<?php

namespace Glovario\Domain;

use Glovario\Repository\VariableRepository;

defined( 'ABSPATH' ) || exit;

final class VariableResolver {
	private $repository;
	private $stack = array();
	private $remaining_references = 0;
	private $maximum_depth = 10;
	private $references;
	private $builtins;

	public function __construct( VariableRepository $repository, ?NestedReferenceParser $references = null, ?BuiltinVariables $builtins = null ) {
		$this->repository = $repository;
		$this->references = $references ? $references : new NestedReferenceParser();
		$this->builtins   = $builtins ? $builtins : new BuiltinVariables();
	}

	public function resolve( $key, $context = array() ) {
		$key = sanitize_key( $key );
		if ( '' === $key ) {
			return null;
		}

		$context         = is_array( $context ) ? $context : array();
		$locale_explicit = array_key_exists( '_glovario_locale_explicit', $context ) ? (bool) $context['_glovario_locale_explicit'] : array_key_exists( 'locale', $context );
		$context = wp_parse_args(
			$context,
			array(
				'post_id'   => get_the_ID() ? get_the_ID() : 0,
				'post_type' => get_post_type() ? get_post_type() : '',
				'locale'    => determine_locale(),
				'user_id'   => get_current_user_id(),
				'timestamp' => time(),
				'source'    => 'api',
			)
		);
		$context['_glovario_locale_explicit'] = $locale_explicit;
		$is_root = empty( $this->stack );
		if ( $is_root ) {
			/**
			 * Filters the maximum number of variables in one nested resolution chain.
			 *
			 * @param int    $maximum Maximum depth, including the root variable.
			 * @param string $key     Root variable key.
			 * @param array  $context Resolution context.
			 */
			$this->maximum_depth = min( 50, max( 1, absint( apply_filters( 'glovario_nested_max_depth', 10, $key, $context ) ) ) );
			/**
			 * Filters the total nested-reference budget for one root resolution.
			 *
			 * @param int    $maximum Maximum references expanded across the complete tree.
			 * @param string $key     Root variable key.
			 * @param array  $context Resolution context.
			 */
			$this->remaining_references = min( 1000, max( 1, absint( apply_filters( 'glovario_nested_max_references', 100, $key, $context ) ) ) );
		}
		if ( in_array( $key, $this->stack, true ) ) {
			return null;
		}

		$this->stack[] = $key;
		try {
			do_action( 'glovario_before_resolve', $key, $context );
			$variable = $this->builtins->find_by_key( $key, $context );
			if ( ! $variable ) {
				$variable = $this->repository->find_by_key( $key );
			}
			if ( ! $variable ) {
				/**
				 * Supplies a variable that is not stored on this site, such as a
				 * multisite network variable. Site variables always take precedence.
				 *
				 * @param array|null $variable Variable row, or null when unknown.
				 * @param string     $key      Requested key.
				 * @param array      $context  Resolution context.
				 */
				$variable = apply_filters( 'glovario_missing_variable', null, $key, $context );
			}
			if ( ! is_array( $variable ) ) {
				return null;
			}

			$value = apply_filters( 'glovario_resolved_value', $variable['value'], $variable, $context );
			$value = $this->expand_nested( $value, $context );
			return array(
				'value'    => $value,
				'variable' => $variable,
				'context'  => $context,
			);
		} finally {
			array_pop( $this->stack );
			if ( $is_root ) {
				$this->remaining_references = 0;
			}
		}
	}

	private function expand_nested( $value, $context ) {
		return $this->references->replace(
			$value,
			function ( $key, $fallback, $date_format ) use ( $context ) {
				if ( '' === $key ) {
					return $fallback;
				}
				if ( in_array( $key, $this->stack, true ) ) {
					$this->blocked_reference( $key, 'cycle', $context );
					return $fallback;
				}
				if ( count( $this->stack ) >= $this->maximum_depth ) {
					$this->blocked_reference( $key, 'depth', $context );
					return $fallback;
				}
				if ( 0 >= $this->remaining_references ) {
					$this->blocked_reference( $key, 'budget', $context );
					return $fallback;
				}
				--$this->remaining_references;
				$nested_context = $context;
				if ( BuiltinVariables::CURRENT_DATE_KEY === $key ) {
					$nested_context['date_format'] = $date_format;
				}
				$resolved = $this->resolve( $key, $nested_context );
				return $resolved ? (string) $resolved['value'] : $fallback;
			}
		);
	}

	private function blocked_reference( $key, $reason, $context ) {
		$parent = end( $this->stack );
		/**
		 * Fires when a nested reference is safely skipped.
		 *
		 * @param string $key     Referenced variable key.
		 * @param string $parent  Variable containing the reference.
		 * @param string $reason  One of cycle, depth, or budget.
		 * @param array  $context Resolution context.
		 */
		do_action( 'glovario_nested_reference_blocked', $key, $parent, $reason, $context );
	}
}