SWIFT-630 Integrate the BSON enum into the public API

Sources/MongoSwift/BSON/BSON.swift

@@ -74,14 +74,14 @@ public enum BSON {
     /// Initialize a `BSON` from an integer. On 64-bit systems, this will result in an `.int64`. On 32-bit systems,
     /// this will result in an `.int32`.
     public init(_ int: Int) {
-        if Int.bsonType == .int32 {
+        if MemoryLayout<Int>.size == 4 {
             self = .int32(Int32(int))
         } else {
             self = .int64(Int64(int))
         }
     }
 
-    /// Gets the `BSONType` of this `BSON`.
+    /// Get the `BSONType` of this `BSON`.
     public var type: BSONType {
         return self.bsonValue.bsonType
     }
@@ -403,8 +403,7 @@ extension BSON: ExpressibleByIntegerLiteral {
 
 extension BSON: ExpressibleByDictionaryLiteral {
     public init(dictionaryLiteral elements: (String, BSON)...) {
-        // TODO SWIFT-630: Implement this.
-        self = .document(Document())
+        self = .document(Document(keyValuePairs: elements))
     }
 }
 
@@ -418,4 +417,31 @@ extension BSON: Equatable {}
 
 extension BSON: Hashable {}
 
-// TODO SWIFT-629: Implement Codable conformance
+extension BSON: Codable {
+    public init(from decoder: Decoder) throws {
+        if let bsonDecoder = decoder as? _BSONDecoder {
+            // This path only taken if a BSON is directly decoded at the top-level. Otherwise execution will never reach
+            // this point.
+            self = try bsonDecoder.decodeBSON()
+        } else {
+            // This path is taken no matter what when a non-BSONDecoder is used.
+            for bsonType in BSON.allBSONTypes {
+                if let value = try? bsonType.init(from: decoder) {
+                    self = value.bson
+                }
+            }
+
+            throw DecodingError.typeMismatch(
+                    BSON.self,
+                    DecodingError.Context(
+                            codingPath: decoder.codingPath,
+                            debugDescription: "Encountered a value that could not be decoded to any BSON type")
+            )
+        }
+    }
+
+    public func encode(to encoder: Encoder) throws {
+        // This is only reached when a non-BSON encoder is used.
+        try self.bsonValue.encode(to: encoder)
+    }
+}