// Native Chromium PDF viewer using a single persistent iframe.

class NativePdfViewer {
  constructor(frame, container) {
    this.frame = frame;
    this.container = container;
    this.generation = 0;
    this.currentKey = null;
    this.lastUrl = null;
    this.loadTimer = null;
    this._onLoad = null;
    this._createDOM();
  }

  _createDOM() {
    this.loadingDiv = document.createElement("div");
    this.loadingDiv.className = "native-pdf-loading";
    this.loadingDiv.textContent = "Loading PDF\u2026";
    this.container.appendChild(this.loadingDiv);

    this.errorDiv = document.createElement("div");
    //this.errorDiv.className = "native-pdf-error";

    this.errorMsg = document.createElement("div");
    this.errorMsg.className = "native-pdf-error-msg";
    this.errorDiv.appendChild(this.errorMsg);

    this.retryBtn = document.createElement("button");
    this.retryBtn.className = "native-pdf-retry";
    this.retryBtn.textContent = "Retry";
    this.retryBtn.addEventListener("click", () => {
      if (this.lastUrl && this.currentKey) {
        this._navigate(this.lastUrl, this.currentKey, true);
      }
    });
    this.errorDiv.appendChild(this.retryBtn);
    this.container.appendChild(this.errorDiv);
  }

  _showState(state) {
    this.loadingDiv.classList.toggle("is-visible", state === "loading");
    this.errorDiv.classList.toggle("is-visible", state === "error");
  }

  load(url, _byteSize, key) {
    this._navigate(url, key, false);
  }

  _navigate(url, key, force) {
    if (!force && key && key === this.currentKey) return;

    const generation = ++this.generation;
    this.currentKey = key;
    this.lastUrl = url;

    // Clear old error text, show loading badge
    this.errorMsg.textContent = "";
    this._showState("loading");

    // Shared hide function, idempotent per navigation
    const hideLoading = () => {
      if (generation !== this.generation) return;
      if (this.loadTimer) {
        clearTimeout(this.loadTimer);
        this.loadTimer = null;
      }
      this._showState("loaded");
    };

    // Optional early signal from iframe load event
    if (this._onLoad) this.frame.removeEventListener("load", this._onLoad);
    this._onLoad = hideLoading;
    this.frame.addEventListener("load", hideLoading, { once: true });

    // Fallback: hide loading after 800ms regardless of load event
    if (this.loadTimer) clearTimeout(this.loadTimer);
    this.loadTimer = setTimeout(hideLoading, 800);

    this.frame.src = url;
  }

  destroy() {
    if (this.loadTimer) clearTimeout(this.loadTimer);
    if (this._onLoad) this.frame.removeEventListener("load", this._onLoad);
    this.generation = 0;
    this.frame.src = "";
    this._showState("loading");
  }
}

globalThis.NativePdfViewer = NativePdfViewer;