/**
 * PDF exporter (via jsPDF).
 *
 * Renders the flattened project to a single-page-per-chapter A4 PDF. Text is
 * laid out with a small manual word-wrap engine so inline marks (bold/italic/
 * code/link) can be drawn with the correct font per run. The theme supplies
 * colours, fonts, and page margins.
 *
 * jsPDF is a browser-oriented library but runs unmodified in Node, so the same
 * code path serves both the web app's download button and the CLI.
 */
import jsPDF from "jspdf";

import { normalizePdfId } from "./determinism.js";
import type { Block, FlatProject, Mark } from "./model.js";
import { getTheme, type Theme } from "./themes.js";

interface Run {
  text: string;
  marks: Mark[];
}

function buildRuns(text: string, marks: Mark[]): Run[] {
  if (!marks.length) return [{ text, marks: [] }];
  const boundaries = new Set<number>([0, text.length]);
  for (const m of marks) {
    boundaries.add(Math.max(0, Math.min(text.length, m.start)));
    boundaries.add(Math.max(0, Math.min(text.length, m.end)));
  }
  const points = Array.from(boundaries).sort((a, b) => a - b);
  const runs: Run[] = [];
  for (let i = 0; i < points.length - 1; i++) {
    const start = points[i]!;
    const end = points[i + 1]!;
    const runMarks = marks.filter((m) => m.start <= start && m.end >= end);
    runs.push({ text: text.slice(start, end), marks: runMarks });
  }
  return runs;
}

function resolvePdfFont(fontFamily: string): "times" | "helvetica" | "courier" {
  const lower = fontFamily.toLowerCase();
  if (lower.includes("mono") || lower.includes("courier") || lower.includes("consolas")) {
    return "courier";
  }
  if (
    lower.includes("serif") ||
    lower.includes("garamond") ||
    lower.includes("georgia") ||
    lower.includes("iowan") ||
    lower.includes("times")
  ) {
    return "times";
  }
  return "helvetica";
}

function setRunFont(doc: jsPDF, run: Run, theme: Theme): void {
  const hasCode = run.marks.some((m) => m.type === "code");
  const hasBold = run.marks.some((m) => m.type === "bold");
  const hasItalic = run.marks.some((m) => m.type === "italic");
  doc.setFont(
    hasCode ? "courier" : resolvePdfFont(theme.fontFamily),
    hasBold ? "bold" : hasItalic ? "italic" : "normal",
  );
}

function pageGeometry() {
  const pageWidth = 595.28; // A4 in points
  const pageHeight = 841.89;
  const margin = 56;
  const maxWidth = pageWidth - 2 * margin;
  const lineHeight = 14;
  return { pageWidth, pageHeight, margin, maxWidth, lineHeight };
}

function newPage(doc: jsPDF, theme: Theme): void {
  doc.setFont(resolvePdfFont(theme.fontFamily), "normal");
  doc.setTextColor(hexToRgb(theme.colors.text));
  doc.setFillColor(hexToRgb(theme.colors.background));
  doc.rect(0, 0, doc.internal.pageSize.getWidth(), doc.internal.pageSize.getHeight(), "F");
}

function hexToRgb(hex: string): string {
  const clean = hex.replace("#", "");
  const r = parseInt(clean.slice(0, 2), 16);
  const g = parseInt(clean.slice(2, 4), 16);
  const b = parseInt(clean.slice(4, 6), 16);
  return `rgb(${r}, ${g}, ${b})`;
}

function renderParagraph(
  doc: jsPDF,
  text: string,
  marks: Mark[],
  x: number,
  y: number,
  maxWidth: number,
  lineHeight: number,
  theme: Theme
): number {
  const runs = buildRuns(text, marks);
  let cx = x;
  let cy = y;
  for (const run of runs) {
    setRunFont(doc, run, theme);
    for (const word of run.text.split(" ")) {
      const wordWidth = doc.getTextWidth(word + " ");
      if (cx + wordWidth > x + maxWidth && cx > x) {
        cy += lineHeight;
        cx = x;
      }
      doc.text(word, cx, cy);
      cx += wordWidth;
    }
  }
  return cy;
}

function renderBlocks(
  doc: jsPDF,
  blocks: Block[],
  theme: Theme
): void {
  const { margin, maxWidth, lineHeight } = pageGeometry();
  let y = margin;

  for (const block of blocks) {
    switch (block.type) {
      case "heading": {
        const level = Math.max(1, Math.min(6, block.level ?? 1));
        const size = level === 1 ? 24 : level === 2 ? 18 : 14;
        doc.setFontSize(size);
        doc.setFont(resolvePdfFont(theme.fontFamily), "bold");
        doc.setTextColor(hexToRgb(theme.colors.heading));
        y += size * 0.9;
        y = renderParagraph(doc, block.text ?? "", block.marks ?? [], margin, y, maxWidth, lineHeight * 1.2, theme);
        y += lineHeight * 0.6;
        break;
      }
      case "paragraph": {
        doc.setFontSize(12);
        doc.setFont(resolvePdfFont(theme.fontFamily), "normal");
        doc.setTextColor(hexToRgb(theme.colors.text));
        y += lineHeight;
        y = renderParagraph(doc, block.text ?? "", block.marks ?? [], margin, y, maxWidth, lineHeight, theme);
        y += lineHeight * 0.4;
        break;
      }
      case "sceneBreak": {
        y += lineHeight;
        doc.setFontSize(12);
        doc.setFont("helvetica", "italic");
        doc.setTextColor(hexToRgb(theme.colors.muted));
        doc.text("***", margin + maxWidth / 2, y, { align: "center" });
        y += lineHeight * 0.6;
        break;
      }
      case "blockquote": {
        y += lineHeight;
        doc.setFontSize(12);
        doc.setFont("helvetica", "italic");
        doc.setTextColor(hexToRgb(theme.colors.muted));
        y = renderParagraph(doc, block.text ?? "", block.marks ?? [], margin, y, maxWidth - 28, lineHeight, theme);
        y += lineHeight * 0.4;
        break;
      }
      case "codeBlock": {
        y += lineHeight;
        doc.setFontSize(9);
        doc.setFont("courier", "normal");
        doc.setTextColor(hexToRgb(theme.colors.text));
        for (const line of (block.text ?? "").split("\n")) {
          y += lineHeight * 0.7;
          doc.text(line, margin, y, { maxWidth: maxWidth });
        }
        y += lineHeight * 0.4;
        break;
      }
      case "list": {
        for (const item of block.children ?? []) {
          y += lineHeight;
          doc.setFontSize(12);
          doc.setFont("helvetica", "normal");
          doc.setTextColor(hexToRgb(theme.colors.text));
          const prefix = block.listType === "ordered" ? "• " : "• ";
          y = renderParagraph(doc, prefix + (item.text ?? ""), item.marks ?? [], margin, y, maxWidth, lineHeight, theme);
          y += lineHeight * 0.3;
        }
        break;
      }
      case "footnote": {
        y += lineHeight;
        doc.setFontSize(9);
        doc.setFont("helvetica", "italic");
        doc.setTextColor(hexToRgb(theme.colors.muted));
        y = renderParagraph(doc, block.text ?? "", [], margin, y, maxWidth, lineHeight * 0.8, theme);
        y += lineHeight * 0.4;
        break;
      }
    }

    // Add a page break when we run low on vertical space.
    if (y > pageGeometry().pageHeight - margin) {
      doc.addPage();
      y = margin;
    }
  }
}

export interface PdfOptions {
  theme?: Theme;
}

/**
 * Serialize a flattened project to a PDF (`.pdf` bytes).
 *
 * @param project the flattened project (frontmatter + blocks)
 * @param options theme
 */
export async function exportPdf(project: FlatProject, options?: PdfOptions): Promise<Uint8Array> {
  const theme = options?.theme ?? getTheme(undefined);
  const fm = project.frontmatter;
  const { margin } = pageGeometry();

  const doc = new jsPDF({ unit: "pt", format: "a4" });
  newPage(doc, theme);

  // Title.
  doc.setFontSize(28);
  doc.setFont("helvetica", "bold");
  doc.setTextColor(hexToRgb(theme.colors.heading));
  doc.text(fm.title, margin, margin + 20, { maxWidth: pageGeometry().maxWidth });

  // Author.
  if (fm.author) {
    doc.setFontSize(14);
    doc.setFont("helvetica", "italic");
    doc.setTextColor(hexToRgb(theme.colors.muted));
    doc.text(fm.author, margin, margin + 48, { maxWidth: pageGeometry().maxWidth });
  }

  renderBlocks(doc, project.blocks, theme);

  return normalizePdfId(new Uint8Array(doc.output("arraybuffer")));
}