feat(platform): add textblock helper for idempotent config-file blocks

internal/platform/textblock_test.go

@@ -0,0 +1,88 @@
+package platform
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestEnsureBlockInsertsIntoMissingFile(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "rc")
+	if err := EnsureBlock(p, "archduino", "export FOO=1"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := os.ReadFile(p)
+	want := "# >>> archduino >>>\nexport FOO=1\n# <<< archduino <<<\n"
+	if string(got) != want {
+		t.Fatalf("got %q want %q", got, want)
+	}
+}
+
+func TestEnsureBlockReplacesExisting(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "rc")
+	initial := "alias ll='ls -l'\n# >>> archduino >>>\nold content\n# <<< archduino <<<\necho tail\n"
+	if err := os.WriteFile(p, []byte(initial), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := EnsureBlock(p, "archduino", "new content"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := os.ReadFile(p)
+	want := "alias ll='ls -l'\n# >>> archduino >>>\nnew content\n# <<< archduino <<<\necho tail\n"
+	if string(got) != want {
+		t.Fatalf("got %q want %q", got, want)
+	}
+}
+
+func TestEnsureBlockIdempotent(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "rc")
+	_ = EnsureBlock(p, "a", "x")
+	before, _ := os.ReadFile(p)
+	_ = EnsureBlock(p, "a", "x")
+	after, _ := os.ReadFile(p)
+	if string(before) != string(after) {
+		t.Fatalf("not idempotent: %q vs %q", before, after)
+	}
+}
+
+func TestHasBlockTrueFalse(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "rc")
+	has, err := HasBlock(p, "a")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if has {
+		t.Fatal("missing file should report has=false")
+	}
+	_ = os.WriteFile(p, []byte("no blocks here\n"), 0o644)
+	has, _ = HasBlock(p, "a")
+	if has {
+		t.Fatal("unblocked file should report has=false")
+	}
+	_ = EnsureBlock(p, "a", "x")
+	has, _ = HasBlock(p, "a")
+	if !has {
+		t.Fatal("blocked file should report has=true")
+	}
+}
+
+func TestRemoveBlock(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "rc")
+	_ = os.WriteFile(p, []byte("head\n# >>> a >>>\nmid\n# <<< a <<<\ntail\n"), 0o644)
+	if err := RemoveBlock(p, "a"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := os.ReadFile(p)
+	if strings.Contains(string(got), ">>> a >>>") {
+		t.Fatalf("block not removed: %q", got)
+	}
+	if !strings.Contains(string(got), "head") || !strings.Contains(string(got), "tail") {
+		t.Fatalf("surrounding content lost: %q", got)
+	}
+}