Function evaluateJsonProgram

typescript/src/ts/program.ts:147–186

(program: Program, onCall: (func: string, args: unknown[]) => Promise<unknown>)

 * @returns A `Promise` with the value of the last expression in the program.
 */
export async function evaluateJsonProgram(program: Program, onCall: (func: string, args: unknown[]) => Promise<unknown>) {
    const results: unknown[] = [];
    for (const expr of program["@steps"]) {
        results.push(await evaluate(expr));
    }
    return results.length > 0 ? results[results.length - 1] : undefined;

    async function evaluate(expr: unknown): Promise<unknown> {
        return typeof expr === "object" && expr !== null ?
            await evaluateObject(expr as Record<string, unknown>) :
            expr;
    }

    async function evaluateObject(obj: Record<string, unknown>) {
        if (obj.hasOwnProperty("@ref")) {
            const index = obj["@ref"];
            if (typeof index === "number" && index < results.length) {
                return results[index];
            }
        }
        else if (obj.hasOwnProperty("@func")) {
            const func = obj["@func"];
            const args = obj.hasOwnProperty("@args") ? obj["@args"] : [];
            if (typeof func === "string" && Array.isArray(args)) {
                return await onCall(func, await evaluateArray(args));
            }
        }
        else if (Array.isArray(obj)) {
            return evaluateArray(obj);
        }
        else {
            const values = await Promise.all(Object.values(obj).map(evaluate));
            return Object.fromEntries(Object.keys(obj).map((k, i) => [k, values[i]]));
        }
    }

    function evaluateArray(array: unknown[]) {
        return Promise.all(array.map(evaluate));
    }
}

/**
 * Creates an object that can translate natural language requests into simple programs, represented as JSON, that compose