1 files changed, 112 insertions, 0 deletions
diff --git a/src/oauth/client.go b/src/oauth/client.go
new file mode 100644
index 0000000..684cb20
--- /dev/null
+++ b/src/oauth/client.go
@@ -0,0 +1,112 @@
+// The oauth package provides a Client that authenticates requests
+// automatically with OAuth1.
+//
+// [Cardmarket OAuth] and [RFC 5849] were used as reference.
+//
+// [Cardmarket OAuth]: https://apiv2.cardmarket.com/ws/documentation/API:Auth_OAuthHeader
+// [RFC 5849]: https://datatracker.ietf.org/doc/html/rfc5849#section-3.1
+package oauth
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"strings"
+)
+
+const (
+	headerAuthorization = "Authorization"
+	headerContentType   = "Content-Type"
+)
+
+type ConsumerToken struct {
+	Token  string
+	Secret string
+}
+
+type AccessToken struct {
+	Token  string
+	Secret string
+}
+
+type Tokens struct {
+	Consumer ConsumerToken
+	Access   AccessToken
+}
+
+type Client struct {
+	tokens Tokens
+}
+
+func NewClient(t Tokens) *Client {
+	return &Client{tokens: t}
+}
+
+func (c *Client) GetWithContext(
+	ctx context.Context,
+	url string,
+) (*http.Response, error) {
+	return c.request(ctx, http.MethodGet, url, "", nil)
+}
+
+func (c *Client) PostWithContext(
+	ctx context.Context,
+	url, contentType string,
+	body io.Reader,
+) (*http.Response, error) {
+	return c.request(ctx, http.MethodPost, url, contentType, body)
+}
+
+// request hydrates and fulfils a http.Request using information stored in the client
+func (c *Client) request(
+	ctx context.Context,
+	method string,
+	url, contentType string,
+	body io.Reader,
+) (*http.Response, error) {
+	req, err := http.NewRequestWithContext(ctx, method, url, body)
+	if err != nil {
+		return nil, err
+	}
+
+	if contentType != "" {
+		req.Header.Set("Content-Type", contentType)
+	}
+
+	if err = c.authorize(req); err != nil {
+		return nil, err
+	}
+
+	slog.DebugContext(
+		ctx,
+		"sending request",
+		"method", req.Method,
+		"url", req.URL.String(),
+		"contentType", req.Header.Get(headerContentType),
+		"authorization", strings.Join(req.Header.Values(headerAuthorization), ", "),
+	)
+
+	return http.DefaultClient.Do(req)
+}
+
+func (c *Client) authorize(req *http.Request) error {
+	baseURL := fmt.Sprintf(
+		"%s://%s%s",
+		strings.ToLower(req.URL.Scheme),
+		strings.ToLower(req.URL.Host),
+		req.URL.Path,
+	)
+
+	ah := newAuthHeader(
+		req.Method,
+		baseURL,
+		nil,
+		c.tokens,
+	)
+
+	req.Header.Set(headerAuthorization, ah.String())
+
+	return nil
+}