Jyotisha/frontend/src/lib/current-subject.ts

"use client";

import { useSyncExternalStore } from "react";

import { fetchAccount, fetchCloudChartLibrary } from "@/lib/home-cloud-sync";
import { readProfile, upsertSelfChart } from "@/lib/home-profile";
import type { ChartLibraryRecord } from "@/lib/home-types";

const SELF_SUBJECT_ID = "self";

let accountId = "";
let subjectId = SELF_SUBJECT_ID;
let catalogReady = false;
const listeners = new Set<() => void>();

export function currentSubjectStorageKey(id: string): string {
  return `jyotisha_current_subject:${id}`;
}

export function readCurrentSubjectId(): string {
  return subjectId;
}

export function currentSubjectCatalogReady(): boolean {
  return catalogReady;
}

export function subscribeCurrentSubject(listener: () => void): () => void {
  listeners.add(listener);
  return () => {
    listeners.delete(listener);
  };
}

function emit(): void {
  for (const listener of listeners) listener();
}

export function setCurrentSubject(next: string): void {
  const id = next.trim() || SELF_SUBJECT_ID;
  if (id === subjectId) return;
  subjectId = id;
  if (accountId && typeof localStorage !== "undefined") {
    localStorage.setItem(currentSubjectStorageKey(accountId), id);
  }
  emit();
}

/**
 * `knownOtherIds === null` means the archive has not loaded yet, so a stored
 * id is kept. Once ids are known, an id that is not in the archive falls
 * back to self.
 */
export function bindCurrentSubjectAccount(nextAccountId: string, knownOtherIds: readonly string[] | null): void {
  accountId = nextAccountId;
  if (!nextAccountId || typeof localStorage === "undefined") {
    catalogReady = knownOtherIds !== null;
    if (subjectId !== SELF_SUBJECT_ID) {
      subjectId = SELF_SUBJECT_ID;
      emit();
    }
    return;
  }
  localStorage.removeItem(`jyotisha_active_chart:${nextAccountId}`);
  const stored = localStorage.getItem(currentSubjectStorageKey(nextAccountId)) || SELF_SUBJECT_ID;
  const valid = stored === SELF_SUBJECT_ID || knownOtherIds === null || knownOtherIds.includes(stored);
  const next = valid ? stored : SELF_SUBJECT_ID;
  if (!valid) localStorage.setItem(currentSubjectStorageKey(nextAccountId), SELF_SUBJECT_ID);
  catalogReady = knownOtherIds !== null;
  if (next !== subjectId || knownOtherIds !== null) {
    subjectId = next;
    emit();
  }
}

export function useCurrentSubject(): string {
  return useSyncExternalStore(subscribeCurrentSubject, readCurrentSubjectId, () => SELF_SUBJECT_ID);
}

let catalogRequest: Promise<ChartLibraryRecord[]> | null = null;
let catalogAccountId = "";

export function resetSubjectCatalogForTests(): void {
  catalogRequest = null;
  catalogAccountId = "";
  accountId = "";
  subjectId = SELF_SUBJECT_ID;
  catalogReady = false;
}

export function loadSubjectCatalog(force = false): Promise<ChartLibraryRecord[]> {
  if (!force && catalogRequest && catalogAccountId) return catalogRequest;
  catalogRequest = Promise.all([
    fetchAccount(),
    fetchCloudChartLibrary(),
  ]).then(([account, others]) => {
    const self = readProfile(account.profile);
    const library = upsertSelfChart(others.filter((record) => record.role === "other"), self);
    catalogAccountId = account.user.id;
    bindCurrentSubjectAccount(
      account.user.id,
      library.filter((record) => record.role === "other").map((record) => record.id),
    );
    return library;
  }).catch((error: unknown) => {
    catalogRequest = null;
    throw error;
  });
  return catalogRequest;
}