From ce0fba0947dc769b1e9e2e9297d7b464135bfa3d Mon Sep 17 00:00:00 2001
From: Victor Shcherb <victor.shcherb@gmail.com>
Date: Fri, 12 Feb 2021 12:35:59 +0100
Subject: [PATCH] Add methods to calculate precision xy

---
 .../main/java/net/osmand/util/MapUtils.java   | 41 +++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/OsmAnd-java/src/main/java/net/osmand/util/MapUtils.java b/OsmAnd-java/src/main/java/net/osmand/util/MapUtils.java
index 7a37eee3aa..a9c3411b68 100644
--- a/OsmAnd-java/src/main/java/net/osmand/util/MapUtils.java
+++ b/OsmAnd-java/src/main/java/net/osmand/util/MapUtils.java
@@ -48,6 +48,47 @@ public class MapUtils {
         'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '_', '~'
     };
+    
+	public static int calculateFromBaseZoomPrecisionXY(int bazeZoom, int finalZoom, int xBase, int yBase) {
+		int px = xBase;
+		int py = yBase;
+		int precisionNumber = 1;
+		for (int zoom = finalZoom - 1; zoom >= bazeZoom; zoom--) {
+			int x = px / 2; // (int) MapUtils.getTileNumberX(zoom, lon);
+			int y = py / 2; // (int) MapUtils.getTileNumberY(zoom, lat);
+			int deltax = px - x * 2;
+			int deltay = py - y * 2;
+			precisionNumber = (precisionNumber << 2) + (deltax << 1) + deltay;
+			// StringBuilder spaces = new StringBuilder();
+			// for (int i = 0; i < 32 - zoom; i++) {
+			//	spaces.append(' ');
+			// }
+			// System.out.println(String.format("%d %s + %d %s %s + %d", zoom, Integer.toBinaryString(x), deltax, spaces.toString(), Integer.toBinaryString(y), deltay));
+			px = x;
+			py = y;
+		}
+		System.out.println(String.format("Bits: %d %s (%d)", Integer.toBinaryString(precisionNumber).length(), Integer.toBinaryString(precisionNumber), precisionNumber));
+		return precisionNumber;
+	}
+
+	public static int[] calculateFinalXYFromBaseAndPrecisionXY(int bazeZoom, int finalZoom,
+			int precisionXY, int xBase, int yBase, boolean ignoreNotEnoughPrecision) {
+		// System.out.println(String.format("Base x, y at zoom %d: %d %d", zoomToStart, xBaseApproximation, yBaseApproximation));
+		// calculate finish approximation using precisionNumber
+		int finalX = xBase;
+		int finalY = yBase;
+		int precisionCalc = precisionXY;
+		for (int zoom = bazeZoom; zoom < finalZoom; zoom++) {
+			if (precisionCalc <= 1 && precisionCalc > 0 && !ignoreNotEnoughPrecision) {
+				 throw new IllegalArgumentException("Not enough bits to retrieve zoom approximation");
+			}
+			finalY = finalY * 2 + (precisionXY & 1);
+			finalX = finalX * 2 + ((precisionXY & 2) >> 1);
+			precisionXY = precisionXY >> 2;
+		}
+		// System.out.println(String.format("Calc x, y at zoom %d: %d %d", finalZoom, finalX, finalY));
+		return new int[] { finalX, finalY };
+	}