import {
  firstOpenDay,
  getFriday,
  getMonday,
  getWeekNumber,
  getYearLabel,
  weekNeedsSchool,
} from "./calendar";
import { START_WEEK_NUMBER, TRAINEE } from "../data/holidays-bw";
import { WEEK_THEMES } from "../data/suggestions";

export type WeekEntry = {
  number: number;
  yearLabel: string;
  from: string;
  to: string;
  /** Flat weekly activity bullets (like original hefte) */
  activities: string[];
  frameworkRefs: string[];
  weekTheme: string;
  schoolTopics: string[];
  done: boolean;
};

export type AppState = {
  /** Monday of the current open week */
  currentWeekMonday: string;
  weeks: Record<string, WeekEntry>;
  usedSuggestionIds: number[];
};

/** Stable localStorage key – bump suffix only when AppState shape breaks compatibility. */
export const STORAGE_KEY = "berichtsheft-generator-v2";
/** Legacy key cleared on reset so old drafts do not linger. */
export const STORAGE_KEY_LEGACY = "berichtsheft-generator-v1";

const DEFAULT_FRAMEWORK = ["1.1", "1.2", "1.4", "2.1", "2.2", "2.3", "2.5", "4.4"];

export function pickTheme(exclude?: string): string {
  const pool = WEEK_THEMES.filter((t) => t !== exclude);
  const src = pool.length ? pool : WEEK_THEMES;
  return src[Math.floor(Math.random() * src.length)] || "Büroabläufe";
}

export function createEmptyWeek(monday: string): WeekEntry {
  return {
    number: getWeekNumber(monday) || START_WEEK_NUMBER,
    yearLabel: getYearLabel(monday),
    from: monday,
    to: getFriday(monday),
    activities: [],
    frameworkRefs: [...DEFAULT_FRAMEWORK],
    weekTheme: pickTheme(),
    schoolTopics: weekNeedsSchool(monday) ? [] : ["Ferien"],
    done: false,
  };
}

export function defaultState(): AppState {
  const monday = getMonday(firstOpenDay());
  return {
    currentWeekMonday: monday,
    weeks: { [monday]: createEmptyWeek(monday) },
    usedSuggestionIds: [],
  };
}

export function loadState(): AppState {
  try {
    const raw = localStorage.getItem(STORAGE_KEY);
    if (!raw) return defaultState();
    const parsed = JSON.parse(raw) as AppState;
    if (!parsed.currentWeekMonday) return defaultState();
    return {
      ...defaultState(),
      ...parsed,
      weeks: parsed.weeks ?? {},
      usedSuggestionIds: parsed.usedSuggestionIds ?? [],
    };
  } catch {
    return defaultState();
  }
}

export function saveState(state: AppState): void {
  localStorage.setItem(STORAGE_KEY, JSON.stringify(state));
}

export function ensureWeek(state: AppState, monday: string): WeekEntry {
  if (!state.weeks[monday]) {
    state.weeks[monday] = createEmptyWeek(monday);
  }
  return state.weeks[monday];
}

export function getTrainee() {
  return TRAINEE;
}

export function nextWeekMonday(monday: string): string {
  const d = new Date(monday + "T12:00:00");
  d.setDate(d.getDate() + 7);
  const y = d.getFullYear();
  const m = String(d.getMonth() + 1).padStart(2, "0");
  const day = String(d.getDate()).padStart(2, "0");
  return `${y}-${m}-${day}`;
}

export function prevWeekMonday(monday: string): string {
  const d = new Date(monday + "T12:00:00");
  d.setDate(d.getDate() - 7);
  const y = d.getFullYear();
  const m = String(d.getMonth() + 1).padStart(2, "0");
  const day = String(d.getDate()).padStart(2, "0");
  return `${y}-${m}-${day}`;
}