bookhoard/web/src/reader/comic/page-order.ts

// Page order presets for manga/comics
// Auto-detect Japanese vs Western reading order
// Feature Registration Pattern implementation

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

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

  context.events.on(
    "reader:loaded",
    (detail: { totalPages: number; pageNames: string[] }) => {
      state = createPageOrderState(detail.totalPages, detail.pageNames);
    },
  );

  context.events.on("page-order:set", (detail: { mode: PageOrderMode }) => {
    if (state) {
      setPageOrderMode(state, detail.mode, context);
    }
  });

  context.events.on("page-order:get", () => {
    if (state) {
      const order = getPageOrder(state);
      context.events.emit("page-order:current", { order });
    }
  });

  context.events.on(
    "page-order:reorder",
    (detail: { pageNumbers: number[] }) => {
      if (state) {
        const reordered = reorderPages(state, detail.pageNumbers);
        context.events.emit("page-order:reordered", { pages: reordered });
      }
    },
  );

  context.events.on(
    "page-order:display-number",
    (detail: { actualPage: number }) => {
      if (state) {
        const displayPage = getDisplayPageNumber(state, detail.actualPage);
        context.events.emit("page-order:display-page", { displayPage });
      }
    },
  );
}

type PageOrderMode = "auto" | "japanese" | "western";

interface PageOrderConfig {
  mode: PageOrderMode;
  detectedOrder: PageOrderMode;
  userOverride: boolean;
}

interface PageOrderState {
  config: PageOrderConfig;
  totalPages: number;
}

function detectPageOrder(pageNames: string[]): PageOrderMode {
  if (pageNames.length < 2) return "western";

  const firstPage = pageNames[0].toLowerCase();
  const lastPage = pageNames[pageNames.length - 1].toLowerCase();

  const hasFrontCover = /cover|front|001/.test(firstPage);
  const hasBackCover = /back|end|最后的/.test(lastPage);

  if (hasFrontCover && !hasBackCover) {
    return "western";
  }
  if (hasBackCover && !hasFrontCover) {
    return "japanese";
  }

  const chapterMatches = pageNames.filter((n) => /ch-\d+|chapter/i.test(n));
  if (chapterMatches.length > 0) {
    const firstChapter = chapterMatches[0];
    const pageNum = parseInt(firstChapter.match(/\d+/)?.[0] || "0");
    return pageNum > 0 ? "western" : "japanese";
  }

  return "western";
}

function createPageOrderState(
  totalPages: number,
  pageNames: string[],
): PageOrderState {
  const detectedOrder = detectPageOrder(pageNames);

  return {
    config: {
      mode: "auto",
      detectedOrder,
      userOverride: false,
    },
    totalPages,
  };
}

function setPageOrderMode(
  state: PageOrderState,
  mode: PageOrderMode,
  context: ReaderContext,
): PageOrderState {
  state.config = {
    ...state.config,
    mode,
    userOverride: mode !== "auto",
  };

  const order = getPageOrder(state);
  context.events.emit("page-order:changed", { mode, order });

  return state;
}

function getPageOrder(state: PageOrderState): PageOrderMode {
  if (state.config.mode === "auto") {
    return state.config.detectedOrder;
  }
  return state.config.mode;
}

function reorderPages(state: PageOrderState, pageNumbers: number[]): number[] {
  const order = getPageOrder(state);

  if (order === "japanese") {
    return [...pageNumbers].reverse();
  }

  return pageNumbers;
}

function getDisplayPageNumber(
  state: PageOrderState,
  actualPage: number,
): number {
  const order = getPageOrder(state);

  if (order === "japanese") {
    return state.totalPages - actualPage + 1;
  }

  return actualPage;
}