/**
 * @module computeSubResourceCacheTTL
 *
 * Adaptive Cache TTL for Opportunity Sub-Resources
 * =================================================
 *
 * Determines how long cached sub-resource data (notes, contacts) should
 * live before being re-fetched from ConnectWise.
 *
 * Sub-resources change less frequently than the opportunity record itself
 * or its activity feed, so TTLs are longer than the primary cache. The
 * same activity-signal heuristics are used (expected close date, last
 * updated, closed status) but with relaxed durations.
 *
 * ## Spec
 *
 * | # | Condition                                                         | TTL (ms) | TTL (human) | Rationale                                                          |
 * |---|-------------------------------------------------------------------|----------|-------------|--------------------------------------------------------------------|
 * | 1 | `closedFlag` is `true` AND closed > 30 days ago                   | `null`   | Do not cache| Old closed records are rarely accessed.                            |
 * | 1b| `closedFlag` is `true` AND closed within 30 days                  | 300 000  | 5 minutes   | Recently-closed records may still be viewed occasionally.          |
 * | 2 | `expectedCloseDate` OR `lastUpdated` within **5 days**            | 60 000   | 60 seconds  | Active deals — contacts/notes may still change.                    |
 * | 3 | `expectedCloseDate` OR `lastUpdated` within **14 days**           | 120 000  | 2 minutes   | Moderate activity — less likely to change.                         |
 * | 4 | Everything else (older than 14 days)                              | 300 000  | 5 minutes   | Low activity — safe to cache longer.                               |
 *
 * ## Evaluation order
 *
 * Rules are evaluated top-to-bottom; the first matching rule wins.
 *
 * ## Inputs
 *
 * Uses the same {@link CacheTTLInput} interface as `computeCacheTTL`.
 *
 * ## Output
 *
 * Returns `number | null`:
 * - Positive integer = TTL in **milliseconds**.
 * - `null` = do **not** cache.
 */

import type { CacheTTLInput } from "./computeCacheTTL";

// ---------------------------------------------------------------------------
// Constants
// ---------------------------------------------------------------------------

/** 60 seconds — TTL for high-activity sub-resources (within 5 days). */
export const SUB_TTL_HIGH_ACTIVITY = 60_000;

/** 2 minutes — TTL for moderate-activity sub-resources (within 14 days). */
export const SUB_TTL_MODERATE_ACTIVITY = 120_000;

/** 5 minutes — TTL for low-activity / stale sub-resources. */
export const SUB_TTL_LOW_ACTIVITY = 300_000;

/** 30 days in milliseconds. */
const THIRTY_DAYS_MS = 30 * 24 * 60 * 60 * 1000;

/** 5 days in milliseconds. */
const FIVE_DAYS_MS = 5 * 24 * 60 * 60 * 1000;

/** 14 days in milliseconds. */
const FOURTEEN_DAYS_MS = 14 * 24 * 60 * 60 * 1000;

// ---------------------------------------------------------------------------
// Algorithm
// ---------------------------------------------------------------------------

/**
 * Compute the cache TTL for an opportunity sub-resource (notes, contacts).
 *
 * @param input - The opportunity's activity signals. See {@link CacheTTLInput}.
 * @returns The TTL in milliseconds, or `null` if the data should not be cached.
 */
export function computeSubResourceCacheTTL(
  input: CacheTTLInput,
): number | null {
  const {
    closedFlag,
    closedDate,
    expectedCloseDate,
    lastUpdated,
    now = new Date(),
  } = input;

  const nowMs = now.getTime();

  const isWithinWindow = (date: Date | null, windowMs: number): boolean => {
    if (!date) return false;
    return Math.abs(nowMs - date.getTime()) <= windowMs;
  };

  // Rule 1 — Closed records
  if (closedFlag) {
    if (isWithinWindow(closedDate, THIRTY_DAYS_MS)) {
      return SUB_TTL_LOW_ACTIVITY;
    }
    return null;
  }

  // Rule 2 — High activity (5 days)
  if (
    isWithinWindow(expectedCloseDate, FIVE_DAYS_MS) ||
    isWithinWindow(lastUpdated, FIVE_DAYS_MS)
  ) {
    return SUB_TTL_HIGH_ACTIVITY;
  }

  // Rule 3 — Moderate activity (14 days)
  if (
    isWithinWindow(expectedCloseDate, FOURTEEN_DAYS_MS) ||
    isWithinWindow(lastUpdated, FOURTEEN_DAYS_MS)
  ) {
    return SUB_TTL_MODERATE_ACTIVITY;
  }

  // Rule 4 — Low activity / stale
  return SUB_TTL_LOW_ACTIVITY;
}