<?php

namespace tobimori\Seo\Ai\Drivers;

use Generator;
use tobimori\Seo\Ai\Chunk;
use tobimori\Seo\Ai\Driver;
use tobimori\Seo\Ai\SseStream;

class Anthropic extends Driver
{
	protected const string DEFAULT_ENDPOINT = 'https://api.anthropic.com/v1/messages';
	protected const string DEFAULT_MODEL = 'claude-4-5-haiku';

	/**
	 * @inheritDoc
	 */
	public function stream(
		string $prompt,
		string|null $model = null,
	): Generator {
		$apiKey = $this->config('apiKey', required: true);
		$headers = [
			'Content-Type: application/json',
			'Accept: text/event-stream',
			"x-api-key: {$apiKey}",
			'anthropic-version: 2023-06-01',
		];

		$payload = [
			'model' => $model ?? $this->config('model', static::DEFAULT_MODEL),
			'messages' => [
				['role' => 'user', 'content' => $prompt]
			],
			'max_tokens' => 4096,
			'stream' => true,
		];

		$stream = new SseStream($this->config('endpoint', static::DEFAULT_ENDPOINT), $headers, $payload, (int)$this->config('timeout', 120));
		yield from $stream->stream(function (array $event): Generator {
			$type = $event['type'] ?? null;

			// handle message start event
			if ($type === 'message_start') {
				yield Chunk::streamStart($event);
				return;
			}

			// handle content block start (beginning of text output)
			if ($type === 'content_block_start') {
				$contentBlock = $event['content_block'] ?? [];
				if (($contentBlock['type'] ?? null) === 'text') {
					yield Chunk::textStart($event);
				}
				return;
			}

			// handle content block delta (text chunks)
			if ($type === 'content_block_delta') {
				$delta = $event['delta'] ?? [];
				if (($delta['type'] ?? null) === 'text_delta') {
					$text = $delta['text'] ?? '';
					if ($text !== '') {
						yield Chunk::textDelta($text, $event);
					}
				}
				return;
			}

			// handle content block stop (end of text block)
			if ($type === 'content_block_stop') {
				yield Chunk::textComplete($event);
				return;
			}

			// handle message stop (end of stream)
			if ($type === 'message_stop') {
				yield Chunk::streamEnd($event);
				return;
			}

			// handle ping events (keep-alive)
			if ($type === 'ping') {
				// ignore ping events
				return;
			}

			// handle error events
			if ($type === 'error') {
				$error = $event['error'] ?? [];
				$message = $error['message'] ?? 'Unknown Anthropic streaming error.';
				yield Chunk::error($message, $event);
				return;
			}

			// handle message delta (contains usage info)
			if ($type === 'message_delta') {
				// we could extract usage info here if needed
				return;
			}
		});
	}
}