export function initAccessibilityWidget(): void {
  if (document.getElementById("accessibility-widget-container")) return;

  const container = document.createElement("div");
  container.id = "accessibility-widget-container";
  container.style.position = "fixed";
  container.style.zIndex = "9999";
  container.style.top = "0";
  container.style.left = "0";
  container.style.height = "100vh";
  container.style.width = "auto";

  document.body.appendChild(container);
  const shadow = container.attachShadow({ mode: "open" });

  const savedTop = localStorage.getItem("accessibility-hamburger-top");

  const style = document.createElement("style");
  style.textContent = `
        .toggle-button {
        width: 40px;
        height: 40px;
        border-radius: 0 8px 8px 0;
        background-color: #0000ff;
        color: white;
        font-size: 20px;
        border: none;
        cursor: grab;
        position: fixed;
        left: 0;
        z-index: 10000;
        transition: top 0.2s;
        }

        .popup-panel {
        position: fixed;
        top: 0;
        left: 0;
        height: 100vh;
        width: 50vw;
        max-width: 400px;
        background: white;
        box-shadow: 2px 0 10px rgba(0,0,0,0.3);
        padding: 20px;
        transform: translateX(-100%);
        transition: transform 0.3s ease-in-out;
        z-index: 9999;
        overflow-y: auto;
        }

        .popup-panel.open {
        transform: translateX(0);
        }

        .accessibility-controls button,
        .button {
        padding: 8px 12px;
        margin: 6px 4px;
        background-color: #0000ff;
        color: white;
        border: none;
        border-radius: 4px;
        font-size: 16px;
        cursor: pointer;
        }

        .accessibility-controls button:hover {
        background-color: #0000cc;
        }

        .accessibility-controls {
        margin-top: 10px;
        }
    `;

  const toggleBtn = document.createElement("button");
  toggleBtn.className = "toggle-button";
  toggleBtn.innerHTML = `
            <svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
                <path d="M12.4575 14.0572V9.02866M12.4575 14.0572H11.0861M12.4575 14.0572L15.2004 20.0001M12.4575 9.02866H11.0861M12.4575 9.02866L13.7381 8.81523C14.7101 8.65322 15.6618 8.38692 16.5768 8.02094L17.4861 7.65723M11.0861 14.0572V9.02866M11.0861 14.0572L7.88608 20.0001M11.0861 9.02866L9.97052 8.84273C8.89172 8.66293 7.84586 8.32283 6.86764 7.83372L6.51465 7.65723" stroke="white" stroke-width="2.28571" stroke-linecap="round" stroke-linejoin="round"/>
                <path d="M12.7309 4.91429C12.7309 5.41923 12.3216 5.82857 11.8166 5.82857C11.3117 5.82857 10.9023 5.41923 10.9023 4.91429C10.9023 4.40934 11.3117 4 11.8166 4C12.3216 4 12.7309 4.40934 12.7309 4.91429Z" fill="white" stroke="white" stroke-width="2.28571" stroke-linecap="round" stroke-linejoin="round"/>
            </svg>
        `;

  toggleBtn.style.top = savedTop ? `${savedTop}px` : "20px";

  const panel = document.createElement("div");
  panel.className = "popup-panel";
  panel.innerHTML = `
        <div class="accessibility-controls" id="controls">
        <h2>Accessibility Options</h2>
        <div>
            <button id="btn-increase">A+</button>
            <button id="btn-decrease">A-</button>
        </div>
        <div>
            <button id="btn-underline">Underline Links</button>
        </div>
        <button id="btn-reset" class="button">Reset</button>
        </div>
    `;

  shadow.appendChild(style);
  shadow.appendChild(toggleBtn);
  shadow.appendChild(panel);

  // Panel Toggle
  let isOpen = false;
  toggleBtn.addEventListener("click", () => {
    isOpen = !isOpen;
    panel.classList.toggle("open", isOpen);

    if (isOpen) {
      toggleBtn.style.top = "20px";
      toggleBtn.style.cursor = "default";
    } else {
      toggleBtn.style.cursor = "grab";
      const saved = localStorage.getItem("accessibility-hamburger-top");
      toggleBtn.style.top = saved ? `${saved}px` : "20px";
    }
  });

  // Font Size Control
  const html = document.documentElement;
  const step = 2;
  const minSize = 12;
  const maxSize = 32;
  const defaultSize = 16;

  const savedFontSize = localStorage.getItem("accessibility-font-size");
  if (savedFontSize) {
    const size = parseFloat(savedFontSize);
    document.querySelectorAll<HTMLElement>("body, body *").forEach((el) => {
      el.style.fontSize = `${size}px`;
    });
  }

  function changeFontSize(direction: "increase" | "decrease") {
    document.querySelectorAll<HTMLElement>("body, body *").forEach((el) => {
      const currentSize = parseFloat(window.getComputedStyle(el).fontSize);
      if (isNaN(currentSize)) return;

      let newSize = currentSize;
      if (direction === "increase" && currentSize < maxSize) newSize += step;
      else if (direction === "decrease" && currentSize > minSize)
        newSize -= step;

      el.style.fontSize = `${newSize}px`;
      localStorage.setItem("accessibility-font-size", `${newSize}`);
    });
  }

  function resetFontSize() {
    html.style.fontSize = `${defaultSize}px`;
    document.querySelectorAll<HTMLElement>("body, body *").forEach((el) => {
      el.style.fontSize = "";
    });
  }

  // Underline Feature
  let underlineActive =
    localStorage.getItem("accessibility-underline") === "true";
  function applyUnderline() {
    document.querySelectorAll<HTMLElement>("a, .link, #link").forEach((el) => {
      el.style.textDecoration = underlineActive ? "underline" : "none";
    });
  }
  if (underlineActive) applyUnderline();

  panel.querySelector("#btn-underline")?.addEventListener("click", () => {
    underlineActive = !underlineActive;
    localStorage.setItem("accessibility-underline", underlineActive.toString());
    applyUnderline();
  });

  const observer = new MutationObserver(() => {
    if (underlineActive) applyUnderline();
  });
  observer.observe(document.body, { childList: true, subtree: true });

  panel
    .querySelector("#btn-increase")
    ?.addEventListener("click", () => changeFontSize("increase"));
  panel
    .querySelector("#btn-decrease")
    ?.addEventListener("click", () => changeFontSize("decrease"));
  panel.querySelector("#btn-reset")?.addEventListener("click", () => {
    resetFontSize();
    underlineActive = false;
    applyUnderline();
    localStorage.removeItem("accessibility-underline");
    localStorage.removeItem("accessibility-font-size");
  });

  // Drag Only When Closed
  let isDragging = false;
  let startY = 0;
  let startTop = 0;

  toggleBtn.addEventListener("mousedown", (e) => {
    if (isOpen) return;
    isDragging = true;
    startY = e.clientY;
    startTop = toggleBtn.getBoundingClientRect().top;
    document.body.style.userSelect = "none";
  });

  document.addEventListener("mousemove", (e) => {
    if (!isDragging || isOpen) return;
    const offsetY = e.clientY - startY;
    let newTop = startTop + offsetY;

    const maxTop = window.innerHeight - 50;
    newTop = Math.max(0, Math.min(maxTop, newTop));

    toggleBtn.style.top = `${newTop}px`;
  });

  document.addEventListener("mouseup", () => {
    if (isDragging) {
      isDragging = false;
      document.body.style.userSelect = "";
      const rect = toggleBtn.getBoundingClientRect();
      localStorage.setItem("accessibility-hamburger-top", `${rect.top}`);
    }
  });
}