feat: add kotlin scaffolding (#500)

eg.

```
ftl init kotlin examples/foo
```

Bitfile

@@ -54,18 +54,22 @@ NODE_MODULES_IN = console/client/package{,-lock}.json
 %{RELEASE}/ftl-runner: %{RELEASE} %{GO_SOURCES} cmd/ftl-runner/**/*.go
   build: go build -o %{OUT} -tags release -ldflags "-X main.version=%{VERSION} -X main.timestamp=$(date +%s)" ./cmd/ftl-runner
 
-%{RELEASE}/ftl: %{RELEASE} %{GO_SOURCES} cmd/ftl/**/*.go go-runtime/scaffolding.zip
+%{RELEASE}/ftl: %{RELEASE} %{GO_SOURCES} cmd/ftl/**/*.go {go,kotlin}-runtime/scaffolding.zip
   build: go build -o %{OUT} -tags release -ldflags "-X main.version=%{VERSION} -X main.timestamp=$(date +%s)" ./cmd/ftl
 
 %{RELEASE}/ftl-initdb: %{RELEASE} %{GO_SOURCES} cmd/ftl-initdb/**/*.go
   build: go build -o %{OUT} -tags release -ldflags "-X main.version=%{VERSION} -X main.timestamp=$(date +%s)" ./cmd/ftl-initdb
 
 # Release builds include zipped scaffolding becaused raw go:embed doesn't
 # preserve permissions or symlinks. Irritating.
-go-runtime/scaffolding.zip: go-runtime/scaffolding/*
+go-runtime/scaffolding.zip: go-runtime/scaffolding/**/*
   cd go-runtime/scaffolding
   build: zip -q --symlinks -r ../scaffolding.zip .
 
+kotlin-runtime/scaffolding.zip: kotlin-runtime/scaffolding/**/*
+  cd kotlin-runtime/scaffolding
+  build: zip -q --symlinks -r ../scaffolding.zip .
+
 %{SCHEMA_OUT}: %{SCHEMA_IN}
   build:
     ftl-schema > %{OUT}

Makefile

@@ -58,6 +58,7 @@ build/release/%: console/client/dist/index.html
 
 build/release/ftl:
 	cd go-runtime/scaffolding && zip -q --symlinks -r ../scaffolding.zip .
+	cd kotlin-runtime/scaffolding && zip -q --symlinks -r ../scaffolding.zip .
 	go build -o $@ -tags release -ldflags "-X main.version=$(VERSION) -X main.timestamp=$(shell date +%s)" ./cmd/ftl
 
 $(KT_MVN_OUT): $(KT_RUNTIME_IN)

cmd/ftl/cmd_init.go

@@ -11,6 +11,7 @@ import (
 	"github.com/TBD54566975/ftl/backend/common/log"
 	goruntime "github.com/TBD54566975/ftl/go-runtime"
 	"github.com/TBD54566975/ftl/internal"
+	kotlinruntime "github.com/TBD54566975/ftl/kotlin-runtime"
 )
 
 type initCmd struct {
@@ -21,8 +22,8 @@ type initCmd struct {
 
 type initGoCmd struct {
 	Dir      string `arg:"" default:"." type:"dir" help:"Directory to initialize the module in."`
-	Name     string `help:"Name of the FTL module (defaults to name of directory)."`
-	GoModule string `required:"" help:"Go module path."`
+	Name     string `short:"n" help:"Name of the FTL module (defaults to name of directory)."`
+	GoModule string `short:"G" required:"" help:"Go module import path."`
 }
 
 func (i initGoCmd) Run(ctx context.Context, parent *initCmd) error {
@@ -44,9 +45,21 @@ func (i initGoCmd) Run(ctx context.Context, parent *initCmd) error {
 }
 
 type initKotlinCmd struct {
-	Dir string `arg:"" default:"." help:"Directory to initialize the module in."`
+	Dir  string `arg:"" default:"." help:"Directory to initialize the module in."`
+	Name string `short:"n" help:"Name of the FTL module (defaults to name of directory)."`
 }
 
-func (i *initKotlinCmd) Run() error {
-	panic("??")
+func (i *initKotlinCmd) Run(parent *initCmd) error {
+	if i.Name == "" {
+		i.Name = filepath.Base(i.Dir)
+	}
+	if err := internal.Scaffold(kotlinruntime.Files, i.Dir, i); err != nil {
+		return errors.WithStack(err)
+	}
+	if !parent.Hermit {
+		if err := os.RemoveAll(filepath.Join(i.Dir, "bin")); err != nil {
+			return errors.WithStack(err)
+		}
+	}
+	return nil
 }

internal/scaffolder.go

@@ -24,22 +24,25 @@ func Scaffold(source *zip.Reader, destination string, ctx any) error {
 	if err != nil {
 		return errors.WithStack(err)
 	}
-	return errors.WithStack(filepath.WalkDir(destination, func(path string, d fs.DirEntry, err error) error {
+	return errors.WithStack(walkDir(destination, func(path string, d fs.DirEntry) error {
 		if err != nil {
-			return err
+			return errors.WithStack(err)
 		}
 		info, err := d.Info()
 		if err != nil {
 			return errors.WithStack(err)
 		}
 
 		// Evaluate path name templates.
-		newName, err := evaluate(path, ctx)
+		dir := filepath.Dir(path)
+		base := filepath.Base(path)
+		newName, err := evaluate(base, ctx)
 		if err != nil {
 			return errors.Wrapf(err, "%s", path)
 		}
 		// Rename if necessary.
-		if newName != path {
+		if newName != base {
+			newName = filepath.Join(dir, newName)
 			err = os.Rename(path, newName)
 			if err != nil {
 				return errors.Wrap(err, "failed to rename file")
@@ -68,6 +71,26 @@ func Scaffold(source *zip.Reader, destination string, ctx any) error {
 	}))
 }
 
+func walkDir(dir string, fn func(path string, d fs.DirEntry) error) error {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+	for _, entry := range entries {
+		if entry.IsDir() {
+			err = walkDir(filepath.Join(dir, entry.Name()), fn)
+			if err != nil {
+				return errors.WithStack(err)
+			}
+		}
+		err = fn(filepath.Join(dir, entry.Name()), entry)
+		if err != nil {
+			return errors.WithStack(err)
+		}
+	}
+	return nil
+}
+
 func evaluate(tmpl string, ctx any) (string, error) {
 	t, err := template.New("scaffolding").Funcs(
 		template.FuncMap{

kotlin-runtime/devel.go

@@ -0,0 +1,47 @@
+//go:build !release
+
+package kotlinruntime
+
+import (
+	"archive/zip"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/TBD54566975/ftl/internal"
+)
+
+// Files is the FTL Kotlin runtime scaffolding files.
+var Files = func() *zip.Reader {
+	cmd := exec.Command("git", "rev-parse", "--show-toplevel")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		panic(err)
+	}
+	dir := filepath.Join(strings.TrimSpace(string(out)), "kotlin-runtime", "scaffolding")
+	w, err := os.CreateTemp("", "")
+	if err != nil {
+		panic(err)
+	}
+	defer os.Remove(w.Name()) // This is okay because the zip.Reader will keep it open.
+	if err != nil {
+		panic(err)
+	}
+
+	err = internal.ZipDir(dir, w.Name())
+	if err != nil {
+		panic(err)
+	}
+
+	info, err := w.Stat()
+	if err != nil {
+		panic(err)
+	}
+	_, _ = w.Seek(0, 0)
+	zr, err := zip.NewReader(w, info.Size())
+	if err != nil {
+		panic(err)
+	}
+	return zr
+}()

kotlin-runtime/release.go

@@ -0,0 +1,24 @@
+//go:build release
+
+package goruntime
+
+import (
+	"archive/zip"
+	"bytes"
+	_ "embed"
+)
+
+//go:embed scaffolding.zip
+var archive []byte
+
+// Files is the FTL Kotlin runtime scaffolding files.
+//
+// scaffolding.zip can be generated by running `bit kotlin-runtime/scaffolding.zip`
+// or indirectly via `bit build/release/ftl`.
+var Files = func() *zip.Reader {
+	zr, err := zip.NewReader(bytes.NewReader(archive), int64(len(archive)))
+	if err != nil {
+		panic(err)
+	}
+	return zr
+}()

kotlin-runtime/scaffolding/bin/.maven-3.8.6.pkg

@@ -0,0 +1 @@
+hermit

kotlin-runtime/scaffolding/bin/.openjdk-17.0.8_7.pkg

@@ -0,0 +1 @@
+hermit

kotlin-runtime/scaffolding/bin/README.hermit.md

@@ -0,0 +1,7 @@
+# Hermit environment
+
+This is a [Hermit](https://github.com/cashapp/hermit) bin directory.
+
+The symlinks in this directory are managed by Hermit and will automatically
+download and install Hermit itself as well as packages. These packages are
+local to this environment.

kotlin-runtime/scaffolding/bin/activate-hermit

@@ -0,0 +1,21 @@
+#!/bin/bash
+# This file must be used with "source bin/activate-hermit" from bash or zsh.
+# You cannot run it directly
+#
+# THIS FILE IS GENERATED; DO NOT MODIFY
+
+if [ "${BASH_SOURCE-}" = "$0" ]; then
+  echo "You must source this script: \$ source $0" >&2
+  exit 33
+fi
+
+BIN_DIR="$(dirname "${BASH_SOURCE[0]:-${(%):-%x}}")"
+if "${BIN_DIR}/hermit" noop > /dev/null; then
+  eval "$("${BIN_DIR}/hermit" activate "${BIN_DIR}/..")"
+
+  if [ -n "${BASH-}" ] || [ -n "${ZSH_VERSION-}" ]; then
+      hash -r 2>/dev/null
+    fi
+
+    echo "Hermit environment $("${HERMIT_ENV}"/bin/hermit env HERMIT_ENV) activated"
+fi

kotlin-runtime/scaffolding/bin/hermit

@@ -0,0 +1,43 @@
+#!/bin/bash
+#
+# THIS FILE IS GENERATED; DO NOT MODIFY
+
+set -eo pipefail
+
+export HERMIT_USER_HOME=~
+
+if [ -z "${HERMIT_STATE_DIR}" ]; then
+  case "$(uname -s)" in
+  Darwin)
+    export HERMIT_STATE_DIR="${HERMIT_USER_HOME}/Library/Caches/hermit"
+    ;;
+  Linux)
+    export HERMIT_STATE_DIR="${XDG_CACHE_HOME:-${HERMIT_USER_HOME}/.cache}/hermit"
+    ;;
+  esac
+fi
+
+export HERMIT_DIST_URL="${HERMIT_DIST_URL:-https://github.com/cashapp/hermit/releases/download/stable}"
+HERMIT_CHANNEL="$(basename "${HERMIT_DIST_URL}")"
+export HERMIT_CHANNEL
+export HERMIT_EXE=${HERMIT_EXE:-${HERMIT_STATE_DIR}/pkg/hermit@${HERMIT_CHANNEL}/hermit}
+
+if [ ! -x "${HERMIT_EXE}" ]; then
+  echo "Bootstrapping ${HERMIT_EXE} from ${HERMIT_DIST_URL}" 1>&2
+  INSTALL_SCRIPT="$(mktemp)"
+  # This value must match that of the install script
+  INSTALL_SCRIPT_SHA256="180e997dd837f839a3072a5e2f558619b6d12555cd5452d3ab19d87720704e38"
+  if [ "${INSTALL_SCRIPT_SHA256}" = "BYPASS" ]; then
+    curl -fsSL "${HERMIT_DIST_URL}/install.sh" -o "${INSTALL_SCRIPT}"
+  else
+    # Install script is versioned by its sha256sum value
+    curl -fsSL "${HERMIT_DIST_URL}/install-${INSTALL_SCRIPT_SHA256}.sh" -o "${INSTALL_SCRIPT}"
+    # Verify install script's sha256sum
+    openssl dgst -sha256 "${INSTALL_SCRIPT}" | \
+      awk -v EXPECTED="$INSTALL_SCRIPT_SHA256" \
+      '$2!=EXPECTED {print "Install script sha256 " $2 " does not match " EXPECTED; exit 1}'
+  fi
+  /bin/bash "${INSTALL_SCRIPT}" 1>&2
+fi
+
+exec "${HERMIT_EXE}" --level=fatal exec "$0" -- "$@"

kotlin-runtime/scaffolding/bin/jar

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jarsigner

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/java

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/javac

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/javadoc

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/javap

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jcmd

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jconsole

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jdb

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jdeprscan

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jdeps

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jfr

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jhsdb

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jimage

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jinfo

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jlink

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jmap

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jmod

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jpackage

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jps

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jrunscript

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jshell

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jstack

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jstat

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/jstatd

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/keytool

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/mvn

@@ -0,0 +1 @@
+.maven-3.8.6.pkg

kotlin-runtime/scaffolding/bin/rmiregistry

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/bin/serialver

@@ -0,0 +1 @@
+.openjdk-17.0.8_7.pkg

kotlin-runtime/scaffolding/ftl.toml

@@ -0,0 +1,8 @@
+module = "{{ .Name | lower }}"
+language = "kotlin"
+deploy = [
+  "target/main",
+  "target/classes",
+  "target/dependency",
+  "target/classpath.txt",
+]