@maplibre/maplibre-gl-style-spec/src/expression/definitions/collator.ts

a specification for maplibre styles

import {StringType, BooleanType, CollatorType} from '../types';
import {Collator} from '../types/collator';

import type {Expression} from '../expression';
import type {EvaluationContext} from '../evaluation_context';
import type {ParsingContext} from '../parsing_context';
import type {Type} from '../types';

export class CollatorExpression implements Expression {
    type: Type;
    caseSensitive: Expression;
    diacriticSensitive: Expression;
    locale: Expression | null;

    constructor(
        caseSensitive: Expression,
        diacriticSensitive: Expression,
        locale: Expression | null
    ) {
        this.type = CollatorType;
        this.locale = locale;
        this.caseSensitive = caseSensitive;
        this.diacriticSensitive = diacriticSensitive;
    }

    static parse(args: ReadonlyArray<unknown>, context: ParsingContext): Expression {
        if (args.length !== 2) return context.error('Expected one argument.') as null;

        const options = args[1] as any;
        if (typeof options !== 'object' || Array.isArray(options))
            return context.error('Collator options argument must be an object.') as null;

        const caseSensitive = context.parse(
            options['case-sensitive'] === undefined ? false : options['case-sensitive'],
            1,
            BooleanType
        );
        if (!caseSensitive) return null;

        const diacriticSensitive = context.parse(
            options['diacritic-sensitive'] === undefined ? false : options['diacritic-sensitive'],
            1,
            BooleanType
        );
        if (!diacriticSensitive) return null;

        let locale = null;
        if (options['locale']) {
            locale = context.parse(options['locale'], 1, StringType);
            if (!locale) return null;
        }

        return new CollatorExpression(caseSensitive, diacriticSensitive, locale);
    }

    evaluate(ctx: EvaluationContext) {
        return new Collator(
            this.caseSensitive.evaluate(ctx),
            this.diacriticSensitive.evaluate(ctx),
            this.locale ? this.locale.evaluate(ctx) : null
        );
    }

    eachChild(fn: (_: Expression) => void) {
        fn(this.caseSensitive);
        fn(this.diacriticSensitive);
        if (this.locale) {
            fn(this.locale);
        }
    }

    outputDefined() {
        // Technically the set of possible outputs is the combinatoric set of Collators produced
        // by all possible outputs of locale/caseSensitive/diacriticSensitive
        // But for the primary use of Collators in comparison operators, we ignore the Collator's
        // possible outputs anyway, so we can get away with leaving this false for now.
        return false;
    }
}