/*
 * This code is an adaptation of https://github.com/antoniotejada/Trilium-SyntaxHighlightWidget with additional improvements, such as:
 *
 *  - support for selecting the language manually;
 *  - support for determining the language automatically, if a special language is selected ("Auto-detected");
 *  - limit for highlighting.
 *
 * TODO: Generally this class can be done directly in the CKEditor repository.
 */

import library_loader from "../../../services/library_loader.js";
import mime_types from "../../../services/mime_types.js";
import { isSyntaxHighlightEnabled } from "../../../services/syntax_highlight.js";

export async function initSyntaxHighlighting(editor: TextEditor) {
    if (!isSyntaxHighlightEnabled) {
        return;
    }

    await library_loader.requireLibrary(library_loader.HIGHLIGHT_JS);
    initTextEditor(editor);
}

const HIGHLIGHT_MAX_BLOCK_COUNT = 500;

const tag = "SyntaxHighlightWidget";
const debugLevels = ["error", "warn", "info", "log", "debug"];
const debugLevel = debugLevels.indexOf("warn");

let warn = function (...args: unknown[]) {};
if (debugLevel >= debugLevels.indexOf("warn")) {
    warn = console.warn.bind(console, tag + ": ");
}

let info = function (...args: unknown[]) {};
if (debugLevel >= debugLevels.indexOf("info")) {
    info = console.info.bind(console, tag + ": ");
}

let log = function (...args: unknown[]) {};
if (debugLevel >= debugLevels.indexOf("log")) {
    log = console.log.bind(console, tag + ": ");
}

let dbg = function (...args: unknown[]) {};
if (debugLevel >= debugLevels.indexOf("debug")) {
    dbg = console.debug.bind(console, tag + ": ");
}

function assert(e: boolean, msg?: string) {
    console.assert(e, tag + ": " + msg);
}

// TODO: Should this be scoped to note?
let markerCounter = 0;

function initTextEditor(textEditor: TextEditor) {
    log("initTextEditor");

    const document = textEditor.model.document;

    // Create a conversion from model to view that converts
    // hljs:hljsClassName:uniqueId into a span with hljsClassName
    // See the list of hljs class names at
    // https://github.com/highlightjs/highlight.js/blob/6b8c831f00c4e87ecd2189ebbd0bb3bbdde66c02/docs/css-classes-reference.rst

    textEditor.conversion.for("editingDowncast").markerToHighlight({
        model: "hljs",
        view: ({ markerName }) => {
            dbg("markerName " + markerName);
            // markerName has the pattern addMarker:cssClassName:uniqueId
            const [, cssClassName, id] = markerName.split(":");

            // The original code at
            // https://github.com/ckeditor/ckeditor5/blob/master/packages/ckeditor5-find-and-replace/src/findandreplaceediting.js
            // has this comment
            //      Marker removal from the view has a bug:
            //      https://github.com/ckeditor/ckeditor5/issues/7499
            //      A minimal option is to return a new object for each converted marker...
            return {
                name: "span",
                classes: [cssClassName],
                attributes: {
                    // ...however, adding a unique attribute should be future-proof..
                    "data-syntax-result": id
                }
            };
        }
    });

    // XXX This is done at BalloonEditor.create time, so it assumes this
    //     document is always attached to this textEditor, empirically that
    //     seems to be the case even with two splits showing the same note,
    //     it's not clear if CKEditor5 has apis to attach and detach
    //     documents around
    document.registerPostFixer(function (writer) {
        log("postFixer");
        // Postfixers are a simpler way of tracking changes than onchange
        // See
        // https://github.com/ckeditor/ckeditor5/blob/b53d2a4b49679b072f4ae781ac094e7e831cfb14/packages/ckeditor5-block-quote/src/blockquoteediting.js#L54
        const changes = document.differ.getChanges();
        let dirtyCodeBlocks = new Set<CKNode>();

        for (const change of changes) {
            dbg("change " + JSON.stringify(change));

            if (change.type == "insert" && change.name == "codeBlock") {
                // A new code block was inserted
                const codeBlock = change.position.nodeAfter;
                // Even if it's a new codeblock, it needs dirtying in case
                // it already has children, like when pasting one or more
                // full codeblocks, undoing a delete, changing the language,
                // etc (the postfixer won't get later changes for those).
                log("dirtying inserted codeBlock " + JSON.stringify(codeBlock.toJSON()));
                dirtyCodeBlocks.add(codeBlock);
            } else if (change.type == "remove" && change.name == "codeBlock") {
                // An existing codeblock was removed, do nothing. Note the
                // node is no longer in the editor so the codeblock cannot
                // be inspected here. No need to dirty the codeblock since
                // it has been removed
                log("removing codeBlock at path " + JSON.stringify(change.position.toJSON()));
            } else if ((change.type == "remove" || change.type == "insert") && change.position.parent.is("element", "codeBlock")) {
                // Text was added or removed from the codeblock, force a
                // highlight
                const codeBlock = change.position.parent;
                log("dirtying codeBlock " + JSON.stringify(codeBlock.toJSON()));
                dirtyCodeBlocks.add(codeBlock);
            }
        }
        for (let codeBlock of dirtyCodeBlocks) {
            highlightCodeBlock(codeBlock, writer);
        }
        // Adding markers doesn't modify the document data so no need for
        // postfixers to run again
        return false;
    });

    // This assumes the document is empty and a explicit call to highlight
    // is not necessary here. Empty documents have a single children of type
    // paragraph with no text
    assert(document.getRoot().childCount == 1 && document.getRoot().getChild(0).name == "paragraph" && document.getRoot().getChild(0).isEmpty);
}

/**
 * This implements highlighting via ephemeral markers (not stored in the
 * document).
 *
 * XXX Another option would be to use formatting markers, which would have
 *     the benefit of making it work for readonly notes. On the flip side,
 *     the formatting would be stored with the note and it would need a
 *     way to remove that formatting when editing back the note.
 */
function highlightCodeBlock(codeBlock: CKNode, writer: Writer) {
    log("highlighting codeblock " + JSON.stringify(codeBlock.toJSON()));
    const model = codeBlock.root.document.model;

    // Can't invoke addMarker with an already existing marker name,
    // clear all highlight markers first. Marker names follow the
    // pattern hljs:cssClassName:uniqueId, eg hljs:hljs-comment:1
    const codeBlockRange = model.createRangeIn(codeBlock);
    for (const marker of model.markers.getMarkersIntersectingRange(codeBlockRange)) {
        dbg("removing marker " + marker.name);
        writer.removeMarker(marker.name);
    }

    // Don't highlight if plaintext (note this needs to remove the markers
    // above first, in case this was a switch from non plaintext to
    // plaintext)
    const mimeType = codeBlock.getAttribute("language");
    if (mimeType == "text-plain") {
        // XXX There's actually a plaintext language that could be used
        //     if you wanted the non-highlight formatting of
        //     highlight.js css applied, see
        //     https://github.com/highlightjs/highlight.js/issues/700
        log("not highlighting plaintext codeblock");
        return;
    }

    // Find the corresponding language for the given mimetype.
    const highlightJsLanguage = mime_types.getHighlightJsNameForMime(mimeType);

    if (mimeType !== mime_types.MIME_TYPE_AUTO && !highlightJsLanguage) {
        console.warn(`Unsupported highlight.js for mime type ${mimeType}.`);
        return;
    }

    // Don't highlight if the code is too big, as the typing performance will be highly degraded.
    if (codeBlock.childCount >= HIGHLIGHT_MAX_BLOCK_COUNT) {
        return;
    }

    // highlight.js needs the full text without HTML tags, eg for the
    // text
    // #include <stdio.h>
    // the highlighted html is
    // <span class="hljs-meta">#<span class="hljs-keyword">include</span> <span class="hljs-string">&lt;stdio.h&gt;</span></span>
    // But CKEditor codeblocks have <br> instead of \n

    // Do a two pass algorithm:
    // - First pass collect the codeblock children text, change <br> to
    //   \n
    // - invoke highlight.js on the collected text generating html
    // - Second pass parse the highlighted html spans and match each
    //   char to the CodeBlock text. Issue addMarker CKEditor calls for
    //   each span

    // XXX This is brittle and assumes how highlight.js generates html
    //     (blanks, which characters escapes, etc), a better approach
    //     would be to use highlight.js beta api TreeTokenizer?

    // Collect all the text nodes to pass to the highlighter Text is
    // direct children of the codeBlock
    let text = "";
    for (let i = 0; i < codeBlock.childCount; ++i) {
        let child = codeBlock.getChild(i);

        // We only expect text and br elements here
        if (child.is("$text")) {
            dbg("child text " + child.data);
            text += child.data;
        } else if (child.is("element") && child.name == "softBreak") {
            dbg("softBreak");
            text += "\n";
        } else {
            warn("Unkown child " + JSON.stringify(child.toJSON()));
        }
    }

    let highlightRes;
    if (mimeType === mime_types.MIME_TYPE_AUTO) {
        highlightRes = hljs.highlightAuto(text);
    } else {
        highlightRes = hljs.highlight(text, { language: highlightJsLanguage });
    }
    dbg("text\n" + text);
    dbg("html\n" + highlightRes.value);

    let iHtml = 0;
    let html = highlightRes.value;
    let spanStack = [];
    let iChild = -1;
    let childText = "";
    let child = null;
    let iChildText = 0;

    while (iHtml < html.length) {
        // Advance the text index and fetch a new child if necessary
        if (iChildText >= childText.length) {
            iChild++;
            if (iChild < codeBlock.childCount) {
                dbg("Fetching child " + iChild);
                child = codeBlock.getChild(iChild);
                if (child.is("$text")) {
                    dbg("child text " + child.data);
                    childText = child.data;
                    iChildText = 0;
                } else if (child.is("element", "softBreak")) {
                    dbg("softBreak");
                    iChildText = 0;
                    childText = "\n";
                } else {
                    warn("child unknown!!!");
                }
            } else {
                // Don't bail if beyond the last children, since there's
                // still html text, it must be a closing span tag that
                // needs to be dealt with below
                childText = "";
            }
        }

        // This parsing is made slightly simpler and faster by only
        // expecting <span> and </span> tags in the highlighted html
        if (html[iHtml] == "<" && html[iHtml + 1] != "/") {
            // new span, note they can be nested eg C preprocessor lines
            // are inside a hljs-meta span, hljs-title function names
            // inside a hljs-function span, etc
            let iStartQuot = html.indexOf('"', iHtml + 1);
            let iEndQuot = html.indexOf('"', iStartQuot + 1);
            let className = html.slice(iStartQuot + 1, iEndQuot);
            // XXX highlight js uses scope for Python "title function_",
            //     etc for now just use the first style only
            // See https://highlightjs.readthedocs.io/en/latest/css-classes-reference.html#a-note-on-scopes-with-sub-scopes
            let iBlank = className.indexOf(" ");
            if (iBlank > 0) {
                className = className.slice(0, iBlank);
            }
            dbg("Found span start " + className);

            iHtml = html.indexOf(">", iHtml) + 1;

            // push the span
            let posStart = writer.createPositionAt(codeBlock, (child?.startOffset ?? 0) + iChildText);
            spanStack.push({ className: className, posStart: posStart });
        } else if (html[iHtml] == "<" && html[iHtml + 1] == "/") {
            // Done with this span, pop the span and mark the range
            iHtml = html.indexOf(">", iHtml + 1) + 1;

            let stackTop = spanStack.pop();
            let posStart = stackTop?.posStart;
            let className = stackTop?.className;
            let posEnd = writer.createPositionAt(codeBlock, (child?.startOffset ?? 0) + iChildText);
            let range = writer.createRange(posStart, posEnd);
            let markerName = "hljs:" + className + ":" + markerCounter;
            // Use an incrementing number for the uniqueId, random of
            // 10000000 is known to cause collisions with a few
            // codeblocks of 10s of lines on real notes (each line is
            // one or more marker).
            // Wrap-around for good measure so all numbers are positive
            // XXX Another option is to catch the exception and retry or
            //     go through the markers and get the largest + 1
            markerCounter = (markerCounter + 1) & 0xffffff;
            dbg("Found span end " + className);
            dbg("Adding marker " + markerName + ": " + JSON.stringify(range.toJSON()));
            writer.addMarker(markerName, { range: range, usingOperation: false });
        } else {
            // Text, we should also have text in the children
            assert(iChild < codeBlock.childCount && iChildText < childText.length, "Found text in html with no corresponding child text!!!!");
            if (html[iHtml] == "&") {
                // highlight.js only encodes
                // .replace(/&/g, '&amp;')
                // .replace(/</g, '&lt;')
                // .replace(/>/g, '&gt;')
                // .replace(/"/g, '&quot;')
                // .replace(/'/g, '&#x27;');
                // see https://github.com/highlightjs/highlight.js/blob/7addd66c19036eccd7c602af61f1ed84d215c77d/src/lib/utils.js#L5
                let iAmpEnd = html.indexOf(";", iHtml);
                dbg(html.slice(iHtml, iAmpEnd));
                iHtml = iAmpEnd + 1;
            } else {
                // regular text
                dbg(html[iHtml]);
                iHtml++;
            }
            iChildText++;
        }
    }
}
