<?php
/**
 * Slack 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 Slack channel.
 *
 * Uses an incoming webhook URL, which carries the channel and the permission in
 * the URL itself — so there is no token to store and no OAuth to complete.
 *
 * @since 1.0.0
 */
final class Slack extends Integration {

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

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

	/**
	 * Returns the sentence explaining what to fill in.
	 */
	public function description(): string {
		return __( 'Create an incoming webhook in your Slack workspace and paste its URL. The channel is part of the URL, so nothing else is needed.', '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( __( 'Incoming webhook URL', 'devplugins-custom-form-builder' ), 'https://hooks.slack.com/services/…' ),
			array(
				'key'         => 'title',
				'type'        => 'text',
				'label'       => __( 'Message heading', 'devplugins-custom-form-builder' ),
				'description' => __( 'Leave empty to use the form title.', 'devplugins-custom-form-builder' ),
			),
		);
	}

	/**
	 * Builds the body sent to Slack.
	 *
	 * @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 {
		$heading = $this->option( $config, 'title' );
		$heading = '' !== $heading ? $heading : $context->form()->title();

		$blocks = array(
			array(
				'type' => 'header',
				'text' => array(
					'type' => 'plain_text',
					'text' => $this->truncate( $heading, 150 ),
				),
			),
		);

		/*
		 * Slack allows ten fields per section and truncates a field at 2000
		 * characters, so the answers are chunked rather than sent as one block
		 * that the API would refuse outright.
		 */
		foreach ( array_chunk( $this->pairs( $context ), 10, true ) as $chunk ) {
			$fields = array();

			foreach ( $chunk as $label => $value ) {
				$fields[] = array(
					'type' => 'mrkdwn',
					'text' => '*' . $this->escape( (string) $label ) . "*\n" . $this->escape( $this->truncate( $value, 1800 ) ),
				);
			}

			$blocks[] = array(
				'type'   => 'section',
				'fields' => $fields,
			);
		}

		$url = $context->entry_url();

		if ( '' !== $url ) {
			$blocks[] = array(
				'type'     => 'context',
				'elements' => array(
					array(
						'type' => 'mrkdwn',
						'text' => '<' . $url . '|' . __( 'View the entry', 'devplugins-custom-form-builder' ) . '>',
					),
				),
			);
		}

		return array(
			// Sent alongside the blocks because it is what a notification preview
			// and a screen reader announce; blocks alone leave both empty.
			'text'   => $heading,
			'blocks' => $blocks,
		);
	}

	/**
	 * Returns the answers, keyed by label, with the empty ones dropped.
	 *
	 * @param IntegrationContext $context Submission being delivered.
	 *
	 * @return array<string, string> Answers keyed by label.
	 */
	private function pairs( IntegrationContext $context ): array {
		$pairs = array_filter(
			$context->labelled(),
			static fn( string $value ): bool => '' !== trim( $value )
		);

		return array() === $pairs
			? array( __( 'Submission', 'devplugins-custom-form-builder' ) => __( 'No answers were recorded.', 'devplugins-custom-form-builder' ) )
			: $pairs;
	}

	/**
	 * Escapes the three characters Slack treats as markup.
	 *
	 * @param string $text Raw text.
	 */
	private function escape( string $text ): string {
		return str_replace( array( '&', '<', '>' ), array( '&amp;', '&lt;', '&gt;' ), $text );
	}

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