimSpace(cleanOutput)
		
		if cleanOutput != "" {
			if json.Valid([]byte(cleanOutput)) {
				result = json.RawMessage(cleanOutput)
			} else {
				// Wrap non-JSON output
				wrappedResult := map[string]interface{}{
					"output": cleanOutput,
				}
				resultJSON, _ := json.Marshal(wrappedResult)
				result = json.RawMessage(resultJSON)
			}
		}
	}

	return logs, result, nil
}

func (s *SimpleDockerRuntime) cleanupContainer(ctx context.Context, containerID string) {
	// Remove container
	if err := s.client.ContainerRemove(ctx, containerID, container.RemoveOptions{
		Force: true,
	}); err != nil {
		s.logger.Warn("Failed to remove container",
			zap.String("container_id", containerID),
			zap.Error(err))
	}
}