<?php
/**
 * A pragmatic JSON Schema validator for tool inputs.
 *
 * Covers the subset used by tool input schemas: object with properties,
 * required, per-property type (string/integer/number/boolean/array/object),
 * enum, min/max, minLength/maxLength, default filling, array item typing, and
 * additionalProperties:false. This keeps the plugin dependency-free while
 * rejecting malformed AI-supplied arguments before they reach WordPress.
 *
 * @package GripMCP
 */

declare( strict_types=1 );

namespace GripMCP\Tools;

defined( 'ABSPATH' ) || exit;

final class Schema_Validator {

	/**
	 * Validate and coerce arguments against a schema.
	 *
	 * @param array<string, mixed> $arguments Raw arguments.
	 * @param array<string, mixed> $schema    JSON Schema (object type).
	 * @return array<string, mixed>|\WP_Error Coerced arguments or an error.
	 */
	public function validate( array $arguments, array $schema ) {
		$properties = isset( $schema['properties'] ) && is_array( $schema['properties'] ) ? $schema['properties'] : array();
		$required   = isset( $schema['required'] ) && is_array( $schema['required'] ) ? $schema['required'] : array();
		$additional = ! array_key_exists( 'additionalProperties', $schema ) || false !== $schema['additionalProperties'];

		$errors = array();
		$out    = array();

		// Reject unexpected properties when additionalProperties is false.
		if ( ! $additional ) {
			foreach ( array_keys( $arguments ) as $key ) {
				if ( ! isset( $properties[ $key ] ) ) {
					$errors[] = sprintf(
						/* translators: %s: property name. */
						__( 'Unexpected property "%s".', 'gripmcp' ),
						$key
					);
				}
			}
		} else {
			// Pass through unknown properties untouched.
			foreach ( $arguments as $key => $value ) {
				if ( ! isset( $properties[ $key ] ) ) {
					$out[ $key ] = $value;
				}
			}
		}

		foreach ( $properties as $name => $spec ) {
			$has = array_key_exists( $name, $arguments );

			if ( ! $has ) {
				if ( in_array( $name, $required, true ) ) {
					$errors[] = sprintf(
						/* translators: %s: property name. */
						__( 'Missing required property "%s".', 'gripmcp' ),
						$name
					);
				} elseif ( is_array( $spec ) && array_key_exists( 'default', $spec ) ) {
					$out[ $name ] = $spec['default'];
				}
				continue;
			}

			$value  = $arguments[ $name ];
			$result = $this->validate_value( $name, $value, is_array( $spec ) ? $spec : array() );

			if ( is_wp_error( $result ) ) {
				$errors[] = $result->get_error_message();
				continue;
			}

			$out[ $name ] = $result;
		}

		if ( ! empty( $errors ) ) {
			return new \WP_Error(
				'gripmcp_invalid_arguments',
				__( 'Invalid arguments: ', 'gripmcp' ) . implode( ' ', $errors ),
				array( 'errors' => $errors )
			);
		}

		return $out;
	}

	/**
	 * Validate/coerce a single value against a property spec.
	 *
	 * @param string               $name  Property name.
	 * @param mixed                $value Value.
	 * @param array<string, mixed> $spec  Property schema.
	 * @return mixed|\WP_Error
	 */
	private function validate_value( string $name, $value, array $spec ) {
		$type = isset( $spec['type'] ) ? (string) $spec['type'] : '';

		// Enum.
		if ( isset( $spec['enum'] ) && is_array( $spec['enum'] ) && ! in_array( $value, $spec['enum'], true ) ) {
			return new \WP_Error(
				'invalid',
				sprintf(
					/* translators: 1: property, 2: allowed values. */
					__( 'Property "%1$s" must be one of: %2$s.', 'gripmcp' ),
					$name,
					implode( ', ', array_map( 'strval', $spec['enum'] ) )
				)
			);
		}

		switch ( $type ) {
			case 'string':
				if ( ! is_string( $value ) ) {
					return $this->type_error( $name, 'string' );
				}
				if ( isset( $spec['maxLength'] ) && strlen( $value ) > (int) $spec['maxLength'] ) {
					return new \WP_Error( 'invalid', sprintf( /* translators: 1: property, 2: max. */ __( '"%1$s" exceeds max length %2$d.', 'gripmcp' ), $name, (int) $spec['maxLength'] ) );
				}
				if ( isset( $spec['minLength'] ) && strlen( $value ) < (int) $spec['minLength'] ) {
					return new \WP_Error( 'invalid', sprintf( /* translators: 1: property, 2: min. */ __( '"%1$s" is shorter than min length %2$d.', 'gripmcp' ), $name, (int) $spec['minLength'] ) );
				}
				return $value;

			case 'integer':
				if ( is_bool( $value ) || ! is_numeric( $value ) || (int) $value != $value ) { // phpcs:ignore Universal.Operators.StrictComparisons.LooseNotEqual
					return $this->type_error( $name, 'integer' );
				}
				return $this->range_check( $name, (int) $value, $spec );

			case 'number':
				if ( is_bool( $value ) || ! is_numeric( $value ) ) {
					return $this->type_error( $name, 'number' );
				}
				return $this->range_check( $name, (float) $value, $spec );

			case 'boolean':
				if ( is_bool( $value ) ) {
					return $value;
				}
				// Coerce common representations from lenient clients.
				if ( in_array( $value, array( 'true', '1', 1 ), true ) ) {
					return true;
				}
				if ( in_array( $value, array( 'false', '0', 0 ), true ) ) {
					return false;
				}
				return $this->type_error( $name, 'boolean' );

			case 'array':
				if ( ! is_array( $value ) || ( ! empty( $value ) && array_keys( $value ) !== range( 0, count( $value ) - 1 ) ) ) {
					return $this->type_error( $name, 'array' );
				}
				if ( isset( $spec['items']['type'] ) ) {
					foreach ( $value as $i => $item ) {
						$check = $this->validate_value( $name . "[$i]", $item, $spec['items'] );
						if ( is_wp_error( $check ) ) {
							return $check;
						}
					}
				}
				return $value;

			case 'object':
				if ( ! is_array( $value ) ) {
					return $this->type_error( $name, 'object' );
				}
				return $value;

			default:
				// Unknown/absent type: accept as-is.
				return $value;
		}
	}

	/**
	 * Numeric range checking.
	 *
	 * @param string    $name  Property name.
	 * @param int|float $value Value.
	 * @param array     $spec  Spec.
	 * @return int|float|\WP_Error
	 */
	private function range_check( string $name, $value, array $spec ) {
		if ( isset( $spec['minimum'] ) && $value < $spec['minimum'] ) {
			return new \WP_Error( 'invalid', sprintf( /* translators: 1: property, 2: min. */ __( '"%1$s" must be >= %2$s.', 'gripmcp' ), $name, (string) $spec['minimum'] ) );
		}
		if ( isset( $spec['maximum'] ) && $value > $spec['maximum'] ) {
			return new \WP_Error( 'invalid', sprintf( /* translators: 1: property, 2: max. */ __( '"%1$s" must be <= %2$s.', 'gripmcp' ), $name, (string) $spec['maximum'] ) );
		}
		return $value;
	}

	/**
	 * Build a type error.
	 *
	 * @param string $name     Property name.
	 * @param string $expected Expected type.
	 */
	private function type_error( string $name, string $expected ): \WP_Error {
		return new \WP_Error(
			'invalid',
			sprintf(
				/* translators: 1: property, 2: type. */
				__( 'Property "%1$s" must be of type %2$s.', 'gripmcp' ),
				$name,
				$expected
			)
		);
	}
}