Support maxFacetHits when searching for facet values (#301)

This parameter is implemented at the `Query` class level, although it only applies to searches for facet values (not to regular searches).

Author: Clément Le Provost

Source/Query.swift

@@ -746,6 +746,20 @@ open class Query : AbstractQuery {
         set { self["responseFields"] = Query.buildJSONArray(newValue) }
     }
 
+    /// Maximum number of facet hits to return during a search for facet values.
+    ///
+    /// + Note: Does not apply to regular search queries.
+    ///
+    /// + Note: For performance reasons, the maximum allowed number of returned values is 100.
+    ///   Any value outside the range [1, 100] will be rejected.
+    ///
+    /// + SeeAlso: `Index.searchForFacetValues(...)`
+    ///
+    public var maxFacetHits: UInt? {
+        get { return Query.parseUInt(self["maxFacetHits"]) }
+        set { self["maxFacetHits"] = Query.buildUInt(newValue) }
+    }
+
     // MARK: - Initialization
 
     /// Construct a query with the specified full text query.
@@ -1011,4 +1025,10 @@ open class Query : AbstractQuery {
         get { return AbstractQuery.toNumber(self.facetingAfterDistinct) }
         set { self.facetingAfterDistinct = newValue?.boolValue }
     }
+
+    @objc(maxFacetHits)
+    public var z_objc_maxFacetHits: NSNumber? {
+        get { return AbstractQuery.toNumber(self.maxFacetHits) }
+        set { self.maxFacetHits = newValue?.uintValue }
+    }
 }

Tests/QueryTests.swift

@@ -696,4 +696,14 @@ class QueryTests: XCTestCase {
         let query2 = Query.parse(query1.build())
         XCTAssertEqual(query2.facetingAfterDistinct, true)
     }
+
+    func test_maxFacetHits() {
+        let query1 = Query()
+        XCTAssertNil(query1.maxFacetHits)
+        query1.maxFacetHits = 66
+        XCTAssertEqual(query1.maxFacetHits, 66)
+        XCTAssertEqual(query1["maxFacetHits"], "66")
+        let query2 = Query.parse(query1.build())
+        XCTAssertEqual(query2.maxFacetHits, query1.maxFacetHits)
+    }
 }