import { useMemo } from 'react'
import dayjs from 'dayjs'
import { AttendanceData } from './useAttendanceData'

export interface AttendanceStats {
  totalLessons: number
  averageAttendance: number
  topStudents: Array<{
    name: string
    attendance: number
    attendancePercent: number
  }>
  lessonsAttendance: Array<{
    name: string
    date: string
    attendancePercent: number
  }>
}

export const useAttendanceStats = (data: AttendanceData): AttendanceStats => {
  return useMemo(() => {
    if (!data.attendance || !data.students.length) {
      return {
        totalLessons: 0,
        averageAttendance: 0,
        topStudents: [],
        lessonsAttendance: []
      }
    }

    const now = dayjs()
    // Фильтруем лекции, оставляя только те, которые уже прошли (исключаем будущие)
    const pastLessons = data.attendance.filter(lesson => dayjs(lesson.date).isBefore(now))
    
    const totalLessons = pastLessons.length
    
    // Рассчитываем посещаемость для каждого студента
    const studentAttendance = data.students.map(student => {
      let attended = 0
      
      pastLessons.forEach(lesson => {
        if (lesson.students.some(s => s.sub === student.sub)) {
          attended++
        }
      })
      
      return {
        student,
        name: student.value,
        attendance: attended,
        attendancePercent: totalLessons > 0 ? (attended / totalLessons) * 100 : 0
      }
    })
    
    // Рассчитываем статистику посещаемости для каждого урока
    const lessonsAttendance = pastLessons.map(lesson => {
      const attendedStudents = lesson.students.length
      const attendancePercent = data.students.length > 0 
        ? (attendedStudents / data.students.length) * 100 
        : 0
        
      return {
        name: lesson.name,
        date: lesson.date,
        attendancePercent
      }
    })
    
    // Выбираем топ-3 студентов по посещаемости
    const topStudents = [...studentAttendance]
      .sort((a, b) => b.attendance - a.attendance)
      .slice(0, 3)
      .map(student => ({
        name: student.name,
        attendance: student.attendance,
        attendancePercent: student.attendancePercent
      }))
    
    // Считаем среднюю посещаемость
    const totalAttendance = studentAttendance.reduce((sum, student) => sum + student.attendance, 0)
    const averageAttendance = data.students.length > 0 && totalLessons > 0
      ? (totalAttendance / (data.students.length * totalLessons)) * 100
      : 0
      
    return {
      totalLessons,
      averageAttendance,
      topStudents,
      lessonsAttendance
    }
  }, [data])
}