/*
Copyright 2023 The Matrix.org Foundation C.I.C.

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 React, { ReactNode } from "react";
import { EventType, MatrixEvent } from "matrix-js-sdk/src/matrix";

import type MessagePanel from "../MessagePanel";
import type { WrappedEvent } from "../MessagePanel";
import { BaseGrouper } from "./BaseGrouper";
import { hasText } from "../../../TextForEvent";
import { MatrixClientPeg } from "../../../MatrixClientPeg";
import DateSeparator from "../../views/messages/DateSeparator";
import HistoryTile from "../../views/rooms/HistoryTile";
import EventListSummary from "../../views/elements/EventListSummary";

const groupedStateEvents = [
    EventType.RoomMember,
    EventType.RoomThirdPartyInvite,
    EventType.RoomServerAcl,
    EventType.RoomPinnedEvents,
];

// Wrap consecutive grouped events in a ListSummary
export class MainGrouper extends BaseGrouper {
    public static canStartGroup = function (panel: MessagePanel, { event: ev, shouldShow }: WrappedEvent): boolean {
        if (!shouldShow) return false;

        if (ev.isState() && groupedStateEvents.includes(ev.getType() as EventType)) {
            return true;
        }

        if (ev.isRedacted()) {
            return true;
        }

        if (panel.showHiddenEvents && !panel.shouldShowEvent(ev, true)) {
            return true;
        }

        return false;
    };

    public constructor(
        public readonly panel: MessagePanel,
        public readonly firstEventAndShouldShow: WrappedEvent,
        public readonly prevEvent: MatrixEvent | null,
        public readonly lastShownEvent: MatrixEvent | undefined,
        nextEvent: WrappedEvent | null,
        nextEventTile: MatrixEvent | null,
    ) {
        super(panel, firstEventAndShouldShow, prevEvent, lastShownEvent, nextEvent, nextEventTile);
        this.events = [firstEventAndShouldShow];
    }

    public shouldGroup({ event: ev, shouldShow }: WrappedEvent): boolean {
        if (!shouldShow) {
            // absorb hidden events so that they do not break up streams of messages & redaction events being grouped
            return true;
        }
        if (this.panel.wantsDateSeparator(this.events[0].event, ev.getDate())) {
            return false;
        }
        if (ev.isState() && groupedStateEvents.includes(ev.getType() as EventType)) {
            return true;
        }
        if (ev.isRedacted()) {
            return true;
        }
        if (this.panel.showHiddenEvents && !this.panel.shouldShowEvent(ev, true)) {
            return true;
        }
        return false;
    }

    public add(wrappedEvent: WrappedEvent): void {
        const { event: ev, shouldShow } = wrappedEvent;
        if (ev.getType() === EventType.RoomMember) {
            // We can ignore any events that don't actually have a message to display
            if (!hasText(ev, MatrixClientPeg.safeGet(), this.panel.showHiddenEvents)) return;
        }
        this.readMarker = this.readMarker || this.panel.readMarkerForEvent(ev.getId()!, ev === this.lastShownEvent);
        if (!this.panel.showHiddenEvents && !shouldShow) {
            // absorb hidden events to not split the summary
            return;
        }
        this.events.push(wrappedEvent);
    }

    private generateKey(): string {
        return "eventlistsummary-" + this.events[0].event.getId();
    }

    public getTiles(): ReactNode[] {
        // If we don't have any events to group, don't even try to group them. The logic
        // below assumes that we have a group of events to deal with, but we might not if
        // the events we were supposed to group were redacted.
        if (!this.events?.length) return [];

        const isGrouped = true;
        const panel = this.panel;
        const lastShownEvent = this.lastShownEvent;
        const ret: ReactNode[] = [];

        if (panel.wantsDateSeparator(this.prevEvent, this.events[0].event.getDate())) {
            const ts = this.events[0].event.getTs();
            ret.push(
                <li key={ts + "~"}>
                    <DateSeparator roomId={this.events[0].event.getRoomId()!} ts={ts} />
                </li>,
            );
        }

        // Ensure that the key of the EventListSummary does not change with new events in either direction.
        // This will prevent it from being re-created unnecessarily, and instead will allow new props to be provided.
        // In turn, the shouldComponentUpdate method on ELS can be used to prevent unnecessary renderings.
        const keyEvent = this.events.find((e) => this.panel.grouperKeyMap.get(e.event));
        const key =
            keyEvent && this.panel.grouperKeyMap.has(keyEvent.event)
                ? this.panel.grouperKeyMap.get(keyEvent.event)!
                : this.generateKey();
        if (!keyEvent) {
            // Populate the weak map with the key.
            // Note that we only set the key on the specific event it refers to, since this group might get
            // split up in the future by other intervening events. If we were to set the key on all events
            // currently in the group, we would risk later giving the same key to multiple groups.
            this.panel.grouperKeyMap.set(this.events[0].event, key);
        }

        let highlightInSummary = false;
        let eventTiles: ReactNode[] | null = this.events
            .map((e, i) => {
                if (e.event.getId() === panel.props.highlightedEventId) {
                    highlightInSummary = true;
                }
                return panel.getTilesForEvent(
                    i === 0 ? this.prevEvent : this.events[i - 1].event,
                    e,
                    e.event === lastShownEvent,
                    isGrouped,
                    this.nextEvent,
                    this.nextEventTile,
                );
            })
            .reduce((a, b) => a.concat(b), []);

        if (eventTiles.length === 0) {
            eventTiles = null;
        }

        // If a membership event is the start of visible history, tell the user
        // why they can't see earlier messages
        if (!this.panel.props.canBackPaginate && !this.prevEvent) {
            ret.push(<HistoryTile key="historytile" />);
        }

        ret.push(
            <EventListSummary
                key={key}
                data-testid={key}
                events={this.events.map((e) => e.event)}
                onToggle={panel.onHeightChanged} // Update scroll state
                startExpanded={highlightInSummary}
                layout={this.panel.props.layout}
            >
                {eventTiles}
            </EventListSummary>,
        );

        if (this.readMarker) {
            ret.push(this.readMarker);
        }

        return ret;
    }

    public getNewPrevEvent(): MatrixEvent {
        return this.events[this.events.length - 1].event;
    }
}