<?php
declare(strict_types=1);

use Exception;

class WpPluginChecker {
    private string $slug;
    private string $version;
    private array $plugin_api_data;
    private array $errors = array();

    public function __construct( string $slug, string $version ) {
        $this->slug    = $slug;
        $this->version = $version;

        try {
            $this->plugin_api_data = $this->fetch_plugin_data_from_api( $this->slug );
            $this->check_plugin();
        } catch ( Exception $e ) {
            $this->errors['api'] = $e->getMessage();
        }
    }

    /**
     * Fetches plugin data from the WordPress API based on the provided slug name.
     *
     * @param string $slug_name The slug name of the plugin.
     * @return array The plugin data retrieved from the API.
     * @throws Exception If the plugin API returns an invalid response or no/invalid plugin data.
     */
    private function fetch_plugin_data_from_api( string $slug_name ): array {
        $plugin_data = wp_remote_get( 'https://api.wordpress.org/plugins/info/1.0/' . $slug_name . '.json' );

        $response = wp_remote_retrieve_response_code( $plugin_data );

        if ( $response !== 200 ) {
            throw new Exception( 'The plugin API returned an invalid response' );
        }

        $plugin_data_body = wp_remote_retrieve_body( $plugin_data );
        $plugin_data      = json_decode( $plugin_data_body, true );

        if ( ! isset( $plugin_data['slug'] ) ) {
            throw new Exception( 'The plugin API returned no or invalid plugin data' );
        }

        return $plugin_data;
    }

    /**
     * Retrieves the current version of the plugin from the API data.
     *
     * @return string The current version of the plugin.
     */
    private function get_current_version_from_api(): string {
        return $this->plugin_api_data['version'] ?? null;
    }

    /**
     * Fetches and sorts the numeric versions from the plugin API data.
     *
     * @return array The sorted numeric versions.
     */
    private function fetch_and_sort_numeric_versions_from_api(): array {
        $plugin_api_data = $this->plugin_api_data;

        if ( isset( $plugin_api_data['error'] ) && ! empty( $plugin_api_data['error'] ) ) {
            return array();
        }

        $versions = $plugin_api_data['versions'];

        $versions = array_filter(
			$versions,
			function ( $key ) {
				return preg_match( '/^\d+(\.\d+)*$/', $key );
			},
			ARRAY_FILTER_USE_KEY
		);

		uksort(
			$versions,
			function ( $a, $b ) {
				return version_compare( $b, $a );
			}
		);

		return $versions;
	}

	/**
	 * Checks if the plugin slug matches the slug from the WordPress plugin API.
	 *
	 * @return bool Returns true if the slugs match, otherwise throws an Exception.
	 * @throws Exception Throws an exception if the installed plugin slug is different from the WordPress plugin API slug.
	 */
	private function check_slug_with_api(): bool|Exception {
		$slug            = $this->get_slug();
		$plugin_api_slug = $this->plugin_api_data['slug'] ?? null;

		if ( $slug !== $plugin_api_slug ) {
			throw new Exception( sprintf( 'The installed plugin slug is different from the WordPress plugin API which can lead to critical issues.', $slug, $plugin_api_slug ) );
		}

		return true;
	}

	/**
	 * Checks the current version of the plugin against the latest version available in the API.
	 *
	 * @return bool|Exception Returns true if the current version is up to date, otherwise throws an Exception.
	 * @throws Exception If no plugin versions are found or if the current version is higher than the expected latest version.
	 */
	private function check_version_in_api(): bool|Exception {
		$current_version = $this->get_current_version_from_api();

		$plugin_versions = $this->fetch_and_sort_numeric_versions_from_api();

		if ( ! $plugin_versions ) {
			throw new Exception( 'No plugin versions found' );
		}

		$latest_version = array_key_first( $plugin_versions );

		if ( $current_version < $latest_version ) {
			throw new Exception( sprintf( 'The latest plugin version is higher than the stable plugin version from the WordPress API (%s <-> %s). Please contact the plugin developer about this issue.', $latest_version, $current_version ) );
		}

		return true;
	}

	/**
	 * Checks the installed version of the plugin against the current version from the API.
	 *
	 * @return bool|Exception Returns true if the installed version is up to date, otherwise throws an Exception.
	 * @throws Exception If no plugin version is found or if the installed version is higher than the expected version.
	 */
	private function check_installed_version_with_api(): bool|Exception {
		$installed_version      = $this->version;
		$current_plugin_version = $this->get_current_version_from_api();

		if ( ! $current_plugin_version ) {
			throw new Exception( 'No plugin version found' );
		}

		if ( ! $installed_version ) {
			throw new Exception( 'No installed plugin version found' );
		}

		if ( $installed_version > $current_plugin_version ) {
			throw new Exception( sprintf( 'The installed plugin version is higher than the current version from the WordPress API (%s <-> %s). Please contact the plugin developer about this issue.', esc_attr($installed_version), esc_attr($current_plugin_version) ) );
		}

		return true;
	}

	/**
	 * Adds an error message to the specified key in the errors array.
	 *
	 * @param string $key The key to add the error message to.
	 * @param string $error The error message to add.
	 * @return void
	 */
	private function add_error( $key, $error ) {
		$this->errors[ $key ][] = $error;
	}

	/**
	 * Checks the plugin by performing various checks such as checking the plugin slug with the API,
	 * checking the plugin version in the API, and checking the installed version of the plugin with the API.
	 *
	 * @return void
	 */
	private function check_plugin(): void {
		try {
			$this->check_slug_with_api();
		} catch ( Exception $e ) {
			$this->add_error( 'api', $e->getMessage() );
		}

		try {
			$this->check_version_in_api();
		} catch ( Exception $e ) {
			$this->add_error( 'api', $e->getMessage() );
		}

		try {
			$this->check_installed_version_with_api();
		} catch ( Exception $e ) {
			$this->add_error( 'wp', $e->getMessage() );
		}
	}

	/**
	 * Retrieves the slug of the plugin.
	 *
	 * @return string The slug of the plugin.
	 */
	public function get_slug(): string {
		return $this->slug;
	}

	/**
	 * Get the version of the plugin.
	 *
	 * @return string The version of the plugin.
	 */
	public function get_version(): string {
		return $this->version;
	}

	/**
	 * Returns the errors array.
	 *
	 * @return array The errors array.
	 */
	public function get_errors(): array {
		return $this->errors;
	}
}