import { IMentionEntry } from '../../api/mentions';

let mentions: IMentionEntry[] = [];
const listeners = new Set<() => void>();

const emit = () => { for(const l of listeners) l(); };

export const subscribeMentions = (onChange: () => void): (() => void) =>
{
    listeners.add(onChange);
    return () => { listeners.delete(onChange); };
};

export const getMentionsSnapshot = (): ReadonlyArray<IMentionEntry> => mentions;

export const getUnreadCount = (): number => mentions.reduce((n, m) => n + (m.read ? 0 : 1), 0);

export const setMentions = (list: IMentionEntry[]): void =>
{
    mentions = [...list].sort((a, b) => b.mentionId - a.mentionId);
    emit();
};

export const addMention = (entry: IMentionEntry): void =>
{
    if(mentions.some(m => m.mentionId === entry.mentionId && entry.mentionId !== 0)) return;
    mentions = [entry, ...mentions];
    emit();
};

export const markRead = (mentionId: number): void =>
{
    mentions = mentions.map(m => m.mentionId === mentionId ? { ...m, read: true } : m);
    emit();
};

export const markAllRead = (): void =>
{
    mentions = mentions.map(m => m.read ? m : { ...m, read: true });
    emit();
};

export const removeMention = (mentionId: number): void =>
{
    const next = mentions.filter(m => m.mentionId !== mentionId);
    if(next.length === mentions.length) return;
    mentions = next;
    emit();
};

export const resetMentions = (): void => { mentions = []; emit(); };