Add extension normalization command

internal/extension/engine.go

@@ -0,0 +1,164 @@
+package extension
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"path/filepath"
+	"strings"
+
+	"github.com/rogeecn/renamer/internal/traversal"
+)
+
+// PlannedRename describes a filesystem rename operation produced during planning.
+type PlannedRename struct {
+	OriginalRelative string
+	OriginalAbsolute string
+	ProposedRelative string
+	ProposedAbsolute string
+	SourceExtension  string
+	IsDir            bool
+	Depth            int
+}
+
+// PlanResult captures the preview summary and concrete operations required for apply.
+type PlanResult struct {
+	Summary    *ExtensionSummary
+	Operations []PlannedRename
+}
+
+// BuildPlan walks the scoped filesystem, collecting preview entries and rename operations.
+func BuildPlan(ctx context.Context, req *ExtensionRequest) (*PlanResult, error) {
+	if req == nil {
+		return nil, errors.New("extension request cannot be nil")
+	}
+	if err := req.Normalize(); err != nil {
+		return nil, err
+	}
+
+	summary := NewSummary()
+	operations := make([]PlannedRename, 0)
+	detector := newConflictDetector()
+
+	targetExt := NormalizeTargetExtension(req.TargetExtension)
+	targetCanonical := CanonicalExtension(targetExt)
+
+	sourceSet := make(map[string]struct{}, len(req.SourceExtensions))
+	for _, source := range req.SourceExtensions {
+		sourceSet[CanonicalExtension(source)] = struct{}{}
+	}
+
+	// Include the target extension so preview surfaces existing matches as no-ops.
+	matchable := make(map[string]struct{}, len(sourceSet)+1)
+	for ext := range sourceSet {
+		matchable[ext] = struct{}{}
+	}
+	matchable[targetCanonical] = struct{}{}
+
+	filterSet := make(map[string]struct{}, len(req.ExtensionFilter))
+	for _, filter := range req.ExtensionFilter {
+		filterSet[CanonicalExtension(filter)] = struct{}{}
+	}
+
+	walker := traversal.NewWalker()
+
+	err := walker.Walk(
+		req.WorkingDir,
+		req.Recursive,
+		req.IncludeDirs,
+		req.IncludeHidden,
+		0,
+		func(relPath string, entry fs.DirEntry, depth int) error {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			default:
+			}
+
+			if relPath == "." {
+				return nil
+			}
+
+			isDir := entry.IsDir()
+			if isDir && !req.IncludeDirs {
+				return nil
+			}
+
+			name := entry.Name()
+			rawExt := strings.TrimSpace(filepath.Ext(name))
+			canonicalExt := CanonicalExtension(rawExt)
+
+			if !isDir && len(filterSet) > 0 {
+				if _, ok := filterSet[canonicalExt]; !ok {
+					return nil
+				}
+			}
+
+			if _, ok := matchable[canonicalExt]; !ok {
+				return nil
+			}
+
+			relative := filepath.ToSlash(relPath)
+			originalAbsolute := filepath.Join(req.WorkingDir, filepath.FromSlash(relative))
+
+			status := PreviewStatusChanged
+			targetRelative := relative
+			targetAbsolute := originalAbsolute
+
+			if canonicalExt == targetCanonical && rawExt == targetExt {
+				status = PreviewStatusNoChange
+			}
+
+			if status == PreviewStatusChanged {
+				base := strings.TrimSuffix(name, rawExt)
+				targetName := base + targetExt
+				dir := filepath.Dir(relative)
+				if dir == "." {
+					dir = ""
+				}
+				if dir == "" {
+					targetRelative = filepath.ToSlash(targetName)
+				} else {
+					targetRelative = filepath.ToSlash(filepath.Join(dir, targetName))
+				}
+				targetAbsolute = filepath.Join(req.WorkingDir, filepath.FromSlash(targetRelative))
+
+				allowed, err := detector.evaluateTarget(summary, relative, targetRelative, originalAbsolute, targetAbsolute)
+				if err != nil {
+					return err
+				}
+				if allowed {
+					operations = append(operations, PlannedRename{
+						OriginalRelative: relative,
+						OriginalAbsolute: originalAbsolute,
+						ProposedRelative: targetRelative,
+						ProposedAbsolute: targetAbsolute,
+						SourceExtension:  rawExt,
+						IsDir:            isDir,
+						Depth:            depth,
+					})
+				} else {
+					status = PreviewStatusSkipped
+				}
+			}
+
+			entrySummary := PreviewEntry{
+				OriginalPath:    relative,
+				ProposedPath:    targetRelative,
+				Status:          status,
+				SourceExtension: rawExt,
+			}
+			summary.RecordEntry(entrySummary)
+
+			return nil
+		},
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	return &PlanResult{
+		Summary:    summary,
+		Operations: operations,
+	}, nil
+}