/**
 * API аналитики ментора (отдельная страница, не профиль).
 * Период по умолчанию на странице аналитики — последние 30 дней.
 */

import apiClient from '@/lib/api-client';

export type AnalyticsPeriod = 'day' | 'week' | 'month' | 'year' | 'custom';

export interface AnalyticsDateRange {
  period: AnalyticsPeriod;
  start_date: string; // YYYY-MM-DD
  end_date: string;
}

export interface AnalyticsOverview {
  period: { start: string; end: string };
  lessons: { total: number; completed: number; cancelled: number };
  revenue: { total: number; average_per_lesson: number };
  students: { active: number };
  homeworks: { total: number; pending: number };
  grades: { average: number };
}

export interface StudentStat {
  id: number;
  name: string;
  email: string;
  lessons_total: number;
  lessons_completed: number;
  average_grade: number;
  revenue: number;
}

export interface AnalyticsStudentsResponse {
  students: StudentStat[];
  total_count: number;
}

export interface AnalyticsRevenueResponse {
  total_revenue: number;
  by_day: { date: string; revenue: number; lessons_count: number }[];
  by_subject: { subject: string; revenue: number; lessons_count: number }[];
}

export interface AnalyticsLessonsStatsResponse {
  by_status: { status: string; count: number }[];
  by_subject: { subject: string; count: number }[];
  by_weekday: { day: string; count: number }[];
}

/** Средняя оценка по дням (успех учеников / продуктивность репетитора) */
export interface AnalyticsGradesByDayResponse {
  period: { start: string; end: string };
  by_day: {
    date: string;
    average_grade: number | null;
    lessons_count: number;
    graded_count: number;
  }[];
  summary: {
    total_lessons: number;
    graded_lessons: number;
    average_grade: number;
  };
}

/** Последние 30 дней (по умолчанию на странице аналитики). */
export function getLast30DaysRange(): { start_date: string; end_date: string } {
  const now = new Date();
  const end = new Date(now);
  const start = new Date(now);
  start.setDate(start.getDate() - 29); // 30 дней включительно: сегодня минус 29
  const fmt = (d: Date) => d.toISOString().slice(0, 10);
  return { start_date: fmt(start), end_date: fmt(end) };
}

export function getCurrentWeekRange(): { start_date: string; end_date: string } {
  const now = new Date();
  const day = now.getDay();
  const diff = day === 0 ? -6 : 1 - day; // понедельник
  const monday = new Date(now);
  monday.setDate(now.getDate() + diff);
  const sunday = new Date(monday);
  sunday.setDate(monday.getDate() + 6);
  const fmt = (d: Date) => d.toISOString().slice(0, 10);
  return { start_date: fmt(monday), end_date: fmt(sunday) };
}

function getWeekRange(): { start: string; end: string } {
  const r = getCurrentWeekRange();
  return { start: r.start_date, end: r.end_date };
}

export function getDefaultDateRange(): AnalyticsDateRange {
  const { start, end } = getWeekRange();
  return { period: 'week', start_date: start, end_date: end };
}

/** Преобразовать диапазон дат в AnalyticsDateRange для API (всегда custom) */
export function toAnalyticsRange(r: { start_date: string; end_date: string }): AnalyticsDateRange {
  return { period: 'custom', start_date: r.start_date, end_date: r.end_date };
}

function buildParams(range: AnalyticsDateRange): string {
  const p = new URLSearchParams();
  p.set('period', range.period === 'custom' ? 'custom' : range.period);
  p.set('start_date', range.start_date);
  p.set('end_date', range.end_date);
  return p.toString();
}

export async function getAnalyticsOverview(range: AnalyticsDateRange): Promise<AnalyticsOverview> {
  const q = buildParams(range);
  const url = q ? `/analytics/overview?${q}` : '/analytics/overview';
  const res = await apiClient.get<AnalyticsOverview>(url);
  return res.data;
}

export async function getAnalyticsStudents(range: AnalyticsDateRange): Promise<AnalyticsStudentsResponse> {
  const q = buildParams(range);
  const url = q ? `/analytics/students?${q}` : '/analytics/students';
  const res = await apiClient.get<AnalyticsStudentsResponse>(url);
  return res.data;
}

export async function getAnalyticsRevenue(range: AnalyticsDateRange): Promise<AnalyticsRevenueResponse> {
  const q = buildParams(range);
  const url = q ? `/analytics/revenue?${q}` : '/analytics/revenue';
  const res = await apiClient.get<AnalyticsRevenueResponse>(url);
  return res.data;
}

export async function getAnalyticsLessonsStats(range: AnalyticsDateRange): Promise<AnalyticsLessonsStatsResponse> {
  const q = buildParams(range);
  const url = q ? `/analytics/lessons_stats?${q}` : '/analytics/lessons_stats';
  const res = await apiClient.get<AnalyticsLessonsStatsResponse>(url);
  return res.data;
}

export async function getAnalyticsGradesByDay(range: AnalyticsDateRange): Promise<AnalyticsGradesByDayResponse> {
  const q = buildParams(range);
  const url = q ? `/analytics/grades_by_day?${q}` : '/analytics/grades_by_day';
  const res = await apiClient.get<AnalyticsGradesByDayResponse>(url);
  return res.data;
}