<?php
// PHP 7.4 compatible. No Composer. No build step. WordPress coding standards.

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

class SLBUILD_SchemaParser {

	/**
	 * Extract and parse the @section JSON schema from a section PHP file.
	 * Uses brace-counting, not regex, to find the JSON boundaries.
	 *
	 * @param string $file_path Absolute path to the section file.
	 * @return array|null Parsed schema array, or null if not found / invalid.
	 */
	public function parse_file( $file_path ) {
		$content = file_get_contents( $file_path );
		if ( false === $content ) {
			return null;
		}

		$marker = '@section';
		$marker_pos = strpos( $content, $marker );
		if ( false === $marker_pos ) {
			return null;
		}

		$json_start = strpos( $content, '{', $marker_pos );
		if ( false === $json_start ) {
			return null;
		}

		$depth   = 0;
		$json_end = -1;
		$length  = strlen( $content );

		for ( $i = $json_start; $i < $length; $i++ ) {
			if ( '{' === $content[ $i ] ) {
				$depth++;
			} elseif ( '}' === $content[ $i ] ) {
				$depth--;
				if ( 0 === $depth ) {
					$json_end = $i;
					break;
				}
			}
		}

		if ( -1 === $json_end ) {
			return null;
		}

		$json   = substr( $content, $json_start, $json_end - $json_start + 1 );
		$schema = json_decode( $json, true );

		if ( null === $schema || JSON_ERROR_NONE !== json_last_error() ) {
			return null;
		}

		return $schema;
	}

	/**
	 * Scan a directory for section PHP files and return slug => schema map.
	 *
	 * @param string $dir Absolute path to the sections directory.
	 * @return array Associative array of section_slug => schema.
	 */
	public function scan_dir( $dir ) {
		$sections = array();

		if ( ! is_dir( $dir ) ) {
			return $sections;
		}

		$files = glob( $dir . '/*.php' );
		if ( ! $files ) {
			return $sections;
		}

		foreach ( $files as $file ) {
			$schema = $this->parse_file( $file );
			if ( null === $schema ) {
				continue;
			}

			$error = $this->validate( $schema );
			if ( true !== $error ) {
				continue;
			}

			$slug              = basename( $file, '.php' );
			$sections[ $slug ] = $schema;
		}

		return $sections;
	}

	/**
	 * Validate a parsed schema array.
	 *
	 * @param array $schema
	 * @return true|string True if valid, error message string if not.
	 */
	public function validate( $schema ) {
		if ( empty( $schema['name'] ) ) {
			return 'Missing required field: name';
		}

		if ( ! isset( $schema['settings'] ) || ! is_array( $schema['settings'] ) ) {
			return 'Missing required field: settings';
		}

		$organizer_types = array( 'header', 'paragraph' );
		foreach ( $schema['settings'] as $i => $setting ) {
			if ( empty( $setting['type'] ) ) {
				return "Setting {$i}: missing type";
			}
			if ( empty( $setting['id'] ) && ! in_array( $setting['type'], $organizer_types, true ) ) {
				return "Setting {$i}: missing id";
			}
		}

		// Validate blocks array if present (PRD §4.6)
		if ( isset( $schema['blocks'] ) ) {
			if ( ! is_array( $schema['blocks'] ) ) {
				return 'blocks must be an array';
			}
			foreach ( $schema['blocks'] as $i => $block_type ) {
				if ( empty( $block_type['type'] ) ) {
					return "Block type {$i}: missing type";
				}
				if ( empty( $block_type['name'] ) ) {
					return "Block type {$i}: missing name";
				}
				if ( ! isset( $block_type['settings'] ) || ! is_array( $block_type['settings'] ) ) {
					return "Block type {$i}: missing settings array";
				}
			}
		}

		// Validate optional assets key (per-section script/style dependencies).
		if ( isset( $schema['assets'] ) ) {
			if ( ! is_array( $schema['assets'] ) ) {
				return 'assets must be an object';
			}
			foreach ( array( 'scripts', 'styles' ) as $group ) {
				if ( ! isset( $schema['assets'][ $group ] ) ) {
					continue;
				}
				if ( ! is_array( $schema['assets'][ $group ] ) ) {
					return "assets.{$group} must be an array";
				}
				foreach ( $schema['assets'][ $group ] as $i => $item ) {
					if ( empty( $item['handle'] ) ) {
						return "assets.{$group}[{$i}]: missing handle";
					}
					if ( empty( $item['src'] ) ) {
						return "assets.{$group}[{$i}]: missing src";
					}
				}
			}
		}

		return true;
	}
}