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export interface Tab {
readonly conversationId: string;
readonly model: string;
readonly title: string;
}
export interface TabsState {
readonly tabs: readonly Tab[];
readonly activeConversationId: string | null;
}
const DEFAULT_TITLE = "New chat";
const DEFAULT_MAX_TITLE_LENGTH = 40;
export function initialState(persisted?: TabsState): TabsState {
if (persisted !== undefined) return persisted;
return { tabs: [], activeConversationId: null };
}
export function newDraft(state: TabsState): TabsState {
return { ...state, activeConversationId: null };
}
export function createTab(state: TabsState, tab: Tab): TabsState {
const exists = state.tabs.some((t) => t.conversationId === tab.conversationId);
const tabs = exists ? state.tabs : [...state.tabs, tab];
return { tabs, activeConversationId: tab.conversationId };
}
export function selectTab(state: TabsState, conversationId: string): TabsState {
return { ...state, activeConversationId: conversationId };
}
export function closeTab(state: TabsState, conversationId: string): TabsState {
const idx = state.tabs.findIndex((t) => t.conversationId === conversationId);
if (idx === -1) return state;
const tabs = state.tabs.filter((t) => t.conversationId !== conversationId);
if (state.activeConversationId !== conversationId) {
return { tabs, activeConversationId: state.activeConversationId };
}
if (tabs.length === 0) {
return { tabs, activeConversationId: null };
}
// prefer previous tab, else next
const neighborIdx = idx > 0 ? idx - 1 : 0;
const neighbor = tabs[neighborIdx];
return { tabs, activeConversationId: neighbor?.conversationId ?? null };
}
export function setModel(state: TabsState, conversationId: string, model: string): TabsState {
const tabs = state.tabs.map((t) => (t.conversationId === conversationId ? { ...t, model } : t));
return { tabs, activeConversationId: state.activeConversationId };
}
export function setTitle(state: TabsState, conversationId: string, title: string): TabsState {
const tabs = state.tabs.map((t) => (t.conversationId === conversationId ? { ...t, title } : t));
return { tabs, activeConversationId: state.activeConversationId };
}
export function activeTab(state: TabsState): Tab | null {
if (state.activeConversationId === null) return null;
return state.tabs.find((t) => t.conversationId === state.activeConversationId) ?? null;
}
export interface ScrollMetrics {
readonly scrollLeft: number;
readonly clientWidth: number;
readonly scrollWidth: number;
}
const STUCK_EPSILON = 1;
/**
* True when a right-pinned sticky element is floating over scrolled content — the
* strip overflows horizontally AND is not scrolled fully to the right. When it is
* at rest (no overflow, or scrolled to the end so it sits at its natural position)
* this returns false. Pure: layout measurements in, boolean out.
*/
export function isStuckToEnd(m: ScrollMetrics): boolean {
const overflows = m.scrollWidth > m.clientWidth + STUCK_EPSILON;
const notAtEnd = m.scrollLeft + m.clientWidth < m.scrollWidth - STUCK_EPSILON;
return overflows && notAtEnd;
}
export function deriveTitle(message: string, max: number = DEFAULT_MAX_TITLE_LENGTH): string {
const trimmed = message.trim().replace(/\s+/g, " ");
if (trimmed.length === 0) return DEFAULT_TITLE;
if (trimmed.length <= max) return trimmed;
return `${trimmed.slice(0, max)}\u2026`;
}
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