/**
 * A View implementation that displays a scatter graph with 
 * automatic unit scaling.
 * 
 * Call the <i>setupGraph()</i> method to modify the graph's
 * properties.
 * @author Antoine Grondin
 *
 */

public class GraphView extends View {

    //////////////////////////////////////////////////////////////////
    // Configuration
    //////////////////////////////////////////////////////////////////

    // Set to true to impose the graph properties
    private static final boolean TEST = false;  

    // Scale configuration
    private float minX = 0;         // When TEST is true,these values are used to
    private float maxX = 50;        // Draw the graph
    private float minY = 0;
    private float maxY = 100;

    private String titleText = "A Graph...";
    private String xUnitText = "s";
    private String yUnitText = "Volts";

    // Debugging variables
    private boolean D = true;
    private String TAG = "GraphView";

    //////////////////////////////////////////////////////////////////
    // Member fields
    //////////////////////////////////////////////////////////////////

    // Represent the borders of the View
    private int mTopSide = 0;
    private int mLeftSide = 0;
    private int mRightSide = 0;
    private int mBottomSide = 0;
    private int mMiddleX = 0;
    // Size of a DensityIndependentPixel
    private float mDips = 0;

    // Hold the position of the axis in regard to the range of values
    private int positionOfX = 0;
    private int positionOfY = 0;

    // Index for the graph array window,and size of the window
    private int windowStart = 0;
    private int windowSize = 128;
    private float[] dataSource;

    // Painting tools
    private Paint xAxisPaint;
    private Paint yAxisPaint;
    private Paint tickPaint;
    private Paint curvePaint;
    private Paint backgroundPaint;

    private TextPaint unitTextPaint;
    private TextPaint titleTextPaint;

    // Object to be drawn

    private Path curve;
    private Bitmap background;

    ///////////////////////////////////////////////////////////////////////////////
    // Constructors
    ///////////////////////////////////////////////////////////////////////////////

    public GraphView(Context context) {
        super(context);
        init();
    }

    public GraphView(Context context,AttributeSet attrs){
        super(context,attrs);
        init();
    }

    public GraphView(Context context,AttributeSet attrs,int defStyle){
        super(context,attrs,defStyle);
        init();
    }

    ///////////////////////////////////////////////////////////////////////////////
    // Configuration methods
    /////////////////////////////////////////////////////////////////////////////// 

    public void setupGraph(String title,String nameOfX,float min_X,float max_X,String nameOfY,float min_Y,float max_Y){
        if(!TEST){
            titleText = title;
            xUnitText = nameOfX;
            yUnitText = nameOfY;
            minX = min_X;
            maxX = max_X;
            minY = min_Y;
            maxY = max_Y;
        }
    }

    /**
     * Set the array this GraphView is to work with.
     * @param data is a float array of length > windowSize.  The floats must range between 0.0 and 1.0.
     * A value of 0.0 will be drawn at the bottom of the graph,while a value of 1.0 will be drawn at 
     * the top of the graph.  The range is not tested,or your
     * graph will look terrible.
     *      0.0  : draw at the bottom of the graph
     *      0.5  : draw in the middle of the graph
     *      1.0  : draw at the top of the graph
     */
    public void setDataSource(float[] data){
        this.dataSource = data;
    }

    ///////////////////////////////////////////////////////////////////////////////
    // Initialization methods
    /////////////////////////////////////////////////////////////////////////////// 

    private void init(){
        initDrawingTools();
    }

    private void initConstants(){
        mDips = getResources().getDisplayMetrics().density;
        mTopSide = (int) (getTop() + 10*mDips);
        mLeftSide = (int) (getLeft() + 10*mDips);
        mRightSide = (int) (getMeasuredWidth() - 10*mDips);
        mBottomSide = (int) (getMeasuredHeight() - 10*mDips);
        mMiddleX = (mRightSide - mLeftSide)/2 + mLeftSide;
    }

    private void initWindowSetting() throws IllegalArgumentException {

        // Don't do anything if the given values make no sense
        if(maxX < minX || maxY < minY ||
                maxX == minX || maxY == minY){
            throw new IllegalArgumentException("Max and min values make no sense");
        }
        // Transform the values in scanable items
        float[][] maxAndMin = new float[][]{
                {minX,maxX},{minY,maxY}};
        int[] positions = new int[]{positionOfY,positionOfX};

        // Place the X and Y axis in regard to the given max and min
        for(int i = 0; i<2; i++){
            if(maxAndMin[i][0] < 0f){
                if(maxAndMin[i][1] < 0f){
                    positions[i] = (int) maxAndMin[i][0];
                } else{
                    positions[i] = 0;
                }
            } else if (maxAndMin[i][0] > 0f){
                positions[i] = (int) maxAndMin[i][0];
            } else {
                positions[i] = 0;
            }
        }

        // Put the values back in their right place
        minX = maxAndMin[0][0];
        maxX = maxAndMin[0][1];
        minY = maxAndMin[1][0];
        maxY = maxAndMin[1][1];

        positionOfY = mLeftSide +  (int) (((positions[0] - minX)/(maxX-minX))*(mRightSide - mLeftSide));    
        positionOfX = mBottomSide - (int) (((positions[1] - minY)/(maxY-minY))*(mBottomSide - mTopSide));
    }

    private void initDrawingTools(){

        xAxisPaint = new Paint();
        xAxisPaint.setColor(0xff888888);
        xAxisPaint.setStrokeWidth(1f*mDips);
        xAxisPaint.setAlpha(0xff);
        xAxisPaint.setAntiAlias(true);

        yAxisPaint = xAxisPaint;

        tickPaint = xAxisPaint;
        tickPaint.setColor(0xffaaaaaa);

        curvePaint = new Paint();
        curvePaint.setColor(0xff00ff00);
        curvePaint.setStrokeWidth(1f*mDips);
        curvePaint.setDither(true);
        curvePaint.setStyle(Paint.Style.STROKE);
        curvePaint.setStrokeJoin(Paint.Join.ROUND);
        curvePaint.setStrokeCap(Paint.Cap.ROUND);
        curvePaint.setPathEffect(new CornerPathEffect(10));
        curvePaint.setAntiAlias(true);

        backgroundPaint = new Paint();
        backgroundPaint.setFilterBitmap(true);

        titleTextPaint = new TextPaint();
        titleTextPaint.setAntiAlias(true);
        titleTextPaint.setColor(0xffffffff);
        titleTextPaint.setTextAlign(Align.CENTER);
        titleTextPaint.setTextSize(20f*mDips);
        titleTextPaint.setTypeface(Typeface.MONOSPACE);

        unitTextPaint = new TextPaint();
        unitTextPaint.setAntiAlias(true);
        unitTextPaint.setColor(0xff888888);
        unitTextPaint.setTextAlign(Align.CENTER);
        unitTextPaint.setTextSize(20f*mDips);
        unitTextPaint.setTypeface(Typeface.MONOSPACE);

    }

    ///////////////////////////////////////////////////////////////////////////////
    // Overridden methods
    /////////////////////////////////////////////////////////////////////////////// 

    protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec){
        super.onMeasure(widthMeasureSpec,heightMeasureSpec);
    }

    protected void onSizeChanged(int w,int h,int oldw,int oldh) {
        regenerateBackground();
    }

    public void onDraw(Canvas canvas){
        drawBackground(canvas);
        if(dataSource != null)
            drawCurve(canvas,dataSource);
    }

    ///////////////////////////////////////////////////////////////////////////////
    // Drawing methods
    /////////////////////////////////////////////////////////////////////////////// 

    private void drawX(Canvas canvas){
        canvas.drawLine(mLeftSide,positionOfX,mRightSide,xAxisPaint);
        canvas.drawText(xUnitText,mRightSide -  unitTextPaint.measureText(xUnitText)/2,positionOfX - unitTextPaint.getTextSize()/2,unitTextPaint);
    }

    private void drawY(Canvas canvas){
        canvas.drawLine(positionOfY,mTopSide,positionOfY,mBottomSide,yAxisPaint);
        canvas.drawText(yUnitText,positionOfY + unitTextPaint.measureText(yUnitText)/2 + 4*mDips,mTopSide + (int) (unitTextPaint.getTextSize()/2),unitTextPaint);
    }

    private void drawTick(Canvas canvas){
        // No tick at this time
        // TODO decide how I want to put those ticks,if I want them
    }

    private void drawTitle(Canvas canvas){
        canvas.drawText(titleText,mMiddleX,mTopSide + (int) (titleTextPaint.getTextSize()/2),titleTextPaint);
    }

    /**
     * Read a buffer array of size greater than "windowSize" and create a window array out of it.
     * A curve is then drawn from this array using "windowSize" points,from left
     * to right.
     * @param canvas is a Canvas object on which the curve will be drawn.  Ensure the canvas is the
     * later drawn object at its position or you will not see your curve.
     * @param data is a float array of length > windowSize.  The floats must range between 0.0 and 1.0.
     * A value of 0.0 will be drawn at the bottom of the graph,or your
     * graph will look terrible. 
     *      0.0  : draw at the bottom of the graph
     *      0.5  : draw in the middle of the graph
     *      1.0  : draw at the top of the graph
     */
    private void drawCurve(Canvas canvas,float[] data){

        // Create a reference value to determine the stepping between each points to be drawn
        float incrementX = (mRightSide-mLeftSide)/(float) windowSize;

        float incrementY = mBottomSide - mTopSide;

        // Prepare the array for the graph
        float[] source = prepareWindowArray(data);

        // Prepare the curve Path
        curve = new Path();
        // Move at the first point.
        curve.moveTo(mLeftSide,source[0]*incrementY);
        // Draw the remaining points of the curve
        for(int i = 1; i < windowSize; i++){
            curve.lineTo(mLeftSide + (i*incrementX),source[i] * incrementY);
        }

        canvas.drawPath(curve,curvePaint);
    }

    ///////////////////////////////////////////////////////////////////////////////
    // Intimate methods
    /////////////////////////////////////////////////////////////////////////////// 

    /**
     * When asked to draw the background,this method will verify if a bitmap of the
     * background is available.  If not,it will regenerate one.  Then,it will draw
     * the background using this bitmap.  The use of a bitmap to draw the background
     * is to avoid unnecessary processing for static parts of the view.
     */
    private void drawBackground(Canvas canvas){
        if(background == null){
            regenerateBackground();
        } 
        canvas.drawBitmap(background,backgroundPaint);
    }

    /**
     * Call this method to force the <i>GraphView</i> to redraw the cache of it's background,* using new properties if you changed them with <i>setupGraph()</i>.
     */
    public void regenerateBackground(){
        initConstants();
        try{
            initWindowSetting();
        } catch (IllegalArgumentException e){
            Log.e(TAG,"Could not initalize windows.",e);
            return;
        }
        if(background != null){
            background.recycle();
        }
        background = Bitmap.createBitmap(getWidth(),getHeight(),Bitmap.Config.ARGB_8888);
        Canvas backgroundCanvas = new Canvas(background);

        drawX(backgroundCanvas);
        drawY(backgroundCanvas);
        drawTick(backgroundCanvas);
        drawTitle(backgroundCanvas);

    }

    /**
     * Extract a window array from the data array,and reposition the windowStart 
     * index for next iteration
     * @param data the array of data from which we get the window
     * @return an array of float that represent the window
     */
    private float[] prepareWindowArray(float[] data){
        // Prepare the source array for the graph.
        float[] source = new float[windowSize];

        // Copy the window from the data array into the source array
        for(int i = 0; i < windowSize; i++){
            if(windowStart+i < data.length)                         // If the windows holds within the data array
                source[i] = data[windowStart + i];                  // Simply copy the value in the source array
            else{                                                   // If the window goes beyond the data array
                source[i] = data[(windowStart + 1)%data.length];    // Loop at the beginning of the data array and copy from there
            }
        }
        // Reposition the buffer index
        windowStart = windowStart + windowSize;
        // If the index is beyond the end of the array
        if(windowStart >= data.length){
            windowStart = windowStart % data.length;
        }

        return source;
    }
}