From 8617bd7b96bbc8496af0d8059893adc614617ffc Mon Sep 17 00:00:00 2001
From: Stuart Douglas <stuart.w.douglas@gmail.com>
Date: Thu, 19 Sep 2024 16:57:46 +1000
Subject: [PATCH] feat: completion for interactive mode

fixes: #2708
---
 frontend/cli/cmd_interactive.go | 87 +++++++++++++++++++++++++++++++--
 frontend/cli/main.go            |  5 +-
 2 files changed, 87 insertions(+), 5 deletions(-)

diff --git a/frontend/cli/cmd_interactive.go b/frontend/cli/cmd_interactive.go
index dac5845282..51dfed711f 100644
--- a/frontend/cli/cmd_interactive.go
+++ b/frontend/cli/cmd_interactive.go
@@ -9,19 +9,28 @@ import (
 
 	"github.com/alecthomas/kong"
 	"github.com/chzyer/readline"
+	kongcompletion "github.com/jotaen/kong-completion"
 	"github.com/kballard/go-shellquote"
+	"github.com/posener/complete"
 
 	"github.com/TBD54566975/ftl/internal/projectconfig"
 )
 
+var _ readline.AutoCompleter = &FTLCompletion{}
+
 type interactiveCmd struct {
 }
 
-func (i *interactiveCmd) Run(ctx context.Context, k *kong.Kong, projectConfig projectconfig.Config) error {
+type FTLCompletion struct {
+	app *kong.Kong
+}
+
+func (i *interactiveCmd) Run(ctx context.Context, k *kong.Kong, projectConfig projectconfig.Config, app *kong.Kong) error {
 	l, err := readline.NewEx(&readline.Config{
 		Prompt:          "\033[32m>\033[0m ",
 		InterruptPrompt: "^C",
 		EOFPrompt:       "exit",
+		AutoComplete:    &FTLCompletion{app: app},
 	})
 	if err != nil {
 		return fmt.Errorf("init readline: %w", err)
@@ -38,6 +47,9 @@ func (i *interactiveCmd) Run(ctx context.Context, k *kong.Kong, projectConfig pr
 			break
 		}
 		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
 		args, err := shellquote.Split(line)
 		if err != nil {
 			errorf("%s", err)
@@ -48,11 +60,11 @@ func (i *interactiveCmd) Run(ctx context.Context, k *kong.Kong, projectConfig pr
 			errorf("%s", err)
 			continue
 		}
-		subctx := bindContext(ctx, kctx, projectConfig)
+		subctx := bindContext(ctx, kctx, projectConfig, app)
 
 		err = kctx.Run(subctx)
 		if err != nil {
-			errorf("%s", err)
+			errorf("error: %s", err)
 			continue
 		}
 	}
@@ -62,3 +74,72 @@ func (i *interactiveCmd) Run(ctx context.Context, k *kong.Kong, projectConfig pr
 func errorf(format string, args ...any) {
 	fmt.Printf("\033[31m%s\033[0m\n", fmt.Sprintf(format, args...))
 }
+
+func (f *FTLCompletion) Do(line []rune, pos int) ([][]rune, int) {
+	parser := f.app
+	if parser == nil {
+		return nil, 0
+	}
+	all := []string{}
+	completed := []string{}
+	last := ""
+	lastCompleted := ""
+	lastSpace := false
+	// We don't care about anything past pos
+	// this completer can't handle completing in the middle of things
+	if pos < len(line) {
+		line = line[:pos]
+	}
+	current := 0
+	for i, arg := range line {
+		if i == pos {
+			break
+		}
+		if arg == ' ' {
+			lastWord := string(line[current:i])
+			all = append(all, lastWord)
+			completed = append(completed, lastWord)
+			current = i + 1
+			lastSpace = true
+		} else {
+			lastSpace = false
+		}
+	}
+	if pos > 0 {
+		if lastSpace {
+			lastCompleted = all[len(all)-1]
+		} else {
+			if current < len(line) {
+				last = string(line[current:])
+				all = append(all, last)
+			}
+			if len(all) > 0 {
+				lastCompleted = all[len(all)-1]
+			}
+		}
+	}
+
+	args := complete.Args{
+		Completed:     completed,
+		All:           all,
+		Last:          last,
+		LastCompleted: lastCompleted,
+	}
+
+	command, err := kongcompletion.Command(parser)
+	if err != nil {
+		// TODO handle error
+		println(err.Error())
+	}
+	result := command.Predict(args)
+	runes := [][]rune{}
+	for _, s := range result {
+		if !strings.HasPrefix(s, last) || s == "interactive" {
+			continue
+		}
+		s = s[len(last):]
+		str := []rune(s)
+		runes = append(runes, str)
+	}
+	return runes, pos
+}
diff --git a/frontend/cli/main.go b/frontend/cli/main.go
index 98beec3839..9fdc878dfa 100644
--- a/frontend/cli/main.go
+++ b/frontend/cli/main.go
@@ -132,14 +132,15 @@ func main() {
 	if err != nil && !errors.Is(err, os.ErrNotExist) {
 		kctx.FatalIfErrorf(err)
 	}
-	ctx = bindContext(ctx, kctx, config)
+	ctx = bindContext(ctx, kctx, config, app)
 
 	err = kctx.Run(ctx)
 	kctx.FatalIfErrorf(err)
 }
 
-func bindContext(ctx context.Context, kctx *kong.Context, projectConfig projectconfig.Config) context.Context {
+func bindContext(ctx context.Context, kctx *kong.Context, projectConfig projectconfig.Config, app *kong.Kong) context.Context {
 	kctx.Bind(projectConfig)
+	kctx.Bind(app)
 
 	controllerServiceClient := rpc.Dial(ftlv1connect.NewControllerServiceClient, cli.Endpoint.String(), log.Error)
 	ctx = rpc.ContextWithClient(ctx, controllerServiceClient)