Implement `BundleCheckpointSource` and add Tests

Sources/ZcashLightClientKit/Checkpoint/BundleCheckpointSource.swift

@@ -0,0 +1,38 @@
+//
+//  BundleCheckpointSource.swift
+//
+//
+//  Created by Francisco Gindre on 10/30/23.
+//
+
+import Foundation
+
+struct BundleCheckpointSource: CheckpointSource {
+    var network: NetworkType
+    
+    var saplingActivation: Checkpoint
+    
+    init(network: NetworkType) {
+        self.network = network
+        self.saplingActivation = switch network {
+        case .mainnet:
+            Checkpoint.mainnetMin
+        case .testnet:
+            Checkpoint.testnetMin
+        }
+    }
+
+    func latestKnownCheckpoint() -> Checkpoint {
+        Checkpoint.birthday(
+            with: .max,
+            checkpointDirectory: BundleCheckpointURLProvider.default.url(self.network)
+        ) ?? saplingActivation
+    }
+    
+    func birthday(for height: BlockHeight) -> Checkpoint {
+        Checkpoint.birthday(
+            with: height, 
+            checkpointDirectory: BundleCheckpointURLProvider.default.url(self.network)
+        ) ?? saplingActivation
+    }
+}

Sources/ZcashLightClientKit/Checkpoint/CheckpointSource.swift

@@ -10,14 +10,14 @@ import Foundation
 /// A protocol that abstracts the requirements around obtaining wallet checkpoints
 /// (also known as TreeStates).
 protocol CheckpointSource {
-    /// network type of this Checkpoint source
+    /// `NetworkType` of this Checkpoint source
     var network: NetworkType { get }
 
     /// The `Checkpoint` that represents the block in which Sapling was activated
     var saplingActivation: Checkpoint { get }
 
     /// Obtain the latest `Checkpoint` in terms of block height known by
-    /// this `CheckpointSource`. It is possible that the returned checkpoints
+    /// this `CheckpointSource`. It is possible that the returned checkpoint
     /// is not the latest checkpoint that exists in the blockchain.
     /// - Returns a `Checkpoint` with the highest height known by this source
     func latestKnownCheckpoint() -> Checkpoint

Sources/ZcashLightClientKit/Checkpoint/CheckpointSourceFactory.swift

@@ -9,55 +9,6 @@ import Foundation
 
 struct CheckpointSourceFactory {
     static func fromBundle(for network: NetworkType) -> CheckpointSource {
-        Placeholder()
+        BundleCheckpointSource(network: network)
     }
 }
-
-// TODO: Remove this
-
-struct Placeholder: CheckpointSource {
-    var network: NetworkType { .mainnet }
-
-    var saplingActivation: Checkpoint {
-        Checkpoint(
-            height: 1,
-            hash: "deadbeef",
-            time: 1,
-            saplingTree: """
-            000000
-            """,
-            orchardTree: """
-            000000
-            """
-        )
-    }
-
-    func latestKnownCheckpoint() -> ZcashLightClientKit.Checkpoint {
-        Checkpoint(
-            height: 1,
-            hash: "deadbeef",
-            time: 1,
-            saplingTree: """
-            000000
-            """,
-            orchardTree: """
-            000000
-            """
-        )
-    }
-
-    func birthday(for height: BlockHeight) -> Checkpoint {
-        Checkpoint(
-            height: 1,
-            hash: "deadbeef",
-            time: 1,
-            saplingTree: """
-            000000
-            """,
-            orchardTree: """
-            000000
-            """
-        )
-    }
-}
-

Tests/OfflineTests/CheckpointSourceTests.swift

@@ -93,7 +93,7 @@ class CheckpointSourceTests: XCTestCase {
 
         let source = CheckpointSourceFactory.fromBundle(for: .mainnet)
 
-        let birthday = source.birthday(for: 4)
+        let birthday = source.birthday(for: activationHeight)
 
         XCTAssertEqual(birthday.height, activationHeight)
         XCTAssertEqual(birthday.orchardTree, "000000")