abstract providers behind a common interface

bitcoin/address.go

@@ -25,13 +25,12 @@ type Address struct {
 
 // GetAddress returns an Address struct populated with data from blockstream.info
 // for a given BTC address
-func (c *Client) GetAddress(address string) (*Address, error) {
+func (c *client) GetAddress(address string) (*Address, error) {
 	addressResponse := &Address{}
 
 	err := c.get(fmt.Sprintf("address/%s", address), addressResponse, url.Values{})
 	if err != nil {
 		return nil, err
 	}
-
 	return addressResponse, nil
 }

bitcoin/client.go

@@ -14,13 +14,13 @@ const apiBaseURL = "https://blockstream.info/api/"
 // A client is the structure that will be used to consume the API
 // endpoints. It holds the login credentials, http client/transport,
 // rate limit information, and the login session timer.
-type Client struct {
+type client struct {
 	httpClient *http.Client
 	transport  *http.Transport
 }
 
 // Send an HTTP GET request, and return the processed response
-func (c *Client) get(endpoint string, out interface{}, query url.Values) error {
+func (c *client) get(endpoint string, out interface{}, query url.Values) error {
 	req, err := http.NewRequest("GET", apiBaseURL+endpoint+"?"+query.Encode(), nil)
 	if err != nil {
 		return fmt.Errorf("failed to create new GET request: %v", err)
@@ -42,7 +42,7 @@ func (c *Client) get(endpoint string, out interface{}, query url.Values) error {
 // the error code, or unmarshalls the JSON response, extracts
 // rate limit info, and places it into the object
 // output parameter. This function closes the response body after reading it.
-func (c *Client) processResponse(res *http.Response, out interface{}) error {
+func (c *client) processResponse(res *http.Response, out interface{}) error {
 	body, err := io.ReadAll(res.Body)
 	res.Body.Close()
 	if err != nil {
@@ -57,25 +57,23 @@ func (c *Client) processResponse(res *http.Response, out interface{}) error {
 	if err != nil {
 		return fmt.Errorf("failed to unmarshal response body: %v", err)
 	}
-
 	return nil
 }
 
-// NewClient is the factory function for clients
-func NewClient() (*Client, error) {
+// newClient is the factory function for clients
+func newClient() (*client, error) {
 	transport := &http.Transport{
 		ResponseHeaderTimeout: 5 * time.Second,
 	}
 
-	client := &http.Client{
+	httpClient := &http.Client{
 		Transport: transport,
 	}
 
 	// Create a new client
-	c := &Client{
-		httpClient: client,
+	c := &client{
+		httpClient: httpClient,
 		transport:  transport,
 	}
-
 	return c, nil
 }

bitcoin/fiat.go

@@ -16,8 +16,7 @@ type FiatConversion struct {
 
 // BTC to CAD FIAT conversion - accepts an
 // amount in satoshi's and returns a CAD amount * 1000
-func (c *Client) ConvertBTCToCAD(amount int) (int, error) {
-
+func (c *client) ConvertBTCToCAD(amount int) (int, error) {
 	fiatConversion := &FiatConversion{}
 
 	req, err := http.NewRequest("GET", fiatConvertURL+"?amount=1", nil)
@@ -38,6 +37,5 @@ func (c *Client) ConvertBTCToCAD(amount int) (int, error) {
 	if fiatConversion.Status != "success" {
 		return 0, fmt.Errorf("fiat conversion status was '%s' but expected 'success'", fiatConversion.Status)
 	}
-
 	return (amount * int(fiatConversion.CAD*1000)) / 100000000, nil // one BTC = one hundred million satoshi's
 }

bitcoin/providerImpl.go

@@ -0,0 +1,70 @@
+package bitcoin
+
+import (
+	"fmt"
+	"os"
+)
+
+type Provider struct {
+	bitcoinAddresses []string // Slice of bitcoin addresses this provider monitors
+	ynabAccountID    string   // YNAB account ID this provider updates - all bitcoin addresses are summed up and mapped to this YNAB account
+	client           *client  // HTTP client for interacting with Questrade API
+}
+
+func (p *Provider) Name() string {
+	return "Bitcoin - Blockstream.info"
+}
+
+// Configures the provider for usage via environment variables and persistentData
+// If an error is returned, the provider will not be used
+func (p *Provider) Configure() error {
+	var err error
+
+	// Load environment variables in continous series with suffix starting at 0
+	// Multiple addresses can be configured, (eg _1, _2)
+	// As soon as the series is interrupted, we assume we're done
+	p.bitcoinAddresses = make([]string, 0)
+	for i := 0; true; i++ {
+		bitcoinAddress := os.Getenv(fmt.Sprintf("bitcoin_address_%d", i))
+		if bitcoinAddress == "" {
+			if i == 0 {
+				return fmt.Errorf("this account provider is not configured")
+			}
+			break
+		}
+		p.bitcoinAddresses = append(p.bitcoinAddresses, bitcoinAddress)
+	}
+	p.ynabAccountID = os.Getenv("bitcoin_ynab_account")
+
+	// Create new HTTP client
+	p.client, err = newClient()
+	if err != nil {
+		return fmt.Errorf("failed to create new bitcoin client: %v", err)
+	}
+	return nil
+}
+
+// Returns slices of account balances and mapped YNAB account IDs, along with an error
+func (p *Provider) GetBalances() ([]int, []string, error) {
+
+	balances := make([]int, 0)
+	ynabAccountIDs := make([]string, 0)
+	var satoshiBalance int
+	for _, bitcoinAddress := range p.bitcoinAddresses {
+		addressResponse, err := p.client.GetAddress(bitcoinAddress)
+		if err != nil {
+			return balances, ynabAccountIDs, fmt.Errorf("failed to get bitcoin address '%s': %v", bitcoinAddress, err)
+		}
+
+		satoshiBalance += addressResponse.ChainStats.FundedTxoSum - addressResponse.ChainStats.SpentTxoSum
+	}
+
+	fiatBalance, err := p.client.ConvertBTCToCAD(satoshiBalance)
+	if err != nil {
+		return balances, ynabAccountIDs, fmt.Errorf("failed to convert satoshi balance to fiat balance: %v", err)
+	}
+
+	balances = append(balances, fiatBalance)
+	ynabAccountIDs = append(ynabAccountIDs, p.ynabAccountID)
+	return balances, ynabAccountIDs, nil
+}