feat(render): implement PowerShell installer rendering

Add PowerShell() function to render .ps1 installers by injecting
$Env: variables and splicing install.ps1 content. Wire it into
the webid server for .ps1 extension requests.

cmd/webid/bootstrap_test.go

@@ -75,6 +75,33 @@ func TestInstallerFull(t *testing.T) {
 	t.Logf("installer size: %d bytes", len(body))
 }
 
+// TestInstallerPowerShell verifies /api/installers/{pkg}.ps1 returns a PowerShell installer.
+func TestInstallerPowerShell(t *testing.T) {
+	srv, ts := newTestServer(t)
+
+	pkg := "node"
+	if srv.getPackage(pkg) == nil {
+		t.Skipf("package %s not in cache", pkg)
+	}
+
+	code, body := getWithUA(t, ts, "/api/installers/node@stable.ps1", "AMD64/unknown Windows/10.0.19045 msvc")
+	if code != 200 {
+		t.Fatalf("status %d: %s", code, body[:min(len(body), 500)])
+	}
+
+	if !strings.Contains(body, "$Env:WEBI_VERSION") {
+		t.Error("missing $Env:WEBI_VERSION in PS1 installer")
+	}
+	if !strings.Contains(body, "$Env:WEBI_PKG_URL") {
+		t.Error("missing $Env:WEBI_PKG_URL in PS1 installer")
+	}
+	if !strings.Contains(body, "$Env:PKG_NAME") {
+		t.Error("missing $Env:PKG_NAME in PS1 installer")
+	}
+
+	t.Logf("PS1 installer size: %d bytes", len(body))
+}
+
 // TestInstallerSelfHosted verifies selfhosted packages get a script without resolution.
 func TestInstallerSelfHosted(t *testing.T) {
 	_, ts := newTestServer(t)

cmd/webid/main.go

@@ -668,12 +668,6 @@ func (s *server) handleInstaller(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "package name required", http.StatusBadRequest)
 		return
 	}
-	if ext == "ps1" {
-		// TODO: PowerShell installer rendering.
-		http.Error(w, "PowerShell installer not yet implemented", http.StatusNotImplemented)
-		return
-	}
-
 	// Detect platform from User-Agent.
 	ua := uadetect.FromRequest(r)
 	if ua.OS == "" {
@@ -763,11 +757,18 @@ func (s *server) handleInstaller(w http.ResponseWriter, r *http.Request) {
 	p.ReleasesURL = fmt.Sprintf("%s/api/releases/%s@%s.tab?os=%s&arch=%s&libc=%s&formats=tar&pretty=true",
 		baseURL, pkg, tag, p.OS, p.Arch, p.Libc)
 
-	tplPath := filepath.Join(s.installersDir, "_webi", "package-install.tpl.sh")
-	script, err := render.Bash(tplPath, s.installersDir, pkg, p)
-	if err != nil {
-		log.Printf("render %s: %v", pkg, err)
-		http.Error(w, fmt.Sprintf("failed to render installer for %q: %v", pkg, err), http.StatusInternalServerError)
+	var script string
+	var renderErr error
+	if ext == "ps1" {
+		tplPath := filepath.Join(s.installersDir, "_webi", "package-install.tpl.ps1")
+		script, renderErr = render.PowerShell(tplPath, s.installersDir, pkg, p)
+	} else {
+		tplPath := filepath.Join(s.installersDir, "_webi", "package-install.tpl.sh")
+		script, renderErr = render.Bash(tplPath, s.installersDir, pkg, p)
+	}
+	if renderErr != nil {
+		log.Printf("render %s: %v", pkg, renderErr)
+		http.Error(w, fmt.Sprintf("failed to render installer for %q: %v", pkg, renderErr), http.StatusInternalServerError)
 		return
 	}
 

internal/render/render.go

@@ -133,6 +133,74 @@ func Bash(tplPath, installersDir, pkgName string, p Params) (string, error) {
 	return text, nil
 }
 
+// PowerShell renders a complete PowerShell installer script by injecting
+// params into the template and splicing in the package's install.ps1.
+func PowerShell(tplPath, installersDir, pkgName string, p Params) (string, error) {
+	tpl, err := os.ReadFile(tplPath)
+	if err != nil {
+		return "", fmt.Errorf("render: read template: %w", err)
+	}
+
+	installPath := filepath.Join(installersDir, pkgName, "install.ps1")
+	installPs1, err := os.ReadFile(installPath)
+	if err != nil {
+		return "", fmt.Errorf("render: read %s/install.ps1: %w", pkgName, err)
+	}
+
+	text := string(tpl)
+
+	vars := []struct {
+		name  string
+		value string
+	}{
+		{"WEBI_PKG", p.PkgName + "@" + p.Tag},
+		{"WEBI_HOST", p.Host},
+		{"WEBI_VERSION", p.Version},
+		{"WEBI_GIT_TAG", p.GitTag},
+		{"WEBI_PKG_URL", p.PkgURL},
+		{"WEBI_PKG_FILE", p.PkgFile},
+		{"WEBI_PKG_PATHNAME", p.PkgFile},
+		{"PKG_NAME", p.PkgName},
+	}
+
+	for _, v := range vars {
+		text = InjectPSVar(text, v.name, v.value)
+	}
+
+	text = strings.Replace(text, "# {{ installer }}", string(installPs1), 1)
+	text = strings.Replace(text, "{{ installer }}", string(installPs1), 1)
+
+	return text, nil
+}
+
+// InjectPSVar replaces a PowerShell template variable line with its value.
+// Matches lines like:
+//
+//	#$Env:WEBI_VERSION = v12.16.2
+//	$Env:WEBI_HOST = 'https://webinstall.dev'
+func InjectPSVar(text, name, value string) string {
+	p := getPSVarPattern(name)
+	return p.ReplaceAllString(text, "${1}$$Env:"+name+" = '"+sanitizePSValue(value)+"'")
+}
+
+var psVarPatterns = map[string]*regexp.Regexp{}
+
+func getPSVarPattern(name string) *regexp.Regexp {
+	if p, ok := psVarPatterns[name]; ok {
+		return p
+	}
+	// Match: optional leading whitespace, optional #, $Env:NAME, =, rest of line
+	p := regexp.MustCompile(`(?m)^([ \t]*)#?\$Env:` + regexp.QuoteMeta(name) + `\s*=.*$`)
+	psVarPatterns[name] = p
+	return p
+}
+
+// sanitizePSValue escapes single quotes for PowerShell single-quoted strings.
+// In PowerShell, single quotes inside single-quoted strings are doubled: ''
+func sanitizePSValue(s string) string {
+	return strings.ReplaceAll(s, "'", "''")
+}
+
 // varPattern matches shell variable declarations in the template.
 // Matches lines like:
 //