import { API_ENDPOINTS } from "@/lib/api_urls";
import { getStoredTokens } from "./auth";
import type {
  CreateAppointmentInput,
  ScheduleAppointmentInput,
  RejectAppointmentInput,
  UpdateAvailabilityInput,
} from "@/lib/schema/appointments";
import type {
  Appointment,
  AppointmentResponse,
  AvailableDatesResponse,
  AdminAvailability,
  AppointmentStats,
  UserAppointmentStats,
  JitsiMeetingInfo,
  ApiError,
  WeeklyAvailabilityResponse,
  AvailabilityConfig,
  CheckDateAvailabilityResponse,
  AvailabilityOverview,
  SelectedSlot,
} from "@/lib/models/appointments";

function extractErrorMessage(error: ApiError): string {
  if (error.detail) {
    return Array.isArray(error.detail) ? error.detail.join(", ") : String(error.detail);
  }
  if (error.message) {
    return Array.isArray(error.message) ? error.message.join(", ") : String(error.message);
  }
  if (typeof error === "string") {
    return error;
  }
  return "An error occurred";
}

async function parseResponse(response: Response): Promise<any> {
  const responseText = await response.text();
  const contentType = response.headers.get("content-type") || "";

  if (!responseText || responseText.trim().length === 0) {
    if (response.ok) {
      return null;
    }
    throw new Error(`Server error (${response.status}): ${response.statusText || 'Empty response'}`);
  }

  if (contentType.includes("application/json")) {
    try {
      return JSON.parse(responseText);
    } catch {
      throw new Error(`Server error (${response.status}): Invalid JSON format`);
    }
  }

  const errorMatch = responseText.match(/<pre[^>]*>([\s\S]*?)<\/pre>/i) || 
                    responseText.match(/<h1[^>]*>([\s\S]*?)<\/h1>/i);
  const errorText = errorMatch?.[1]?.replace(/<[^>]*>/g, '').trim() || '';
  throw new Error(`Server error (${response.status}): ${errorText || response.statusText || 'Internal Server Error'}`);
}

function extractHtmlError(responseText: string): string {
  const errorMatch = responseText.match(/<pre[^>]*>([\s\S]*?)<\/pre>/i);
  if (!errorMatch) return '';
  
  const traceback = errorMatch[1].replace(/<[^>]*>/g, '');
  const lines = traceback.split('\n').filter(line => line.trim());
  
  for (let i = lines.length - 1; i >= Math.max(0, lines.length - 5); i--) {
    const line = lines[i];
    if (line.match(/(Error|Exception|Failed)/i)) {
      return line.trim().replace(/^(Traceback|File|Error|Exception):\s*/i, '');
    }
  }
  
  return lines[lines.length - 1]?.trim() || '';
}

function validateAndCleanSlots(slots: any[]): SelectedSlot[] {
  return slots
    .filter(slot => {
      if (!slot || typeof slot !== 'object') return false;
      const dayNum = Number(slot.day);
      const timeSlot = String(slot.time_slot || '').toLowerCase().trim();
      return !isNaN(dayNum) && dayNum >= 0 && dayNum <= 6 && 
             ['morning', 'afternoon', 'evening'].includes(timeSlot);
    })
    .map(slot => ({
      day: Number(slot.day),
      time_slot: String(slot.time_slot).toLowerCase().trim() as "morning" | "afternoon" | "evening",
    }));
}

function normalizeAvailabilitySchedule(schedule: any): Record<string, string[]> {
  if (typeof schedule === 'string') {
    try {
      schedule = JSON.parse(schedule);
    } catch {
      return {};
    }
  }

  const numberToTimeSlot: Record<number, string> = {
    0: 'morning',
    1: 'afternoon',
    2: 'evening',
  };

  const result: Record<string, string[]> = {};
  Object.keys(schedule || {}).forEach(day => {
    const slots = schedule[day];
    if (Array.isArray(slots) && slots.length > 0) {
      result[day] = typeof slots[0] === 'number'
        ? slots.map((num: number) => numberToTimeSlot[num]).filter(Boolean) as string[]
        : slots.filter((s: string) => ['morning', 'afternoon', 'evening'].includes(s));
    }
  });
  return result;
}

export async function createAppointment(input: CreateAppointmentInput): Promise<Appointment> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required. Please log in to book an appointment.");
  }

  if (!input.first_name || !input.last_name || !input.email) {
    throw new Error("First name, last name, and email are required");
  }

  if (!input.selected_slots || input.selected_slots.length === 0) {
    throw new Error("At least one time slot must be selected");
    }

  const validSlots = validateAndCleanSlots(input.selected_slots);
  if (validSlots.length === 0) {
    throw new Error("At least one valid time slot must be selected. Each slot must have both 'day' (0-6) and 'time_slot' (morning, afternoon, or evening).");
  }

  // Explicitly exclude legacy fields - API doesn't need preferred_dates or preferred_time_slots
  // We only use selected_slots format

  const truncate = (str: string, max: number) => String(str || '').trim().substring(0, max);
  
  const selectedSlotsForPayload = validSlots.map(slot => ({
    day: slot.day,
    time_slot: slot.time_slot,
  }));
  
  // Build payload with ONLY the fields the API requires/accepts
  // DO NOT include preferred_dates or preferred_time_slots - the API doesn't need them
  const payload: {
    first_name: string;
    last_name: string;
    email: string;
    selected_slots: Array<{ day: number; time_slot: string }>;
    phone?: string;
    reason?: string;
  } = {
    first_name: truncate(input.first_name, 100),
    last_name: truncate(input.last_name, 100),
    email: truncate(input.email, 100).toLowerCase(),
    selected_slots: selectedSlotsForPayload,
  };

  // Only add optional fields if they exist
  if (input.phone && input.phone.length > 0) {
    payload.phone = truncate(input.phone, 100);
  }
  if (input.reason && input.reason.length > 0) {
    payload.reason = truncate(input.reason, 100);
  }

  const requestBody = JSON.stringify(payload);

  const response = await fetch(API_ENDPOINTS.meetings.createAppointment, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
    body: requestBody,
  });
  
  const data = await parseResponse(response);

  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  // Build clean response - explicitly exclude preferred_dates and preferred_time_slots
  // Backend may return these legacy fields, but we only use selected_slots format (per API spec)
  const rawResponse: any = data.appointment || data.data || data;
  
  // Build appointment object from scratch with ONLY the fields we want
  // Explicitly DO NOT include preferred_dates, preferred_time_slots, or their display variants
  const appointmentResponse: any = {
    id: data.appointment_id || rawResponse.id || '',
    first_name: rawResponse.first_name || input.first_name.trim(),
    last_name: rawResponse.last_name || input.last_name.trim(),
    email: rawResponse.email || input.email.trim().toLowerCase(),
    phone: rawResponse.phone || input.phone?.trim(),
    reason: rawResponse.reason || input.reason?.trim(),
    // Use selected_slots from our original input (preserve the format we sent - per API spec)
    selected_slots: validSlots,
    status: rawResponse.status || "pending_review",
    created_at: rawResponse.created_at || new Date().toISOString(),
    updated_at: rawResponse.updated_at || new Date().toISOString(),
    // Include other useful fields from response
    ...(rawResponse.jitsi_meet_url && { jitsi_meet_url: rawResponse.jitsi_meet_url }),
    ...(rawResponse.jitsi_room_id && { jitsi_room_id: rawResponse.jitsi_room_id }),
    ...(rawResponse.matching_availability && { matching_availability: rawResponse.matching_availability }),
    ...(rawResponse.are_preferences_available !== undefined && { are_preferences_available: rawResponse.are_preferences_available }),
    ...(rawResponse.available_slots_info && { available_slots_info: rawResponse.available_slots_info }),
    // Explicitly EXCLUDED: preferred_dates, preferred_time_slots, preferred_dates_display, preferred_time_slots_display
  };

  // Explicitly delete preferred_dates and preferred_time_slots from response object
  // These are backend legacy fields - we only use selected_slots format
  if ('preferred_dates' in appointmentResponse) {
    delete appointmentResponse.preferred_dates;
  }
  if ('preferred_time_slots' in appointmentResponse) {
    delete appointmentResponse.preferred_time_slots;
  }
  if ('preferred_dates_display' in appointmentResponse) {
    delete appointmentResponse.preferred_dates_display;
  }
  if ('preferred_time_slots_display' in appointmentResponse) {
    delete appointmentResponse.preferred_time_slots_display;
  }

  return appointmentResponse;
}

export async function getAvailableDates(): Promise<AvailableDatesResponse> {
  try {
  const response = await fetch(API_ENDPOINTS.meetings.availableDates, {
      method: "GET",
      headers: { "Content-Type": "application/json" },
    });

    if (!response.ok) {
      return { dates: [] };
    }

    const data = await parseResponse(response);
    return Array.isArray(data) ? { dates: data } : data;
  } catch {
    return { dates: [] };
  }
}

export async function getWeeklyAvailability(): Promise<WeeklyAvailabilityResponse> {
  const response = await fetch(API_ENDPOINTS.meetings.weeklyAvailability, {
    method: "GET",
    headers: { "Content-Type": "application/json" },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
      }

  return Array.isArray(data) ? data : data;
}

export async function getAvailabilityConfig(): Promise<AvailabilityConfig> {
  const response = await fetch(API_ENDPOINTS.meetings.availabilityConfig, {
    method: "GET",
    headers: { "Content-Type": "application/json" },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return data;
}

export async function checkDateAvailability(date: string): Promise<CheckDateAvailabilityResponse> {
  const response = await fetch(API_ENDPOINTS.meetings.checkDateAvailability, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ date }),
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
}

  return data;
}

export async function getAvailabilityOverview(): Promise<AvailabilityOverview> {
  const response = await fetch(API_ENDPOINTS.meetings.availabilityOverview, {
    method: "GET",
    headers: { "Content-Type": "application/json" },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }
  
  return data;
}

export async function listAppointments(email?: string): Promise<Appointment[]> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const url = email 
    ? `${API_ENDPOINTS.meetings.listAppointments}?email=${encodeURIComponent(email)}`
    : API_ENDPOINTS.meetings.listAppointments;

  const response = await fetch(url, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  if (Array.isArray(data)) return data;
  if (data?.appointments && Array.isArray(data.appointments)) return data.appointments;
  if (data?.results && Array.isArray(data.results)) return data.results;
  if (data?.id || data?.first_name) return [data];
  return [];
}

export async function getUserAppointments(): Promise<Appointment[]> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(API_ENDPOINTS.meetings.userAppointments, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  if (Array.isArray(data)) return data;
  if (data?.appointments && Array.isArray(data.appointments)) return data.appointments;
  if (data?.results && Array.isArray(data.results)) return data.results;
  return [];
}

export async function getAppointmentDetail(id: string): Promise<Appointment> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(`${API_ENDPOINTS.meetings.listAppointments}${id}/`, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return (data as AppointmentResponse).appointment || data;
}

export async function scheduleAppointment(id: string, input: ScheduleAppointmentInput): Promise<Appointment> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(`${API_ENDPOINTS.meetings.listAppointments}${id}/schedule/`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
    body: JSON.stringify(input),
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return data.appointment || data;
  }

export async function rejectAppointment(id: string, input: RejectAppointmentInput): Promise<Appointment> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(`${API_ENDPOINTS.meetings.listAppointments}${id}/reject/`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
    body: JSON.stringify(input),
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return (data as AppointmentResponse).appointment || data;
}

export async function getPublicAvailability(): Promise<AdminAvailability | null> {
  try {
    const weeklyAvailability = await getWeeklyAvailability();
    const weekArray = Array.isArray(weeklyAvailability) 
      ? weeklyAvailability 
      : (weeklyAvailability as any).week || [];

    if (!weekArray || weekArray.length === 0) {
      return null;
    }

    const availabilitySchedule: Record<string, string[]> = {};
    const availableDays: number[] = [];
    const availableDaysDisplay: string[] = [];

    weekArray.forEach((day: any) => {
      if (day.is_available && day.available_slots?.length > 0) {
        availabilitySchedule[day.day.toString()] = day.available_slots;
        availableDays.push(day.day);
        availableDaysDisplay.push(day.day_name);
    }
    });

    return {
      available_days: availableDays,
      available_days_display: availableDaysDisplay,
      availability_schedule: availabilitySchedule,
      all_available_slots: weekArray
        .filter((d: any) => d.is_available)
        .flatMap((d: any) => 
          d.available_slots.map((slot: string) => ({ 
            day: d.day, 
            time_slot: slot as "morning" | "afternoon" | "evening" 
          }))
        ),
    } as AdminAvailability;
  } catch {
    return null;
  }
}

export async function getAdminAvailability(): Promise<AdminAvailability> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(API_ENDPOINTS.meetings.adminAvailability, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  if (data.availability_schedule) {
    const availabilitySchedule = normalizeAvailabilitySchedule(data.availability_schedule);
    const availableDays = Object.keys(availabilitySchedule).map(Number);
    const dayNames = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];
    const availableDaysDisplay = availableDays.map(day => dayNames[day] || `Day ${day}`);

    return {
      available_days: availableDays,
      available_days_display: Array.isArray(data.availability_schedule_display) 
        ? data.availability_schedule_display 
        : data.availability_schedule_display 
        ? [data.availability_schedule_display]
        : availableDaysDisplay,
      availability_schedule: availabilitySchedule,
      availability_schedule_display: data.availability_schedule_display,
      all_available_slots: data.all_available_slots || [],
    } as AdminAvailability;
  }

  let availableDays: number[] = [];
  if (typeof data.available_days === 'string') {
    try {
      availableDays = JSON.parse(data.available_days);
    } catch {
      availableDays = data.available_days.split(',').map((d: string) => parseInt(d.trim())).filter((d: number) => !isNaN(d));
    }
  } else if (Array.isArray(data.available_days)) {
    availableDays = data.available_days;
  }

  return {
    available_days: availableDays,
    available_days_display: data.available_days_display || [],
  } as AdminAvailability;
}

export async function updateAdminAvailability(input: UpdateAvailabilityInput): Promise<AdminAvailability> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  if (!input.availability_schedule) {
    throw new Error("availability_schedule is required");
  }

  const cleanedSchedule: Record<string, string[]> = {};
  Object.keys(input.availability_schedule).forEach(key => {
    const dayNum = parseInt(key);
    if (isNaN(dayNum) || dayNum < 0 || dayNum > 6) return;
    
    const slots = input.availability_schedule[key];
    if (Array.isArray(slots) && slots.length > 0) {
      const validSlots = slots
        .filter((slot: string) => typeof slot === 'string' && ['morning', 'afternoon', 'evening'].includes(slot))
        .filter((slot: string, index: number, self: string[]) => self.indexOf(slot) === index);
      
      if (validSlots.length > 0) {
        cleanedSchedule[key.toString()] = validSlots;
      }
    }
  });

  if (Object.keys(cleanedSchedule).length === 0) {
    throw new Error("At least one day with valid time slots must be provided");
  }

  const sortedSchedule: Record<string, string[]> = {};
  Object.keys(cleanedSchedule)
    .sort((a, b) => parseInt(a) - parseInt(b))
    .forEach(key => {
      sortedSchedule[key] = cleanedSchedule[key];
    });

  let response = await fetch(API_ENDPOINTS.meetings.adminAvailability, {
    method: "PUT",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
    body: JSON.stringify({ availability_schedule: sortedSchedule }),
  });

  if (!response.ok && response.status === 500) {
    response = await fetch(API_ENDPOINTS.meetings.adminAvailability, {
      method: "PATCH",
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${tokens.access}`,
      },
      body: JSON.stringify({ availability_schedule: sortedSchedule }),
  });
  }

  const responseText = await response.text();
  const contentType = response.headers.get("content-type") || "";

  if (!responseText || responseText.trim().length === 0) {
    if (response.ok) {
      return await getAdminAvailability();
    }
    throw new Error(`Server error (${response.status}): ${response.statusText || 'Empty response'}`);
  }

  let data: any;
  if (contentType.includes("application/json")) {
  try {
      data = JSON.parse(responseText);
    } catch {
      throw new Error(`Server error (${response.status}): Invalid JSON format`);
    }
  } else {
    const htmlError = extractHtmlError(responseText);
    throw new Error(`Server error (${response.status}): ${htmlError || response.statusText || 'Internal Server Error'}`);
  }

  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  if (data?.availability_schedule) {
    const availabilitySchedule = normalizeAvailabilitySchedule(data.availability_schedule);
    const availableDays = Object.keys(availabilitySchedule).map(Number);
    const dayNames = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];
    const availableDaysDisplay = availableDays.map(day => dayNames[day] || `Day ${day}`);

    return {
      available_days: availableDays,
      available_days_display: Array.isArray(data.availability_schedule_display)
        ? data.availability_schedule_display
        : data.availability_schedule_display
        ? [data.availability_schedule_display]
        : availableDaysDisplay,
      availability_schedule: availabilitySchedule,
      availability_schedule_display: data.availability_schedule_display,
      all_available_slots: data.all_available_slots || [],
    } as AdminAvailability;
  }

  if (response.ok && (!data || Object.keys(data).length === 0)) {
    return await getAdminAvailability();
  }

  let availableDays: number[] = [];
  if (typeof data.available_days === 'string') {
    try {
      availableDays = JSON.parse(data.available_days);
    } catch {
      availableDays = data.available_days.split(',').map((d: string) => parseInt(d.trim())).filter((d: number) => !isNaN(d));
    }
  } else if (Array.isArray(data.available_days)) {
    availableDays = data.available_days;
  }

  return {
    available_days: availableDays,
    available_days_display: data.available_days_display || [],
  } as AdminAvailability;
}

export async function getAppointmentStats(): Promise<AppointmentStats> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(`${API_ENDPOINTS.meetings.listAppointments}stats/`, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return data;
}

export async function getUserAppointmentStats(): Promise<UserAppointmentStats> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(API_ENDPOINTS.meetings.userAppointmentStats, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return data;
}

export async function getJitsiMeetingInfo(id: string): Promise<JitsiMeetingInfo> {
  const tokens = getStoredTokens();
  if (!tokens.access) {
    throw new Error("Authentication required.");
  }

  const response = await fetch(`${API_ENDPOINTS.meetings.listAppointments}${id}/jitsi-meeting/`, {
    method: "GET",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${tokens.access}`,
    },
  });

  const data = await parseResponse(response);
  if (!response.ok) {
    throw new Error(extractErrorMessage(data as unknown as ApiError));
  }

  return data;
}