// 负责聊天区域滚动控制的通用方法，解耦 App.vue 中的 DOM 操作

type ScrollContext = {
  getMessagesAreaElement?: () => HTMLElement | null;
  getThinkingContentElement?: (blockId: string) => HTMLElement | null;
  chatToggleScrollLockState?: () => boolean;
  thinkingScrollLocks?: Map<string, boolean>;
  _setScrollingFlag?: (value: boolean) => void;
  autoScrollEnabled?: boolean;
  userScrolling?: boolean;
  isOutputActive?: () => boolean;
};

export function scrollToBottom(ctx: ScrollContext) {
  const messagesArea = ctx.getMessagesAreaElement?.();
  if (!messagesArea) {
    return;
  }

  const attempts = [0, 16, 60, 150, 320, 520]; // 多次尝试覆盖布局抖动/异步伸缩
  let cancelled = false;

  const perform = (idx: number) => {
    if (cancelled) return;
    if (ctx.userScrolling) {
      cancelled = true;
      if (typeof ctx._setScrollingFlag === 'function') {
        ctx._setScrollingFlag(false);
      }
      return;
    }

    if (idx === 0 && typeof ctx._setScrollingFlag === 'function') {
      ctx._setScrollingFlag(true);
    }

    messagesArea.scrollTop = messagesArea.scrollHeight;

    if (idx < attempts.length - 1) {
      setTimeout(() => perform(idx + 1), attempts[idx + 1] - attempts[idx]);
    } else if (typeof ctx._setScrollingFlag === 'function') {
      setTimeout(() => ctx._setScrollingFlag && ctx._setScrollingFlag(false), 40);
    }
  };

  perform(0);
}

export function conditionalScrollToBottom(ctx: ScrollContext) {
  const active = typeof ctx.isOutputActive === 'function' ? ctx.isOutputActive() : true;
  if (ctx.autoScrollEnabled === true && ctx.userScrolling === false && active) {
    scrollToBottom(ctx);
  }
}

export function toggleScrollLock(ctx: ScrollContext) {
  const active = typeof ctx.isOutputActive === 'function' ? ctx.isOutputActive() : true;

  // 没有模型输出时：允许点击，但不切换锁定，仅单次滚动到底部
  if (!active) {
    scrollToBottom(ctx);
    return ctx.autoScrollEnabled ?? false;
  }

  const nextState = ctx.chatToggleScrollLockState?.() ?? false;
  if (nextState) {
    scrollToBottom(ctx);
  }
  return nextState;
}

export function scrollThinkingToBottom(ctx: ScrollContext, blockId: string) {
  if (!blockId) {
    return;
  }
  if (!ctx.thinkingScrollLocks?.get(blockId)) {
    return;
  }
  const el = ctx.getThinkingContentElement?.(blockId);
  if (el) {
    el.scrollTop = el.scrollHeight;
  }
}