import React, { useState, useEffect } from "react";
import { View, Text, StyleSheet, TouchableOpacity } from "react-native";
import { LinearGradient } from "expo-linear-gradient";
import { Ionicons } from "@expo/vector-icons";
import { theme } from "../styles/theme";

interface AttendanceRecord {
  id: string;
  checkInTime: string;
  checkOutTime?: string | null;
  duration?: number | null;
}

interface AttendanceCalendarProps {
  attendanceRecords: AttendanceRecord[];
}

export function AttendanceCalendar({
  attendanceRecords,
}: AttendanceCalendarProps) {
  const [currentMonth, setCurrentMonth] = useState(new Date());
  const [calendarDays, setCalendarDays] = useState<
    Array<{ date: Date | null; hasAttendance: boolean; isToday: boolean }>
  >([]);

  useEffect(() => {
    generateCalendar(currentMonth);
  }, [currentMonth, attendanceRecords]);

  const generateCalendar = (month: Date) => {
    const year = month.getFullYear();
    const monthIndex = month.getMonth();

    // Get first day of month and number of days
    const firstDay = new Date(year, monthIndex, 1);
    const lastDay = new Date(year, monthIndex + 1, 0);
    const daysInMonth = lastDay.getDate();
    const startingDayOfWeek = firstDay.getDay();

    // Create attendance lookup set
    const attendanceDates = new Set(
      attendanceRecords.map((record) =>
        new Date(record.checkInTime).toDateString(),
      ),
    );

    const today = new Date().toDateString();

    // Build calendar array
    const days: Array<{
      date: Date | null;
      hasAttendance: boolean;
      isToday: boolean;
    }> = [];

    // Add empty cells for days before month starts
    for (let i = 0; i < startingDayOfWeek; i++) {
      days.push({ date: null, hasAttendance: false, isToday: false });
    }

    // Add days of the month
    for (let day = 1; day <= daysInMonth; day++) {
      const date = new Date(year, monthIndex, day);
      const dateString = date.toDateString();
      days.push({
        date,
        hasAttendance: attendanceDates.has(dateString),
        isToday: dateString === today,
      });
    }

    setCalendarDays(days);
  };

  const goToPreviousMonth = () => {
    setCurrentMonth(
      new Date(currentMonth.getFullYear(), currentMonth.getMonth() - 1),
    );
  };

  const goToNextMonth = () => {
    setCurrentMonth(
      new Date(currentMonth.getFullYear(), currentMonth.getMonth() + 1),
    );
  };

  const monthName = currentMonth.toLocaleDateString("en-US", {
    month: "long",
    year: "numeric",
  });

  return (
    <View style={styles.container}>
      <LinearGradient
        colors={[theme.colors.white, theme.colors.gray50]}
        style={[styles.card, theme.shadows.medium]}
      >
        {/* Header */}
        <View style={styles.header}>
          <Text style={styles.title}>Attendance Calendar</Text>
        </View>

        {/* Month Navigation */}
        <View style={styles.monthNav}>
          <TouchableOpacity
            onPress={goToPreviousMonth}
            style={styles.navButton}
          >
            <Ionicons
              name="chevron-back"
              size={20}
              color={theme.colors.primary}
            />
          </TouchableOpacity>
          <Text style={styles.monthText}>{monthName}</Text>
          <TouchableOpacity onPress={goToNextMonth} style={styles.navButton}>
            <Ionicons
              name="chevron-forward"
              size={20}
              color={theme.colors.primary}
            />
          </TouchableOpacity>
        </View>

        {/* Day Headers */}
        <View style={styles.dayHeaders}>
          {["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"].map((day) => (
            <Text key={day} style={styles.dayHeader}>
              {day}
            </Text>
          ))}
        </View>

        {/* Calendar Grid */}
        <View style={styles.calendarGrid}>
          {calendarDays.map((day, index) => (
            <View key={index} style={styles.dayCell}>
              {day.date ? (
                <View
                  style={[
                    styles.dayContent,
                    day.isToday && styles.todayContent,
                    day.hasAttendance && styles.attendanceContent,
                  ]}
                >
                  <Text
                    style={[
                      styles.dayText,
                      day.isToday && styles.todayText,
                      day.hasAttendance && styles.attendanceText,
                    ]}
                  >
                    {day.date.getDate()}
                  </Text>
                  {day.hasAttendance && <View style={styles.attendanceDot} />}
                </View>
              ) : (
                <View style={styles.emptyCell} />
              )}
            </View>
          ))}
        </View>

        {/* Legend */}
        <View style={styles.legend}>
          <View style={styles.legendItem}>
            <View style={styles.legendDotAttendance} />
            <Text style={styles.legendText}>Attended</Text>
          </View>
          <View style={styles.legendItem}>
            <View style={styles.legendDotToday} />
            <Text style={styles.legendText}>Today</Text>
          </View>
        </View>
      </LinearGradient>
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    paddingHorizontal: 20,
    marginBottom: 20,
  },
  card: {
    borderRadius: theme.borderRadius["2xl"],
    padding: 20,
  },
  header: {
    marginBottom: 16,
  },
  title: {
    fontSize: theme.typography.fontSize.xl,
    fontWeight: theme.typography.fontWeight.bold,
    color: theme.colors.gray800,
  },
  monthNav: {
    flexDirection: "row",
    justifyContent: "space-between",
    alignItems: "center",
    marginBottom: 16,
    paddingHorizontal: 8,
  },
  navButton: {
    padding: 8,
  },
  monthText: {
    fontSize: theme.typography.fontSize.lg,
    fontWeight: theme.typography.fontWeight.semibold,
    color: theme.colors.gray700,
  },
  dayHeaders: {
    flexDirection: "row",
    marginBottom: 8,
  },
  dayHeader: {
    flex: 1,
    textAlign: "center",
    fontSize: theme.typography.fontSize.xs,
    fontWeight: theme.typography.fontWeight.semibold,
    color: theme.colors.gray500,
  },
  calendarGrid: {
    flexDirection: "row",
    flexWrap: "wrap",
  },
  dayCell: {
    width: `${100 / 7}%`,
    aspectRatio: 1,
    padding: 2,
  },
  dayContent: {
    flex: 1,
    justifyContent: "center",
    alignItems: "center",
    borderRadius: theme.borderRadius.md,
    position: "relative",
  },
  todayContent: {
    backgroundColor: theme.colors.primaryLight,
    borderWidth: 1,
    borderColor: theme.colors.primary,
  },
  attendanceContent: {
    backgroundColor: theme.colors.successLight,
  },
  emptyCell: {
    flex: 1,
  },
  dayText: {
    fontSize: theme.typography.fontSize.sm,
    color: theme.colors.gray700,
    fontWeight: theme.typography.fontWeight.medium,
  },
  todayText: {
    color: theme.colors.white,
    fontWeight: theme.typography.fontWeight.bold,
  },
  attendanceText: {
    color: theme.colors.white,
    fontWeight: theme.typography.fontWeight.bold,
  },
  attendanceDot: {
    position: "absolute",
    bottom: 2,
    width: 4,
    height: 4,
    borderRadius: 2,
    backgroundColor: theme.colors.white,
  },
  legend: {
    flexDirection: "row",
    justifyContent: "center",
    gap: 20,
    marginTop: 16,
    paddingTop: 16,
    borderTopWidth: 1,
    borderTopColor: theme.colors.gray200,
  },
  legendItem: {
    flexDirection: "row",
    alignItems: "center",
    gap: 6,
  },
  legendDotAttendance: {
    width: 12,
    height: 12,
    borderRadius: 6,
    backgroundColor: theme.colors.successLight,
  },
  legendDotToday: {
    width: 12,
    height: 12,
    borderRadius: 6,
    backgroundColor: theme.colors.primaryLight,
    borderWidth: 1,
    borderColor: theme.colors.primary,
  },
  legendText: {
    fontSize: theme.typography.fontSize.xs,
    color: theme.colors.gray600,
  },
});