// PDF.js viewer using pdfjs-dist 6.1.200 legacy build.
// Depends on global pdfjsLib (loaded in index.html).

class PdfViewer {
  constructor(container) {
    this.container = container;
    this.generation = 0;
    this.loadingTask = null;
    this.doc = null;
    this.renderTasks = new Set();
    this.lastUrl = null;
    this.lastSize = null;
    this._createDOM();
  }

  _createDOM() {
    // The pages container is always visible (never hidden).
    // Loading and error states are overlays on top.
    this.container.innerHTML = `
      <div class="pdf-v-pages"></div>
      <div class="pdf-v-overlay pdf-v-loading" hidden>Loading PDF\u2026</div>
      <div class="pdf-v-overlay pdf-v-error" hidden>
        <div class="pdf-v-error-msg"></div>
        <button class="pdf-v-retry">Retry</button>
      </div>
    `;
    this.pagesDiv = this.container.querySelector(".pdf-v-pages");
    this.loadingDiv = this.container.querySelector(".pdf-v-loading");
    this.errorDiv = this.container.querySelector(".pdf-v-error");
    this.errorMsg = this.container.querySelector(".pdf-v-error-msg");
    this.retryBtn = this.container.querySelector(".pdf-v-retry");

    this.retryBtn.addEventListener("click", () => {
      if (this.lastUrl != null) {
        this._setState("loading");
        this._loadInternal(this.lastUrl, this.lastSize);
      }
    });
  }

  _setState(state) {
    this.loadingDiv.hidden = true;
    this.errorDiv.hidden = true;
    if (state === "loading") this.loadingDiv.hidden = false;
    if (state === "error") this.errorDiv.hidden = false;
    this._viewerState = state;
  }

  async load(url, byteSize) {
    this.lastUrl = url;
    this.lastSize = byteSize;
    this._setState("loading");
    await this._loadInternal(url, byteSize);
  }

  async _loadInternal(url, _byteSize) {
    const generation = ++this.generation;
    console.log(
      `[BizMatch QC] PDF viewer load started: generation ${generation}`,
    );

    // Await cleanup of previous document (promises may be involved)
    await this._disposeCurrentDocument();
    if (generation !== this.generation) return;

    this.pagesDiv.innerHTML = "";

    const loadStart = performance.now();
    try {
      const task = pdfjsLib.getDocument({
        url,
        rangeChunkSize: 65536,
        disableAutoFetch: false,
      });
      this.loadingTask = task;

      const doc = await task.promise;
      if (generation !== this.generation) {
        doc.destroy();
        return;
      }
      this.doc = doc;

      const numPages = doc.numPages;
      const loadMs = Math.round(performance.now() - loadStart);
      console.log(
        `[BizMatch QC] PDF document loaded: ${numPages} pages in ${loadMs}ms`,
      );

      const viewerWidth = this._getViewportWidth();
      console.log(`[BizMatch QC] PDF usable render width: ${viewerWidth}px`);

      const pageStart = performance.now();
      await this._renderPage(doc, 1, viewerWidth, generation);
      if (generation !== this.generation) return;

      this._setState(null); // Remove loading overlay
      const firstPageMs = Math.round(performance.now() - pageStart);
      console.log(
        `[BizMatch QC] PDF page 1 rendered in ${firstPageMs}ms`,
      );
      console.log(
        `[BizMatch QC] First page visible after ${
          Math.round(performance.now() - loadStart)
        }ms`,
      );

      for (let p = 2; p <= numPages; p++) {
        if (generation !== this.generation) return;
        const pStart = performance.now();
        await this._renderPage(doc, p, viewerWidth, generation);
        if (generation !== this.generation) return;
        console.log(
          `[BizMatch QC] PDF page ${p} rendered in ${
            Math.round(performance.now() - pStart)
          }ms`,
        );
        await new Promise((r) => requestAnimationFrame(r));
      }

      const totalMs = Math.round(performance.now() - loadStart);
      console.log(
        `[BizMatch QC] PDF viewer load completed: generation ${generation}`,
      );
      console.log(
        `[BizMatch QC] PDF fully rendered: ${numPages} pages in ${totalMs}ms`,
      );
    } catch (err) {
      if (generation !== this.generation) return;
      // Distinguish cancellation from real errors
      if (isCancellationError(err)) {
        console.log(
          `[BizMatch QC] PDF generation ${generation} cancelled`,
        );
        return;
      }
      const msg = errorMsg(err);
      console.error(`[BizMatch QC] PDF load failed:`, msg);
      this.errorMsg.textContent = `Unable to open PDF: ${msg}`;
      this._setState("error");
    }
  }

  _getViewportWidth() {
    const style = globalThis.getComputedStyle
      ? getComputedStyle(this.pagesDiv)
      : null;
    let padding = 24; // default guess
    if (style) {
      padding = (parseFloat(style.paddingLeft) || 0) +
        (parseFloat(style.paddingRight) || 0);
    }
    const raw = Math.round(this.pagesDiv.clientWidth || 600);
    return Math.max(raw - padding, 200);
  }

  async _disposeCurrentDocument() {
    for (const rt of this.renderTasks) {
      try {
        rt.cancel();
      } catch { /* ok */ }
    }
    this.renderTasks.clear();

    if (this.loadingTask) {
      try {
        await this.loadingTask.destroy();
      } catch { /* ok */ }
      this.loadingTask = null;
    }

    if (this.doc) {
      try {
        await this.doc.destroy();
      } catch { /* ok */ }
      this.doc = null;
    }
  }

  async _renderPage(doc, pageNum, viewerWidth, generation) {
    const pageDiv = document.createElement("div");
    pageDiv.className = "pdf-v-page";
    pageDiv.dataset.page = String(pageNum);
    pageDiv.dataset.renderState = "idle";

    const canvas = document.createElement("canvas");
    pageDiv.appendChild(canvas);
    this.pagesDiv.appendChild(pageDiv);

    pageDiv.dataset.renderState = "rendering";

    try {
      const page = await doc.getPage(pageNum);
      if (generation !== this.generation) return;

      const vp1 = page.getViewport({ scale: 1 });
      const fitScale = viewerWidth / vp1.width;
      const viewport = page.getViewport({ scale: fitScale });

      const dpr = Math.min(globalThis.devicePixelRatio || 1, 2);
      canvas.width = Math.floor(viewport.width * dpr);
      canvas.height = Math.floor(viewport.height * dpr);
      canvas.style.width = `${Math.floor(viewport.width)}px`;
      canvas.style.height = `${Math.floor(viewport.height)}px`;

      const ctx = canvas.getContext("2d");
      const transform = dpr !== 1 ? [dpr, 0, 0, dpr, 0, 0] : undefined;

      const renderTask = page.render({
        canvasContext: ctx,
        viewport,
        transform,
      });
      this.renderTasks.add(renderTask);

      await renderTask.promise;
      this.renderTasks.delete(renderTask);

      if (generation !== this.generation) return;
      pageDiv.dataset.renderState = "rendered";
    } catch (err) {
      if (generation !== this.generation) return;
      if (isCancellationError(err)) return;
      pageDiv.dataset.renderState = "error";
      console.error(
        `[BizMatch QC] Failed to render PDF page ${pageNum}`,
        err,
      );
      if (pageNum === 1) {
        this.errorMsg.textContent = `Unable to open PDF: ${errorMsg(err)}`;
        this._setState("error");
      } else {
        pageDiv.textContent = `Error rendering page ${pageNum}`;
        pageDiv.style.padding = "20px";
        pageDiv.style.color = "#f88";
        pageDiv.style.textAlign = "center";
      }
    }
  }

  destroy() {
    this.generation = 0;
    this._disposeCurrentDocument().catch(() => {});
    this.pagesDiv.innerHTML = "";
    this._setState("loading");
  }
}

function isCancellationError(err) {
  if (!(err instanceof Error)) return false;
  const msg = err.message || "";
  return msg.includes("cancelled") ||
    msg.includes("cancelled") ||
    msg.includes("destroyed") ||
    msg.includes("Worker was destroyed");
}

function errorMsg(err) {
  return err instanceof Error ? err.message : String(err);
}

globalThis.PdfViewer = PdfViewer;