import { useEffect, useMemo, useState } from 'react';
import {
  ActivityIndicator,
  FlatList,
  KeyboardAvoidingView,
  Platform,
  StyleSheet,
  TextInput,
  View,
} from 'react-native';
import { Image } from 'expo-image';
import * as ImageManipulator from 'expo-image-manipulator';
import * as ImagePicker from 'expo-image-picker';
import { Link } from 'expo-router';

import { ThemedText } from '@/components/themed-text';
import { ThemedView } from '@/components/themed-view';
import { Colors, Fonts } from '@/constants/theme';
import { ThemedButton } from '@/components/themed-button';
import { useTranslation } from '@/localization/i18n';
import { dbPromise, initCoreTables } from '@/services/db';
import { useColorScheme } from '@/hooks/use-color-scheme';

type TaskRow = {
  id: number;
  name: string;
  description: string | null;
  entry_id: number | null;
  status: string | null;
  notes: string | null;
  meta_json: string | null;
};

export default function DailyTasksScreen() {
  const { t } = useTranslation();
  const theme = useColorScheme() ?? 'light';
  const palette = Colors[theme];
  const defaultTasks = [
    {
      name: t('tasks.default.fieldCheck'),
      description: t('tasks.default.fieldCheckDesc'),
      default_time: '08:00',
    },
    {
      name: t('tasks.default.scouting'),
      description: t('tasks.default.scoutingDesc'),
      default_time: '10:00',
    },
    {
      name: t('tasks.default.sensors'),
      description: t('tasks.default.sensorsDesc'),
      default_time: '15:00',
    },
  ];
  const pageSize = 10;
  const [tasks, setTasks] = useState<TaskRow[]>([]);
  const [status, setStatus] = useState(t('tasks.loading'));
  const [notesByTaskId, setNotesByTaskId] = useState<Record<number, string>>({});
  const [photoByTaskId, setPhotoByTaskId] = useState<Record<number, string>>({});
  const [page, setPage] = useState(1);
  const [hasMore, setHasMore] = useState(true);
  const [loadingMore, setLoadingMore] = useState(false);

  const todayKey = useMemo(() => new Date().toISOString().slice(0, 10), []);

  useEffect(() => {
    let isActive = true;

    async function loadTasks() {
      try {
        await initCoreTables();
        const db = await dbPromise;
        await ensureDefaultTasks(db, defaultTasks);
        await fetchTasksPage(1, true, isActive);
      } catch (error) {
        if (isActive) setStatus(`Error: ${String(error)}`);
      }
    }

    loadTasks();
    return () => {
      isActive = false;
    };
  }, [t, todayKey]);

  async function fetchTasksPage(pageToLoad: number, replace: boolean, isActive = true) {
    try {
      const db = await dbPromise;
      const rows = await db.getAllAsync<TaskRow>(
        `SELECT t.id, t.name, t.description,
                e.id as entry_id, e.status, e.notes, e.meta_json
         FROM daily_tasks t
         LEFT JOIN daily_task_entries e
           ON e.task_id = t.id
          AND substr(e.completed_at, 1, 10) = ?
         WHERE t.is_active = 1
         ORDER BY t.id ASC
         LIMIT ? OFFSET ?;`,
        todayKey,
        pageSize,
        (pageToLoad - 1) * pageSize
      );
      if (!isActive) return;
      setTasks((prev) => (replace ? rows : [...prev, ...rows]));
      setHasMore(rows.length === pageSize);
      setPage(pageToLoad);
      if (replace) {
        setStatus(rows.length === 0 ? t('tasks.empty') : '');
      }
      setNotesByTaskId((prev) => {
        const next = replace ? {} : { ...prev };
        rows.forEach((row) => {
          if (row.notes) next[row.id] = row.notes;
        });
        return next;
      });
      setPhotoByTaskId((prev) => {
        const next = replace ? {} : { ...prev };
        rows.forEach((row) => {
          const meta = parseTaskMeta(row.meta_json);
          if (meta.photoUri) next[row.id] = meta.photoUri;
        });
        return next;
      });
    } catch (error) {
      if (isActive) setStatus(`Error: ${String(error)}`);
    } finally {
      if (isActive) setLoadingMore(false);
    }
  }

  async function handleLoadMore() {
    if (loadingMore || !hasMore) return;
    setLoadingMore(true);
    const nextPage = page + 1;
    await fetchTasksPage(nextPage, false);
  }

  async function handleComplete(task: TaskRow) {
    try {
      const db = await dbPromise;
      const now = new Date().toISOString();
      const notes = (notesByTaskId[task.id] ?? '').trim();
      const metaJson = serializeTaskMeta({
        photoUri: photoByTaskId[task.id],
      });
      if (task.entry_id) {
        await db.runAsync('DELETE FROM daily_task_entries WHERE id = ?;', task.entry_id);
      } else {
        await db.runAsync(
          'INSERT INTO daily_task_entries (task_id, field_id, notes, status, completed_at, created_at, meta_json) VALUES (?, NULL, ?, ?, ?, ?, ?);',
          task.id,
          notes,
          'done',
          now,
          now,
          metaJson
        );
      }
      await fetchTasksPage(1, true);
    } catch (error) {
      setStatus(`Error: ${String(error)}`);
    }
  }

  async function handlePickPhoto(task: TaskRow) {
    const result = await ImagePicker.launchImageLibraryAsync({
      mediaTypes: getImageMediaTypes(),
      quality: 1,
    });
    if (result.canceled) return;
    const asset = result.assets[0];
    console.log('[Tasks] Picked photo:', asset.uri);
    const normalized = await normalizeImageUri(asset.uri);
    console.log('[Tasks] Normalized photo:', normalized);
    await persistTaskPhoto(task, normalized, setPhotoByTaskId);
  }

  async function handleTakePhoto(task: TaskRow) {
    try {
      const permission = await ImagePicker.requestCameraPermissionsAsync();
      if (!permission.granted) {
        setStatus(t('tasks.cameraDenied'));
        return;
      }
      const result = await ImagePicker.launchCameraAsync({
        quality: 1,
      });
      if (result.canceled) return;
      const asset = result.assets[0];
      console.log('[Tasks] Captured photo:', asset.uri);
      const normalized = await normalizeImageUri(asset.uri);
      console.log('[Tasks] Normalized photo:', normalized);
      await persistTaskPhoto(task, normalized, setPhotoByTaskId);
    } catch (error) {
      setStatus(t('tasks.cameraError'));
    }
  }

  return (
    <KeyboardAvoidingView
      behavior={Platform.OS === 'ios' ? 'padding' : undefined}
      keyboardVerticalOffset={Platform.OS === 'ios' ? 0 : 0}
      style={styles.keyboardAvoid}>
      <FlatList
        data={tasks}
        keyExtractor={(item) => String(item.id)}
        keyboardShouldPersistTaps="handled"
        keyboardDismissMode="on-drag"
        contentContainerStyle={styles.listContent}
        renderItem={({ item }) => {
        const isDone = Boolean(item.entry_id);
        return (
          <ThemedView
            style={[styles.card, { backgroundColor: palette.card, borderColor: palette.border }]}>
            <ThemedView style={styles.cardHeader}>
              <ThemedText type="subtitle" style={[styles.taskTitle, { color: palette.tint }]}>
                {item.name}
              </ThemedText>
              <ThemedText style={styles.badge}>
                {isDone ? t('tasks.done') : t('tasks.pending')}
              </ThemedText>
            </ThemedView>
            {item.description ? (
              <ThemedText style={styles.description}>{item.description}</ThemedText>
            ) : null}
            <ThemedText style={styles.photoLabel}>{t('tasks.photo')}</ThemedText>
            {photoByTaskId[item.id] ? (
              <Image
                source={{ uri: photoByTaskId[item.id] }}
                style={styles.photoPreview}
                contentFit="cover"
              />
            ) : null}
            <View style={styles.photoRow}>
              <ThemedButton
                title={t('tasks.pickPhoto')}
                onPress={() => handlePickPhoto(item)}
                variant="secondary"
              />
              <ThemedButton
                title={t('tasks.takePhoto')}
                onPress={() => handleTakePhoto(item)}
                variant="secondary"
              />
            </View>
            <TextInput
              value={notesByTaskId[item.id] ?? ''}
              onChangeText={(value) =>
                setNotesByTaskId((prev) => ({ ...prev, [item.id]: value }))
              }
              placeholder={t('tasks.notePlaceholder')}
              style={[
                styles.input,
                { borderColor: palette.border, backgroundColor: palette.input, color: palette.text },
              ]}
              multiline
            />
            <View style={styles.buttonRow}>
              <ThemedButton
                title={isDone ? t('tasks.undo') : t('tasks.complete')}
                onPress={() => handleComplete(item)}
              />
            </View>
          </ThemedView>
        );
      }}
        ItemSeparatorComponent={() => <View style={styles.separator} />}
        ListHeaderComponent={
        <View>
          <ThemedView style={styles.hero}>
            <Image source={require('@/assets/images/dailytask.jpg')} style={styles.heroImage} />
          </ThemedView>
          <ThemedView style={styles.titleContainer}>
            <ThemedText type="title" style={{ fontFamily: Fonts.rounded }}>
              {t('tasks.title')}
            </ThemedText>
            <ThemedText style={styles.subtitle}>{t('tasks.subtitle')}</ThemedText>
            <Link href="/task-history" push>
              <ThemedText type="link">{t('tasks.historyTitle')}</ThemedText>
            </Link>
          </ThemedView>

          {status ? (
            <ThemedView style={styles.section}>
              <ThemedText>{status}</ThemedText>
            </ThemedView>
          ) : null}
        </View>
      }
        onEndReached={handleLoadMore}
        onEndReachedThreshold={0.4}
        ListFooterComponent={
          <View style={styles.footer}>
            {loadingMore ? <ActivityIndicator /> : null}
          </View>
        }
      />
    </KeyboardAvoidingView>
  );
}

async function ensureDefaultTasks(
  db: Awaited<typeof dbPromise>,
  tasks: { name: string; description: string; default_time: string }[]
) {
  const row = await db.getFirstAsync<{ count: number }>(
    'SELECT COUNT(*) as count FROM daily_tasks;'
  );
  if (row?.count && row.count > 0) return;
  const now = new Date().toISOString();
  for (const task of tasks) {
    await db.runAsync(
      'INSERT INTO daily_tasks (name, description, default_time, is_active, created_at) VALUES (?, ?, ?, 1, ?);',
      task.name,
      task.description,
      task.default_time,
      now
    );
  }
}

async function persistTaskPhoto(
  task: TaskRow,
  uri: string,
  setPhotoByTaskId: (photos: Record<number, string>) => void
) {
  setPhotoByTaskId((prev) => ({ ...prev, [task.id]: uri }));
  if (!task.entry_id) return;
  const db = await dbPromise;
  const metaJson = serializeTaskMeta({ photoUri: uri });
  await db.runAsync(
    'UPDATE daily_task_entries SET meta_json = ? WHERE id = ?;',
    metaJson,
    task.entry_id
  );
}

function parseTaskMeta(raw: string | null) {
  if (!raw) return {} as { photoUri?: string };
  try {
    return JSON.parse(raw) as { photoUri?: string };
  } catch {
    return {} as { photoUri?: string };
  }
}

function serializeTaskMeta(meta: { photoUri?: string }) {
  if (!meta.photoUri) return null;
  return JSON.stringify(meta);
}

function getImageMediaTypes() {
  const mediaType = (ImagePicker as { MediaType?: { Image?: unknown; Images?: unknown } })
    .MediaType;
  return mediaType?.Image ?? mediaType?.Images ?? ['images'];
}

async function normalizeImageUri(uri: string) {
  try {
    const result = await ImageManipulator.manipulateAsync(
      uri,
      [],
      { compress: 1, format: ImageManipulator.SaveFormat.JPEG }
    );
    return result.uri;
  } catch {
    return uri;
  }
}

const styles = StyleSheet.create({
  hero: {
    backgroundColor: '#E8E6DA',
    aspectRatio: 16 / 9,
    width: '100%',
  },
  heroImage: {
    width: '100%',
    height: '100%',
  },
  titleContainer: {
    gap: 8,
    paddingHorizontal: 16,
    paddingVertical: 12,
  },
  subtitle: {
    opacity: 0.7,
  },
  section: {
    gap: 8,
    marginBottom: 16,
    paddingHorizontal: 16,
  },
  card: {
    borderRadius: 12,
    borderWidth: 1,
    borderColor: '#C6C6C6',
    padding: 12,
    marginHorizontal: 16,
    marginBottom: 12,
    gap: 8,
    backgroundColor: '#FFFFFF',
  },
  cardHeader: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    gap: 8,
  },
  description: {
    opacity: 0.8,
  },
  photoLabel: {
    opacity: 0.7,
  },
  photoPreview: {
    height: 160,
    width: '100%',
    borderRadius: 12,
  },
  photoRow: {
    flexDirection: 'row',
    gap: 8,
  },
  badge: {
    fontSize: 12,
    opacity: 0.7,
  },
  taskTitle: {
    color: '#2F7D4F',
  },
  input: {
    borderRadius: 10,
    borderWidth: 1,
    borderColor: '#B9B9B9',
    paddingHorizontal: 12,
    paddingVertical: 10,
    fontSize: 15,
  },
  buttonRow: {
    alignSelf: 'flex-start',
  },
  separator: {
    height: 12,
  },
  footer: {
    height: 24,
  },
  keyboardAvoid: {
    flex: 1,
  },
  listContent: {
    paddingBottom: 80,
  },
});