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-7';
const minTimeInterval = 1;	// minimum time between versions

let prior = {};
let priorTime = {};
let timer = -1;

const username = os.userInfo().username;
const sessionStart = time().toString();
let hashInitial = crypto.createHash('sha256').update(username + ' ' + sessionStart);
let hash = {};
let versionDir = {};

exports.activate = () => {
    vscode.workspace.textDocuments.forEach(doc => initFile(doc));
    vscode.workspace.onDidOpenTextDocument(doc => {
        initFile(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 version directory in versionDir
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';
	    }
	} catch (err) {
	    versionDir[dir] = '';
	}
    }
}

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

function textChanged(doc) {
    // limit the rate of versioning events
    if (doc.fileName in priorTime
	    && time() - priorTime[doc.fileName] < minTimeInterval) {
	// make sure this version is eventually saved
	if (timer >= 0) {
	    clearTimeout(timer);
	}
	// replace any pending timer event, so these don't pile up
	timer = setTimeout(textChanged, minTimeInterval, 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 dir = versionDir[path.dirname(doc.fileName)];
    try {
	if (! fs.statSync(dir).isDirectory) {
	    return;
	}
    } catch (err) {
	fs.mkdirSync(dir);
    }

    if (! (dir in hash)) {
	hash[dir] = hashInitial.copy();
    }

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

    const priorname = dir + path.sep + sessionStart + '.' + username + '.prior';
    const currentname = dir + path.sep + sessionStart + '.' + username + '.current';
    fs.writeFileSync(priorname, prior[doc.fileName]);
    const current = doc.getText();
    fs.writeFileSync(currentname, current);
    const versionfile = dir + path.sep + sessionStart + '.' + username;
    const stdout = child_process.execSync('diff "' + priorname + '" "' + currentname + '"; rm "' + priorname + '" "' + currentname + '"').toString();
    if (stdout != '') {
	const line = version + ' ' + time() + ' '
			+ hash[dir].copy().digest('hex') + ' '
			+ doc.fileName + ' '
			+ JSON.stringify(stdout);
	try {
	    fs.appendFileSync(versionfile, line + "\n", () => {});
	} catch (err) {
	    return;
	}
	hash[dir] = crypto.createHash('sha256').update(line);
	prior[doc.fileName] = current;
	priorTime[doc.fileName] = time();
    }
}