<?php

namespace Libs;

use Closure;
use Exception;
use ReflectionClass;
use ReflectionFunction;
use ReflectionMethod;
use ReflectionParameter;

/**
 * Synapsis - DuckBrain
 *
 * Class responsible for dependency resolution and injection.
 *
 * @author KJ
 * @website https://kj2.me
 * @license MIT
 */
class Synapsis
{
    /**
     * @var array<class-string, class-string> $bindings
     */
    private static array $bindings = [];
    /**
     * @var array<class-string, mixed> $instances
     */
    private static array $instances = [];

    /**
     * Binds an interface to a class to instantiate it instead.
     *
     * @param class-string $interfaceName
     * @param class-string $className
     *
     * @return void
     * @throws Exception If the interface or class does not exist.
     */
    public static function bind(string $interfaceName, string $className): void
    {
        if (interface_exists($interfaceName) && class_exists($className)) {
            static::$bindings[$interfaceName] = $className;
            return;
        }

        throw new Exception('Error at binding non existant Interface or ClassName.');
    }

    /**
     * Binds multiple interfaces to multiple classes in bulk.
     *
     * @param array<class-string, class-string> $bindings
     *
     * @return void
     */
    public static function bulkBind(array $bindings): void
    {
        foreach ($bindings as $interfaceName => $className) {
            static::bind($interfaceName, $className);
        }
    }

    /**
     * Resolves and injects dependencies for a callable and returns its result.
     *
     * @param callable $action
     *
     * @return mixed
     * @throws Exception If an unhandled callable type is provided.
     */
    public static function resolve(callable $action): mixed
    {
        if ($action instanceof Closure) { // If it's an anonymous function
            $reflectionCallback = new ReflectionFunction($action);
        } else { // Array or string with the method
            if (is_string($action)) {
                $action = preg_split('/::/', $action);
            }

            // Check if it's a method or just a function
            if (count($action) == 2) {
                $reflectionCallback = new ReflectionMethod($action[0], $action[1]);
            } else {
                $reflectionCallback = new ReflectionFunction($action[0]);
            }
        }

        // Get the parameters
        return call_user_func_array(
            $action,
            static::resolveParameterValues($reflectionCallback->getParameters())
        );
    }

    /**
     * Resolves and injects dependencies for a class and returns its result.
     *
     * @param class-string $className
     *
     * @return mixed
     * @throws Exception If a binding is missing for an interface or the class does not exist.
     */
    public static function &resolveInstance(string $className): mixed
    {
        if (interface_exists($className)) {
            if (isset(static::$bindings[$className])) {
                $className = static::$bindings[$className];
            } else {
                throw new Exception("Missing binding for interface: {$className}");
            }
        }

        if (!class_exists($className)) {
            throw new Exception("Cannot resolve: {$className}");
        }

        if (!isset(static::$instances[$className])) {
            // If the instance has not been resolved before, resolve it
            $reflectionClass = new ReflectionClass($className);
            $constructor = $reflectionClass->getConstructor();
            static::$instances[$className] = new $className(
                ...static::resolveParameterValues($constructor?->getParameters() ?? [])
            );
        }

        return static::$instances[$className];
    }

    /**
     * Resolves parameter values by injecting dependencies.
     *
     * @param array<ReflectionParameter> $parameters
     *
     * @return array<mixed>
     * @throws Exception    If a primitive parameter does not have a default value.
     */
    public static function resolveParameterValues(array $parameters): array
    {
        $values = [];
        foreach ($parameters as $parameter) {
            if ($parameter->isOptional()) { // Always use the default value first
                $values[] = $parameter->getDefaultValue();
                continue;
            }

            $paramType = $parameter->getType();
            if ($paramType === null) {
                // If no type is declared, and it's not optional, we cannot resolve it.
                throw new Exception('Untyped parameters expect at least a default value or must be optional.');
            }

            if ($paramType->isBuiltin()) {
                throw new Exception("Primitive parameter '{$parameter->getName()}' expects at least a default value.");
            }

            $values[] = static::resolveInstance($paramType->getName());
        }
        return $values;
    }
}