/**
 * pdf.ts — render the printable Codex PDF.
 *
 * Layout follows section "PDF rendering" of the design doc. The input is a
 * flat list of per-Aztec PNG byte arrays (one PNG per code, not one per page).
 * We compute pagination from `CODES_PER_PAGE` and embed each PNG into the
 * grid. Each PNG is embedded once via `pdfDoc.embedPng()` — pdf-lib reuses
 * the embedded image object across pages automatically, so even multi-page
 * Codexes stay compact in file size.
 *
 * Fonts: standard 14, available in every PDF viewer (no font embedding cost).
 * The cream/ink palette is intentionally low-contrast so the printed page
 * reads like an artifact rather than a tax form.
 *
 * Recovery words never appear in the PDF — they are paper-only, kept
 * physically separate from the Codex by design (see peach_codex_addendum.md).
 */

import { PDFDocument, type PDFFont, type PDFPage, rgb, StandardFonts } from "pdf-lib";
import {
  CODES_PER_COL,
  CODES_PER_PAGE,
  CODES_PER_ROW,
  CodexError,
  type CodexManifest,
} from "../../shared/codex-types";
import {
  CODE_SIZE,
  COL_GAP,
  HEADER_GAP,
  HEADER_HEIGHT,
  MARGIN,
  PAGE_HEIGHT,
  PAGE_WIDTH,
  ROW_GAP,
} from "./pdf-layout";

// ── Layout constants ────────────────────────────────────────────────────────
// Page geometry (A4, margins, header height, code size, gaps) is imported
// from ./pdf-layout so the PDF importer can crop matching regions out of the
// rendered canvas without drifting from the generator.

const HEADER_HAIRLINE = 0.5;

const FOOTER_HEIGHT = 32;
const FOOTER_HAIRLINE = 0.5;

const CREAM = rgb(0.961, 0.941, 0.91);
const INK = rgb(0.102, 0.094, 0.086);

/**
 * Render the full A4 Codex PDF. Returns the serialized PDF bytes ready to be
 * blob-downloaded or printed. `aztecPngs` is one PNG per code, in chunk-index
 * order. Recovery words are never drawn here — they are paper-only.
 */
export async function renderCodexPDF(
  aztecPngs: Uint8Array[],
  manifest: CodexManifest,
): Promise<Uint8Array> {
  if (aztecPngs.length !== manifest.totalChunks) {
    throw new CodexError(
      "PDF_GENERATION_FAILED",
      `PDF render: expected ${manifest.totalChunks} Aztec images, got ${aztecPngs.length}`,
    );
  }
  void CODES_PER_COL; // Imported for spec parity; the row math derives the column count.

  const pdfDoc = await PDFDocument.create();

  // Use Times-Italic for the brand mark and Courier for verify codes / labels.
  // The standard 14 fonts cover everything we need without embedding overhead.
  const serif = await pdfDoc.embedFont(StandardFonts.TimesRomanItalic);
  const mono = await pdfDoc.embedFont(StandardFonts.Courier);
  const monoBold = await pdfDoc.embedFont(StandardFonts.CourierBold);

  const embeddedImages = await Promise.all(aztecPngs.map((bytes) => pdfDoc.embedPng(bytes)));

  const pageCount = Math.ceil(manifest.totalChunks / CODES_PER_PAGE);

  for (let pageIndex = 0; pageIndex < pageCount; pageIndex++) {
    const page = pdfDoc.addPage([PAGE_WIDTH, PAGE_HEIGHT]);
    const startIndex = pageIndex * CODES_PER_PAGE;
    const pageImages = embeddedImages.slice(startIndex, startIndex + CODES_PER_PAGE);

    drawBackground(page);
    drawBorder(page);
    drawHeader(page, manifest, pageIndex, pageCount, serif, mono, monoBold);

    const gridTop = PAGE_HEIGHT - MARGIN - HEADER_HEIGHT - HEADER_GAP;
    drawAztecGrid(page, pageImages, startIndex, gridTop, mono);

    drawFooter(page, manifest, serif, mono);
  }

  try {
    return await pdfDoc.save();
  } catch (err) {
    throw new CodexError(
      "PDF_GENERATION_FAILED",
      `pdf-lib save() failed: ${err instanceof Error ? err.message : String(err)}`,
    );
  }
}

// ── Page chrome ─────────────────────────────────────────────────────────────

function drawBackground(page: PDFPage): void {
  page.drawRectangle({ x: 0, y: 0, width: PAGE_WIDTH, height: PAGE_HEIGHT, color: CREAM });
}

function drawBorder(page: PDFPage): void {
  page.drawRectangle({
    x: MARGIN - 6,
    y: MARGIN - 6,
    width: PAGE_WIDTH - 2 * (MARGIN - 6),
    height: PAGE_HEIGHT - 2 * (MARGIN - 6),
    borderColor: INK,
    borderOpacity: 0.2,
    borderWidth: 0.75,
  });
}

function drawHeader(
  page: PDFPage,
  manifest: CodexManifest,
  pageIndex: number,
  pageCount: number,
  serif: PDFFont,
  mono: PDFFont,
  monoBold: PDFFont,
): void {
  const y = PAGE_HEIGHT - MARGIN - HEADER_HEIGHT + 14;

  // The standard 14 PDF fonts use WinAnsi encoding which omits ●. Use the
  // middle-dot bullet (U+00B7), which renders close enough to the spec's
  // filled-circle peach mark for printed output.
  page.drawText("· peach codex", { x: MARGIN, y, size: 13, font: serif, color: INK });

  const pageText = `Page ${pageIndex + 1} of ${pageCount}`;
  const pageTextWidth = mono.widthOfTextAtSize(pageText, 9);
  page.drawText(pageText, {
    x: (PAGE_WIDTH - pageTextWidth) / 2,
    y,
    size: 9,
    font: mono,
    color: INK,
    opacity: 0.5,
  });

  const verifyText = manifest.verifyCode;
  const verifyWidth = monoBold.widthOfTextAtSize(verifyText, 10);
  page.drawText(verifyText, {
    x: PAGE_WIDTH - MARGIN - verifyWidth,
    y,
    size: 10,
    font: monoBold,
    color: INK,
  });

  page.drawLine({
    start: { x: MARGIN, y: PAGE_HEIGHT - MARGIN - HEADER_HEIGHT },
    end: { x: PAGE_WIDTH - MARGIN, y: PAGE_HEIGHT - MARGIN - HEADER_HEIGHT },
    thickness: HEADER_HAIRLINE,
    color: INK,
    opacity: 0.2,
  });
}

// ── Aztec grid ──────────────────────────────────────────────────────────────

/**
 * The `images` parameter is a slice of pre-embedded PDFImage objects for
 * THIS page only. `startIndex` is the global chunk index of `images[0]` and
 * is used solely to label each code with its 1-based number.
 */
function drawAztecGrid(
  page: PDFPage,
  images: import("pdf-lib").PDFImage[],
  startIndex: number,
  gridTop: number,
  mono: PDFFont,
): void {
  for (let i = 0; i < images.length; i++) {
    const col = i % CODES_PER_ROW;
    const row = Math.floor(i / CODES_PER_ROW);
    const x = MARGIN + col * (CODE_SIZE + COL_GAP);
    const y = gridTop - row * (CODE_SIZE + ROW_GAP + 14) - CODE_SIZE;

    page.drawImage(images[i]!, { x, y, width: CODE_SIZE, height: CODE_SIZE });

    const label = String(startIndex + i + 1).padStart(2, "0");
    const labelWidth = mono.widthOfTextAtSize(label, 8);
    page.drawText(label, {
      x: x + CODE_SIZE / 2 - labelWidth / 2,
      y: y - 11,
      size: 8,
      font: mono,
      color: INK,
      opacity: 0.55,
    });
  }
}

// ── Footer ──────────────────────────────────────────────────────────────────

function drawFooter(
  page: PDFPage,
  manifest: CodexManifest,
  serif: PDFFont,
  mono: PDFFont,
): void {
  page.drawLine({
    start: { x: MARGIN, y: MARGIN + FOOTER_HEIGHT },
    end: { x: PAGE_WIDTH - MARGIN, y: MARGIN + FOOTER_HEIGHT },
    thickness: FOOTER_HAIRLINE,
    color: INK,
    opacity: 0.15,
  });

  const footerY = MARGIN + 10;

  page.drawText("This document restores your Peach vault. Keep it private. Keep it safe.", {
    x: MARGIN,
    y: footerY + 10,
    size: 7,
    font: serif,
    color: INK,
    opacity: 0.45,
  });

  const date = new Date(manifest.generatedAt).toISOString().slice(0, 10);
  const meta = `${manifest.entryCount} entries · ${date} · ${manifest.verifyCode}`;
  const metaWidth = mono.widthOfTextAtSize(meta, 7);
  page.drawText(meta, {
    x: PAGE_WIDTH - MARGIN - metaWidth,
    y: footerY + 10,
    size: 7,
    font: mono,
    color: INK,
    opacity: 0.45,
  });

  const siteText = "peachpasswords.com";
  const siteWidth = serif.widthOfTextAtSize(siteText, 7);
  page.drawText(siteText, {
    x: (PAGE_WIDTH - siteWidth) / 2,
    y: footerY,
    size: 7,
    font: serif,
    color: INK,
    opacity: 0.3,
  });
}