version482

//
// Keep versions of files in EECS 482 github repos
//
const vscode = require('vscode');
const os = require('os');
const fs = require('fs');
const path = require('path');
const crypto = require('crypto');
const child_process = require('child_process');
const version = 'vscode-20250826';
const minTimeInterval = 1;	// minimum time between versions
const username = os.userInfo().username.replace(/[^a-zA-Z0-9]/g, "");

let hash = {};		// last hash value for each version file
let size = {};		// last size for each version file
let prior = {};		// prior contents for each file
let priorTime = {};	// last time each file was written

let sessionStart = time();
let hashInitial = crypto.createHash('sha256').update(username + ' ' + sessionStart.toString());

let versionDir = {};	// .version482 directory name for each source file directory
let timer = {};

exports.activate = () => {
    vscode.workspace.textDocuments.forEach(doc => initFile(doc));
    vscode.workspace.onDidOpenTextDocument(doc => {
        initFile(doc);
    });
    vscode.workspace.onDidSaveTextDocument(doc => {
        writeFile(doc);
    });
    vscode.workspace.onDidChangeTextDocument(e => {
        textChanged(e.document);
    });
}

// return current time in seconds
function time() {
    return(Math.trunc(Date.now()/1000));
}

// see if directory is in an EECS 482 git repo
// store .version482 directory name in versionDir, and make sure the
// .version482 directory exists
function initVersionDir(dir) {
    if (! (dir in versionDir)) {
        try {
	    const stdout = child_process.execSync('cd "' + dir + '"; git remote -v 2> /dev/null');
	    if (stdout.indexOf('eecs482') < 0) {
		versionDir[dir] = '';
	    } else {
		versionDir[dir] = child_process.execSync('cd "' + dir + '"; git rev-parse --show-toplevel').toString().trimEnd() + path.sep + '.version482';

		try {
		    if (! fs.statSync(versionDir[dir]).isDirectory) {
			versionDir[dir] = '';
		    }
		} catch (err) {
		    fs.mkdirSync(versionDir[dir]);
		}
	    }
	} catch (err) {
	    versionDir[dir] = '';
	}
    }
}

function initFile(doc) {
    initVersionDir(path.dirname(doc.fileName));
}

function writeFile(doc) {
    initVersionDir(path.dirname(doc.fileName));

    // make sure file is in an EECS 482 git repo
    if (versionDir[path.dirname(doc.fileName)] == '') {
        return;
    }

    child_process.execSync('cd "' + path.dirname(doc.fileName) + '"; git add "' + versionDir[path.dirname(doc.fileName)] + '"');
}

function textChanged(doc) {
    let now = time();

    // Limit the rate of versioning events.  Also log events where time has
    // gone backward by more than minTimeInterval.
    if (doc.fileName in priorTime
	    && Math.abs(now - priorTime[doc.fileName]) < minTimeInterval) {
	// replace any pending timer event for this file, so events don't pile up
	if (doc.fileName in timer) {
	    clearTimeout(timer[doc.fileName]);
	}
	// make sure this version is eventually saved
	timer[doc.fileName] = setTimeout(textChanged, minTimeInterval*1000, doc);
	return;
    }

    initVersionDir(path.dirname(doc.fileName));

    // make sure file is in an EECS 482 git repo
    if (versionDir[path.dirname(doc.fileName)] == '') {
        return;
    }

    // make sure file is a program source file, i.e., has extension {cpp,cc,h,hpp,py}
    const ext = path.extname(doc.fileName);
    if (ext != '.cpp' && ext != '.cc' && ext != '.h' && ext != '.hpp' && ext != '.py') {
	return;
    }

    // make sure file isn't too big
    if (doc.getText().length > 10 * 1024 * 1024) {
        return;
    }

    const versionDirname = versionDir[path.dirname(doc.fileName)];

    // check if version file has grown too old or too big
    if (now - sessionStart > 60*60 || (versionDirname in size && size[versionDirname] > 50 * 1024 * 1024)) {
	// start new version file by mimicking restarting vscode
	hash = {};
	size = {};
	prior = {};
	priorTime = {};
	sessionStart = now;
	hashInitial = crypto.createHash('sha256').update(username + ' ' + sessionStart.toString());
    }

    if (! (versionDirname in hash)) {
	hash[versionDirname] = hashInitial.copy();
    }
    if (! (versionDirname in size)) {
	size[versionDirname] = 0;
    }

    const priorname = versionDirname + path.sep + sessionStart.toString() + '.' + username + '.prior';
    const currentname = versionDirname + path.sep + sessionStart.toString() + '.' + username + '.current';

    if (! (doc.fileName in prior)) {
        prior[doc.fileName] = '';
    }

    fs.writeFileSync(priorname, prior[doc.fileName]);

    const current = doc.getText();
    fs.writeFileSync(currentname, current);
    const versionfile = versionDirname + path.sep + sessionStart.toString() + '.' + username;
    const diff = child_process.execSync('diff "' + priorname + '" "' + currentname + '"; rm "' + priorname + '" "' + currentname + '"').toString();
    if (diff != '') {
        let dict = {};
	dict['file'] = doc.fileName;
	dict['diff'] = diff;
	const line = version + ' ' + now + ' '
	                + size[versionDirname] + ' '
			+ hash[versionDirname].copy().digest('hex') + ' '
			+ JSON.stringify(dict);
	try {
	    fs.appendFileSync(versionfile, line + "\n", () => {});
	} catch (err) {
	    return;
	}
	prior[doc.fileName] = current;
	priorTime[doc.fileName] = now;

	hash[versionDirname] = crypto.createHash('sha256').update(line);
	size[versionDirname] += line.length + 1;
	// console.log(size[versionDirname]);

    }
}