/**
 * A user's settings follow their account from browser to browser, and the
 * server reads some of them itself (a digest is drawn in its reader's style).
 * This module types them for `GET` and `PATCH /api/me/settings`; the
 * client keeps them with its session.
 *
 * @module
 */

import type { ColorScheme, StyleName } from "./theme.ts";

/**
 * Returned by `GET /api/me/settings`, and by a `PATCH` once applied.
 * The client's `useSettings` reads it from the session.
 */
export interface UserSettings {
  /**
   * Null until the user picks one, so the instance's default style
   * (`GERBEUR_DEFAULT_STYLE`) applies, and so a browser's earlier choice can be
   * carried over on first sign-in.
   */
  style: StyleName | null;
  /** Null until the user picks one, which reads as "auto". */
  colorScheme: ColorScheme | null;
  /** Whether the weekly digest is sent. */
  digestWeekly: boolean;
  /** Whether the monthly recap is sent. */
  digestMonthly: boolean;
}

/**
 * Sent to `PATCH /api/me/settings` with the settings to change; the
 * others keep their value.
 */
export type UpdateSettingsRequest = Partial<UserSettings>;

/** The settings of a user who never changed any. Digests are on by default. */
export const DEFAULT_SETTINGS: UserSettings = {
  style: null,
  colorScheme: null,
  digestWeekly: true,
  digestMonthly: true,
};

/** Lists how often a digest can come: weekly, or monthly as a recap. */
export const DIGEST_CADENCES = ["weekly", "monthly"] as const;
/**
 * One of the {@link DIGEST_CADENCES}. An unsubscribe link names one, which
 * turns off its setting alone.
 */
export type DigestCadence = typeof DIGEST_CADENCES[number];

const DAY_MS = 86_400_000;
/**
 * How long each cadence's period lasts, rolling: a digest covers the one just
 * ended, and the `/community` page the one ending now.
 */
export const PERIOD_MS: Record<DigestCadence, number> = {
  weekly: 7 * DAY_MS,
  monthly: 30 * DAY_MS,
};

/** Checks whether `value` is a {@link DigestCadence}. */
export function isDigestCadence(value: unknown): value is DigestCadence {
  return typeof value === "string" &&
    (DIGEST_CADENCES as readonly string[]).includes(value);
}

/** Names the setting that switches each cadence of digest. */
export const DIGEST_SETTING: Record<
  DigestCadence,
  "digestWeekly" | "digestMonthly"
> = {
  weekly: "digestWeekly",
  monthly: "digestMonthly",
};