import { useCallback, useEffect, useMemo, useState } from "react";
import {
  Button,
  ComboBox,
  FileUploaderButton,
  InlineLoading,
  InlineNotification,
  PasswordInput,
  RadioButton,
  RadioButtonGroup,
  TextArea,
  TextInput,
  Tag,
  Tile,
  Toggle,
} from "@carbon/react";
import { Save } from "@carbon/icons-react";
import { api } from "../lib/api";
import type { ErpnextConfig, ErpnextConfigInput, ErpnextConnectionTest, ErpnextOptionItem, ErpnextOptions } from "../lib/erpnext";
import {
  OPTION_LIST_LABELS,
  UOM_UNITS,
  connectionProblems,
  emptyOptions,
  hasProblems,
  mirrorSupported,
  optionErrors,
  optionText,
  sortWarnings,
  toInput,
  validateConfigForm,
  versionsLine,
  warningSeverity,
  withStoredValue,
  type FormProblems,
} from "../lib/erpnextUi";
import { useToast } from "./ToastProvider";

const SEVERITY_TITLE = { error: "Needs fixing", warning: "Warning", info: "Note" } as const;

interface PickProps {
  id: string;
  label: string;
  value: string;
  onChange: (value: string) => void;
  /** The loaded list; an empty list means "not loaded", and the field takes typed text instead. */
  items: ErpnextOptionItem[];
  /** Why this list is empty although the lists were loaded (a load error for this list). */
  error?: string;
  /** The control is switched off, with the reason shown under it. */
  disabledReason?: string;
  helper?: string;
}

/** A searchable dropdown over a live list, or a text box while the list has not been loaded. */
function PickField({ id, label, value, onChange, items, error, disabledReason, helper }: PickProps) {
  const options = useMemo(() => withStoredValue(items, value), [items, value]);
  const note = disabledReason ?? error ?? helper;
  if (items.length === 0 || disabledReason) {
    return (
      <TextInput
        id={id}
        labelText={label}
        value={value}
        disabled={Boolean(disabledReason)}
        invalid={Boolean(error) && !disabledReason}
        invalidText={error}
        helperText={error ? undefined : note}
        onChange={(e) => onChange(e.target.value)}
      />
    );
  }
  return (
    <ComboBox
      id={id}
      titleText={label}
      items={options}
      itemToString={(i: ErpnextOptionItem | null) => (i ? optionText(i) : "")}
      selectedItem={options.find((o) => o.name === value) ?? null}
      onChange={({ selectedItem }: { selectedItem?: ErpnextOptionItem | null }) => onChange(selectedItem?.name ?? "")}
      shouldFilterItem={({ item, inputValue }: { item: ErpnextOptionItem; inputValue: string | null }) =>
        !inputValue || optionText(item).toLowerCase().includes(inputValue.toLowerCase())
      }
      helperText={helper}
      placeholder="Search or choose"
    />
  );
}

function Section({ title, children, note }: { title: string; children: React.ReactNode; note?: string }) {
  return (
    <section className="voiced-erp__section" aria-label={title}>
      <h3>{title}</h3>
      {note ? <p className="voiced-muted">{note}</p> : null}
      <div className="voiced-erp__fields">{children}</div>
    </section>
  );
}

/** Settings, Integrations, ERPNext. It has its own Save: the page-level Save settings button does not cover it. */
export default function ErpnextSettingsPanel({ active }: { active: boolean }) {
  const toast = useToast();
  const [saved, setSaved] = useState<ErpnextConfig | null>(null);
  const [form, setForm] = useState<ErpnextConfigInput | null>(null);
  const [loadError, setLoadError] = useState<string | null>(null);
  const [replacing, setReplacing] = useState(false);
  const [test, setTest] = useState<ErpnextConnectionTest | null>(null);
  /** A test result from this session that is not saved yet. */
  const [testUnsaved, setTestUnsaved] = useState(false);
  const [testError, setTestError] = useState<string | null>(null);
  const [testing, setTesting] = useState(false);
  const [options, setOptions] = useState<ErpnextOptions | null>(null);
  const [loadingOptions, setLoadingOptions] = useState(false);
  const [saving, setSaving] = useState(false);
  const [showProblems, setShowProblems] = useState(false);
  const [saveError, setSaveError] = useState<string | null>(null);

  const load = useCallback(async () => {
    try {
      const cfg = await api.erpnextGetConfig();
      setSaved(cfg);
      setForm(toInput(cfg));
      setTest(cfg.lastDetectResult);
      setTestUnsaved(false);
      setLoadError(null);
    } catch (e) {
      setLoadError(String(e));
    }
  }, []);

  useEffect(() => {
    if (active && form === null) void load();
    // Reload only on first show; edits must survive switching tabs.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [active]);

  if (loadError) {
    return <InlineNotification kind="error" lowContrast hideCloseButton title="Could not load the ERPNext settings" subtitle={loadError} />;
  }
  if (!form || !saved) return <InlineLoading description="Loading ERPNext settings" />;

  const set = <K extends keyof ErpnextConfigInput>(key: K, value: ErpnextConfigInput[K]) => setForm((f) => (f ? { ...f, [key]: value } : f));
  const secretStored = saved.apiSecretSet;
  const secretShown = secretStored && !replacing && !form.clearSecret;
  const problems: FormProblems = showProblems ? validateConfigForm(form, secretStored, test) : {};
  const connProblems = connectionProblems(form, secretStored);
  const canConnect = !hasProblems(connProblems);
  const optErrors = optionErrors(options);
  const opts = options ?? emptyOptions();
  const noCompany = !form.company.trim();
  const companyReason = noCompany ? "Pick a company first." : undefined;
  const seriesMode = form.namingMode === "series";
  const mirrorOk = mirrorSupported(test);

  const loadOptions = async (values: ErpnextConfigInput) => {
    setLoadingOptions(true);
    try {
      setOptions(await api.erpnextLoadOptions(values));
    } catch (e) {
      setOptions(null);
      toast.error("Could not load the ERPNext lists", String(e));
    } finally {
      setLoadingOptions(false);
    }
  };

  const runTest = async () => {
    setShowProblems(true);
    if (!canConnect) return;
    setTesting(true);
    setTestError(null);
    try {
      const result = await api.erpnextTestConnection(form);
      setTest(result);
      setTestUnsaved(true);
      let next = form;
      // A site that keeps no posted name cannot mirror the Voiced number.
      if (!result.features.v2Naming && form.namingMode === "mirror") {
        next = { ...form, namingMode: "series" };
        setForm(next);
      }
      await loadOptions(next);
    } catch (e) {
      setTestError(String(e));
    } finally {
      setTesting(false);
    }
  };

  const changeCompany = (company: string) => {
    const next = { ...form, company };
    setForm(next);
    // Accounts, addresses and cost centers belong to the company, so the lists are reloaded for it.
    if (options && canConnect) void loadOptions(next);
  };

  const save = async () => {
    setShowProblems(true);
    setSaveError(null);
    if (hasProblems(validateConfigForm(form, secretStored, test))) return;
    setSaving(true);
    try {
      const cfg = await api.erpnextSaveConfig({ ...form, ...(testUnsaved && test ? { lastDetectResult: test } : {}) });
      setSaved(cfg);
      setForm(toInput(cfg));
      setReplacing(false);
      setTest(cfg.lastDetectResult ?? test);
      setTestUnsaved(false);
      setShowProblems(false);
      toast.success("ERPNext settings saved");
    } catch (e) {
      const text = String(e);
      setSaveError(text);
      toast.error("Could not save the ERPNext settings", text);
    } finally {
      setSaving(false);
    }
  };

  const readPem = async (file: File | undefined) => {
    if (!file) return;
    try {
      set("extraCaPem", (await file.text()).trim());
    } catch (e) {
      toast.error("Could not read the certificate file", String(e));
    }
  };

  const secretInvalid = problems.apiSecret ?? (saveError && /secret again/i.test(saveError) ? saveError : undefined);

  return (
    <div className="voiced-stack voiced-erp">
      <div>
        <h2 className="voiced-detail__h2">ERPNext</h2>
        <p>
          Send issued invoices and payments to your ERPNext site as Sales Invoices. Everything is sent from this computer; ERPNext is never
          needed to issue an invoice.
        </p>
        <p className="voiced-muted">
          Create a dedicated ERPNext user for Voiced with only these permissions: create and submit Sales Invoice, read on the master data
          (Customer, Item, Address, Account, Company), and write on File. Use that user&rsquo;s API key and secret below. An address must be
          https://; plain http is only allowed for localhost, 127.0.0.1, *.localhost and *.test hosts.
        </p>
      </div>

      <Section title="Connection">
        <TextInput
          id="erp-baseUrl"
          labelText="Site address"
          placeholder="https://erp.example.com"
          value={form.baseUrl}
          invalid={Boolean(problems.baseUrl)}
          invalidText={problems.baseUrl}
          onChange={(e) => set("baseUrl", e.target.value)}
        />
        <TextInput
          id="erp-apiKey"
          labelText="API key"
          autoComplete="off"
          value={form.apiKey}
          invalid={Boolean(problems.apiKey)}
          invalidText={problems.apiKey}
          onChange={(e) => set("apiKey", e.target.value)}
        />
        {secretShown ? (
          <div className="voiced-erp__secret">
            <p className="voiced-erp__label" id="erp-secret-label">
              API secret
            </p>
            <p aria-labelledby="erp-secret-label">
              <Tag type="green" size="sm">
                set
              </Tag>{" "}
              <span className="voiced-muted">The secret is stored on this computer and is never shown again.</span>
            </p>
            <div className="voiced-header-action">
              <Button kind="tertiary" size="sm" onClick={() => setReplacing(true)}>
                Replace
              </Button>
              <Button kind="ghost" size="sm" onClick={() => set("clearSecret", true)}>
                Clear
              </Button>
            </div>
          </div>
        ) : (
          <div>
            <PasswordInput
              id="erp-apiSecret"
              labelText="API secret"
              autoComplete="new-password"
              value={form.apiSecret}
              invalid={Boolean(secretInvalid)}
              invalidText={secretInvalid}
              helperText={form.clearSecret ? "The stored secret is removed when you save, unless you type a new one." : undefined}
              onChange={(e) => set("apiSecret", e.target.value)}
            />
            {secretStored ? (
              <Button
                kind="ghost"
                size="sm"
                onClick={() => {
                  setReplacing(false);
                  setForm((f) => (f ? { ...f, apiSecret: "", clearSecret: false } : f));
                }}
              >
                Keep the stored secret
              </Button>
            ) : null}
          </div>
        )}
        <div>
          <TextArea
            id="erp-extraCa"
            labelText="Extra CA certificate (optional, PEM)"
            helperText="Only for a self-hosted site whose certificate is not trusted by this computer."
            rows={3}
            value={form.extraCaPem}
            onChange={(e) => set("extraCaPem", e.target.value)}
          />
          <FileUploaderButton
            labelText="Load from file…"
            buttonKind="ghost"
            size="sm"
            accept={[".pem", ".crt", ".cer"]}
            disableLabelChanges
            onChange={(e: React.ChangeEvent<HTMLInputElement>) => {
              const file = e.target.files?.[0];
              e.target.value = "";
              void readPem(file);
            }}
          />
        </div>
        <div className="voiced-header-action">
          <Button kind="secondary" size="md" onClick={() => void runTest()} disabled={testing || loadingOptions}>
            {testing ? "Testing…" : "Test connection"}
          </Button>
          {testing || loadingOptions ? <InlineLoading description={testing ? "Contacting ERPNext" : "Loading lists"} /> : null}
          {!canConnect && showProblems ? <span className="voiced-muted">Fix the address, key and secret first.</span> : null}
        </div>
        {testError ? <InlineNotification kind="error" lowContrast hideCloseButton title="Connection failed" subtitle={testError} /> : null}
        {test ? (
          <Tile className="voiced-erp__result" aria-label="Connection test result">
            <p>
              <strong>Connected as {test.user || "an unknown user"}</strong>{" "}
              <Tag type={test.indiaCompliance ? "green" : "warm-gray"} size="sm">
                {test.indiaCompliance ? "India Compliance detected" : "India Compliance not detected"}
              </Tag>
            </p>
            <p className="voiced-muted">{versionsLine(test)}</p>
            {testUnsaved ? (
              <InlineNotification
                kind="info"
                lowContrast
                hideCloseButton
                title="Save to keep this result"
                subtitle="Sending invoices needs a saved connection test."
              />
            ) : (
              <p className="voiced-muted">Last saved test result.</p>
            )}
            {sortWarnings(test.warnings).map((w, i) => {
              const severity = warningSeverity(w.code);
              return (
                <InlineNotification
                  key={`${w.code}-${i}`}
                  kind={severity}
                  lowContrast
                  hideCloseButton
                  title={SEVERITY_TITLE[severity]}
                  subtitle={w.message}
                />
              );
            })}
            {test.warnings.length === 0 ? <p className="voiced-muted">No problems found with the current settings.</p> : null}
            <p className="voiced-muted">Test again after changing the mappings below to refresh these warnings.</p>
          </Tile>
        ) : null}
      </Section>

      <Section
        title="Company and accounts"
        note={options ? "Choose from what your ERPNext site has." : "Run Test connection to choose from your site's lists; until then, type the exact names."}
      >
        {options && options.errors.length > 0 ? (
          <InlineNotification
            kind="warning"
            lowContrast
            hideCloseButton
            title="Some lists could not be loaded"
            subtitle={options.errors.map((e) => `${OPTION_LIST_LABELS[e.list] ?? e.list}: ${e.message}`).join(" ")}
          />
        ) : null}
        <PickField
          id="erp-company"
          label="Company"
          value={form.company}
          onChange={changeCompany}
          items={opts.companies}
          error={optErrors.get("companies")}
        />
        <PickField
          id="erp-companyAddress"
          label="Company address"
          value={form.companyAddress}
          onChange={(v) => set("companyAddress", v)}
          items={opts.companyAddresses}
          error={optErrors.get("companyAddresses")}
          disabledReason={companyReason}
          helper="Required by India Compliance on every invoice."
        />
        <PickField
          id="erp-incomeAccount"
          label="Income account"
          value={form.incomeAccount}
          onChange={(v) => set("incomeAccount", v)}
          items={opts.incomeAccounts}
          error={optErrors.get("incomeAccounts")}
          disabledReason={companyReason}
        />
        <PickField
          id="erp-costCenter"
          label="Cost center"
          value={form.costCenter}
          onChange={(v) => set("costCenter", v)}
          items={opts.costCenters}
          error={optErrors.get("costCenters")}
          disabledReason={companyReason}
        />
        {(
          [
            ["cgstAccount", "CGST account"],
            ["sgstAccount", "SGST account"],
            ["utgstAccount", "UTGST account"],
            ["igstAccount", "IGST account"],
          ] as const
        ).map(([key, label]) => (
          <PickField
            key={key}
            id={`erp-${key}`}
            label={label}
            value={form[key]}
            onChange={(v) => set(key, v)}
            items={opts.taxAccounts}
            error={optErrors.get("taxAccounts")}
            disabledReason={companyReason}
            helper={key === "utgstAccount" ? "Only needed when the supplier is in a union territory without a legislature." : "Must be the account set in GST Settings."}
          />
        ))}
        <TextInput
          id="erp-paymentBank"
          labelText="Payment bank account"
          helperText="The bank or cash account that receives payments, e.g. HDFC Bank - AC. Needed to send payments."
          value={form.paymentBankAccount}
          onChange={(e) => set("paymentBankAccount", e.target.value)}
        />
        <TextInput
          id="erp-tdsAccount"
          labelText="TDS account"
          helperText="The account that holds tax deducted by clients. Needed only for payments with TDS."
          value={form.tdsAccount}
          onChange={(e) => set("tdsAccount", e.target.value)}
        />
      </Section>

      <Section title="Customers and items">
        <TextInput
          id="erp-defaultItem"
          labelText="Default item code (optional)"
          helperText="Used for invoice lines without an item code of their own; a line with none is sent as a description-only row."
          value={form.defaultItemCode}
          onChange={(e) => set("defaultItemCode", e.target.value)}
        />
        <PickField
          id="erp-customerGroup"
          label="Customer group for new customers"
          value={form.customerGroup}
          onChange={(v) => set("customerGroup", v)}
          items={opts.customerGroups}
          error={optErrors.get("customerGroups")}
        />
        <PickField
          id="erp-territory"
          label="Territory for new customers"
          value={form.territory}
          onChange={(v) => set("territory", v)}
          items={opts.territories}
          error={optErrors.get("territories")}
        />
        <PickField
          id="erp-priceList"
          label="Selling price list"
          value={form.sellingPriceList}
          onChange={(v) => set("sellingPriceList", v)}
          items={opts.priceLists}
          error={optErrors.get("priceLists")}
        />
        <fieldset className="voiced-erp__uoms">
          <legend>Units of measure</legend>
          <p className="voiced-muted">The ERPNext unit used for each Voiced unit. Whole-number units such as Nos reject fractional quantities.</p>
          {UOM_UNITS.map((unit) => (
            <PickField
              key={unit}
              id={`erp-uom-${unit}`}
              label={`Voiced ${unit}`}
              value={form.uomMap[unit] ?? ""}
              onChange={(v) => setForm((f) => (f ? { ...f, uomMap: { ...f.uomMap, [unit]: v } } : f))}
              items={opts.uoms}
              error={optErrors.get("uoms")}
            />
          ))}
        </fieldset>
      </Section>

      <Section title="Invoice numbers">
        <RadioButtonGroup
          legendText="Numbering in ERPNext"
          name="erp-namingMode"
          orientation="vertical"
          valueSelected={form.namingMode}
          onChange={(value) => set("namingMode", value === "series" ? "series" : "mirror")}
        >
          <RadioButton
            id="erp-nm-mirror"
            value="mirror"
            labelText="Mirror the Voiced number (recommended)"
            disabled={!mirrorOk}
          />
          <RadioButton id="erp-nm-series" value="series" labelText="Use an ERPNext naming series" />
        </RadioButtonGroup>
        <p className="voiced-muted">
          {mirrorOk
            ? "Mirror keeps the number printed on the PDF as the ERPNext invoice name, so GST returns match. Needs Frappe 15.73 or later."
            : "Mirror is unavailable: this ERPNext version replaces a posted invoice number. The Voiced number is stored in the remarks instead."}
        </p>
        {problems.namingMode ? <p className="voiced-erp__error">{problems.namingMode}</p> : null}
        <PickField
          id="erp-namingSeries"
          label="Naming series"
          value={form.namingSeries}
          onChange={(v) => set("namingSeries", v)}
          items={opts.namingSeries}
          error={problems.namingSeries ?? optErrors.get("namingSeries")}
          disabledReason={seriesMode ? undefined : "Only used with an ERPNext naming series."}
        />
      </Section>

      <Section title="Sending">
        <Toggle
          id="erp-submit"
          labelText="Submit invoices when sending"
          labelA="Off: drafts for review"
          labelB="On: submitted"
          toggled={form.submitOnPush}
          onToggle={(v) => set("submitOnPush", v)}
        />
        <Toggle
          id="erp-attach"
          labelText="Attach the PDF"
          labelA="Off"
          labelB="On"
          toggled={form.attachPdf}
          onToggle={(v) => set("attachPdf", v)}
        />
        <Toggle
          id="erp-auto"
          labelText="Send automatically when an invoice is issued"
          labelA="Off"
          labelB="On"
          toggled={form.autoPushOnIssue}
          onToggle={(v) => set("autoPushOnIssue", v)}
        />
        <Toggle
          id="erp-customers"
          labelText="Create customers that are missing in ERPNext"
          labelA="Off"
          labelB="On"
          toggled={form.createMissingCustomers}
          onToggle={(v) => set("createMissingCustomers", v)}
        />
      </Section>

      {saveError && !secretInvalid ? <InlineNotification kind="error" lowContrast hideCloseButton title="Not saved" subtitle={saveError} /> : null}
      <div>
        <Button renderIcon={Save} onClick={() => void save()} disabled={saving}>
          {saving ? "Saving…" : "Save ERPNext settings"}
        </Button>
        <p className="voiced-muted">This tab has its own Save button; Save settings at the bottom of the page does not cover it.</p>
      </div>
    </div>
  );
}