import { writable } from "svelte/store";
import gateway, { GatewayEventType } from "./gateway";
import request from "./request";
import { apiRoute } from "./storage";

class Store {
    constructor(value=null) {
        this._handlers = [];
        this.value = value;
    }

    subscribe(handler) {
        const newLength = this._handlers.push(handler);
        const handlerIndex = newLength - 1;
        handler(this.value);
        return () => {
            this._handlers.splice(handlerIndex, 1);
        };
    }

    updated() {
        this._handlers.forEach(e => {
            e(this.value);
        });
    }
}

class ChannelsStore extends Store {
    constructor() {
        super(gateway.channels || []);

        gateway.subscribe(GatewayEventType.Ready, ({ channels }) => {
            this.value = channels;
            this.updated();
        });
        gateway.subscribe(GatewayEventType.ChannelCreate, (channel) => {
            this.value.push(channel);
            this.updated();
        });
        gateway.subscribe(GatewayEventType.ChannelDelete, ({ id }) => {
            const index = this.value.findIndex(e => e.id === id);
            if (index === -1)
                return;

            this.value.splice(index, 1);
            this.updated();
        });
        gateway.subscribe(GatewayEventType.ChannelUpdate, (data) => {
            const index = this.value.findIndex(e => e.id === data.id);
            if (index === -1)
                return;
            if (!this.value[index])
                return;

            this.value[index] = data;
            this.updated();
        });
    }
}

class GatewayStatusStore extends Store {
    constructor() {
        super({ open: gateway.open, ready: gateway.authenticated });

        gateway.subscribe(GatewayEventType.Open, () => {
            this.value.open = true;
            this.updated();
        });

        gateway.subscribe(GatewayEventType.Close, () => {
            this.value.open = false;
            this.value.ready = false;
            this.updated();
        });

        gateway.subscribe(GatewayEventType.Ready, () => {
            this.value.ready = true;
            this.updated();
        });
    }
}

class UserInfoStore extends Store {
    constructor() {
        super(null);

        gateway.subscribe(GatewayEventType.Ready, ({ user }) => {
            this.value = user;
            this.updated();
        });

        gateway.subscribe(GatewayEventType.Close, () => {
            this.value = null;
            this.updated();
        });
    }
}

class MessageStore extends Store {
    constructor(channelId) {
        super([]);
        this.channelId = channelId;
        this.isCollectingOldMessages = true;
        this.didDoInitialLoad = false;
    }

    setMessage(id, message) {
        const index = this.value.findIndex(e => e.id === id);
        if (index === -1)
            return;

        this.value[index] = message;

        this.updated();
    }

    addMessage(message) {
        this.value.push(message);
        // only dispatch update if collectOldMessages didn't
        if (!this.collectOldMessages()) {
            this.updated();
        }
    }

    updateId(oldId, newId) {
        const index = this.value.findIndex(e => e.id === oldId);
        if (index === -1)
            return;

        this.value[index].id = newId;

        this.updated();
    }

    updateMessage(message) {
        const index = this.value.findIndex(e => e.id === message.id);
        if (index === -1)
            return;

        this.value[index] = message;

        this.updated();
    }

    deleteMessage({ id }) {
        const index = this.value.findIndex(e => e.id === id);
        if (index === -1)
            return;

        this.value.splice(index, 1);

        this.updated();
    }

    collectOldMessages() {
        if (!this.isCollectingOldMessages)
            return false;

        const target = 50;
        const delta = this.value.length - target;
        if (delta >= 1) {
            this.value.splice(0, delta);
            this.updated();
            return true;
        } else {
            return false;
        }
    }

    setIsCollectingOldMessages(isCollectingOldMessages) {
        this.isCollectingOldMessages = isCollectingOldMessages; 
        this.collectOldMessages();
    }

    async loadOlderMessages(beforeCommitToStore=null) {
        const oldestMessage = this.value[0];
        const endpoint = oldestMessage ? `channels/${this.channelId}/messages/?before=${oldestMessage.id}` : `channels/${this.channelId}/messages`;
        const res = await request("GET", apiRoute(endpoint), true, null);
        if (res.success && res.ok && res.json && res.json.length > 0) {
            if (beforeCommitToStore)
                beforeCommitToStore(res.json);
            res.json.reverse();
            this.value = res.json.concat(this.value);
            this.updated();
        }
    }

    async doInitialLoad() {
        await this.loadOlderMessages();
        this.didDoInitialLoad = true;
    }
}

class MessagesStoreProvider {
    constructor() {
        this.storeByChannel = new Map();

        gateway.subscribe(GatewayEventType.MessageCreate, (message) => {
            // we currently don't care about our own messages
            if (gateway.user && message.author_id === gateway.user.id)
                return;
            this.getStore(message.channel_id).addMessage(message);
        });
        gateway.subscribe(GatewayEventType.MessageUpdate, (message) => {
            this.getStore(message.channel_id).updateMessage(message);
        });
        gateway.subscribe(GatewayEventType.MessageDelete, (message) => {
            this.getStore(message.channel_id).deleteMessage(message);
        });
    }

    getStore(channelId) {
        if (!this.storeByChannel.get(channelId)) {
            const store = new MessageStore(channelId);
            store.doInitialLoad();
            this.storeByChannel.set(channelId, store);
        }
        return this.storeByChannel.get(channelId);
    }
}

export const channels = new ChannelsStore();
export const gatewayStatus = new GatewayStatusStore();
export const messagesStoreProvider = new MessagesStoreProvider();
export const userInfoStore = new UserInfoStore();
export const selectedChannel = writable({ id: -1, name: "none", creator_id: -1 });