<?php

declare(strict_types=1);

namespace App\Framework\ExceptionHandling\Scope;

use App\Framework\DI\Initializer;
use Fiber;

/**
 * Error Scope Stack Manager
 *
 * Manages fiber-aware scope stack for error context enrichment.
 * Each fiber has its own isolated scope stack.
 *
 * PHP 8.5+ with fiber isolation and automatic cleanup.
 */
final class ErrorScope
{
    /** @var array<int, array<ErrorScopeContext>> Fiber-specific scope stacks */
    private array $stack = [];

    #[Initializer]
    public static function initialize(): self
    {
        return new self();
    }

    /**
     * Enter a new error scope
     *
     * @param ErrorScopeContext $context Scope context to enter
     * @return int Token for leaving this scope (stack depth)
     */
    public function enter(ErrorScopeContext $context): int
    {
        $id = $this->fiberId();
        $this->stack[$id] ??= [];
        $this->stack[$id][] = $context;

        return count($this->stack[$id]);
    }

    /**
     * Exit error scope(s)
     *
     * @param int $token Token from enter() - exits all scopes until this depth
     */
    public function exit(int $token = 0): void
    {
        $id = $this->fiberId();

        if (!isset($this->stack[$id])) {
            return;
        }

        if ($token === 0) {
            // Exit only the most recent scope
            array_pop($this->stack[$id]);
        } else {
            // Exit all scopes until token depth
            while (!empty($this->stack[$id]) && count($this->stack[$id]) >= $token) {
                array_pop($this->stack[$id]);
            }
        }

        // Cleanup empty stack
        if (empty($this->stack[$id])) {
            unset($this->stack[$id]);
        }
    }

    /**
     * Get current error scope context
     *
     * @return ErrorScopeContext|null Current scope or null if no scope active
     */
    public function current(): ?ErrorScopeContext
    {
        $id = $this->fiberId();
        $stack = $this->stack[$id] ?? [];

        $current = end($stack);
        return $current !== false ? $current : null;
    }

    /**
     * Check if any scope is active
     */
    public function hasScope(): bool
    {
        $id = $this->fiberId();
        return !empty($this->stack[$id]);
    }

    /**
     * Get scope depth (number of nested scopes)
     */
    public function depth(): int
    {
        $id = $this->fiberId();
        return count($this->stack[$id] ?? []);
    }

    /**
     * Get fiber ID for isolation
     *
     * Returns 0 for main fiber, unique ID for each Fiber
     */
    private function fiberId(): int
    {
        $fiber = Fiber::getCurrent();
        return $fiber ? spl_object_id($fiber) : 0;
    }

    /**
     * Clear all scopes (for testing/cleanup)
     */
    public function clear(): void
    {
        $this->stack = [];
    }

    /**
     * Get statistics for monitoring
     */
    public function getStats(): array
    {
        return [
            'active_fibers' => count($this->stack),
            'total_scopes' => array_sum(array_map('count', $this->stack)),
            'max_depth' => !empty($this->stack) ? max(array_map('count', $this->stack)) : 0,
        ];
    }
}