feat: add support for getRecentPrioritizationFees RPC method (#140)

* feat: add wrapper for getRecentPrioritizationFees rpc call

* test: getRecentPrioritizationFees rpc call

* docs: README entry for getRecentPrioritizationFees rpc method

* docs: update errors in README

* refactor: add comments to GetRecentPrioritizationFees

README.md

@@ -872,6 +872,7 @@ func main() {
     - To be used with **solana v1.8**
     - For solana v1.9 or newer: **DEPRECATED: Please use [GetLatestBlockhash](#index--rpc--getlatestblockhash) instead** (This method is expected to be removed in **solana-core v2.0**)
   - [GetRecentPerformanceSamples](#index--rpc--getrecentperformancesamples)
+  - [GetRecentPrioritizationFees](#index--rpc--getrecentprioritizationfees)
   - [GetSignatureStatuses](#index--rpc--getsignaturestatuses)
   - [GetSignaturesForAddress](#index--rpc--getsignaturesforaddress)
   - [GetSlot](#index--rpc--getslot)
@@ -2218,7 +2219,6 @@ func main() {
   spew.Dump(recent)
 }
 ```
-
 #### [index](#contents) > [RPC](#rpc-methods) > GetRecentPerformanceSamples
 
 ```go
@@ -2247,6 +2247,36 @@ func main() {
 }
 ```
 
+#### [index](#contents) > [RPC](#rpc-methods) > GetRecentPrioritizationFees
+
+```go
+package main
+
+import (
+  "context"
+
+  "github.com/davecgh/go-spew/spew"
+  "github.com/gagliardetto/solana-go"
+  "github.com/gagliardetto/solana-go/rpc"
+)
+
+func main() {
+  endpoint := rpc.TestNet_RPC
+  client := rpc.New(endpoint)
+
+  out, err := client.GetRecentPrioritizationFees(
+    context.TODO(),
+    []solana.PublicKey{
+      solana.MustPublicKeyFromBase58("q5BgreVhTyBH1QCeriVb7kQYEPneanFXPLjvyjdf8M3"),
+    },
+  )
+  if err != nil {
+    panic(err)
+  }
+  spew.Dump(out)
+}
+```
+
 #### [index](#contents) > [RPC](#rpc-methods) > GetSignatureStatuses
 
 ```go

rpc/client_test.go

@@ -2766,3 +2766,43 @@ func TestClient_GetLatestBlockhash(t *testing.T) {
 
 	assert.Equal(t, expected, got, "both deserialized values must be equal")
 }
+
+func TestClient_GetRecentPrioritizationFees(t *testing.T) {
+	responseBody := `[ { "slot": 348125, "prioritizationFee": 0 }, { "slot": 348126, "prioritizationFee": 1000 }, { "slot": 348127, "prioritizationFee": 500 } ]`
+	server, closer := mockJSONRPC(t, stdjson.RawMessage(wrapIntoRPC(responseBody)))
+	defer closer()
+
+	client := New(server.URL)
+
+	accounts := []solana.PublicKey{
+		solana.MustPublicKeyFromBase58("41twqNJmPHv8a5AW32if2CcGRcPzaetwErXaNggGWu1q"),
+		solana.MustPublicKeyFromBase58("5U3bH5b6XtG99aVWLqwVzYPVpQiFHytBD68Rz2eFPZd7"),
+	}
+
+	out, err := client.GetRecentPrioritizationFees(
+		context.Background(),
+		accounts,
+	)
+	require.NoError(t, err)
+
+	assert.Equal(t,
+		map[string]interface{}{
+			"id":      float64(0),
+			"jsonrpc": "2.0",
+			"method":  "getRecentPrioritizationFees",
+			"params": []interface{}{
+				[]interface{}{
+					accounts[0].String(),
+					accounts[1].String(),
+				},
+			},
+		},
+		server.RequestBody(t),
+	)
+
+	expected := mustJSONToInterface([]byte(responseBody))
+
+	got := mustJSONToInterface(mustAnyToJSON(out))
+
+	assert.Equal(t, expected, got, "both deserialized values must be equal")
+}

rpc/getRecentPrioritizationFees.go

@@ -0,0 +1,41 @@
+// Copyright 2021 github.com/gagliardetto
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rpc
+
+import (
+	"context"
+
+	"github.com/gagliardetto/solana-go"
+)
+
+// GetRecentPrioritizationFees returns a list of prioritization fees from recent blocks.
+// Currently, a node's prioritization-fee cache stores data from up to 150 blocks.
+func (cl *Client) GetRecentPrioritizationFees(
+	ctx context.Context,
+	accounts solana.PublicKeySlice, // optional
+) (out []PriorizationFeeResult, err error) {
+	params := []interface{}{accounts}
+	err = cl.rpcClient.CallForInto(ctx, &out, "getRecentPrioritizationFees", params)
+
+	return
+}
+
+type PriorizationFeeResult struct {
+	// Slot in which the fee was observed
+	Slot uint64 `json:"slot"`
+
+	// The per-compute-unit fee paid by at least one successfully landed transaction, specified in increments of 0.000001 lamports
+	PrioritizationFee uint64 `json:"prioritizationFee"`
+}