import type { 
  SleepSessionCreate, 
  SleepSessionUpdate, 
  SleepSessionRead, 
  SessionListResponse,
  DailySummaryResponse,
  TimetableResponse,
  WakeupBedtimeResponse,
  SummaryResponse 
} from '@/types';

const BASE_URL = import.meta.env.VITE_API_BASE_URL || '';

/**
 * Convert a local HH:MM time string to its UTC equivalent.
 * @param hhmm - Local time as "HH:MM"
 * @returns UTC time as "HH:MM"
 */
export function localHHMMToUTCHHMM(hhmm: string): string {
  const [hours, minutes] = hhmm.split(":").map(Number);
  const offsetInMinutes = new Date().getTimezoneOffset();
  // UTC = Local - offsetInMinutes (where offset is negative for East of UTC)
  const totalMinutesUTC = (hours * 60 + minutes) + offsetInMinutes;
  const normalizedMinutes = ((totalMinutesUTC % 1440) + 1440) % 1440;
  const h = Math.floor(normalizedMinutes / 60);
  const m = normalizedMinutes % 60;
  return `${String(h).padStart(2, "0")}:${String(m).padStart(2, "0")}`;
}

export function localToUTC(localValue: string): string {
  return new Date(localValue).toISOString();
}

async function fetchStats<T>(endpoint: string, from_date: string, to_date: string, extraParams: Record<string, string> = {}): Promise<T> {
  const params = new URLSearchParams({ from_date, to_date, ...extraParams });
  const response = await fetch(`${BASE_URL}/api/stats/${endpoint}?${params.toString()}`);
  if (!response.ok) throw new Error(`Failed to fetch ${endpoint}`);
  return response.json();
}

export async function fetchSummary(from_date: string, to_date: string): Promise<SummaryResponse> {
  return fetchStats('summary', from_date, to_date);
}

export async function fetchDailySummary(from_date: string, to_date: string, day_start: string, day_end: string, timezone_offset = 0): Promise<DailySummaryResponse> {
  return fetchStats('daily-summary', from_date, to_date, { day_start, day_end, timezone_offset: timezone_offset.toString() });
}

export async function fetchTimetable(from_date: string, to_date: string, day_start: string, day_end: string, timezone_offset = 0): Promise<TimetableResponse> {
  return fetchStats('timetable', from_date, to_date, { day_start, day_end, timezone_offset: timezone_offset.toString() });
}

export async function fetchWakeSleepTimes(from_date: string, to_date: string, wakeup_ref: string, bedtime_ref: string, timezone_offset = 0): Promise<WakeupBedtimeResponse> {
  return fetchStats('wake-sleep-times', from_date, to_date, { 
    wakeup_ref: localHHMMToUTCHHMM(wakeup_ref), 
    bedtime_ref: localHHMMToUTCHHMM(bedtime_ref),
    timezone_offset: timezone_offset.toString()
  });
}

// Session API functions
export async function fetchActiveSession(): Promise<SleepSessionRead | null> {
  const response = await fetch(`${BASE_URL}/api/sessions/active`);
  if (!response.ok) return null;
  return response.json();
}

export async function fetchSessions(): Promise<SessionListResponse> {
  const response = await fetch(`${BASE_URL}/api/sessions`);
  if (!response.ok) throw new Error('Failed to fetch sessions');
  return response.json();
}

export async function createSession(payload: SleepSessionCreate): Promise<SleepSessionRead> {
  const response = await fetch(`${BASE_URL}/api/sessions`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(payload),
  });
  if (!response.ok) throw new Error('Failed to create session');
  return response.json();
}

export async function endSession(sessionId: number, payload: SleepSessionUpdate): Promise<SleepSessionRead> {
  const response = await fetch(`${BASE_URL}/api/sessions/${sessionId}/end`, {
    method: 'PATCH',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(payload),
  });
  if (!response.ok) throw new Error('Failed to end session');
  return response.json();
}

export async function deleteSession(sessionId: number): Promise<void> {
  const response = await fetch(`${BASE_URL}/api/sessions/${sessionId}`, {
    method: 'DELETE',
  });
  if (!response.ok) throw new Error('Failed to delete session');
}

export async function updateSession(sessionId: number, payload: SleepSessionUpdate): Promise<SleepSessionRead> {
  const response = await fetch(`${BASE_URL}/api/sessions/${sessionId}`, {
    method: 'PATCH',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(payload),
  });
  if (!response.ok) throw new Error('Failed to update session');
  return response.json();
}