Fixed parsing of the rate limit error response

Same as mapbox/MapboxGeocoder.swift#91.

MapboxStatic/Snapshot.swift

@@ -525,23 +525,22 @@ open class Snapshot: NSObject {
     /**
      Returns an error that supplements the given underlying error with additional information from the an HTTP response’s body or headers.
      */
-    fileprivate static func descriptiveError(_ json: JSONDictionary, response: URLResponse?, underlyingError error: NSError?) -> NSError {
+    static func descriptiveError(_ json: JSONDictionary, response: URLResponse?, underlyingError error: NSError?) -> NSError {
         var userInfo = error?.userInfo ?? [:]
         if let response = response as? HTTPURLResponse {
             var failureReason: String? = nil
             var recoverySuggestion: String? = nil
             switch response.statusCode {
             case 429:
-                if let timeInterval = response.allHeaderFields["x-rate-limit-interval"] as? TimeInterval, let maximumCountOfRequests = response.allHeaderFields["x-rate-limit-limit"] as? UInt {
+                if let timeInterval = response.rateLimitInterval, let maximumCountOfRequests = response.rateLimit {
                     let intervalFormatter = DateComponentsFormatter()
                     intervalFormatter.unitsStyle = .full
-                    let formattedInterval = intervalFormatter.string(from: timeInterval)
-                    let formattedCount = NumberFormatter.localizedString(from: NSNumber(value: maximumCountOfRequests), number: .decimal)
+                    let formattedInterval = intervalFormatter.string(from: timeInterval) ?? "\(timeInterval) seconds"
+                    let formattedCount = NumberFormatter.localizedString(from: maximumCountOfRequests as NSNumber, number: .decimal)
                     failureReason = "More than \(formattedCount) requests have been made with this access token within a period of \(formattedInterval)."
                 }
-                if let rolloverTimestamp = response.allHeaderFields["x-rate-limit-reset"] as? Double {
-                    let date = Date(timeIntervalSince1970: rolloverTimestamp)
-                    let formattedDate = DateFormatter.localizedString(from: date, dateStyle: .long, timeStyle: .full)
+                if let rolloverTime = response.rateLimitResetTime {
+                    let formattedDate = DateFormatter.localizedString(from: rolloverTime, dateStyle: .long, timeStyle: .full)
                     recoverySuggestion = "Wait until \(formattedDate) before retrying."
                 }
             default:
@@ -550,7 +549,39 @@ open class Snapshot: NSObject {
             userInfo[NSLocalizedFailureReasonErrorKey] = failureReason ?? userInfo[NSLocalizedFailureReasonErrorKey] ?? HTTPURLResponse.localizedString(forStatusCode: error?.code ?? -1)
             userInfo[NSLocalizedRecoverySuggestionErrorKey] = recoverySuggestion ?? userInfo[NSLocalizedRecoverySuggestionErrorKey]
         }
-        userInfo[NSUnderlyingErrorKey] = error
+        if let error = error {
+            userInfo[NSUnderlyingErrorKey] = error
+        }
         return NSError(domain: error?.domain ?? MBStaticErrorDomain, code: error?.code ?? -1, userInfo: userInfo)
     }
 }
+
+extension HTTPURLResponse {
+    static let rateLimitIntervalHeaderKey = "X-Rate-Limit-Interval"
+    static let rateLimitLimitHeaderKey = "X-Rate-Limit-Limit"
+    static let rateLimitResetHeaderKey = "X-Rate-Limit-Reset"
+
+    var rateLimit: UInt? {
+        guard let limit = allHeaderFields[HTTPURLResponse.rateLimitLimitHeaderKey] as? String else {
+            return nil
+        }
+        return UInt(limit)
+    }
+
+    var rateLimitInterval: TimeInterval? {
+        guard let interval = allHeaderFields[HTTPURLResponse.rateLimitIntervalHeaderKey] as? String else {
+            return nil
+        }
+        return TimeInterval(interval)
+    }
+
+    var rateLimitResetTime: Date? {
+        guard let resetTime = allHeaderFields[HTTPURLResponse.rateLimitResetHeaderKey] as? String else {
+            return nil
+        }
+        guard let resetTimeNumber = Double(resetTime) else {
+            return nil
+        }
+        return Date(timeIntervalSince1970: resetTimeNumber)
+    }
+}

MapboxStaticTests/MapboxStaticTests.swift

@@ -2,7 +2,7 @@ import XCTest
 import OHHTTPStubs
 import CoreLocation
 import Foundation
-import MapboxStatic
+@testable import MapboxStatic
 
 #if os(OSX)
     typealias Color = NSColor
@@ -18,6 +18,9 @@ class MapboxStaticTests: XCTestCase {
     override func setUp() {
         super.setUp()
         OHHTTPStubs.removeAllStubs()
+
+        // Make sure tests run in all time zones
+        NSTimeZone.default = TimeZone(secondsFromGMT: 0)!
     }
 
     fileprivate func parseQueryString(_ request: URLRequest) -> Dictionary<String, String> {
@@ -475,4 +478,19 @@ class MapboxStaticTests: XCTestCase {
 
         waitForExpectations(timeout: 1, handler: nil)
     }
+
+    func testRateLimitErrorParsing() {
+        let json = ["message" : "Hit rate limit"]
+
+        let url = URL(string: "https://api.mapbox.com")!
+        let headerFields = ["X-Rate-Limit-Interval" : "60", "X-Rate-Limit-Limit" : "600", "X-Rate-Limit-Reset" : "1479460584"]
+        let response = HTTPURLResponse(url: url, statusCode: 429, httpVersion: nil, headerFields: headerFields)
+
+        let error: NSError? = nil
+
+        let resultError = Snapshot.descriptiveError(json, response: response, underlyingError: error)
+
+        XCTAssertEqual(resultError.localizedFailureReason, "More than 600 requests have been made with this access token within a period of 1 minute.")
+        XCTAssertEqual(resultError.localizedRecoverySuggestion, "Wait until November 18, 2016 at 9:16:24 AM GMT before retrying.")
+    }
 }