import { useEffect, useState, type FormEvent } from "react";
import {
  Button,
  DateTimeField,
  DescriptionItem,
  DescriptionList,
  Dialog,
  DialogForm,
  DialogSection,
  DismissibleAlert,
  FormField,
  FormGrid,
  useUnsavedChanges,
  useUnsavedDraftGuard,
  type ApiSettings
} from "@govoplan/core-webui";
import {
  paymentApiErrorMessage,
  reconcileManualPayment,
  type PaymentRequest
} from "../../api/payments";

type ManualReconciliationDialogProps = {
  open: boolean;
  settings: ApiSettings;
  tenantId: string;
  payment: PaymentRequest | null;
  onClose: () => void;
  onReconciled: (payment: PaymentRequest) => void;
};

type ReconciliationDraft = {
  transactionReference: string;
  receivedAt: string;
  evidenceOwnerModule: string;
  evidenceKind: string;
  evidenceId: string;
  evidenceVersion: string;
  evidenceChecksum: string;
  idempotencyKey: string;
};

const FORM_ID = "payments-manual-reconciliation-form";

function localDateTime(date = new Date()): string {
  const local = new Date(date.getTime() - date.getTimezoneOffset() * 60_000);
  return local.toISOString().slice(0, 16);
}

function replayKey(): string {
  const suffix = globalThis.crypto?.randomUUID?.() ?? `${Date.now()}-${Math.random().toString(16).slice(2)}`;
  return `payments-ui-reconciliation-${suffix}`;
}

function emptyDraft(): ReconciliationDraft {
  return {
    transactionReference: "",
    receivedAt: localDateTime(),
    evidenceOwnerModule: "files",
    evidenceKind: "document",
    evidenceId: "",
    evidenceVersion: "",
    evidenceChecksum: "",
    idempotencyKey: replayKey()
  };
}

function formatAmount(amountMinor: number, currency: string): string {
  try {
    return new Intl.NumberFormat(undefined, { style: "currency", currency }).format(amountMinor / 100);
  } catch {
    return `${(amountMinor / 100).toFixed(2)} ${currency}`;
  }
}

export default function ManualReconciliationDialog({
  open,
  settings,
  tenantId,
  payment,
  onClose,
  onReconciled
}: ManualReconciliationDialogProps) {
  const [draft, setDraft] = useState<ReconciliationDraft>(emptyDraft);
  const [dirty, setDirty] = useState(false);
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState("");
  const { requestDiscard } = useUnsavedChanges();

  function reset() {
    setDraft(emptyDraft());
    setDirty(false);
    setError("");
  }

  useEffect(() => {
    if (open) reset();
  }, [open, payment?.payment_id]);

  function change<K extends keyof ReconciliationDraft>(key: K, value: ReconciliationDraft[K]) {
    setDraft((current) => ({ ...current, [key]: value }));
    setDirty(true);
  }

  async function submit(): Promise<boolean> {
    if (!payment) return false;
    if (!draft.transactionReference.trim() || !draft.evidenceOwnerModule.trim() || !draft.evidenceKind.trim() || !draft.evidenceId.trim()) {
      setError("Transaction reference and evidence owner, kind, and ID are required.");
      return false;
    }
    if (!draft.evidenceVersion.trim() && !draft.evidenceChecksum.trim()) {
      setError("Provide an evidence version or checksum so the receipt evidence is immutable.");
      return false;
    }
    if (!draft.receivedAt) {
      setError("Payment received time is required.");
      return false;
    }

    setBusy(true);
    setError("");
    try {
      const reconciled = await reconcileManualPayment(settings, payment.payment_id, {
        amount_minor: payment.amount_minor,
        currency: payment.currency,
        transaction_reference: draft.transactionReference.trim(),
        evidence_ref: {
          tenant_id: tenantId,
          owner_module: draft.evidenceOwnerModule.trim(),
          kind: draft.evidenceKind.trim(),
          evidence_id: draft.evidenceId.trim(),
          version: draft.evidenceVersion.trim() || null,
          checksum: draft.evidenceChecksum.trim() || null
        },
        idempotency_key: draft.idempotencyKey.trim(),
        received_at: new Date(draft.receivedAt).toISOString(),
        metadata: {}
      });
      setDirty(false);
      onReconciled(reconciled);
      return true;
    } catch (reason) {
      setError(paymentApiErrorMessage(reason));
      return false;
    } finally {
      setBusy(false);
    }
  }

  useUnsavedDraftGuard({
    dirty: open && dirty,
    title: "Discard the reconciliation draft?",
    message: "No payment state has changed yet. Save the exact receipt evidence before leaving or discard this draft.",
    onSave: submit,
    onDiscard: reset,
    enabled: open
  });

  function close() {
    if (busy) return;
    if (dirty) requestDiscard(onClose);
    else onClose();
  }

  function handleSubmit(event: FormEvent) {
    event.preventDefault();
    void submit();
  }

  return (
    <Dialog
      open={open}
      title="Record manual payment"
      description="Confirm a full offline receipt against immutable evidence. Payments rejects any amount or currency mismatch."
      size="wide"
      closeDisabled={busy}
      onClose={close}
      interfaceId="payments.reconciliation.manual.dialog"
      helpContextId="payments.reconciliation.manual"
      helpModuleId="payments"
      notices={error ? <DismissibleAlert tone="danger" resetKey={error}>{error}</DismissibleAlert> : null}
      footer={(
        <>
          <Button type="button" onClick={close} disabled={busy}>Cancel</Button>
          <Button type="submit" form={FORM_ID} variant="primary" disabled={busy || !payment}>
            {busy ? "Recording…" : "Record payment as paid"}
          </Button>
        </>
      )}
    >
      <DialogForm id={FORM_ID} onSubmit={handleSubmit}>
        {payment && (
          <DialogSection variant="inset" className="payments-reconciliation-warning">
            <h3 className="payments-dialog-section-title">Exact obligation</h3>
            <DescriptionList columns={2} density="compact">
              <DescriptionItem term="Payment reference">{payment.payment_reference}</DescriptionItem>
              <DescriptionItem term="Amount"><span className="payments-readonly-amount">{formatAmount(payment.amount_minor, payment.currency)}</span></DescriptionItem>
              <DescriptionItem term="Source">{payment.source.module}:{payment.source.resource_type}:{payment.source.resource_id}</DescriptionItem>
              <DescriptionItem term="Current state">Requested</DescriptionItem>
            </DescriptionList>
            <p className="payments-dialog-copy">This action appends reconciliation evidence and marks the obligation paid. It cannot be silently undone; correction or reversal requires a future governed adjustment flow.</p>
          </DialogSection>
        )}

        <DialogSection variant="separated">
          <h3 className="payments-dialog-section-title">Receipt</h3>
          <FormGrid columns={2}>
            <FormField label="External transaction reference" helpContextId="payments.reconciliation.field.transaction-reference" helpModuleId="payments">
              <input required maxLength={255} value={draft.transactionReference} onChange={(event) => change("transactionReference", event.target.value)} />
            </FormField>
            <FormField label="Payment received date and time">
              <DateTimeField required value={draft.receivedAt} onChange={(value) => change("receivedAt", value)} aria-label="Payment received date and time" />
            </FormField>
          </FormGrid>
        </DialogSection>

        <DialogSection variant="separated">
          <h3 className="payments-dialog-section-title">Immutable evidence</h3>
          <p className="payments-dialog-section-copy">Payments stores only this typed reference. The evidence bytes and retention remain with the owning module.</p>
          <FormGrid columns={2}>
            <FormField label="Evidence owner module">
              <input required maxLength={120} value={draft.evidenceOwnerModule} onChange={(event) => change("evidenceOwnerModule", event.target.value)} />
            </FormField>
            <FormField label="Evidence kind">
              <input required maxLength={120} value={draft.evidenceKind} onChange={(event) => change("evidenceKind", event.target.value)} />
            </FormField>
            <FormField label="Evidence ID">
              <input required maxLength={255} value={draft.evidenceId} onChange={(event) => change("evidenceId", event.target.value)} />
            </FormField>
            <FormField label="Evidence version" help="Provide a version or checksum; both may be supplied.">
              <input maxLength={255} value={draft.evidenceVersion} onChange={(event) => change("evidenceVersion", event.target.value)} />
            </FormField>
            <FormField label="Evidence checksum" help="Provide a checksum or version; both may be supplied.">
              <input maxLength={255} value={draft.evidenceChecksum} onChange={(event) => change("evidenceChecksum", event.target.value)} />
            </FormField>
          </FormGrid>
        </DialogSection>

        <DialogSection variant="inset">
          <h3 className="payments-dialog-section-title">Replay protection</h3>
          <p className="payments-dialog-section-copy">Retry this key only for this exact payment and evidence. A changed replay conflicts instead of creating ambiguous settlement evidence.</p>
          <FormField label="Idempotency key" helpContextId="payments.reconciliation.field.replay-key" helpModuleId="payments">
            <input required maxLength={255} value={draft.idempotencyKey} onChange={(event) => change("idempotencyKey", event.target.value)} />
          </FormField>
        </DialogSection>
      </DialogForm>
    </Dialog>
  );
}