<?php

namespace DeliciousBrains\WPMDB\Common;

use DeliciousBrains\WPMDB\Common\Filesystem\Filesystem;
use DeliciousBrains\WPMDB\Common\Migration\MigrationHelper;
use DeliciousBrains\WPMDB\Common\Util\Util;
use WP_Error;

class Debug {
	const FILE_PREFIX = 'wpmdb-debug-';
	const FALLBACK_ID = 'migration-id-unknown';

	public function __construct() {
		add_action( 'wpmdb_after_finalize_migration', [ $this, 'maybe_delete' ], 10, 2 );
		add_action( 'wpmdb_remote_finalize', [ $this, 'maybe_delete' ], 10, 2 );
		add_action( 'wpmdb_deactivate_plugin', [ $this, 'delete_all' ], 99 );
	}

	/**
	 * Get the filename for logging debug info.
	 *
	 * @param string $migration_id Optionally get filename for a specific migration, default current migration.
	 *
	 * @return false|string
	 */
	private static function get_debug_log_path( $migration_id = '' ) {
		if ( empty( $migration_id ) || ! is_string( $migration_id ) ) {
			$migration_id = MigrationHelper::get_current_migration_id();
		}

		if ( empty( $migration_id ) ) {
			$migration_id = self::FALLBACK_ID;
		}

		$dir = Filesystem::get_upload_info();

		if ( ! is_string( $dir ) || empty( $dir ) || ! is_dir( $dir ) ) {
			return false;
		}

		$role     = Util::is_source() ? 'src' : 'dst';
		$filename = trailingslashit( $dir ) . self::FILE_PREFIX . $role . '-' . $migration_id . '.log';

		return $filename;
	}

	/**
	 * Write a formatted line to the file path.
	 *
	 * @param string $file
	 * @param string $line
	 *
	 * @return bool
	 */
	private static function write( $file, $line ) {
		if ( empty( $file ) || empty( $line ) ) {
			return false;
		}

		$resource = static::open_truncated_log( $file );

		if ( ! is_resource( $resource ) ) {
			return false;
		}

		$line   = static::line_prefix() . trim( $line ) . PHP_EOL;
		$result = fwrite( $resource, $line );

		fclose( $resource );

		return false !== $result;
	}

	/**
	 * Get log line prefix.
	 *
	 * @return string
	 */
	private static function line_prefix() {
		return '[' . date( 'c' ) . '] ';
	}

	/**
	 * Get file resource for file name, maybe truncated if it's got a little too large.
	 *
	 * @param string $file
	 *
	 * @return false|resource
	 */
	private static function open_truncated_log( $file ) {
		$resource = fopen( $file, 'a+' );

		if ( ! is_resource( $resource ) ) {
			return false;
		}

		$stat = fstat( $resource );

		// If the file has got bigger than we'd like, we'll proceed to trim it down, otherwise we're done here.
		if (
			empty( $stat['size'] ) ||
			max( 10000, (int) apply_filters( 'wpmdb_max_debug_log_bytes', 100000000 ) ) > $stat['size']
		) {
			return $resource;
		}

		// For speed and code sanity we'll trim the file down to a sensible number of lines rather than bytes.
		// There'll be an extra truncate marker line added at the beginning, so line count is for retained lines.
		$lines       = max( 10, (int) apply_filters( 'wpmdb_max_debug_log_lines', 100000 ) );
		$linecounter = $lines;
		$pos         = -strlen( PHP_EOL );
		$beginning   = false;
		$text        = array();

		// Going from end to beginning, collect lines until we hit our limit.
		while ( $linecounter > 0 ) {
			$char = "_";
			while ( $char != PHP_EOL ) {
				if ( fseek( $resource, $pos, SEEK_END ) == -1 ) {
					$beginning = true;
					break;
				}
				$char = fgetc( $resource );
				$pos--;
			}

			$linecounter--;

			if ( $beginning ) {
				rewind( $resource );
			}

			$line = fgets( $resource );

			// Found previous truncate point, bail.
			if ( false !== strpos( $line, '--- WPMDB DEBUG LOG TRUNCATED ---' ) ) {
				break;
			}

			$text[] = $line;

			if ( $beginning ) {
				break;
			}
		}
		fclose( $resource );

		$text[] = static::line_prefix() . '--- WPMDB DEBUG LOG TRUNCATED ---' . PHP_EOL;

		$result = file_put_contents( $file, array_reverse( $text ) );

		if ( false === $result ) {
			return false;
		}

		return fopen( $file, 'a+' );
	}

	/**
	 * Delete the file for logging debug info.
	 *
	 * @param string $migration_id Optionally delete specific migration's log file.
	 *
	 * @return bool
	 */
	private static function delete( $migration_id = '' ) {
		$file = static::get_debug_log_path();

		if ( false === $file || ! is_string( $file ) ) {
			return false;
		}

		if ( ! is_writable( $file ) ) {
			return false;
		}

		return unlink( $file );
	}

	/**
	 * Log some information to our custom temporary debug log file.
	 *
	 * @param string|mixed|WP_Error $message
	 *
	 * @return void
	 */
	public static function log( $message ) {
		static $bad_file = false;

		if ( $bad_file || empty( $message ) ) {
			return;
		}

		$enabled = apply_filters( 'wpmdb_enable_debug_log', false );

		if ( empty( $enabled ) || ! is_bool( $enabled ) ) {
			return;
		}

		$file = static::get_debug_log_path();

		if ( false === $file || ! is_string( $file ) ) {
			$bad_file = true;

			return;
		}

		if ( is_wp_error( $message ) ) {
			$line   = 'ERROR CODE: ' . $message->get_error_code();
			$result = static::write( $file, $line );
			if ( false === $result ) {
				return;
			}

			$line   = 'ERROR MESSAGE: ' . $message->get_error_message();
			$result = static::write( $file, $line );
			if ( false === $result ) {
				return;
			}

			$line = 'ERROR DATA: ' . print_r( $message->get_error_data(), true );
			static::write( $file, $line );

			return;
		}

		$line = is_string( $message ) ? $message : print_r( $message, true );
		static::write( $file, $line );
	}

	/**
	 * Delete debug log file if migration successful.
	 *
	 * @param array|WP_Error      $state_data
	 * @param array|bool|WP_Error $result
	 *
	 * @return void
	 */
	public function maybe_delete( $state_data, $result ) {
		if ( is_wp_error( $state_data ) || is_wp_error( $result ) ) {
			return;
		}

		if ( apply_filters( 'wpmdb_retain_debug_log', false ) ) {
			return;
		}

		static::delete();
	}

	/**
	 * Delete all debug log files.
	 *
	 * @return void
	 */
	public static function delete_all() {
		if ( apply_filters( 'wpmdb_retain_debug_log', false ) ) {
			return;
		}

		$dir = Filesystem::get_upload_info();

		if ( ! is_string( $dir ) || empty( $dir ) || ! is_dir( $dir ) ) {
			return;
		}

		$files = scandir( $dir );

		if ( empty( $files ) ) {
			return;
		}

		foreach ( $files as $file ) {
			if ( 0 !== strpos( $file, self::FILE_PREFIX ) || '.log' !== substr( $file, -4 ) ) {
				continue;
			}

			$filepath = trailingslashit( $dir ) . $file;

			if ( is_dir( $filepath ) || is_link( $filepath ) || ! is_writable( $filepath ) ) {
				continue;
			}

			@unlink( $filepath );
		}
	}
}