package worker

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"github.com/jfraeys/fetch_ml/internal/container"
	"github.com/jfraeys/fetch_ml/internal/jupyter"
	"github.com/jfraeys/fetch_ml/internal/logging"
	"github.com/jfraeys/fetch_ml/internal/metrics"
	"github.com/jfraeys/fetch_ml/internal/queue"
	"github.com/jfraeys/fetch_ml/internal/resources"
	"github.com/jfraeys/fetch_ml/internal/tracking"
	"github.com/jfraeys/fetch_ml/internal/tracking/factory"
	trackingplugins "github.com/jfraeys/fetch_ml/internal/tracking/plugins"
	"github.com/jfraeys/fetch_ml/internal/worker/executor"
	"github.com/jfraeys/fetch_ml/internal/worker/lifecycle"
)

// NewWorker creates a new worker instance with composed dependencies.
func NewWorker(cfg *Config, _ string) (*Worker, error) {
	// Create queue backend
	backendCfg := queue.BackendConfig{
		Mode:                 cfg.Mode,
		Backend:              queue.QueueBackend(strings.ToLower(strings.TrimSpace(cfg.Queue.Backend))),
		RedisAddr:            cfg.RedisAddr,
		RedisPassword:        cfg.RedisPassword,
		RedisDB:              cfg.RedisDB,
		SQLitePath:           cfg.Queue.SQLitePath,
		FilesystemPath:       cfg.Queue.FilesystemPath,
		FallbackToFilesystem: cfg.Queue.FallbackToFilesystem,
		MetricsFlushInterval: cfg.MetricsFlushInterval,
		Scheduler: queue.SchedulerConfig{
			Address: cfg.Scheduler.Address,
			Cert:    cfg.Scheduler.Cert,
			Token:   cfg.Scheduler.Token,
		},
	}

	queueClient, err := queue.NewBackend(backendCfg)
	if err != nil {
		return nil, err
	}

	ctx, cancel := context.WithCancel(context.Background())
	ctx = logging.EnsureTrace(ctx)
	ctx = logging.CtxWithWorker(ctx, cfg.WorkerID)

	baseLogger := logging.NewLogger(slog.LevelInfo, false)
	logger := baseLogger.Component(ctx, "worker")
	metricsObj := &metrics.Metrics{}

	podmanMgr, err := container.NewPodmanManager(logger)
	if err != nil {
		cancel()
		return nil, fmt.Errorf("failed to create podman manager: %w", err)
	}

	jupyterMgr, err := jupyter.NewServiceManager(logger, jupyter.GetDefaultServiceConfig())
	if err != nil {
		cancel()
		return nil, fmt.Errorf("failed to create jupyter service manager: %w", err)
	}

	trackingRegistry := tracking.NewRegistry(logger)
	pluginLoader := factory.NewPluginLoader(logger, podmanMgr)

	if len(cfg.Plugins) == 0 {
		logger.Warn("no plugins configured, defining defaults")
		mlflowPlugin, err := trackingplugins.NewMLflowPlugin(
			logger,
			podmanMgr,
			trackingplugins.MLflowOptions{
				ArtifactBasePath: filepath.Join(cfg.BasePath, "tracking", "mlflow"),
			},
		)
		if err == nil {
			trackingRegistry.Register(mlflowPlugin)
		}

		tensorboardPlugin, err := trackingplugins.NewTensorBoardPlugin(
			logger,
			podmanMgr,
			trackingplugins.TensorBoardOptions{
				LogBasePath: filepath.Join(cfg.BasePath, "tracking", "tensorboard"),
			},
		)
		if err == nil {
			trackingRegistry.Register(tensorboardPlugin)
		}

		trackingRegistry.Register(trackingplugins.NewWandbPlugin())
	} else {
		if err := pluginLoader.LoadPlugins(cfg.Plugins, trackingRegistry); err != nil {
			cancel()
			return nil, fmt.Errorf("failed to load plugins: %w", err)
		}
	}

	// Create run loop configuration
	runLoopConfig := lifecycle.RunLoopConfig{
		WorkerID:          cfg.WorkerID,
		MaxWorkers:        cfg.MaxWorkers,
		PollInterval:      time.Duration(cfg.PollInterval) * time.Second,
		TaskLeaseDuration: cfg.TaskLeaseDuration,
		HeartbeatInterval: cfg.HeartbeatInterval,
		GracefulTimeout:   cfg.GracefulTimeout,
		PrewarmEnabled:    cfg.PrewarmEnabled,
	}

	// Create executors
	localExecutor := executor.NewLocalExecutor(logger, nil)
	containerExecutor := executor.NewContainerExecutor(
		logger,
		nil,
		executor.ContainerConfig{
			PodmanImage: cfg.PodmanImage,
			BasePath:    cfg.BasePath,
		},
	)

	// Create task executor adapter
	exec := executor.NewTaskExecutorAdapter(
		localExecutor,
		containerExecutor,
		cfg.LocalMode,
	)

	// Create state manager for task lifecycle management
	stateMgr := lifecycle.NewStateManager(nil) // Can pass audit logger if available

	// Create job runner
	jobRunner := executor.NewJobRunner(
		localExecutor,
		containerExecutor,
		nil, // ManifestWriter - can be added later if needed
		logger,
	)

	runLoop := lifecycle.NewRunLoop(
		runLoopConfig,
		queueClient,
		exec,
		metricsObj,
		logger,
		stateMgr,
	)

	// Create resource manager
	gpuCount, gpuDetectionInfo := parseGPUCountFromConfig(cfg)
	rm, err := resources.NewManager(resources.Options{
		TotalCPU:    parseCPUFromConfig(cfg),
		GPUCount:    gpuCount,
		SlotsPerGPU: parseGPUSlotsPerGPUFromConfig(),
	})
	if err != nil {
		cancel()
		return nil, fmt.Errorf("failed to init resource manager: %w", err)
	}

	worker := &Worker{
		ID:               cfg.WorkerID,
		Config:           cfg,
		Logger:           logger,
		RunLoop:          runLoop,
		Runner:           jobRunner,
		Metrics:          metricsObj,
		Health:           lifecycle.NewHealthMonitor(),
		Resources:        rm,
		Jupyter:          jupyterMgr,
		gpuDetectionInfo: gpuDetectionInfo,
	}

	// In distributed mode, store the scheduler connection for heartbeats
	if cfg.Mode == "distributed" {
		if schedBackend, ok := queueClient.(*queue.SchedulerBackend); ok {
			worker.schedulerConn = schedBackend.Conn()
		}
	}

	// Log GPU configuration
	if !cfg.LocalMode {
		gpuType := strings.ToLower(strings.TrimSpace(os.Getenv("FETCH_ML_GPU_TYPE")))
		if gpuType == "amd" {
			cancel()
			return nil, fmt.Errorf(
				"AMD GPU mode is not supported in production (FETCH_ML_GPU_TYPE=amd). " +
					"Use 'nvidia', 'apple', 'none', or GPUDevices config. " +
					"AMD support is available in local mode for experimental development",
			)
		} else if cfg.AppleGPU.Enabled {
			logger.Warn(
				"apple MPS GPU mode is intended for development; do not use in production",
				"gpu_type", "apple",
			)
		}
	}

	// Pre-pull tracking images in background
	go worker.prePullImages()

	// Cancel context is not needed after creation
	cancel()

	return worker, nil
}

// prePullImages pulls required container images in the background
func (w *Worker) prePullImages() {
	if w.Config.LocalMode {
		return
	}

	w.Logger.Info("starting image pre-pulling")

	// Pull worker image
	if w.Config.PodmanImage != "" {
		w.pullImage(w.Config.PodmanImage)
	}

	// Pull plugin images
	for name, cfg := range w.Config.Plugins {
		if !cfg.Enabled || cfg.Image == "" {
			continue
		}
		w.Logger.Info("pre-pulling plugin image", "plugin", name, "image", cfg.Image)
		w.pullImage(cfg.Image)
	}
}

// pullImage pulls a single container image
func (w *Worker) pullImage(image string) {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Minute)
	defer cancel()

	cmd := exec.CommandContext(ctx, "podman", "pull", image)
	if output, err := cmd.CombinedOutput(); err != nil {
		w.Logger.Warn("failed to pull image", "image", image, "error", err, "output", string(output))
	} else {
		w.Logger.Info("image pulled successfully", "image", image)
	}
}