<?php

declare(strict_types=1);

namespace libphonenumber\buildtools;

use libphonenumber\buildtools\Builders\PhoneMetadataBuilder;
use libphonenumber\NumberFormat;
use libphonenumber\PhoneNumberDesc;
use DOMDocument;
use DOMElement;
use RuntimeException;

use function array_intersect;
use function array_key_exists;
use function array_merge;
use function array_unshift;
use function count;
use function explode;
use function implode;
use function in_array;
use function is_numeric;
use function preg_last_error;
use function preg_match;
use function preg_replace;
use function sort;
use function str_replace;
use function strpos;
use function substr;

/**
 * Library to build phone number metadata from the XML format.
 *
 * @author Davide Mendolia
 * @internal
 */
class BuildMetadataFromXml
{
    // String constants used to fetch the XML nodes and attributes.
    public const CARRIER_CODE_FORMATTING_RULE = 'carrierCodeFormattingRule';
    public const COUNTRY_CODE = 'countryCode';
    public const EMERGENCY = 'emergency';
    public const EXAMPLE_NUMBER = 'exampleNumber';
    public const FIXED_LINE = 'fixedLine';
    public const FORMAT = 'format';
    public const GENERAL_DESC = 'generalDesc';
    public const INTERNATIONAL_PREFIX = 'internationalPrefix';
    public const INTL_FORMAT = 'intlFormat';
    public const LEADING_DIGITS = 'leadingDigits';
    public const MOBILE_NUMBER_PORTABLE_REGION = 'mobileNumberPortableRegion';
    public const MAIN_COUNTRY_FOR_CODE = 'mainCountryForCode';
    public const MOBILE = 'mobile';
    public const NATIONAL_NUMBER_PATTERN = 'nationalNumberPattern';
    public const NATIONAL_PREFIX = 'nationalPrefix';
    public const NATIONAL_PREFIX_FORMATTING_RULE = 'nationalPrefixFormattingRule';
    public const NATIONAL_PREFIX_OPTIONAL_WHEN_FORMATTING = 'nationalPrefixOptionalWhenFormatting';
    public const NATIONAL_PREFIX_FOR_PARSING = 'nationalPrefixForParsing';
    public const NATIONAL_PREFIX_TRANSFORM_RULE = 'nationalPrefixTransformRule';
    public const NO_INTERNATIONAL_DIALLING = 'noInternationalDialling';
    public const NUMBER_FORMAT = 'numberFormat';
    public const PAGER = 'pager';
    public const CARRIER_SPECIFIC = 'carrierSpecific';
    public const PATTERN = 'pattern';
    public const PERSONAL_NUMBER = 'personalNumber';
    public const POSSIBLE_LENGTHS = 'possibleLengths';
    public const NATIONAL = 'national';
    public const LOCAL_ONLY = 'localOnly';
    public const PREFERRED_EXTN_PREFIX = 'preferredExtnPrefix';
    public const PREFERRED_INTERNATIONAL_PREFIX = 'preferredInternationalPrefix';
    public const PREMIUM_RATE = 'premiumRate';
    public const SHARED_COST = 'sharedCost';
    public const SHORT_CODE = 'shortCode';
    public const SMS_SERVICES = 'smsServices';
    public const STANDARD_RATE = 'standardRate';
    public const TOLL_FREE = 'tollFree';
    public const UAN = 'uan';
    public const VOICEMAIL = 'voicemail';
    public const VOIP = 'voip';

    /**
     * @var string[]
     */
    private static array $phoneNumberDescsWithoutMatchingTypes = [
        self::NO_INTERNATIONAL_DIALLING,
    ];

    public static function validateRE(string $regex, bool $removeWhitespace = false): string
    {
        $compressedRegex = $removeWhitespace ? preg_replace('/\\s/', '', $regex) : $regex;
        // Match regex against an empty string to check the regex is valid
        if (@preg_match('/' . $compressedRegex . '/', '') === false) {
            throw new RuntimeException('Regex error: ' . preg_last_error());
        }
        // We don't ever expect to see | followed by a ) in our metadata - this would be an indication
        // of a bug. If one wants to make something optional, we prefer ? to using an empty group.
        $errorIndex = strpos($compressedRegex, '|)');
        if ($errorIndex !== false) {
            throw new RuntimeException('| followed by )');
        }
        // return the regex if it is of correct syntax, i.e. compile did not fail with a
        return $compressedRegex;
    }

    /**
     * @return PhoneMetadataBuilder[]
     */
    public static function buildPhoneMetadataCollection(string|DOMElement $inputXmlFile, bool $isShortNumberMetadata = false, bool $isAlternateFormatsMetadata = false): array
    {
        if ($inputXmlFile instanceof DOMElement) {
            $document = $inputXmlFile;
        } else {
            $document = new DOMDocument();
            $document->load($inputXmlFile);
            $document->normalizeDocument();

            $isShortNumberMetadata = str_contains($inputXmlFile, 'ShortNumberMetadata');
            $isAlternateFormatsMetadata = str_contains($inputXmlFile, 'PhoneNumberAlternateFormats');
        }

        $territories = $document->getElementsByTagName('territory');
        $metadataCollection = [];

        foreach ($territories as $territoryElement) {
            /** @var DOMElement $territoryElement */
            // For the main metadata file this should always be set, but for other supplementary data
            // files the country calling code may be all that is needed.
            if ($territoryElement->hasAttribute('id')) {
                $regionCode = $territoryElement->getAttribute('id');
            } else {
                $regionCode = '';
            }
            $metadata = self::loadCountryMetadata($regionCode, $territoryElement, $isShortNumberMetadata, $isAlternateFormatsMetadata);
            $metadataCollection[] = $metadata;
        }
        return $metadataCollection;
    }

    public static function loadCountryMetadata(string $regionCode, DOMElement $element, bool $isShortNumberMetadata, bool $isAlternateFormatsMetadata): PhoneMetadataBuilder
    {
        $nationalPrefix = self::getNationalPrefix($element);
        $metadata = self::loadTerritoryTagMetadata($regionCode, $element, $nationalPrefix);
        $nationalPrefixFormattingRule = self::getNationalPrefixFormattingRuleFromElement($element, $nationalPrefix);

        self::loadAvailableFormats($metadata, $element, $nationalPrefix, $nationalPrefixFormattingRule, $element->hasAttribute(self::NATIONAL_PREFIX_OPTIONAL_WHEN_FORMATTING));
        if (!$isAlternateFormatsMetadata) {
            // The alternate formats metadata does not need most of the patterns to be set.
            self::setRelevantDescPatterns($metadata, $element, $isShortNumberMetadata);
        }
        return $metadata;
    }

    /**
     * Returns the national prefix of the provided country element.
     */
    public static function getNationalPrefix(DOMElement $element): string
    {
        return $element->hasAttribute(self::NATIONAL_PREFIX) ? $element->getAttribute(self::NATIONAL_PREFIX) : '';
    }

    public static function getNationalPrefixFormattingRuleFromElement(DOMElement $element, string $nationalPrefix): string
    {
        $nationalPrefixFormattingRule = $element->getAttribute(self::NATIONAL_PREFIX_FORMATTING_RULE);
        // Replace $NP with national prefix and $FG with the first group ($1).
        return str_replace(
            ['$NP', '$FG'],
            [$nationalPrefix, '$1'],
            $nationalPrefixFormattingRule
        );
    }

    public static function loadTerritoryTagMetadata(
        string $regionCode,
        DOMElement $element,
        string $nationalPrefix
    ): PhoneMetadataBuilder {
        $metadata = new PhoneMetadataBuilder();
        $metadata->setId($regionCode);
        $metadata->setCountryCode((int) $element->getAttribute(self::COUNTRY_CODE));
        if ($element->hasAttribute(self::LEADING_DIGITS)) {
            $metadata->setLeadingDigits(self::validateRE($element->getAttribute(self::LEADING_DIGITS)));
        }
        $metadata->setInternationalPrefix(self::validateRE($element->getAttribute(self::INTERNATIONAL_PREFIX)));
        if ($element->hasAttribute(self::PREFERRED_INTERNATIONAL_PREFIX)) {
            $preferredInternationalPrefix = $element->getAttribute(self::PREFERRED_INTERNATIONAL_PREFIX);
            $metadata->setPreferredInternationalPrefix($preferredInternationalPrefix);
        }
        if ($element->hasAttribute(self::NATIONAL_PREFIX_FOR_PARSING)) {
            $metadata->setNationalPrefixForParsing(
                self::validateRE($element->getAttribute(self::NATIONAL_PREFIX_FOR_PARSING), true)
            );
            if ($element->hasAttribute(self::NATIONAL_PREFIX_TRANSFORM_RULE)) {
                $metadata->setNationalPrefixTransformRule(self::validateRE($element->getAttribute(self::NATIONAL_PREFIX_TRANSFORM_RULE)));
            }
        }
        if ($nationalPrefix !== '') {
            $metadata->setNationalPrefix($nationalPrefix);
            if (!$metadata->hasNationalPrefixForParsing()) {
                $metadata->setNationalPrefixForParsing($nationalPrefix);
            }
        }
        if ($element->hasAttribute(self::PREFERRED_EXTN_PREFIX)) {
            $metadata->setPreferredExtnPrefix($element->getAttribute(self::PREFERRED_EXTN_PREFIX));
        }
        if ($element->hasAttribute(self::MAIN_COUNTRY_FOR_CODE)) {
            $metadata->setMainCountryForCode(true);
        }
        if ($element->hasAttribute(self::MOBILE_NUMBER_PORTABLE_REGION)) {
            $metadata->setMobileNumberPortableRegion(true);
        }
        return $metadata;
    }

    /**
     * Extracts the available formats from the provided DOM element. If it does not contain any
     * nationalPrefixFormattingRule, the one passed-in is retained; similarly for
     * nationalPrefixOptionalWhenFormatting. The nationalPrefix, nationalPrefixFormattingRule and
     * nationalPrefixOptionalWhenFormatting values are provided from the parent (territory) element.
     */
    public static function loadAvailableFormats(
        PhoneMetadataBuilder $metadata,
        DOMElement $element,
        string $nationalPrefix,
        string $nationalPrefixFormattingRule,
        bool $nationalPrefixOptionalWhenFormatting
    ): void {
        $carrierCodeFormattingRule = '';
        if ($element->hasAttribute(self::CARRIER_CODE_FORMATTING_RULE)) {
            $carrierCodeFormattingRule = self::validateRE(self::getDomesticCarrierCodeFormattingRuleFromElement($element, $nationalPrefix));
        }
        $numberFormatElements = $element->getElementsByTagName(self::NUMBER_FORMAT);
        $hasExplicitIntlFormatDefined = false;

        $numOfFormatElements = $numberFormatElements->length;
        if ($numOfFormatElements > 0) {
            for ($i = 0; $i < $numOfFormatElements; $i++) {
                /** @var DOMElement $numberFormatElement */
                $numberFormatElement = $numberFormatElements->item($i);
                $format = new NumberFormat();

                if ($numberFormatElement->hasAttribute(self::NATIONAL_PREFIX_FORMATTING_RULE)) {
                    $format->setNationalPrefixFormattingRule(
                        self::getNationalPrefixFormattingRuleFromElement($numberFormatElement, $nationalPrefix)
                    );
                } else {
                    $format->setNationalPrefixFormattingRule($nationalPrefixFormattingRule);
                }
                if ($numberFormatElement->hasAttribute(self::NATIONAL_PREFIX_OPTIONAL_WHEN_FORMATTING)) {
                    $format->setNationalPrefixOptionalWhenFormatting($numberFormatElement->getAttribute(self::NATIONAL_PREFIX_OPTIONAL_WHEN_FORMATTING) === 'true');
                } else {
                    $format->setNationalPrefixOptionalWhenFormatting($nationalPrefixOptionalWhenFormatting);
                }
                if ($numberFormatElement->hasAttribute(self::CARRIER_CODE_FORMATTING_RULE)) {
                    $format->setDomesticCarrierCodeFormattingRule(
                        self::validateRE(self::getDomesticCarrierCodeFormattingRuleFromElement($numberFormatElement, $nationalPrefix))
                    );
                } else {
                    $format->setDomesticCarrierCodeFormattingRule($carrierCodeFormattingRule);
                }
                self::loadNationalFormat($metadata, $numberFormatElement, $format);
                $metadata->addNumberFormat($format);

                if (self::loadInternationalFormat($metadata, $numberFormatElement, $format)) {
                    $hasExplicitIntlFormatDefined = true;
                }
            }
            // Only a small number of regions need to specify the intlFormats in the xml. For the majority
            // of countries the intlNumberFormat metadata is an exact copy of the national NumberFormat
            // metadata. To minimize the size of the metadata file, we only keep intlNumberFormats that
            // actually differ in some way to the national formats.
            if (!$hasExplicitIntlFormatDefined) {
                $metadata->clearIntlNumberFormat();
            }
        }
    }

    public static function getDomesticCarrierCodeFormattingRuleFromElement(DOMElement $element, string $nationalPrefix): string
    {
        $carrierCodeFormattingRule = $element->getAttribute(self::CARRIER_CODE_FORMATTING_RULE);
        // Replace $FG with the first group ($1) and $NP with the national prefix.
        return str_replace(
            ['$NP', '$FG'],
            [$nationalPrefix, '$1'],
            $carrierCodeFormattingRule
        );
    }

    /**
     * Extracts the pattern for the national format.
     *
     * @throws RuntimeException if multiple or no formats have been encountered.
     */
    public static function loadNationalFormat(
        PhoneMetadataBuilder $metadata,
        DOMElement $numberFormatElement,
        NumberFormat $format
    ): void {
        self::setLeadingDigitsPatterns($numberFormatElement, $format);
        $format->setPattern(self::validateRE($numberFormatElement->getAttribute(self::PATTERN)));

        $formatPattern = $numberFormatElement->getElementsByTagName(self::FORMAT);
        if ($formatPattern->length !== 1) {
            $countryId = $metadata->getId() !== '' ? $metadata->getId() : $metadata->getCountryCode();
            throw new RuntimeException('Invalid number of format patterns for country: ' . $countryId);
        }
        $nationalFormat = $formatPattern->item(0)->firstChild->nodeValue;
        $format->setFormat($nationalFormat);
    }

    public static function setLeadingDigitsPatterns(DOMElement $numberFormatElement, NumberFormat $format): void
    {
        $leadingDigitsPatternNodes = $numberFormatElement->getElementsByTagName(self::LEADING_DIGITS);
        $numOfLeadingDigitsPatterns = $leadingDigitsPatternNodes->length;
        if ($numOfLeadingDigitsPatterns > 0) {
            for ($i = 0; $i < $numOfLeadingDigitsPatterns; $i++) {
                $format->addLeadingDigitsPattern(self::validateRE($leadingDigitsPatternNodes->item($i)->firstChild->nodeValue, true));
            }
        }
    }

    /**
     * Extracts the pattern for international format. If there is no intlFormat, default to using the
     * national format. If the intlFormat is set to "NA" the intlFormat should be ignored.
     *
     * @throws RuntimeException if multiple intlFormats have been encountered.
     * @return bool whether an international number format is defined.
     */
    public static function loadInternationalFormat(
        PhoneMetadataBuilder $metadata,
        DOMElement $numberFormatElement,
        NumberFormat $nationalFormat
    ): bool {
        $intlFormat = new NumberFormat();
        $intlFormatPattern = $numberFormatElement->getElementsByTagName(self::INTL_FORMAT);
        $hasExplicitIntlFormatDefined = false;

        if ($intlFormatPattern->length > 1) {
            $countryId = $metadata->getId() !== '' ? $metadata->getId() : $metadata->getCountryCode();
            throw new RuntimeException('Invalid number of intlFormat patterns for country: ' . $countryId);
        }

        if ($intlFormatPattern->length === 0) {
            // Default to use the same as the national pattern if none is defined.
            $intlFormat->mergeFrom($nationalFormat);
        } else {
            $intlFormat->setPattern($numberFormatElement->getAttribute(self::PATTERN));
            self::setLeadingDigitsPatterns($numberFormatElement, $intlFormat);
            $intlFormatPatternValue = $intlFormatPattern->item(0)->firstChild->nodeValue;
            if ($intlFormatPatternValue !== 'NA') {
                $intlFormat->setFormat($intlFormatPatternValue);
            }
            $hasExplicitIntlFormatDefined = true;
        }

        if ($intlFormat->hasFormat()) {
            $metadata->addIntlNumberFormat($intlFormat);
        }
        return $hasExplicitIntlFormatDefined;
    }

    public static function setRelevantDescPatterns(PhoneMetadataBuilder $metadata, DOMElement $element, bool $isShortNumberMetadata): void
    {
        $generalDesc = self::processPhoneNumberDescElement(null, $element, self::GENERAL_DESC);
        $metadata->setGeneralDesc($generalDesc);

        $metadataId = $metadata->getId();
        // Calculate the possible lengths for the general description. This will be based on the
        // possible lengths of the child elements.
        self::setPossibleLengthsGeneralDesc($generalDesc, $metadataId, $element, $isShortNumberMetadata);

        if (!$isShortNumberMetadata) {
            // Set fields used by regular length phone numbers.
            $metadata->setFixedLine(self::processPhoneNumberDescElement($generalDesc, $element, self::FIXED_LINE));
            $metadata->setMobile(self::processPhoneNumberDescElement($generalDesc, $element, self::MOBILE));
            $metadata->setSharedCost(self::processPhoneNumberDescElement($generalDesc, $element, self::SHARED_COST));
            $metadata->setVoip(self::processPhoneNumberDescElement($generalDesc, $element, self::VOIP));
            $metadata->setPersonalNumber(self::processPhoneNumberDescElement($generalDesc, $element, self::PERSONAL_NUMBER));
            $metadata->setPager(self::processPhoneNumberDescElement($generalDesc, $element, self::PAGER));
            $metadata->setUan(self::processPhoneNumberDescElement($generalDesc, $element, self::UAN));
            $metadata->setVoicemail(self::processPhoneNumberDescElement($generalDesc, $element, self::VOICEMAIL));
            $metadata->setNoInternationalDialling(self::processPhoneNumberDescElement($generalDesc, $element, self::NO_INTERNATIONAL_DIALLING));
            $metadata->setSameMobileAndFixedLinePattern($metadata->getMobile()->getNationalNumberPattern() === $metadata->getFixedLine()->getNationalNumberPattern());
            $metadata->setTollFree(self::processPhoneNumberDescElement($generalDesc, $element, self::TOLL_FREE));
            $metadata->setPremiumRate(self::processPhoneNumberDescElement($generalDesc, $element, self::PREMIUM_RATE));
        } else {
            // Set fields used by short numbers.
            $metadata->setStandardRate(self::processPhoneNumberDescElement($generalDesc, $element, self::STANDARD_RATE));
            $metadata->setShortCode(self::processPhoneNumberDescElement($generalDesc, $element, self::SHORT_CODE));
            $metadata->setCarrierSpecific(self::processPhoneNumberDescElement($generalDesc, $element, self::CARRIER_SPECIFIC));
            $metadata->setEmergency(self::processPhoneNumberDescElement($generalDesc, $element, self::EMERGENCY));
            $metadata->setTollFree(self::processPhoneNumberDescElement($generalDesc, $element, self::TOLL_FREE));
            $metadata->setPremiumRate(self::processPhoneNumberDescElement($generalDesc, $element, self::PREMIUM_RATE));
            $metadata->setSmsServices(self::processPhoneNumberDescElement($generalDesc, $element, self::SMS_SERVICES));
        }
    }

    /**
     * Parses a possible length string into a set of the integers that are covered.
     *
     * @param string $possibleLengthString a string specifying the possible lengths of phone numbers. Follows
     *                                     this syntax: ranges or elements are separated by commas, and ranges are specified in
     *                                     [min-max] notation, inclusive. For example, [3-5],7,9,[11-14] should be parsed to
     *                                     3,4,5,7,9,11,12,13,14
     * @return int[]
     */
    private static function parsePossibleLengthStringToSet(string $possibleLengthString): array
    {
        if ($possibleLengthString === '') {
            throw new RuntimeException('Empty possibleLength string found.');
        }

        $lengths = explode(',', $possibleLengthString);
        $lengthSet = [];


        foreach ($lengths as $iValue) {
            $lengthSubstring = $iValue;
            if ($lengthSubstring === '') {
                throw new RuntimeException('Leading, trailing or adjacent commas in possible '
                    . "length string {$possibleLengthString}, these should only separate numbers or ranges.");
            }

            if ($lengthSubstring[0] === '[') {
                if (!str_ends_with($lengthSubstring, ']')) {
                    throw new RuntimeException("Missing end of range character in possible length string {$possibleLengthString}.");
                }

                // Strip the leading and trailing [], and split on the -.
                $minMax = explode('-', substr($lengthSubstring, 1, -1));
                if (count($minMax) !== 2) {
                    throw new RuntimeException("Ranges must have exactly one - character: missing for {$possibleLengthString}.");
                }
                $min = (int) $minMax[0];
                $max = (int) $minMax[1];
                // We don't even accept [6-7] since we prefer the shorter 6,7 variant; for a range to be in
                // use the hyphen needs to replace at least one digit.
                if ($max - $min < 2) {
                    throw new RuntimeException("The first number in a range should be two or more digits lower than the second. Culprit possibleLength string: {$possibleLengthString}.");
                }
                for ($j = $min; $j <= $max; $j++) {
                    if (in_array($j, $lengthSet, true)) {
                        throw new RuntimeException("Duplicate length element found ({$j}) in possibleLength string {$possibleLengthString}.");
                    }
                    $lengthSet[] = $j;
                }
            } else {
                $length = $lengthSubstring;
                if (!is_numeric($length)) {
                    throw new RuntimeException("For input string \"{$length}\"");
                }
                if (in_array((int) $length, $lengthSet, true)) {
                    throw new RuntimeException("Duplicate length element found ({$length}) in possibleLength string {$possibleLengthString}.");
                }
                $lengthSet[] = (int) $length;
            }
        }
        return $lengthSet;
    }

    /**
     * Reads the possible length present in the metadata and splits them into two sets: one for
     * full-length numbers, one for local numbers.
     *
     *
     * @param DOMElement $data One or more phone number descriptions
     * @param int[] $lengths An array in which to add possible lengths of full phone numbers
     * @param int[] $localOnlyLengths An array in which to add possible lengths of phone numbers only diallable
     *                                locally (e.g. within a province)
     */
    private static function populatePossibleLengthSets(DOMElement $data, array &$lengths, array &$localOnlyLengths): void
    {
        $possibleLengths = $data->getElementsByTagName(self::POSSIBLE_LENGTHS);

        for ($i = 0; $i < $possibleLengths->length; $i++) {
            /** @var DOMElement $element */
            $element = $possibleLengths->item($i);
            $nationalLengths = $element->getAttribute(self::NATIONAL);
            // We don't add to the phone metadata yet, since we want to sort length elements found under
            // different nodes first, make sure there are no duplicates between them and that the
            // localOnly lengths don't overlap with the others.
            $thisElementLengths = self::parsePossibleLengthStringToSet($nationalLengths);
            if ($element->hasAttribute(self::LOCAL_ONLY)) {
                $localLengths = $element->getAttribute(self::LOCAL_ONLY);
                $thisElementLocalOnlyLengths = self::parsePossibleLengthStringToSet($localLengths);
                $intersection = array_intersect($thisElementLengths, $thisElementLocalOnlyLengths);
                if (count($intersection) > 0) {
                    throw new RuntimeException('Possible length(s) found specified as a normal and local-only length: [' . implode(',', $intersection) . '].');
                }
                // We check again when we set these lengths on the metadata itself in setPossibleLengths
                // that the elements in localOnly are not also in lengths. For e.g. the generalDesc, it
                // might have a local-only length for one type that is a normal length for another type. We
                // don't consider this an error, but we do want to remove the local-only lengths.
                $localOnlyLengths = array_merge($localOnlyLengths, $thisElementLocalOnlyLengths);
                sort($localOnlyLengths);
            }
            // It is okay if at this time we have duplicates, because the same length might be possible
            // for e.g. fixed-line and for mobile numbers, and this method operates potentially on
            // multiple phoneNumberDesc XML elements.
            $lengths = array_merge($lengths, $thisElementLengths);
            sort($lengths);
        }
    }

    /**
     * Sets possible lengths in the general description, derived from certain child elements
     */
    public static function setPossibleLengthsGeneralDesc(PhoneNumberDesc $generalDesc, ?string $metadataId, DOMElement $data, bool $isShortNumberMetadata): void
    {
        $lengths = [];
        $localOnlyLengths = [];
        // The general description node should *always* be present if metadata for other types is
        // present, aside from in some unit tests.
        // (However, for e.g. formatting metadata in PhoneNumberAlternateFormats, no PhoneNumberDesc
        // elements are present).
        $generalDescNodes = $data->getElementsByTagName(self::GENERAL_DESC);
        if ($generalDescNodes->length > 0) {
            $generalDescNode = $generalDescNodes->item(0);
            self::populatePossibleLengthSets($generalDescNode, $lengths, $localOnlyLengths);
            if (count($lengths) > 0 || count($localOnlyLengths) > 0) {
                // We shouldn't have anything specified at the "general desc" level: we are going to
                // calculate this ourselves from child elements.
                throw new RuntimeException("Found possible lengths specified at general desc: this should be derived from child elements. Affected country: {$metadataId}");
            }
        }
        if (!$isShortNumberMetadata) {
            // Make a copy here since we want to remove some nodes, but we don't want to do that on our
            // actual data.
            $allDescData = $data->cloneNode(true);
            foreach (self::$phoneNumberDescsWithoutMatchingTypes as $tag) {
                $nodesToRemove = $allDescData->getElementsByTagName($tag);
                if ($nodesToRemove->length > 0) {
                    // We check when we process phone number descriptions that there are only one of each
                    // type, so this is safe to do.
                    $allDescData->removeChild($nodesToRemove->item(0));
                }
            }
            self::populatePossibleLengthSets($allDescData, $lengths, $localOnlyLengths);
        } else {
            // For short number metadata, we want to copy the lengths from the "short code" section only.
            // This is because it's the more detailed validation pattern, it's not a sub-type of short
            // codes. The other lengths will be checked later to see that they are a sub-set of these
            // possible lengths.
            $shortCodeDescList = $data->getElementsByTagName(self::SHORT_CODE);
            if (count($shortCodeDescList) > 0) {
                $shortCodeDesc = $shortCodeDescList->item(0);
                self::populatePossibleLengthSets($shortCodeDesc, $lengths, $localOnlyLengths);
            }
            if (count($localOnlyLengths) > 0) {
                throw new RuntimeException('Found local-only lengths in short-number metadata');
            }
        }
        self::setPossibleLengths($lengths, $localOnlyLengths, null, $generalDesc);
    }

    /**
     * Sets the possible length fields in the metadata from the sets of data passed in. Checks that
     * the length is covered by the "parent" phone number description element if one is present, and
     * if the lengths are exactly the same as this, they are not filled in for efficiency reasons.
     * @param int[] $lengths
     * @param int[] $localOnlyLengths
     */
    private static function setPossibleLengths(array $lengths, array $localOnlyLengths, ?PhoneNumberDesc $parentDesc, PhoneNumberDesc $desc): void
    {
        // We clear these fields since the metadata tends to inherit from the parent element for other
        // fields (via a mergeFrom).
        $desc->clearPossibleLength();
        $desc->clearPossibleLengthLocalOnly();

        // Only add the lengths to this sub-type if they aren't exactly the same as the possible
        // lengths in the general desc (for metadata size reasons).
        if ($parentDesc === null || !self::arePossibleLengthsEqual($lengths, $parentDesc)) {
            foreach ($lengths as $length) {
                if ($parentDesc === null || in_array($length, $parentDesc->getPossibleLength(), true)) {
                    $desc->addPossibleLength($length);
                } else {
                    // We shouldn't have possible lengths defined in a child element that are not covered by
                    // the general description. We check this here even though the general description is
                    // derived from child elements because it is only derived from a subset, and we need to
                    // ensure *all* child elements have a valid possible length.
                    throw new RuntimeException("Out-of-range possible length found ({$length}), parent lengths " . implode(',', $parentDesc->getPossibleLength()));
                }
            }
        }
        // We check that the local-only length isn't also a normal possible length (only relevant for
        // the general-desc, since within elements such as fixed-line we would throw an exception if we
        // saw this) before adding it to the collection of possible local-only lengths.
        foreach ($localOnlyLengths as $length) {
            if (!in_array($length, $lengths, true)) {
                // We check it is covered by either of the possible length sets of the parent
                // PhoneNumberDesc, because for example 7 might be a valid localOnly length for mobile, but
                // a valid national length for fixedLine, so the generalDesc would have the 7 removed from
                // localOnly.
                if ($parentDesc === null
                    || in_array($length, $parentDesc->getPossibleLength(), true)
                    || in_array($length, $parentDesc->getPossibleLengthLocalOnly(), true)
                ) {
                    $desc->addPossibleLengthLocalOnly($length);
                } else {
                    $implodedLengths = implode(',', $parentDesc->getPossibleLength());
                    throw new RuntimeException("Out-of-range local-only possible length found ({$length}), parent lengths {$implodedLengths}");
                }
            }
        }
    }

    /**
     * Processes a phone number description element from the XML file and returns it as a
     * PhoneNumberDesc. If the description element is a fixed line or mobile number, the parent
     * description will be used to fill in the whole element if necessary, or any components that are
     * missing. For all other types, the parent description will only be used to fill in missing
     * components if the type has a partial definition. For example, if no "tollFree" element exists,
     * we assume there are no toll free numbers for that locale, and return a phone number description
     * with no national number data and [-1] for this possible lengths. Note that the parent
     * description must therefore already be processed before this method is called on any child
     * elements.
     *
     * @internal
     * @param PhoneNumberDesc|null $parentDesc a generic phone number description that will be used to fill in missing
     *                                         parts of the description, or null if this is the root node. This must be processed before
     *                                         this is run on any child elements.
     * @param DOMElement $countryElement XML element representing all the country information
     * @param string $numberType name of the number type, corresponding to the appropriate tag in the XML
     *                           file with information about that type
     * @return PhoneNumberDesc complete description of that phone number type
     */
    public static function processPhoneNumberDescElement(
        ?PhoneNumberDesc $parentDesc,
        DOMElement $countryElement,
        string $numberType
    ): PhoneNumberDesc {
        $phoneNumberDescList = $countryElement->getElementsByTagName($numberType);
        $numberDesc = new PhoneNumberDesc();
        if ($phoneNumberDescList->length === 0) {
            // -1 will never match a possible phone number length, so is safe to use to ensure this never
            // matches. We don't leave it empty, since for compression reasons, we use the empty list to
            // mean that the generalDesc possible lengths apply.
            $numberDesc->setPossibleLength([-1]);
            return $numberDesc;
        }

        if ($parentDesc !== null) {
            if ($parentDesc->getNationalNumberPattern() !== '') {
                $numberDesc->setNationalNumberPattern($parentDesc->getNationalNumberPattern());
            }
            if ($parentDesc->getExampleNumber() !== '') {
                $numberDesc->setExampleNumber($parentDesc->getExampleNumber());
            }
        }

        if ($phoneNumberDescList->length > 0) {
            if ($phoneNumberDescList->length > 1) {
                throw new RuntimeException("Multiple elements with type {$numberType} found.");
            }

            /** @var DOMElement $element */
            $element = $phoneNumberDescList->item(0);

            if ($parentDesc !== null) {
                // New way of handling possible number lengths. We don't do this for the general
                // description, since these tags won't be present; instead we will calculate its values
                // based on the values for all the other number type descriptions (see
                // setPossibleLengthsGeneralDesc).
                $lengths = [];
                $localOnlyLengths = [];
                self::populatePossibleLengthSets($element, $lengths, $localOnlyLengths);
                self::setPossibleLengths($lengths, $localOnlyLengths, $parentDesc, $numberDesc);
            }

            $validPattern = $element->getElementsByTagName(self::NATIONAL_NUMBER_PATTERN);
            if ($validPattern->length > 0) {
                $numberDesc->setNationalNumberPattern(self::validateRE($validPattern->item(0)->firstChild->nodeValue, true));
            }

            $exampleNumber = $element->getElementsByTagName(self::EXAMPLE_NUMBER);
            if ($exampleNumber->length > 0) {
                $numberDesc->setExampleNumber($exampleNumber->item(0)->firstChild->nodeValue);
            }
        }
        return $numberDesc;
    }

    /**
     * @param int[] $possibleLengths
     */
    private static function arePossibleLengthsEqual(array $possibleLengths, PhoneNumberDesc $desc): bool
    {
        $descPossibleLength = $desc->getPossibleLength();
        if (count($possibleLengths) !== count($descPossibleLength)) {
            return false;
        }

        // Note that both should be sorted already, and we know they are the same length.
        $i = 0;
        foreach ($possibleLengths as $length) {
            if ($length !== $descPossibleLength[$i]) {
                return false;
            }
            $i++;
        }
        return true;
    }

    /**
     * @param PhoneMetadataBuilder[] $metadataCollection
     * @return array<int|string,array<string>>
     */
    public static function buildCountryCodeToRegionCodeMap(array $metadataCollection): array
    {
        $countryCodeToRegionCodeMap = [];

        foreach ($metadataCollection as $metadata) {
            $regionCode = $metadata->getId();
            $countryCode = $metadata->getCountryCode();
            if (array_key_exists($countryCode, $countryCodeToRegionCodeMap)) {
                if ($metadata->getMainCountryForCode()) {
                    array_unshift($countryCodeToRegionCodeMap[$countryCode], $regionCode);
                } else {
                    $countryCodeToRegionCodeMap[$countryCode][] = $regionCode;
                }
            } else {
                // For most countries, there will be only one region code for the country calling code.
                $listWithRegionCode = [];
                if ($regionCode !== '') { // For alternate formats, there are no region codes at all.
                    $listWithRegionCode[] = $regionCode;
                }
                $countryCodeToRegionCodeMap[$countryCode] = $listWithRegionCode;
            }
        }

        return $countryCodeToRegionCodeMap;
    }
}