/*
Copyright 2019-2023 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 from "react";
import ReactDOM from "react-dom";
import { PushProcessor } from "matrix-js-sdk/src/pushprocessor";
import { MatrixEvent } from "matrix-js-sdk/src/models/event";

import { MatrixClientPeg } from "../MatrixClientPeg";
import SettingsStore from "../settings/SettingsStore";
import { Pill, PillType, pillRoomNotifLen, pillRoomNotifPos } from "../components/views/elements/Pill";
import { parsePermalink } from "./permalinks/Permalinks";
import { PermalinkParts } from "./permalinks/PermalinkConstructor";

/**
 * A node here is an A element with a href attribute tag.
 *
 * It should not be pillified if the permalink parser result contains an event Id.
 *
 * It should be pillified if the permalink parser returns a result and one of the following conditions match:
 * - Text content equals href. This is the case when sending a plain permalink inside a message.
 * - The link does not have the "linkified" class.
 *   Composer completions already create an A tag.
 *   Linkify will not linkify things again. → There won't be a "linkified" class.
 */
const shouldBePillified = (node: Element, href: string, parts: PermalinkParts | null): boolean => {
    if (!parts || parts.eventId) return false;

    const textContent = node.textContent;
    return href === textContent || !node.classList.contains("linkified");
};

/**
 * Recurses depth-first through a DOM tree, converting matrix.to links
 * into pills based on the context of a given room.  Returns a list of
 * the resulting React nodes so they can be unmounted rather than leaking.
 *
 * @param {Element[]} nodes - a list of sibling DOM nodes to traverse to try
 *   to turn into pills.
 * @param {MatrixEvent} mxEvent - the matrix event which the DOM nodes are
 *   part of representing.
 * @param {Element[]} pills: an accumulator of the DOM nodes which contain
 *   React components which have been mounted as part of this.
 *   The initial caller should pass in an empty array to seed the accumulator.
 */
export function pillifyLinks(nodes: ArrayLike<Element>, mxEvent: MatrixEvent, pills: Element[]): void {
    const room = MatrixClientPeg.get().getRoom(mxEvent.getRoomId()) ?? undefined;
    const shouldShowPillAvatar = SettingsStore.getValue("Pill.shouldShowPillAvatar");
    let node = nodes[0];
    while (node) {
        let pillified = false;

        if (node.tagName === "PRE" || node.tagName === "CODE" || pills.includes(node)) {
            // Skip code blocks and existing pills
            node = node.nextSibling as Element;
            continue;
        } else if (node.tagName === "A" && node.getAttribute("href")) {
            const href = node.getAttribute("href")!;
            const parts = parsePermalink(href);

            if (shouldBePillified(node, href, parts)) {
                const pillContainer = document.createElement("span");

                const pill = (
                    <Pill url={href} inMessage={true} room={room} shouldShowPillAvatar={shouldShowPillAvatar} />
                );

                ReactDOM.render(pill, pillContainer);
                node.parentNode.replaceChild(pillContainer, node);
                pills.push(pillContainer);
                // Pills within pills aren't going to go well, so move on
                pillified = true;

                // update the current node with one that's now taken its place
                node = pillContainer;
            }
        } else if (
            node.nodeType === Node.TEXT_NODE &&
            // as applying pills happens outside of react, make sure we're not doubly
            // applying @room pills here, as a rerender with the same content won't touch the DOM
            // to clear the pills from the last run of pillifyLinks
            !node.parentElement.classList.contains("mx_AtRoomPill")
        ) {
            let currentTextNode = node as Node as Text | null;
            const roomNotifTextNodes = [];

            // Take a textNode and break it up to make all the instances of @room their
            // own textNode, adding those nodes to roomNotifTextNodes
            while (currentTextNode !== null) {
                const roomNotifPos = pillRoomNotifPos(currentTextNode.textContent);
                let nextTextNode: Text | null = null;
                if (roomNotifPos > -1) {
                    let roomTextNode = currentTextNode;

                    if (roomNotifPos > 0) roomTextNode = roomTextNode.splitText(roomNotifPos);
                    if (roomTextNode.textContent.length > pillRoomNotifLen()) {
                        nextTextNode = roomTextNode.splitText(pillRoomNotifLen());
                    }
                    roomNotifTextNodes.push(roomTextNode);
                }
                currentTextNode = nextTextNode;
            }

            if (roomNotifTextNodes.length > 0) {
                const pushProcessor = new PushProcessor(MatrixClientPeg.get());
                const atRoomRule = pushProcessor.getPushRuleById(".m.rule.roomnotif");
                if (atRoomRule && pushProcessor.ruleMatchesEvent(atRoomRule, mxEvent)) {
                    // Now replace all those nodes with Pills
                    for (const roomNotifTextNode of roomNotifTextNodes) {
                        // Set the next node to be processed to the one after the node
                        // we're adding now, since we've just inserted nodes into the structure
                        // we're iterating over.
                        // Note we've checked roomNotifTextNodes.length > 0 so we'll do this at least once
                        node = roomNotifTextNode.nextSibling as Element;

                        const pillContainer = document.createElement("span");
                        const pill = (
                            <Pill
                                type={PillType.AtRoomMention}
                                inMessage={true}
                                room={room}
                                shouldShowPillAvatar={shouldShowPillAvatar}
                            />
                        );

                        ReactDOM.render(pill, pillContainer);
                        roomNotifTextNode.parentNode.replaceChild(pillContainer, roomNotifTextNode);
                        pills.push(pillContainer);
                    }
                    // Nothing else to do for a text node (and we don't need to advance
                    // the loop pointer because we did it above)
                    continue;
                }
            }
        }

        if (node.childNodes && node.childNodes.length && !pillified) {
            pillifyLinks(node.childNodes as NodeListOf<Element>, mxEvent, pills);
        }

        node = node.nextSibling as Element;
    }
}

/**
 * Unmount all the pill containers from React created by pillifyLinks.
 *
 * It's critical to call this after pillifyLinks, otherwise
 * Pills will leak, leaking entire DOM trees via the event
 * emitter on BaseAvatar as per
 * https://github.com/vector-im/element-web/issues/12417
 *
 * @param {Element[]} pills - array of pill containers whose React
 *   components should be unmounted.
 */
export function unmountPills(pills: Element[]): void {
    for (const pillContainer of pills) {
        ReactDOM.unmountComponentAtNode(pillContainer);
    }
}
