zulip/static/js/fold_dict.ts

/*
    Use this class to manage keys where you don't care
    about case (i.e. case-insensitive).

    Keys for FoldDict should be strings.  We "fold" all
    casings of "alice" (e.g. "ALICE", "Alice", "ALIce", etc.)
    to "alice" as the key.

    Examples of case-insensitive data in Zulip are:
        - emails
        - stream names
        - topics
        - etc.
 */
type KeyValue<V> = {k: string; v: V};

export class FoldDict<V> {
    private _items: Map<string, KeyValue<V>> = new Map();

    get(key: string): V | undefined {
        const mapping = this._items.get(this._munge(key));
        if (mapping === undefined) {
            return undefined;
        }
        return mapping.v;
    }

    set(key: string, value: V): FoldDict<V> {
        this._items.set(this._munge(key), {k: key, v: value});
        return this;
    }

    has(key: string): boolean {
        return this._items.has(this._munge(key));
    }

    delete(key: string): boolean {
        return this._items.delete(this._munge(key));
    }

    *keys(): Iterator<string> {
        for (const {k} of this._items.values()) {
            yield k;
        }
    }

    *values(): Iterator<V> {
        for (const {v} of this._items.values()) {
            yield v;
        }
    }

    *[Symbol.iterator](): Iterator<[string, V]> {
        for (const {k, v} of this._items.values()) {
            yield [k, v];
        }
    }

    get size(): number {
        return this._items.size;
    }

    clear(): void {
        this._items.clear();
    }

    // Handle case-folding of keys and the empty string.
    private _munge(key: string): string {
        if (key === undefined) {
            throw new TypeError("Tried to call a FoldDict method with an undefined key.");
        }

        return key.toString().toLowerCase();
    }
}