Add --listen=HTTP_PORT option to receive actions

Supersedes #2019

See also:
* #1728
* https://github.com/junegunn/fzf.vim/pull/1044

src/terminal.go

@@ -3,8 +3,10 @@ package fzf
 import (
 	"bufio"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"math"
+	"net/http"
 	"os"
 	"os/signal"
 	"regexp"
@@ -167,6 +169,7 @@ type Terminal struct {
 	padding            [4]sizeSpec
 	strong             tui.Attr
 	unicode            bool
+	listenPort         int
 	borderShape        tui.BorderShape
 	cleanExit          bool
 	paused             bool
@@ -200,6 +203,7 @@ type Terminal struct {
 	sigstop            bool
 	startChan          chan fitpad
 	killChan           chan int
+	serverChan         chan []*action
 	slab               *util.Slab
 	theme              *tui.ColorTheme
 	tui                tui.Renderer
@@ -481,7 +485,8 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 	}
 	var previewBox *util.EventBox
 	showPreviewWindow := len(opts.Preview.command) > 0 && !opts.Preview.hidden
-	if len(opts.Preview.command) > 0 || hasPreviewAction(opts) {
+	// We need to start previewer if HTTP server is enabled even when --preview option is not specified
+	if len(opts.Preview.command) > 0 || hasPreviewAction(opts) || opts.ListenPort > 0 {
 		previewBox = util.NewEventBox()
 	}
 	strongAttr := tui.Bold
@@ -556,6 +561,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		margin:             opts.Margin,
 		padding:            opts.Padding,
 		unicode:            opts.Unicode,
+		listenPort:         opts.ListenPort,
 		borderShape:        opts.BorderShape,
 		borderLabel:        nil,
 		borderLabelOpts:    opts.BorderLabel,
@@ -595,6 +601,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		theme:              opts.Theme,
 		startChan:          make(chan fitpad, 1),
 		killChan:           make(chan int),
+		serverChan:         make(chan []*action),
 		tui:                renderer,
 		initFunc:           func() { renderer.Init() },
 		executing:          util.NewAtomicBool(false)}
@@ -619,6 +626,39 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 	return &t
 }
 
+func (t *Terminal) startServer() {
+	if t.listenPort == 0 {
+		return
+	}
+
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != "POST" {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+		body, err := io.ReadAll(r.Body)
+		if err != nil {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+
+		response := ""
+		actions := parseSingleActionList(string(body), func(message string) {
+			response = message
+		})
+
+		if len(response) > 0 {
+			w.WriteHeader(http.StatusBadRequest)
+			fmt.Fprintln(w, response)
+			return
+		}
+		t.serverChan <- actions
+	})
+	go func() {
+		http.ListenAndServe(fmt.Sprintf(":%d", t.listenPort), nil)
+	}()
+}
+
 func borderLines(shape tui.BorderShape) int {
 	switch shape {
 	case tui.BorderHorizontal, tui.BorderRounded, tui.BorderSharp, tui.BorderBold, tui.BorderDouble:
@@ -2256,6 +2296,9 @@ func (t *Terminal) Loop() {
 						env = append(env, "FZF_PREVIEW_"+lines)
 						env = append(env, columns)
 						env = append(env, "FZF_PREVIEW_"+columns)
+						if t.listenPort > 0 {
+							env = append(env, fmt.Sprintf("FZF_LISTEN_PORT=%d", t.listenPort))
+						}
 						cmd.Env = env
 					}
 
@@ -2492,6 +2535,16 @@ func (t *Terminal) Loop() {
 	looping := true
 	_, startEvent := t.keymap[tui.Start.AsEvent()]
 
+	t.startServer()
+	eventChan := make(chan tui.Event)
+	needBarrier := true
+	barrier := make(chan bool)
+	go func() {
+		for {
+			<-barrier
+			eventChan <- t.tui.GetChar()
+		}
+	}()
 	for looping {
 		var newCommand *string
 		changed := false
@@ -2499,11 +2552,21 @@ func (t *Terminal) Loop() {
 		queryChanged := false
 
 		var event tui.Event
+		actions := []*action{}
 		if startEvent {
 			event = tui.Start.AsEvent()
 			startEvent = false
 		} else {
-			event = t.tui.GetChar()
+			if needBarrier {
+				barrier <- true
+			}
+			select {
+			case event = <-eventChan:
+				needBarrier = true
+			case actions = <-t.serverChan:
+				event = tui.Invalid.AsEvent()
+				needBarrier = false
+			}
 		}
 
 		t.mutex.Lock()
@@ -3043,7 +3106,9 @@ func (t *Terminal) Loop() {
 		}
 
 		if t.jumping == jumpDisabled {
-			actions := t.keymap[event.Comparable()]
+			if len(actions) == 0 {
+				actions = t.keymap[event.Comparable()]
+			}
 			if len(actions) == 0 && event.Type == tui.Rune {
 				doAction(&action{t: actRune})
 			} else if !doActions(actions) {