let editor = new CodeMirror(document.body, {
	value: "function myScript() {\t\n\treturn 100;\n}",
	mode: "javascript",
	readOnly: true,
	autofocus: true
});

var incompleteMark = editor.doc.markText({ line: 0, ch: 0 }, getEndPos(), {
	className: "incomplete"
});

var focused = true;

editor.on("focus", (instance, event) => {
	focused = true;
});
editor.on("blur", (instance, event) => {
	focused = false;
})

let invalids = [];

document.addEventListener("keypress", (event) => {
	if (focused) {
		event.preventDefault();

		let pos = editor.getCursor();
		let line = editor.doc.getLine(pos.line);
		let char = line.charCodeAt(pos.ch);
		if (event.charCode != char) {
			let mark = editor.doc.markText(pos, {line: pos.line, ch: pos.ch + 1}, {
				className: "invalid"
			});
			if (!invalids[pos.line]) invalids[pos.line] = [];
			invalids[pos.line][pos.ch] = mark;
		}
		editor.setCursor({ line: pos.line, ch: pos.ch + 1 });
		updateIncompleteMark();
	}
});

document.addEventListener("keydown", (event) => {
	if (focused) {
		var result = false;

		if (event.keyCode == 8) { // delete
			result = true;

			let pos = editor.getCursor();
			if (pos.ch == 0) { // move up 1 line {
				moveToEndOfPreviousLine();
			} else { // move back 1 char
				let line = editor.doc.getLine(pos.line);
				if (line.hasOnlyWhiteSpaceBeforeIndex(pos.ch)) {
					moveToEndOfPreviousLine();
				} else {
					editor.setCursor({ line: pos.line, ch: pos.ch - 1 });
				}
			}

			let newPos = editor.getCursor();
			let lineInvalids = invalids[newPos.line];
			if (lineInvalids) {
				let mark = lineInvalids[newPos.ch];
				if (mark) {
					mark.clear();
					lineInvalids.splice(newPos.ch, 1);
				}
			}

			updateIncompleteMark();
		} else if (event.keyCode == 13) { // enter
			result = true;

			let pos = editor.getCursor();
			if (pos.line != editor.doc.size - 1) {
				let currentLine = editor.doc.getLine(pos.line);
				let trimmed = currentLine.trim();
				if (editor.getCursor().ch >= currentLine.indexOf(trimmed) + trimmed.length) {
					let newLine = pos.line + 1;
					let text = editor.doc.getLine(newLine);
					let ch = text.indexOf(text.trim());
					editor.setCursor({ line: newLine, ch: ch });
					updateIncompleteMark();
				}
			}
		}

		if (result) {
			event.preventDefault();
		}
	}
});

function moveToEndOfPreviousLine() {
	let pos = editor.getCursor();
	if (pos.line > 0) {
		let newLine = pos.line - 1;
		let text = editor.doc.getLine(newLine);
		let trimmed = text.trim();
		let ch = text.indexOf(trimmed) + trimmed.length;
		editor.setCursor({ line: newLine, ch: ch });
	}
}

function isComplete() {
	if (incompleteMark.lines.length != 0) {
		return false;
	}

	for (var i = 0; i < invalids.length; i++) {
		let arr = invalids[i];
		for (var j = 0; j < arr.length; j++) {
			if (arr[j]) {
				return false;
			}
		}
	}
	return true;
}

function getEndPos() {
	return { line: editor.doc.size, ch: editor.doc.getLine(editor.doc.size - 1).length };
}

function updateIncompleteMark() {
	incompleteMark.clear();
	incompleteMark = editor.doc.markText(editor.getCursor(), getEndPos(), {
		className: "incomplete"
	});
}

String.prototype.hasOnlyWhiteSpaceBeforeIndex = function(index) {
	return this.substring(index) == this.trim();
};