import type { Mechanic } from "./data";
import { mechanicQrPayload, isBadgeReady } from "./mechanics";
import { qrMatrix, isDark } from "./qr";

/**
 * Builds the printable badge sheet as a REAL PDF — vector, not a screenshot of the
 * page and not a browser print job.
 *
 * The QR is drawn module by module as a filled rectangle, so it stays perfectly sharp
 * at any printer resolution or zoom level. Rasterising it into a PNG first would look
 * fine on screen and go fuzzy on a badge somebody scans with a phone off a lanyard.
 *
 * A4 portrait, four badges per row, cut lines included so the sheet can be guillotined.
 */
export async function buildBadgesPdf(mechanics: Pick<Mechanic, "name" | "employee_code" | "role">[], title = "Mega Plant — Mechanic Badges"): Promise<Uint8Array> {
  const { PDFDocument, StandardFonts, rgb } = await import("pdf-lib");
  const doc = await PDFDocument.create();

  const page = doc.addPage([595.28, 841.89]); // A4 portrait, points
  const regular = await doc.embedFont(StandardFonts.Helvetica);
  const bold = await doc.embedFont(StandardFonts.HelveticaBold);

  const INK = rgb(0, 0, 0);
  const GREY = rgb(0.38, 0.42, 0.45);
  const HAIRLINE = rgb(0.82, 0.85, 0.87);

  const printables = mechanics.filter(isBadgeReady);

  const margin = 36;
  const cols = 3;
  const gutter = 14;
  const cellW = (page.getWidth() - margin * 2 - gutter * (cols - 1)) / cols;
  const cellH = 232;

  page.drawText(title, {
    x: margin,
    y: page.getHeight() - margin + 2,
    size: 13,
    font: bold,
    color: INK,
  });
  page.drawText(
    `${printables.length} badge${printables.length !== 1 ? "s" : ""} · each QR scans to the name and employee number`,
    { x: margin, y: page.getHeight() - margin - 12, size: 8.5, font: regular, color: GREY },
  );

  const top = page.getHeight() - margin - 28;

  printables.forEach((m, i) => {
    const col = i % cols;
    const row = Math.floor(i / cols);
    const x = margin + col * (cellW + gutter);
    const y = top - row * (cellH + gutter) - cellH;

    // Cell border doubles as the cut line.
    page.drawRectangle({
      x,
      y,
      width: cellW,
      height: cellH,
      borderColor: HAIRLINE,
      borderWidth: 0.5,
    });

    const matrix = qrMatrix(mechanicQrPayload(m));
    const qrSize = 104;
    const qrX = x + (cellW - qrSize) / 2;
    const qrY = y + cellH - 20 - qrSize;
    const unit = qrSize / matrix.size;

    // White backing first: a PDF page is transparent by default, and a transparent QR
    // prints as nothing on most printers.
    page.drawRectangle({ x: qrX, y: qrY, width: qrSize, height: qrSize, color: rgb(1, 1, 1) });

    // Merge horizontally adjacent dark modules into one rect — same trick as the SVG,
    // so the file stays small.
    for (let my = 0; my < matrix.size; my++) {
      let run = 0;
      for (let mx = 0; mx <= matrix.size; mx++) {
        const dark = mx < matrix.size && isDark(matrix, mx, my);
        if (dark) {
          run++;
        } else if (run > 0) {
          page.drawRectangle({
            x: qrX + (mx - run) * unit,
            y: qrY + (matrix.size - my - 1) * unit,
            width: run * unit,
            height: unit,
            color: INK,
          });
          run = 0;
        }
      }
    }

    let cursor = qrY - 18;
    const nameSize = Math.min(11, (cellW - 12) / (m.name.length * 0.58));
    page.drawText(m.name, {
      x: x + (cellW - bold.widthOfTextAtSize(m.name, nameSize)) / 2,
      y: cursor,
      size: nameSize,
      font: bold,
      color: INK,
    });

    cursor -= 13;
    page.drawText(m.employee_code, {
      x: x + (cellW - regular.widthOfTextAtSize(m.employee_code, 10)) / 2,
      y: cursor,
      size: 10,
      font: regular,
      color: GREY,
    });

    cursor -= 12;
    const role = m.role || "Mechanic";
    page.drawText(role.toUpperCase(), {
      x: x + (cellW - regular.widthOfTextAtSize(role.toUpperCase(), 7)) / 2,
      y: cursor,
      size: 7,
      font: regular,
      color: GREY,
    });
  });

  if (printables.length === 0) {
    page.drawText("No mechanic has an employee number yet — there is nothing to print.", {
      x: margin,
      y: page.getHeight() / 2,
      size: 11,
      font: regular,
      color: INK,
    });
  }

  return doc.save();
}

/** Trigger a browser download for the generated bytes. */
export function downloadPdf(bytes: Uint8Array, filename: string) {
  // Copy into a fresh ArrayBuffer: pdf-lib's Uint8Array can be a view onto a larger
  // buffer, and Blob would then save the padding too.
  const blob = new Blob([new Uint8Array(bytes)], { type: "application/pdf" });
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  a.remove();
  // Revoke on the next tick so the click has definitely been handled.
  setTimeout(() => URL.revokeObjectURL(url), 1000);
}
/**
 * The oil drum labels: one QR per tracked oil, printed as a label for the drum or
 * dispenser. Same vector drawing and the same encoder as the badge sheet, so a label
 * can never scan to a different oil than the one on screen.
 */
export async function buildOilLabelsPdf(
  items: { name: string; code: string; colour: string; drum_litres: number }[],
  payloadOf: (i: { name: string; code: string }) => string,
): Promise<Uint8Array> {
  const { PDFDocument, StandardFonts, rgb } = await import("pdf-lib");
  const doc = await PDFDocument.create();
  const page = doc.addPage([595.28, 841.89]);
  const regular = await doc.embedFont(StandardFonts.Helvetica);
  const bold = await doc.embedFont(StandardFonts.HelveticaBold);

  const INK = rgb(0, 0, 0);
  const GREY = rgb(0.38, 0.42, 0.45);
  const HAIRLINE = rgb(0.82, 0.85, 0.87);
  const hex = (c: string) => {
    const m = /^#?([0-9a-f]{6})$/i.exec(c || "");
    if (!m) return rgb(0, 0, 0);
    const n = parseInt(m[1], 16);
    return rgb(((n >> 16) & 255) / 255, ((n >> 8) & 255) / 255, (n & 255) / 255);
  };

  const margin = 36;
  page.drawText("Mega Plant — Oil & Diesel Labels", {
    x: margin, y: page.getHeight() - margin + 2, size: 13, font: bold, color: INK,
  });
  page.drawText("Cut and stick each label on its drum or tank. The QR identifies the product.", {
    x: margin, y: page.getHeight() - margin - 12, size: 8.5, font: regular, color: GREY,
  });

  const cellW = (page.getWidth() - margin * 2) / 2;
  const cellH = 250;
  const top = page.getHeight() - margin - 28;

  items.forEach((item, i) => {
    const x = margin + (i % 2) * cellW;
    const y = top - Math.floor(i / 2) * cellH - cellH;

    page.drawRectangle({
      x: x + 6, y, width: cellW - 12, height: cellH - 6,
      borderColor: HAIRLINE, borderWidth: 0.5,
    });

    // A colour bar, so the two labels are told apart at a glance on the drum.
    page.drawRectangle({ x: x + 6, y: y + cellH - 22, width: cellW - 12, height: 10, color: hex(item.colour) });

    const matrix = qrMatrix(payloadOf(item));
    const qrSize = 120;
    const qrX = x + (cellW - qrSize) / 2;
    const qrY = y + cellH - 34 - qrSize;
    const unit = qrSize / matrix.size;

    // Transparent pages print as nothing, so the backing plate is not optional.
    page.drawRectangle({ x: qrX, y: qrY, width: qrSize, height: qrSize, color: rgb(1, 1, 1) });
    for (let my = 0; my < matrix.size; my++) {
      let run = 0;
      for (let mx = 0; mx <= matrix.size; mx++) {
        const dark = mx < matrix.size && isDark(matrix, mx, my);
        if (dark) {
          run++;
        } else if (run > 0) {
          page.drawRectangle({
            x: qrX + (mx - run) * unit,
            y: qrY + (matrix.size - my - 1) * unit,
            width: run * unit, height: unit, color: INK,
          });
          run = 0;
        }
      }
    }

    let cursor = qrY - 20;
    page.drawText(item.name, {
      x: x + (cellW - bold.widthOfTextAtSize(item.name, 14)) / 2,
      y: cursor, size: 14, font: bold, color: INK,
    });
    cursor -= 15;
    page.drawText(item.code, {
      x: x + (cellW - regular.widthOfTextAtSize(item.code, 11)) / 2,
      y: cursor, size: 11, font: regular, color: GREY,
    });
    cursor -= 13;
    const drum = `${item.drum_litres || 210} L ${item.code.startsWith("FUEL") ? "tank" : "drum"}`;
    page.drawText(drum, {
      x: x + (cellW - regular.widthOfTextAtSize(drum, 9)) / 2,
      y: cursor, size: 9, font: regular, color: GREY,
    });
  });

  return doc.save();
}