<?php
/**
 * CODING CONVENTION:
 * This file follows the coding convention where variable_names and function_names
 * use snake_case (underscore_wherever_possible).
 */

namespace App\RSpade\Commands\Rsx;

use Illuminate\Console\Command;
use Illuminate\Support\Facades\DB;
use App\RSpade\Core\Task\Task;
use App\RSpade\Core\Task\Task_Instance;
use App\RSpade\Core\Task\Task_Status;
use App\RSpade\Core\Task\Task_Lock;
use App\RSpade\Core\Task\Cron_Parser;
use Symfony\Component\Process\Process;

/**
 * Task Process Command
 *
 * Main worker manager for the task system. Handles:
 * - Processing queued tasks
 * - Executing scheduled tasks
 * - Spawning worker processes
 * - Detecting and recovering stuck tasks
 *
 * This command is designed to run via cron every minute:
 *   * * * * * cd /var/www/html && php artisan rsx:task:process
 *
 * It will:
 * 1. Check for stuck tasks and mark them as failed
 * 2. Process scheduled tasks that are due
 * 3. Spawn workers for queued tasks (up to concurrency limits)
 * 4. Exit quickly if no work to do
 */
class Task_Process_Command extends Command
{
    protected $signature = 'rsx:task:process
        {--queue= : Process only this specific queue}
        {--once : Process one task and exit (for testing)}
        {--force-scheduled : Run all scheduled tasks immediately (ignore next_run_at)}';

    protected $description = 'Process queued and scheduled tasks (run via cron every minute)';

    public function handle()
    {
        $specific_queue = $this->option('queue');
        $once_mode = $this->option('once');

        $this->info('[TASK PROCESSOR] Starting task processor');

        // Step 1: Detect and recover stuck tasks
        $this->detect_stuck_tasks();

        // Step 2: Process scheduled tasks
        if (!$specific_queue) {
            $this->process_scheduled_tasks();
        }

        // Step 3: Spawn workers for queued tasks
        $this->spawn_workers_for_queues($specific_queue);

        // If in once mode, process one task directly (for testing)
        if ($once_mode) {
            $this->process_one_task($specific_queue ?? 'default');
        }

        $this->info('[TASK PROCESSOR] Task processor complete');

        return 0;
    }

    /**
     * Detect and mark stuck tasks as failed
     *
     * A task is considered stuck if:
     * - Status is 'running'
     * - Started more than timeout seconds ago
     * - Worker PID is dead or missing
     */
    private function detect_stuck_tasks(): void
    {
        $cleanup_after = config('rsx.tasks.cleanup_stuck_after', 1800);

        $stuck_tasks = DB::table('_task_queue')
            ->where('status', Task_Status::RUNNING)
            ->where('started_at', '<', now()->subSeconds($cleanup_after))
            ->get();

        foreach ($stuck_tasks as $task) {
            // Check if worker process is still alive
            $worker_alive = $task->worker_pid && posix_kill($task->worker_pid, 0);

            if (!$worker_alive) {
                $this->warn("[STUCK TASK] Marking task {$task->id} as failed (worker PID {$task->worker_pid} not responding)");

                DB::table('_task_queue')
                    ->where('id', $task->id)
                    ->update([
                        'status' => Task_Status::FAILED,
                        'error' => 'Task stuck - worker process not responding',
                        'completed_at' => now(),
                        'updated_at' => now(),
                    ]);
            }
        }
    }

    /**
     * Process scheduled tasks that are due
     *
     * Scans manifest for #[Schedule] attributes and ensures each has a database record.
     * Creates pending task instances for any scheduled tasks that are due.
     */
    private function process_scheduled_tasks(): void
    {
        $force_all = $this->option('force-scheduled');

        // Get all scheduled tasks from manifest
        $scheduled_tasks = Task::get_scheduled_tasks();

        if (empty($scheduled_tasks)) {
            return;
        }

        $this->info("[SCHEDULED] Found " . count($scheduled_tasks) . " scheduled task(s) in manifest");

        foreach ($scheduled_tasks as $task_def) {
            $this->process_scheduled_task($task_def, $force_all);
        }
    }

    /**
     * Process a single scheduled task definition
     *
     * @param array $task_def Task definition from manifest
     * @param bool $force_run If true, run immediately regardless of schedule
     */
    private function process_scheduled_task(array $task_def, bool $force_run): void
    {
        $class = $task_def['class'];
        $method = $task_def['method'];
        $cron_expression = $task_def['cron_expression'];
        $queue = $task_def['queue'];

        // Check if we have a record for this scheduled task
        $existing = DB::table('_task_queue')
            ->where('class', $class)
            ->where('method', $method)
            ->where('queue', $queue)
            ->whereNotNull('next_run_at')
            ->whereIn('status', [Task_Status::PENDING, Task_Status::RUNNING])
            ->first();

        if (!$existing) {
            // Create initial scheduled task record
            $parser = new Cron_Parser($cron_expression);
            $next_run_at = $parser->get_next_run_time();

            $this->info("[SCHEDULED] Registering new scheduled task: {$class}::{$method}");
            $this->info("[SCHEDULED]   Cron: {$cron_expression}");
            $this->info("[SCHEDULED]   Next run: " . date('Y-m-d H:i:s', $next_run_at));

            DB::table('_task_queue')->insert([
                'class' => $class,
                'method' => $method,
                'queue' => $queue,
                'status' => Task_Status::PENDING,
                'params' => json_encode([]),
                'next_run_at' => date('Y-m-d H:i:s', $next_run_at),
                'created_at' => now(),
                'updated_at' => now(),
            ]);

            return;
        }

        // Check if task is due to run
        $next_run_timestamp = strtotime($existing->next_run_at);
        $is_due = $next_run_timestamp <= time();

        if ($force_run || $is_due) {
            // Task is due - dispatch it
            $this->info("[SCHEDULED] Dispatching scheduled task: {$class}::{$method}");

            // Create a new pending task instance
            $task_id = DB::table('_task_queue')->insertGetId([
                'class' => $class,
                'method' => $method,
                'queue' => $queue,
                'status' => Task_Status::PENDING,
                'params' => json_encode([]),
                'scheduled_for' => now(),
                'created_at' => now(),
                'updated_at' => now(),
            ]);

            // Calculate next run time and update the scheduled task record
            $parser = new Cron_Parser($cron_expression);
            $next_run_at = $parser->get_next_run_time();

            DB::table('_task_queue')
                ->where('id', $existing->id)
                ->update([
                    'next_run_at' => date('Y-m-d H:i:s', $next_run_at),
                    'updated_at' => now(),
                ]);

            $this->info("[SCHEDULED]   Created task instance ID: {$task_id}");
            $this->info("[SCHEDULED]   Next run updated to: " . date('Y-m-d H:i:s', $next_run_at));
        }
    }

    /**
     * Spawn workers for queued tasks based on concurrency limits
     *
     * @param string|null $specific_queue If set, only process this queue
     */
    private function spawn_workers_for_queues(?string $specific_queue): void
    {
        $queue_config = config('rsx.tasks.queues', []);
        $global_max = config('rsx.tasks.global_max_workers', 1);

        // Count currently running workers across all queues
        $total_running = DB::table('_task_queue')
            ->where('status', Task_Status::RUNNING)
            ->count();

        if ($total_running >= $global_max) {
            $this->info("[WORKER SPAWN] Global limit reached ({$total_running}/{$global_max})");
            return;
        }

        // Get queues to process
        $queues_to_process = $specific_queue
            ? [$specific_queue => $queue_config[$specific_queue] ?? ['max_workers' => 1]]
            : $queue_config;

        foreach ($queues_to_process as $queue_name => $queue_settings) {
            $max_workers = $queue_settings['max_workers'] ?? 1;

            // Count running workers for this queue
            $queue_running = DB::table('_task_queue')
                ->where('queue', $queue_name)
                ->where('status', Task_Status::RUNNING)
                ->count();

            // Count pending tasks for this queue (exclude scheduled task records)
            $queue_pending = DB::table('_task_queue')
                ->where('queue', $queue_name)
                ->where('status', Task_Status::PENDING)
                ->whereNull('next_run_at')  // Exclude scheduled task records
                ->where(function ($query) {
                    $query->whereNull('scheduled_for')
                        ->orWhere('scheduled_for', '<=', now());
                })
                ->count();

            if ($queue_pending === 0) {
                continue;
            }

            // Calculate how many workers we can spawn
            $can_spawn_global = $global_max - $total_running;
            $can_spawn_queue = $max_workers - $queue_running;
            $can_spawn = min($can_spawn_global, $can_spawn_queue, $queue_pending);

            if ($can_spawn > 0) {
                $this->info("[WORKER SPAWN] Spawning {$can_spawn} worker(s) for queue '{$queue_name}'");

                for ($i = 0; $i < $can_spawn; $i++) {
                    $this->spawn_worker($queue_name);
                    $total_running++;
                }
            }
        }
    }

    /**
     * Spawn a worker process for a queue
     *
     * @param string $queue_name Queue to process
     */
    private function spawn_worker(string $queue_name): void
    {
        $process = new Process([
            'php',
            base_path('artisan'),
            'rsx:task:worker',
            '--queue=' . $queue_name,
        ]);

        $process->setTimeout(null);
        $process->start();

        $this->info("[WORKER SPAWN] Started worker process {$process->getPid()} for queue '{$queue_name}'");
    }

    /**
     * Process one task directly (for testing)
     *
     * @param string $queue_name Queue to process from
     */
    private function process_one_task(string $queue_name): void
    {
        $this->info("[ONCE MODE] Processing one task from queue '{$queue_name}'");

        // Use lock to ensure atomic task selection
        $lock = new Task_Lock("task_queue_{$queue_name}");

        if (!$lock->acquire()) {
            $this->warn("[ONCE MODE] Could not acquire lock for queue '{$queue_name}'");
            return;
        }

        try {
            // Select next pending task (exclude scheduled task records)
            $task_row = DB::table('_task_queue')
                ->where('queue', $queue_name)
                ->where('status', Task_Status::PENDING)
                ->whereNull('next_run_at')  // Exclude scheduled task records
                ->where(function ($query) {
                    $query->whereNull('scheduled_for')
                        ->orWhere('scheduled_for', '<=', now());
                })
                ->orderBy('created_at', 'asc')
                ->lockForUpdate()
                ->first();

            if (!$task_row) {
                $this->info("[ONCE MODE] No pending tasks in queue '{$queue_name}'");
                $lock->release();
                return;
            }

            // Mark as running
            DB::table('_task_queue')
                ->where('id', $task_row->id)
                ->update([
                    'status' => Task_Status::RUNNING,
                    'started_at' => now(),
                    'worker_pid' => getmypid(),
                    'updated_at' => now(),
                ]);

            $lock->release();

            // Execute the task
            $this->info("[ONCE MODE] Executing task {$task_row->id}: {$task_row->class}::{$task_row->method}");

            $task_instance = Task_Instance::find($task_row->id);

            try {
                $class = $task_row->class;
                $method = $task_row->method;
                $params = json_decode($task_row->params, true) ?? [];

                $result = $class::$method($task_instance, $params);

                $task_instance->mark_completed($result);

                $this->info("[ONCE MODE] Task {$task_row->id} completed successfully");
            } catch (\Exception $e) {
                $task_instance->mark_failed($e->getMessage());

                $this->error("[ONCE MODE] Task {$task_row->id} failed: " . $e->getMessage());
            }
        } finally {
            if ($lock->is_locked()) {
                $lock->release();
            }
        }
    }
}