Add GET endpoints for getting the state of the finder

* GET / (or GET /current)
* GET /query

CHANGELOG.md

@@ -3,13 +3,21 @@ CHANGELOG
 
 0.36.0
 ------
-- Added `--listen=HTTP_PORT` option to receive actions from external processes
+- Added `--listen=HTTP_PORT` option to start HTTP server. It allows external
+  processes to send actions to perform via POST method, or retrieve the
+  current state of the finder.
   ```sh
   # Start HTTP server on port 6266
   fzf --listen 6266
 
-  # Send actions to the server
-  curl -XPOST localhost:6266 -d 'reload(seq 100)+change-prompt(hundred> )'
+  # Send action to the server via POST method
+  curl localhost:6266 -d 'reload(seq 100)+change-prompt(hundred> )'
+
+  # Retrieve the current item
+  curl localhost:6266
+
+  # Retrieve the query string
+  curl localhost:6266/query
   ```
 - Added `next-selected` and `prev-selected` actions to move between selected
   items

man/man1/fzf.1

@@ -722,14 +722,22 @@ e.g. \fBfzf --multi | fzf --sync\fR
 .RE
 .TP
 .B "--listen=HTTP_PORT"
-Start HTTP server on the given port to receive actions via POST requests.
+Start HTTP server on the given port. It allows external processes to send
+actions to perform via POST method, or retrieve the current state of the
+finder.
 
 e.g.
      \fB# Start HTTP server on port 6266
      fzf --listen 6266
 
-     # Send action to the server
-     curl -XPOST localhost:6266 -d 'reload(seq 100)+change-prompt(hundred> )'
+     # Send action to the server via POST method
+     curl localhost:6266 -d 'reload(seq 100)+change-prompt(hundred> )'
+
+     # Retrieve the current item
+     curl localhost:6266
+
+     # Retrieve the query string
+     curl localhost:6266/query
      \fR
 
 The port number is exported as \fB$FZF_LISTEN_PORT\fR on the child processes.

src/options.go

@@ -113,7 +113,7 @@ const usage = `usage: fzf [options]
     --read0                Read input delimited by ASCII NUL characters
     --print0               Print output delimited by ASCII NUL characters
     --sync                 Synchronous search for multi-staged filtering
-    --listen=HTTP_PORT     Start HTTP server to receive actions (POST /)
+    --listen=HTTP_PORT     Start HTTP server to receive actions
     --version              Display version information and exit
 
   Environment variables

src/server.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -13,13 +14,18 @@ import (
 
 const (
 	crlf             = "\r\n"
+	httpPattern      = "^(GET|POST) (/[^ ]*) HTTP"
 	httpOk           = "HTTP/1.1 200 OK" + crlf
 	httpBadRequest   = "HTTP/1.1 400 Bad Request" + crlf
 	httpReadTimeout  = 10 * time.Second
 	maxContentLength = 1024 * 1024
 )
 
-func startHttpServer(port int, channel chan []*action) error {
+var (
+	httpRegexp *regexp.Regexp
+)
+
+func startHttpServer(port int, requestChan chan []*action, responseChan chan string) error {
 	if port == 0 {
 		return nil
 	}
@@ -29,6 +35,7 @@ func startHttpServer(port int, channel chan []*action) error {
 		return fmt.Errorf("port not available: %d", port)
 	}
 
+	httpRegexp = regexp.MustCompile(httpPattern)
 	go func() {
 		for {
 			conn, err := listener.Accept()
@@ -39,7 +46,7 @@ func startHttpServer(port int, channel chan []*action) error {
 					continue
 				}
 			}
-			conn.Write([]byte(handleHttpRequest(conn, channel)))
+			conn.Write([]byte(handleHttpRequest(conn, requestChan, responseChan)))
 			conn.Close()
 		}
 		listener.Close()
@@ -54,12 +61,14 @@ func startHttpServer(port int, channel chan []*action) error {
 // * No --listen:            2.8MB
 // * --listen with net/http: 5.7MB
 // * --listen w/o net/http:  3.3MB
-func handleHttpRequest(conn net.Conn, channel chan []*action) string {
+func handleHttpRequest(conn net.Conn, requestChan chan []*action, responseChan chan string) string {
 	contentLength := 0
 	body := ""
+	response := func(header string, message string) string {
+		return header + fmt.Sprintf("Content-Length: %d%s", len(message), crlf+crlf+message)
+	}
 	bad := func(message string) string {
-		message += "\n"
-		return httpBadRequest + fmt.Sprintf("Content-Length: %d%s", len(message), crlf+crlf+message)
+		return response(httpBadRequest, strings.TrimSpace(message)+"\n")
 	}
 	conn.SetReadDeadline(time.Now().Add(httpReadTimeout))
 	scanner := bufio.NewScanner(conn)
@@ -80,8 +89,13 @@ func handleHttpRequest(conn net.Conn, channel chan []*action) string {
 		text := scanner.Text()
 		switch section {
 		case 0:
-			if !strings.HasPrefix(text, "POST / HTTP") {
-				return bad("invalid request method")
+			httpMatch := httpRegexp.FindStringSubmatch(text)
+			if len(httpMatch) != 3 {
+				return bad("invalid HTTP request: " + text)
+			}
+			if httpMatch[1] == "GET" {
+				requestChan <- []*action{{t: actEvaluate, a: httpMatch[2][1:]}}
+				return response(httpOk, <-responseChan)
 			}
 			section++
 		case 1:
@@ -120,7 +134,6 @@ func handleHttpRequest(conn net.Conn, channel chan []*action) string {
 	if len(actions) == 0 {
 		return bad("no action specified")
 	}
-
-	channel <- actions
+	requestChan <- actions
 	return httpOk
 }

src/terminal.go

@@ -201,7 +201,8 @@ type Terminal struct {
 	sigstop            bool
 	startChan          chan fitpad
 	killChan           chan int
-	serverChan         chan []*action
+	serverRequestChan  chan []*action
+	serverResponseChan chan string
 	slab               *util.Slab
 	theme              *tui.ColorTheme
 	tui                tui.Renderer
@@ -276,6 +277,7 @@ const (
 	actDeleteChar
 	actDeleteCharEOF
 	actEndOfLine
+	actEvaluate
 	actForwardChar
 	actForwardWord
 	actKillLine
@@ -599,7 +601,8 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		theme:              opts.Theme,
 		startChan:          make(chan fitpad, 1),
 		killChan:           make(chan int),
-		serverChan:         make(chan []*action),
+		serverRequestChan:  make(chan []*action),
+		serverResponseChan: make(chan string),
 		tui:                renderer,
 		initFunc:           func() { renderer.Init() },
 		executing:          util.NewAtomicBool(false)}
@@ -621,7 +624,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		t.separator, t.separatorLen = t.ansiLabelPrinter(bar, &tui.ColSeparator, true)
 	}
 
-	if err := startHttpServer(t.listenPort, t.serverChan); err != nil {
+	if err := startHttpServer(t.listenPort, t.serverRequestChan, t.serverResponseChan); err != nil {
 		errorExit(err.Error())
 	}
 
@@ -2531,7 +2534,7 @@ func (t *Terminal) Loop() {
 			select {
 			case event = <-eventChan:
 				needBarrier = true
-			case actions = <-t.serverChan:
+			case actions = <-t.serverRequestChan:
 				event = tui.Invalid.AsEvent()
 				needBarrier = false
 			}
@@ -2614,6 +2617,15 @@ func (t *Terminal) Loop() {
 				t.executeCommand(a.a, false, a.t == actExecuteSilent)
 			case actExecuteMulti:
 				t.executeCommand(a.a, true, false)
+			case actEvaluate:
+				response := ""
+				switch a.a {
+				case "", "current":
+					response = t.currentItem().AsString(t.ansi)
+				case "query":
+					response = string(t.input)
+				}
+				t.serverResponseChan <- response
 			case actInvalid:
 				t.mutex.Unlock()
 				return false

test/test_go.rb

@@ -2440,9 +2440,12 @@ class TestGoFZF < TestBase
   def test_listen
     tmux.send_keys 'seq 10 | fzf --listen 6266', :Enter
     tmux.until { |lines| assert_equal 10, lines.item_count }
-    Net::HTTP.post(URI('http://localhost:6266'), 'change-query(yo)+reload(seq 100)+change-prompt:hundred> ')
+    Net::HTTP.post(URI('http://localhost:6266'), 'change-query(00)+reload(seq 100)+change-prompt:hundred> ')
     tmux.until { |lines| assert_equal 100, lines.item_count }
-    tmux.until { |lines| assert_equal 'hundred> yo', lines[-1] }
+    tmux.until { |lines| assert_equal 'hundred> 00', lines[-1] }
+    assert_equal '100', Net::HTTP.get(URI('http://localhost:6266'))
+    assert_equal '100', Net::HTTP.get(URI('http://localhost:6266/current'))
+    assert_equal '00', Net::HTTP.get(URI('http://localhost:6266/query'))
   end
 end