<?php
/**
 * Failure log.
 *
 * @package AdPix\Analytics
 */

declare( strict_types = 1 );

namespace AdPix\Analytics\Service;

use AdPix\Analytics\Contracts\LoggerInterface;
use AdPix\Analytics\Contracts\SettingsRepositoryInterface;

defined( 'ABSPATH' ) || exit;

/**
 * Keeps the last few failures where the site owner can read them.
 *
 * A misconfigured integration is silent by nature: events simply do not arrive, and the site looks
 * perfectly healthy from the inside. The settings screen shows this log so the answer to "why is
 * nothing coming through" is on the same page as the settings that caused it, rather than in a
 * debug.log the site owner cannot reach.
 */
final class ErrorLog implements LoggerInterface {

	/**
	 * Option holding recent failures.
	 */
	public const OPTION = 'adpix_analytics_log';

	/**
	 * Entries kept. Enough to show a pattern, small enough to stay a cheap option row.
	 */
	private const MAX_ENTRIES = 20;

	/**
	 * @var SettingsRepositoryInterface
	 */
	private $settings;

	/**
	 * @param SettingsRepositoryInterface $settings Configuration source.
	 */
	public function __construct( SettingsRepositoryInterface $settings ) {
		$this->settings = $settings;
	}

	/**
	 * Record a failure.
	 *
	 * @param string              $message Summary.
	 * @param array<string,mixed> $context Structured detail.
	 * @return void
	 */
	public function error( string $message, array $context = array() ): void {
		$entries = $this->entries();

		array_unshift(
			$entries,
			array(
				'time'    => time(),
				'message' => $message,
				'context' => $this->flatten( $context ),
			)
		);

		update_option( self::OPTION, array_slice( $entries, 0, self::MAX_ENTRIES ), false );

		$this->to_debug_log( 'error', $message, $context );
	}

	/**
	 * Record developer detail.
	 *
	 * Never stored in the database — this fires on every successful delivery, and writing an option
	 * row per event would make measurement the most expensive thing the site does.
	 *
	 * @param string              $message Summary.
	 * @param array<string,mixed> $context Structured detail.
	 * @return void
	 */
	public function debug( string $message, array $context = array() ): void {
		if ( ! $this->settings->load()->flag( 'debug' ) ) {
			return;
		}

		$this->to_debug_log( 'debug', $message, $context );
	}

	/**
	 * Recent failures, newest first.
	 *
	 * @return array<int,array<string,mixed>>
	 */
	public function entries(): array {
		$stored = get_option( self::OPTION, array() );

		if ( ! is_array( $stored ) ) {
			return array();
		}

		return array_values( array_filter( $stored, 'is_array' ) );
	}

	/**
	 * Empty the log.
	 *
	 * @return void
	 */
	public function clear(): void {
		delete_option( self::OPTION );
	}

	/**
	 * Reduce a context array to short scalar strings.
	 *
	 * @param array<string,mixed> $context Structured detail.
	 * @return array<string,string>
	 */
	private function flatten( array $context ): array {
		$flat = array();

		foreach ( $context as $key => $value ) {
			if ( ! is_scalar( $value ) ) {
				continue;
			}

			$flat[ sanitize_key( (string) $key ) ] = substr( sanitize_text_field( (string) $value ), 0, 200 );
		}

		return $flat;
	}

	/**
	 * Mirror an entry into the PHP error log when the site is set up to collect one.
	 *
	 * @param string              $level   Level label.
	 * @param string              $message Summary.
	 * @param array<string,mixed> $context Structured detail.
	 * @return void
	 */
	private function to_debug_log( string $level, string $message, array $context ): void {
		if ( ! defined( 'WP_DEBUG' ) || ! WP_DEBUG || ! defined( 'WP_DEBUG_LOG' ) || ! WP_DEBUG_LOG ) {
			return;
		}

		$line = '[AdPix Analytics] ' . strtoupper( $level ) . ': ' . $message;

		if ( array() !== $context ) {
			$encoded = wp_json_encode( $this->flatten( $context ) );
			$line   .= ' ' . ( is_string( $encoded ) ? $encoded : '' );
		}

		// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log -- Guarded by WP_DEBUG_LOG; this is the log the site asked for.
		error_log( $line );
	}
}