Merge pull request #6 from michael-groble/add-geohash-iterator

add geohash iterator

Sources/Geohash/GeohashIterator.swift

@@ -0,0 +1,39 @@
+//
+//  GeohashIterator.swift
+//  Geohash
+//
+//  Created by michael groble on 1/12/17.
+//
+//
+
+public class GeohashIterator : IteratorProtocol, Sequence {
+
+  let bounds: BoundingBox
+  var latBaseline: GeohashBits
+  var current: GeohashBits?
+
+  public init(bounds: BoundingBox, bitPrecision: UInt8) throws {
+    self.bounds = bounds
+    self.latBaseline = try GeohashBits(location: bounds.min, bitPrecision: bitPrecision)
+    self.current = self.latBaseline
+  }
+
+  public func next() -> GeohashBits? {
+    defer { advanceCurrent() }
+    return current
+  }
+
+  private func advanceCurrent() {
+    // advance eastward until we are out of the bounds then advance northward
+    if var bits = self.current {
+      bits = bits.neighbor(.east)
+      if bounds.intersects(bits.boundingBox()) {
+        self.current = bits
+      }
+      else {
+        self.latBaseline = latBaseline.neighbor(.north)
+        self.current = bounds.intersects(latBaseline.boundingBox()) ? latBaseline : nil
+      }
+    }
+  }
+}

Tests/GeohashTests/GeohashIteratorTests.swift

@@ -0,0 +1,40 @@
+//
+//  GeohashIteratorTests.swift
+//  Geohash
+//
+//  Created by michael groble on 1/12/17.
+//
+//
+
+import XCTest
+@testable import Geohash
+
+class GeohashIteratorTests: XCTestCase {
+
+  var bounds: BoundingBox!
+
+  override func setUp() {
+    super.setUp()
+
+    self.bounds = try! BoundingBox(
+      min: Location(longitude: 0.09991, latitude: 51.49996),
+      max: Location(longitude: 0.10059, latitude: 51.50028)
+    )
+  }
+
+
+  func testIterateLevel8() throws {
+    let subject = try GeohashIterator(bounds: bounds, bitPrecision: 20)
+    XCTAssertEqual(subject.next()!.hash(), "u10hfr2c")
+    XCTAssertEqual(subject.next()!.hash(), "u10hfr31")
+    XCTAssertEqual(subject.next()!.hash(), "u10hfr2f")
+    XCTAssertEqual(subject.next()!.hash(), "u10hfr34")
+    XCTAssertNil(subject.next())
+  }
+}
+
+extension GeohashIteratorTests {
+  static var allTests = [
+    ("testIterateLevel8", testIterateLevel8),
+    ]
+}

Tests/LinuxMain.swift

@@ -4,5 +4,6 @@ import XCTest
 XCTMain([
   testCase(BoundingBoxTests.allTests),
   testCase(GeohashBitsTests.allTests),
+  testCase(GeohashIteratorTests.allTests),
   testCase(LocationTests.allTests),
 ])