<?php

declare(strict_types=1);

namespace KTXF\Json;

use DateTimeInterface;
use DateTimeZone;
use DateInterval;

use KTXF\Json\JsonSerializable;
use KTXF\Json\JsonDeserializable;

abstract class JsonSerializableObject implements JsonSerializable, JsonDeserializable {

	protected string $dateTimeFormat = 'c'; // ISO 8601 format by default
	protected array $serializableProperties = []; // Empty array means serialize all properties
	protected array $nonSerializableProperties = ['dateTimeFormat', 'serializableProperties', 'nonSerializableProperties']; // Properties to exclude from serialization

	public function jsonSerialize(): mixed {
		$vars = get_object_vars($this);
		
		// Filter properties based on serializableProperties if specified
		if (!empty($this->serializableProperties)) {
			$vars = array_filter($vars, function($key) {
				return in_array($key, $this->serializableProperties);
			}, ARRAY_FILTER_USE_KEY);
		}
		
		// Process each property for special types
		foreach ($vars as $key => $value) {
			// Skip internal control properties
			if (in_array($key, $this->nonSerializableProperties)) {
				unset($vars[$key]);
				continue;
			}
			
			// Handle DateTimeInterface (DateTime/DateTimeImmutable)
			if ($value instanceof DateTimeInterface) {
				$vars[$key] = $value->format($this->dateTimeFormat);
			}
			// Handle DateTimeZone
			elseif ($value instanceof DateTimeZone) {
				$vars[$key] = $value->getName();
			}
			// Handle DateInterval
			elseif ($value instanceof DateInterval) {
				$vars[$key] = $this->fromDateInterval($value);
			}
			// Handle backed enums
			elseif ($value instanceof \BackedEnum) {
				$vars[$key] = $value->value;
			}
			// Handle JsonSerializable objects
			elseif ($value instanceof JsonSerializable) {
				$vars[$key] = $value->jsonSerialize();
			}
		}
		
		return $vars;
	}

	public function jsonDeserialize(array|string $data): static {

		if (is_string($data)) {
			$data = json_decode($data, true);
		}

		foreach ($data as $key => $value) {
			if (property_exists($this, $key)) {
				// Skip internal control properties
				if (in_array($key, $this->nonSerializableProperties)) {
					continue;
				}
				
				// Check if property should be deserialized (if serializableProperties is set)
				if (!empty($this->serializableProperties) && !in_array($key, $this->serializableProperties)) {
					continue;
				}

				// Null means absent: leave the property at its default rather
				// than passing null into an object's jsonDeserialize/enum
				// coercion or overwriting an initialized collection.
				if ($value === null) {
					continue;
				}

				$type = gettype($this->$key);
				
				// Handle JsonDeserializable objects
				if ($type === 'object' && $this->$key instanceof JsonDeserializable) {
					$this->$key = $this->$key->jsonDeserialize($value);
				}
				// Handle DateTimeInterface (DateTime/DateTimeImmutable)
				elseif ($type === 'object' && $this->$key instanceof DateTimeInterface) {
					$this->$key = new \DateTimeImmutable($value);
				}
				// Handle DateTimeZone
				elseif ($type === 'object' && $this->$key instanceof DateTimeZone) {
					$this->$key = new DateTimeZone($value);
				}
				// Handle DateInterval
				elseif ($type === 'object' && $this->$key instanceof DateInterval) {
					$this->$key = $this->toDateInterval($value);
				}
				// Handle backed enums
				elseif ($type === 'object' && $this->$key instanceof \BackedEnum) {
					$enumClass = get_class($this->$key);
					$this->$key = $enumClass::from($value);
				}
				// Handle regular values, coercing by declared type when the
				// current value is null and carries no instance to key off
				else {
					$this->$key = $this->coerceValue($key, $value);
				}
			}
		}

		return $this;
	}

	/**
	 * Coerces a decoded JSON value to the property's declared type. Needed for
	 * properties whose current value is null: the instanceof-based branches
	 * above cannot dispatch without an instance, and assigning the raw string
	 * to a typed property (DateTime, enum, ...) would raise a TypeError.
	 */
	private function coerceValue(string $key, mixed $value): mixed {
		$type = (new \ReflectionProperty($this, $key))->getType();
		if ($type instanceof \ReflectionNamedType) {
			$names = [$type->getName()];
		} elseif ($type instanceof \ReflectionUnionType) {
			$names = array_map(static fn($member) => $member->getName(), $type->getTypes());
		} else {
			return $value;
		}

		foreach ($names as $name) {
			if (!class_exists($name) && !interface_exists($name) && !enum_exists($name)) {
				continue;
			}
			if (is_string($value) && is_a($name, DateTimeInterface::class, true)) {
				return $name === \DateTime::class ? new \DateTime($value) : new \DateTimeImmutable($value);
			}
			if (is_string($value) && is_a($name, DateTimeZone::class, true)) {
				return new DateTimeZone($value);
			}
			if (is_string($value) && is_a($name, DateInterval::class, true)) {
				return $this->toDateInterval($value);
			}
			if ((is_string($value) || is_int($value)) && is_subclass_of($name, \BackedEnum::class)) {
				return $name::from($value);
			}
			if ((is_array($value) || is_string($value)) && is_subclass_of($name, JsonDeserializable::class)) {
				/** @var JsonDeserializable $instance */
				$instance = new $name();
				return $instance->jsonDeserialize($value);
			}
		}

		return $value;
	}

	protected function fromDateInterval(DateInterval $interval): string {
		$spec = '';
		
		// Handle negative intervals
		if ($interval->invert === 1) {
			$spec = '-';
		}
		
		$spec .= 'P';
		
		if ($interval->y > 0) $spec .= $interval->y . 'Y';
		if ($interval->m > 0) $spec .= $interval->m . 'M';
		if ($interval->d > 0) $spec .= $interval->d . 'D';
		
		$timePart = '';
		if ($interval->h > 0) $timePart .= $interval->h . 'H';
		if ($interval->i > 0) $timePart .= $interval->i . 'M';
		if ($interval->s > 0) $timePart .= $interval->s . 'S';
		
		if (!empty($timePart)) {
			$spec .= 'T' . $timePart;
		}
		
		// Handle edge case of zero duration
		if ($spec === 'P' || $spec === '-P') {
			$spec = 'PT0S';
		}
		
		return $spec;
	}

	protected function toDateInterval(string $value): DateInterval {
		$isNegative = false;
		
		// Check for negative interval
		if (str_starts_with($value, '-')) {
			$isNegative = true;
			$value = substr($value, 1);
		}
		
		// Create the interval
		$interval = new DateInterval($value);
		
		// Set invert property for negative intervals
		if ($isNegative) {
			$interval->invert = 1;
		}
		
		return $interval;
	}

}