import type { ExecutionOptions, ExecutionResult, MathJSLabRuntime, RuntimeSession } from 'mathjslab/runtime';

/** Serialize commands into one workspace; the remote runtime recovers its Worker after timeout. */
export class CalculatorSession {
    private session: Promise<RuntimeSession> | undefined;
    private queue: Promise<unknown> = Promise.resolve();
    private disposed = false;

    public constructor(private readonly runtime: MathJSLabRuntime) {}

    public execute(source: string, options: ExecutionOptions = {}): Promise<ExecutionResult> {
        const operation = this.queue.then(async () => {
            if (this.disposed) throw new Error('Calculator session is disposed.');
            this.session ??= this.runtime.createSession({ parfor: 'fallback' }).catch((error: unknown) => {
                this.session = undefined;
                throw error;
            });
            const session = await this.session;
            return session.execute(source, { timeoutMs: 15000, ...options });
        });
        this.queue = operation.catch(() => undefined);
        return operation;
    }

    public async dispose(): Promise<void> {
        if (this.disposed) return;
        this.disposed = true;
        await this.runtime.dispose();
    }
}