import gateway, { GatewayEventType } from "./gateway";
import logger from "./logging";
import request from "./request";
import { apiRoute, getItem, setItem } from "./storage";

const storeLog = logger("Store");

class Store {
    constructor(value=null, name="[no name]") {
        this._handlers = [];
        this.value = value;
        this.name = name;
    }

    // like subscribe, but without initially calling the handler
    watch(handler) {
        const handlerIndex = this._handlers.push(handler) - 1;
        storeLog(`(${this.name}) (watch/handler) New handler`, this.value);
        return () => {
            this._handlers.splice(handlerIndex, 1);
        };
    }

    subscribe(handler) {
        const handlerIndex = this._handlers.push(handler) - 1;
        storeLog(`(${this.name}) (subscribe/initial) Calling handler`, this.value);
        handler(this.value);
        return () => {
            this._handlers.splice(handlerIndex, 1);
        };
    }

    set(value) {
        if (value === this.value)
            return;

        this.value = value;
        this.updated();
    }

    updated() {
        storeLog(`(${this.name}) (updated) Calling all (${this._handlers.length}) handlers`, this.value);
        for (let i = this._handlers.length - 1; i >= 0; i--) {
            this._handlers[i](this.value);
        }
    }
}

class StorageItemStore extends Store {
    constructor(key) {
        super(getItem(key), `StorageItemStore[key=${key}]`);
        this.watch(e => setItem(key, e));
    }
}

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

        gateway.subscribe(GatewayEventType.Ready, ({ channels }) => {
            this.value = channels;
            if (channels.length >= 1) {
                if (!selectedChannel.value || selectedChannel.value.id === -1) {
                    selectedChannel.set(channels[0]);
                } else {
                    // if a channel id is already selected, we'll populate it with the data we just got from the gateway
                    const index = this.value.findIndex(e => e.id === selectedChannel.value.id);
                    if (index !== -1)
                        selectedChannel.set(this.value[index]);
                    else // if the channel doesn't exist, just select the first one
                        selectedChannel.set(channels[0]);
                }
            }
            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();
        });
        gateway.subscribe(GatewayEventType.MessageCreate, ({ channel_id }) => {
            const index = this.value.findIndex(e => e.id === channel_id);
            if (index === -1 || !this.value[index] || selectedChannel.value.id === channel_id)
                return;

            this.value[index]._hasUnreads = true;
            this.updated();
        });
        selectedChannel.subscribe(({ id }) => {
            const index = this.value.findIndex(e => e.id === id);
            if (index === -1 || !this.value[index] || !this.value[index]._hasUnreads)
                return;

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

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

        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, "UserInfoStore");

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

class MessageStore extends Store {
    constructor(channelId) {
        super([], `MessageStore[channelId=${channelId}]`);
        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) {
        if (this.channelId === -1)
            return;

        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) {
            if (res.json.length < 1)
                return;
            if (beforeCommitToStore)
                beforeCommitToStore(res.json);
            res.json.reverse();
            this.value = res.json.concat(this.value);
            this.updated();
        } else {
            overlayStore.open("toast", {
                message: "Messages failed to load"
            });
        }
    }

    async doInitialLoad() {
        if (this.channelId === -1)
            return;

        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;

            const store = this.getStoreOrNull(message.channel_id);
            if (store)
                store.addMessage(message);
        });
        gateway.subscribe(GatewayEventType.MessageUpdate, (message) => {
            const store = this.getStoreOrNull(message.channel_id);
            if (store)
                store.updateMessage(message);
        });
        gateway.subscribe(GatewayEventType.MessageDelete, (message) => {
            const store = this.getStoreOrNull(message.channel_id);
            if (store)
                store.deleteMessage(message);
        });
    }

    getStoreOrNull(channelId) {
        return this.storeByChannel.get(channelId);
    }

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

class OverlayStore extends Store {
    constructor() {
        super({
            createChannel: null,
            editChannel: null,
            toast: null,
            login: null,
            createAccount: null,
            editMessage: null,
            settings: null,
        }, "OverlayStore");
    }

    open(name, props={}) {
        if (this.value[name] === undefined)
            throw new Error(`OverlayStore.open: tried to open unknown overlay with name '${name}' (undefined in overlay map)`);
        this.value[name] = props;
        this.updated();
    }

    close(name) {
        if (!this.value[name])
            return;

        this.value[name] = null;
        this.updated();
    }
}

export const selectedChannel = new Store({ id: getItem("app:cache:openChannelId"), name: "none", creator_id: -1 }, "selectedChannel");
export const showSidebar = new Store(true, "showSidebar");
export const smallViewport = new Store(false, "smallViewport");
export const showChannelView = new Store(true, "showChannelView");
export const theme = new StorageItemStore("app:visual:theme");
export const doAnimations = new StorageItemStore("app:behavior:doAnimations");
export const channels = new ChannelsStore();
export const gatewayStatus = new GatewayStatusStore();
export const messagesStoreProvider = new MessagesStoreProvider();
export const userInfoStore = new UserInfoStore();
export const overlayStore = new OverlayStore();

export const allStores = {
    selectedChannel,
    showSidebar,
    showChannelView,
    smallViewport,
    theme,
    doAnimations,
    channels,
    gatewayStatus,
    messagesStoreProvider,
    userInfoStore,
    overlayStore,
};

selectedChannel.watch((newSelectedChannel) => {
    setItem("app:cache:openChannelId", newSelectedChannel.id);
});