Merge pull request #4 from michael-groble/bbox-intersection

add bounding box intersection test

Sources/Geohash/BoundingBox.swift

@@ -7,10 +7,16 @@
 //
 
 public class BoundingBox {
-  let min: Location
-  let max: Location
+  public let min: Location
+  public let max: Location
+
+  public init(min: Location, max: Location) throws {
+    guard
+      min.longitude <= max.longitude &&
+      min.latitude  <= max.latitude else {
+        throw GeohashError.invalidArguments
+    }
 
-  public init(min: Location, max: Location) {
     self.min = min
     self.max = max
   }
@@ -21,4 +27,16 @@ public class BoundingBox {
       latitude:  0.5 * (self.min.latitude + self.max.latitude)
     )
   }
+
+  /// - todo: support wrap-around at the 180th meridian
+  public func intersects(_ other: BoundingBox) -> Bool {
+    if
+      max.longitude < other.min.longitude ||
+      max.latitude  < other.min.latitude  ||
+      min.longitude > other.max.longitude ||
+      min.latitude  > other.max.latitude {
+      return false
+    }
+    return true
+  }
 }

Sources/Geohash/Geohash.swift

@@ -0,0 +1,13 @@
+//
+//  Geohash.swift
+//  Geohash
+//
+//  Created by michael groble on 1/8/17.
+//
+//
+
+public enum GeohashError : Error {
+  case invalidPrecision
+  case invalidLocation
+  case invalidArguments
+}

Sources/Geohash/GeohashBits.swift

@@ -8,11 +8,6 @@
 
 import Foundation
 
-public enum GeohashError : Error {
-  case invalidPrecision
-  case invalidLocation
-}
-
 public struct GeohashBits {
   public let bits : UInt64
   public let precision : UInt8
@@ -89,7 +84,7 @@ public struct GeohashBits {
       latPrecision -= 1;
     }
 
-    return BoundingBox(
+    return try! BoundingBox(
       min: Location(longitude: unscaledBits(lonBits, range: longitudeRange, precision: self.precision),
                     latitude:  unscaledBits(latBits, range: latitudeRange,  precision: latPrecision)),
       max: Location(longitude: unscaledBits(lonBits + 1, range: longitudeRange, precision: self.precision),

Tests/GeohashTests/BoundingBoxTests.swift

@@ -0,0 +1,47 @@
+//
+//  BoundingBoxTests.swift
+//  Geohash
+//
+//  Created by michael groble on 1/8/17.
+//
+//
+
+import XCTest
+@testable import Geohash
+
+class BoundingBoxTests: XCTestCase {
+
+  var subject: BoundingBox!
+
+  override func setUp() {
+    super.setUp()
+
+    self.subject = try! BoundingBox(
+      min: Location(longitude: -10, latitude: -10),
+      max: Location(longitude: +10, latitude: +10)
+    )
+  }
+
+  func testIntersectsIntersecting() throws {
+    let intersecting = try BoundingBox(
+      min: Location(longitude: -20, latitude: -20),
+      max: Location(longitude:  -9, latitude: -9)
+    )
+    XCTAssertTrue(subject.intersects(intersecting))
+  }
+
+  func testIntersectsNonIntersecting() throws {
+    let intersecting = try BoundingBox(
+      min: Location(longitude: -20, latitude: -20),
+      max: Location(longitude:  -9, latitude: -10.1)
+    )
+    XCTAssertFalse(subject.intersects(intersecting))
+  }
+}
+
+extension BoundingBoxTests {
+  static var allTests = [
+    ("testIntersectsIntersecting", testIntersectsIntersecting),
+    ("testIntersectsNonIntersecting", testIntersectsNonIntersecting),
+  ]
+}

Tests/LinuxMain.swift

@@ -2,6 +2,7 @@ import XCTest
 @testable import GeohashTests
 
 XCTMain([
+  testCase(BoundingBoxTests.allTests),
   testCase(GeohashBitsTests.allTests),
   testCase(LocationTests.allTests),
 ])