// Package executor provides job execution implementations
package executor

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"github.com/jfraeys/fetch_ml/internal/errtypes"
	"github.com/jfraeys/fetch_ml/internal/logging"
	"github.com/jfraeys/fetch_ml/internal/manifest"
	"github.com/jfraeys/fetch_ml/internal/queue"
	"github.com/jfraeys/fetch_ml/internal/storage"
	"github.com/jfraeys/fetch_ml/internal/worker/execution"
	"github.com/jfraeys/fetch_ml/internal/worker/interfaces"
)

// JobRunner orchestrates job execution by delegating to specific executors
type JobRunner struct {
	local     interfaces.JobExecutor
	container interfaces.JobExecutor
	writer    interfaces.ManifestWriter
	logger    *logging.Logger
}

// NewJobRunner creates a new job runner
func NewJobRunner(
	local interfaces.JobExecutor,
	container interfaces.JobExecutor,
	writer interfaces.ManifestWriter,
	logger *logging.Logger,
) *JobRunner {
	return &JobRunner{
		local:     local,
		container: container,
		writer:    writer,
		logger:    logger,
	}
}

// ExecutionMode determines which executor to use
type ExecutionMode int

const (
	// ModeAuto selects based on configuration
	ModeAuto ExecutionMode = iota
	// ModeLocal forces local execution
	ModeLocal
	// ModeContainer forces container execution
	ModeContainer
)

// Run executes a job with the given mode
func (r *JobRunner) Run(
	ctx context.Context,
	task *queue.Task,
	basePath string,
	mode ExecutionMode,
	localMode bool,
	gpuEnv interfaces.ExecutionEnv,
) error {
	// 1. Setup directories
	jobDir, outputDir, logFile, err := execution.SetupJobDirectories(basePath, task.JobName, task.ID)
	if err != nil {
		return err
	}

	// 2. Create execution environment
	env := interfaces.ExecutionEnv{
		JobDir:        jobDir,
		OutputDir:     outputDir,
		LogFile:       logFile,
		GPUDevices:    gpuEnv.GPUDevices,
		GPUEnvVar:     gpuEnv.GPUEnvVar,
		GPUDevicesStr: gpuEnv.GPUDevicesStr,
	}

	// 3. Select executor
	executor := r.selectExecutor(mode, localMode)

	// 3.5 Validate manifest completeness before execution
	if r.writer != nil {
		// Load current manifest and validate
		if m, err := manifest.LoadFromDir(outputDir); err == nil {
			validator := manifest.NewValidator()
			if err := validator.Validate(m); err != nil {
				r.logger.Error("manifest validation failed - execution blocked",
					"task", task.ID,
					"error", err)
				return &errtypes.TaskExecutionError{
					TaskID:      task.ID,
					JobName:     task.JobName,
					Phase:       "validation",
					Message:     "manifest incomplete - execution blocked",
					Err:         err,
					Recoverable: false, // Can't retry - manifest is missing data
				}
			}
		}
	}

	// 4. Pre-execution manifest update
	if r.writer != nil {
		r.writer.Upsert(outputDir, task, func(m *manifest.RunManifest) {
			m.MarkStarted(time.Now().UTC())
			m.GPUDevices = gpuEnv.GPUDevices
			if gpuEnv.GPUEnvVar != "" {
				m.Metadata["gpu_visible_devices"] = gpuEnv.GPUDevicesStr
				m.Metadata["gpu_visible_env"] = gpuEnv.GPUEnvVar
			}
		})
	}

	// 5. Execute
	execErr := executor.Execute(ctx, task, env)

	// 6. Post-execution cleanup
	return r.finalize(task, outputDir, basePath, execErr)
}

func (r *JobRunner) selectExecutor(mode ExecutionMode, localMode bool) interfaces.JobExecutor {
	switch mode {
	case ModeLocal:
		return r.local
	case ModeContainer:
		return r.container
	default: // ModeAuto
		if localMode {
			return r.local
		}
		return r.container
	}
}

func (r *JobRunner) finalize(
	task *queue.Task,
	outputDir string,
	basePath string,
	execErr error,
) error {
	jobPaths := storage.NewJobPaths(basePath)

	if execErr != nil {
		// Handle failure
		failedDir := filepath.Join(jobPaths.FailedPath(), task.JobName)
		os.MkdirAll(filepath.Dir(failedDir), 0750)
		os.RemoveAll(failedDir)

		if r.writer != nil {
			r.writer.Upsert(outputDir, task, func(m *manifest.RunManifest) {
				now := time.Now().UTC()
				exitCode := 1
				m.MarkFinished(now, &exitCode, execErr)
			})
		}

		os.Rename(outputDir, failedDir)

		if taskErr, ok := execErr.(*errtypes.TaskExecutionError); ok {
			return taskErr
		}
		return &errtypes.TaskExecutionError{
			TaskID:  task.ID,
			JobName: task.JobName,
			Phase:   "execution",
			Err:     execErr,
		}
	}

	// Handle success
	finishedDir := filepath.Join(jobPaths.FinishedPath(), task.JobName)
	os.MkdirAll(filepath.Dir(finishedDir), 0750)
	os.RemoveAll(finishedDir)

	if r.writer != nil {
		r.writer.Upsert(outputDir, task, func(m *manifest.RunManifest) {
			now := time.Now().UTC()
			exitCode := 0
			m.MarkFinished(now, &exitCode, nil)
		})
	}

	if err := os.Rename(outputDir, finishedDir); err != nil {
		r.logger.Warn("failed to move job to finished dir", "job", task.JobName, "error", err)
		return fmt.Errorf("failed to move job to finished: %w", err)
	}

	return nil
}