/*
Copyright 2019 New Vector Ltd
Copyright 2019, 2020 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 Markdown from '../Markdown';
import {makeGenericPermalink} from "../utils/permalinks/Permalinks";
import EditorModel from "./model";
import { AllHtmlEntities } from 'html-entities';
import SettingsStore from '../settings/SettingsStore';
import SdkConfig from '../SdkConfig';
import cheerio from 'cheerio';

export function mdSerialize(model: EditorModel) {
    return model.parts.reduce((html, part) => {
        switch (part.type) {
            case "newline":
                return html + "\n";
            case "plain":
            case "command":
            case "pill-candidate":
            case "at-room-pill":
                return html + part.text;
            case "room-pill":
            case "user-pill":
                return html +
                    `[${part.text.replace(/[[\\\]]/g, c => "\\" + c)}](${makeGenericPermalink(part.resourceId)})`;
        }
    }, "");
}

export function markdownSerializeIfNeeded(md: string, {forceHTML = false} = {}, {forceTEX = false} = {}) {
    // copy of raw input to remove unwanted math later
    const orig = md;

    if (SettingsStore.getValue("feature_latex_maths")) {
        if (forceTEX) {
            // detect math with tex delimiters, inline: $...$, display $$...$$
            // preferably use negative lookbehinds, not supported in all major browsers:
            // const displayPattern = "^(?<!\\\\)\\$\\$(?![ \\t])(([^$]|\\\\\\$)+?)\\$\\$$";
            // const inlinePattern = "(?:^|\\s)(?<!\\\\)\\$(?!\\s)(([^$]|\\\\\\$)+?)(?<!\\\\|\\s)\\$";

            // conditions for display math detection $$...$$:
            // - pattern starts at beginning of line
            // - left delimiter ($$) is not escaped by backslash
            // - left delimiter is not followed by space or tab
            // - pattern ends at end of line
            const displayPattern = "^(?!\\\\)\\$\\$(?![ \\t])(([^$]|\\\\\\$)+?)\\$\\$$";

            // conditions for inline math detection $...$:
            // - pattern starts at beginning of line or follows whitespace character
            // - left and right delimiters ($) are not escaped by backslashes
            // - left delimiter is not followed by whitespace character
            // - right delimiter is not prefixed with whitespace character
            const inlinePattern = "(^|\\s)(?!\\\\)\\$(?!\\s)(([^$]|\\\\\\$)*[^\\\\\\s\\$](?:\\\\\\$)?)\\$";

            md = md.replace(RegExp(displayPattern, "gm"), function(m, p1) {
                const p1e = AllHtmlEntities.encode(p1);
                return `<div data-mx-maths="${p1e}">\n\n</div>\n\n`;
            });

            md = md.replace(RegExp(inlinePattern, "gm"), function(m, p1, p2) {
                const p2e = AllHtmlEntities.encode(p2);
                return `${p1}<span data-mx-maths="${p2e}"></span>`;
            });
        } else {
            // detect math with latex delimiters, inline: \(...\), display \[...\]

            // conditions for display math detection \[...\]:
            // - pattern starts at beginning of line
            // - pattern ends at end of line
            const displayPattern = (SdkConfig.get()['latex_maths_delims'] || {})['display_pattern'] ||
                "^\\\\\\[(.*?)\\\\\\]$";

            // conditions for inline math detection \(...\):
            // - pattern starts at beginning of line or is not prefixed with backslash
            // (this allows escaping and requires that multiple consecutive
            // patterns are separated by at least one character)
            const inlinePattern = (SdkConfig.get()['latex_maths_delims'] || {})['inline_pattern'] ||
                "(^|[^\\\\])\\\\\\((.*?)\\\\\\)";

            md = md.replace(RegExp(displayPattern, "gms"), function(m, p1) {
                const p1e = AllHtmlEntities.encode(p1);
                return `<div data-mx-maths="${p1e}">\n\n</div>\n\n`;
            });

            md = md.replace(RegExp(inlinePattern, "gms"), function(m, p1, p2) {
                const p2e = AllHtmlEntities.encode(p2);
                return `${p1}<span data-mx-maths="${p2e}"></span>`;
            });
        }

        // make sure div tags always start on a new line, otherwise it will confuse
        // the markdown parser
        md = md.replace(/(.)<div/g, function(m, p1) { return `${p1}\n<div`; });
    }

    const parser = new Markdown(md);
    if (!parser.isPlainText() || forceHTML) {
        // feed Markdown output to HTML parser
        const phtml = cheerio.load(parser.toHTML(),
            { _useHtmlParser2: true, decodeEntities: false });

        if (SettingsStore.getValue("feature_latex_maths")) {
            // original Markdown without LaTeX replacements
            const parserOrig = new Markdown(orig);
            const phtmlOrig = cheerio.load(parserOrig.toHTML(),
                { _useHtmlParser2: true, decodeEntities: false });

            // since maths delimiters are handled before Markdown,
            // code blocks could contain mangled content.
            // replace code blocks with original content
            phtml('code').contents('div, span').each(function(i) {
                const origData = phtmlOrig('code').contents('div, span')[i].data;
                phtml('code').contents('div, span')[i].data = origData;
            });

            // add fallback output for latex math, which should not be interpreted as markdown
            phtml('div, span').each(function(i, e) {
                const tex = phtml(e).attr('data-mx-maths')
                if (tex) {
                    phtml(e).html(`<code>${tex}</code>`)
                }
            });
        }
        return phtml.html();
    }
    // ensure removal of escape backslashes in non-Markdown messages
    if (md.indexOf("\\") > -1) {
        return parser.toPlaintext();
    }
}

export function htmlSerializeIfNeeded(model: EditorModel, {forceHTML = false} = {}) {
    let md = mdSerialize(model);

    return markdownSerializeIfNeeded(md, {forceHTML: forceHTML});
}

export function textSerialize(model: EditorModel) {
    return model.parts.reduce((text, part) => {
        switch (part.type) {
            case "newline":
                return text + "\n";
            case "plain":
            case "command":
            case "pill-candidate":
            case "at-room-pill":
                return text + part.text;
            case "room-pill":
            case "user-pill":
                return text + `${part.text}`;
        }
    }, "");
}

export function containsEmote(model: EditorModel) {
    return startsWith(model, "/me ", false);
}

export function startsWith(model: EditorModel, prefix: string, caseSensitive = true) {
    const firstPart = model.parts[0];
    // part type will be "plain" while editing,
    // and "command" while composing a message.
    let text = firstPart && firstPart.text;
    if (!caseSensitive) {
        prefix = prefix.toLowerCase();
        text = text.toLowerCase();
    }

    return firstPart && (firstPart.type === "plain" || firstPart.type === "command") && text.startsWith(prefix);
}

export function stripEmoteCommand(model: EditorModel) {
    // trim "/me "
    return stripPrefix(model, "/me ");
}

export function stripPrefix(model: EditorModel, prefix: string) {
    model = model.clone();
    model.removeText({index: 0, offset: 0}, prefix.length);
    return model;
}

export function unescapeMessage(model: EditorModel) {
    const {parts} = model;
    if (parts.length) {
        const firstPart = parts[0];
        // only unescape \/ to / at start of editor
        if (firstPart.type === "plain" && firstPart.text.startsWith("\\/")) {
            model = model.clone();
            model.removeText({index: 0, offset: 0}, 1);
        }
    }
    return model;
}