import { useEffect, useMemo, useState } from 'react';
import {
  KeyboardAvoidingView,
  Modal,
  Platform,
  Pressable,
  ScrollView,
  StyleSheet,
  Text,
  TextInput,
  View,
} from 'react-native';

import { CalendarEvent, createEvent, Project } from '@/src/lib/api';
import { useAuth } from '@/src/providers/auth-provider';

const PRIMARY = '#69c350';

type EventCreateModalProps = {
  visible: boolean;
  projects?: Project[];
  initialProjectId?: number | null;
  initialDate?: Date | null;
  onClose: () => void;
  onCreated: (event: CalendarEvent) => void | Promise<void>;
};

function pad(value: number): string {
  return String(value).padStart(2, '0');
}

function formatDateInput(date: Date): string {
  return `${pad(date.getDate())}.${pad(date.getMonth() + 1)}.${date.getFullYear()}`;
}

function formatTimeInput(date: Date): string {
  return `${pad(date.getHours())}:${pad(date.getMinutes())}`;
}

function createDefaults(initialDate?: Date | null) {
  const start = initialDate ? new Date(initialDate) : new Date();
  if (!initialDate) {
    start.setMinutes(Math.ceil(start.getMinutes() / 15) * 15, 0, 0);
  } else {
    start.setHours(9, 0, 0, 0);
  }
  const end = new Date(start.getTime() + 60 * 60 * 1000);
  return {
    startDate: formatDateInput(start),
    startTime: formatTimeInput(start),
    endDate: formatDateInput(end),
    endTime: formatTimeInput(end),
  };
}

function parseLocalDate(dateValue: string, timeValue: string): Date | null {
  const match = dateValue.trim().match(/^(\d{1,2})\.(\d{1,2})\.(\d{4})$/);
  const timeMatch = timeValue.trim().match(/^(\d{1,2}):(\d{2})$/);
  if (!match || !timeMatch) return null;

  const day = Number(match[1]);
  const month = Number(match[2]);
  const year = Number(match[3]);
  const hours = Number(timeMatch[1]);
  const minutes = Number(timeMatch[2]);
  if (hours > 23 || minutes > 59) return null;

  const date = new Date(year, month - 1, day, hours, minutes, 0, 0);
  if (
    date.getFullYear() !== year ||
    date.getMonth() !== month - 1 ||
    date.getDate() !== day
  ) {
    return null;
  }
  return date;
}

function relationId(value: unknown): number | null {
  if (!value) return null;
  if (typeof value === 'object') {
    const id = (value as { id?: number | string }).id;
    return id ? Number(id) : null;
  }
  const id = Number(value);
  return Number.isFinite(id) ? id : null;
}

export function EventCreateModal({
  visible,
  projects = [],
  initialProjectId = null,
  initialDate = null,
  onClose,
  onCreated,
}: EventCreateModalProps) {
  const { token } = useAuth();
  const [name, setName] = useState('');
  const [notes, setNotes] = useState('');
  const [link, setLink] = useState('');
  const [startDate, setStartDate] = useState('');
  const [startTime, setStartTime] = useState('');
  const [endDate, setEndDate] = useState('');
  const [endTime, setEndTime] = useState('');
  const [selectedProjectId, setSelectedProjectId] = useState<number | null>(initialProjectId);
  const [projectSearch, setProjectSearch] = useState('');
  const [saving, setSaving] = useState(false);
  const [error, setError] = useState<string | null>(null);

  useEffect(() => {
    if (!visible) return;
    const defaults = createDefaults(initialDate);
    setName('');
    setNotes('');
    setLink('');
    setStartDate(defaults.startDate);
    setStartTime(defaults.startTime);
    setEndDate(defaults.endDate);
    setEndTime(defaults.endTime);
    setSelectedProjectId(initialProjectId);
    setProjectSearch('');
    setError(null);
  }, [initialDate, initialProjectId, visible]);

  const selectedProject = useMemo(
    () => projects.find((project) => Number(project.id) === selectedProjectId) || null,
    [projects, selectedProjectId]
  );

  const projectOptions = useMemo(() => {
    const terms = projectSearch.trim().toLowerCase().split(/\s+/).filter(Boolean);
    return projects
      .filter((project) => {
        if (terms.length === 0) return true;
        const haystack = `${project.name || ''} ${project.projectNumber || ''}`.toLowerCase();
        return terms.every((term) => haystack.includes(term));
      })
      .slice(0, 8);
  }, [projectSearch, projects]);

  async function save() {
    if (!token || saving) return;
    const title = name.trim();
    if (!title) {
      setError('Bitte einen Namen für den Termin eingeben.');
      return;
    }

    const start = parseLocalDate(startDate, startTime);
    const end = parseLocalDate(endDate, endTime);
    if (!start || !end) {
      setError('Bitte Datum und Uhrzeit im angegebenen Format eingeben.');
      return;
    }
    if (end <= start) {
      setError('Das Ende muss nach dem Beginn liegen.');
      return;
    }

    setSaving(true);
    setError(null);
    try {
      const event = await createEvent(token, {
        name: title,
        startDate: start.toISOString(),
        endDate: end.toISOString(),
        project: selectedProjectId,
        customer: relationId(selectedProject?.customer),
        notes: notes.trim() || null,
        link: link.trim() || null,
        state: 'Final',
        repeatInterval: 'Keine Wiederholung',
      });
      await onCreated(event);
      onClose();
    } catch (err) {
      setError(err instanceof Error ? err.message : 'Der Termin konnte nicht gespeichert werden.');
    } finally {
      setSaving(false);
    }
  }

  return (
    <Modal visible={visible} transparent animationType="fade" onRequestClose={onClose}>
      <View style={styles.overlay}>
        <KeyboardAvoidingView behavior={Platform.OS === 'ios' ? 'padding' : undefined} style={styles.keyboardWrap}>
          <View style={styles.card}>
            <Text style={styles.title}>Neuer Termin</Text>
            <ScrollView style={styles.scroll} contentContainerStyle={styles.form} keyboardShouldPersistTaps="handled">
              <TextInput
                autoFocus
                placeholder="Name *"
                placeholderTextColor="#9ca3af"
                style={styles.input}
                value={name}
                onChangeText={setName}
              />

              <Text style={styles.label}>Beginn</Text>
              <View style={styles.row}>
                <TextInput
                  placeholder="TT.MM.JJJJ"
                  placeholderTextColor="#9ca3af"
                  style={[styles.input, styles.dateInput]}
                  value={startDate}
                  onChangeText={setStartDate}
                  keyboardType="numbers-and-punctuation"
                />
                <TextInput
                  placeholder="HH:MM"
                  placeholderTextColor="#9ca3af"
                  style={[styles.input, styles.timeInput]}
                  value={startTime}
                  onChangeText={setStartTime}
                  keyboardType="numbers-and-punctuation"
                />
              </View>

              <Text style={styles.label}>Ende</Text>
              <View style={styles.row}>
                <TextInput
                  placeholder="TT.MM.JJJJ"
                  placeholderTextColor="#9ca3af"
                  style={[styles.input, styles.dateInput]}
                  value={endDate}
                  onChangeText={setEndDate}
                  keyboardType="numbers-and-punctuation"
                />
                <TextInput
                  placeholder="HH:MM"
                  placeholderTextColor="#9ca3af"
                  style={[styles.input, styles.timeInput]}
                  value={endTime}
                  onChangeText={setEndTime}
                  keyboardType="numbers-and-punctuation"
                />
              </View>

              <Text style={styles.label}>Projekt</Text>
              {selectedProject ? (
                <View style={styles.selectedProject}>
                  <View style={styles.selectedProjectMain}>
                    <Text style={styles.selectedProjectName}>{selectedProject.name}</Text>
                    {selectedProject.projectNumber ? (
                      <Text style={styles.selectedProjectNumber}>Nr. {selectedProject.projectNumber}</Text>
                    ) : null}
                  </View>
                  <Pressable onPress={() => setSelectedProjectId(null)}>
                    <Text style={styles.removeProject}>Ändern</Text>
                  </Pressable>
                </View>
              ) : (
                <>
                  <TextInput
                    placeholder="Projekt suchen (optional)"
                    placeholderTextColor="#9ca3af"
                    style={styles.input}
                    value={projectSearch}
                    onChangeText={setProjectSearch}
                  />
                  {projectOptions.map((project) => (
                    <Pressable
                      key={String(project.id)}
                      style={styles.projectOption}
                      onPress={() => setSelectedProjectId(Number(project.id))}>
                      <Text style={styles.projectOptionName}>{project.name}</Text>
                      <Text style={styles.projectOptionNumber}>{project.projectNumber || `#${project.id}`}</Text>
                    </Pressable>
                  ))}
                </>
              )}

              <TextInput
                placeholder="Link (optional)"
                placeholderTextColor="#9ca3af"
                style={styles.input}
                value={link}
                onChangeText={setLink}
                autoCapitalize="none"
                keyboardType="url"
              />
              <TextInput
                placeholder="Notizen (optional)"
                placeholderTextColor="#9ca3af"
                style={[styles.input, styles.multiline]}
                value={notes}
                onChangeText={setNotes}
                multiline
              />
              {error ? <Text style={styles.error}>{error}</Text> : null}
            </ScrollView>

            <View style={styles.actions}>
              <Pressable style={styles.secondaryButton} onPress={onClose} disabled={saving}>
                <Text style={styles.secondaryButtonText}>Abbrechen</Text>
              </Pressable>
              <Pressable style={[styles.primaryButton, saving ? styles.disabled : null]} onPress={save} disabled={saving}>
                <Text style={styles.primaryButtonText}>{saving ? 'Speichere...' : 'Anlegen'}</Text>
              </Pressable>
            </View>
          </View>
        </KeyboardAvoidingView>
      </View>
    </Modal>
  );
}

const styles = StyleSheet.create({
  overlay: { flex: 1, backgroundColor: 'rgba(17, 24, 39, 0.45)', justifyContent: 'center', padding: 20 },
  keyboardWrap: { width: '100%' },
  card: { maxHeight: '92%', backgroundColor: '#ffffff', borderRadius: 14, padding: 16, gap: 12 },
  title: { color: '#111827', fontSize: 18, fontWeight: '700' },
  scroll: { flexShrink: 1 },
  form: { gap: 10, paddingBottom: 4 },
  label: { color: '#374151', fontSize: 13, fontWeight: '700' },
  input: {
    borderWidth: 1,
    borderColor: '#d1d5db',
    borderRadius: 10,
    paddingHorizontal: 12,
    paddingVertical: 10,
    fontSize: 15,
    color: '#111827',
    backgroundColor: '#ffffff',
  },
  row: { flexDirection: 'row', gap: 8 },
  dateInput: { flex: 1 },
  timeInput: { width: 92 },
  multiline: { minHeight: 90, textAlignVertical: 'top' },
  selectedProject: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    borderWidth: 1,
    borderColor: '#b9e3ae',
    backgroundColor: '#eff9ea',
    borderRadius: 10,
    padding: 10,
    gap: 8,
  },
  selectedProjectMain: { flex: 1 },
  selectedProjectName: { color: '#111827', fontSize: 14, fontWeight: '700' },
  selectedProjectNumber: { color: '#6b7280', fontSize: 12 },
  removeProject: { color: '#3d7a30', fontSize: 13, fontWeight: '700' },
  projectOption: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    borderBottomWidth: 1,
    borderBottomColor: '#e5e7eb',
    paddingVertical: 8,
    gap: 8,
  },
  projectOptionName: { flex: 1, color: '#111827', fontSize: 14, fontWeight: '600' },
  projectOptionNumber: { color: '#6b7280', fontSize: 12 },
  error: { color: '#dc2626', fontSize: 13 },
  actions: { flexDirection: 'row', justifyContent: 'flex-end', gap: 8 },
  secondaryButton: {
    minHeight: 40,
    borderWidth: 1,
    borderColor: '#d1d5db',
    borderRadius: 10,
    paddingHorizontal: 14,
    alignItems: 'center',
    justifyContent: 'center',
  },
  secondaryButtonText: { color: '#374151', fontWeight: '600' },
  primaryButton: {
    minHeight: 40,
    borderRadius: 10,
    paddingHorizontal: 14,
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: PRIMARY,
  },
  primaryButtonText: { color: '#ffffff', fontWeight: '700' },
  disabled: { opacity: 0.6 },
});