// Modified from https://github.com/mrhuo/image-viewer
class ImageViewer {
  constructor(options = {}) {
    // State variables
    this.targetSelector = "#gallery img";
    this.currentScale = 1.0;
    this.maxScale = 8;
    this.minScale = 0.5;
    this.isDragging = false;
    this.hasMoved = false;
    this.downX = 0;
    this.downY = 0;
    this.startX = 0;
    this.startY = 0;
    this.currentX = 0;
    this.currentY = 0;
    this.imageList = [];
    this.currentIndex = -1;

    window.scrollTo(0, 0);

    this.preview = document.getElementById("preview");
    this.sidebar = document.getElementById("sidebar");
    this.imageWrapper = document.getElementById("image-wrapper");
    this.previewImg = document.getElementById("preview-img");
    this.navControls = document.getElementById("nav-controls");
    this.prevBtn = document.getElementById("prev-btn");
    this.nextBtn = document.getElementById("next-btn");
    this.imageCaption = document.getElementById("image-caption");
    this.imageIndex = document.getElementById("image-index");
    this.imageInfo = document.getElementById("image-info");
    this.downloadBtn = document.getElementById("download-btn");
    this.toggleSidebarBtn = document.getElementById("toggle-sidebar-btn");
    this.sidebarContent = document.getElementById("sidebar-content");
    this.sidebarImageName = document.getElementById("img-name");
    this.sidebarImageAlt = document.getElementById("img-alt");

    if (window.innerWidth > 1600) {
      this.sidebar.style.width = "30vw";
    }

    this.imageList = Array.from(document.querySelectorAll(this.targetSelector));
    this.observeImages();
    this.bindClickEvents(this.imageList);

    this.imageWrapper.addEventListener("wheel", this.handleWheel.bind(this));
    this.imageWrapper.addEventListener("mousedown", this.startDrag.bind(this));
    this.prevBtn.addEventListener("click", this.showPrevImage.bind(this));
    this.nextBtn.addEventListener("click", this.showNextImage.bind(this));
    document.addEventListener("keydown", this.handleKeyDown.bind(this));
    this.downloadBtn.addEventListener("click", this.downloadImage.bind(this));
    this.toggleSidebarBtn.addEventListener("click", this.toggleSidebar.bind(this));
  }

  downloadImage() {
    const link = document.createElement("a");
    link.download = this.previewImg.name;
    link.href = this.previewImg.src;
    link.click();
    link.remove();
  }

  toggleSidebar() {
    if (this.sidebar.style.width) {
      this.sidebar.style.width = "";
      setTimeout(() => {
        this.sidebarContent.style.display = "none";
      }, 100);
    } else {
      this.sidebar.style.width = "30vw";
      setTimeout(() => {
        this.sidebarContent.style.display = "block";
      }, 100);
    }
  }

  bindDragEvents() {
    this.imageWrapper.addEventListener("mousemove", this.doDrag.bind(this));
    this.imageWrapper.addEventListener("mouseup", this.endDrag.bind(this));
    this.imageWrapper.addEventListener("mouseleave", this.endDrag.bind(this));
  }

  unbindDragEvents() {
    this.imageWrapper.removeEventListener("mousemove", this.doDrag.bind(this));
    this.imageWrapper.removeEventListener("mouseup", this.endDrag.bind(this));
    this.imageWrapper.removeEventListener("mouseleave",this.endDrag.bind(this));
  }

  resetTransform() {
    this.currentScale = 1.0;
    this.currentX = 0;
    this.currentY = 0;
    this.updateImageTransform();
  }

  updateImageTransform() {
    this.previewImg.style.transform = `
      translate(${this.currentX}px, ${this.currentY}px)
      scale(${this.currentScale})
    `;
  }

  showImageByIndex(index) {
    if (index < 0 || index >= this.imageList.length) {
      return;
    }

    if (index === this.imageList.length - 7) {
      loadMoreImages();
    }

    this.currentIndex = index;
    const img = this.imageList[this.currentIndex];
    this.resetTransform();

    const highResSrc = img.dataset.highres;
    const lowResSrc = img.src;
    const altText = img.alt || "";

    // 先显示小图
    this.previewImg.src = lowResSrc;
    this.previewImg.alt = altText;
    this.updateInfoBar(altText);
    this.updateNavButtons();

    this.previewImg.onload = () => {
      // 如果有高分辨率图片，异步加载并在完成后替换
      if (highResSrc && highResSrc !== lowResSrc) {
        this.loadHighResImage(altText, highResSrc);
      }
    };

    this.previewImg.onerror = () => {
      this.updateInfoBar("Failed to load image");
    };

    this.preview.style.display = "flex";
    document.body.style.overflow = "hidden";
  }

  loadHighResImage(altText, highResSrc) {
    this.imageIndex.textContent += "　loading...";

    const loadingIndex = this.currentIndex;
    const highResImg = new Image();

    highResImg.onload = () => {
      // Remove current onload handler to avoid duplicate triggers
      this.previewImg.onload = null;

      // Check if the image index has changed
      if (this.currentIndex != loadingIndex) return;

      // High-resolution image loaded, replace current image
      this.previewImg.src = highResSrc;

      this.updateInfoBar(altText);
    };

    highResImg.onerror = () => {
      if (this.currentIndex != loadingIndex) return;
      this.updateInfoBar("Failed to load high res image");
    };

    // Start loading high-resolution image
    highResImg.src = highResSrc;
  }

  updateInfoBar(altText) {
    this.imageCaption.textContent = altText;
    this.imageIndex.textContent = `${this.currentIndex + 1} / ${
      this.imageList.length
    }`;
    this.sidebarImageName.textContent = this.imageList[this.currentIndex].name;
    this.sidebarImageAlt.textContent = this.imageList[this.currentIndex].alt;
  }

  updateNavButtons() {
    this.prevBtn.style.opacity = this.currentIndex <= 0 ? "0" : "1";
    this.prevBtn.style.pointerEvents = this.currentIndex <= 0 ? "none" : "auto";

    this.nextBtn.style.opacity =
      this.currentIndex >= this.imageList.length - 1 ? "0" : "1";
    this.nextBtn.style.pointerEvents =
      this.currentIndex >= this.imageList.length - 1 ? "none" : "auto";
  }

  openPreview(e, img) {
    e.stopPropagation();
    const index = this.imageList.indexOf(img);
    if (index !== -1) {
      this.showImageByIndex(index);
    }
  }

  closePreview() {
    this.preview.style.display = "none";
    document.body.style.overflow = "";
  }

  showNextImage() {
    if (this.currentIndex < this.imageList.length - 1) {
      this.showImageByIndex(this.currentIndex + 1);
    }
  }

  showPrevImage() {
    if (this.currentIndex > 0) {
      this.showImageByIndex(this.currentIndex - 1);
    }
  }

  handleKeyDown(e) {
    if (this.preview.style.display !== "flex") return;

    switch (e.key) {
      case "Escape":
        this.closePreview();
        break;
      case "ArrowRight":
        this.showNextImage();
        break;
      case "ArrowLeft":
        this.showPrevImage();
        break;
      case "b":
        if (e.ctrlKey) {
          this.toggleSidebar();
        }
        break;
    }
  }

  handleWheel(e) {
    e.preventDefault();
    const delta = e.deltaY > 0 ? -0.1 : 0.1;
    const newScale = this.currentScale + delta;

    if (newScale >= this.minScale && newScale <= this.maxScale) {
      const ratio = newScale / this.currentScale;
      const rect = this.imageWrapper.getBoundingClientRect();

      const offsetX = e.clientX - (rect.left + rect.width / 2);
      const offsetY = e.clientY - (rect.top + rect.height / 2);

      this.currentX = offsetX * (1 - ratio) + this.currentX * ratio;
      this.currentY = offsetY * (1 - ratio) + this.currentY * ratio;
      this.currentScale = newScale;
      this.updateImageTransform();
    }
  }

  startDrag(e) {
    if (e.button !== 0) return; // Only left button
    e.preventDefault();
    e.stopPropagation();

    this.isDragging = true;
    this.hasMoved = false;
    this.startX = e.clientX - this.currentX;
    this.startY = e.clientY - this.currentY;
    this.downX = e.clientX;
    this.downY = e.clientY;
    this.imageWrapper.classList.add("dragging");
    this.navControls.style.display = "none";
    this.bindDragEvents();
  }

  doDrag(e) {
    if (!this.isDragging) return;
    e.preventDefault();
    e.stopPropagation();
    const dx = e.clientX - this.downX;
    const dy = e.clientY - this.downY;
    if (Math.abs(dx) > 2 || Math.abs(dy) > 2) {
      this.hasMoved = true;
    }
    this.currentX = e.clientX - this.startX;
    this.currentY = e.clientY - this.startY;
    this.updateImageTransform();
  }

  endDrag(e) {
    if (!this.isDragging) return;
    if (e) {
      e.stopPropagation();
    }

    this.isDragging = false;
    this.imageWrapper.classList.remove("dragging");
    this.unbindDragEvents();
    setTimeout(() => {
      if (!this.isDragging) {
        this.navControls.style.display = "flex";
      }
    }, 500)

    if (!this.hasMoved) {
      this.closePreview();
    }
  }

  observeImages() {
    this.observer = new MutationObserver((mutations) => {
      mutations.forEach((mutation) => {
        mutation.addedNodes.forEach((node) => {
          let imgsToProcess = [];
          if (node.tagName === "IMG" && node.matches(this.targetSelector)) {
            imgsToProcess.push(node);
          } else if (node.querySelectorAll) {
            imgsToProcess = Array.from(
              node.querySelectorAll(this.targetSelector)
            );
          }

          imgsToProcess.forEach((img) => {
            if (!this.imageList.includes(img)) {
              this.imageList.push(img);
              this.bindClickEvents([img]);
            }
          });
        });

        if (mutation.removedNodes.length > 0) {
          this.imageList = this.imageList.filter((img) =>
            document.body.contains(img)
          );
        }
      });
    });
    this.observer.observe(document.body, { childList: true, subtree: true });
  }

  bindClickEvents(images) {
    images.forEach((img) => {
      if (!img.dataset.imageViewerBound) {
        img.addEventListener("click", (e) => this.openPreview(e, img));
        img.dataset.imageViewerBound = "true";
        img.style.cursor = "zoom-in";
      }
    });
  }
}

document.addEventListener('DOMContentLoaded', () => { new ImageViewer({}) });