<?php
/**
 * Discover models available to direct API credentials.
 *
 * @package AISupportAssistant\Providers
 */

namespace AISupportAssistant\Providers;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class ModelDiscovery
 */
class ModelDiscovery {

	/**
	 * Fetch chat and embedding models accessible with an API key.
	 *
	 * @param string $provider Provider identifier.
	 * @param string $api_key  Provider API key.
	 * @return array
	 * @throws \RuntimeException If the provider request fails.
	 */
	public static function fetch_models( string $provider, string $api_key ): array {
		if ( 'openai' === $provider ) {
			return self::fetch_openai_models( $api_key );
		}

		if ( 'gemini' === $provider ) {
			return self::fetch_gemini_models( $api_key );
		}

		throw new \RuntimeException( esc_html__( 'Model discovery is supported for OpenAI and Gemini API providers only.', 'ai-support-assistant' ) );
	}

	/**
	 * Fetch available OpenAI chat and embedding models.
	 *
	 * @param string $api_key Provider API key.
	 * @return array
	 * @throws \RuntimeException If the provider request fails.
	 */
	private static function fetch_openai_models( string $api_key ): array {
		$models = array(
			'chat'      => array(),
			'embedding' => array(),
		);
		$cursor = '';

		for ( $page = 0; $page < 20; $page++ ) {
			$url      = add_query_arg(
				array_filter(
					array(
						'limit' => 100,
						'after' => $cursor,
					),
					static function ( $value ) {
						return '' !== $value;
					}
				),
				\AISupportAssistant\Config\Urls::OPENAI_MODELS
			);
			$response = wp_safe_remote_get(
				$url,
				array(
					'headers'             => array( 'Authorization' => 'Bearer ' . $api_key ),
					'timeout'             => 20,
					'limit_response_size' => 1048576,
				)
			);

			$payload = self::get_payload( $response, $api_key, 'OpenAI' );
			if ( empty( $payload['data'] ) || ! is_array( $payload['data'] ) ) {
				break;
			}

			foreach ( $payload['data'] as $model ) {
				if ( empty( $model['id'] ) || ! is_string( $model['id'] ) ) {
					continue;
				}

				$model_id = $model['id'];
				if ( self::is_openai_chat_model( $model_id ) ) {
					$models['chat'][] = $model_id;
				} elseif ( 0 === strpos( $model_id, 'text-embedding-' ) ) {
					$models['embedding'][] = $model_id;
				}
			}

			if ( empty( $payload['has_more'] ) ) {
				break;
			}
			if ( 19 === $page ) {
				throw new \RuntimeException( esc_html__( 'OpenAI returned more model pages than can be safely loaded at once.', 'ai-support-assistant' ) );
			}

			$last_model  = end( $payload['data'] );
			$next_cursor = ! empty( $payload['last_id'] ) ? $payload['last_id'] : ( is_array( $last_model ) && isset( $last_model['id'] ) ? $last_model['id'] : '' );
			if ( ! is_string( $next_cursor ) || '' === $next_cursor || $next_cursor === $cursor ) {
				throw new \RuntimeException( esc_html__( 'OpenAI returned an incomplete model list.', 'ai-support-assistant' ) );
			}
			$cursor = $next_cursor;
		}

		self::sort_models( $models, array( 'gpt-4o-mini', 'text-embedding-3-small' ) );
		return $models;
	}

	/**
	 * Fetch available Gemini chat and embedding models.
	 *
	 * @param string $api_key Provider API key.
	 * @return array
	 * @throws \RuntimeException If the provider request fails.
	 */
	private static function fetch_gemini_models( string $api_key ): array {
		$models     = array(
			'chat'      => array(),
			'embedding' => array(),
		);
		$page_token = '';

		for ( $page = 0; $page < 20; $page++ ) {
			$query = array( 'pageSize' => 100 );
			if ( '' !== $page_token ) {
				$query['pageToken'] = $page_token;
			}
			// phpcs:ignore PluginCheck.CodeAnalysis.AIProvider.DirectIntegration -- The native prompt API does not provide this credential-specific model catalog.
			$url      = add_query_arg( $query, \AISupportAssistant\Config\Urls::GEMINI_MODELS );
			$response = wp_safe_remote_get(
				$url,
				array(
					'headers'             => array( 'x-goog-api-key' => $api_key ),
					'timeout'             => 20,
					'limit_response_size' => 1048576,
				)
			);

			$payload = self::get_payload( $response, $api_key, 'Gemini' );
			if ( ! empty( $payload['models'] ) && is_array( $payload['models'] ) ) {
				foreach ( $payload['models'] as $model ) {
					if ( empty( $model['name'] ) || ! is_string( $model['name'] ) ) {
						continue;
					}

					$model_id = preg_replace( '/^models\//', '', $model['name'] );
					if ( 0 !== strpos( $model_id, 'gemini-' ) || empty( $model['supportedGenerationMethods'] ) || ! is_array( $model['supportedGenerationMethods'] ) ) {
						continue;
					}

					$is_text_chat_model = ! preg_match( '/(?:embedding|audio|transcri|tts|image|live)/i', $model_id );
					if ( $is_text_chat_model && in_array( 'generateContent', $model['supportedGenerationMethods'], true ) ) {
						$models['chat'][] = $model_id;
					}
					if ( in_array( 'embedContent', $model['supportedGenerationMethods'], true ) ) {
						$models['embedding'][] = $model_id;
					}
				}
			}

			if ( empty( $payload['nextPageToken'] ) ) {
				break;
			}
			if ( 19 === $page ) {
				throw new \RuntimeException( esc_html__( 'Gemini returned more model pages than can be safely loaded at once.', 'ai-support-assistant' ) );
			}
			if ( ! is_string( $payload['nextPageToken'] ) || $payload['nextPageToken'] === $page_token ) {
				throw new \RuntimeException( esc_html__( 'Gemini returned an incomplete model list.', 'ai-support-assistant' ) );
			}
			$page_token = $payload['nextPageToken'];
		}

		self::sort_models( $models, array( 'gemini-3.1-flash-lite', 'gemini-embedding-001' ) );
		return $models;
	}

	/**
	 * Request and decode a model-list response.
	 *
	 * @param array|\WP_Error $response Remote response.
	 * @param string          $api_key  API key to redact from errors.
	 * @param string          $provider Provider display name.
	 * @return array
	 * @throws \RuntimeException If the response is invalid or unsuccessful.
	 */
	private static function get_payload( $response, string $api_key, string $provider ): array {
		if ( is_wp_error( $response ) ) {
			$message = str_replace( $api_key, '[redacted]', $response->get_error_message() );
			/* translators: 1: AI provider name, 2: Provider error detail. */
			throw new \RuntimeException( esc_html( sprintf( __( '%1$s model request failed: %2$s', 'ai-support-assistant' ), $provider, $message ) ) );
		}

		$status  = wp_remote_retrieve_response_code( $response );
		$body    = wp_remote_retrieve_body( $response );
		$payload = json_decode( $body, true );
		if ( 200 !== $status ) {
			$message = ! empty( $payload['error']['message'] ) ? $payload['error']['message'] : sprintf( 'HTTP %d', $status );
			$message = str_replace( $api_key, '[redacted]', (string) $message );
			/* translators: 1: AI provider name, 2: Provider error detail. */
			throw new \RuntimeException( esc_html( sprintf( __( '%1$s model request failed: %2$s', 'ai-support-assistant' ), $provider, $message ) ) );
		}

		if ( ! is_array( $payload ) ) {
			/* translators: %s: AI provider name. */
			throw new \RuntimeException( esc_html( sprintf( __( '%s returned an invalid model list.', 'ai-support-assistant' ), $provider ) ) );
		}

		return $payload;
	}

	/**
	 * Check if an OpenAI model ID is compatible with the chat-completions API.
	 *
	 * @param string $model_id Model identifier.
	 * @return bool
	 */
	private static function is_openai_chat_model( string $model_id ): bool {
		if ( ! preg_match( '/^(?:ft:)?gpt-/', $model_id ) && ! preg_match( '/^chatgpt-4o(?:-|$)/', $model_id ) ) {
			return false;
		}

		return ! preg_match( '/(?:audio|realtime|transcri|tts|image|embedding|moderation|search|instruct|codex|whisper|dall-e|sora|(?:^|[-:])pro(?:[-:]|$))/i', $model_id );
	}

	/**
	 * Remove duplicates and put recommended models first.
	 *
	 * @param array $models      Model categories.
	 * @param array $recommended Preferred model for each category.
	 * @return void
	 */
	private static function sort_models( array &$models, array $recommended ): void {
		foreach ( array( 'chat', 'embedding' ) as $index => $type ) {
			$models[ $type ] = array_values( array_unique( $models[ $type ] ) );
			sort( $models[ $type ], SORT_STRING );

			$preferred = $recommended[ $index ];
			if ( in_array( $preferred, $models[ $type ], true ) ) {
				$models[ $type ] = array_merge( array( $preferred ), array_diff( $models[ $type ], array( $preferred ) ) );
			}
		}
	}
}