import { useState } from 'react';
import {
  ActionIcon,
  Alert,
  Badge,
  Button,
  Card,
  Divider,
  Group,
  Modal,
  NumberInput,
  Paper,
  Select,
  SimpleGrid,
  Stack,
  Switch,
  Table,
  Text,
  TextInput,
  ThemeIcon,
  Title,
  rem,
} from '@mantine/core';
import {
  IconBook2,
  IconCertificate,
  IconCheck,
  IconCreditCard,
  IconEdit,
  IconId,
  IconInfoCircle,
  IconShieldCheck,
} from '@tabler/icons-react';
import { notify } from '@ema-platform/ui';

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------
interface CertFee {
  id: string;
  certType: string;
  icon: typeof IconBook2;
  color: string;
  description: string;
  fees: { label: string; amount: number; editable: boolean }[];
  enabled: boolean;
}

interface PaymentMethod {
  id: string;
  name: string;
  shortName: string;
  accountNumber: string;
  accountName: string;
  instructions: string;
  enabled: boolean;
}

// ---------------------------------------------------------------------------
// Initial state
// ---------------------------------------------------------------------------
const INITIAL_CERT_FEES: CertFee[] = [
  {
    id: 'seaman-book',
    certType: 'Seaman Book',
    icon: IconBook2,
    color: 'blue',
    description: 'Official EMA seafarer identification book — valid 5 years',
    fees: [
      { label: 'Application Fee',          amount: 500, editable: true },
      { label: 'Document Verification Fee',amount: 200, editable: true },
    ],
    enabled: true,
  },
  {
    id: 'btc',
    certType: 'Basic Training Certificate (BTC)',
    icon: IconCertificate,
    color: 'teal',
    description: 'EMA-issued BTC certifying all 5 basic safety training courses — valid 5 years',
    fees: [
      { label: 'Application Fee',          amount: 300, editable: true },
      { label: 'Document Verification Fee',amount: 100, editable: true },
    ],
    enabled: true,
  },
  {
    id: 'bsid',
    certType: 'BSID (Biometric Seafarer ID)',
    icon: IconId,
    color: 'violet',
    description: 'Biometric Seafarer Identity Document — valid 5 years',
    fees: [
      { label: 'Application Fee',          amount: 100, editable: true },
      { label: 'Card Production Fee',      amount: 150, editable: true },
    ],
    enabled: true,
  },
  {
    id: 'certificate',
    certType: 'Certificate (CoC / CoP)',
    icon: IconShieldCheck,
    color: 'orange',
    description: 'Certificate of Competency or Certificate of Proficiency under STCW',
    fees: [
      { label: 'Application Fee',          amount: 800, editable: true },
      { label: 'Examination Fee',          amount: 400, editable: true },
      { label: 'Certificate Issuance Fee', amount: 200, editable: true },
    ],
    enabled: true,
  },
];

const INITIAL_PAYMENT_METHODS: PaymentMethod[] = [
  {
    id: 'cbe',
    name: 'Commercial Bank of Ethiopia',
    shortName: 'CBE',
    accountNumber: '1000123456789',
    accountName: 'EMA Maritime Authority',
    instructions: 'Transfer the exact fee amount. Use your full name as the transfer description.',
    enabled: true,
  },
  {
    id: 'telebirr',
    name: 'Telebirr (Ethio Telecom)',
    shortName: 'Telebirr',
    accountNumber: '+251 11 551 0000',
    accountName: 'EMA Maritime Authority',
    instructions: 'Send to Telebirr number. Screenshot your confirmation and upload it with your application.',
    enabled: true,
  },
];

// ---------------------------------------------------------------------------
// Fee edit modal
// ---------------------------------------------------------------------------
function FeeEditModal({
  cert,
  opened,
  onClose,
  onSave,
}: {
  cert: CertFee | null;
  opened: boolean;
  onClose: () => void;
  onSave: (id: string, fees: CertFee['fees']) => void;
}) {
  const [fees, setFees] = useState<CertFee['fees']>(cert?.fees ?? []);

  const handleOpen = () => setFees(cert?.fees ?? []);

  return (
    <Modal
      opened={opened}
      onClose={onClose}
      title={<Group gap="xs"><IconCreditCard size={18} /><Text fw={700}>Edit Fees — {cert?.certType}</Text></Group>}
      size="md"
      radius="lg"
      onTransitionEnd={() => { if (opened) handleOpen(); }}
    >
      <Stack gap="md">
        <Alert variant="light" color="blue" icon={<IconInfoCircle size={15} />}>
          Changes take effect on new applications immediately. Existing applications retain the fee at time of submission.
        </Alert>
        {fees.map((fee, i) => (
          <Group key={fee.label} gap="sm" align="flex-end">
            <TextInput label="Fee Label" value={fee.label} disabled style={{ flex: 1 }} size="sm" />
            <NumberInput
              label="Amount (ETB)"
              value={fee.amount}
              min={0}
              step={50}
              style={{ width: rem(140) }}
              size="sm"
              disabled={!fee.editable}
              onChange={(v) =>
                setFees((prev) => prev.map((f, idx) => idx === i ? { ...f, amount: Number(v) || 0 } : f))
              }
            />
          </Group>
        ))}
        <Divider />
        <Paper withBorder radius="md" p="sm" bg="gray.0">
          <Group justify="space-between">
            <Text fz="sm" fw={700}>Total</Text>
            <Text fz="sm" fw={700} c="blue">ETB {fees.reduce((s, f) => s + f.amount, 0).toFixed(2)}</Text>
          </Group>
        </Paper>
        <Group justify="flex-end">
          <Button variant="default" onClick={onClose}>Cancel</Button>
          <Button leftSection={<IconCheck size={15} />} onClick={() => { onSave(cert!.id, fees); onClose(); }}>
            Save Fees
          </Button>
        </Group>
      </Stack>
    </Modal>
  );
}

// ---------------------------------------------------------------------------
// Payment method edit modal
// ---------------------------------------------------------------------------
function MethodEditModal({
  method,
  opened,
  onClose,
  onSave,
}: {
  method: PaymentMethod | null;
  opened: boolean;
  onClose: () => void;
  onSave: (updated: PaymentMethod) => void;
}) {
  const [form, setForm] = useState<PaymentMethod>(method ?? INITIAL_PAYMENT_METHODS[0]);
  const set = (k: keyof PaymentMethod, v: string) => setForm((p) => ({ ...p, [k]: v }));

  return (
    <Modal
      opened={opened}
      onClose={onClose}
      title={<Group gap="xs"><IconCreditCard size={18} /><Text fw={700}>Edit Payment Method — {method?.shortName}</Text></Group>}
      size="md"
      radius="lg"
      onTransitionEnd={() => { if (opened && method) setForm(method); }}
    >
      <Stack gap="md">
        <TextInput label="Account Number / Phone" value={form.accountNumber} onChange={(e) => set('accountNumber', e.currentTarget.value)} />
        <TextInput label="Account Name" value={form.accountName} onChange={(e) => set('accountName', e.currentTarget.value)} />
        <TextInput label="Instructions (shown to applicant)" value={form.instructions} onChange={(e) => set('instructions', e.currentTarget.value)} />
        <Group justify="flex-end">
          <Button variant="default" onClick={onClose}>Cancel</Button>
          <Button leftSection={<IconCheck size={15} />} onClick={() => { onSave(form); onClose(); }}>Save</Button>
        </Group>
      </Stack>
    </Modal>
  );
}

// ---------------------------------------------------------------------------
// Main page
// ---------------------------------------------------------------------------
export function PaymentConfigPage() {
  const [certFees, setCertFees] = useState<CertFee[]>(INITIAL_CERT_FEES);
  const [methods, setMethods] = useState<PaymentMethod[]>(INITIAL_PAYMENT_METHODS);

  const [editingCert, setEditingCert] = useState<CertFee | null>(null);
  const [editingMethod, setEditingMethod] = useState<PaymentMethod | null>(null);

  const totalCombined = certFees
    .filter((c) => c.enabled)
    .flatMap((c) => c.fees)
    .reduce((s, f) => s + f.amount, 0);

  const handleSaveFees = (id: string, fees: CertFee['fees']) => {
    setCertFees((prev) => prev.map((c) => c.id === id ? { ...c, fees } : c));
    notify.success('Fees updated successfully.');
  };

  const handleToggleCert = (id: string) => {
    setCertFees((prev) => prev.map((c) => c.id === id ? { ...c, enabled: !c.enabled } : c));
  };

  const handleSaveMethod = (updated: PaymentMethod) => {
    setMethods((prev) => prev.map((m) => m.id === updated.id ? updated : m));
    notify.success('Payment method updated.');
  };

  const handleToggleMethod = (id: string) => {
    setMethods((prev) => prev.map((m) => m.id === id ? { ...m, enabled: !m.enabled } : m));
  };

  return (
    <Stack gap="md">
      {/* Header */}
      <Group justify="space-between" align="flex-start">
        <div>
          <Title order={3}>Payment Configuration</Title>
          <Text fz="sm" c="dimmed">Manage certificate fees and accepted payment methods shown to applicants</Text>
        </div>
        <Badge size="lg" variant="light" color="blue">
          Combined Total: ETB {totalCombined.toFixed(2)}
        </Badge>
      </Group>

      {/* Fee summary table */}
      <Paper withBorder radius="lg" p="xl">
        <Group justify="space-between" mb="lg">
          <Text fw={700} fz="md">Certificate Fees</Text>
          <Text fz="xs" c="dimmed">Click Edit to change fee amounts</Text>
        </Group>

        <Table highlightOnHover verticalSpacing="sm" fz="sm">
          <Table.Thead bg="var(--mantine-color-default-hover)">
            <Table.Tr>
              {['Certificate Type', 'Fee Breakdown', 'Total', 'Status', ''].map((h) => (
                <Table.Th key={h} style={{ fontSize: rem(11), textTransform: 'uppercase', color: 'var(--mantine-color-dimmed)' }}>{h}</Table.Th>
              ))}
            </Table.Tr>
          </Table.Thead>
          <Table.Tbody>
            {certFees.map((cert) => {
              const CertIcon = cert.icon;
              const total = cert.fees.reduce((s, f) => s + f.amount, 0);
              return (
                <Table.Tr key={cert.id} style={{ opacity: cert.enabled ? 1 : 0.5 }}>
                  <Table.Td>
                    <Group gap="sm" wrap="nowrap">
                      <ThemeIcon size="md" variant="light" color={cert.color} radius="md">
                        <CertIcon size={16} stroke={1.5} />
                      </ThemeIcon>
                      <div>
                        <Text fz="sm" fw={600}>{cert.certType}</Text>
                        <Text fz="xs" c="dimmed">{cert.description}</Text>
                      </div>
                    </Group>
                  </Table.Td>
                  <Table.Td>
                    <Stack gap={2}>
                      {cert.fees.map((f) => (
                        <Group key={f.label} gap={6}>
                          <Text fz="xs" c="dimmed">{f.label}:</Text>
                          <Text fz="xs" fw={500}>ETB {f.amount.toFixed(2)}</Text>
                        </Group>
                      ))}
                    </Stack>
                  </Table.Td>
                  <Table.Td>
                    <Text fz="sm" fw={700} c={cert.enabled ? 'blue.7' : 'dimmed'}>ETB {total.toFixed(2)}</Text>
                  </Table.Td>
                  <Table.Td>
                    <Switch
                      checked={cert.enabled}
                      onChange={() => handleToggleCert(cert.id)}
                      size="sm"
                      color="teal"
                      label={cert.enabled ? 'Active' : 'Disabled'}
                    />
                  </Table.Td>
                  <Table.Td>
                    <ActionIcon variant="light" color="blue" size="md" onClick={() => setEditingCert(cert)}>
                      <IconEdit size={15} />
                    </ActionIcon>
                  </Table.Td>
                </Table.Tr>
              );
            })}
          </Table.Tbody>
          <Table.Tfoot>
            <Table.Tr>
              <Table.Td colSpan={2}><Text fz="sm" fw={700} ta="right">Grand Total (all active)</Text></Table.Td>
              <Table.Td><Text fz="sm" fw={800} c="blue">ETB {totalCombined.toFixed(2)}</Text></Table.Td>
              <Table.Td colSpan={2} />
            </Table.Tr>
          </Table.Tfoot>
        </Table>
      </Paper>

      {/* Payment methods */}
      <Paper withBorder radius="lg" p="xl">
        <Text fw={700} fz="md" mb="lg">Accepted Payment Methods</Text>
        <SimpleGrid cols={{ base: 1, sm: 2 }} spacing="md">
          {methods.map((method) => (
            <Card key={method.id} withBorder radius="md" p="md" style={{ opacity: method.enabled ? 1 : 0.6 }}>
              <Group justify="space-between" mb="sm">
                <Group gap="sm">
                  <ThemeIcon size="lg" variant="light" color={method.enabled ? 'blue' : 'gray'} radius="md">
                    <IconCreditCard size={18} stroke={1.5} />
                  </ThemeIcon>
                  <div>
                    <Text fw={700} fz="sm">{method.name}</Text>
                    <Badge size="xs" variant="light" color={method.enabled ? 'teal' : 'gray'}>
                      {method.enabled ? 'Active' : 'Disabled'}
                    </Badge>
                  </div>
                </Group>
                <Group gap="xs">
                  <Switch checked={method.enabled} onChange={() => handleToggleMethod(method.id)} size="sm" color="teal" />
                  <ActionIcon variant="light" color="blue" size="md" onClick={() => setEditingMethod(method)}>
                    <IconEdit size={15} />
                  </ActionIcon>
                </Group>
              </Group>
              <Divider mb="sm" />
              <Stack gap={4}>
                <Group justify="space-between">
                  <Text fz="xs" c="dimmed">Account / Number</Text>
                  <Text fz="xs" fw={600}>{method.accountNumber}</Text>
                </Group>
                <Group justify="space-between">
                  <Text fz="xs" c="dimmed">Account Name</Text>
                  <Text fz="xs" fw={600}>{method.accountName}</Text>
                </Group>
              </Stack>
              <Text fz="xs" c="dimmed" mt="sm" lh={1.4}>{method.instructions}</Text>
            </Card>
          ))}
        </SimpleGrid>
      </Paper>

      {/* Fee edit modal */}
      <FeeEditModal
        cert={editingCert}
        opened={!!editingCert}
        onClose={() => setEditingCert(null)}
        onSave={handleSaveFees}
      />

      {/* Method edit modal */}
      <MethodEditModal
        method={editingMethod}
        opened={!!editingMethod}
        onClose={() => setEditingMethod(null)}
        onSave={handleSaveMethod}
      />
    </Stack>
  );
}