/**
 * Provide effect for line
 * @module echarts/chart/helper/EffectLine
 */

import Polyline from './Polyline';
import * as zrUtil from 'zrender/core/util';
import EffectLine from './EffectLine';
import * as vec2 from 'zrender/core/vector';

/**
 * @constructor
 * @extends {module:echarts/chart/helper/EffectLine}
 * @alias {module:echarts/chart/helper/Polyline}
 */
function EffectPolyline(lineData, idx, seriesScope) {
    EffectLine.call(this, lineData, idx, seriesScope);
    this._lastFrame = 0;
    this._lastFramePercent = 0;
}

var effectPolylineProto = EffectPolyline.prototype;

// Overwrite
effectPolylineProto.createLine = function (lineData, idx, seriesScope) {
    return new Polyline(lineData, idx, seriesScope);
};

// Overwrite
effectPolylineProto.updateAnimationPoints = function (symbol, points) {
    this._points = points;
    var accLenArr = [0];
    var len = 0;
    for (var i = 1; i < points.length; i++) {
        var p1 = points[i - 1];
        var p2 = points[i];
        len += vec2.dist(p1, p2);
        accLenArr.push(len);
    }
    if (len === 0) {
        return;
    }

    for (var i = 0; i < accLenArr.length; i++) {
        accLenArr[i] /= len;
    }
    this._offsets = accLenArr;
    this._length = len;
};

// Overwrite
effectPolylineProto.getLineLength = function (symbol) {
    return this._length;
};

// Overwrite
effectPolylineProto.updateSymbolPosition = function (symbol) {
    var t = symbol.__t;
    var points = this._points;
    var offsets = this._offsets;
    var len = points.length;

    if (!offsets) {
        // Has length 0
        return;
    }

    var lastFrame = this._lastFrame;
    var frame;

    if (t < this._lastFramePercent) {
        // Start from the next frame
        // PENDING start from lastFrame ?
        var start = Math.min(lastFrame + 1, len - 1);
        for (frame = start; frame >= 0; frame--) {
            if (offsets[frame] <= t) {
                break;
            }
        }
        // PENDING really need to do this ?
        frame = Math.min(frame, len - 2);
    }
    else {
        for (var frame = lastFrame; frame < len; frame++) {
            if (offsets[frame] > t) {
                break;
            }
        }
        frame = Math.min(frame - 1, len - 2);
    }

    vec2.lerp(
        symbol.position, points[frame], points[frame + 1],
        (t - offsets[frame]) / (offsets[frame + 1] - offsets[frame])
    );

    var tx = points[frame + 1][0] - points[frame][0];
    var ty = points[frame + 1][1] - points[frame][1];
    symbol.rotation = -Math.atan2(ty, tx) - Math.PI / 2;

    this._lastFrame = frame;
    this._lastFramePercent = t;

    symbol.ignore = false;
};

zrUtil.inherits(EffectPolyline, EffectLine);

export default EffectPolyline;