<?php

namespace AIContentWriter;

defined( 'ABSPATH' ) || exit; // Exit if accessed directly.

/**
 * Handles REST API endpoints for the plugin.
 *
 * @since 2.2.0
 * @package AIContentWriter
 */
class RestAPI {

	/**
	 * REST namespace.
	 *
	 * @var string
	 */
	const REST_NAMESPACE = 'aicw/v1';

	/**
	 * Constructor.
	 */
	public function __construct() {
		add_action( 'rest_api_init', array( $this, 'register_routes' ) );
	}

	/**
	 * Register REST API routes.
	 *
	 * @since 2.2.0
	 * @return void
	 */
	public function register_routes() {
		register_rest_route(
			self::REST_NAMESPACE,
			'/generateContent',
			array(
				'methods'             => 'POST',
				'callback'            => array( $this, 'handle_generate_content' ),
				'permission_callback' => array( $this, 'check_permission' ),
				'args'                => array(
					'mode'         => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => 'generate',
						'enum'              => array( 'generate', 'modify' ),
						'sanitize_callback' => 'sanitize_key',
					),
					'content_type' => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => 'paragraph',
						'sanitize_callback' => 'sanitize_key',
					),
					'topic'        => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => '',
						'sanitize_callback' => 'sanitize_text_field',
					),
					'instructions' => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => '',
						'sanitize_callback' => 'sanitize_textarea_field',
					),
					'selection'    => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => '',
						'sanitize_callback' => 'wp_kses_post',
					),
					'tone'         => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => '',
						'sanitize_callback' => 'sanitize_key',
					),
					'length'       => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => '',
						'sanitize_callback' => 'sanitize_key',
					),
					'language'     => array(
						'type'              => 'string',
						'required'          => false,
						'default'           => '',
						'sanitize_callback' => 'sanitize_text_field',
					),
				),
			)
		);
	}

	/**
	 * Permission callback for the content generation endpoint.
	 *
	 * @param \WP_REST_Request $request Request.
	 *
	 * @since 2.2.0
	 * @return bool|\WP_Error
	 */
	public function check_permission( \WP_REST_Request $request ) {
		if ( ! current_user_can( 'edit_posts' ) ) {
			return new \WP_Error(
				'rest_forbidden',
				__( 'You do not have permission to generate content.', 'ai-content-writer' ),
				array( 'status' => rest_authorization_required_code() )
			);
		}

		$mode      = (string) $request->get_param( 'mode' );
		$topic     = trim( (string) $request->get_param( 'topic' ) );
		$selection = trim( wp_strip_all_tags( (string) $request->get_param( 'selection' ) ) );

		if ( 'modify' === $mode && '' === $selection ) {
			return new \WP_Error(
				'rest_invalid_param',
				__( 'Selected text is required to modify content.', 'ai-content-writer' ),
				array( 'status' => 400 )
			);
		}

		if ( 'generate' === $mode && '' === $topic ) {
			return new \WP_Error(
				'rest_invalid_param',
				__( 'A topic or set of keywords is required to generate content.', 'ai-content-writer' ),
				array( 'status' => 400 )
			);
		}

		return true;
	}

	/**
	 * Handle the content generation request.
	 *
	 * @param \WP_REST_Request $request The REST request object.
	 *
	 * @since 2.2.0
	 * @return \WP_REST_Response|\WP_Error The REST response or error.
	 */
	public function handle_generate_content( \WP_REST_Request $request ) {
		$api_model = get_option( 'aicw_api_model' );
		$provider  = aicw_get_ai_provider( $api_model );

		if ( ! $provider ) {
			return new \WP_Error(
				'aicw_invalid_provider',
				__( 'No AI provider is configured. Please choose Gemini or ChatGPT on the settings page.', 'ai-content-writer' ),
				array( 'status' => 400 )
			);
		}

		$prompt = $this->build_prompt(
			(string) $request->get_param( 'mode' ),
			(string) $request->get_param( 'content_type' ),
			(string) $request->get_param( 'topic' ),
			(string) $request->get_param( 'instructions' ),
			wp_strip_all_tags( (string) $request->get_param( 'selection' ) ),
			(string) $request->get_param( 'tone' ),
			(string) $request->get_param( 'length' ),
			(string) $request->get_param( 'language' )
		);

		$raw = $this->call_provider( $provider, $prompt );

		if ( is_wp_error( $raw ) ) {
			return $raw;
		}

		$cleaned   = $this->strip_code_fences( $raw );
		$converted = aicw_convert_openai_markdown_to_html( $cleaned );

		return rest_ensure_response(
			array(
				'text' => $cleaned,
				'html' => isset( $converted['content'] ) ? $converted['content'] : $cleaned,
			)
		);
	}

	/**
	 * Build the prompt sent to the AI provider.
	 *
	 * @param string $mode         Action mode.
	 * @param string $content_type Content type.
	 * @param string $topic        Topic / keywords.
	 * @param string $instructions Extra free-form instructions.
	 * @param string $selection    Currently selected text (modify mode only).
	 * @param string $tone         Optional tone preset.
	 * @param string $length       Optional length preset.
	 * @param string $language     Optional output language.
	 *
	 * @since 2.2.0
	 * @return string
	 */
	protected function build_prompt( $mode, $content_type, $topic, $instructions, $selection, $tone, $length, $language = '' ) {
		$length_map = array(
			'short'  => '50-100 words',
			'medium' => '150-300 words',
			'long'   => '500-800 words',
		);

		$tone_line     = '' !== $tone ? sprintf( 'Use a %s tone.', $tone ) : '';
		$length_line   = isset( $length_map[ $length ] ) ? sprintf( 'Aim for roughly %s.', $length_map[ $length ] ) : '';
		$language_line = '' !== $language && array_key_exists( $language, aicw_get_languages() ) ? sprintf( 'Write in %s.', $language ) : '';
		$extra_line    = '' !== trim( $instructions ) ? sprintf( "Additional instructions: %s", $instructions ) : '';

		$type_labels = array(
			'paragraph' => 'a single well-written paragraph',
			'article'   => 'a full article with H2/H3 markdown headings, intro, body sections, and conclusion',
		);

		$type_label = isset( $type_labels[ $content_type ] ) ? $type_labels[ $content_type ] : $type_labels['paragraph'];

		switch ( $mode ) {
			case 'modify':
				$base = sprintf(
					"Rewrite the following text based on these instructions. Preserve markdown formatting where useful and return only the rewritten text — no preface, no explanation.\n\nOriginal text:\n%s",
					$selection
				);
				break;

			case 'generate':
			default:
				$base = sprintf(
					"Write %s about: %s.\nReturn only the requested content in markdown — no preface, no explanation, no surrounding code fences.",
					$type_label,
					'' !== $topic ? $topic : 'the topic provided in the instructions'
				);
				break;
		}

		return trim(
			implode(
				"\n\n",
				array_filter(
					array( $base, $tone_line, $length_line, $language_line, $extra_line )
				)
			)
		);
	}

	/**
	 * Call the given provider and return the generated text (or WP_Error).
	 *
	 * @param \AIContentWriter\Services\ProviderInterface $provider The AI provider.
	 * @param string                                      $prompt   The full prompt string.
	 *
	 * @since 2.2.0
	 * @return string|\WP_Error
	 */
	protected function call_provider( $provider, $prompt ) {
		if ( ! $provider->is_configured() ) {
			return new \WP_Error(
				'aicw_provider_not_configured',
				sprintf(
					/* translators: %s: Provider label. */
					__( 'No API key configured for %s. Please add your API key on the API settings page.', 'ai-content-writer' ),
					$provider->get_label()
				),
				array( 'status' => 400 )
			);
		}

		return $provider->generate( $prompt );
	}

	/**
	 * Strip ```language ... ``` code fences that some models wrap responses in.
	 *
	 * @param string $text Raw model output.
	 *
	 * @since 2.2.0
	 * @return string
	 */
	protected function strip_code_fences( $text ) {
		$text = trim( (string) $text );
		if ( preg_match( '/^```[a-zA-Z0-9_-]*\s*\n(.*)\n```$/s', $text, $m ) ) {
			return trim( $m[1] );
		}
		return $text;
	}
}