import React, { useState, useCallback } from 'react';
import {
  View,
  StyleSheet,
  ScrollView,
  Alert,
  KeyboardAvoidingView,
  Platform,
} from 'react-native';
import {
  TextInput,
  Button,
  Text,
  SegmentedButtons,
  Snackbar,
} from 'react-native-paper';
import { useNavigation } from '@react-navigation/native';
import NetInfo from '@react-native-community/netinfo';
import {
  proposalsApi,
  type CreateProposalRequest,
} from '../../lib/api/proposals';
import { FilePickerButton } from '../../components/FilePickerButton';
import {
  useOfflineDraft,
  queueOfflineSubmission,
} from '../../hooks/useOfflineDraft';
import { SERVICE_CATEGORIES, PRIORITIES } from '../../constants';

interface DraftForm extends Record<string, unknown> {
  workOrderNumber: string;
  customerName: string;
  customerAddress: string;
  scopeOfWork: string;
  serviceCategory: string;
  priority: string;
  notes: string;
}

const emptyDraft: DraftForm = {
  workOrderNumber: '',
  customerName: '',
  customerAddress: '',
  scopeOfWork: '',
  serviceCategory: 'General',
  priority: 'Standard',
  notes: '',
};

export function NewProposalScreen() {
  const navigation = useNavigation();
  const { draft, updateDraft, clearDraft, isLoaded } =
    useOfflineDraft(emptyDraft);
  const [submitting, setSubmitting] = useState(false);
  const [proposalId, setProposalId] = useState<string | null>(null);
  const [snackbar, setSnackbar] = useState('');

  const validate = (): string | null => {
    if (!draft.customerName.trim()) return 'Customer name is required';
    if (!draft.customerAddress.trim()) return 'Customer address is required';
    if (!draft.scopeOfWork.trim()) return 'Scope of work is required';
    if (!draft.workOrderNumber.trim()) return 'Work order number is required';
    return null;
  };

  const handleSubmit = useCallback(async () => {
    const error = validate();
    if (error) {
      Alert.alert('Validation', error);
      return;
    }

    setSubmitting(true);
    try {
      const payload: CreateProposalRequest = {
        workOrderNumber: draft.workOrderNumber.trim(),
        customerName: draft.customerName.trim(),
        customerAddress: draft.customerAddress.trim(),
        scopeOfWork: draft.scopeOfWork.trim(),
        serviceCategory: draft.serviceCategory as CreateProposalRequest['serviceCategory'],
        priority: draft.priority as CreateProposalRequest['priority'],
        notes: draft.notes.trim() || undefined,
      };

      const netState = await NetInfo.fetch();
      if (!netState.isConnected) {
        await queueOfflineSubmission(payload);
        await clearDraft();
        Alert.alert(
          'Saved Offline',
          'Your proposal has been queued and will submit when you reconnect.',
          [{ text: 'OK', onPress: () => navigation.goBack() }],
        );
        return;
      }

      const result = await proposalsApi.create(payload);
      setProposalId(result.id);
      await clearDraft();
      setSnackbar(`Proposal ${result.proposalNumber} submitted!`);
      setTimeout(() => navigation.goBack(), 1500);
    } catch (err) {
      Alert.alert(
        'Error',
        err instanceof Error ? err.message : 'Failed to submit proposal.',
      );
    } finally {
      setSubmitting(false);
    }
  }, [draft, clearDraft, navigation]);

  if (!isLoaded) return null;

  return (
    <KeyboardAvoidingView
      style={styles.container}
      behavior={Platform.OS === 'ios' ? 'padding' : undefined}
    >
      <ScrollView contentContainerStyle={styles.scroll}>
        <TextInput
          label="Work Order Number"
          value={draft.workOrderNumber}
          onChangeText={(v) => updateDraft({ workOrderNumber: v })}
          mode="outlined"
          style={styles.input}
        />

        <TextInput
          label="Customer Name"
          value={draft.customerName}
          onChangeText={(v) => updateDraft({ customerName: v })}
          mode="outlined"
          style={styles.input}
        />

        <TextInput
          label="Customer Address / Site Location"
          value={draft.customerAddress}
          onChangeText={(v) => updateDraft({ customerAddress: v })}
          mode="outlined"
          multiline
          numberOfLines={2}
          style={styles.input}
        />

        <Text variant="labelLarge" style={styles.label}>
          Service Category
        </Text>
        <SegmentedButtons
          value={draft.serviceCategory}
          onValueChange={(v) => updateDraft({ serviceCategory: v })}
          buttons={SERVICE_CATEGORIES.map((c) => ({
            value: c,
            label: c,
          }))}
          style={styles.segmented}
          density="small"
        />

        <Text variant="labelLarge" style={styles.label}>
          Priority
        </Text>
        <SegmentedButtons
          value={draft.priority}
          onValueChange={(v) => updateDraft({ priority: v })}
          buttons={PRIORITIES.map((p) => ({ value: p, label: p }))}
          style={styles.segmented}
        />

        <TextInput
          label="Scope of Work"
          value={draft.scopeOfWork}
          onChangeText={(v) => updateDraft({ scopeOfWork: v })}
          mode="outlined"
          multiline
          numberOfLines={6}
          placeholder="Describe the work to be done..."
          style={styles.input}
        />

        <Text variant="labelLarge" style={styles.label}>
          Vendor Proposal (optional)
        </Text>
        {proposalId ? (
          <FilePickerButton
            onFileSelected={() => setSnackbar('Vendor PDF attached')}
            getUploadUrl={(fileName) =>
              proposalsApi.uploadAttachment(proposalId, fileName)
            }
          />
        ) : (
          <Text variant="bodySmall" style={styles.hint}>
            Submit the proposal first, then attach vendor PDFs
          </Text>
        )}

        <TextInput
          label="Additional Notes"
          value={draft.notes}
          onChangeText={(v) => updateDraft({ notes: v })}
          mode="outlined"
          multiline
          numberOfLines={3}
          style={styles.input}
        />

        <Button
          mode="contained"
          onPress={handleSubmit}
          loading={submitting}
          disabled={submitting}
          contentStyle={styles.submitContent}
          style={styles.submit}
        >
          Submit Proposal
        </Button>
      </ScrollView>

      <Snackbar
        visible={!!snackbar}
        onDismiss={() => setSnackbar('')}
        duration={3000}
      >
        {snackbar}
      </Snackbar>
    </KeyboardAvoidingView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#FAFAFA',
  },
  scroll: {
    padding: 16,
    paddingBottom: 40,
  },
  input: {
    marginBottom: 12,
  },
  label: {
    marginBottom: 8,
    marginTop: 4,
    color: '#424242',
  },
  segmented: {
    marginBottom: 16,
  },
  hint: {
    color: '#9E9E9E',
    marginBottom: 12,
  },
  submit: {
    marginTop: 16,
    borderRadius: 8,
  },
  submitContent: {
    paddingVertical: 8,
  },
});