feat: add get_epoch_by_number RPC

lib/ckb/api.rb

@@ -139,6 +139,15 @@ def get_current_epoch
       Types::Epoch.from_h(rpc.get_current_epoch)
     end
 
+    # @param number [Integer | String]
+    #
+    # @return [CKB::Types::Epoch]
+    def get_epoch_by_number(number)
+      Types::Epoch.from_h(
+        rpc.get_epoch_by_number(number)
+      )
+    end
+
     def inspect
       "\#<API@#{uri}>"
     end

lib/ckb/rpc.rb

@@ -78,6 +78,10 @@ def get_current_epoch
       rpc_request("get_current_epoch")
     end
 
+    def get_epoch_by_number(number)
+      rpc_request("get_epoch_by_number", params: [number.to_s])
+    end
+
     def inspect
       "\#<RPC@#{uri}>"
     end

lib/ckb/types/epoch.rb

@@ -43,6 +43,7 @@ def to_h
       end
 
       def self.from_h(hash)
+        return if hash.nil?
         new(
           block_reward: hash[:block_reward],
           difficulty: hash[:difficulty],

spec/ckb/api_spec.rb

@@ -76,4 +76,11 @@
     expect(result).not_to be nil
     expect(result).to be_a(Types::Epoch)
   end
+
+  it "get epoch by number" do
+    number = 1
+    result = api.get_epoch_by_number(number)
+    expect(result).to be_a(Types::Epoch)
+    expect(result.number).to eq number.to_s
+  end
 end

spec/ckb/rpc_spec.rb

@@ -100,4 +100,11 @@
     result = rpc.get_transaction_trace(trace_tx_hash)
     expect(result).to be nil
   end
+
+  it "get epoch by number" do
+    number = '1'
+    result = rpc.get_epoch_by_number(number)
+    expect(result).to be_a(Hash)
+    expect(result[:number]).to eq number
+  end
 end