import * as Calendar from "expo-calendar";
import * as SQLite from "expo-sqlite";
import React, { useEffect, useState } from "react";
import {
  FlatList,
  SafeAreaView,
  StyleSheet,
  Text,
  TouchableOpacity,
  View,
} from "react-native";

export interface EventItem {
  id: string;
  title: string;
  startDate: string;
  endDate: string;
}

const db = SQLite.openDatabaseSync("events.db");

export default function CalendarTab() {
  const [source, setSource] = useState<"sqlite" | "iphone">("sqlite");
  const [events, setEvents] = useState<EventItem[]>([]);
  const [loading, setLoading] = useState(false);
  const [selectedYear, setSelectedYear] = useState<number>(
    new Date().getFullYear()
  );
  const [permissionError, setPermissionError] = useState<string | null>(null);
  const [calendarType, setCalendarType] = useState<"calendar" | "reminder">(
    "calendar"
  );

  useEffect(() => {
    if (source === "sqlite") {
      loadEventsFromDB();
    } else {
      loadEventsFromDevice();
    }
  }, [source, selectedYear, calendarType]);

  const loadEventsFromDB = async () => {
    setLoading(true);
    try {
      const stmt = await db.prepareAsync("SELECT * FROM events;");
      const loadedEvents: EventItem[] = [];
      const result = await stmt.executeAsync([]);
      for await (const row of result) {
        loadedEvents.push(row as EventItem);
      }
      setEvents(loadedEvents);
      await stmt.finalizeAsync();
    } catch (e) {
      setEvents([]);
    } finally {
      setLoading(false);
    }
  };

  const loadEventsFromDevice = async () => {
    setLoading(true);
    setPermissionError(null);
    try {
      let perm;
      if (calendarType === "reminder") {
        perm = await Calendar.requestRemindersPermissionsAsync();
      } else {
        perm = await Calendar.requestCalendarPermissionsAsync();
      }
      if (!perm.granted) {
        setEvents([]);
        setPermissionError(
          `Keine Berechtigung für ${
            calendarType === "reminder" ? "Erinnerungen" : "Kalender"
          }-Zugriff. Bitte in den iOS-Einstellungen aktivieren.`
        );
        return;
      }
      let calendars = await Calendar.getCalendarsAsync();
      console.log(
        "Gefundene Kalender:",
        calendars.map((c) => ({ id: c.id, title: c.title, type: c.type }))
      );
      if (calendarType === "calendar") {
        calendars = calendars.filter((c) => String(c.type) === "calendar");
      } else {
        calendars = calendars.filter((c) => String(c.type) === "reminder");
      }
      const start = new Date(selectedYear, 0, 1);
      const end = new Date(selectedYear, 11, 31, 23, 59, 59);
      let allEvents: EventItem[] = [];
      for (const cal of calendars) {
        const calEvents = await Calendar.getEventsAsync([cal.id], start, end);
        console.log(
          `Events für Kalender ${cal.title}:`,
          calEvents.map((e) => ({
            id: e.id,
            title: e.title,
            start: e.startDate,
            end: e.endDate,
          }))
        );
        allEvents = allEvents.concat(
          calEvents.map((e) => ({
            id: e.id,
            title: e.title || "(Kein Titel)",
            startDate:
              typeof e.startDate === "string"
                ? e.startDate
                : new Date(e.startDate).toISOString(),
            endDate:
              typeof e.endDate === "string"
                ? e.endDate
                : new Date(e.endDate).toISOString(),
          }))
        );
      }
      setEvents(allEvents);
    } catch (e: any) {
      setEvents([]);
      setPermissionError(
        "Fehler beim Zugriff auf " +
          (calendarType === "reminder" ? "Erinnerungen" : "Kalender") +
          ": " +
          (e?.message || JSON.stringify(e))
      );
    } finally {
      setLoading(false);
    }
  };

  const renderItem = ({ item }: { item: EventItem }) => (
    <View style={styles.item}>
      <Text style={styles.title}>{item.title}</Text>
      <Text style={styles.time}>
        {new Date(item.startDate).toLocaleString()} -{" "}
        {new Date(item.endDate).toLocaleString()}
      </Text>
    </View>
  );

  return (
    <SafeAreaView style={styles.container}>
      <View style={styles.switchRow}>
        <TouchableOpacity
          style={[
            styles.switchButton,
            source === "sqlite" && styles.activeButton,
          ]}
          onPress={() => setSource("sqlite")}
        >
          <Text style={styles.switchText}>SQLite</Text>
        </TouchableOpacity>
        <TouchableOpacity
          style={[
            styles.switchButton,
            source === "iphone" && styles.activeButton,
          ]}
          onPress={() => setSource("iphone")}
        >
          <Text style={styles.switchText}>
            iPhone ({calendarType === "calendar" ? "Kalender" : "Erinnerungen"})
          </Text>
        </TouchableOpacity>
      </View>
      {source === "iphone" && (
        <View style={styles.switchRow}>
          <TouchableOpacity
            style={[
              styles.switchButton,
              calendarType === "calendar" && styles.activeButton,
            ]}
            onPress={() => setCalendarType("calendar")}
          >
            <Text style={styles.switchText}>Kalender</Text>
          </TouchableOpacity>
          <TouchableOpacity
            style={[
              styles.switchButton,
              calendarType === "reminder" && styles.activeButton,
            ]}
            onPress={() => setCalendarType("reminder")}
          >
            <Text style={styles.switchText}>Erinnerungen</Text>
          </TouchableOpacity>
        </View>
      )}
      <Text style={styles.header}>Kalender Events ({selectedYear})</Text>
      <FlatList
        data={events}
        keyExtractor={(item) => item.id}
        renderItem={renderItem}
        ListEmptyComponent={
          permissionError ? (
            <Text style={{ textAlign: "center", color: "red" }}>
              {permissionError}
            </Text>
          ) : (
            <Text style={{ textAlign: "center" }}>Keine Events gefunden.</Text>
          )
        }
        refreshing={loading}
        onRefresh={
          source === "sqlite" ? loadEventsFromDB : loadEventsFromDevice
        }
      />
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: { flex: 1, backgroundColor: "#fff", padding: 10 },
  header: {
    fontSize: 20,
    fontWeight: "bold",
    marginBottom: 16,
    textAlign: "center",
  },
  item: {
    marginBottom: 12,
    padding: 12,
    borderRadius: 8,
    backgroundColor: "#f2f2f2",
  },
  title: { fontSize: 16, fontWeight: "600" },
  time: { fontSize: 14, color: "#555" },
  switchRow: {
    flexDirection: "row",
    justifyContent: "center",
    marginBottom: 16,
  },
  switchButton: {
    padding: 10,
    borderRadius: 8,
    backgroundColor: "#eee",
    marginHorizontal: 8,
  },
  activeButton: { backgroundColor: "#007AFF" },
  switchText: { color: "#333", fontWeight: "bold" },
});