import { useEffect, useState } from "react";
import {
  Button,
  Column,
  Grid,
  Link,
  NumberInput,
  RadioButton,
  RadioButtonGroup,
  Select,
  SelectItem,
  Table,
  TableBody,
  TableCell,
  TableContainer,
  TableHead,
  TableHeader,
  TableRow,
  TextArea,
  TextInput,
  Tab,
  TabList,
  TabPanel,
  TabPanels,
  Tabs,
  Tile,
  Toggle,
} from "@carbon/react";
import { Add, Save, TrashCan } from "@carbon/icons-react";
import { confirm } from "@tauri-apps/plugin-dialog";
import { api } from "../lib/api";
import {
  INDIAN_STATES,
  type BankAccount,
  type GstRegistration,
  type Settings,
  type TaxType,
} from "../lib/types";
import { emailError, ifscError, panError, phoneError, vendorGstinError } from "../lib/validators";
import { ImagePicker } from "../components/ImagePicker";
import { LogoBranding } from "../components/LogoBranding";
import DiagnosticsPanel from "../components/DiagnosticsPanel";
import { FontOverrideTable } from "../components/FontOverrideTable";
import { useToast } from "../components/ToastProvider";
import { SETTINGS_TABS, loadSettingsTab, saveSettingsTab } from "../lib/settingsTab";
import SeriesSettings from "./SeriesSettings";

const blankBank = (): BankAccount => ({
  id: null,
  label: "",
  bankName: "",
  accountName: "",
  accountNo: "",
  branch: "",
  ifsc: "",
  isDefault: false,
});

export default function AppSettings({
  settings,
  onSaved,
}: {
  settings: Settings;
  onSaved: () => void;
}) {
  const [form, setForm] = useState<Settings>({ ...settings });
  const [diagnosticsOpen, setDiagnosticsOpen] = useState(false);
  const [banks, setBanks] = useState<BankAccount[]>([]);
  const [editing, setEditing] = useState<BankAccount | null>(null);
  const [busy, setBusy] = useState(false);
  const toast = useToast();
  // One form state for every tab and one Save button, so edits survive switching tabs.
  const [tab, setTab] = useState(loadSettingsTab);

  const selectTab = (index: number) => {
    setTab(index);
    saveSettingsTab(index);
  };

  const loadBanks = async () => {
    try {
      setBanks(await api.listBanks());
    } catch (e) {
      toast.error("Could not load bank accounts", String(e));
    }
  };

  useEffect(() => {
    void loadBanks();
  }, []);

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

  const setBank = <K extends keyof BankAccount>(key: K, value: BankAccount[K]) =>
    setEditing((prev) => (prev ? { ...prev, [key]: value } : prev));

  const registered = form.gstRegistration !== "unregistered";
  const gstinProblem = vendorGstinError(
    form.gstRegistration,
    form.vendorGstin,
    form.vendorPan,
    form.vendorStateCode,
  );

  const saveAll = async () => {
    if (gstinProblem) {
      selectTab(0);
      toast.error("Settings not saved", gstinProblem);
      return;
    }
    setBusy(true);
    try {
      await api.saveSettings(form);
      toast.success("Settings saved");
      onSaved();
    } catch (e) {
      toast.error("Could not save settings", String(e));
    } finally {
      setBusy(false);
    }
  };

  const saveBank = async () => {
    if (!editing) return;
    setBusy(true);
    try {
      const saved = await api.saveBank(editing);
      if (saved.isDefault || form.defaultBankId === null) {
        setForm((prev) => ({ ...prev, defaultBankId: saved.id }));
      }
      setEditing(null);
      await loadBanks();
      toast.success("Bank account saved", "Click Save settings to keep a changed default account.");
    } catch (e) {
      toast.error("Could not save bank account", String(e));
    } finally {
      setBusy(false);
    }
  };

  const removeBank = async (bank: BankAccount) => {
    if (bank.id === null) return;
    const ok = await confirm(`Delete bank account “${bank.bankName}”?`, {
      title: "Delete bank account",
      kind: "warning",
    });
    if (!ok) return;
    try {
      await api.deleteBank(bank.id);
      if (form.defaultBankId === bank.id) set("defaultBankId", null);
      await loadBanks();
    } catch (e) {
      toast.error("Could not delete bank account", String(e));
    }
  };

  return (
    <div className="voiced-page">
      <h1 className="voiced-page__title">Settings</h1>
      <p className="voiced-page__subtitle">Business details, branding, defaults and bank accounts.</p>

      <Tabs selectedIndex={tab} onChange={({ selectedIndex }) => selectTab(selectedIndex)}>
        <TabList aria-label="Settings sections" contained scrollIntoView>
          <Tab>Business</Tab>
          <Tab>Branding</Tab>
          <Tab>Bank &amp; payments</Tab>
          <Tab>Invoice defaults</Tab>
          <Tab>Numbering</Tab>
          <Tab>Templates &amp; export</Tab>
          <Tab>Fonts</Tab>
          <Tab>Data</Tab>
        </TabList>
        <TabPanels>
            <TabPanel>
      <section className="voiced-stack" style={{ marginBottom: "2.5rem" }}>
        <Grid narrow>
          <Column sm={4} md={8} lg={12}>
            <RadioButtonGroup
              legendText="GST registration"
              name="s-gstReg"
              orientation="horizontal"
              valueSelected={form.gstRegistration}
              onChange={(value) => {
                set("gstRegistration", value as GstRegistration);
                if (value === "unregistered") set("defaultTaxType", "none");
                else if (form.defaultTaxType === "none") set("defaultTaxType", "cgst_sgst");
              }}
            >
              <RadioButton id="s-gr-un" labelText="Unregistered" value="unregistered" />
              <RadioButton id="s-gr-reg" labelText="Regular" value="regular" />
            </RadioButtonGroup>
          </Column>
          <Column sm={4} md={8} lg={12}>
            <TextInput
              id="s-vendorName"
              labelText="Name on invoice"
              value={form.vendorName}
              onChange={(e) => set("vendorName", e.target.value)}
            />
          </Column>
          <Column sm={4} md={8} lg={12}>
            <TextArea
              id="s-vendorAddress"
              labelText="Address"
              rows={3}
              value={form.vendorAddress}
              onChange={(e) => set("vendorAddress", e.target.value)}
            />
          </Column>
          <Column sm={4} md={4} lg={6}>
            <TextInput
              id="s-vendorEmail"
              labelText="Email"
              value={form.vendorEmail}
              onChange={(e) => set("vendorEmail", e.target.value)}
              invalid={Boolean(emailError(form.vendorEmail))}
              invalidText={emailError(form.vendorEmail)}
            />
          </Column>
          <Column sm={4} md={4} lg={6}>
            <TextInput
              id="s-vendorPhone"
              labelText="Phone"
              value={form.vendorPhone}
              onChange={(e) => set("vendorPhone", e.target.value)}
              invalid={Boolean(phoneError(form.vendorPhone))}
              invalidText={phoneError(form.vendorPhone)}
            />
          </Column>
          <Column sm={4} md={4} lg={6}>
            <TextInput
              id="s-vendorPan"
              labelText="PAN"
              value={form.vendorPan}
              onChange={(e) => set("vendorPan", e.target.value.toUpperCase())}
              invalid={Boolean(panError(form.vendorPan))}
              invalidText={panError(form.vendorPan)}
            />
          </Column>
          {registered ? (
            <Column sm={4} md={4} lg={6}>
              <TextInput
                id="s-vendorGstin"
                labelText="GSTIN"
                value={form.vendorGstin}
                onChange={(e) => set("vendorGstin", e.target.value.toUpperCase())}
                invalid={Boolean(gstinProblem)}
                invalidText={gstinProblem}
              />
            </Column>
          ) : null}
          <Column sm={4} md={8} lg={12}>
            <Select
              id="s-vendorState"
              labelText="State of supply"
              value={form.vendorStateCode}
              onChange={(e) => set("vendorStateCode", e.target.value)}
            >
              {INDIAN_STATES.map((s) => (
                <SelectItem key={s.code} value={s.code} text={`${s.code} — ${s.name}`} />
              ))}
            </Select>
          </Column>
          <Column sm={4} md={4} lg={6}>
            <TextInput
              id="s-signatoryName"
              labelText="Authorised signatory name"
              value={form.signatoryName}
              onChange={(e) => set("signatoryName", e.target.value)}
            />
          </Column>
          <Column sm={4} md={4} lg={6}>
            <TextInput
              id="s-signatoryDesignation"
              labelText="Signatory designation"
              value={form.signatoryDesignation}
              onChange={(e) => set("signatoryDesignation", e.target.value)}
            />
          </Column>
          <Column sm={4} md={8} lg={8}>
            <ImagePicker
              kind="signature"
              label="Default signature"
              value={form.signaturePath}
              onChange={(path) => set("signaturePath", path)}
            />
          </Column>
        </Grid>
      </section>
            </TabPanel>
            <TabPanel>
      <section className="voiced-stack" style={{ marginBottom: "2.5rem" }}>
        <Tile>
          <LogoBranding
            idPrefix="s"
            value={form}
            onChange={(patch) => setForm((prev) => ({ ...prev, ...patch }))}
            disabled={busy}
          />
        </Tile>
      </section>
            </TabPanel>
            <TabPanel>
      <section className="voiced-stack" style={{ marginBottom: "2rem" }}>
        <div style={{ display: "flex", justifyContent: "space-between", alignItems: "center" }}>
          <h3>Bank accounts</h3>
          <Button kind="tertiary" size="sm" renderIcon={Add} onClick={() => setEditing(blankBank())}>
            Add account
          </Button>
        </div>

        {banks.length > 0 ? (
          <TableContainer>
            <Table aria-label="Bank accounts">
              <TableHead>
                <TableRow>
                  <TableHeader>Bank</TableHeader>
                  <TableHeader>Account name</TableHeader>
                  <TableHeader>Account no.</TableHeader>
                  <TableHeader>IFSC</TableHeader>
                  <TableHeader>Default</TableHeader>
                  <TableHeader>Actions</TableHeader>
                </TableRow>
              </TableHead>
              <TableBody>
                {banks.map((bank) => (
                  <TableRow key={bank.id ?? bank.bankName}>
                    <TableCell>{bank.bankName}</TableCell>
                    <TableCell>{bank.accountName}</TableCell>
                    <TableCell>{bank.accountNo}</TableCell>
                    <TableCell>{bank.ifsc}</TableCell>
                    <TableCell>{bank.isDefault ? "Yes" : "No"}</TableCell>
                    <TableCell>
                      <div className="voiced-header-action">
                        <Button kind="ghost" size="sm" onClick={() => setEditing({ ...bank })}>
                          Edit
                        </Button>
                        <Button
                          kind="ghost"
                          size="sm"
                          renderIcon={TrashCan}
                          onClick={() => removeBank(bank)}
                        >
                          Delete
                        </Button>
                      </div>
                    </TableCell>
                  </TableRow>
                ))}
              </TableBody>
            </Table>
          </TableContainer>
        ) : (
          <div className="voiced-empty">No bank accounts yet.</div>
        )}

        {editing ? (
          <div style={{ border: "1px solid var(--cds-border-subtle-01)", padding: "1rem" }}>
            <Grid narrow>
              <Column sm={4} md={4} lg={6}>
                <TextInput
                  id="b-label"
                  labelText="Label"
                  value={editing.label}
                  onChange={(e) => setBank("label", e.target.value)}
                />
              </Column>
              <Column sm={4} md={4} lg={6}>
                <TextInput
                  id="b-bankName"
                  labelText="Bank name"
                  value={editing.bankName}
                  onChange={(e) => setBank("bankName", e.target.value)}
                />
              </Column>
              <Column sm={4} md={4} lg={6}>
                <TextInput
                  id="b-accountName"
                  labelText="Account name"
                  value={editing.accountName}
                  onChange={(e) => setBank("accountName", e.target.value)}
                />
              </Column>
              <Column sm={4} md={4} lg={6}>
                <TextInput
                  id="b-accountNo"
                  labelText="Account number"
                  value={editing.accountNo}
                  onChange={(e) => setBank("accountNo", e.target.value)}
                />
              </Column>
              <Column sm={4} md={4} lg={6}>
                <TextInput
                  id="b-branch"
                  labelText="Branch"
                  value={editing.branch}
                  onChange={(e) => setBank("branch", e.target.value)}
                />
              </Column>
              <Column sm={4} md={4} lg={6}>
                <TextInput
                  id="b-ifsc"
                  labelText="IFSC"
                  value={editing.ifsc}
                  onChange={(e) => setBank("ifsc", e.target.value.toUpperCase())}
                  invalid={Boolean(ifscError(editing.ifsc))}
                  invalidText={ifscError(editing.ifsc)}
                />
              </Column>
              <Column sm={4} md={8} lg={16}>
                <Toggle
                  id="b-default"
                  labelText="Use as default account"
                  toggled={editing.isDefault}
                  onToggle={(value) => setBank("isDefault", value)}
                />
              </Column>
            </Grid>
            <div className="voiced-header-action" style={{ marginTop: "1rem" }}>
              <Button size="sm" onClick={saveBank} disabled={busy}>
                {busy ? "Saving…" : "Save account"}
              </Button>
              <Button kind="ghost" size="sm" onClick={() => setEditing(null)}>
                Cancel
              </Button>
            </div>
          </div>
        ) : null}
      </section>
            </TabPanel>
            <TabPanel>
      <section className="voiced-stack" style={{ marginBottom: "2.5rem" }}>
        <Grid narrow>
          {registered ? (
            <>
            <Column sm={4} md={4} lg={5}>
              <NumberInput
                id="s-taxRate"
                label="Default tax rate (%)"
                min={0}
                max={100}
                step={0.5}
                value={form.defaultTaxRate}
                onChange={(_e, { value }) => set("defaultTaxRate", Number(value) || 0)}
              />
            </Column>
  <Column sm={4} md={4} lg={5}>
                <TextInput
                  id="s-hsn"
                  labelText="Default HSN/SAC"
                  value={form.defaultHsnSac}
                  onChange={(e) => set("defaultHsnSac", e.target.value)}
                />
              </Column>
            </>
          ) : null}
          <Column sm={4} md={4} lg={5}>
            <NumberInput
              id="s-terms"
              label="Payment terms (days)"
              min={0}
              max={365}
              value={form.paymentTermsDays}
              onChange={(_e, { value }) => set("paymentTermsDays", Number(value) || 0)}
            />
          </Column>
          <Column sm={4} md={8} lg={6}>
            <Select
              id="s-theme"
              labelText="Theme"
              value={form.theme}
              onChange={(e) => set("theme", e.target.value)}
            >
              <SelectItem value="g10" text="Carbon light (g10)" />
              <SelectItem value="g100" text="Carbon dark (g100)" />
            </Select>
          </Column>
          {registered ? (
            <Column sm={4} md={8} lg={16}>
              <RadioButtonGroup
                legendText="Default tax treatment"
                name="s-taxType"
                valueSelected={form.defaultTaxType}
                onChange={(value) => set("defaultTaxType", value as TaxType)}
              >
                <RadioButton id="s-tt-cgst" labelText="CGST + SGST (within state)" value="cgst_sgst" />
                <RadioButton id="s-tt-igst" labelText="IGST (inter-state)" value="igst" />
                <RadioButton id="s-tt-none" labelText="No tax" value="none" />
              </RadioButtonGroup>
            </Column>
          ) : null}
        </Grid>
      </section>
            </TabPanel>
            <TabPanel>
              <SeriesSettings embedded active={tab === SETTINGS_TABS.findIndex((t) => t.id === "numbering")} />
            </TabPanel>
            <TabPanel>
              <section className="voiced-stack">
                <p>
                  The template, page size and margins are chosen next to the preview on the New invoice screen. The
                  default page setup is saved from there.
                </p>
                <p className="voiced-muted">Export mode (searchable or flattened) is chosen when you issue an invoice.</p>
              </section>
            </TabPanel>
            <TabPanel>
      <section className="voiced-stack" style={{ marginBottom: "2.5rem" }}>
        <Tile>
          <FontOverrideTable />
        </Tile>
      </section>
            </TabPanel>
            <TabPanel>
              <section className="voiced-stack">
                <p>Backup and export arrive in the next step.</p>
              </section>
            </TabPanel>
        </TabPanels>
      </Tabs>

      <Button renderIcon={Save} onClick={saveAll} disabled={busy}>
        {busy ? "Saving…" : "Save settings"}
      </Button>

      <p className="voiced-muted" style={{ marginTop: "3rem", fontSize: "0.75rem" }}>
        <Link
          href="#"
          size="sm"
          onClick={(e: { preventDefault: () => void }) => {
            e.preventDefault();
            setDiagnosticsOpen(true);
          }}
        >
          Diagnostics
        </Link>
      </p>
      <DiagnosticsPanel open={diagnosticsOpen} onClose={() => setDiagnosticsOpen(false)} />
    </div>
  );
}