Merge pull request #76 from ndsev/tile-id-neighbor

Implement TileId::neighbor() including test.
ndsev · Aug 9, 2024 · 40317c2 · 40317c2
2 parents f5a8825 + 225cc44
commit 40317c2
Show file tree

Hide file tree

Showing 3 changed files with 51 additions and 1 deletion.
diff --git a/libs/model/include/mapget/model/tileid.h b/libs/model/include/mapget/model/tileid.h
@@ -41,6 +41,13 @@ struct TileId
      */
     static TileId fromWgs84(double longitude, double latitude, uint16_t zoomLevel);
 
+    /**
+     * Get the neighbor for a mapget tile id. Tile row will be clamped to [0, maxForLevel],
+     * so a positive/negative wraparound is not possible. The tile id column will wrap at the
+     * antimeridian. Note: The implementation will only work for offset values [-1, 0, 1].
+     */
+    [[nodiscard]] TileId neighbor(int32_t offsetX, int32_t offsetY) const;
+
     /**
      * Get the center of the tile in Wgs84.
      */

diff --git a/libs/model/src/tileid.cpp b/libs/model/src/tileid.cpp
@@ -1,6 +1,7 @@
 #include "tileid.h"
-#include <cmath>
 #include <algorithm>
+#include <cmath>
+#include "mapget/log.h"
 
 namespace mapget
 {
@@ -68,6 +69,30 @@ TileId TileId::fromWgs84(double longitude, double latitude, uint16_t zoomLevel)
     return {(uint16_t)x, (uint16_t)y, zoomLevel};
 }
 
+TileId TileId::neighbor(int32_t offsetX, int32_t offsetY) const
+{
+    if (glm::abs(offsetX) > 1 || glm::abs(offsetY) > 1) {
+        raise("TileId::neighbor() called with offset value greater than 1 or less than -1.");
+    }
+
+    auto const maxCol = static_cast<int64_t>(1ull << (z() + 1)) - 1;
+    auto const maxRow = static_cast<int64_t>(1ull << z()) - 1;
+
+    auto resultX = x();
+    auto resultY = y();
+
+    if (offsetX == -1 && resultX == 0)
+        resultX = maxCol;
+    else if (offsetX == 1 && resultX == maxCol)
+        resultX = 0;
+    else
+        resultX += offsetX;
+
+    if (offsetY == -1 && resultY > 0 || offsetY == 1 && resultY < maxRow)
+        resultY += offsetY;
+    return TileId(resultX, resultY, z()).value_;
+}
+
 Point TileId::center() const {
     auto extent = size();
     auto lon = MIN_LON + (static_cast<double>(x()) + 0.5) * extent.x;

diff --git a/test/unit/test-model.cpp b/test/unit/test-model.cpp
@@ -372,4 +372,22 @@ TEST_CASE("TileId", "[TileId]") {
         REQUIRE_EQUAL(tile.ne(), {0, 90});
         REQUIRE_EQUAL(tile.size(), {180, 180});
     }
+
+    SECTION("Neighbor") {
+        TileId tile(0, 0, 1);
+        REQUIRE(tile.neighbor(1, 0) == TileId(1, 0, 1));
+        REQUIRE(tile.neighbor(0, 1) == TileId(0, 1, 1));
+        REQUIRE(tile.neighbor(-1, -1) == TileId(3, 0, 1));  // Wrap around
+
+        TileId tile2(3, 1, 1);
+        REQUIRE(tile2.neighbor(-1, -1) == TileId(2, 0, 1));
+        REQUIRE(tile2.neighbor(1, 1) == TileId(0, 1, 1));  // Wrap around
+
+        REQUIRE_THROWS(tile2.neighbor(2, -2));
+        REQUIRE_THROWS(tile2.neighbor(-2, 2));
+        REQUIRE_THROWS(tile2.neighbor(0, 3));
+        REQUIRE_THROWS(tile2.neighbor(0, -3));
+        REQUIRE_THROWS(tile2.neighbor(2, 0));
+        REQUIRE_THROWS(tile2.neighbor(-2, 0));
+    }
 }