import { useEffect, useState, type RefObject } from "react";
import { Column, Grid, InlineNotification, Modal, Select, SelectItem, TextArea, TextInput } from "@carbon/react";
import { api } from "../lib/api";
import {
  GST_CATEGORY_LABELS,
  INDIAN_STATES,
  blankClient,
  type Client,
  type GstCategory,
} from "../lib/types";
import { composeAddress, pincodeError, splitLegacyAddress } from "../lib/clientAddress";
import { clientGstinStateError } from "../lib/validators";
import { useToast } from "./ToastProvider";

interface ClientModalProps {
  open: boolean;
  /** The client to edit; null opens a blank one. */
  client: Client | null;
  onClose: () => void;
  onSaved: (client: Client) => void;
  /** Focus returns here when the modal closes. */
  launcherRef?: RefObject<HTMLElement | null>;
}

/** Fills the structured address from the legacy free-text one when a client predates the new fields. */
export function prepareForEdit(client: Client): { form: Client; splitFromLegacy: boolean } {
  const structured = client.addressLine1 || client.addressLine2 || client.city || client.pincode;
  if (structured || !client.address.trim()) return { form: client, splitFromLegacy: false };
  return { form: { ...client, ...splitLegacyAddress(client.address) }, splitFromLegacy: true };
}

export default function ClientModal({ open, client, onClose, onSaved, launcherRef }: ClientModalProps) {
  const toast = useToast();
  const [form, setForm] = useState<Client>(blankClient());
  const [split, setSplit] = useState(false);
  const [busy, setBusy] = useState(false);
  const [touched, setTouched] = useState(false);

  useEffect(() => {
    if (!open) return;
    const prepared = prepareForEdit(client ?? blankClient());
    setForm(prepared.form);
    setSplit(prepared.splitFromLegacy);
    setBusy(false);
    setTouched(false);
  }, [open, client]);

  const set = <K extends keyof Client>(key: K, value: Client[K]) => setForm((prev) => ({ ...prev, [key]: value }));

  const nameProblem = form.name.trim() ? undefined : "Client name is required";
  const gstinProblem = clientGstinStateError(form.gstin, form.stateCode);
  const pinProblem = pincodeError(form.pincode);
  const termsProblem =
    form.paymentTermsDays !== null && (form.paymentTermsDays < 0 || form.paymentTermsDays > 365)
      ? "Between 0 and 365 days"
      : undefined;
  const blocking = nameProblem ?? gstinProblem ?? pinProblem ?? termsProblem;

  const submit = async () => {
    setTouched(true);
    if (blocking) return;
    setBusy(true);
    const structured = form.addressLine1 || form.addressLine2 || form.city || form.pincode;
    const toSave: Client = {
      ...form,
      name: form.name.trim(),
      gstin: form.gstin.trim().toUpperCase(),
      address: structured
        ? composeAddress({
            line1: form.addressLine1,
            line2: form.addressLine2,
            city: form.city,
            stateCode: form.stateCode,
            pincode: form.pincode,
          })
        : form.address,
    };
    try {
      const saved = await api.saveClient(toSave);
      toast.success(toSave.id === null ? "Client added" : "Client updated", saved.name);
      onSaved(saved);
    } catch (e) {
      toast.error("Could not save client", String(e));
      setBusy(false);
    }
  };

  return (
    <Modal
      open={open}
      modalHeading={client?.id ? "Edit client" : "New client"}
      primaryButtonText={busy ? "Saving…" : "Save client"}
      secondaryButtonText="Cancel"
      primaryButtonDisabled={busy}
      onRequestClose={onClose}
      onRequestSubmit={() => void submit()}
      launcherButtonRef={launcherRef}
      size="md"
    >
      <Grid narrow>
        {split ? (
          <Column sm={4} md={8} lg={16}>
            <InlineNotification
              kind="info"
              lowContrast
              hideCloseButton
              title="Address split automatically"
              subtitle="This client has a free-text address. Check the lines below before saving."
            />
          </Column>
        ) : null}
        <Column sm={4} md={8} lg={16}>
          <TextInput
            id="cm-name"
            labelText="Client name"
            value={form.name}
            onChange={(e) => set("name", e.target.value)}
            invalid={touched && Boolean(nameProblem)}
            invalidText={nameProblem}
            data-modal-primary-focus
          />
        </Column>
        <Column sm={4} md={4} lg={8}>
          <Select
            id="cm-category"
            labelText="GST category"
            value={form.gstCategory}
            onChange={(e) => set("gstCategory", e.target.value as GstCategory)}
          >
            {Object.entries(GST_CATEGORY_LABELS).map(([value, text]) => (
              <SelectItem key={value} value={value} text={text} />
            ))}
          </Select>
        </Column>
        <Column sm={4} md={4} lg={8}>
          <TextInput
            id="cm-gstin"
            labelText="GSTIN (optional)"
            value={form.gstin}
            onChange={(e) => set("gstin", e.target.value.toUpperCase())}
            invalid={Boolean(form.gstin.trim()) && Boolean(gstinProblem)}
            invalidText={gstinProblem}
          />
        </Column>
        <Column sm={4} md={8} lg={16}>
          <TextInput
            id="cm-line1"
            labelText="Address line 1"
            value={form.addressLine1}
            onChange={(e) => set("addressLine1", e.target.value)}
          />
        </Column>
        <Column sm={4} md={8} lg={16}>
          <TextInput
            id="cm-line2"
            labelText="Address line 2"
            value={form.addressLine2}
            onChange={(e) => set("addressLine2", e.target.value)}
          />
        </Column>
        <Column sm={4} md={4} lg={5}>
          <TextInput id="cm-city" labelText="City" value={form.city} onChange={(e) => set("city", e.target.value)} />
        </Column>
        <Column sm={4} md={4} lg={7}>
          <Select
            id="cm-state"
            labelText="State (also the default place of supply)"
            value={form.stateCode}
            onChange={(e) => set("stateCode", e.target.value)}
          >
            <SelectItem value="" text="Not set" />
            {INDIAN_STATES.map((s) => (
              <SelectItem key={s.code} value={s.code} text={`${s.code} — ${s.name}`} />
            ))}
          </Select>
        </Column>
        <Column sm={4} md={4} lg={4}>
          <TextInput
            id="cm-pin"
            labelText="Pincode"
            inputMode="numeric"
            maxLength={6}
            value={form.pincode}
            onChange={(e) => set("pincode", e.target.value)}
            invalid={Boolean(pinProblem)}
            invalidText={pinProblem}
          />
        </Column>
        <Column sm={4} md={4} lg={8}>
          <TextInput
            id="cm-po"
            labelText="Default PO number (optional)"
            value={form.poNumber}
            onChange={(e) => set("poNumber", e.target.value)}
          />
        </Column>
        <Column sm={4} md={4} lg={8}>
          <TextInput
            id="cm-terms"
            labelText="Payment terms (days, blank = default)"
            inputMode="numeric"
            value={form.paymentTermsDays === null ? "" : String(form.paymentTermsDays)}
            onChange={(e) => {
              const raw = e.target.value.trim();
              set("paymentTermsDays", raw === "" ? null : Number.isFinite(Number(raw)) ? Math.trunc(Number(raw)) : null);
            }}
            invalid={Boolean(termsProblem)}
            invalidText={termsProblem}
          />
        </Column>
        <Column sm={4} md={8} lg={16}>
          <TextArea
            id="cm-notes"
            labelText="Default notes / payment terms text"
            helperText="Copied into the invoice notes when this client is picked and the notes are empty."
            rows={3}
            value={form.defaultNotes}
            onChange={(e) => set("defaultNotes", e.target.value)}
          />
        </Column>
      </Grid>
    </Modal>
  );
}