BlueToothLogger/app/src/main/java/com/wytehat/btlogger/BluetoothRadarView.java

package com.wytehat.btlogger;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RadialGradient;
import android.graphics.Shader;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.view.View;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;

public class BluetoothRadarView extends View {
    public interface Listener { void onTargetSelected(String address); }

    public static class Target {
        public String address;
        public String name;
        public int rssi;
        float x, y;
        public Target(String address, String name, int rssi) {
            this.address = address; this.name = name; this.rssi = rssi;
        }
    }

    private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private final ArrayList<Target> targets = new ArrayList<Target>();
    private final HashMap<String, Float> targetAngles = new HashMap<String, Float>();
    private final HashMap<String, Float> displayedRadii = new HashMap<String, Float>();
    private Listener listener;

    private boolean scanning;
    private final ScaleGestureDetector scaleDetector;
    private float zoom = 1.0f;
    private boolean suppressTap;
    private double sweepAngle = -90.0;

    /* Draw-time scratch, reused every frame -- see onDraw. */
    private android.graphics.RadialGradient glow;
    private float glowCx = -1f, glowCy = -1f, glowR = -1f;
    private final ArrayList<Target> ordered = new ArrayList<Target>();
    private final Comparator<Target> byAngle = new Comparator<Target>() {
        public int compare(Target first, Target second) {
            float a = angleFor(first.address);
            float b = angleFor(second.address);
            return a < b ? -1 : (a > b ? 1 : 0);
        }
    };
    public BluetoothRadarView(Context context) {
        super(context);
        scaleDetector = new ScaleGestureDetector(context, new ScaleGestureDetector.SimpleOnScaleGestureListener() {
            public boolean onScaleBegin(ScaleGestureDetector detector) { suppressTap = true; return true; }
            public boolean onScale(ScaleGestureDetector detector) {
                zoom = clamp(zoom * detector.getScaleFactor(), 1.0f, 3.5f);
                invalidate();
                return true;
            }
        });
        paint.setTypeface(android.graphics.Typeface.create("sans", android.graphics.Typeface.NORMAL));
        setBackgroundColor(Color.rgb(4, 24, 29));
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    }
    public synchronized void setScanning(boolean value) {
        if (value && !scanning) zoom = 1.0f;
        scanning = value;
        invalidate();
    }


    public void setListener(Listener value) { listener = value; }

    public synchronized void setTargets(List<Target> values) {
        for (int i = 0; i < values.size(); i++) {
            Target target = values.get(i);
            if (!targetAngles.containsKey(target.address))
                targetAngles.put(target.address, Float.valueOf(findOpenAngle(target.address)));
        }
        targets.clear(); targets.addAll(values);
        // While scanning, onDraw already re-posts itself every 33ms; an
        // extra invalidate per update just forces redundant frames.
        if (!scanning) invalidate();
    }

    protected synchronized void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        float cx = getWidth() / 2f;
        float cy = getHeight() / 2f;
        canvas.save();
        canvas.scale(zoom, zoom, cx, cy);
        float radius = Math.min(cx, cy) - 34;
        float glowRadius = radius + 34f;
        float edgeStop = radius / glowRadius;
        paint.setStyle(Paint.Style.FILL);
        // Rebuilt only when the geometry moves. This used to allocate a
        // six-stop gradient and two arrays on every frame of a 30fps sweep.
        if (glow == null || glowCx != cx || glowCy != cy || glowR != glowRadius) {
            glow = new android.graphics.RadialGradient(cx, cy, glowRadius,
                new int[] { Color.TRANSPARENT, Color.argb(5, 35, 180, 110), Color.argb(24, 45, 225, 140), Color.argb(48, 55, 235, 150), Color.argb(18, 35, 190, 120), Color.TRANSPARENT },
                new float[] { 0f, 0.55f, edgeStop - 0.05f, edgeStop, edgeStop + 0.10f, 1f }, android.graphics.Shader.TileMode.CLAMP);
            glowCx = cx; glowCy = cy; glowR = glowRadius;
        }
        paint.setShader(glow);
        canvas.drawCircle(cx, cy, glowRadius, paint);
        paint.setShader(null);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(2.4f);
        paint.setColor(Color.argb(95, 55, 220, 145));
        paint.setShadowLayer(12f, 0f, 0f, Color.argb(65, 45, 225, 145));
        canvas.drawCircle(cx, cy, radius, paint);
        paint.clearShadowLayer();
        paint.setColor(Color.argb(22, 65, 225, 155));
        paint.setStrokeWidth(6f);
        for (int i = 1; i <= 4; i++) canvas.drawCircle(cx, cy, radius * i / 4f, paint);
        paint.setColor(Color.rgb(38, 145, 110));
        paint.setStrokeWidth(2.8f);
        for (int i = 1; i <= 4; i++) canvas.drawCircle(cx, cy, radius * i / 4f, paint);
        paint.setColor(Color.argb(28, 55, 205, 145)); paint.setStrokeWidth(3.5f);
        canvas.drawLine(cx - radius, cy, cx + radius, cy, paint);
        canvas.drawLine(cx, cy - radius, cx, cy + radius, paint);
        paint.setColor(Color.rgb(35, 125, 100)); paint.setStrokeWidth(1.8f);
        canvas.drawLine(cx - radius, cy, cx + radius, cy, paint);
        canvas.drawLine(cx, cy - radius, cx, cy + radius, paint);

        if (scanning) sweepAngle = (System.currentTimeMillis() % 6000L) * 360.0 / 6000.0 - 90.0;
        double angle = sweepAngle + 90.0;
        double radians = Math.toRadians(angle - 90);
        float sweepX = cx + (float)Math.cos(radians) * radius;
        float sweepY = cy + (float)Math.sin(radians) * radius;
        paint.setColor(Color.argb(35, 70, 255, 170)); paint.setStrokeWidth(16);
        canvas.drawLine(cx, cy, sweepX, sweepY, paint);
        paint.setColor(Color.argb(85, 70, 255, 170)); paint.setStrokeWidth(8);
        canvas.drawLine(cx, cy, sweepX, sweepY, paint);
        paint.setColor(Color.rgb(65, 255, 170)); paint.setStrokeWidth(2.5f);
        canvas.drawLine(cx, cy, sweepX, sweepY, paint);

        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.WHITE);
        canvas.drawCircle(cx, cy, 7, paint);
        paint.setTextAlign(Paint.Align.CENTER);
        paint.setTextSize(12 * getResources().getDisplayMetrics().scaledDensity);
        canvas.drawText("YOU", cx, cy + 24, paint);
        // Reused across frames; a fresh list and comparator per frame is
        // pure garbage at 30fps.
        ordered.clear();
        ordered.addAll(targets);
        Collections.sort(ordered, byAngle);
        float density = getResources().getDisplayMetrics().scaledDensity;
        for (int i = 0; i < ordered.size(); i++) {
            Target target = ordered.get(i);
            float degrees = angleFor(target.address);
            double targetAngle = Math.toRadians(degrees);
            float desiredRadius = radius * radialPosition(target.rssi);
            Float previous = displayedRadii.get(target.address);
            float shownRadius = previous == null ? desiredRadius : previous.floatValue() + (desiredRadius - previous.floatValue()) * 0.055f;
            displayedRadii.put(target.address, Float.valueOf(shownRadius));
            float cos = (float)Math.cos(targetAngle);
            float sin = (float)Math.sin(targetAngle);
            target.x = cx + cos * shownRadius;
            target.y = cy + sin * shownRadius;
            paint.setStyle(Paint.Style.FILL);
            paint.setColor(target.rssi >= -60 ? Color.rgb(255, 70, 70) : target.rssi >= -80 ? Color.rgb(255, 180, 40) : Color.rgb(40, 150, 255));
            canvas.drawCircle(target.x, target.y, 9, paint);

            paint.setTextSize(9.5f * density);
            paint.setTextAlign(Paint.Align.CENTER);
            String label = target.name == null ? "Unknown" : target.name;
            if (label.length() > 14) label = label.substring(0, 14);
            String signal = target.rssi + " dBm";
            float textWidth = Math.max(paint.measureText(label), paint.measureText(signal));
            int lane = target.address == null ? 0 : Math.abs(target.address.hashCode() / 360) % 5 - 2;
            float shift = lane * 10f * density;
            float labelX = target.x + cos * (15f + textWidth / 2f) - sin * shift;
            float labelY = target.y + sin * (17f + 12f * density) + cos * shift;
            labelX = clamp(labelX, textWidth / 2f + 3f, getWidth() - textWidth / 2f - 3f);
            labelY = clamp(labelY, 12f * density, getHeight() - 12f * density);
            paint.setColor(Color.WHITE);
            paint.setShadowLayer(3f, 1f, 1f, Color.BLACK);
            canvas.drawText(label, labelX, labelY - 2f, paint);
            paint.setTextSize(8.5f * density);
            canvas.drawText(signal, labelX, labelY + 10f * density, paint);
            paint.clearShadowLayer();
        }
        canvas.restore();
        if (scanning) postInvalidateDelayed(33);
    }

    public synchronized boolean onTouchEvent(MotionEvent event) {
        if (event.getActionMasked() == MotionEvent.ACTION_DOWN && getParent() != null)
            getParent().requestDisallowInterceptTouchEvent(true);
        scaleDetector.onTouchEvent(event);
        if (event.getPointerCount() > 1) { suppressTap = true; return true; }
        if (event.getAction() != MotionEvent.ACTION_UP) return true;
        if (suppressTap) { suppressTap = false; return true; }
        float cx = getWidth() / 2f;
        float cy = getHeight() / 2f;
        float touchX = cx + (event.getX() - cx) / zoom;
        float touchY = cy + (event.getY() - cy) / zoom;
        Target closest = null;
        float best = Float.MAX_VALUE;
        for (int i = 0; i < targets.size(); i++) {
            Target target = targets.get(i);
            float dx = touchX - target.x;
            float dy = touchY - target.y;
            float distance = dx * dx + dy * dy;
            if (distance < best) { best = distance; closest = target; }
        }
        float limit = 48 * getResources().getDisplayMetrics().density / zoom;
        if (closest != null && best <= limit * limit && listener != null)
            listener.onTargetSelected(closest.address);
        return true;
    }

    private float angleFor(String address) {
        Float value = targetAngles.get(address);
        if (value != null) return value.floatValue();
        float created = findOpenAngle(address);
        targetAngles.put(address, Float.valueOf(created));
        return created;
    }

    private float findOpenAngle(String address) {
        if (targetAngles.isEmpty()) return address == null ? -90f : (Math.abs(address.hashCode()) % 360) - 90f;
        float bestAngle = 0f;
        float bestGap = -1f;
        for (int candidate = 0; candidate < 360; candidate += 5) {
            float nearest = 360f;
            for (Float used : targetAngles.values()) nearest = Math.min(nearest, circularDistance(candidate, used.floatValue()));
            if (nearest > bestGap) { bestGap = nearest; bestAngle = candidate; }
        }
        return bestAngle;
    }

    private float circularDistance(float first, float second) {
        float difference = Math.abs(first - second) % 360f;
        return Math.min(difference, 360f - difference);
    }

    private float radialPosition(int rssi) {
        return clamp((-rssi - 45f) / 60f, 0.12f, 0.94f);
    }

    private float clamp(float value, float min, float max) {
        return Math.max(min, Math.min(max, value));
    }
}