import { useState, useCallback, useRef, useEffect } from 'react';
import { useNavigate } from 'react-router-dom';
import { useMutation } from '@tanstack/react-query';
import {
  Box,
  Typography,
  Card,
  CardContent,
  TextField,
  Button,
  Grid,
  MenuItem,
  Autocomplete,
  CircularProgress,
} from '@mui/material';
import SendIcon from '@mui/icons-material/Send';
import { toast } from 'react-toastify';
import { proposalsApi, type CreateProposalRequest, type ServiceCategory, type Priority } from '../../../lib/api/proposals';
import { customersApi, type Customer } from '../../../lib/api/customers';
import { SERVICE_CATEGORIES, PRIORITIES } from '../../../constants';
import { queryClient } from '../../../lib/queryClient';

// Fix: WEB-M5 — form state allows empty serviceCategory during editing; validated before submit
interface ProposalFormState {
  workOrderNumber: string;
  customerName: string;
  customerAddress: string;
  scopeOfWork: string;
  serviceCategory: ServiceCategory | '';
  priority: Priority;
  notes: string;
}

// Fix: WEB-M6 — file validation constants
const MAX_FILE_SIZE_BYTES = 25 * 1024 * 1024; // 25 MB
const ALLOWED_MIME_TYPES = ['application/pdf'];

export default function ProposalFormPage() {
  const navigate = useNavigate();

  const [form, setForm] = useState<ProposalFormState>({
    workOrderNumber: '',
    customerName: '',
    customerAddress: '',
    scopeOfWork: '',
    serviceCategory: '',
    priority: 'Standard',
    notes: '',
  });

  const [customers, setCustomers] = useState<Customer[]>([]);
  const [customerLoading, setCustomerLoading] = useState(false);
  const [addresses, setAddresses] = useState<string[]>([]);
  const [vendorFile, setVendorFile] = useState<File | null>(null);
  const searchDebounceRef = useRef<ReturnType<typeof setTimeout> | null>(null);

  useEffect(() => {
    return () => {
      if (searchDebounceRef.current) clearTimeout(searchDebounceRef.current);
    };
  }, []);

  const handleChange = (field: keyof ProposalFormState, value: string) => {
    setForm((prev) => ({ ...prev, [field]: value }));
  };

  const searchCustomers = useCallback(async (query: string) => {
    if (query.length < 2) return;
    setCustomerLoading(true);
    try {
      const results = await customersApi.search(query);
      setCustomers(results);
    } catch {
      setCustomers([]);
    } finally {
      setCustomerLoading(false);
    }
  }, []);

  const handleCustomerSelect = (_: unknown, value: Customer | string | null) => {
    if (!value) {
      setForm((prev) => ({ ...prev, customerName: '', customerAddress: '' }));
      setAddresses([]);
      return;
    }
    if (typeof value === 'string') {
      setForm((prev) => ({ ...prev, customerName: value, customerAddress: '' }));
      setAddresses([]);
    } else {
      setForm((prev) => ({ ...prev, customerName: value.name, customerAddress: value.addresses[0] || '' }));
      setAddresses(value.addresses);
    }
  };

  const createMutation = useMutation({
    mutationFn: async () => {
      // Fix: WEB-M5 — cast validated form state to the strict request type
      const request: CreateProposalRequest = {
        workOrderNumber: form.workOrderNumber,
        customerName: form.customerName,
        customerAddress: form.customerAddress,
        scopeOfWork: form.scopeOfWork,
        serviceCategory: form.serviceCategory as ServiceCategory,
        priority: form.priority,
        notes: form.notes || undefined,
      };
      const proposal = await proposalsApi.create(request);

      if (vendorFile) {
        try {
          const { uploadUrl, vendorProposalId } = await proposalsApi.uploadAttachment(proposal.id, vendorFile.name);
          await fetch(uploadUrl, {
            method: 'PUT',
            body: vendorFile,
            headers: { 'Content-Type': vendorFile.type || 'application/pdf' },
          });
          await proposalsApi.confirmUpload(proposal.id, vendorProposalId);
        } catch {
          toast.warning(`Proposal ${proposal.proposalNumber} was created, but vendor PDF upload failed. You can re-upload from the proposal detail page.`);
        }
      }

      return proposal;
    },
    onSuccess: (proposal) => {
      queryClient.invalidateQueries({ queryKey: ['proposals'] });
      toast.success(`Proposal ${proposal.proposalNumber} submitted`);
      navigate(`/proposals/${proposal.id}`);
    },
    onError: (error: Error) => {
      toast.error(error.message || 'Failed to submit proposal');
    },
  });

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();
    createMutation.mutate();
  };

  const isValid =
    form.workOrderNumber.trim() &&
    form.customerName.trim() &&
    form.customerAddress.trim() &&
    form.scopeOfWork.trim() &&
    form.serviceCategory;

  return (
    <Box>
      <Typography variant="h5" sx={{ mb: 3 }}>
        New Proposal Request
      </Typography>

      <Card>
        <CardContent>
          <Box component="form" onSubmit={handleSubmit}>
            <Grid container spacing={3}>
              <Grid size={{ xs: 12, sm: 6 }}>
                <TextField
                  label="Work Order #"
                  required
                  fullWidth
                  value={form.workOrderNumber}
                  onChange={(e) => handleChange('workOrderNumber', e.target.value)}
                />
              </Grid>

              <Grid size={{ xs: 12, sm: 6 }}>
                <Autocomplete
                  freeSolo
                  options={customers}
                  getOptionLabel={(opt) => (typeof opt === 'string' ? opt : opt.name)}
                  loading={customerLoading}
                  onInputChange={(_, value, reason) => {
                    if (reason === 'input') {
                      handleChange('customerName', value);
                    }
                    if (searchDebounceRef.current) clearTimeout(searchDebounceRef.current);
                    searchDebounceRef.current = setTimeout(() => searchCustomers(value), 300);
                  }}
                  onChange={handleCustomerSelect}
                  renderInput={(params) => (
                    <TextField
                      {...params}
                      label="Customer"
                      required
                      slotProps={{
                        input: {
                          ...params.InputProps,
                          endAdornment: (
                            <>
                              {customerLoading && <CircularProgress size={20} />}
                              {params.InputProps.endAdornment}
                            </>
                          ),
                        },
                      }}
                    />
                  )}
                />
              </Grid>

              <Grid size={{ xs: 12 }}>
                {addresses.length > 1 ? (
                  <TextField
                    label="Customer Address"
                    required
                    fullWidth
                    select
                    value={form.customerAddress}
                    onChange={(e) => handleChange('customerAddress', e.target.value)}
                  >
                    {addresses.map((addr) => (
                      <MenuItem key={addr} value={addr}>
                        {addr}
                      </MenuItem>
                    ))}
                  </TextField>
                ) : (
                  <TextField
                    label="Customer Address"
                    required
                    fullWidth
                    value={form.customerAddress}
                    onChange={(e) => handleChange('customerAddress', e.target.value)}
                  />
                )}
              </Grid>

              <Grid size={{ xs: 12, sm: 6 }}>
                <TextField
                  label="Service Category"
                  required
                  fullWidth
                  select
                  value={form.serviceCategory}
                  onChange={(e) => handleChange('serviceCategory', e.target.value)}
                >
                  {SERVICE_CATEGORIES.map((cat) => (
                    <MenuItem key={cat} value={cat}>
                      {cat}
                    </MenuItem>
                  ))}
                </TextField>
              </Grid>

              <Grid size={{ xs: 12, sm: 6 }}>
                <TextField
                  label="Priority"
                  required
                  fullWidth
                  select
                  value={form.priority}
                  onChange={(e) => handleChange('priority', e.target.value)}
                >
                  {PRIORITIES.map((p) => (
                    <MenuItem key={p} value={p}>
                      {p}
                    </MenuItem>
                  ))}
                </TextField>
              </Grid>

              <Grid size={{ xs: 12 }}>
                <TextField
                  label="Scope of Work"
                  required
                  fullWidth
                  multiline
                  minRows={4}
                  value={form.scopeOfWork}
                  onChange={(e) => handleChange('scopeOfWork', e.target.value)}
                  placeholder="Describe the work needed..."
                />
              </Grid>

              <Grid size={{ xs: 12 }}>
                <TextField
                  label="Notes (optional)"
                  fullWidth
                  multiline
                  minRows={2}
                  value={form.notes}
                  onChange={(e) => handleChange('notes', e.target.value)}
                />
              </Grid>

              <Grid size={{ xs: 12 }}>
                <Button variant="outlined" component="label">
                  {vendorFile ? vendorFile.name : 'Attach Vendor Proposal (PDF)'}
                  <input
                    type="file"
                    hidden
                    accept=".pdf,application/pdf"
                    onChange={(e) => {
                      // Fix: WEB-M6 — validate file size and MIME type before accepting
                      const file = e.target.files?.[0] || null;
                      if (!file) {
                        setVendorFile(null);
                        return;
                      }
                      if (!file.name.toLowerCase().endsWith('.pdf') || !ALLOWED_MIME_TYPES.includes(file.type)) {
                        toast.error('Only PDF files are accepted.');
                        e.target.value = '';
                        return;
                      }
                      if (file.size > MAX_FILE_SIZE_BYTES) {
                        toast.error('File size exceeds the 25 MB limit. Please choose a smaller file.');
                        e.target.value = '';
                        return;
                      }
                      setVendorFile(file);
                    }}
                  />
                </Button>
              </Grid>

              <Grid size={{ xs: 12 }}>
                <Box sx={{ display: 'flex', gap: 2, justifyContent: 'flex-end' }}>
                  <Button variant="text" onClick={() => navigate(-1)}>
                    Cancel
                  </Button>
                  <Button
                    type="submit"
                    variant="contained"
                    startIcon={<SendIcon />}
                    disabled={!isValid || createMutation.isPending}
                  >
                    {createMutation.isPending ? 'Submitting...' : 'Submit Proposal'}
                  </Button>
                </Box>
              </Grid>
            </Grid>
          </Box>
        </CardContent>
      </Card>
    </Box>
  );
}