for-legacy-web/src/redux/reducers/unreads.ts

import type { Sync } from "revolt.js/dist/api/objects";

export interface Unreads {
	[key: string]: Partial<Omit<Sync.ChannelUnread, "_id">>;
}

export type UnreadsAction =
	| { type: undefined }
	| {
			type: "UNREADS_MARK_READ";
			channel: string;
			message: string;
	  }
	| {
			type: "UNREADS_SET";
			unreads: Sync.ChannelUnread[];
	  }
	| {
			type: "UNREADS_MENTION";
			channel: string;
			message: string;
	  }
	| {
			type: "RESET";
	  };

export function unreads(state = {} as Unreads, action: UnreadsAction): Unreads {
	switch (action.type) {
		case "UNREADS_MARK_READ":
			return {
				...state,
				[action.channel]: {
					last_id: action.message,
				},
			};
		case "UNREADS_SET": {
			const obj: Unreads = {};
			for (const entry of action.unreads) {
				const { _id, ...v } = entry;
				obj[_id.channel] = v;
			}

			return obj;
		}
		case "UNREADS_MENTION": {
			const obj = state[action.channel];

			return {
				...state,
				[action.channel]: {
					...obj,
					mentions: [...(obj?.mentions ?? []), action.message],
				},
			};
		}
		case "RESET":
			return {};
		default:
			return state;
	}
}