<?php
/**
 * Discord integration.
 *
 * @package FormPilot
 * @since   1.0.0
 */

declare( strict_types = 1 );

namespace FormPilot\Integrations\Services;

use FormPilot\Integrations\Integration;
use FormPilot\Integrations\IntegrationContext;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Posts a submission into a Discord channel.
 *
 * @since 1.0.0
 */
final class Discord extends Integration {

	/**
	 * Largest number of fields one embed may carry.
	 */
	private const MAX_FIELDS = 25;

	/**
	 * Returns the slug the configuration is stored under.
	 */
	public function id(): string {
		return 'discord';
	}

	/**
	 * Returns the name shown in the editor.
	 */
	public function label(): string {
		return __( 'Discord', 'devplugins-custom-form-builder' );
	}

	/**
	 * Returns the sentence explaining what to fill in.
	 */
	public function description(): string {
		return __( 'In your Discord server, open Channel Settings, Integrations, Webhooks, and copy the webhook URL.', 'devplugins-custom-form-builder' );
	}

	/**
	 * Returns the settings this integration takes, per form.
	 *
	 * @return array<int, array<string, mixed>> The option definitions.
	 */
	public function options(): array {
		return array(
			$this->url_option( __( 'Webhook URL', 'devplugins-custom-form-builder' ), 'https://discord.com/api/webhooks/…' ),
			array(
				'key'         => 'username',
				'type'        => 'text',
				'label'       => __( 'Post as', 'devplugins-custom-form-builder' ),
				'description' => __( 'Overrides the name the webhook was created with.', 'devplugins-custom-form-builder' ),
			),
		);
	}

	/**
	 * Builds the body sent to Discord.
	 *
	 * @param IntegrationContext   $context Submission being delivered.
	 * @param array<string, mixed> $config  Stored values for the form.
	 *
	 * @return array<string, mixed> The payload.
	 */
	public function payload( IntegrationContext $context, array $config ): array {
		$fields = array();

		foreach ( $context->labelled() as $label => $value ) {
			if ( '' === trim( $value ) ) {
				continue;
			}

			if ( count( $fields ) >= self::MAX_FIELDS ) {
				break;
			}

			$fields[] = array(
				// Discord refuses an embed field with an empty name or value and
				// caps them at 256 and 1024 characters.
				'name'   => $this->truncate( (string) $label, 256 ),
				'value'  => $this->truncate( $this->literal( $value ), 1024 ),
				'inline' => false,
			);
		}

		$embed = array(
			'title'       => $this->truncate( $context->form()->title(), 256 ),
			'description' => array() === $fields ? __( 'No answers were recorded.', 'devplugins-custom-form-builder' ) : '',
			'timestamp'   => gmdate( 'c' ),
			'fields'      => $fields,
		);

		$url = $context->entry_url();

		if ( '' !== $url ) {
			$embed['url'] = $url;
		}

		$payload = array(
			'embeds'           => array( $embed ),

			/*
			 * Nothing a visitor typed may ping anyone. Discord parses @everyone,
			 * @here and role or user mentions out of message content by default,
			 * so an answer of "@everyone" notified the whole server.
			 */
			'allowed_mentions' => array( 'parse' => array() ),
		);

		$username = $this->option( $config, 'username' );

		if ( '' !== $username ) {
			$payload['username'] = $username;
		}

		return $payload;
	}

	/**
	 * Shortens text to a number of characters.
	 *
	 * @param string $text  Raw text.
	 * @param int    $limit Largest length.
	 */
	private function truncate( string $text, int $limit ): string {
		$text = '' === trim( $text ) ? '—' : $text;

		return mb_strlen( $text ) > $limit ? mb_substr( $text, 0, $limit - 1 ) . '…' : $text;
	}

	/**
	 * Escapes Discord markdown in a visitor's answer.
	 *
	 * Embed field values are rendered as markdown, so `[Verify your account](https://…)`
	 * typed into a form became a clickable masked link in the team's channel, and
	 * `@everyone` or `<@&role>` looked like a real mention. Each markdown character is
	 * escaped with a backslash, which Discord shows as the character itself.
	 *
	 * @param string $text Raw answer.
	 */
	private function literal( string $text ): string {
		return (string) preg_replace_callback(
			'/[\\\\*_~`|>\[\]()<@#:-]/',
			static fn( array $found ): string => '\\' . $found[0],
			$text
		);
	}
}