Add regex command implementation

internal/regex/apply.go

@@ -0,0 +1,92 @@
+package regex
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+
+	"github.com/rogeecn/renamer/internal/history"
+)
+
+// Apply executes the planned regex renames and writes a ledger entry.
+func Apply(ctx context.Context, req Request, planned []PlannedRename, summary Summary) (history.Entry, error) {
+	reqCopy := req
+	if err := reqCopy.Validate(); err != nil {
+		return history.Entry{}, err
+	}
+
+	entry := history.Entry{Command: "regex"}
+
+	if len(planned) == 0 {
+		return entry, nil
+	}
+
+	sort.SliceStable(planned, func(i, j int) bool {
+		return planned[i].Depth > planned[j].Depth
+	})
+
+	done := make([]history.Operation, 0, len(planned))
+	groupsMeta := make(map[string][]string, len(planned))
+
+	revert := func() error {
+		for i := len(done) - 1; i >= 0; i-- {
+			op := done[i]
+			source := filepath.Join(reqCopy.WorkingDir, filepath.FromSlash(op.To))
+			destination := filepath.Join(reqCopy.WorkingDir, filepath.FromSlash(op.From))
+			if err := os.Rename(source, destination); err != nil && !errors.Is(err, os.ErrNotExist) {
+				return err
+			}
+		}
+		return nil
+	}
+
+	for _, plan := range planned {
+		if err := ctx.Err(); err != nil {
+			_ = revert()
+			return history.Entry{}, err
+		}
+
+		if err := os.MkdirAll(filepath.Dir(plan.TargetAbsolute), 0o755); err != nil {
+			_ = revert()
+			return history.Entry{}, fmt.Errorf("prepare target directory: %w", err)
+		}
+
+		if err := os.Rename(plan.SourceAbsolute, plan.TargetAbsolute); err != nil {
+			_ = revert()
+			return history.Entry{}, err
+		}
+
+		relFrom := filepath.ToSlash(plan.SourceRelative)
+		relTo := filepath.ToSlash(plan.TargetRelative)
+		done = append(done, history.Operation{From: relFrom, To: relTo})
+		if len(plan.MatchGroups) > 0 {
+			groupsMeta[relFrom] = append([]string(nil), plan.MatchGroups...)
+		}
+	}
+
+	if len(done) == 0 {
+		return entry, nil
+	}
+
+	entry.Operations = done
+	metadata := map[string]any{
+		"pattern":  reqCopy.Pattern,
+		"template": reqCopy.Template,
+		"matched":  summary.Matched,
+		"changed":  summary.Changed,
+	}
+	if len(groupsMeta) > 0 {
+		metadata["matchGroups"] = groupsMeta
+	}
+	entry.Metadata = metadata
+
+	if err := history.Append(reqCopy.WorkingDir, entry); err != nil {
+		_ = revert()
+		return history.Entry{}, err
+	}
+
+	return entry, nil
+}