<?php

declare(strict_types=1);

namespace Tests\Unit\Framework\Async;

use App\Framework\Async\AsyncChannel;
use App\Framework\Async\ChannelClosedException;
use App\Framework\Async\FiberManager;
use App\Framework\DateTime\SystemClock;
use App\Framework\DateTime\SystemTimer;
use Fiber;

describe('AsyncChannel', function () {
    beforeEach(function () {
        $clock = new SystemClock();
        $timer = new SystemTimer();
        $this->fiberManager = new FiberManager($clock, $timer);
    });

    it('creates unbuffered channel by default', function () {
        $channel = new AsyncChannel();
        
        $stats = $channel->getStats();
        expect($stats['capacity'])->toBe(0);
        expect($stats['buffered_items'])->toBe(0);
    });

    it('creates buffered channel with capacity', function () {
        $channel = new AsyncChannel(capacity: 10);
        
        $stats = $channel->getStats();
        expect($stats['capacity'])->toBe(10);
    });

    it('supports producer-consumer pattern with buffered channel', function () {
        $channel = new AsyncChannel(capacity: 5);
        $received = [];

        // Producer fiber
        $producer = $this->fiberManager->asyncCooperative(function () use ($channel) {
            for ($i = 1; $i <= 3; $i++) {
                $channel->send("item-{$i}");
            }
            $channel->close();
        });

        // Consumer fiber
        $consumer = $this->fiberManager->asyncCooperative(function () use ($channel, &$received) {
            try {
                while (true) {
                    $item = $channel->receive();
                    $received[] = $item;
                }
            } catch (ChannelClosedException) {
                // Channel closed, stop consuming
            }
        });

        // Start fibers
        $producer->start();
        $consumer->start();

        // Process until both terminated
        while (!$producer->isTerminated() || !$consumer->isTerminated()) {
            if ($producer->isSuspended()) {
                $producer->resume();
            }
            if ($consumer->isSuspended()) {
                $consumer->resume();
            }
        }

        expect($received)->toBe(['item-1', 'item-2', 'item-3']);
    });

    it('blocks producer when buffered channel is full', function () {
        $channel = new AsyncChannel(capacity: 2);
        $sent = 0;

        $producer = new Fiber(function () use ($channel, &$sent) {
            for ($i = 1; $i <= 5; $i++) {
                $channel->send("item-{$i}");
                $sent = $i;
            }
        });

        $producer->start();

        // Producer should have sent 2 items and then blocked
        expect($sent)->toBe(2);
        expect($channel->count())->toBe(2);

        // Receive one item to free space
        $item = $channel->receive();
        expect($item)->toBe('item-1');

        // Resume producer
        if ($producer->isSuspended()) {
            $producer->resume();
        }

        // Should have sent one more
        expect($sent)->toBe(3);
    });

    it('throws exception when sending to closed channel', function () {
        $channel = new AsyncChannel(capacity: 5);
        $channel->close();

        expect(fn() => $channel->send('test'))
            ->toThrow(ChannelClosedException::class);
    });

    it('throws exception when receiving from closed empty channel', function () {
        $channel = new AsyncChannel(capacity: 5);
        $channel->close();

        expect(fn() => $channel->receive())
            ->toThrow(ChannelClosedException::class);
    });

    it('allows receiving remaining items after close', function () {
        $channel = new AsyncChannel(capacity: 5);
        
        $channel->send('item-1');
        $channel->send('item-2');
        $channel->close();

        // Can still receive buffered items
        expect($channel->receive())->toBe('item-1');
        expect($channel->receive())->toBe('item-2');

        // Now throws
        expect(fn() => $channel->receive())
            ->toThrow(ChannelClosedException::class);
    });

    it('supports non-blocking try operations', function () {
        $channel = new AsyncChannel(capacity: 2);

        // trySend succeeds when space available
        expect($channel->trySend('item-1'))->toBeTrue();
        expect($channel->trySend('item-2'))->toBeTrue();
        expect($channel->trySend('item-3'))->toBeFalse(); // Full

        // tryReceive succeeds when items available
        $result = $channel->tryReceive();
        expect($result['success'])->toBeTrue();
        expect($result['value'])->toBe('item-1');

        $result = $channel->tryReceive();
        expect($result['success'])->toBeTrue();
        expect($result['value'])->toBe('item-2');

        $result = $channel->tryReceive();
        expect($result['success'])->toBeFalse(); // Empty
    });

    it('provides accurate channel statistics', function () {
        $channel = new AsyncChannel(capacity: 10);

        $channel->send('item-1');
        $channel->send('item-2');
        $channel->send('item-3');

        $stats = $channel->getStats();

        expect($stats['capacity'])->toBe(10);
        expect($stats['buffered_items'])->toBe(3);
        expect($stats['is_closed'])->toBeFalse();

        $channel->close();

        $stats = $channel->getStats();
        expect($stats['is_closed'])->toBeTrue();
    });

    it('counts buffered items correctly', function () {
        $channel = new AsyncChannel(capacity: 5);

        expect($channel->count())->toBe(0);

        $channel->send('a');
        expect($channel->count())->toBe(1);

        $channel->send('b');
        $channel->send('c');
        expect($channel->count())->toBe(3);

        $channel->receive();
        expect($channel->count())->toBe(2);
    });
});