var detectArrowKeys = function()

in lib/ace/keyboard/textinput.js [682:744]
58 lines of code
29 McCabe index (conditional complexity)

        var detectArrowKeys = function(e) {
            if (document.activeElement !== text) return;
            if (typing || inComposition || host.$mouseHandler.isMousePressed) return;

            if (copied) {
                return;
            }
            var selectionStart = text.selectionStart;
            var selectionEnd = text.selectionEnd;
            
            var key = null;
            var modifier = 0;
            // console.log(selectionStart, selectionEnd);
            if (selectionStart == 0) {
                key = KEYS.up;
            } else if (selectionStart == 1) {
                key = KEYS.home;
            } else if (selectionEnd > lastSelectionEnd && lastValue[selectionEnd] == "\n") {
                key = KEYS.end;
            } else if (selectionStart < lastSelectionStart && lastValue[selectionStart - 1] == " ") {
                key = KEYS.left;
                modifier = MODS.option;
            } else if (
                selectionStart < lastSelectionStart
                || (
                    selectionStart == lastSelectionStart 
                    && lastSelectionEnd != lastSelectionStart
                    && selectionStart == selectionEnd
                )
            ) {
                key = KEYS.left;
            } else if (selectionEnd > lastSelectionEnd && lastValue.slice(0, selectionEnd).split("\n").length > 2) {
                key = KEYS.down;
            } else if (selectionEnd > lastSelectionEnd && lastValue[selectionEnd - 1] == " ") {
                key = KEYS.right;
                modifier = MODS.option;
            } else if (
                selectionEnd > lastSelectionEnd
                || (
                    selectionEnd == lastSelectionEnd 
                    && lastSelectionEnd != lastSelectionStart
                    && selectionStart == selectionEnd
                )
            ) {
                key = KEYS.right;
            }
            
            if (selectionStart !== selectionEnd)
                modifier |= MODS.shift;

            if (key) {
                var result = host.onCommandKey({}, modifier, key);
                if (!result && host.commands) {
                    key = KEYS.keyCodeToString(key);
                    var command = host.commands.findKeyCommand(modifier, key);
                    if (command)
                        host.execCommand(command);
                }
                lastSelectionStart = selectionStart;
                lastSelectionEnd = selectionEnd;
                resetSelection("");
            }
        };