import type { Appointment, Slot } from 'fhir/r4';
import type { SaveOperation } from '../saveOperation';

export type NewBookingOutcome<Task> =
    /** The booking may have been made, but the person or dialog that asked moved on: nothing more is shown or sent. */
    | { kind: 'retired'; booked?: Appointment }
    | { kind: 'booked'; booked: Appointment; failedTasks: Task[] };

// A new booking from the desk: its time, the appointment, then its tasks. `operation` is started before the first
// wait and belongs to whoever asked, so a booking made after they were replaced is never shown to, nor finished
// under, whoever replaced them. A booking already made stands; only its continuation is dropped.
export async function bookNewAppointment<Task>(params: {
    operation: SaveOperation;
    hold: () => Promise<Slot>;
    create: (slot: Slot) => Promise<Appointment>;
    publish: (booked: Appointment) => void;
    tasks: Task[];
    assign: (booked: Appointment, tasks: Task[], operation: SaveOperation) => Promise<Task[]>;
}): Promise<NewBookingOutcome<Task>> {
    const { operation } = params;
    const slot = await params.hold();
    // An unused booking hold stores nothing and lapses on its own.
    if (!operation.belongs()) return { kind: 'retired' };
    const booked = await params.create(slot);
    if (!operation.belongs()) return { kind: 'retired', booked };
    params.publish(booked);
    if (params.tasks.length === 0) return { kind: 'booked', booked, failedTasks: [] };
    const failedTasks = await params.assign(booked, params.tasks, operation);
    if (!operation.belongs()) return { kind: 'retired', booked };
    return { kind: 'booked', booked, failedTasks };
}