3 files changed, 253 insertions, 0 deletions
diff --git a/spartan/request.go b/spartan/request.go
new file mode 100644
index 0000000..331b68c
--- /dev/null
+++ b/spartan/request.go
@@ -0,0 +1,62 @@
+package spartan
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"tildegit.org/tjp/gus"
+)
+
+var (
+	// InvalidRequestLine indicates a malformed first-line of a spartan request.
+	InvalidRequestLine = errors.New("invalid request line")
+
+	// InvalidRequestLineEnding says that a spartan request's first line wasn't terminated with CRLF.
+	InvalidRequestLineEnding = errors.New("invalid request line ending")
+)
+
+// ParseRequest parses a single spartan request and the indicated content-length from a reader.
+//
+// If ther reader artument is a *bufio.Reader, it will only read a single line from it.
+func ParseRequest(rdr io.Reader) (*gus.Request, int, error) {
+	bufrdr, ok := rdr.(*bufio.Reader)
+	if !ok {
+		bufrdr = bufio.NewReader(rdr)
+	}
+
+	line, err := bufrdr.ReadString('\n')
+	if err != io.EOF && err != nil {
+		return nil, 0, err
+	}
+
+	host, rest, ok := strings.Cut(line, " ")
+	if !ok {
+		return nil, 0, InvalidRequestLine
+	}
+	path, rest, ok := strings.Cut(line, " ")
+	if !ok {
+		return nil, 0, InvalidRequestLine
+	}
+
+	if len(rest) < 2 || line[len(line)-2:] != "\r\n" {
+		return nil, 0, InvalidRequestLineEnding
+	}
+
+	contentlen, err := strconv.Atoi(line[:len(line)-2])
+	if err != nil {
+		return nil, 0, err
+	}
+
+	return &gus.Request{
+		URL: &url.URL{
+			Scheme:  "spartan",
+			Host:    host,
+			Path:    path,
+			RawPath: path,
+		},
+	}, contentlen, nil
+}
diff --git a/spartan/response.go b/spartan/response.go
new file mode 100644
index 0000000..edc1db6
--- /dev/null
+++ b/spartan/response.go
@@ -0,0 +1,96 @@
+package spartan
+
+import (
+	"bytes"
+	"io"
+	"sync"
+
+	"tildegit.org/tjp/gus"
+)
+
+// The spartan response types.
+const (
+	StatusSuccess     gus.Status = 2
+	StatusRedirect    gus.Status = 3
+	StatusClientError gus.Status = 4
+	StatusServerError gus.Status = 5
+)
+
+// Success builds a successful spartan response.
+func Success(mediatype string, body io.Reader) *gus.Response {
+	return &gus.Response{
+		Status: StatusSuccess,
+		Meta:   mediatype,
+		Body:   body,
+	}
+}
+
+// Redirect builds a spartan redirect response.
+func Redirect(url string) *gus.Response {
+	return &gus.Response{
+		Status: StatusRedirect,
+		Meta:   url,
+	}
+}
+
+// ClientError builds a "client error" spartan response.
+func ClientError(err error) *gus.Response {
+	return &gus.Response{
+		Status: StatusClientError,
+		Meta: err.Error(),
+	}
+}
+
+// ServerError builds a "server error" spartan response.
+func ServerError(err error) *gus.Response {
+	return &gus.Response{
+		Status: StatusServerError,
+		Meta: err.Error(),
+	}
+}
+
+// NewResponseReader builds a reader for a response.
+func NewResponseReader(response *gus.Response) gus.ResponseReader {
+	return &responseReader{
+		Response: response,
+		once:     &sync.Once{},
+	}
+}
+
+type responseReader struct {
+	*gus.Response
+	reader io.Reader
+	once   *sync.Once
+}
+
+func (rdr *responseReader) Read(b []byte) (int, error) {
+	rdr.ensureReader()
+	return rdr.reader.Read(b)
+}
+
+func (rdr *responseReader) WriteTo(dst io.Writer) (int64, error) {
+	rdr.ensureReader()
+	return rdr.reader.(io.WriterTo).WriteTo(dst)
+}
+
+func (rdr *responseReader) ensureReader() {
+	rdr.once.Do(func() {
+		hdr := bytes.NewBuffer(rdr.headerLine())
+		if rdr.Body != nil {
+			rdr.reader = io.MultiReader(hdr, rdr.Body)
+		} else {
+			rdr.reader = hdr
+		}
+	})
+}
+
+func (rdr *responseReader) headerLine() []byte {
+	meta := rdr.Meta.(string)
+	buf := make([]byte, len(meta)+4)
+	buf[0] = byte(rdr.Status) + '0'
+	buf[1] = ' '
+	copy(buf[2:], meta)
+	buf[len(buf)-2] = '\r'
+	buf[len(buf)-1] = '\n'
+	return buf
+}
diff --git a/spartan/serve.go b/spartan/serve.go
new file mode 100644
index 0000000..677d76c
--- /dev/null
+++ b/spartan/serve.go
@@ -0,0 +1,95 @@
+package spartan
+
+import (
+	"bufio"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strings"
+
+	"tildegit.org/tjp/gus"
+	"tildegit.org/tjp/gus/internal"
+	"tildegit.org/tjp/gus/logging"
+)
+
+type spartanRequestBodyKey struct{}
+type spartanRequestBodyLenKey struct{}
+
+// SpartanRequestBody is the key set in a handler's context for spartan request bodies.
+//
+// The corresponding value is a *bufio.Reader from which the request body can be read.
+var SpartanRequestBody = spartanRequestBodyKey{}
+
+// SpartanRequestBodyLen is the key set in a handler's context for the content-length of the request.
+//
+// The corresponding value is an int.
+var SpartanRequestBodyLen = spartanRequestBodyLenKey{}
+
+type spartanServer struct {
+	internal.Server
+	handler gus.Handler
+}
+
+func (ss spartanServer) Protocol() string { return "SPARTAN" }
+
+// NewServer builds a spartan server.
+func NewServer(
+	ctx context.Context,
+	hostname string,
+	network string,
+	address string,
+	handler gus.Handler,
+	errLog logging.Logger,
+) (gus.Server, error) {
+	ss := &spartanServer{handler: handler}
+
+	if strings.IndexByte(hostname, ':') < 0 {
+		hostname = net.JoinHostPort(hostname, "300")
+	}
+
+	var err error
+	ss.Server, err = internal.NewServer(ctx, hostname, network, address, errLog, ss.handleConn)
+	if err != nil {
+		return nil, err
+	}
+
+	return ss, nil
+}
+
+func (ss *spartanServer) handleConn(conn net.Conn) {
+	buf := bufio.NewReader(conn)
+
+	var response *gus.Response
+	request, clen, err := ParseRequest(buf)
+	if err != nil {
+		response = ClientError(err)
+	} else {
+		request.Server = ss
+		request.RemoteAddr = conn.RemoteAddr()
+
+		var body *bufio.Reader = nil
+		if clen > 0 {
+			body = bufio.NewReader(io.LimitReader(buf, int64(clen)))
+		}
+		ctx := context.WithValue(ss.Ctx, SpartanRequestBody, body)
+		ctx = context.WithValue(ctx, SpartanRequestBodyLen, clen)
+
+		defer func() {
+			if r := recover(); r != nil {
+				err := fmt.Errorf("%s", r)
+				_ = ss.LogError("msg", "panic in handler", "err", err)
+				rdr := NewResponseReader(ServerError(errors.New("Server error")))
+				_, _ = io.Copy(conn, rdr)
+			}
+		}()
+		response = ss.handler.Handle(ctx, request)
+		if response == nil {
+			response = ClientError(errors.New("Resource does not exist."))
+		}
+	}
+
+	defer response.Close()
+	_, _ = io.Copy(conn, NewResponseReader(response))
+}