import { readFileSync } from "node:fs";
import path from "node:path";
import { deflateSync } from "node:zlib";
import { computeTotals } from "../../lib/invoice";
import { amountInWords } from "../../lib/numberToWords";
import type { BankAccount, Invoice, InvoiceItem, Settings, TaxType } from "../../lib/types";
import { buildRenderModel, type LogoInput, type RenderModel } from "../model/build";
import { DEFAULT_PREFS, type RenderPrefsV1 } from "../model/prefs";
import { renderInvoicePdf, type RenderInvoiceResult } from "../render/invoice";
import { parsePdfText, type RenderedPdf } from "../testing/pdfText";
import { setupPdfTest } from "../testing/setup";

/** Fixtures and helpers shared by the template harness and the sample renderer. */

export type LogoKind = "none" | "real" | "wide" | "square";

export interface FixtureSpec {
  name: string;
  vendor?: Partial<Settings>;
  invoice?: Partial<Invoice>;
  /** An item list, or a count of generated one-line items. */
  items?: InvoiceItem[] | number;
  logo?: LogoKind;
  signature?: boolean;
  /** Tax invoice with a registered supplier (default true; false gives the plain invoice). */
  registered?: boolean;
}

export const FIXTURE_GSTIN = "29AAAAA0000A1Z5";
const FIXTURE_CLIENT_GSTIN = "29ABCDE1234F1Z5";

const baseVendor: Settings = {
  vendorName: "Test Vendor",
  vendorAddress: "1 Test Road, Bangalore - 560001",
  vendorEmail: "vendor@example.com",
  vendorPhone: "9000000000",
  vendorPan: "ABCDE1234F",
  vendorGstin: "",
  vendorStateCode: "29",
  logoPath: null,
  signaturePath: null,
  defaultBankId: 1,
  defaultTaxRate: 18,
  defaultTaxType: "cgst_sgst",
  paymentTermsDays: 30,
  currency: "INR",
  onboarded: true,
  theme: "g10",
  gstRegistration: "unregistered",
  defaultHsnSac: "",
  signatoryName: "",
  signatoryDesignation: "",
  renderPrefs: "",
};

export const FIXTURE_BANK: BankAccount = {
  id: 1,
  label: "Primary",
  bankName: "State Bank of India",
  accountName: "Test Vendor",
  accountNo: "000000000000",
  branch: "000001",
  ifsc: "TEST0000001",
  isDefault: true,
};

export const makeItems = (n: number, hsn: boolean): InvoiceItem[] =>
  Array.from({ length: n }, (_, i) => ({
    id: i + 1,
    description: `Voice-over session ${i + 1} - narration for module ${i + 1}`,
    mode: i % 2 === 0 ? "rate" : "fixed",
    rate: 1200,
    unit: "hour",
    quantity: 1 + (i % 3),
    amount: 2500 + i * 10,
    sortOrder: i,
    ...(hsn ? { hsnSac: "998397" } : {}),
  }));

// --- tiny PNG writer: logos for the fixtures without a native image library or a binary fixture ----

const crcTable = Array.from({ length: 256 }, (_, n) => {
  let c = n;
  for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
  return c >>> 0;
});
const crc32 = (buf: Buffer) => {
  let c = 0xffffffff;
  for (const b of buf) c = crcTable[(c ^ b) & 0xff] ^ (c >>> 8);
  return (c ^ 0xffffffff) >>> 0;
};
const chunk = (type: string, data: Buffer) => {
  const len = Buffer.alloc(4);
  len.writeUInt32BE(data.length);
  const body = Buffer.concat([Buffer.from(type, "latin1"), data]);
  const crc = Buffer.alloc(4);
  crc.writeUInt32BE(crc32(body));
  return Buffer.concat([len, body, crc]);
};

/** A w x h RGBA PNG: a navy block with a light stripe, so a wrongly stretched logo is visible. */
export function solidPng(w: number, h: number): Buffer {
  const row = Buffer.alloc(1 + w * 4);
  const raw = Buffer.alloc(row.length * h);
  for (let y = 0; y < h; y++) {
    raw[y * row.length] = 0;
    for (let x = 0; x < w; x++) {
      const stripe = Math.abs(x - y * (w / h)) < h * 0.12;
      const o = y * row.length + 1 + x * 4;
      raw[o] = stripe ? 120 : 24;
      raw[o + 1] = stripe ? 160 : 52;
      raw[o + 2] = stripe ? 240 : 120;
      raw[o + 3] = 255;
    }
  }
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(w, 0);
  ihdr.writeUInt32BE(h, 4);
  ihdr[8] = 8;
  ihdr[9] = 6;
  return Buffer.concat([
    Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
    chunk("IHDR", ihdr),
    chunk("IDAT", deflateSync(raw)),
    chunk("IEND", Buffer.alloc(0)),
  ]);
}

const dataUri = (png: Buffer) => `data:image/png;base64,${png.toString("base64")}`;

const cache = new Map<string, LogoInput>();
export function fixtureLogo(kind: LogoKind): LogoInput | null {
  if (kind === "none") return null;
  let hit = cache.get(kind);
  if (!hit) {
    if (kind === "real") {
      // 2172 x 724: the untrimmed Test Vendor logo, a 3:1 aspect.
      const png = readFileSync(path.resolve(process.cwd(), "public/brand/sample-wordmark-logo.png"));
      hit = { dataUri: dataUri(png), width: png.readUInt32BE(16), height: png.readUInt32BE(20) };
    } else if (kind === "wide") {
      // The trimmed Test Vendor ink box is 4.6:1.
      hit = { dataUri: dataUri(solidPng(460, 100)), width: 460, height: 100 };
    } else {
      hit = { dataUri: dataUri(solidPng(120, 120)), width: 120, height: 120 };
    }
    cache.set(kind, hit);
  }
  return hit;
}

let signature: string | null = null;
const signatureUri = () => (signature ??= dataUri(solidPng(320, 90)));

export interface BuiltFixture {
  spec: FixtureSpec;
  model: RenderModel;
  invoice: Invoice;
}

/** A full `Invoice` read model (totals derived the way Rust does) pushed through buildRenderModel. */
export function buildFixture(spec: FixtureSpec): BuiltFixture {
  const registered = spec.registered !== false;
  const taxInvoice = registered;
  const items = Array.isArray(spec.items) ? spec.items : makeItems(spec.items ?? 3, taxInvoice);
  const taxType: TaxType = spec.invoice?.taxType ?? (taxInvoice ? "cgst_sgst" : "none");
  const taxRate = spec.invoice?.taxRate ?? (taxInvoice ? 18 : 0);
  const discount = spec.invoice?.discount ?? 0;
  const totals = computeTotals(items, discount, taxType, taxRate);

  const vendor: Settings = {
    ...baseVendor,
    ...(registered
      ? { vendorGstin: FIXTURE_GSTIN, gstRegistration: "regular" as const, signatoryName: "Test Vendor", signatoryDesignation: "Proprietor" }
      : // A stale GSTIN left in the settings of an unregistered supplier must never print.
        { vendorGstin: "27ZZZZZ9999Z1Z9", gstRegistration: "unregistered" as const }),
    ...spec.vendor,
  };
  const pos = vendor.vendorStateCode;
  const invoice: Invoice = {
    id: 1,
    number: "INV/2026-001",
    seriesId: 1,
    invoiceDate: "2026-09-15",
    dueDate: "2026-10-15",
    clientId: null,
    clientName: "Acme Learning Pvt Ltd",
    clientAddress: "42 MG Road\nBangalore 560001",
    clientGstin: FIXTURE_CLIENT_GSTIN,
    poNumber: "",
    placeOfSupplyStateCode: taxInvoice ? pos : "",
    subtotal: totals.subtotal,
    discount: totals.discount,
    taxType,
    taxRate,
    cgstAmount: totals.cgst,
    sgstAmount: totals.sgst,
    igstAmount: totals.igst,
    total: totals.total,
    amountInWords: amountInWords(totals.total),
    bankAccountId: 1,
    bankSnapshot: "",
    signaturePath: null,
    notes: "",
    status: "issued",
    createdAt: "2026-09-15T00:00:00Z",
    updatedAt: "2026-09-15T00:00:00Z",
    docType: taxInvoice ? "tax_invoice" : "invoice",
    reverseCharge: false,
    vendorSnapshot: "",
    snapshotOrigin: "",
    cancelledAt: null,
    cancelReason: "",
    archivedPdfSha256: null,
    renderPrefs: "",
    items,
    ...spec.invoice,
  };
  const model = buildRenderModel({
    invoice,
    vendor,
    bank: FIXTURE_BANK,
    logo: fixtureLogo(spec.logo ?? "real"),
    signatureDataUri: spec.signature ? signatureUri() : null,
    appVersion: "0.1.0",
  });
  return { spec, model, invoice };
}

const LONG_ADDRESS =
  "Unit 4, Third Floor, The Grand Heritage Business Centre, Plot 1187-B, Old Airport Road Extension, Opposite the Municipal Corporation Ward Office, Domlur Second Stage, Bengaluru Urban District, Karnataka State, India - 560071; Registered office: Level 12, Tower C, Global Technology Park, Outer Ring Road, Marathahalli, Bengaluru - 560103";

/** The fixture matrix of the template harness. Every name is unique; the file name of a sample uses it. */
export const FIXTURES: FixtureSpec[] = [
  { name: "minimal", items: 1, logo: "none" },
  { name: "long-address", vendor: { vendorAddress: LONG_ADDRESS }, items: 4 },
  {
    name: "id-tokens",
    vendor: {
      vendorEmail: "Sample.longsurname.voiceover.studio.bangalore@examplestudios-india.co.in",
      vendorPhone: "+91 97382 84459 / +91 80 4123 9988 (studio)",
      vendorName: "Venkatachalam Longsurname Ramasubramanian Voice Studios Pvt",
    },
    invoice: { clientName: "https://www.extremely-long-client-website-address.example.com/projects/2026/voice", clientGstin: "29ABCDE1234F1Z5", poNumber: "PO/2026/BANGALORE/0042/REV-3/LONG-REFERENCE" },
    items: 3,
  },
  { name: "rows-60", items: 60, invoice: { notes: "Payment due within 30 days.\nLate payments attract 2% monthly interest." }, signature: true },
  {
    name: "multiline",
    items: [
      { description: "Voice-over for the onboarding course\nModule 1 - introduction\nModule 2 - safety basics\nIncludes two rounds of revisions", mode: "rate", rate: 1500, unit: "hour", quantity: 3, amount: 0, sortOrder: 0, hsnSac: "998397" },
      { description: "Studio hire", mode: "fixed", rate: 0, unit: "unit", quantity: 1, amount: 8000, sortOrder: 1, hsnSac: "997212" },
      { description: "Audio editing and mastering of all deliverables, including noise reduction, levelling, and export to the three formats requested by the client in the brief of August", mode: "rate", rate: 400, unit: "minute", quantity: 25, amount: 0, sortOrder: 2, hsnSac: "998397" },
    ],
  },
  {
    name: "long-notes",
    items: 30,
    invoice: { notes: Array.from({ length: 18 }, (_, i) => `Note ${i + 1}: payment is due within thirty days of the invoice date; late payments attract interest at two percent per month.`).join("\n") },
  },
  { name: "igst", invoice: { taxType: "igst", placeOfSupplyStateCode: "27", discount: 500 }, items: 5 },
  { name: "cgst-sgst", items: 5, invoice: { poNumber: "PO-2026-0042", notes: "Thank you for your business." } },
  { name: "utgst", vendor: { vendorStateCode: "04", vendorGstin: "04AAAAA0000A1Z5" }, invoice: { placeOfSupplyStateCode: "04" }, items: 4 },
  { name: "unregistered", registered: false, items: 3 },
  { name: "cancelled", invoice: { status: "cancelled" }, items: 4, signature: true },
  { name: "logo-none", logo: "none", items: 3 },
  { name: "logo-wide", logo: "wide", items: 3 },
  { name: "logo-square", logo: "square", items: 3 },
  {
    name: "long-client",
    invoice: {
      clientName: "The Board of Trustees of the Mahatma Gandhi Memorial Institute of Education, Research and Rural Development (Registered Society)",
      clientAddress: "Administrative Block, Level 3, Institutional Area, Sector 62\nNoida, Gautam Buddha Nagar, Uttar Pradesh - 201309",
    },
    items: 3,
  },
];

export const PAGE_SIZE_IDS = ["A4", "LETTER"] as const;

export const prefsFor = (pageSize: RenderPrefsV1["pageSize"], over: Partial<RenderPrefsV1> = {}): RenderPrefsV1 => ({ ...DEFAULT_PREFS, pageSize, ...over });

export interface Rendered {
  fixture: BuiltFixture;
  prefs: RenderPrefsV1;
  result: RenderInvoiceResult;
  pdf: RenderedPdf;
}

let ready = false;
/** Registers fonts and installs the measurer once per process. */
export function ensureSetup(): void {
  if (!ready) {
    setupPdfTest();
    ready = true;
  }
}

export async function renderFixture(spec: FixtureSpec, prefs: RenderPrefsV1): Promise<Rendered> {
  ensureSetup();
  const fixture = buildFixture(spec);
  const result = await renderInvoicePdf({ model: fixture.model, prefs });
  const pdf = await parsePdfText(result.bytes);
  return { fixture, prefs, result, pdf };
}