<?php
/**
 * @license MIT
 * Copyright 2017 Dustin Wilson, J. King, et al.
 * See LICENSE and AUTHORS files for details
 */

declare(strict_types=1);
namespace MensBeam\HTML\DOM;
use MensBeam\HTML\Parser\Data,
    MensBeam\GettersAndSetters;


class DOMTokenList implements \ArrayAccess, \Countable, \Iterator {
    use GettersAndSetters;


    protected \WeakReference $element;
    protected int $_length = 0;
    protected string $localName;
    protected int $position = 0;
    protected array $supportedTokens;
    # A DOMTokenList object has an associated token set (a set), which is initially
    # empty.
    protected array $tokenSet = [];


    protected function __get_length(): int {
        return $this->_length;
    }

    protected function __get_value(): string {
        # The value attribute must return the result of running this’s serialize steps.
        return $this->__toString();
    }

    protected function __set_value(string $value) {
        # Setting the value attribute must set an attribute value for the associated
        # element using associated attribute’s local name and the given value.
        $element = $this->element->get()->innerNode;
        $element->setAttribute($this->localName, $value);
        // Also update the token set and the length.
        $this->tokenSet = $this->parseOrderedSet($value);
        $this->_length = count($this->tokenSet);
    }


    protected function __construct(Element $element, string $attributeLocalName, array $supportedTokens = []) {
        # A DOMTokenList object also has an associated element and an attribute’s local
        # name.
        // Apparently the "attribute's local name" has an associated set of supported
        // tokens, but the specification is extremely vague on how this is supposed to
        // be done. Going to have a list of supported tokens as a parameter.

        # When a DOMTokenList object is created, then:
        #
        # 1. Let element be associated element.
        // Using a weak reference here to prevent a circular reference.
        $this->element = \WeakReference::create($element);
        # 2. Let localName be associated attribute’s local name.
        $this->localName = $attributeLocalName;
        $this->supportedTokens = $supportedTokens;
        # 3. Let value be the result of getting an attribute value given element and
        # localName.
        $element = $element->innerNode;
        $value = $element->getAttribute($attributeLocalName);
        # 4. Run the attribute change steps for element, localName, value, value, and
        # null.
        # A DOMTokenList object has these attribute change steps for its associated
        # element:
        # 1. If localName is associated attribute’s local name, namespace is null, and
        # value is null, then empty token set.
        // localName will always be the associated attribute's local name; there's no
        // namespace here.
        // Also need to check for empty string here because PHP DOM incorrectly returns
        // an empty string here
        if ($value === '' || $value === null) {
            $this->tokenSet = [];
            $this->_length = 0;
        }
        # 2. Otherwise, if localName is associated attribute’s local name, namespace is
        # null, then set token set to value, parsed.
        // localName will always be the associated attribute's local name; there's no
        // namespace here.
        else {
            $this->tokenSet = $this->parseOrderedSet($value);
            $this->_length = count($this->tokenSet);
        }
    }


    public function add(...$tokens): void {
        # 1. For each token in tokens:
        foreach ($tokens as $token) {
            # 1. If token is the empty string, then throw a "SyntaxError" DOMException.
            if ($token === '') {
                throw new SyntaxError();
            }

            # 2. If token contains any ASCII whitespace, then throw an
            # "InvalidCharacterError" DOMException.
            if (preg_match(Data::WHITESPACE_REGEX, $token)) {
                throw new InvalidCharacterError();
            }
        }

        # 2. For each token in tokens, append token to this’s token set.
        foreach ($tokens as $token) {
            # To append to an ordered set: if the set contains the given item, then do
            # nothing; otherwise, perform the normal list append operation.
            if (!in_array($token, $this->tokenSet)) {
                $this->tokenSet[] = $token;
                $this->_length++;
            }
        }

        # 3. Run the update steps.
        $this->update();
    }

    public function contains(string $token): bool {
        return (in_array($token, $this->tokenSet));
    }

    public function count(): int {
        return $this->_length;
    }

    public function current(): ?string {
        return $this->item($this->position);
    }

    public function item(int $index): ?string {
        # The item(index) method steps are:
        # 1. If index is equal to or greater than this’s token set’s size, then return null.
        if ($index >= $this->_length) {
            return null;
        }
        # 2. Return this’s token set[index].
        return $this->tokenSet[$index];
    }

    public function key(): int {
        return $this->position;
    }

    public function next(): void {
        ++$this->position;
    }

    public function rewind(): void {
        $this->position = 0;
    }

    public function offsetExists($offset): bool {
        return isset($this->tokenSet[$offset]);
    }

    public function offsetGet($offset): ?string {
        return $this->item($offset);
    }

    public function offsetSet($offset, $value): void {
        // Spec says nothing about setting values on DOMTokenList outside of add();
        // browsers silently fail here.
    }

    public function offsetUnset($offset): void {
        // Spec says nothing about unsetting values on DOMTokenList outside of remove();
        // browsers silently fail here.
    }

    public function remove(...$tokens): void {
        # 1. For each token in tokens:
        foreach ($tokens as $token) {
            # 1. If token is the empty string, then throw a "SyntaxError" DOMException.
            if ($token === '') {
                throw new SyntaxError();
            }

            # 2. If token contains any ASCII whitespace, then throw an
            # "InvalidCharacterError" DOMException.
            if (preg_match(Data::WHITESPACE_REGEX, $token)) {
                throw new InvalidCharacterError();
            }
        }

        # For each token in tokens, remove token from this’s token set.
        $changed = false;
        foreach ($this->tokenSet as $key => $value) {
            foreach ($tokens as $token) {
                if ($value === $token) {
                    unset($this->tokenSet[$key]);
                    $this->_length--;
                    $changed = true;
                }
            }
        }

        if ($changed) {
            $this->tokenSet = array_values($this->tokenSet);
        }

        # 3. Run the update steps.
        $this->update();
    }

    public function replace(string $token, string $newToken): bool {
        # 1. If either token or newToken is the empty string, then throw a "SyntaxError"
        # DOMException.
        if ($token === '' || $newToken === '') {
            throw new SyntaxError();
        }

        # 2. If either token or newToken contains any ASCII whitespace, then throw an
        # "InvalidCharacterError" DOMException.
        if (preg_match(Data::WHITESPACE_REGEX, $token) || preg_match(Data::WHITESPACE_REGEX, $newToken)) {
            throw new InvalidCharacterError();
        }

        # 3. If this’s token set does not contain token, then return false.
        if (!($key = array_search($token, $this->tokenSet))) {
            return false;
        }

        # 4. Replace token in this’s token set with newToken.
        $this->tokenSet[$key] = $newToken;

        # 5. Run the update steps.
        $this->update();

        # 6. Return true.
        return true;
    }

    public function supports(string $token): bool {
        # 1. Let result be the return value of validation steps called with token.
        # 2. Return result.
        #
        # A DOMTokenList object’s validation steps for a given token are:
        #
        # 1. If the associated attribute’s local name does not define supported tokens,
        # throw a TypeError.
        if (count($this->supportedTokens) === 0) {
            trigger_error('Type error; there are no defined supported tokens', \E_USER_ERROR);
        }

        // This part cannot be covered until there's something in the standard which
        // defines supported tokens. HTMLMediaElement::controlsList is a non-standard
        // method which does define supported tokens, but until it is standardized it
        // won't be added in this implementation.

        // @codeCoverageIgnoreStart
        # 2. Let lowercase token be a copy of token, in ASCII lowercase.
        $lowercaseToken = strtolower($token);

        # 3. If lowercase token is present in supported tokens, return true.
        if (in_array($lowercaseToken, $this->supportedTokens)) {
            return true;
        }

        # 4. Return false.
        return false;
        // @codeCoverageIgnoreEnd
    }

    public function toggle(string $token, ?bool $force = null): bool {
        # 1. If token is the empty string, then throw a "SyntaxError" DOMException.
        if ($token === '') {
            throw new SyntaxError();
        }

        # 2. If token contains any ASCII whitespace, then throw an
        # "InvalidCharacterError" DOMException.
        if (preg_match(Data::WHITESPACE_REGEX, $token)) {
            throw new InvalidCharacterError();
        }

        # 3. If this’s token set[token] exists, then:
        if (in_array($token, $this->tokenSet)) {
            # 1. If force is either not given or is false, then remove token from this’s
            # token set, run the update steps and return false.
            if (!$force) {
                $this->remove($token);
                return false;
            }

            # 2. Return true.
            return true;
        }
        # 4. Otherwise, if force not given or is true, append token to this’s token set,
        # run the update steps, and return true.
        elseif ($force === null || $force === true) {
            $this->add($token);
            return true;
        }

        # 5. Return false.
        return false;
    }

    public function valid(): bool {
        return array_key_exists($this->position, $this->tokenSet);
    }


    protected function parseOrderedSet(string $input): array {
        if ($input === '') {
            return [];
        }

        # The ordered set parser takes a string input and then runs these steps:
        #
        # 1. Let inputTokens be the result of splitting input on ASCII whitespace.
        // There isn't a Set object in php, so make sure all the tokens are unique.
        $inputTokens = array_unique(preg_split(Data::WHITESPACE_REGEX, $input));

        # 2. Let tokens be a new ordered set.
        # 3. For each token in inputTokens, append token to tokens.
        # 4. Return tokens.
        // There isn't a Set object in php, so just return the uniqued input tokens.
        return $inputTokens;
    }

    protected function update(): void {
        # A DOMTokenList object’s update steps are:

        $element = $this->element->get()->innerNode;

        # 1. If the associated element does not have an associated attribute and token
        # set is empty, then return.
        if (!$element->hasAttribute($this->localName) && count($this->tokenSet) === 0) {
            return;
        }

        # 2. Set an attribute value for the associated element using associated
        # attribute’s local name and the result of running the ordered set serializer
        # for token set.
        $class = $element->ownerDocument->createAttribute($this->localName);
        $class->value = $this->__toString();
        $element->setAttributeNode($class);
    }


    public function __toString(): string {
        # The ordered set serializer takes a set and returns the concatenation of set
        # using U+0020 SPACE.
        return implode(' ', $this->tokenSet);
    }
}