// Different viewing modes for ebooks
// Feature Registration Pattern implementation

import { ReaderContext } from "../core/reader-context";

export function init(context: ReaderContext): void {
  let state: ViewModeState | null = null;

  context.events.on("reader:loaded", (detail: { container: HTMLElement }) => {
    state = { currentMode: "paginated", currentPage: 1 };
    setViewMode(detail.container, "paginated");
  });

  context.events.on("view-mode:set", (detail: { mode: ViewMode }) => {
    if (state && context.elements.readerContent) {
      state.currentMode = detail.mode;
      setViewMode(context.elements.readerContent, detail.mode);
      context.events.emit("view-mode:changed", { mode: detail.mode });
    }
  });

  context.events.on("view-mode:get", () => {
    if (state) {
      context.events.emit("view-mode:current", state);
    }
  });

  context.events.on("pagination:go-to-page", (detail: { page: number }) => {
    if (state && context.elements.readerContent) {
      state.currentPage = detail.page;
      goToPage(context.elements.readerContent, detail.page);
      context.events.emit("pagination:page-changed", { page: detail.page });
    }
  });
}

type ViewMode = "paginated" | "scrolled" | "single-column" | "double-column";

interface ViewModeState {
  currentMode: ViewMode;
  currentPage: number;
}

function setViewMode(container: HTMLElement, mode: ViewMode): void {
  const content = container.querySelector(".ebook-content");
  if (!content) return;

  const element = content as HTMLElement;

  element.classList.remove(
    "paginated",
    "scrolled",
    "single-column",
    "double-column",
  );

  switch (mode) {
    case "paginated":
      applyPaginatedMode(element);
      break;
    case "scrolled":
      applyScrolledMode(element);
      break;
    case "single-column":
      applySingleColumn(element);
      break;
    case "double-column":
      applyDoubleColumn(element);
      break;
  }
}

function applyPaginatedMode(element: HTMLElement): void {
  element.classList.add("paginated");
  // Set up for CSS columns
  element.style.height = "calc(100vh - 120px)";
  element.style.overflowY = "auto";
  element.style.overflowX = "hidden";
  element.style.columnCount = "1";
  element.style.columnFill = "auto";
  element.style.columnGap = "0";
  element.style.position = "relative";
  // Inject CSS for CSS column pagination
  injectPaginatedStyles();
}

function injectPaginatedStyles(): void {
  // Remove existing injected styles if any
  const existing = document.getElementById("paginated-styles");
  existing?.remove();

  const style = document.createElement("style");
  style.id = "paginated-styles";
  style.textContent = `
    .paginated {
      height: calc(100vh - 120px) !important;
      overflow-y: auto !important;
      overflow-x: hidden !important;
      column-fill: auto !important;
      column-count: 1 !important;
      column-gap: 0 !important;
      position: relative !important;
    }
    .paginated > * {
      max-width: 100%;
      column-fill: auto;
    }
    .paginated .ebook-content {
      height: auto !important;
      min-height: 100%;
    }
  `;
  document.head.appendChild(style);
}

function applyScrolledMode(element: HTMLElement): void {
  element.classList.add("scrolled");

  element.style.height = "auto";
  element.style.overflowY = "auto";
  element.style.columnCount = "1";
}

function applySingleColumn(element: HTMLElement): void {
  element.classList.add("single-column");

  element.style.columnCount = "1";
  element.style.columnGap = "0";
  element.style.maxWidth = "800px";
  element.style.margin = "0 auto";
}

function applyDoubleColumn(element: HTMLElement): void {
  element.classList.add("double-column");

  element.style.columnCount = "2";
  element.style.columnGap = "60px";
  element.style.columnRule = "1px solid var(--text-secondary)";
  element.style.maxWidth = "1400px";
  element.style.margin = "0 auto";
}

function goToPage(container: HTMLElement, pageNumber: number): void {
  const content = container.querySelector(".ebook-content") as HTMLElement;
  if (!content) return;
  const totalPages = getTotalPageCount(container);
  const targetPage = Math.min(Math.max(1, pageNumber), totalPages);
  const viewportHeight = window.innerHeight - 120;
  const scrollTop = (targetPage - 1) * viewportHeight;
  content.scrollTo({
    top: scrollTop,
    behavior: "smooth",
  });
}

function getTotalPageCount(container: HTMLElement): number {
  const content = container.querySelector(".ebook-content") as HTMLElement;
  if (!content) return 1;
  const viewportHeight = window.innerHeight - 120;
  const contentHeight = content.scrollHeight;
  return Math.max(1, Math.ceil(contentHeight / viewportHeight));
}

export function getCurrentViewMode(container: HTMLElement): ViewMode {
  const content = container.querySelector(".ebook-content") as HTMLElement;
  if (!content) return "paginated";

  if (content.classList.contains("paginated")) return "paginated";
  if (content.classList.contains("scrolled")) return "scrolled";
  if (content.classList.contains("single-column")) return "single-column";
  if (content.classList.contains("double-column")) return "double-column";

  return "paginated";
}