import { readJson } from './fs'
import type { Fs } from './fs'
import { MATERIALS as M, WEATHER_MOOD } from './rules'

// 外部素材快取：由系統排程執行的 scripts/fetch-materials.mjs 寫入，hook 只讀、不連網。
// 只存標題、摘要、連結與時間（at 為抓取時間，毫秒）。
export type Item = { title: string; summary: string; link: string; at: number }
export type Materials = { weather: Item | null; news: Item[] }

export const EMPTY: Materials = { weather: null, news: [] }

const isItem = (x: unknown): x is Item => {
  const i = x as Item
  return !!i && typeof i.title === 'string' && typeof i.summary === 'string' && typeof i.link === 'string' && typeof i.at === 'number'
}

/** 讀快取並丟掉過期項目：天氣 6 小時、新聞 24 小時；檔案缺失或壞掉就是沒查 */
export async function readMaterials(fs: Fs, path: string, now: number): Promise<Materials> {
  const raw = await readJson<{ weather?: unknown; news?: unknown }>(fs, path)
  if (!raw) return EMPTY
  const weather = isItem(raw.weather) && now - raw.weather.at < M.weatherTtlMs ? raw.weather : null
  const news = (Array.isArray(raw.news) ? raw.news : []).filter(isItem).filter(n => now - n.at < M.newsTtlMs)
  return { weather, news }
}

/** 天氣對心情基準的微調；未知狀況為 0，且不超過上限 */
export function weatherShift(w: Item | null): number {
  if (!w) return 0
  const v = WEATHER_MOOD[w.title] ?? 0
  return Math.max(-M.weatherCap, Math.min(M.weatherCap, v))
}