// CloseFiscalYearWizard - Multi-step wizard for year-end closing (årsafslutning)

import { useState, useEffect, useMemo } from 'react';
import {
  Modal,
  Steps,
  Button,
  Alert,
  Typography,
  Table,
  Statistic,
  Row,
  Col,
  Card,
  Select,
  Divider,
  Checkbox,
  Result,
  Tag,
  Form,
} from 'antd';
import {
  CheckCircleOutlined,
  WarningOutlined,
  LockOutlined,
  ArrowRightOutlined,
  ExclamationCircleOutlined,
} from '@ant-design/icons';
import { usePeriodStore } from '@/stores/periodStore';
import {
  calculateClosingSummary,
  validateFiscalYearClose,
  generateClosingEntries,
  calculateClosingBalances,
  type FiscalYearClosingSummary,
  type GeneratedClosingEntry,
} from '@/lib/fiscalYear';
import { formatCurrency } from '@/lib/formatters';
import type { FiscalYear } from '@/types/periods';
import type { Account, Transaction } from '@/types/accounting';
import { useCloseFiscalYear, useCreateFiscalYear } from '@/api/mutations/fiscalYearMutations';
import { useCreateJournalEntryDraft, useUpdateJournalEntryDraft } from '@/api/mutations/draftMutations';
import { message } from 'antd';
import dayjs from 'dayjs';

const { Text, Title, Paragraph } = Typography;

interface CloseFiscalYearWizardProps {
  open: boolean;
  fiscalYear: FiscalYear;
  accounts: Account[];
  transactions: Transaction[];
  onClose: () => void;
  onSuccess?: () => void;
}

type WizardStep = 'validation' | 'summary' | 'transfer' | 'confirm' | 'complete';

// Default "Overført resultat" account (equity)
const DEFAULT_RESULT_ACCOUNT = {
  id: 'acc-3900',
  accountNumber: '3900',
  name: 'Overført resultat',
};

export default function CloseFiscalYearWizard({
  open,
  fiscalYear,
  accounts,
  transactions,
  onClose,
  onSuccess,
}: CloseFiscalYearWizardProps) {
  const [currentStep, setCurrentStep] = useState<WizardStep>('validation');
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [resultAccountId, setResultAccountId] = useState<string>(DEFAULT_RESULT_ACCOUNT.id);
  const [createNextYear, setCreateNextYear] = useState(true);
  const [closeOpenPeriods, setCloseOpenPeriods] = useState(true);
  const [confirmLock, setConfirmLock] = useState(false);

  const {
    periods,
    closeFiscalYear,
    lockFiscalYear,
    closePeriod,
    lockPeriod,
  } = usePeriodStore();

  const closeFiscalYearMutation = useCloseFiscalYear();
  const createFiscalYearMutation = useCreateFiscalYear();
  const createDraftMutation = useCreateJournalEntryDraft();
  const updateDraftMutation = useUpdateJournalEntryDraft();

  // Reset wizard when opened
  useEffect(() => {
    if (open) {
      setCurrentStep('validation');
      setIsSubmitting(false);
      setConfirmLock(false);
    }
  }, [open]);

  // Calculate closing balances
  const closingBalances = useMemo(
    () => calculateClosingBalances(fiscalYear, accounts, transactions),
    [fiscalYear, accounts, transactions]
  );

  // Calculate summary
  const summary: FiscalYearClosingSummary = useMemo(
    () => calculateClosingSummary(fiscalYear, periods, closingBalances, transactions),
    [fiscalYear, periods, closingBalances, transactions]
  );

  // Validate fiscal year close
  const validation = useMemo(
    () => validateFiscalYearClose(fiscalYear, periods),
    [fiscalYear, periods]
  );

  // Generate closing entries preview
  const closingEntries: GeneratedClosingEntry[] = useMemo(() => {
    const resultAccount = accounts.find((a) => a.id === resultAccountId) || {
      id: resultAccountId,
      accountNumber: DEFAULT_RESULT_ACCOUNT.accountNumber,
      name: DEFAULT_RESULT_ACCOUNT.name,
    };

    return generateClosingEntries(
      fiscalYear,
      closingBalances,
      resultAccount.id,
      resultAccount.accountNumber,
      resultAccount.name
    );
  }, [fiscalYear, closingBalances, resultAccountId, accounts]);

  // Equity accounts for result transfer
  const equityAccounts = useMemo(
    () => accounts.filter((a) => a.type === 'equity'),
    [accounts]
  );

  // Year periods
  const yearPeriods = useMemo(
    () => periods.filter((p) => p.fiscalYearId === fiscalYear.id),
    [periods, fiscalYear.id]
  );

  const openPeriodsInYear = yearPeriods.filter((p) => p.status === 'open');

  const handleNext = () => {
    const steps: WizardStep[] = ['validation', 'summary', 'transfer', 'confirm', 'complete'];
    const currentIndex = steps.indexOf(currentStep);
    if (currentIndex < steps.length - 1) {
      setCurrentStep(steps[currentIndex + 1]);
    }
  };

  const handlePrevious = () => {
    const steps: WizardStep[] = ['validation', 'summary', 'transfer', 'confirm', 'complete'];
    const currentIndex = steps.indexOf(currentStep);
    if (currentIndex > 0) {
      setCurrentStep(steps[currentIndex - 1]);
    }
  };

  const handleSubmit = async () => {
    setIsSubmitting(true);

    try {
      // 1. Post closing entries as journal entry drafts
      for (const entry of closingEntries) {
        // Create a draft for each closing entry
        const draft = await createDraftMutation.mutateAsync({
          companyId: fiscalYear.companyId,
          name: entry.descriptionDanish,
          documentDate: fiscalYear.endDate,
          description: entry.descriptionDanish,
          fiscalYearId: fiscalYear.id,
        });

        // Add lines to the draft
        if (entry.lines.length > 0) {
          await updateDraftMutation.mutateAsync({
            id: draft.id,
            lines: entry.lines.map((line, idx) => ({
              lineNumber: idx + 1,
              accountId: line.accountId,
              debitAmount: line.debit,
              creditAmount: line.credit,
              description: entry.descriptionDanish,
            })),
          });
        }
      }

      // 2. Close open periods if requested (local store)
      if (closeOpenPeriods) {
        for (const period of openPeriodsInYear) {
          closePeriod(period.id, 'system');
        }
      }

      // 3. Lock all periods in the year (local store)
      for (const period of yearPeriods) {
        lockPeriod(period.id, 'system');
      }

      // 4. Call backend mutation to close the fiscal year
      await closeFiscalYearMutation.mutateAsync(fiscalYear.id);

      // 5. Also update local store
      closeFiscalYear(fiscalYear.id, 'system');
      lockFiscalYear(fiscalYear.id, 'system');

      // 6. Create next fiscal year if requested
      if (createNextYear) {
        const nextStartDate = dayjs(fiscalYear.endDate).add(1, 'day');
        const nextEndDate = nextStartDate.add(12, 'month').subtract(1, 'day');
        const nextStartYear = nextStartDate.year();
        const nextEndYear = nextEndDate.year();
        const nextName = nextStartYear === nextEndYear
          ? `${nextStartYear}`
          : `${nextStartYear}/${nextEndYear}`;

        await createFiscalYearMutation.mutateAsync({
          companyId: fiscalYear.companyId,
          name: nextName,
          startDate: nextStartDate.format('YYYY-MM-DD'),
          endDate: nextEndDate.format('YYYY-MM-DD'),
        });
      }

      // 7. Move to complete step
      setCurrentStep('complete');

      onSuccess?.();
    } catch (error) {
      if (error instanceof Error) {
        message.error(`Fejl ved årsafslutning: ${error.message}`);
      }
      console.error('Failed to close fiscal year:', error);
    } finally {
      setIsSubmitting(false);
    }
  };

  const getStepNumber = (step: WizardStep): number => {
    const steps: WizardStep[] = ['validation', 'summary', 'transfer', 'confirm', 'complete'];
    return steps.indexOf(step);
  };

  const renderValidationStep = () => (
    <div>
      <Title level={5}>Validering af regnskabsår {fiscalYear.name}</Title>
      <Paragraph type="secondary">
        Før årsafslutning kontrolleres regnskabsåret for eventuelle problemer.
      </Paragraph>

      {validation.errors.length > 0 && (
        <Alert
          type="error"
          message="Fejl fundet"
          description={
            <ul style={{ margin: 0, paddingLeft: 16 }}>
              {validation.errors.map((err, idx) => (
                <li key={idx}>{err.messageDanish}</li>
              ))}
            </ul>
          }
          style={{ marginBottom: 16 }}
        />
      )}

      {validation.warnings.length > 0 && (
        <Alert
          type="warning"
          icon={<WarningOutlined />}
          message="Advarsler"
          description={
            <ul style={{ margin: 0, paddingLeft: 16 }}>
              {validation.warnings.map((warn, idx) => (
                <li key={idx}>{warn.messageDanish}</li>
              ))}
            </ul>
          }
          style={{ marginBottom: 16 }}
        />
      )}

      {summary.unreconciledCount > 0 && (
        <Alert
          type="info"
          icon={<ExclamationCircleOutlined />}
          message={`${summary.unreconciledCount} transaktioner er ikke afstemt`}
          description="Det anbefales at afstemme alle transaktioner før årsafslutning."
          style={{ marginBottom: 16 }}
        />
      )}

      {openPeriodsInYear.length > 0 && (
        <Card size="small" style={{ marginBottom: 16 }}>
          <Checkbox
            checked={closeOpenPeriods}
            onChange={(e) => setCloseOpenPeriods(e.target.checked)}
          >
            <Text>
              Luk automatisk {openPeriodsInYear.length} åbne periode(r) ved årsafslutning
            </Text>
          </Checkbox>
        </Card>
      )}

      {validation.isValid && validation.warnings.length === 0 && (
        <Alert
          type="success"
          icon={<CheckCircleOutlined />}
          message="Regnskabsåret er klar til afslutning"
          description="Ingen fejl eller advarsler fundet."
        />
      )}
    </div>
  );

  const renderSummaryStep = () => (
    <div>
      <Title level={5}>Resultatoversigt for {fiscalYear.name}</Title>

      <Row gutter={16} style={{ marginBottom: 24 }}>
        <Col span={8}>
          <Card>
            <Statistic
              title="Samlet indtægt"
              value={summary.totalRevenue}
              formatter={(val) => formatCurrency(Number(val))}
              valueStyle={{ color: '#3f8600' }}
            />
          </Card>
        </Col>
        <Col span={8}>
          <Card>
            <Statistic
              title="Samlet udgift"
              value={summary.totalExpenses}
              formatter={(val) => formatCurrency(Number(val))}
              valueStyle={{ color: '#cf1322' }}
            />
          </Card>
        </Col>
        <Col span={8}>
          <Card>
            <Statistic
              title="Årsresultat"
              value={summary.netResult}
              formatter={(val) => formatCurrency(Number(val))}
              valueStyle={{ color: summary.netResult >= 0 ? '#3f8600' : '#cf1322' }}
              prefix={summary.netResult >= 0 ? '+' : ''}
            />
          </Card>
        </Col>
      </Row>

      <Divider />

      <Text type="secondary">
        Årsresultatet på <strong>{formatCurrency(summary.netResult)}</strong> vil blive
        overført til egenkapitalen ved årsafslutning.
      </Text>
    </div>
  );

  const renderTransferStep = () => (
    <div>
      <Title level={5}>Resultatoverførsel</Title>
      <Paragraph type="secondary">
        Vælg hvilken egenkapitalkonto årsresultatet skal overføres til.
      </Paragraph>

      <Form.Item label="Egenkapitalkonto for resultatoverførsel">
        <Select
          value={resultAccountId}
          onChange={setResultAccountId}
          style={{ width: '100%' }}
          options={[
            ...equityAccounts.map((account) => ({
              value: account.id,
              label: `${account.accountNumber} - ${account.name}`,
            })),
            {
              value: DEFAULT_RESULT_ACCOUNT.id,
              label: `${DEFAULT_RESULT_ACCOUNT.accountNumber} - ${DEFAULT_RESULT_ACCOUNT.name} (Standard)`,
            },
          ]}
        />
      </Form.Item>

      <Alert
        type="info"
        message="Resultatoverførsel"
        description={
          <Text>
            Årsresultatet på <strong>{formatCurrency(summary.netResult)}</strong> vil blive
            bogført som {summary.netResult >= 0 ? 'kredit' : 'debet'} på den valgte konto.
          </Text>
        }
      />
    </div>
  );

  const renderConfirmStep = () => (
    <div>
      <Title level={5}>Bekræft årsafslutning</Title>

      <Alert
        type="warning"
        icon={<LockOutlined />}
        message="Permanent handling"
        description="Når regnskabsåret er låst, kan det ikke genåbnes. Alle perioder vil også blive låst."
        style={{ marginBottom: 16 }}
      />

      <Card title="Lukkeposter der oprettes" size="small" style={{ marginBottom: 16 }}>
        <Table
          dataSource={closingEntries.map((entry, idx) => ({ ...entry, key: idx }))}
          columns={[
            {
              title: 'Type',
              dataIndex: 'type',
              key: 'type',
              render: (type: string) => (
                <Tag>
                  {type === 'revenue-close' ? 'Luk indtægter' : 'Luk udgifter'}
                </Tag>
              ),
            },
            {
              title: 'Beskrivelse',
              dataIndex: 'descriptionDanish',
              key: 'description',
            },
            {
              title: 'Beløb',
              dataIndex: 'totalAmount',
              key: 'amount',
              align: 'right',
              render: (amount: number) => formatCurrency(amount),
            },
          ]}
          pagination={false}
          size="small"
        />
      </Card>

      <Card size="small" style={{ marginBottom: 16 }}>
        <Checkbox
          checked={createNextYear}
          onChange={(e) => setCreateNextYear(e.target.checked)}
        >
          <Text>Opret automatisk næste regnskabsår</Text>
        </Checkbox>
      </Card>

      <Alert
        type="error"
        icon={<ExclamationCircleOutlined />}
        message="Bekræft låsning"
        description={
          <Checkbox
            checked={confirmLock}
            onChange={(e) => setConfirmLock(e.target.checked)}
            style={{ marginTop: 8 }}
          >
            <Text strong>
              Jeg bekræfter at jeg vil låse regnskabsår {fiscalYear.name} permanent.
              Dette kan ikke fortrydes.
            </Text>
          </Checkbox>
        }
      />
    </div>
  );

  const renderCompleteStep = () => (
    <Result
      status="success"
      icon={<CheckCircleOutlined />}
      title="Årsafslutning gennemført"
      subTitle={`Regnskabsår ${fiscalYear.name} er nu lukket og låst.`}
      extra={[
        <Button type="primary" key="close" onClick={onClose}>
          Luk
        </Button>,
      ]}
    />
  );

  const renderStepContent = () => {
    switch (currentStep) {
      case 'validation':
        return renderValidationStep();
      case 'summary':
        return renderSummaryStep();
      case 'transfer':
        return renderTransferStep();
      case 'confirm':
        return renderConfirmStep();
      case 'complete':
        return renderCompleteStep();
      default:
        return null;
    }
  };

  const canProceed = currentStep === 'validation' ? validation.isValid : true;
  const isLastStep = currentStep === 'confirm';
  const isComplete = currentStep === 'complete';

  return (
    <Modal
      title={`Årsafslutning - ${fiscalYear.name}`}
      open={open}
      onCancel={onClose}
      width={700}
      footer={
        isComplete
          ? null
          : [
              <Button key="cancel" onClick={onClose}>
                Annuller
              </Button>,
              currentStep !== 'validation' && (
                <Button key="prev" onClick={handlePrevious}>
                  Tilbage
                </Button>
              ),
              isLastStep ? (
                <Button
                  key="submit"
                  type="primary"
                  danger
                  icon={<LockOutlined />}
                  loading={isSubmitting}
                  disabled={!confirmLock}
                  onClick={handleSubmit}
                >
                  Gennemfør årsafslutning
                </Button>
              ) : (
                <Button
                  key="next"
                  type="primary"
                  onClick={handleNext}
                  disabled={!canProceed}
                  icon={<ArrowRightOutlined />}
                >
                  Næste
                </Button>
              ),
            ].filter(Boolean)
      }
      destroyOnClose
    >
      <Steps
        current={getStepNumber(currentStep)}
        size="small"
        style={{ marginBottom: 24 }}
        items={[
          { title: 'Validering' },
          { title: 'Oversigt' },
          { title: 'Overførsel' },
          { title: 'Bekræft' },
          { title: 'Færdig' },
        ]}
      />

      {renderStepContent()}
    </Modal>
  );
}