feat: add replace subcommand with multi-pattern support

tests/contract/replace_command_test.go

@@ -0,0 +1,102 @@
+package contract
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/rogeecn/renamer/internal/replace"
+)
+
+func TestPreviewSummaryCounts(t *testing.T) {
+	tmp := t.TempDir()
+	createFile(t, filepath.Join(tmp, "draft.txt"))
+	createFile(t, filepath.Join(tmp, "Draft.md"))
+	createFile(t, filepath.Join(tmp, "notes", "DRAFT.log"))
+
+	args := []string{"draft", "Draft", "DRAFT", "final"}
+	parsed, err := replace.ParseArgs(args)
+	if err != nil {
+		t.Fatalf("ParseArgs error: %v", err)
+	}
+
+	req := &replace.ReplaceRequest{
+		WorkingDir:  tmp,
+		Patterns:    parsed.Patterns,
+		Replacement: parsed.Replacement,
+		Recursive:   true,
+	}
+
+	var buf bytes.Buffer
+	summary, planned, err := replace.Preview(context.Background(), req, parsed, &buf)
+	if err != nil {
+		t.Fatalf("Preview error: %v", err)
+	}
+
+	if summary.TotalCandidates == 0 {
+		t.Fatalf("expected candidates to be processed")
+	}
+
+	if summary.ChangedCount != len(planned) {
+		t.Fatalf("changed count mismatch: %d vs %d", summary.ChangedCount, len(planned))
+	}
+
+	for _, pattern := range []string{"draft", "Draft", "DRAFT"} {
+		if summary.PatternMatches[pattern] == 0 {
+			t.Fatalf("expected matches recorded for %s", pattern)
+		}
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "draft.txt -> final.txt") {
+		t.Fatalf("expected preview output to list replacements, got: %s", output)
+	}
+
+	if summary.ReplacementWasEmpty(parsed.Replacement) {
+		t.Fatalf("replacement should not be empty warning for this test")
+	}
+}
+
+func TestPreviewWarnsOnEmptyReplacement(t *testing.T) {
+	tmp := t.TempDir()
+	createFile(t, filepath.Join(tmp, "foo.txt"))
+
+	args := []string{"foo", ""}
+	parsed, err := replace.ParseArgs(args)
+	if err != nil {
+		t.Fatalf("ParseArgs error: %v", err)
+	}
+
+	req := &replace.ReplaceRequest{
+		WorkingDir:  tmp,
+		Patterns:    parsed.Patterns,
+		Replacement: parsed.Replacement,
+	}
+
+	var buf bytes.Buffer
+	summary, _, err := replace.Preview(context.Background(), req, parsed, &buf)
+	if err != nil {
+		t.Fatalf("Preview error: %v", err)
+	}
+
+	if !summary.EmptyReplacement {
+		t.Fatalf("expected empty replacement flag to be set")
+	}
+
+	if !strings.Contains(buf.String(), "Warning: replacement string is empty") {
+		t.Fatalf("expected empty replacement warning in preview output")
+	}
+}
+
+func createFile(t *testing.T, path string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("mkdir %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, []byte("test"), 0o644); err != nil {
+		t.Fatalf("write file %s: %v", path, err)
+	}
+}