import type { Patient } from "fhir/r4";

// A profile section saves from a fresh read, but its form was filled from the record as it stood when
// editing began. If what the section edits changed in between (a contact added from another screen,
// say), writing the form would silently delete that change, so the save is refused instead.

/** Key order carries no meaning in a FHIR resource, so it must not count as a change. */
const stable = (value: unknown): unknown => {
  if (Array.isArray(value)) return value.map(stable);
  if (value && typeof value === "object") {
    return Object.keys(value as Record<string, unknown>)
      .sort()
      .reduce<Record<string, unknown>>((out, key) => {
        const entry = (value as Record<string, unknown>)[key];
        if (entry !== undefined) out[key] = stable(entry);
        return out;
      }, {});
  }
  return value;
};

export const sectionChangedSince = (
  baseline: Patient | undefined,
  latest: Patient,
  pick: (patient: Patient) => unknown,
): boolean => {
  if (!baseline) return false;
  // Equal values on another patient are not this patient's section.
  if (baseline.id !== latest.id) return true;
  return JSON.stringify(stable(pick(baseline))) !== JSON.stringify(stable(pick(latest)));
};