/**
 * @file 遍历路径的路径集合，包括segment和 bezier curve
 * @author mengke01(kekee000@gmail.com)
 */



/**
 * 遍历路径的路径集合
 *
 * @param {Array} contour 坐标点集
 * @param {Function} callBack 回调函数，参数集合：command, p0, p1, p2, i
 * p0, p1, p2 直线或者贝塞尔曲线参数
 * i 当前遍历的点
 * 其中command = L 或者 Q，表示直线或者贝塞尔曲线
 */
function pathIterator(contour, callBack) {

    var curPoint;
    var prevPoint;
    var nextPoint;
    var cursorPoint; // cursorPoint 为当前单个绘制命令的起点

    for (var i = 0, l = contour.length; i < l; i++) {
        curPoint = contour[i];
        prevPoint = i === 0 ? contour[l - 1] : contour[i - 1];
        nextPoint =  i === l - 1 ? contour[0] : contour[i + 1];

        // 起始坐标
        if (i === 0) {
            if (curPoint.onCurve) {
                cursorPoint = curPoint;
            }
            else {
                if (prevPoint.onCurve) {
                    cursorPoint = prevPoint;
                }
                else {
                    cursorPoint = {
                        x: (prevPoint.x + curPoint.x) / 2,
                        y: (prevPoint.y + curPoint.y) / 2
                    };
                }
            }
        }

        // 直线
        if (curPoint.onCurve && nextPoint.onCurve) {
            if (false === callBack('L', curPoint, nextPoint, 0, i)) {
                break;
            }
            cursorPoint = nextPoint;
        }
        else if (!curPoint.onCurve) {

            if (nextPoint.onCurve) {
                if (false === callBack('Q', cursorPoint, curPoint, nextPoint, i)) {
                    break;
                }
                cursorPoint = nextPoint;
            }
            else {
                var last = {
                    x: (curPoint.x + nextPoint.x) / 2,
                    y: (curPoint.y + nextPoint.y) / 2
                };
                if (false === callBack('Q', cursorPoint, curPoint, last, i)) {
                    break;
                }
                cursorPoint = last;
            }
        }
    }
}

module.exports = pathIterator;
    
