feat(sdk): add TypeScript generator

Implements TypeScript SDK generator with three-level fallback:
1. Native openapi-typescript-codegen if installed globally
2. npx openapi-typescript-codegen if npx available
3. Docker openapitools/openapi-generator-cli as fallback

Includes tests following _Good convention for Available and Generate.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pkg/sdk/generators/typescript.go

@@ -0,0 +1,106 @@
+package generators
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+)
+
+// TypeScriptGenerator generates TypeScript SDKs from OpenAPI specs.
+type TypeScriptGenerator struct{}
+
+// NewTypeScriptGenerator creates a new TypeScript generator.
+func NewTypeScriptGenerator() *TypeScriptGenerator {
+	return &TypeScriptGenerator{}
+}
+
+// Language returns the generator's target language identifier.
+func (g *TypeScriptGenerator) Language() string {
+	return "typescript"
+}
+
+// Available checks if generator dependencies are installed.
+func (g *TypeScriptGenerator) Available() bool {
+	_, err := exec.LookPath("openapi-typescript-codegen")
+	if err == nil {
+		return true
+	}
+	_, err = exec.LookPath("npx")
+	return err == nil
+}
+
+// Install returns instructions for installing the generator.
+func (g *TypeScriptGenerator) Install() string {
+	return "npm install -g openapi-typescript-codegen"
+}
+
+// Generate creates SDK from OpenAPI spec.
+func (g *TypeScriptGenerator) Generate(ctx context.Context, opts Options) error {
+	if err := os.MkdirAll(opts.OutputDir, 0755); err != nil {
+		return fmt.Errorf("typescript.Generate: failed to create output dir: %w", err)
+	}
+
+	if g.nativeAvailable() {
+		return g.generateNative(ctx, opts)
+	}
+	if g.npxAvailable() {
+		return g.generateNpx(ctx, opts)
+	}
+	return g.generateDocker(ctx, opts)
+}
+
+func (g *TypeScriptGenerator) nativeAvailable() bool {
+	_, err := exec.LookPath("openapi-typescript-codegen")
+	return err == nil
+}
+
+func (g *TypeScriptGenerator) npxAvailable() bool {
+	_, err := exec.LookPath("npx")
+	return err == nil
+}
+
+func (g *TypeScriptGenerator) generateNative(ctx context.Context, opts Options) error {
+	cmd := exec.CommandContext(ctx, "openapi-typescript-codegen",
+		"--input", opts.SpecPath,
+		"--output", opts.OutputDir,
+		"--name", opts.PackageName,
+	)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func (g *TypeScriptGenerator) generateNpx(ctx context.Context, opts Options) error {
+	cmd := exec.CommandContext(ctx, "npx", "openapi-typescript-codegen",
+		"--input", opts.SpecPath,
+		"--output", opts.OutputDir,
+		"--name", opts.PackageName,
+	)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func (g *TypeScriptGenerator) generateDocker(ctx context.Context, opts Options) error {
+	specDir := filepath.Dir(opts.SpecPath)
+	specName := filepath.Base(opts.SpecPath)
+
+	cmd := exec.CommandContext(ctx, "docker", "run", "--rm",
+		"-v", specDir+":/spec",
+		"-v", opts.OutputDir+":/out",
+		"openapitools/openapi-generator-cli", "generate",
+		"-i", "/spec/"+specName,
+		"-g", "typescript-fetch",
+		"-o", "/out",
+		"--additional-properties=npmName="+opts.PackageName,
+	)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("typescript.generateDocker: %w", err)
+	}
+	return nil
+}

pkg/sdk/generators/typescript_test.go

@@ -0,0 +1,87 @@
+package generators
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+// dockerAvailable checks if docker is available for fallback generation.
+func dockerAvailable() bool {
+	_, err := exec.LookPath("docker")
+	return err == nil
+}
+
+// createTestSpec creates a minimal OpenAPI spec for testing.
+func createTestSpec(t *testing.T, dir string) string {
+	t.Helper()
+	spec := `openapi: "3.0.0"
+info:
+  title: Test API
+  version: "1.0.0"
+paths:
+  /health:
+    get:
+      summary: Health check
+      responses:
+        "200":
+          description: OK
+`
+	specPath := filepath.Join(dir, "openapi.yaml")
+	if err := os.WriteFile(specPath, []byte(spec), 0644); err != nil {
+		t.Fatalf("failed to write test spec: %v", err)
+	}
+	return specPath
+}
+
+func TestTypeScriptGenerator_Good_Available(t *testing.T) {
+	g := NewTypeScriptGenerator()
+
+	// These should not panic
+	lang := g.Language()
+	if lang != "typescript" {
+		t.Errorf("expected language 'typescript', got '%s'", lang)
+	}
+
+	_ = g.Available()
+
+	install := g.Install()
+	if install == "" {
+		t.Error("expected non-empty install instructions")
+	}
+}
+
+func TestTypeScriptGenerator_Good_Generate(t *testing.T) {
+	g := NewTypeScriptGenerator()
+	if !g.Available() && !dockerAvailable() {
+		t.Skip("no TypeScript generator available (neither native nor docker)")
+	}
+
+	// Create temp directories
+	tmpDir := t.TempDir()
+	specPath := createTestSpec(t, tmpDir)
+	outputDir := filepath.Join(tmpDir, "output")
+
+	opts := Options{
+		SpecPath:    specPath,
+		OutputDir:   outputDir,
+		PackageName: "testclient",
+		Version:     "1.0.0",
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	err := g.Generate(ctx, opts)
+	if err != nil {
+		t.Fatalf("Generate failed: %v", err)
+	}
+
+	// Verify output directory was created
+	if _, err := os.Stat(outputDir); os.IsNotExist(err) {
+		t.Error("output directory was not created")
+	}
+}