9.negotiation.js

// Sect 9.2 Abstract Operations
// ============================

import {
    List,
    toObject,
    toLength,
    arrIndexOf,
    arrPush,
    arrSlice,
    Record,
    hop,
    defineProperty
} from "./util.js";

import {
    IsStructurallyValidLanguageTag,
    CanonicalizeLanguageTag,
    DefaultLocale
} from "./6.locales-currencies-tz.js";

const expUnicodeExSeq = /-u(?:-[0-9a-z]{2,8})+/gi; // See `extension` below

export function /* 9.2.1 */CanonicalizeLocaleList (locales) {
// The abstract operation CanonicalizeLocaleList takes the following steps:

    // 1. If locales is undefined, then a. Return a new empty List
    if (locales === undefined)
        return new List();

    // 2. Let seen be a new empty List.
    let seen = new List();

    // 3. If locales is a String value, then
    //    a. Let locales be a new array created as if by the expression new
    //    Array(locales) where Array is the standard built-in constructor with
    //    that name and locales is the value of locales.
    locales = typeof locales === 'string' ? [ locales ] : locales;

    // 4. Let O be ToObject(locales).
    let O = toObject(locales);

    // 5. Let lenValue be the result of calling the [[Get]] internal method of
    //    O with the argument "length".
    // 6. Let len be ToUint32(lenValue).
    let len = toLength(O.length);

    // 7. Let k be 0.
    let k = 0;

    // 8. Repeat, while k < len
    while (k < len) {
        // a. Let Pk be ToString(k).
        let Pk = String(k);

        // b. Let kPresent be the result of calling the [[HasProperty]] internal
        //    method of O with argument Pk.
        let kPresent = Pk in O;

        // c. If kPresent is true, then
        if (kPresent) {
            // i. Let kValue be the result of calling the [[Get]] internal
            //     method of O with argument Pk.
            let kValue = O[Pk];

            // ii. If the type of kValue is not String or Object, then throw a
            //     TypeError exception.
            if (kValue === null || (typeof kValue !== 'string' && typeof kValue !== 'object'))
                throw new TypeError('String or Object type expected');

            // iii. Let tag be ToString(kValue).
            let tag = String(kValue);

            // iv. If the result of calling the abstract operation
            //     IsStructurallyValidLanguageTag (defined in 6.2.2), passing tag as
            //     the argument, is false, then throw a RangeError exception.
            if (!IsStructurallyValidLanguageTag(tag))
                throw new RangeError("'" + tag + "' is not a structurally valid language tag");

            // v. Let tag be the result of calling the abstract operation
            //    CanonicalizeLanguageTag (defined in 6.2.3), passing tag as the
            //    argument.
            tag = CanonicalizeLanguageTag(tag);

            // vi. If tag is not an element of seen, then append tag as the last
            //     element of seen.
            if (arrIndexOf.call(seen, tag) === -1)
                arrPush.call(seen, tag);
        }

        // d. Increase k by 1.
        k++;
    }

    // 9. Return seen.
    return seen;
}

/**
 * The BestAvailableLocale abstract operation compares the provided argument
 * locale, which must be a String value with a structurally valid and
 * canonicalized BCP 47 language tag, against the locales in availableLocales and
 * returns either the longest non-empty prefix of locale that is an element of
 * availableLocales, or undefined if there is no such element. It uses the
 * fallback mechanism of RFC 4647, section 3.4. The following steps are taken:
 */
export function /* 9.2.2 */BestAvailableLocale (availableLocales, locale) {
    // 1. Let candidate be locale
    let candidate = locale;

    // 2. Repeat
    while (candidate) {
        // a. If availableLocales contains an element equal to candidate, then return
        // candidate.
        if (arrIndexOf.call(availableLocales, candidate) > -1)
            return candidate;

        // b. Let pos be the character index of the last occurrence of "-"
        // (U+002D) within candidate. If that character does not occur, return
        // undefined.
        let pos = candidate.lastIndexOf('-');

        if (pos < 0)
            return;

        // c. If pos ≥ 2 and the character "-" occurs at index pos-2 of candidate,
        //    then decrease pos by 2.
        if (pos >= 2 && candidate.charAt(pos - 2) === '-')
            pos -= 2;

        // d. Let candidate be the substring of candidate from position 0, inclusive,
        //    to position pos, exclusive.
        candidate = candidate.substring(0, pos);
    }
}

/**
 * The LookupMatcher abstract operation compares requestedLocales, which must be
 * a List as returned by CanonicalizeLocaleList, against the locales in
 * availableLocales and determines the best available language to meet the
 * request. The following steps are taken:
 */
export function /* 9.2.3 */LookupMatcher (availableLocales, requestedLocales) {
    // 1. Let i be 0.
    let i = 0;

    // 2. Let len be the number of elements in requestedLocales.
    let len = requestedLocales.length;

    // 3. Let availableLocale be undefined.
    let availableLocale;

    let locale, noExtensionsLocale;

    // 4. Repeat while i < len and availableLocale is undefined:
    while (i < len && !availableLocale) {
        // a. Let locale be the element of requestedLocales at 0-origined list
        //    position i.
        locale = requestedLocales[i];

        // b. Let noExtensionsLocale be the String value that is locale with all
        //    Unicode locale extension sequences removed.
        noExtensionsLocale = String(locale).replace(expUnicodeExSeq, '');

        // c. Let availableLocale be the result of calling the
        //    BestAvailableLocale abstract operation (defined in 9.2.2) with
        //    arguments availableLocales and noExtensionsLocale.
        availableLocale = BestAvailableLocale(availableLocales, noExtensionsLocale);

        // d. Increase i by 1.
        i++;
    }

    // 5. Let result be a new Record.
    let result = new Record();

    // 6. If availableLocale is not undefined, then
    if (availableLocale !== undefined) {
        // a. Set result.[[locale]] to availableLocale.
        result['[[locale]]'] = availableLocale;

        // b. If locale and noExtensionsLocale are not the same String value, then
        if (String(locale) !== String(noExtensionsLocale)) {
            // i. Let extension be the String value consisting of the first
            //    substring of locale that is a Unicode locale extension sequence.
            let extension = locale.match(expUnicodeExSeq)[0];

            // ii. Let extensionIndex be the character position of the initial
            //     "-" of the first Unicode locale extension sequence within locale.
            let extensionIndex = locale.indexOf('-u-');

            // iii. Set result.[[extension]] to extension.
            result['[[extension]]'] = extension;

            // iv. Set result.[[extensionIndex]] to extensionIndex.
            result['[[extensionIndex]]'] = extensionIndex;
        }
    }
    // 7. Else
    else
        // a. Set result.[[locale]] to the value returned by the DefaultLocale abstract
        //    operation (defined in 6.2.4).
        result['[[locale]]'] = DefaultLocale();

    // 8. Return result
    return result;
}

/**
 * The BestFitMatcher abstract operation compares requestedLocales, which must be
 * a List as returned by CanonicalizeLocaleList, against the locales in
 * availableLocales and determines the best available language to meet the
 * request. The algorithm is implementation dependent, but should produce results
 * that a typical user of the requested locales would perceive as at least as
 * good as those produced by the LookupMatcher abstract operation. Options
 * specified through Unicode locale extension sequences must be ignored by the
 * algorithm. Information about such subsequences is returned separately.
 * The abstract operation returns a record with a [[locale]] field, whose value
 * is the language tag of the selected locale, which must be an element of
 * availableLocales. If the language tag of the request locale that led to the
 * selected locale contained a Unicode locale extension sequence, then the
 * returned record also contains an [[extension]] field whose value is the first
 * Unicode locale extension sequence, and an [[extensionIndex]] field whose value
 * is the index of the first Unicode locale extension sequence within the request
 * locale language tag.
 */
export function /* 9.2.4 */BestFitMatcher (availableLocales, requestedLocales) {
    return LookupMatcher(availableLocales, requestedLocales);
}

// @spec[tc39/ecma402/master/spec/negotiation.html]
// @clause[sec-unicodeextensionsubtags]
export function UnicodeExtensionSubtags(extension) {
    // 1. Let size be the number of elements in extension.
    let size = extension.length;
    // 2. If size = 0, then
    if (size === 0) {
        // a. Return « ».
        return [];
    }
    // 3. Let extensionSubtags be « ».
    let extensionSubtags = [];
    // 4. Let attribute be true.
    let attribute = true;
    // 5. Let q be 3.
    let q = 3;
    // 6. Let p be q.
    let p = q;
    // 7. Let t be q.
    let t = q;
    // 8. Repeat, while q < size
    while (q < size) {
        // a. Let c be the code unit value of the element at index q in the String extension.
        let c = extension.codePointAt(q);
        // a. If c is 0x002D (HYPHEN-MINUS), then
        if (c === 0x002D) {
            // i. If q - p = 2, then
            if (q - p === 2) {
                // 1. If p - t > 1, then
                if (p - t > 1) {
                    // a. Let type be a String value equal to the substring of extension consisting of the code units at indices t (inclusive) through p - 1 (exclusive).
                    let type = extension.substring(t, p - 1);
                    // a. Append type as the last element of extensionSubtags.
                    extensionSubtags.push(type);
                }
                // 2. Let key be a String value equal to the substring of extension consisting of the code units at indices p (inclusive) through q (exclusive).
                let key = extension.substring(p, q);
                // 3. Append key as the last element of extensionSubtags.
                extensionSubtags.push(key);
                // 4. Let t be q + 1.
                t = q + 1;
                // 5. Let attribute be false.
                attribute = false;
            // ii. Else if attribute is true, then
            } else if (attribute === true) {
                // 1. Let attr be a String value equal to the substring of extension consisting of the code units at indices p (inclusive) through q (exclusive).
                let attr = extension.substring(p, q);
                // 2. Append attr as the last element of extensionSubtags.
                extensionSubtags.push(attr);
                // 3. Let t be q + 1.
                t = q + 1;
            }
            // iii. Let p be q + 1.
            p = q + 1;
        }
        // a. Let q be q + 1.
        q = q + 1;
    }
    // 9. If size - p = 2, then
    if (size - p === 2) {
        // a. If p - t > 1, then
        if (p - t > 1) {
            // i. Let type be a String value equal to the substring of extension consisting of the code units at indices t (inclusive) through p - 1 (exclusive).
            let type = extension.substring(t, p - 1);
            // ii. Append type as the last element of extensionSubtags.
            extensionSubtags.push(type);
        }
        // a. Let t be p.
        t = p;
    }
    // 10. Let tail be a String value equal to the substring of extension consisting of the code units at indices t (inclusive) through size (exclusive).
    let tail = extension.substring(t, size);
    // 11. Append tail as the last element of extensionSubtags.
    extensionSubtags.push(tail);
    // 12. Return extensionSubtags.
    return extensionSubtags;
}

/**
 * The ResolveLocale abstract operation compares a BCP 47 language priority list
 * requestedLocales against the locales in availableLocales and determines the
 * best available language to meet the request. availableLocales and
 * requestedLocales must be provided as List values, options as a Record.
 */
export function /* 9.2.5 */ResolveLocale (availableLocales, requestedLocales, options, relevantExtensionKeys, localeData) {
    if (availableLocales.length === 0) {
        throw new ReferenceError('No locale data has been provided for this object yet.');
    }

    // The following steps are taken:
    // 1. Let matcher be the value of options.[[localeMatcher]].
    let matcher = options['[[localeMatcher]]'];

    let r;

    // 2. If matcher is "lookup", then
    if (matcher === 'lookup')
        // a. Let r be the result of calling the LookupMatcher abstract operation
        //    (defined in 9.2.3) with arguments availableLocales and
        //    requestedLocales.
        r = LookupMatcher(availableLocales, requestedLocales);

    // 3. Else
    else
        // a. Let r be the result of calling the BestFitMatcher abstract
        //    operation (defined in 9.2.4) with arguments availableLocales and
        //    requestedLocales.
        r = BestFitMatcher(availableLocales, requestedLocales);

    // 4. Let foundLocale be the value of r.[[locale]].
    let foundLocale = r['[[locale]]'];

    let extensionSubtags, extensionSubtagsLength;

    // 5. If r has an [[extension]] field, then
    if (hop.call(r, '[[extension]]')) {
        // a. Let extension be the value of r.[[extension]].
        let extension = r['[[extension]]'];
        // b. Let _extensionSubtags_ be
        // CreateArrayFromList(UnicodeExtensionSubtags(_extension_)).
        extensionSubtags = UnicodeExtensionSubtags(extension);
        // c. Let _extensionSubtagsLength_ be Get(_extensionSubtags_, *"length"*)
        extensionSubtagsLength = extensionSubtags.length;
    }

    // 6. Let result be a new Record.
    let result = new Record();

    // 7. Set result.[[dataLocale]] to foundLocale.
    result['[[dataLocale]]'] = foundLocale;

    // 8. Let supportedExtension be "-u".
    let supportedExtension = '-u';
    // 9. Let i be 0.
    let i = 0;
    // 10. Let len be the result of calling the [[Get]] internal method of
    //     relevantExtensionKeys with argument "length".
    let len = relevantExtensionKeys.length;

    // 11 Repeat while i < len:
    while (i < len) {
        // a. Let key be the result of calling the [[Get]] internal method of
        //    relevantExtensionKeys with argument ToString(i).
        let key = relevantExtensionKeys[i];
        // b. Let foundLocaleData be the result of calling the [[Get]] internal
        //    method of localeData with the argument foundLocale.
        let foundLocaleData = localeData[foundLocale];
        // c. Let keyLocaleData be the result of calling the [[Get]] internal
        //    method of foundLocaleData with the argument key.
        let keyLocaleData = foundLocaleData[key];
        // d. Let value be the result of calling the [[Get]] internal method of
        //    keyLocaleData with argument "0".
        let value = keyLocaleData['0'];
        // e. Let supportedExtensionAddition be "".
        let supportedExtensionAddition = '';
        // f. Let indexOf be the standard built-in function object defined in
        //    ES5, 15.4.4.14.
        let indexOf = arrIndexOf;

        // g. If extensionSubtags is not undefined, then
        if (extensionSubtags !== undefined) {
            // i. Let keyPos be the result of calling the [[Call]] internal
            //    method of indexOf with extensionSubtags as the this value and
            // an argument list containing the single item key.
            let keyPos = indexOf.call(extensionSubtags, key);

            // ii. If keyPos ≠ -1, then
            if (keyPos !== -1) {
                // 1. If keyPos + 1 < extensionSubtagsLength and the length of the
                //    result of calling the [[Get]] internal method of
                //    extensionSubtags with argument ToString(keyPos +1) is greater
                //    than 2, then
                if (keyPos + 1 < extensionSubtagsLength
                        && extensionSubtags[keyPos + 1].length > 2) {
                    // a. Let requestedValue be the result of calling the [[Get]]
                    //    internal method of extensionSubtags with argument
                    //    ToString(keyPos + 1).
                    let requestedValue = extensionSubtags[keyPos + 1];
                    // b. Let valuePos be the result of calling the [[Call]]
                    //    internal method of indexOf with keyLocaleData as the
                    //    this value and an argument list containing the single
                    //    item requestedValue.
                    let valuePos = indexOf.call(keyLocaleData, requestedValue);

                    // c. If valuePos ≠ -1, then
                    if (valuePos !== -1) {
                        // i. Let value be requestedValue.
                        value = requestedValue,
                        // ii. Let supportedExtensionAddition be the
                        //     concatenation of "-", key, "-", and value.
                        supportedExtensionAddition = '-' + key + '-' + value;
                    }
                }
                // 2. Else
                else {
                    // a. Let valuePos be the result of calling the [[Call]]
                    // internal method of indexOf with keyLocaleData as the this
                    // value and an argument list containing the single item
                    // "true".
                    let valuePos = indexOf(keyLocaleData, 'true');

                    // b. If valuePos ≠ -1, then
                    if (valuePos !== -1)
                        // i. Let value be "true".
                        value = 'true';
                }
            }
        }
        // h. If options has a field [[<key>]], then
        if (hop.call(options, '[[' + key + ']]')) {
            // i. Let optionsValue be the value of options.[[<key>]].
            let optionsValue = options['[[' + key + ']]'];

            // ii. If the result of calling the [[Call]] internal method of indexOf
            //     with keyLocaleData as the this value and an argument list
            //     containing the single item optionsValue is not -1, then
            if (indexOf.call(keyLocaleData, optionsValue) !== -1) {
                // 1. If optionsValue is not equal to value, then
                if (optionsValue !== value) {
                    // a. Let value be optionsValue.
                    value = optionsValue;
                    // b. Let supportedExtensionAddition be "".
                    supportedExtensionAddition = '';
                }
            }
        }
        // i. Set result.[[<key>]] to value.
        result['[[' + key + ']]'] = value;

        // j. Append supportedExtensionAddition to supportedExtension.
        supportedExtension += supportedExtensionAddition;

        // k. Increase i by 1.
        i++;
    }
    // 12. If the length of supportedExtension is greater than 2, then
    if (supportedExtension.length > 2) {
        // a.
        let privateIndex = foundLocale.indexOf("-x-");
        // b.
        if (privateIndex === -1) {
            // i.
            foundLocale = foundLocale + supportedExtension;
        }
        // c.
        else {
            // i.
            let preExtension = foundLocale.substring(0, privateIndex);
            // ii.
            let postExtension = foundLocale.substring(privateIndex);
            // iii.
            foundLocale = preExtension + supportedExtension + postExtension;
        }
        // d. asserting - skipping
        // e.
        foundLocale = CanonicalizeLanguageTag(foundLocale);
    }
    // 13. Set result.[[locale]] to foundLocale.
    result['[[locale]]'] = foundLocale;

    // 14. Return result.
    return result;
}

/**
 * The LookupSupportedLocales abstract operation returns the subset of the
 * provided BCP 47 language priority list requestedLocales for which
 * availableLocales has a matching locale when using the BCP 47 Lookup algorithm.
 * Locales appear in the same order in the returned list as in requestedLocales.
 * The following steps are taken:
 */
export function /* 9.2.6 */LookupSupportedLocales (availableLocales, requestedLocales) {
    // 1. Let len be the number of elements in requestedLocales.
    let len = requestedLocales.length;
    // 2. Let subset be a new empty List.
    let subset = new List();
    // 3. Let k be 0.
    let k = 0;

    // 4. Repeat while k < len
    while (k < len) {
        // a. Let locale be the element of requestedLocales at 0-origined list
        //    position k.
        let locale = requestedLocales[k];
        // b. Let noExtensionsLocale be the String value that is locale with all
        //    Unicode locale extension sequences removed.
        let noExtensionsLocale = String(locale).replace(expUnicodeExSeq, '');
        // c. Let availableLocale be the result of calling the
        //    BestAvailableLocale abstract operation (defined in 9.2.2) with
        //    arguments availableLocales and noExtensionsLocale.
        let availableLocale = BestAvailableLocale(availableLocales, noExtensionsLocale);

        // d. If availableLocale is not undefined, then append locale to the end of
        //    subset.
        if (availableLocale !== undefined)
            arrPush.call(subset, locale);

        // e. Increment k by 1.
        k++;
    }

    // 5. Let subsetArray be a new Array object whose elements are the same
    //    values in the same order as the elements of subset.
    let subsetArray = arrSlice.call(subset);

    // 6. Return subsetArray.
    return subsetArray;
}

/**
 * The BestFitSupportedLocales abstract operation returns the subset of the
 * provided BCP 47 language priority list requestedLocales for which
 * availableLocales has a matching locale when using the Best Fit Matcher
 * algorithm. Locales appear in the same order in the returned list as in
 * requestedLocales. The steps taken are implementation dependent.
 */
export function /*9.2.7 */BestFitSupportedLocales (availableLocales, requestedLocales) {
    // ###TODO: implement this function as described by the specification###
    return LookupSupportedLocales(availableLocales, requestedLocales);
}

/**
 * The SupportedLocales abstract operation returns the subset of the provided BCP
 * 47 language priority list requestedLocales for which availableLocales has a
 * matching locale. Two algorithms are available to match the locales: the Lookup
 * algorithm described in RFC 4647 section 3.4, and an implementation dependent
 * best-fit algorithm. Locales appear in the same order in the returned list as
 * in requestedLocales. The following steps are taken:
 */
export function /*9.2.8 */SupportedLocales (availableLocales, requestedLocales, options) {
    let matcher, subset;

    // 1. If options is not undefined, then
    if (options !== undefined) {
        // a. Let options be ToObject(options).
        options = new Record(toObject(options));
        // b. Let matcher be the result of calling the [[Get]] internal method of
        //    options with argument "localeMatcher".
        matcher = options.localeMatcher;

        // c. If matcher is not undefined, then
        if (matcher !== undefined) {
            // i. Let matcher be ToString(matcher).
            matcher = String(matcher);

            // ii. If matcher is not "lookup" or "best fit", then throw a RangeError
            //     exception.
            if (matcher !== 'lookup' && matcher !== 'best fit')
                throw new RangeError('matcher should be "lookup" or "best fit"');
        }
    }
    // 2. If matcher is undefined or "best fit", then
    if (matcher === undefined || matcher === 'best fit')
        // a. Let subset be the result of calling the BestFitSupportedLocales
        //    abstract operation (defined in 9.2.7) with arguments
        //    availableLocales and requestedLocales.
        subset = BestFitSupportedLocales(availableLocales, requestedLocales);
    // 3. Else
    else
        // a. Let subset be the result of calling the LookupSupportedLocales
        //    abstract operation (defined in 9.2.6) with arguments
        //    availableLocales and requestedLocales.
        subset = LookupSupportedLocales(availableLocales, requestedLocales);

    // 4. For each named own property name P of subset,
    for (let P in subset) {
        if (!hop.call(subset, P))
            continue;

        // a. Let desc be the result of calling the [[GetOwnProperty]] internal
        //    method of subset with P.
        // b. Set desc.[[Writable]] to false.
        // c. Set desc.[[Configurable]] to false.
        // d. Call the [[DefineOwnProperty]] internal method of subset with P, desc,
        //    and true as arguments.
        defineProperty(subset, P, {
            writable: false, configurable: false, value: subset[P]
        });
    }

    // 5. repeat the above operation for the length property,
    //    since length is not enumerable in a List.
    //    This is by design as it matches the behavior of Array.
    defineProperty(subset, 'length', {
        writable: false, configurable: false, value: subset.length
    });


    // 6. Return subset
    return subset;
}

/**
 * The GetOption abstract operation extracts the value of the property named
 * property from the provided options object, converts it to the required type,
 * checks whether it is one of a List of allowed values, and fills in a fallback
 * value if necessary.
 */
export function /*9.2.9 */GetOption (options, property, type, values, fallback) {
    // 1. Let value be the result of calling the [[Get]] internal method of
    //    options with argument property.
    let value = options[property];

    // 2. If value is not undefined, then
    if (value !== undefined) {
        // a. Assert: type is "boolean" or "string".
        // b. If type is "boolean", then let value be ToBoolean(value).
        // c. If type is "string", then let value be ToString(value).
        value = type === 'boolean' ? Boolean(value)
                  : (type === 'string' ? String(value) : value);

        // d. If values is not undefined, then
        if (values !== undefined) {
            // i. If values does not contain an element equal to value, then throw a
            //    RangeError exception.
            if (arrIndexOf.call(values, value) === -1)
                throw new RangeError("'" + value + "' is not an allowed value for `" + property +'`');
        }

        // e. Return value.
        return value;
    }
    // Else return fallback.
    return fallback;
}

/**
 * The GetNumberOption abstract operation extracts a property value from the
 * provided options object, converts it to a Number value, checks whether it is
 * in the allowed range, and fills in a fallback value if necessary.
 */
export function /* 9.2.10 */GetNumberOption (options, property, minimum, maximum, fallback) {
    // 1. Let value be the result of calling the [[Get]] internal method of
    //    options with argument property.
    let value = options[property];

    // 2. If value is not undefined, then
    if (value !== undefined) {
        // a. Let value be ToNumber(value).
        value = Number(value);

        // b. If value is NaN or less than minimum or greater than maximum, throw a
        //    RangeError exception.
        if (isNaN(value) || value < minimum || value > maximum)
            throw new RangeError('Value is not a number or outside accepted range');

        // c. Return floor(value).
        return Math.floor(value);
    }
    // 3. Else return fallback.
    return fallback;
}