JSWarrior by FusionCharts - solution lvl7 - see http://jswarrior.fusioncharts.com/

jswarrior.js

jsWarrior.turn = function (warrior) {

    warrior.underAttack = warrior.previousHealth > warrior.getHealth();
    warrior.timeToRetreat = warrior.getHealth() <= 10;
    warior.retreating = warrior.retreating || false;

    // Start
    if (!warrior.started) {
        warrior.started = true;
        warrior.pivot();
        return;
    }

    // Normal move
    if (warrior.check() == 'wall') {
        warrior.pivot();
    } else if (warrior.check() == 'diamond') {
        warrior.collect();
    } else if (warrior.check() == "enemy") {
        warrior.attack();
    } else {
        if ((warrior.timeToRetreat && !warrior.retreating) || warrior.retreating) {
            warrior.retreating = true;
            if (warrior.underAttack) {
                warrior.walk('backward');
            } else {
                warrior.rest();

                if (warrior.getHealth() == 20) {
                    warrior.retreating = false;
                }
            }
        } else {
            warrior.walk();
        }
    }

    // #LT
    warrior.previousHealth = warrior.getHealth();
}