[Access] Add REST endpoint to get an accounts flow balance

engine/access/rest/models/account.go

@@ -66,3 +66,7 @@ func (a *AccountPublicKeys) Build(accountKeys []flow.AccountPublicKey) {
 
 	*a = keys
 }
+
+func (b *AccountBalance) Build(balance uint64) {
+	b.Balance = util.FromUint(balance)
+}

engine/access/rest/models/model_account_balance.go

@@ -0,0 +1,14 @@
+/*
+ * Access API
+ *
+ * No description provided (generated by Swagger Codegen https://github.com/swagger-api/swagger-codegen)
+ *
+ * API version: 1.0.0
+ * Generated by: Swagger Codegen (https://github.com/swagger-api/swagger-codegen.git)
+ */
+package models
+
+type AccountBalance struct {
+	// Flow balance of the account.
+	Balance string `json:"balance"`
+}

engine/access/rest/request/get_account_balance.go

@@ -0,0 +1,45 @@
+package request
+
+import (
+	"github.com/onflow/flow-go/model/flow"
+)
+
+type GetAccountBalance struct {
+	Address flow.Address
+	Height  uint64
+}
+
+func (g *GetAccountBalance) Build(r *Request) error {
+	return g.Parse(
+		r.GetVar(addressVar),
+		r.GetQueryParam(blockHeightQuery),
+		r.Chain,
+	)
+}
+
+func (g *GetAccountBalance) Parse(
+	rawAddress string,
+	rawHeight string,
+	chain flow.Chain,
+) error {
+	address, err := ParseAddress(rawAddress, chain)
+	if err != nil {
+		return err
+	}
+
+	var height Height
+	err = height.Parse(rawHeight)
+	if err != nil {
+		return err
+	}
+
+	g.Address = address
+	g.Height = height.Flow()
+
+	// default to last block
+	if g.Height == EmptyHeight {
+		g.Height = SealedHeight
+	}
+
+	return nil
+}

engine/access/rest/request/get_account_balance_test.go

@@ -0,0 +1,45 @@
+package request
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/onflow/flow-go/model/flow"
+)
+
+func Test_GetAccountBalance_InvalidParse(t *testing.T) {
+	var getAccountBalance GetAccountBalance
+
+	tests := []struct {
+		address string
+		height  string
+		err     string
+	}{
+		{"", "", "invalid address"},
+		{"f8d6e0586b0a20c7", "-1", "invalid height format"},
+	}
+
+	chain := flow.Localnet.Chain()
+	for i, test := range tests {
+		err := getAccountBalance.Parse(test.address, test.height, chain)
+		assert.EqualError(t, err, test.err, fmt.Sprintf("test #%d failed", i))
+	}
+}
+
+func Test_GetAccountBalance_ValidParse(t *testing.T) {
+
+	var getAccountBalance GetAccountBalance
+
+	addr := "f8d6e0586b0a20c7"
+	chain := flow.Localnet.Chain()
+	err := getAccountBalance.Parse(addr, "", chain)
+	assert.NoError(t, err)
+	assert.Equal(t, getAccountBalance.Address.String(), addr)
+	assert.Equal(t, getAccountBalance.Height, SealedHeight)
+
+	err = getAccountBalance.Parse(addr, "100", chain)
+	assert.NoError(t, err)
+	assert.Equal(t, getAccountBalance.Height, uint64(100))
+}

engine/access/rest/request/request.go

@@ -54,6 +54,12 @@ func (rd *Request) GetAccountRequest() (GetAccount, error) {
 	return req, err
 }
 
+func (rd *Request) GetAccountBalanceRequest() (GetAccountBalance, error) {
+	var req GetAccountBalance
+	err := req.Build(rd)
+	return req, err
+}
+
 func (rd *Request) GetAccountKeyRequest() (GetAccountKey, error) {
 	var req GetAccountKey
 	err := req.Build(rd)

engine/access/rest/routes/account_balance.go

@@ -0,0 +1,39 @@
+package routes
+
+import (
+	"fmt"
+
+	"github.com/onflow/flow-go/access"
+	"github.com/onflow/flow-go/engine/access/rest/models"
+	"github.com/onflow/flow-go/engine/access/rest/request"
+)
+
+// GetAccountBalance handler retrieves an account balance by address and block height and returns the response
+func GetAccountBalance(r *request.Request, backend access.API, _ models.LinkGenerator) (interface{}, error) {
+	req, err := r.GetAccountBalanceRequest()
+	if err != nil {
+		return nil, models.NewBadRequestError(err)
+	}
+
+	// In case we receive special height values 'final' and 'sealed',
+	// fetch that height and overwrite request with it.
+	if req.Height == request.FinalHeight || req.Height == request.SealedHeight {
+		isSealed := req.Height == request.SealedHeight
+		header, _, err := backend.GetLatestBlockHeader(r.Context(), isSealed)
+		if err != nil {
+			err := fmt.Errorf("block with height: %d does not exist", req.Height)
+			return nil, models.NewNotFoundError(err.Error(), err)
+		}
+		req.Height = header.Height
+	}
+
+	balance, err := backend.GetAccountBalanceAtBlockHeight(r.Context(), req.Address, req.Height)
+	if err != nil {
+		err = fmt.Errorf("failed to get account balance, reason: %w", err)
+		return nil, models.NewNotFoundError(err.Error(), err)
+	}
+
+	var response models.AccountBalance
+	response.Build(balance)
+	return response, nil
+}

engine/access/rest/routes/account_balance_test.go

@@ -0,0 +1,135 @@
+package routes
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	mocktestify "github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+
+	"github.com/onflow/flow-go/access/mock"
+	"github.com/onflow/flow-go/model/flow"
+	"github.com/onflow/flow-go/utils/unittest"
+)
+
+// TestGetAccountBalance tests local getAccountBalance request.
+//
+// Runs the following tests:
+// 1. Get account balance by address at latest sealed block.
+// 2. Get account balance by address at latest finalized block.
+// 3. Get account balance by address at height.
+// 4. Get invalid account balance.
+func TestGetAccountBalance(t *testing.T) {
+	backend := &mock.API{}
+
+	t.Run("get balance by address at latest sealed block", func(t *testing.T) {
+		account := accountFixture(t)
+		var height uint64 = 100
+		block := unittest.BlockHeaderFixture(unittest.WithHeaderHeight(height))
+
+		req := getAccountBalanceRequest(t, account, sealedHeightQueryParam)
+
+		backend.Mock.
+			On("GetLatestBlockHeader", mocktestify.Anything, true).
+			Return(block, flow.BlockStatusSealed, nil)
+
+		backend.Mock.
+			On("GetAccountBalanceAtBlockHeight", mocktestify.Anything, account.Address, height).
+			Return(account.Balance, nil)
+
+		expected := expectedAccountBalanceResponse(account)
+
+		assertOKResponse(t, req, expected, backend)
+		mocktestify.AssertExpectationsForObjects(t, backend)
+	})
+
+	t.Run("get balance by address at latest finalized block", func(t *testing.T) {
+		account := accountFixture(t)
+		var height uint64 = 100
+		block := unittest.BlockHeaderFixture(unittest.WithHeaderHeight(height))
+
+		req := getAccountBalanceRequest(t, account, finalHeightQueryParam)
+
+		backend.Mock.
+			On("GetLatestBlockHeader", mocktestify.Anything, false).
+			Return(block, flow.BlockStatusFinalized, nil)
+
+		backend.Mock.
+			On("GetAccountBalanceAtBlockHeight", mocktestify.Anything, account.Address, height).
+			Return(account.Balance, nil)
+
+		expected := expectedAccountBalanceResponse(account)
+
+		assertOKResponse(t, req, expected, backend)
+		mocktestify.AssertExpectationsForObjects(t, backend)
+	})
+
+	t.Run("get balance by address at height", func(t *testing.T) {
+		account := accountFixture(t)
+		var height uint64 = 1337
+		req := getAccountBalanceRequest(t, account, fmt.Sprintf("%d", height))
+
+		backend.Mock.
+			On("GetAccountBalanceAtBlockHeight", mocktestify.Anything, account.Address, height).
+			Return(account.Balance, nil)
+
+		expected := expectedAccountBalanceResponse(account)
+
+		assertOKResponse(t, req, expected, backend)
+		mocktestify.AssertExpectationsForObjects(t, backend)
+	})
+
+	t.Run("get invalid", func(t *testing.T) {
+		tests := []struct {
+			url string
+			out string
+		}{
+			{accountBalanceURL(t, "123", ""), `{"code":400, "message":"invalid address"}`},
+			{accountBalanceURL(t, unittest.AddressFixture().String(), "foo"), `{"code":400, "message":"invalid height format"}`},
+		}
+
+		for i, test := range tests {
+			req, _ := http.NewRequest("GET", test.url, nil)
+			rr := executeRequest(req, backend)
+
+			assert.Equal(t, http.StatusBadRequest, rr.Code)
+			assert.JSONEq(t, test.out, rr.Body.String(), fmt.Sprintf("test #%d failed: %v", i, test))
+		}
+	})
+}
+
+func accountBalanceURL(t *testing.T, address string, height string) string {
+	u, err := url.ParseRequestURI(fmt.Sprintf("/v1/accounts/%s/balance", address))
+	require.NoError(t, err)
+	q := u.Query()
+
+	if height != "" {
+		q.Add("block_height", height)
+	}
+
+	u.RawQuery = q.Encode()
+	return u.String()
+}
+
+func getAccountBalanceRequest(t *testing.T, account *flow.Account, height string) *http.Request {
+	req, err := http.NewRequest(
+		"GET",
+		accountBalanceURL(t, account.Address.String(), height),
+		nil,
+	)
+
+	require.NoError(t, err)
+	return req
+}
+
+func expectedAccountBalanceResponse(account *flow.Account) string {
+	return fmt.Sprintf(`
+        {
+          "balance":"%d"
+        }`,
+		account.Balance,
+	)
+}

engine/access/rest/routes/account_keys_test.go

@@ -13,7 +13,6 @@ import (
 
 	"github.com/onflow/flow-go/access/mock"
 	"github.com/onflow/flow-go/model/flow"
-
 	"github.com/onflow/flow-go/utils/unittest"
 )
 

engine/access/rest/routes/router.go

@@ -151,6 +151,11 @@ var Routes = []route{{
 	Pattern: "/accounts/{address}",
 	Name:    "getAccount",
 	Handler: GetAccount,
+}, {
+	Method:  http.MethodGet,
+	Pattern: "/accounts/{address}/balance",
+	Name:    "getAccountBalance",
+	Handler: GetAccountBalance,
 }, {
 	Method:  http.MethodGet,
 	Pattern: "/accounts/{address}/keys/{index}",