From cc0c7e6eb5b27c3a263352ba40ce8ee5209272a2 Mon Sep 17 00:00:00 2001
From: tjpcc <tjp@ctrl-c.club>
Date: Wed, 11 Jan 2023 10:12:32 -0700
Subject: Simple client functionality and an example.

---
 TODO.md                |  4 ++-
 examples/fetch/main.go | 65 +++++++++++++++++++++++++++++++++++++++++++++++
 gemini/client.go       | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++
 gemini/response.go     |  5 +++-
 4 files changed, 141 insertions(+), 2 deletions(-)
 create mode 100644 examples/fetch/main.go
 create mode 100644 gemini/client.go

diff --git a/TODO.md b/TODO.md
index 63e748a..68137bc 100644
--- a/TODO.md
+++ b/TODO.md
@@ -1,6 +1,8 @@
 - [x] server
   - [x] TLS configuration from cert+key files
-- [ ] client
+- [x] client
+  - [ ] follow redirects
+- [ ] reject non-gemini requests
 - [x] contrib - filesystem handling
   - [x] serving files
   - [x] directory index files
diff --git a/examples/fetch/main.go b/examples/fetch/main.go
new file mode 100644
index 0000000..adfece4
--- /dev/null
+++ b/examples/fetch/main.go
@@ -0,0 +1,65 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/url"
+	"os"
+	"strings"
+
+	"tildegit.org/tjp/gus/gemini"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintf(os.Stderr, "usage: %s <gemini url>\n", os.Args[0])
+	}
+
+	certfile, keyfile := envConfig()
+
+	// build a client
+	var client gemini.Client
+	if certfile != "" && keyfile != "" {
+		tlsConf, err := gemini.FileTLS(certfile, keyfile)
+		if err != nil {
+			log.Fatal(err)
+		}
+		client = gemini.NewClient(tlsConf)
+	}
+
+	// parse the URL and build the request
+	request := &gemini.Request{URL: buildURL()}
+
+	// fetch the response
+	response, err := client.RoundTrip(request)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if response.Status != gemini.StatusSuccess {
+		log.Fatalf("%d %s\n", response.Status, response.Meta)
+	}
+
+	//io.Copy(os.Stdout, response)
+	buf, err := io.ReadAll(response)
+	fmt.Printf("response: %s\n", buf)
+}
+
+func envConfig() (string, string) {
+	return os.Getenv("SERVER_CERTIFICATE"), os.Getenv("SERVER_PRIVATEKEY")
+}
+
+func buildURL() *url.URL {
+	raw := os.Args[1]
+	if strings.HasPrefix(raw, "//") {
+		raw = "gemini:" + raw
+	}
+
+	u, err := url.Parse(raw)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	return u
+}
diff --git a/gemini/client.go b/gemini/client.go
new file mode 100644
index 0000000..53c8b71
--- /dev/null
+++ b/gemini/client.go
@@ -0,0 +1,69 @@
+package gemini
+
+import (
+	"bytes"
+	"crypto/tls"
+	"errors"
+	"io"
+	"net"
+)
+
+// Client is used for sending gemini requests and parsing gemini responses.
+//
+// It carries no state and is usable and reusable simultaneously by multiple goroutines.
+// The only reason you might create more than one Client is to support separate TLS-cert
+// driven identities.
+//
+// The zero value of Client is usable, it simply has no client TLS cert.
+type Client struct {
+	tlsConf *tls.Config
+}
+
+// Create a gemini Client with the given TLS configuration.
+func NewClient(tlsConf *tls.Config) Client {
+	return Client{tlsConf: tlsConf}
+}
+
+// RoundTrip sends a single gemini request to the correct server and returns its response.
+//
+// It also populates the TLSState and RemoteAddr fields on the request - the only field
+// it needs populated beforehand is the URL.
+func (client Client) RoundTrip(request *Request) (*Response, error) {
+	if request.Scheme != "gemini" && request.Scheme != "" {
+		return nil, errors.New("non-gemini protocols not supported")
+	}
+
+	host := request.Host
+	if _, port, _ := net.SplitHostPort(host); port == "" {
+		host += ":1965"
+	}
+
+	conn, err := tls.Dial("tcp", host, client.tlsConf)
+	if err != nil {
+		return nil, err
+	}
+	defer conn.Close()
+
+	request.RemoteAddr = conn.RemoteAddr()
+	st := conn.ConnectionState()
+	request.TLSState = &st
+
+	if _, err := conn.Write([]byte(request.URL.String() + "\r\n")); err != nil {
+		return nil, err
+	}
+
+	response, err := ParseResponse(conn)
+	if err != nil {
+		return nil, err
+	}
+
+	// read and store the request body in full or we may miss doing so before the
+	// connection gets closed.
+	bodybuf, err := io.ReadAll(response.Body)
+	if err != nil {
+		return nil, err
+	}
+	response.Body = bytes.NewBuffer(bodybuf)
+
+	return response, nil
+}
diff --git a/gemini/response.go b/gemini/response.go
index 478913b..1fa64cf 100644
--- a/gemini/response.go
+++ b/gemini/response.go
@@ -283,6 +283,9 @@ func ParseResponse(rdr io.Reader) (*Response, error) {
 	if hdrLine[len(hdrLine)-2] != '\r' {
 		return nil, InvalidResponseLineEnding
 	}
+	if hdrLine[2] != ' ' {
+		return nil, InvalidResponseHeaderLine
+	}
 	hdrLine = hdrLine[:len(hdrLine)-2]
 
 	status, err := strconv.Atoi(string(hdrLine[:2]))
@@ -292,7 +295,7 @@ func ParseResponse(rdr io.Reader) (*Response, error) {
 
 	return &Response{
 		Status: Status(status),
-		Meta:   string(hdrLine[2:]),
+		Meta:   string(hdrLine[3:]),
 		Body:   bufrdr,
 	}, nil
 }
-- 
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