import * as fs from 'fs';
import * as path from 'path';
import { PDFDocument, rgb } from 'pdf-lib';

const FONT_SEARCH_PATHS = [
  path.join(__dirname, '..', '..', '..', 'assets', 'fonts', 'NotoSansSC-VF.ttf'),
  'C:/Windows/Fonts/NotoSansSC-VF.ttf',
  'C:/Windows/Fonts/msyh.ttc',
  'C:/Windows/Fonts/simsun.ttc',
  '/usr/share/fonts/opentype/noto/NotoSansCJK-Regular.ttc',
  '/usr/share/fonts/truetype/noto/NotoSansCJK-Regular.ttc',
];

let cachedFontBytes: Buffer | null = null;

function findFont(): Buffer {
  if (cachedFontBytes) return cachedFontBytes;
  for (const p of FONT_SEARCH_PATHS) {
    try {
      if (fs.existsSync(p)) {
        cachedFontBytes = fs.readFileSync(p);
        return cachedFontBytes;
      }
    } catch { }
  }
  return Buffer.alloc(0);
}

interface PdfReportOptions {
  title: string;
  subtitle?: string;
  sections: PdfSection[];
}

interface PdfSection {
  title: string;
  lines: string[];
}

function textToHex(str: string): string {
  let hex = '';
  for (let i = 0; i < str.length; i++) {
    hex += str.charCodeAt(i).toString(16).toUpperCase().padStart(4, '0');
  }
  return hex;
}

export async function generateAssessmentPdf(options: PdfReportOptions): Promise<Buffer> {
  const doc = await PDFDocument.create();

  const fontBytes = findFont();
  if (fontBytes.length === 0) {
    throw new Error('No CJK font found. Install Noto Sans SC or similar.');
  }

  const FONT_DESC_REF = { ref: null as any };
  const FONT_REF = { ref: null as any };

  function prepareFont(page: any) {
    const fontProgRef = ctx.nextRef();
    ctx.assign(fontProgRef, ctx.flateStream(fontBytes));

    const fontDescRef = ctx.nextRef();
    ctx.assign(fontDescRef, ctx.obj({
      Type: 'FontDescriptor',
      FontName: 'CJKFont',
      Flags: 4,
      FontBBox: [0, -300, 1000, 1000],
      ItalicAngle: 0,
      Ascent: 900,
      Descent: -200,
      CapHeight: 800,
      StemV: 80,
      FontFile2: fontProgRef,
    }));
    FONT_DESC_REF.ref = fontDescRef;

    const cidFontRef = ctx.nextRef();
    ctx.assign(cidFontRef, ctx.obj({
      Type: 'Font',
      Subtype: 'CIDFontType2',
      BaseFont: 'CJKFont',
      CIDSystemInfo: ctx.obj({
        Registry: 'Adobe',
        Ordering: 'Identity',
        Supplement: 0,
      }),
      FontDescriptor: fontDescRef,
      W: [0, [500]],
    }));

    const fontRef = ctx.nextRef();
    ctx.assign(fontRef, ctx.obj({
      Type: 'Font',
      Subtype: 'Type0',
      BaseFont: 'CJKFont',
      Encoding: 'Identity-H',
      DescendantFonts: [cidFontRef],
    }));
    FONT_REF.ref = fontRef;

    const fontKey = page.node.newFontDictionaryKey('F1');
    page.node.setFontDictionary(fontKey, fontRef);
  }

  const margin = 50;
  const pageWidth = 595.28;
  const pageHeight = 841.89;

  const ctx = doc.context as any;
  let currentPage = doc.addPage([pageWidth, pageHeight]);
  let contentOps = '';
  let y = pageHeight - 50;

  prepareFont(currentPage);

  function addFontToPage(page: any) {
    const fontKey = page.node.newFontDictionaryKey('F1');
    page.node.setFontDictionary(fontKey, FONT_REF.ref);
  }

  function ensureSpace(needed: number) {
    const bottomMargin = 60;
    if (y - needed < bottomMargin) {
      const contentObj = ctx.flateStream(contentOps);
      const contentRef = ctx.nextRef();
      ctx.assign(contentRef, contentObj);
      currentPage.node.addContentStream(contentRef);

      currentPage = doc.addPage([pageWidth, pageHeight]);
      addFontToPage(currentPage);
      contentOps = '';
      y = pageHeight - 50;
    }
  }

  function addLine(text: string, size: number, bold: boolean = false) {
    const lines = text.split('\n');
    for (const line of lines) {
      ensureSpace(size * 1.5);
      const hex = textToHex(line);
      contentOps += `BT\n/F1 ${size} Tf\n1 0 0 1 ${margin} ${y} Tm\n<${hex}> Tj\nET\n`;
      y -= size * 1.5;
    }
  }

  function addSeparator() {
    ensureSpace(12);
    let hex = '';
    for (let i = 0; i < 55; i++) hex += '002D';
    contentOps += `BT\n/F1 8 Tf\n1 0 0 1 ${margin} ${y} Tm\n<${hex}> Tj\nET\n`;
    y -= 12;
  }

  addLine(options.title, 22);
  y -= 4;
  if (options.subtitle) {
    addLine(options.subtitle, 10);
    y -= 4;
  }
  addSeparator();

  for (const section of options.sections) {
    ensureSpace(30);
    addLine(section.title, 12);
    for (const line of section.lines) {
      addLine(line, 10);
    }
    y -= 6;
  }

  addSeparator();
  addLine('--- End of Report ---', 9);

  const contentObj = ctx.flateStream(contentOps);
  const contentRef = ctx.nextRef();
  ctx.assign(contentRef, contentObj);
  currentPage.node.addContentStream(contentRef);

  return Buffer.from(await doc.save());
}