2 files changed, 104 insertions, 2 deletions

diff --git a/spartan/client.go b/spartan/client.go
new file mode 100644
index 0000000..154b18a
--- /dev/null
+++ b/spartan/client.go
@@ -0,0 +1,70 @@
+package spartan
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"net"
+	"strconv"
+
+	"tildegit.org/tjp/gus"
+)
+
+// Client is used for sending spartan requests and receiving responses.
+//
+// It carries no state and is reusable simultaneously by multiple goroutines.
+//
+// The zero value is immediately usabble.
+type Client struct{}
+
+// RoundTrip sends a single spartan request and returns its response.
+func (c Client) RoundTrip(request *gus.Request, body io.Reader) (*gus.Response, error) {
+	if request.Scheme != "spartan" && request.Scheme != "" {
+		return nil, errors.New("non-spartan protocols not supported")
+	}
+
+	host, port, _ := net.SplitHostPort(request.Host)
+	if port == "" {
+		host = request.Host
+		port = "300"
+	}
+	addr := net.JoinHostPort(host, port)
+
+	conn, err := net.Dial("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+
+	request.RemoteAddr = conn.RemoteAddr()
+
+	var bodyBytes []byte = nil
+	if body != nil {
+		bodyBytes, err = io.ReadAll(body)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	requestLine := host + " " + request.EscapedPath() + " " + strconv.Itoa(len(bodyBytes)) + "\r\n"
+
+	if _, err := conn.Write([]byte(requestLine)); err != nil {
+		return nil, err
+	}
+	if _, err := conn.Write(bodyBytes); err != nil {
+		return nil, err
+	}
+
+	response, err := ParseResponse(conn)
+	if err != nil {
+		return nil, err
+	}
+
+	bodybuf, err := io.ReadAll(response.Body)
+	if err != nil {
+		return nil, err
+	}
+	response.Body = bytes.NewBuffer(bodybuf)
+
+	return response, nil
+}
diff --git a/spartan/response.go b/spartan/response.go
index edc1db6..bd906e0 100644
--- a/spartan/response.go
+++ b/spartan/response.go
@@ -1,8 +1,11 @@
 package spartan
 
 import (
+	"bufio"
 	"bytes"
+	"errors"
 	"io"
+	"strconv"
 	"sync"
 
 	"tildegit.org/tjp/gus"
@@ -37,7 +40,7 @@ func Redirect(url string) *gus.Response {
 func ClientError(err error) *gus.Response {
 	return &gus.Response{
 		Status: StatusClientError,
-		Meta: err.Error(),
+		Meta:   err.Error(),
 	}
 }
 
@@ -45,10 +48,39 @@ func ClientError(err error) *gus.Response {
 func ServerError(err error) *gus.Response {
 	return &gus.Response{
 		Status: StatusServerError,
-		Meta: err.Error(),
+		Meta:   err.Error(),
 	}
 }
 
+// InvalidResponseHeaderLine indicates a malformed spartan response line.
+var InvalidResponseHeaderLine = errors.New("Invalid response header line.")
+
+// InvalidResponseLineEnding indicates that a spartan response header didn't end with "\r\n".
+var InvalidResponseLineEnding = errors.New("Invalid response line ending.")
+
+func ParseResponse(rdr io.Reader) (*gus.Response, error) {
+	bufrdr := bufio.NewReader(rdr)
+
+	hdrLine, err := bufrdr.ReadString('\n')
+	if err != nil {
+		return nil, InvalidResponseLineEnding
+	}
+	if len(hdrLine) < 2 {
+		return nil, InvalidResponseHeaderLine
+	}
+
+	status, err := strconv.Atoi(string(hdrLine[0]))
+	if err != nil || hdrLine[1] != ' ' || hdrLine[len(hdrLine)-2:] != "\r\n" {
+		return nil, InvalidResponseHeaderLine
+	}
+
+	return &gus.Response{
+		Status: gus.Status(status),
+		Meta:   hdrLine[2 : len(hdrLine)-2],
+		Body:   bufrdr,
+	}, nil
+}
+
 // NewResponseReader builds a reader for a response.
 func NewResponseReader(response *gus.Response) gus.ResponseReader {
 	return &responseReader{