<?php
/**
 * Validator — checks generated files against specification requirements.
 *
 * @package AIDF
 * @since   1.0.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Validates AI Discovery Files for spec compliance and cross-file consistency.
 */
class AIDF_Validator {

	/**
	 * Validate a single file type.
	 *
	 * @param  string $file_slug File type slug.
	 * @return array<string, mixed> Validation result with 'valid', 'errors', 'warnings'.
	 */
	public static function validate( $file_slug ) {
		$content = AIDF_Generator::generate( $file_slug );

		if ( false === $content ) {
			return array(
				'valid'    => false,
				'errors'   => array( __( 'File could not be generated.', 'ai-discovery-files' ) ),
				'warnings' => array(),
			);
		}

		$validators = array(
			'llms-txt'      => 'validate_llms_txt',
			'ai-txt'        => 'validate_ai_txt',
			'ai-json'       => 'validate_ai_json',
			'identity-json' => 'validate_identity_json',
		);

		if ( isset( $validators[ $file_slug ] ) ) {
			return self::{$validators[ $file_slug ]}( $content );
		}

		return array(
			'valid'    => true,
			'errors'   => array(),
			'warnings' => array(),
		);
	}

	/**
	 * Validate all active files and check cross-file consistency.
	 *
	 * @return array<string, array<string, mixed>>
	 */
	public static function validate_all() {
		$settings     = AIDF_Plugin::get_settings();
		$active_files = isset( $settings['active_files'] ) ? (array) $settings['active_files'] : array();
		$results      = array();

		foreach ( $active_files as $slug ) {
			$results[ $slug ] = self::validate( $slug );
		}

		$results['_consistency'] = self::validate_consistency( $active_files );

		return $results;
	}

	/**
	 * Validate llms.txt (ADF-001).
	 *
	 * @param  string $content File content.
	 * @return array<string, mixed>
	 */
	private static function validate_llms_txt( $content ) {
		$errors   = array();
		$warnings = array();

		// Must have an H1 title.
		if ( ! preg_match( '/^# .+$/m', $content ) ) {
			$errors[] = __( 'llms.txt must begin with an H1 heading (# Title).', 'ai-discovery-files' );
		}

		// Should have a blockquote description.
		if ( false === strpos( $content, '> ' ) ) {
			$warnings[] = __( 'llms.txt should include a blockquote description (> text).', 'ai-discovery-files' );
		}

		// Should have a contact section.
		if ( false === stripos( $content, '## Contact' ) ) {
			$warnings[] = __( 'llms.txt should include a Contact section.', 'ai-discovery-files' );
		}

		return array(
			'valid'    => empty( $errors ),
			'errors'   => $errors,
			'warnings' => $warnings,
		);
	}

	/**
	 * Validate ai.txt (ADF-004).
	 *
	 * @param  string $content File content.
	 * @return array<string, mixed>
	 */
	private static function validate_ai_txt( $content ) {
		$errors   = array();
		$warnings = array();

		if ( false === stripos( $content, 'AI Usage' ) && false === stripos( $content, 'Usage Policy' ) ) {
			$errors[] = __( 'ai.txt must include an AI usage policy declaration.', 'ai-discovery-files' );
		}

		return array(
			'valid'    => empty( $errors ),
			'errors'   => $errors,
			'warnings' => $warnings,
		);
	}

	/**
	 * Validate ai.json (ADF-005).
	 *
	 * @param  string $content File content.
	 * @return array<string, mixed>
	 */
	private static function validate_ai_json( $content ) {
		$errors   = array();
		$warnings = array();

		$decoded = json_decode( $content, true );

		if ( null === $decoded ) {
			$errors[] = __( 'ai.json contains invalid JSON.', 'ai-discovery-files' );
			return array(
				'valid'    => false,
				'errors'   => $errors,
				'warnings' => $warnings,
			);
		}

		if ( ! isset( $decoded['permissions'] ) ) {
			$errors[] = __( 'ai.json must contain a "permissions" object.', 'ai-discovery-files' );
		}

		return array(
			'valid'    => empty( $errors ),
			'errors'   => $errors,
			'warnings' => $warnings,
		);
	}

	/**
	 * Validate identity.json (ADF-006).
	 *
	 * @param  string $content File content.
	 * @return array<string, mixed>
	 */
	private static function validate_identity_json( $content ) {
		$errors   = array();
		$warnings = array();

		$decoded = json_decode( $content, true );

		if ( null === $decoded ) {
			$errors[] = __( 'identity.json contains invalid JSON.', 'ai-discovery-files' );
			return array(
				'valid'    => false,
				'errors'   => $errors,
				'warnings' => $warnings,
			);
		}

		if ( ! isset( $decoded['name'] ) || empty( $decoded['name'] ) ) {
			$errors[] = __( 'identity.json must contain a "name" field.', 'ai-discovery-files' );
		}

		if ( ! isset( $decoded['url'] ) || empty( $decoded['url'] ) ) {
			$errors[] = __( 'identity.json must contain a "url" field.', 'ai-discovery-files' );
		}

		return array(
			'valid'    => empty( $errors ),
			'errors'   => $errors,
			'warnings' => $warnings,
		);
	}

	/**
	 * Validate cross-file consistency.
	 *
	 * @param  array<int, string> $active_files Active file slugs.
	 * @return array<string, mixed>
	 */
	private static function validate_consistency( $active_files ) {
		$warnings = array();
		$settings = AIDF_Plugin::get_settings();
		$name     = ! empty( $settings['business_name'] ) ? $settings['business_name'] : get_bloginfo( 'name' );

		// Check essential tier.
		if ( ! in_array( 'llms-txt', $active_files, true ) ) {
			$warnings[] = __( 'llms.txt (Essential tier) is not enabled — this is the most important AI Discovery File.', 'ai-discovery-files' );
		}

		if ( ! in_array( 'ai-txt', $active_files, true ) ) {
			$warnings[] = __( 'ai.txt (Essential tier) is not enabled — AI systems need to know your usage permissions.', 'ai-discovery-files' );
		}

		// If ai-json is active, ai-txt should be too.
		if ( in_array( 'ai-json', $active_files, true ) && ! in_array( 'ai-txt', $active_files, true ) ) {
			$warnings[] = __( 'ai.json is enabled without ai.txt — both should be active for consistency.', 'ai-discovery-files' );
		}

		// Check that business name is set.
		if ( empty( $name ) ) {
			$warnings[] = __( 'No business name configured — this is required for most AI Discovery Files.', 'ai-discovery-files' );
		}

		return array(
			'valid'    => empty( $warnings ),
			'errors'   => array(),
			'warnings' => $warnings,
		);
	}

	/**
	 * Get the overall status for a file type.
	 *
	 * @param  string $file_slug File type slug.
	 * @return string 'active', 'inactive', 'conflict', or 'error'.
	 */
	public static function get_status( $file_slug ) {
		$settings     = AIDF_Plugin::get_settings();
		$active_files = isset( $settings['active_files'] ) ? (array) $settings['active_files'] : array();

		if ( ! in_array( $file_slug, $active_files, true ) ) {
			return 'inactive';
		}

		if ( AIDF_Server::physical_file_exists( $file_slug ) ) {
			return 'conflict';
		}

		$validation = self::validate( $file_slug );

		if ( ! $validation['valid'] ) {
			return 'error';
		}

		return 'active';
	}
}