<?php

namespace ChargeForms\Includes;

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

/**
 * Blocks a form save from inserting a permanently-unbuilt field type — shared
 * by every write path that can persist a form's `fields`
 * array (RestApi's create_form/update_form, and includes/mcp/class-mcp-
 * tools.php's create_form/update_form_fields write tools), so an MCP
 * client can't do something the REST API (and by extension the Builder UI)
 * refuses to allow. Deliberately has NO WordPress REST dependency — unlike
 * RestApi, which pulls in register_rest_route()/WP_REST_Request/etc, this
 * only needs core translation functions, so it can be loaded standalone in a
 * lightweight test context (see
 * tests/mcp-tools.test.php) without dragging in the whole REST machinery.
 */
class Field_Type_Gate {

	/**
	 * Field types advertised in the palette with `built: false`
	 * in builtins.js — no canvas preview, no frontend/class-shortcode.php
	 * render path, no submission handling exists for these yet. Blocked
	 * unconditionally: inserting one of these would
	 * save successfully and then render nothing at all on the live form —
	 * silently broken for every visitor, not merely upsold. Keep in sync by
	 * hand with builtins.js's `built: false` entries.
	 */
	const UNBUILT_FIELD_TYPES = [
		'post_selection' => 'Post/CPT Selection',
	];

	public static function reject_locked_fields( array $new_fields, array $existing_fields ) {
		$existing_types = array_column( self::flatten_field_types( $existing_fields ), 'type' );

		foreach ( self::flatten_field_types( $new_fields ) as $field ) {
			$type = $field['type'] ?? '';
			if ( in_array( $type, $existing_types, true ) ) {
				continue; // Grandfathered — already on this form before the check ran.
			}
			if ( isset( self::UNBUILT_FIELD_TYPES[ $type ] ) ) {
				return new \WP_Error(
					'chargeforms_field_not_yet_available',
					/* translators: %s: field type label, e.g. "Ranking Field" */
					sprintf( __( 'The "%s" field is not available yet — remove it before saving.', 'chargeforms' ), self::UNBUILT_FIELD_TYPES[ $type ] ),
					[ 'status' => 403 ]
				);
			}
		}
		return true;
	}

	/**
	 * Validates an AI/MCP-proposed field blueprint without writing anything.
	 * This deliberately returns structured diagnostics so an AI client can
	 * repair a proposal before calling a write tool.
	 */
	public static function validate_blueprint( array $fields, array $existing_fields = [] ) {
		$errors = [];
		$ids    = [];
		$walk   = function ( array $items, $path = '' ) use ( &$walk, &$errors, &$ids ) {
			foreach ( $items as $index => $field ) {
				$location = '' === $path ? (string) $index : $path . '.' . $index;
				if ( ! is_array( $field ) ) {
					$errors[] = [ 'path' => $location, 'code' => 'field_not_object', 'message' => __( 'Each field must be an object.', 'chargeforms' ) ];
					continue;
				}
				$id   = isset( $field['id'] ) ? sanitize_key( $field['id'] ) : '';
				$type = isset( $field['type'] ) ? sanitize_key( $field['type'] ) : '';
				if ( '' === $id || ! preg_match( '/^[a-z][a-z0-9_-]{0,63}$/', $id ) ) {
					$errors[] = [ 'path' => $location . '.id', 'code' => 'invalid_id', 'message' => __( 'Field IDs must start with a letter and contain only lowercase letters, numbers, underscores or hyphens.', 'chargeforms' ) ];
				} elseif ( isset( $ids[ $id ] ) ) {
					$errors[] = [ 'path' => $location . '.id', 'code' => 'duplicate_id', 'message' => sprintf( __( 'Field ID "%s" is used more than once.', 'chargeforms' ), $id ) ];
				} else {
					$ids[ $id ] = true;
				}
				if ( '' === $type ) {
					$errors[] = [ 'path' => $location . '.type', 'code' => 'missing_type', 'message' => __( 'Every field needs a type.', 'chargeforms' ) ];
				}
				if ( ! isset( $field['label'] ) && ! in_array( $type, [ 'row', 'column', 'container', 'section', 'page_break' ], true ) ) {
					$errors[] = [ 'path' => $location . '.label', 'code' => 'missing_label', 'message' => __( 'Input fields need a label.', 'chargeforms' ) ];
				}
				if ( ! empty( $field['children'] ) ) {
					if ( ! is_array( $field['children'] ) ) {
						$errors[] = [ 'path' => $location . '.children', 'code' => 'children_not_array', 'message' => __( 'Nested fields must use a children array.', 'chargeforms' ) ];
					} else {
						$walk( $field['children'], $location . '.children' );
					}
				}
			}
		};
		$walk( $fields );
		$gate = self::reject_locked_fields( $fields, $existing_fields );
		if ( is_wp_error( $gate ) ) {
			$errors[] = [ 'path' => '', 'code' => $gate->get_error_code(), 'message' => $gate->get_error_message() ];
		}
		return [ 'valid' => empty( $errors ), 'field_count' => count( $ids ), 'errors' => $errors ];
	}

	/** Recursively walks a field tree (containers/sections/rows/columns can nest fields) into one flat list — mirrors core/tree.js's flattenFields() on the JS side. */
	private static function flatten_field_types( array $fields ) {
		$flat = [];
		foreach ( $fields as $field ) {
			$flat[] = $field;
			if ( ! empty( $field['children'] ) && is_array( $field['children'] ) ) {
				$flat = array_merge( $flat, self::flatten_field_types( $field['children'] ) );
			}
		}
		return $flat;
	}
}