import { clientStore, config, datastore, editor, index } from "@silverbulletmd/silverbullet/syscalls";
import { convertIcsCalendar, type IcsCalendar, type IcsEvent, type IcsDateObjects } from "ts-ics";

const VERSION = "0.2.11";
const CACHE_KEY = "icalendar:lastSync";
const DEFAULT_CACHE_DURATION_SECONDS = 21600; // 6 hours

console.log(`[iCalendar] Plug loading (Version ${VERSION})...`);

// ============================================================================
// Types
// ============================================================================

/**
 * Recursively converts all Date objects to strings in a type
 */
type DateToString<T> = T extends Date ? string
  : T extends IcsDateObjects ? string
  : T extends object ? { [K in keyof T]: DateToString<T[K]> }
  : T extends Array<infer U> ? Array<DateToString<U>>
  : T;

/**
 * Configuration for a calendar source
 */
interface Source {
  url: string;
  name: string | undefined;
}

/**
 * Plugin configuration structure
 */
interface PlugConfig {
  sources: Source[];
  cacheDuration: number | undefined;
  tzShift: number | undefined; // Manual hour shift override
}

/**
 * Calendar event object indexed in SilverBullet
 */
interface CalendarEvent extends DateToString<IcsEvent> {
  ref: string;
  tag: "ical-event";
  sourceName: string | undefined;
}

// ============================================================================
// Utility Functions
// ============================================================================

/**
 * Custom date formatter that handles the local timezone shift correctly
 */
function localizeDate(d: Date, hourShift = 0): string {
  // Apply any manual shift requested by the user
  if (hourShift !== 0) {
    d = new Date(d.getTime() + (hourShift * 3600000));
  }

  // Get local parts based on the environment's timezone
  const pad = (n: number) => String(n).padStart(2, "0");
  
  return d.getFullYear() +
    "-" + pad(d.getMonth() + 1) +
    "-" + pad(d.getDate()) +
    "T" + pad(d.getHours()) +
    ":" + pad(d.getMinutes()) +
    ":" + pad(d.getSeconds()) +
    "." + String(d.getMilliseconds()).padStart(3, "0");
}

/**
 * Type guard for IcsDateObjects
 */
function isIcsDateObjects(obj: any): obj is IcsDateObjects {
  return obj && typeof obj === 'object' && ('date' in obj && 'type' in obj);
}

/**
 * Creates a SHA-256 hash of a string (hex encoded)
 */
async function sha256Hash(str: string): Promise<string> {
  const encoder = new TextEncoder();
  const data = encoder.encode(str);
  const hashBuffer = await crypto.subtle.digest("SHA-256", data);
  const hashArray = Array.from(new Uint8Array(hashBuffer));
  return hashArray.map(b => b.toString(16).padStart(2, "0")).join("");
}

/**
 * Recursively converts all Date objects and ISO date strings to strings
 */
function convertDatesToStrings<T>(obj: T, hourShift = 0): DateToString<T> {
  if (obj === null || obj === undefined) {
    return obj as DateToString<T>;
  }

  if (obj instanceof Date) {
    return localizeDate(obj, hourShift) as DateToString<T>;
  }
  
  if (isIcsDateObjects(obj) && obj.date instanceof Date) {
    // If ts-ics gave us a nested 'local' object, prioritize it but treat it as the base time
    const baseDate = (obj as any).local?.date instanceof Date ? (obj as any).local.date : obj.date;
    return localizeDate(baseDate, hourShift) as DateToString<T>;
  }

  if (typeof obj === 'string' && /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}/.test(obj)) {
    // Ensure it's treated as UTC if it doesn't have a timezone marking
    const forcedUTC = obj.endsWith("Z") ? obj : obj + "Z";
    return localizeDate(new Date(forcedUTC), hourShift) as DateToString<T>;
  }

  if (Array.isArray(obj)) {
    return obj.map(item => convertDatesToStrings(item, hourShift)) as DateToString<T>;
  }

  if (typeof obj === 'object') {
    const result: any = {};
    for (const key in obj) {
      if (Object.prototype.hasOwnProperty.call(obj, key)) {
        result[key] = convertDatesToStrings((obj as any)[key], hourShift);
      }
    }
    return result as DateToString<T>;
  }

  return obj as DateToString<T>;
}

// ============================================================================
// Configuration Functions
// ============================================================================

async function getSources(): Promise<Source[]> {
  const plugConfig = await config.get<PlugConfig>("icalendar", { sources: [] });
  if (!plugConfig.sources) return [];
  let sources = plugConfig.sources;
  if (!Array.isArray(sources)) sources = [sources as unknown as Source];
  const validated: Source[] = [];
  for (const src of sources) {
    if (typeof src.url === "string") {
      validated.push({ url: src.url, name: src.name });
    }
  }
  return validated;
}

// ============================================================================
// Calendar Fetching & Parsing
// ============================================================================

async function fetchAndParseCalendar(source: Source, hourShift = 0): Promise<CalendarEvent[]> {
  let url = source.url.trim();
  if (url.includes(" ")) url = encodeURI(url);
  
  const response = await fetch(url, {
    headers: {
      "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
    }
  });

  if (!response.ok) throw new Error(`HTTP ${response.status}`);

  const icsData = await response.text();
  const calendar: IcsCalendar = convertIcsCalendar(undefined, icsData);

  if (!calendar.events) return [];

  return await Promise.all(calendar.events.map(async (icsEvent: IcsEvent): Promise<CalendarEvent> => {
    const uniqueKey = `${icsEvent.start?.date || ''}${icsEvent.uid || icsEvent.summary || ''}`;
    const ref = await sha256Hash(uniqueKey);

    return convertDatesToStrings({
      ...icsEvent,
      ref,
      tag: "ical-event" as const,
      sourceName: source.name,
    }, hourShift);
  }));
}

// ============================================================================
// Exported Commands
// ============================================================================

export async function syncCalendars() {
  try {
    const plugConfig = await config.get<PlugConfig>("icalendar", { sources: [] });
    const hourShift = plugConfig.tzShift ?? 0;
    const cacheDurationMs = (plugConfig.cacheDuration ?? DEFAULT_CACHE_DURATION_SECONDS) * 1000;

    const sources = await getSources();
    if (sources.length === 0) return;

    const lastSync = await clientStore.get(CACHE_KEY);
    const now = Date.now();

    if (lastSync && (now - lastSync) < cacheDurationMs) return;

    await editor.flashNotification("Syncing calendars...", "info");

    const allEvents: CalendarEvent[] = [];
    for (const source of sources) {
      try {
        const events = await fetchAndParseCalendar(source, hourShift);
        allEvents.push(...events);
      } catch (err) {
        console.error(`[iCalendar] Failed to sync ${source.name}:`, err);
      }
    }

    await index.indexObjects("$icalendar", allEvents);
    await clientStore.set(CACHE_KEY, now);
    await editor.flashNotification(`Synced ${allEvents.length} events`, "info");
  } catch (err) {
    console.error("[iCalendar] Sync failed:", err);
  }
}

export async function forceSync() {
  await clientStore.del(CACHE_KEY);
  await syncCalendars();
}

export async function clearCache() {
  if (!await editor.confirm("Clear all calendar events and cache?")) return;
  try {
    const pageKeys = await datastore.query({ prefix: ["ridx", "$icalendar"] });
    const allKeys: any[] = [];
    for (const { key } of pageKeys) {
      allKeys.push(key);
      allKeys.push(["idx", ...key.slice(2), "$icalendar"]);
    }
    if (allKeys.length > 0) await datastore.batchDel(allKeys);
    await clientStore.del(CACHE_KEY);
    await editor.flashNotification("Calendar index cleared", "info");
  } catch (err) {
    console.error("[iCalendar] Failed to clear cache:", err);
  }
}

export async function showVersion() {
  await editor.flashNotification(`iCalendar Plug ${VERSION}`, "info");
}