/**
 * Turning notes into files on disk.
 *
 * The point of this is that the notes are not hostage to this program. A single
 * note becomes one Markdown file; a notebook becomes a ZIP with the notes, their
 * images, and any drawings rendered as PNG — everything readable without InkNote
 * ever running again.
 */

import * as sync from "../syncEngine";
import { parseNoteContent } from "../editor/content";
import { parsingExtensions } from "../editor/extensions.js";
import { CANON_W, CANON_H, docStrokes, paintStrokeDoc, sizeCanvas } from "../features/drawing/strokes.js";
import type { NoteContent, NoteMeta, Notebook } from "../types";
import { noteToMarkdown, safeFilename } from "./markdown";
import { asPdfStrokeDoc, hasOverlay } from "../features/pdf/pageStrokes";
import { stampStrokesIntoPdf } from "../features/pdf/stampPdf";
import { printNotes, type PrintableNote } from "./print";
import { bytesToBlob, createZip, download, type ZipEntry } from "./zip";

/** Width the exported drawing is rendered at; the page ratio is kept. */
const DRAWING_EXPORT_W = 1200;

export interface ExportProgress {
  done: number;
  total: number;
  label: string;
}

type Loaded = { meta: NoteMeta; content: NoteContent };

/* ── pieces ── */

/** Renders a stroke document to PNG bytes, so a drawing survives as a picture. */
async function drawingToPng(doc: unknown): Promise<Uint8Array | null> {
  // `doc` is already a stroke document as stored — strokeDocOf() builds one from
  // a bare array and would wrap this one a second time, hiding the strokes.
  if (docStrokes(doc).length === 0) return null;

  const canvas = document.createElement("canvas");
  const height = Math.round((DRAWING_EXPORT_W * CANON_H) / CANON_W);
  const { bw, bh } = sizeCanvas(canvas, DRAWING_EXPORT_W, height);
  const ctx = canvas.getContext("2d");
  if (!ctx) return null;
  paintStrokeDoc(ctx, doc, bw, bh);
  // Strokes are drawn on nothing, which would export as a transparent PNG and
  // leave black ink invisible in a dark image viewer. The paper goes in behind
  // afterwards, because paintStrokeDoc begins by clearing the canvas.
  ctx.setTransform(1, 0, 0, 1, 0, 0);
  ctx.globalCompositeOperation = "destination-over";
  ctx.fillStyle = "#ffffff";
  ctx.fillRect(0, 0, bw, bh);
  ctx.globalCompositeOperation = "source-over";

  const blob = await new Promise<Blob | null>((r) => canvas.toBlob(r, "image/png"));
  if (!blob) return null;
  return new Uint8Array(await blob.arrayBuffer());
}

/** Every attachment id the document refers to. */
function attachmentIds(doc: unknown): string[] {
  const ids = new Set<string>();
  const walk = (n: any) => {
    if (!n) return;
    if (n.type === "image" && n.attrs?.attachmentId) ids.add(n.attrs.attachmentId);
    if (Array.isArray(n.content)) n.content.forEach(walk);
  };
  walk(doc);
  return [...ids];
}

async function loadNote(meta: NoteMeta): Promise<Loaded> {
  return { meta, content: await sync.loadNoteContent(meta.id) };
}

/** Unique filename per note — two notes may well share a title. */
function nameFor(meta: NoteMeta, taken: Set<string>): string {
  const base = safeFilename(meta.title, "Notiz");
  let name = base;
  for (let i = 2; taken.has(name.toLowerCase()); i++) name = `${base} (${i})`;
  taken.add(name.toLowerCase());
  return name;
}

/* ── PDF notes ── */

/**
 * Exports the document behind a PDF note.
 *
 * `withInk` decides whether the drawings come along. Without it the bytes are
 * handed over exactly as imported — the original is never modified in storage,
 * so a clean copy stays available however often it has been drawn on.
 */
export async function exportPdfNote(meta: NoteMeta, withInk: boolean): Promise<void> {
  if (!meta.pdfAttachmentId) throw new Error("Zu dieser Notiz gehört keine PDF-Datei.");
  const bytes = await sync.loadPdfBytes(meta.pdfAttachmentId);
  const name = safeFilename(meta.title, "Dokument");

  if (!withInk) {
    download(bytesToBlob(bytes, "application/pdf"), `${name}.pdf`);
    return;
  }

  const { content } = await loadNote(meta);
  const ink = asPdfStrokeDoc(content.drawingStrokes);
  // Pinned notes count as much as strokes here: both are the reader's own work
  // on the document, and an export that dropped either would lose it silently.
  if (!hasOverlay(ink)) {
    download(bytesToBlob(bytes, "application/pdf"), `${name}.pdf`);
    return;
  }

  const stamped = await stampStrokesIntoPdf(bytes, ink);
  download(bytesToBlob(stamped, "application/pdf"), `${name} (mit Notizen).pdf`);
}

/** True when the PDF carries drawings or pinned notes, so the wizard can say so. */
export async function pdfNoteHasInk(meta: NoteMeta): Promise<boolean> {
  try {
    const { content } = await loadNote(meta);
    return hasOverlay(asPdfStrokeDoc(content.drawingStrokes));
  } catch {
    return false;
  }
}

/* ── single note ── */

/** What a single-note export should contain. */
export type ExportParts = "text" | "drawing" | "both";

/** Whether this note has a drawing — decides which options the wizard offers. */
export async function noteHasDrawing(meta: NoteMeta): Promise<boolean> {
  try {
    const { content } = await loadNote(meta);
    return docStrokes(content.drawingStrokes).length > 0;
  } catch {
    return false;
  }
}

/** The drawing on its own, as a PNG on white paper. */
export async function exportDrawingAsPng(meta: NoteMeta): Promise<void> {
  const { content } = await loadNote(meta);
  const png = await drawingToPng(content.drawingStrokes);
  if (!png) throw new Error("Diese Notiz enthält keine Zeichnung.");
  download(bytesToBlob(png, "image/png"), `${safeFilename(meta.title)}.png`);
}

export async function exportNoteAsMarkdown(meta: NoteMeta): Promise<void> {
  const { content } = await loadNote(meta);
  const doc = parseNoteContent(content.content, parsingExtensions);
  const hasDrawing = docStrokes(content.drawingStrokes).length > 0;
  const ids = attachmentIds(doc);

  const md = noteToMarkdown(doc, {
    title: meta.title,
    updatedAt: meta.updatedAt,
    hasDrawing,
    attachmentPath: (id) => `${safeFilename(meta.title)}-bilder/${id}.png`,
    notePath: () => null, // a lone note has nothing to link to
  });

  // Only worth an archive if there is something to put beside the text.
  if (ids.length === 0 && !hasDrawing) {
    download(new Blob([md], { type: "text/markdown;charset=utf-8" }), `${safeFilename(meta.title)}.md`);
    return;
  }

  const folder = safeFilename(meta.title);
  const entries: ZipEntry[] = [{ name: `${folder}.md`, data: md }];
  for (const id of ids) {
    const bytes = await fetchAttachment(id);
    if (bytes) entries.push({ name: `${folder}-bilder/${id}.png`, data: bytes });
  }
  const png = await drawingToPng(content.drawingStrokes);
  if (png) entries.push({ name: `${folder}-zeichnung.png`, data: png });

  download(createZip(entries), `${folder}.zip`);
}

/* ── PDF ── */

const blobToDataUrl = (blob: Blob): Promise<string> =>
  new Promise((resolve, reject) => {
    const r = new FileReader();
    r.onload = () => resolve(String(r.result));
    r.onerror = () => reject(r.error);
    r.readAsDataURL(blob);
  });

/**
 * Prepares notes for the print dialog.
 *
 * Images have to travel as data URLs: the print document lives in its own
 * iframe, where a blob: URL minted by the app is not resolvable, and an
 * authenticated request is not something a printed page can make.
 */
export async function exportNotesAsPdf(
  metas: NoteMeta[],
  title: string,
  onProgress?: (p: ExportProgress) => void,
  parts: ExportParts = "both"
): Promise<void> {
  const printable: PrintableNote[] = [];
  const total = metas.length;

  for (const [i, meta] of metas.entries()) {
    onProgress?.({ done: i, total, label: meta.title });
    try {
      const content = await sync.loadNoteContent(meta.id);
      const doc = parseNoteContent(content.content, parsingExtensions);

      const images = new Map<string, string>();
      for (const id of attachmentIds(doc)) {
        try {
          images.set(id, await blobToDataUrl(await sync.fetchAttachmentBlob(id)));
        } catch {
          /* a missing image should not stop the rest of the page */
        }
      }

      const png = parts === "text" ? null : await drawingToPng(content.drawingStrokes);
      const drawing = png ? await blobToDataUrl(bytesToBlob(png, "image/png")) : null;

      printable.push({ meta, content, drawing, images, includeText: parts !== "drawing" });
    } catch {
      /* an unreadable note is left out rather than aborting the whole print */
    }
  }

  onProgress?.({ done: total, total, label: "Druckansicht wird geöffnet" });
  await printNotes(printable, title);
}

async function fetchAttachment(id: string): Promise<Uint8Array | null> {
  try {
    const blob = await sync.fetchAttachmentBlob(id);
    return new Uint8Array(await blob.arrayBuffer());
  } catch {
    // One unreachable image must not cost the whole export.
    return null;
  }
}

/* ── many notes ── */

export interface ExportSetOptions {
  /** Shown in the archive name and its index file. */
  label: string;
  notes: NoteMeta[];
  notebooks: Notebook[];
  onProgress?: (p: ExportProgress) => void;
}

export async function exportNotesAsZip({
  label,
  notes,
  notebooks,
  onProgress,
}: ExportSetOptions): Promise<void> {
  const total = notes.length + 1;
  const entries: ZipEntry[] = [];
  const taken = new Set<string>();
  const filenames = new Map<string, string>();

  // Names are settled first, so a link from the first note to the last one can
  // already point at the right file.
  for (const meta of notes) filenames.set(meta.id, nameFor(meta, taken));
  const notePath = (id: string) => {
    const name = filenames.get(id);
    return name ? `${encodeURIComponent(name)}.md` : null;
  };

  const index: string[] = [
    `# ${label}`,
    "",
    `${notes.length} Notizen, exportiert am ${new Date().toLocaleString("de-DE")}`,
    "",
  ];
  const byNotebook = new Map<string | null, NoteMeta[]>();
  for (const n of notes) {
    const key = n.folderId ?? null;
    if (!byNotebook.has(key)) byNotebook.set(key, []);
    byNotebook.get(key)!.push(n);
  }

  let done = 0;
  for (const meta of notes) {
    onProgress?.({ done, total, label: meta.title });
    const name = filenames.get(meta.id)!;
    try {
      const { content } = await loadNote(meta);
      const doc = parseNoteContent(content.content, parsingExtensions);
      const hasDrawing = docStrokes(content.drawingStrokes).length > 0;

      entries.push({
        name: `${name}.md`,
        data: noteToMarkdown(doc, {
          title: meta.title,
          updatedAt: meta.updatedAt,
          hasDrawing,
          attachmentPath: (id) => `bilder/${id}.png`,
          notePath,
        }),
      });

      for (const id of attachmentIds(doc)) {
        if (entries.some((e) => e.name === `bilder/${id}.png`)) continue;
        const bytes = await fetchAttachment(id);
        if (bytes) entries.push({ name: `bilder/${id}.png`, data: bytes });
      }
      const png = await drawingToPng(content.drawingStrokes);
      if (png) entries.push({ name: `zeichnungen/${name}.png`, data: png });
    } catch (err) {
      // A note that cannot be read is named in the index rather than skipped in
      // silence — an export that quietly drops things is worse than useless.
      entries.push({
        name: `${name}.md`,
        data: `# ${meta.title}\n\n> Diese Notiz konnte beim Export nicht gelesen werden.\n> (${(err as Error).message})\n`,
      });
    }
    done++;
  }

  for (const [notebookId, group] of byNotebook) {
    const nb = notebooks.find((b) => b.id === notebookId);
    index.push("", `## ${nb?.name || "Ohne Notizbuch"}`, "");
    for (const n of group) index.push(`- [${n.title || "Untitled"}](${notePath(n.id)})`);
  }
  entries.unshift({ name: "README.md", data: index.join("\n") + "\n" });

  onProgress?.({ done: total, total, label: "Archiv wird gepackt" });
  download(createZip(entries), `${safeFilename(label, "InkNote")}.zip`);
}