package tasks

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"

	"github.com/atlasos/calypso/internal/common/database"
	"github.com/atlasos/calypso/internal/common/logger"
	"github.com/google/uuid"
)

// Engine manages async task execution
type Engine struct {
	db     *database.DB
	logger *logger.Logger
}

// NewEngine creates a new task engine
func NewEngine(db *database.DB, log *logger.Logger) *Engine {
	return &Engine{
		db:     db,
		logger: log,
	}
}

// TaskStatus represents the state of a task
type TaskStatus string

const (
	TaskStatusPending   TaskStatus = "pending"
	TaskStatusRunning   TaskStatus = "running"
	TaskStatusCompleted TaskStatus = "completed"
	TaskStatusFailed    TaskStatus = "failed"
	TaskStatusCancelled TaskStatus = "cancelled"
)

// TaskType represents the type of task
type TaskType string

const (
	TaskTypeInventory     TaskType = "inventory"
	TaskTypeLoadUnload    TaskType = "load_unload"
	TaskTypeRescan        TaskType = "rescan"
	TaskTypeApplySCST     TaskType = "apply_scst"
	TaskTypeSupportBundle TaskType = "support_bundle"
)

// CreateTask creates a new task
func (e *Engine) CreateTask(ctx context.Context, taskType TaskType, createdBy string, metadata map[string]interface{}) (string, error) {
	taskID := uuid.New().String()

	var metadataJSON *string
	if metadata != nil {
		bytes, err := json.Marshal(metadata)
		if err != nil {
			return "", fmt.Errorf("failed to marshal metadata: %w", err)
		}
		jsonStr := string(bytes)
		metadataJSON = &jsonStr
	}

	query := `
		INSERT INTO tasks (id, type, status, progress, created_by, metadata)
		VALUES ($1, $2, $3, $4, $5, $6)
	`

	_, err := e.db.ExecContext(ctx, query,
		taskID, string(taskType), string(TaskStatusPending), 0, createdBy, metadataJSON,
	)
	if err != nil {
		return "", fmt.Errorf("failed to create task: %w", err)
	}

	e.logger.Info("Task created", "task_id", taskID, "type", taskType)
	return taskID, nil
}

// StartTask marks a task as running
func (e *Engine) StartTask(ctx context.Context, taskID string) error {
	query := `
		UPDATE tasks
		SET status = $1, progress = 0, started_at = NOW(), updated_at = NOW()
		WHERE id = $2 AND status = $3
	`

	result, err := e.db.ExecContext(ctx, query, string(TaskStatusRunning), taskID, string(TaskStatusPending))
	if err != nil {
		return fmt.Errorf("failed to start task: %w", err)
	}

	rows, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rows == 0 {
		return fmt.Errorf("task not found or already started")
	}

	e.logger.Info("Task started", "task_id", taskID)
	return nil
}

// UpdateProgress updates task progress
func (e *Engine) UpdateProgress(ctx context.Context, taskID string, progress int, message string) error {
	if progress < 0 || progress > 100 {
		return fmt.Errorf("progress must be between 0 and 100")
	}

	query := `
		UPDATE tasks
		SET progress = $1, message = $2, updated_at = NOW()
		WHERE id = $3
	`

	_, err := e.db.ExecContext(ctx, query, progress, message, taskID)
	if err != nil {
		return fmt.Errorf("failed to update progress: %w", err)
	}

	return nil
}

// CompleteTask marks a task as completed
func (e *Engine) CompleteTask(ctx context.Context, taskID string, message string) error {
	query := `
		UPDATE tasks
		SET status = $1, progress = 100, message = $2, completed_at = NOW(), updated_at = NOW()
		WHERE id = $3
	`

	result, err := e.db.ExecContext(ctx, query, string(TaskStatusCompleted), message, taskID)
	if err != nil {
		return fmt.Errorf("failed to complete task: %w", err)
	}

	rows, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rows == 0 {
		return fmt.Errorf("task not found")
	}

	e.logger.Info("Task completed", "task_id", taskID)
	return nil
}

// FailTask marks a task as failed
func (e *Engine) FailTask(ctx context.Context, taskID string, errorMessage string) error {
	query := `
		UPDATE tasks
		SET status = $1, error_message = $2, completed_at = NOW(), updated_at = NOW()
		WHERE id = $3
	`

	result, err := e.db.ExecContext(ctx, query, string(TaskStatusFailed), errorMessage, taskID)
	if err != nil {
		return fmt.Errorf("failed to fail task: %w", err)
	}

	rows, err := result.RowsAffected()
	if err != nil {
		return fmt.Errorf("failed to get rows affected: %w", err)
	}

	if rows == 0 {
		return fmt.Errorf("task not found")
	}

	e.logger.Error("Task failed", "task_id", taskID, "error", errorMessage)
	return nil
}

// GetTask retrieves a task by ID
func (e *Engine) GetTask(ctx context.Context, taskID string) (*Task, error) {
	query := `
		SELECT id, type, status, progress, message, error_message,
		       created_by, started_at, completed_at, created_at, updated_at, metadata
		FROM tasks
		WHERE id = $1
	`

	var task Task
	var errorMsg, createdBy sql.NullString
	var startedAt, completedAt sql.NullTime
	var metadata sql.NullString

	err := e.db.QueryRowContext(ctx, query, taskID).Scan(
		&task.ID, &task.Type, &task.Status, &task.Progress,
		&task.Message, &errorMsg, &createdBy,
		&startedAt, &completedAt, &task.CreatedAt, &task.UpdatedAt, &metadata,
	)
	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("task not found")
		}
		return nil, fmt.Errorf("failed to get task: %w", err)
	}

	if errorMsg.Valid {
		task.ErrorMessage = errorMsg.String
	}
	if createdBy.Valid {
		task.CreatedBy = createdBy.String
	}
	if startedAt.Valid {
		task.StartedAt = &startedAt.Time
	}
	if completedAt.Valid {
		task.CompletedAt = &completedAt.Time
	}
	if metadata.Valid && metadata.String != "" {
		json.Unmarshal([]byte(metadata.String), &task.Metadata)
	}

	return &task, nil
}