/*
Copyright 2020 Bruno Windels <bruno@windels.cloud>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import {SimpleTile} from "./SimpleTile.js";
import {UpdateAction} from "../UpdateAction.js";
import {ConnectionError} from "../../../../../matrix/error.js";
import {ConnectionStatus} from "../../../../../matrix/net/Reconnector";

export class GapTile extends SimpleTile {
    constructor(entry, options) {
        super(entry, options);
        this._loading = false;
        this._error = null;
        this._isAtTop = true;
        this._siblingChanged = false;
    }

    async fill() {
        if (!this._loading && !this._entry.edgeReached) {
            this._loading = true;
            this._error = null;
            this.emitChange("isLoading");
            try {
                await this._room.fillGap(this._entry, 10);
            } catch (err) {
                console.error(`room.fillGap(): ${err.message}:\n${err.stack}`);
                this._error = err;
                this._loading = false;
                this.emitChange("error");
                if (err instanceof ConnectionError) {
                    /*
                    We need to wait for reconnection here rather than in
                    notifyVisible() because when we return/throw here
                    this._loading is set to false and other queued invocations of
                    this method will succeed and attempt further room.fillGap() calls - 
                    resulting in multiple error entries in logs and elsewhere!
                    */
                    await this._waitForReconnection();
                    return true;
                }
                // rethrow so caller of this method
                // knows not to keep calling this for now
                throw err;
            } finally {
                this._loading = false;
                this.emitChange("isLoading");
            }
                return true;
        }
        return false;
    }

    async notifyVisible() {
        // we do (up to 10) backfills while no new tiles have been added to the timeline
        // because notifyVisible won't be called again until something gets added to the timeline
        let depth = 0;
        let canFillMore;
        this._siblingChanged = false;
        do {
            try {
                canFillMore = await this.fill();
            }
            catch (e) {
                if (e instanceof ConnectionError) {
                    // Don't increase depth because this gap fill was a noop
                    continue;
                }
                else {
                    canFillMore = false;
                }
            }
            depth = depth + 1;
        } while (depth < 10 && !this._siblingChanged && canFillMore && !this.isDisposed);
    }

    get isAtTop() {
        return this._isAtTop;
    }

    updatePreviousSibling(prev) {
        super.updatePreviousSibling(prev);
        const isAtTop = !prev;
        if (this._isAtTop !== isAtTop) {
            this._isAtTop = isAtTop;
            this.emitChange("isAtTop");
        }
        this._siblingChanged = true;
    }

    updateNextSibling() {
        // if the sibling of the gap changed while calling room.fill(),
        // we intepret this as at least one new tile has been added to
        // the timeline. See notifyVisible why this is important.
        this._siblingChanged = true;
    }

    updateEntry(entry, params) {
        super.updateEntry(entry, params);
        if (!entry.isGap) {
            return UpdateAction.Remove();
        } else {
            return UpdateAction.Nothing();
        }
    }

    async _waitForReconnection() {
        await this.options.client.reconnector.connectionStatus.waitFor(status => status === ConnectionStatus.Online).promise;
    }

    get shape() {
        return "gap";
    }

    get isLoading() {
        return this._loading;
    }

    get error() {
        if (this._error) {
            if (this._error instanceof ConnectionError) {
                return { message: "Waiting for reconnection", showSpinner: true };
            }
            const dir = this._entry.prev_batch ? "previous" : "next";
            return { message: `Could not load ${dir} messages: ${this._error.message}`, showSpinner: false };
        }
        return null;
    }
}

import {FragmentBoundaryEntry} from "../../../../../matrix/room/timeline/entries/FragmentBoundaryEntry.js";
export function tests() {
    return {
        "uses updated token to fill": async assert => {
            let currentToken = 5;
            const fragment = {
                id: 0,
                previousToken: currentToken,
                roomId: "!abc"
            };
            const room = {
                async fillGap(entry) {
                    assert.equal(entry.token, currentToken);
                    currentToken += 1;
                    const newEntry = entry.withUpdatedFragment(Object.assign({}, fragment, {previousToken: currentToken}));
                    tile.updateEntry(newEntry);
                }
            };
            const tile = new GapTile(new FragmentBoundaryEntry(fragment, true), {roomVM: {room}});
            await tile.fill();
            await tile.fill();
            await tile.fill();
            assert.equal(currentToken, 8);
        }
    }
}