/* nav-20251012.js
   作者：ChatGPT（为你量身定制）
   功能：按键/触摸导航 —— 支持：入口 /main/ /commitee-list/ /speech/x.html
   将此文件在 /20251012/ 相关页面引入即可。
*/

(function () {
  "use strict";

  // ========== 配置 ==========
  const CONFIG = {
    // 如果没有在 URL 中检测到 8 位日期段，可以在这里硬编码入口（以 '/' 开头并以 '/' 结尾）
    // 例如 '/20251012/'。若保留 null 会自动从 location.pathname 中寻找第一个 8 位数字段。
    FORCE_BASE: null, // '/20251012/', or null to auto-detect

    // 如果页面中没有可被自动发现的 speech/x.html 链接，设置一个最大页数（整数 > 0）
    FALLBACK_SPEECH_COUNT: 3,

    // 当在最后一页按 "下一页" 时的行为： 'wrap' | 'toRoot' | 'noop'
    ON_FINAL_NEXT: "toRoot", // 推荐 'toRoot'（回到入口）或 'wrap'（回到第一篇）

    // 是否使用 history.pushState 做平滑跳转（默认 true），设 false 则使用 location.href 真正跳转
    USE_PUSHSTATE: true,

    // 显示键位提示面板（true/false）
    SHOW_HELP_OVERLAY: true,
  };

  // ========== 工具函数 ==========
  function normalizePath(p) {
    if (!p) return "/";
    // ensure starts with /
    if (!p.startsWith("/")) p = "/" + p;
    // ensure trailing slash for directory-like paths, except for filenames like .html
    if (!p.endsWith("/") && !p.match(/\.\w+$/)) p = p + "/";
    return p;
  }

  function detectBaseFromPath() {
    if (CONFIG.FORCE_BASE) return normalizePath(CONFIG.FORCE_BASE);
    // find first /YYYYMMDD/ in pathname
    const m = location.pathname.match(/\/(\d{8})(?:\/|$)/);
    if (m) return `/${m[1]}/`;
    // fallback: try first path segment if looks like a date
    const segs = location.pathname.split("/").filter(Boolean);
    if (segs.length && /^\d{8}$/.test(segs[0])) return `/${segs[0]}/`;
    // last resort
    return "/20251012/";
  }

  const BASE = detectBaseFromPath();
  const MAIN = normalizePath(BASE + "main");
  const COMMITEE = normalizePath(BASE + "commitee-list");
  const SPEECH_PREFIX = normalizePath(BASE + "speech"); // like '/20251012/speech/'

  function isRoot(pathname) {
    const p = normalizePath(pathname);
    return (
      p === normalizePath(BASE) || p === normalizePath(BASE.replace(/\/$/, ""))
    );
  }
  function isMain(pathname) {
    return normalizePath(pathname) === MAIN;
  }
  function isCommitee(pathname) {
    return normalizePath(pathname) === COMMITEE;
  }
  function isSpeech(pathname) {
    // match /.../speech/x.html or /.../speech/x (with or without trailing slash)
    const m = pathname.match(/\/speech\/(\d+)(?:\.html)?(?:\/|$)/);
    return m ? parseInt(m[1], 10) : null;
  }

  // detect available speech pages by scanning <a> tags in the current document
  function detectSpeechPagesFromLinks() {
    const anchors = Array.from(document.querySelectorAll("a[href]"));
    const nums = new Set();
    const basePattern = new RegExp(
      "^" + SPEECH_PREFIX.replace(/\/$/, "\\/") + "(\\d+)(?:\\.html)?(?:\\/?$)"
    );
    anchors.forEach((a) => {
      try {
        const href = a.getAttribute("href");
        // convert relative -> absolute path (only pathname part)
        const tmp = new URL(href, location.href);
        const path = tmp.pathname;
        const m = path.match(/\/speech\/(\d+)(?:\.html)?(?:\/|$)/);
        if (m) nums.add(parseInt(m[1], 10));
      } catch (e) {
        // ignore
      }
    });
    if (nums.size === 0) return null;
    return Array.from(nums).sort((a, b) => a - b);
  }

  // Determine speech pages list
  const detectedSpeechList = detectSpeechPagesFromLinks();
  let SPEECH_LIST = null; // array of numbers like [1,2,3]
  if (detectedSpeechList && detectedSpeechList.length > 0) {
    SPEECH_LIST = detectedSpeechList;
  } else {
    // fallback to 1..FALLBACK_SPEECH_COUNT
    const n = Math.max(1, Math.floor(CONFIG.FALLBACK_SPEECH_COUNT));
    SPEECH_LIST = Array.from({ length: n }, (_, i) => i + 1);
  }

  function speechUrl(n) {
    // return '/20251012/speech/1.html'
    return `${SPEECH_PREFIX}${n}.html`;
  }

  function goTo(url, opts = {}) {
    const usePush = CONFIG.USE_PUSHSTATE && opts.push !== false;
    if (usePush) {
      try {
        history.pushState({}, "", url);
        // optionally fetch and replace content (here we just reload to keep things simple)
        // best practice: make this an SPA; for now do a full location.assign to ensure page loads.
        location.assign(url);
      } catch (e) {
        location.href = url;
      }
    } else {
      location.href = url;
    }
  }

  // ========== Navigation logic ==========
  function handleNext() {
    const pathname = location.pathname;
    const curSpeech = isSpeech(pathname);
    if (isRoot(pathname)) {
      // entry -> main
      goTo(MAIN);
      return;
    }
    if (isMain(pathname)) {
      goTo(COMMITEE);
      return;
    }
    if (isCommitee(pathname)) {
      // go to first speech (if exists) else go to first fallback
      const first = SPEECH_LIST[0];
      goTo(speechUrl(first));
      return;
    }
    if (curSpeech) {
      // find index in SPEECH_LIST
      const idx = SPEECH_LIST.indexOf(curSpeech);
      if (idx >= 0 && idx < SPEECH_LIST.length - 1) {
        goTo(speechUrl(SPEECH_LIST[idx + 1]));
      } else {
        // at final speech
        if (CONFIG.ON_FINAL_NEXT === "wrap") {
          goTo(speechUrl(SPEECH_LIST[0]));
        } else if (CONFIG.ON_FINAL_NEXT === "toRoot") {
          goTo(BASE);
        } else {
          // noop
        }
      }
      return;
    }
    // default fallback: go to main
    goTo(MAIN);
  }

  function handlePrev() {
    const pathname = location.pathname;
    const curSpeech = isSpeech(pathname);
    if (isRoot(pathname)) {
      // nothing to do
      return;
    }
    if (isMain(pathname)) {
      goTo(BASE);
      return;
    }
    if (isCommitee(pathname)) {
      goTo(MAIN);
      return;
    }
    if (curSpeech) {
      const idx = SPEECH_LIST.indexOf(curSpeech);
      if (idx > 0) {
        goTo(speechUrl(SPEECH_LIST[idx - 1]));
      } else {
        // first speech -> back to commitee-list
        goTo(COMMITEE);
      }
      return;
    }
    // default fallback: go to base
    goTo(BASE);
  }

  // ========== Key & Touch handling ==========
  function onKey(e) {
    // Normalize some keys:
    // Enter -> Next
    // ArrowRight / '>' / '.' -> Next
    // ArrowLeft / '<' / ',' -> Prev
    const k = e.key;
    if (k === "Enter") {
      e.preventDefault();
      handleNext();
      return;
    }
    if (k === "ArrowRight" || k === "Right") {
      e.preventDefault();
      handleNext();
      return;
    }
    if (k === "ArrowLeft" || k === "Left") {
      e.preventDefault();
      handlePrev();
      return;
    }
    // characters '>' and '<' (depending on keyboard)
    if (k === ">" || k === ".") {
      e.preventDefault();
      handleNext();
      return;
    }
    if (k === "<" || k === ",") {
      e.preventDefault();
      handlePrev();
      return;
    }

    // optional: 'h' toggles help overlay
    if (k === "h" || k === "H") {
      toggleHelpOverlay();
    }
  }

  // Basic touch swipe (horizontal)
  let touchStartX = null;
  function onTouchStart(e) {
    if (e.touches && e.touches.length === 1) {
      touchStartX = e.touches[0].clientX;
    }
  }
  function onTouchEnd(e) {
    if (!touchStartX) return;
    const endX = (e.changedTouches && e.changedTouches[0].clientX) || null;
    if (endX === null) {
      touchStartX = null;
      return;
    }
    const dx = endX - touchStartX;
    const threshold = 50; // pixels
    if (dx > threshold) {
      // swipe right -> Prev
      handlePrev();
    } else if (dx < -threshold) {
      // swipe left -> Next
      handleNext();
    }
    touchStartX = null;
  }

  // ========== UI overlay/help ==========
  let overlayEl = null;
  function createHelpOverlay() {
    if (!CONFIG.SHOW_HELP_OVERLAY) return;
    overlayEl = document.createElement("div");
    overlayEl.id = "nav-help-overlay";
    overlayEl.style.position = "fixed";
    overlayEl.style.right = "16px";
    overlayEl.style.bottom = "16px";
    overlayEl.style.zIndex = 9999;
    overlayEl.style.padding = "10px 12px";
    overlayEl.style.borderRadius = "8px";
    overlayEl.style.boxShadow = "0 6px 20px rgba(0,0,0,0.2)";
    overlayEl.style.background = "rgba(255,255,255,0.95)";
    overlayEl.style.fontFamily =
      'system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue"';
    overlayEl.style.fontSize = "13px";
    overlayEl.style.color = "#111";
    overlayEl.style.border = "1px solid rgba(0,0,0,0.06)";
    overlayEl.style.maxWidth = "260px";
    overlayEl.style.lineHeight = "1.3";
    overlayEl.innerHTML = `
      <strong>导航提示</strong><br/>
      Enter / → / '>' : 下一页<br/>
      ← / '<' : 上一页<br/>
      H : 显示/隐藏本提示<br/>
      支持触摸左右滑动（移动端）
    `;
    overlayEl.style.cursor = "pointer";
    overlayEl.title = "点击隐藏/显示";
    overlayEl.addEventListener("click", toggleHelpOverlay);
    document.body.appendChild(overlayEl);
  }

  function toggleHelpOverlay() {
    if (!overlayEl) {
      createHelpOverlay();
      return;
    }
    if (overlayEl.style.display === "none") overlayEl.style.display = "";
    else overlayEl.style.display = "none";
  }

  // ========== Init ==========
  function init() {
    // Attach handlers
    window.addEventListener("keydown", onKey, { passive: false });
    window.addEventListener("touchstart", onTouchStart, { passive: true });
    window.addEventListener("touchend", onTouchEnd, { passive: true });

    // pushState popstate handling: when user clicks back/forward, allow normal navigation (no extra handling needed)
    window.addEventListener("popstate", () => {
      // no-op: browser handles location; you could re-run UI update hooks here if needed
    });

    // create help overlay
    if (CONFIG.SHOW_HELP_OVERLAY) createHelpOverlay();

    // Add small visual helper arrows (optional)
    addOnScreenArrows();
  }

  function addOnScreenArrows() {
    // minimal left/right arrow buttons for mouse users
    const left = document.createElement("button");
    left.textContent = "←";
    left.setAttribute("aria-label", "上一页");
    styleTinyArrow(left, "left");
    left.addEventListener("click", handlePrev);

    const right = document.createElement("button");
    right.textContent = "→";
    right.setAttribute("aria-label", "下一页");
    styleTinyArrow(right, "right");
    right.addEventListener("click", handleNext);

    document.body.appendChild(left);
    document.body.appendChild(right);
  }

  function styleTinyArrow(btn, which) {
    btn.style.position = "fixed";
    btn.style.zIndex = 9998;
    btn.style.top = "50%";
    btn.style.transform = "translateY(-50%)";
    btn.style[which === "left" ? "left" : "right"] = "8px";
    btn.style.width = "40px";
    btn.style.height = "40px";
    btn.style.borderRadius = "6px";
    btn.style.border = "1px solid rgba(0,0,0,0.08)";
    btn.style.background = "rgba(255,255,255,0.9)";
    btn.style.boxShadow = "0 6px 20px rgba(0,0,0,0.08)";
    btn.style.cursor = "pointer";
    btn.style.fontSize = "18px";
    btn.style.lineHeight = "36px";
    btn.style.padding = "0";
    btn.style.display = "flex";
    btn.style.alignItems = "center";
    btn.style.justifyContent = "center";
  }

  // run
  init();

  // expose for debugging
  window._eventNav = {
    BASE,
    MAIN,
    COMMITEE,
    SPEECH_PREFIX,
    SPEECH_LIST,
    handleNext,
    handlePrev,
  };
})();