feat: add replace subcommand with multi-pattern support

internal/replace/README.md

@@ -0,0 +1,13 @@
+# internal/replace
+
+This package hosts the core building blocks for the `renamer replace` command. The modules are
+organized as follows:
+
+- `request.go` — CLI input parsing, validation, and normalization of pattern/replacement data.
+- `parser.go` — Helpers for token handling (quoting, deduplication, reporting).
+- `traversal.go` — Bridges shared traversal utilities with replace-specific filtering logic.
+- `engine.go` — Applies pattern replacements to candidate names and detects conflicts.
+- `preview.go` / `apply.go` — Orchestrate preview output and apply/ledger integration (added later).
+- `summary.go` — Aggregates match counts and conflict details for previews and ledger entries.
+
+Tests will live alongside the package (unit) and in `tests/contract` + `tests/integration`.

internal/replace/apply.go

@@ -0,0 +1,86 @@
+package replace
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"sort"
+
+	"github.com/rogeecn/renamer/internal/history"
+)
+
+// Apply executes the planned operations and records them in the ledger.
+func Apply(ctx context.Context, req *ReplaceRequest, planned []PlannedOperation, summary Summary) (history.Entry, error) {
+	entry := history.Entry{Command: "replace"}
+
+	if len(planned) == 0 {
+		return entry, nil
+	}
+
+	sort.SliceStable(planned, func(i, j int) bool {
+		return planned[i].Result.Candidate.Depth > planned[j].Result.Candidate.Depth
+	})
+
+	done := make([]history.Operation, 0, len(planned))
+
+	revert := func() error {
+		for i := len(done) - 1; i >= 0; i-- {
+			op := done[i]
+			source := filepath.Join(req.WorkingDir, op.To)
+			destination := filepath.Join(req.WorkingDir, op.From)
+			if err := os.Rename(source, destination); err != nil && !errors.Is(err, os.ErrNotExist) {
+				return err
+			}
+		}
+		return nil
+	}
+
+	for _, op := range planned {
+		if err := ctx.Err(); err != nil {
+			_ = revert()
+			return history.Entry{}, err
+		}
+
+		from := op.Result.Candidate.OriginalPath
+		to := op.TargetAbsolute
+
+		if from == to {
+			continue
+		}
+
+		if err := os.Rename(from, to); err != nil {
+			_ = revert()
+			return history.Entry{}, err
+		}
+
+		done = append(done, history.Operation{
+			From: filepath.ToSlash(op.Result.Candidate.RelativePath),
+			To:   filepath.ToSlash(op.TargetRelative),
+		})
+	}
+
+	if len(done) == 0 {
+		return entry, nil
+	}
+
+	entry.Operations = done
+
+	metadataPatterns := make(map[string]int, len(summary.PatternMatches))
+	for pattern, count := range summary.PatternMatches {
+		metadataPatterns[pattern] = count
+	}
+	entry.Metadata = map[string]any{
+		"patterns":        metadataPatterns,
+		"changed":         summary.ChangedCount,
+		"totalCandidates": summary.TotalCandidates,
+	}
+
+	if err := history.Append(req.WorkingDir, entry); err != nil {
+		// Attempt to undo renames if ledger append fails.
+		_ = revert()
+		return history.Entry{}, err
+	}
+
+	return entry, nil
+}

internal/replace/engine.go

@@ -0,0 +1,38 @@
+package replace
+
+import "strings"
+
+// Result captures the outcome of applying patterns to a candidate name.
+type Result struct {
+	Candidate    Candidate
+	ProposedName string
+	Matches      map[string]int
+	Changed      bool
+}
+
+// ApplyPatterns replaces every occurrence of the provided patterns within the candidate's base name.
+func ApplyPatterns(candidate Candidate, patterns []string, replacement string) Result {
+	current := candidate.BaseName
+	matches := make(map[string]int, len(patterns))
+
+	for _, pattern := range patterns {
+		if pattern == "" {
+			continue
+		}
+		count := strings.Count(current, pattern)
+		if count == 0 {
+			continue
+		}
+		current = strings.ReplaceAll(current, pattern, replacement)
+		matches[pattern] += count
+	}
+
+	changed := current != candidate.BaseName
+
+	return Result{
+		Candidate:    candidate,
+		ProposedName: current,
+		Matches:      matches,
+		Changed:      changed,
+	}
+}

internal/replace/parser.go

@@ -0,0 +1,52 @@
+package replace
+
+import (
+	"errors"
+	"strings"
+)
+
+// ParseArgs splits CLI arguments into patterns and replacement while deduplicating patterns.
+type ParseArgsResult struct {
+	Patterns    []string
+	Replacement string
+	Duplicates  []string
+}
+
+// ParseArgs interprets positional arguments for the replace command.
+// The final token is treated as the replacement; all preceding tokens are literal patterns.
+func ParseArgs(args []string) (ParseArgsResult, error) {
+	if len(args) < 2 {
+		return ParseArgsResult{}, errors.New("provide at least one pattern and a replacement value")
+	}
+
+	replacement := args[len(args)-1]
+	patternTokens := args[:len(args)-1]
+
+	seen := make(map[string]struct{}, len(patternTokens))
+	patterns := make([]string, 0, len(patternTokens))
+	duplicates := make([]string, 0)
+
+	for _, token := range patternTokens {
+		trimmed := strings.TrimSpace(token)
+		if trimmed == "" {
+			continue
+		}
+		key := trimmed
+		if _, ok := seen[key]; ok {
+			duplicates = append(duplicates, trimmed)
+			continue
+		}
+		seen[key] = struct{}{}
+		patterns = append(patterns, trimmed)
+	}
+
+	if len(patterns) == 0 {
+		return ParseArgsResult{}, errors.New("at least one non-empty pattern is required before the replacement")
+	}
+
+	return ParseArgsResult{
+		Patterns:    patterns,
+		Replacement: replacement,
+		Duplicates:  duplicates,
+	}, nil
+}

internal/replace/preview.go

@@ -0,0 +1,111 @@
+package replace
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+// PlannedOperation represents a rename that will be executed during apply.
+type PlannedOperation struct {
+	Result         Result
+	TargetRelative string
+	TargetAbsolute string
+}
+
+// Preview computes replacements and writes a human-readable summary to out.
+func Preview(ctx context.Context, req *ReplaceRequest, parseResult ParseArgsResult, out io.Writer) (Summary, []PlannedOperation, error) {
+	summary := NewSummary()
+	for _, dup := range parseResult.Duplicates {
+		summary.AddDuplicate(dup)
+	}
+
+	planned := make([]PlannedOperation, 0)
+	plannedTargets := make(map[string]string) // target rel -> source rel to detect duplicates
+
+	err := TraverseCandidates(ctx, req, func(candidate Candidate) error {
+		res := ApplyPatterns(candidate, parseResult.Patterns, parseResult.Replacement)
+		summary.RecordCandidate(res)
+
+		if !res.Changed {
+			return nil
+		}
+
+		dir := filepath.Dir(candidate.RelativePath)
+		if dir == "." {
+			dir = ""
+		}
+
+		targetRelative := res.ProposedName
+		if dir != "" {
+			targetRelative = filepath.ToSlash(filepath.Join(dir, res.ProposedName))
+		} else {
+			targetRelative = filepath.ToSlash(res.ProposedName)
+		}
+
+		if targetRelative == candidate.RelativePath {
+			return nil
+		}
+
+		if existing, ok := plannedTargets[targetRelative]; ok && existing != candidate.RelativePath {
+			summary.AddConflict(ConflictDetail{
+				OriginalPath: candidate.RelativePath,
+				ProposedPath: targetRelative,
+				Reason:       "duplicate target generated in preview",
+			})
+			return nil
+		}
+
+		targetAbsolute := filepath.Join(req.WorkingDir, filepath.FromSlash(targetRelative))
+		if info, err := os.Stat(targetAbsolute); err == nil {
+			if candidate.OriginalPath != targetAbsolute {
+				// Case-only renames are allowed on case-insensitive filesystems. Compare file identity.
+				if origInfo, origErr := os.Stat(candidate.OriginalPath); origErr == nil {
+					if os.SameFile(info, origInfo) {
+						// Same file—case-only update permitted.
+						goto recordOperation
+					}
+				}
+
+				reason := "target already exists"
+				if info.IsDir() {
+					reason = "target directory already exists"
+				}
+				summary.AddConflict(ConflictDetail{
+					OriginalPath: candidate.RelativePath,
+					ProposedPath: targetRelative,
+					Reason:       reason,
+				})
+				return nil
+			}
+		}
+
+		plannedTargets[targetRelative] = candidate.RelativePath
+
+		if out != nil {
+			fmt.Fprintf(out, "%s -> %s\n", candidate.RelativePath, targetRelative)
+		}
+
+	recordOperation:
+		planned = append(planned, PlannedOperation{
+			Result:         res,
+			TargetRelative: targetRelative,
+			TargetAbsolute: targetAbsolute,
+		})
+
+		return nil
+	})
+	if err != nil {
+		return Summary{}, nil, err
+	}
+
+	if summary.ReplacementWasEmpty(parseResult.Replacement) {
+		if out != nil {
+			fmt.Fprintln(out, "Warning: replacement string is empty; matched patterns will be removed.")
+		}
+	}
+
+	return summary, planned, nil
+}

internal/replace/request.go

@@ -0,0 +1,61 @@
+package replace
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+)
+
+// ReplaceRequest captures all inputs needed to evaluate a replace operation.
+type ReplaceRequest struct {
+	WorkingDir         string
+	Patterns           []string
+	Replacement        string
+	IncludeDirectories bool
+	Recursive          bool
+	IncludeHidden      bool
+	Extensions         []string
+}
+
+// Validate ensures the request is well-formed before preview/apply.
+func (r *ReplaceRequest) Validate() error {
+	if r == nil {
+		return errors.New("replace request cannot be nil")
+	}
+
+	if len(r.Patterns) == 0 {
+		return errors.New("at least one pattern is required")
+	}
+
+	if r.Replacement == "" {
+		// Allow empty replacement but make sure caller has surfaced warnings elsewhere.
+		// No error returned; preview will message accordingly.
+	}
+
+	if r.WorkingDir == "" {
+		cwd, err := os.Getwd()
+		if err != nil {
+			return fmt.Errorf("determine working directory: %w", err)
+		}
+		r.WorkingDir = cwd
+	}
+
+	if !filepath.IsAbs(r.WorkingDir) {
+		abs, err := filepath.Abs(r.WorkingDir)
+		if err != nil {
+			return fmt.Errorf("resolve working directory: %w", err)
+		}
+		r.WorkingDir = abs
+	}
+
+	info, err := os.Stat(r.WorkingDir)
+	if err != nil {
+		return fmt.Errorf("stat working directory: %w", err)
+	}
+	if !info.IsDir() {
+		return fmt.Errorf("working directory %q is not a directory", r.WorkingDir)
+	}
+
+	return nil
+}

internal/replace/summary.go

@@ -0,0 +1,80 @@
+package replace
+
+import "sort"
+
+// ConflictDetail describes a rename that could not be applied.
+type ConflictDetail struct {
+	OriginalPath string
+	ProposedPath string
+	Reason       string
+}
+
+// Summary aggregates metrics for previews, applies, and ledger entries.
+type Summary struct {
+	TotalCandidates  int
+	ChangedCount     int
+	PatternMatches   map[string]int
+	Conflicts        []ConflictDetail
+	Duplicates       []string
+	EmptyReplacement bool
+}
+
+// NewSummary constructs an initialized summary.
+func NewSummary() Summary {
+	return Summary{
+		PatternMatches: make(map[string]int),
+	}
+}
+
+// AddDuplicate records a duplicate pattern supplied by the user.
+func (s *Summary) AddDuplicate(pattern string) {
+	if pattern == "" {
+		return
+	}
+	s.Duplicates = append(s.Duplicates, pattern)
+}
+
+// AddResult incorporates an individual candidate replacement result.
+// RecordCandidate updates aggregate counts for a processed candidate and any matches.
+func (s *Summary) RecordCandidate(res Result) {
+	s.TotalCandidates++
+	if !res.Changed {
+		return
+	}
+	s.ChangedCount++
+	for pattern, count := range res.Matches {
+		s.PatternMatches[pattern] += count
+	}
+}
+
+// AddConflict appends a conflict detail to the summary.
+func (s *Summary) AddConflict(conflict ConflictDetail) {
+	s.Conflicts = append(s.Conflicts, conflict)
+}
+
+// SortedDuplicates returns de-duplicated duplicates list for reporting.
+func (s *Summary) SortedDuplicates() []string {
+	if len(s.Duplicates) == 0 {
+		return nil
+	}
+	copyList := make([]string, 0, len(s.Duplicates))
+	seen := make(map[string]struct{}, len(s.Duplicates))
+	for _, dup := range s.Duplicates {
+		if _, ok := seen[dup]; ok {
+			continue
+		}
+		seen[dup] = struct{}{}
+		copyList = append(copyList, dup)
+	}
+	sort.Strings(copyList)
+	return copyList
+}
+
+// ReplacementWasEmpty records whether the replacement string is empty and returns true.
+func (s *Summary) ReplacementWasEmpty(replacement string) bool {
+	if replacement == "" {
+		s.EmptyReplacement = true
+		return true
+	}
+	return false
+}

internal/replace/traversal.go

@@ -0,0 +1,73 @@
+package replace
+
+import (
+	"context"
+	"io/fs"
+	"path/filepath"
+	"strings"
+
+	"github.com/rogeecn/renamer/internal/traversal"
+)
+
+// Candidate represents a file or directory that may be renamed.
+type Candidate struct {
+	RelativePath string
+	OriginalPath string
+	BaseName     string
+	IsDir        bool
+	Depth        int
+}
+
+// TraverseCandidates walks the working directory according to the request scope and invokes fn for
+// every eligible candidate (files by default, directories when IncludeDirectories is true).
+func TraverseCandidates(ctx context.Context, req *ReplaceRequest, fn func(Candidate) error) error {
+	if err := req.Validate(); err != nil {
+		return err
+	}
+
+	extensions := make(map[string]struct{}, len(req.Extensions))
+	for _, ext := range req.Extensions {
+		lower := strings.ToLower(ext)
+		extensions[lower] = struct{}{}
+	}
+
+	walker := traversal.NewWalker()
+
+	return walker.Walk(
+		req.WorkingDir,
+		req.Recursive,
+		req.IncludeDirectories,
+		req.IncludeHidden,
+		0,
+		func(relPath string, entry fs.DirEntry, depth int) error {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			default:
+			}
+
+			isDir := entry.IsDir()
+			ext := strings.ToLower(filepath.Ext(entry.Name()))
+
+			if !isDir && len(extensions) > 0 {
+				if _, ok := extensions[ext]; !ok {
+					return nil
+				}
+			}
+
+			candidate := Candidate{
+				RelativePath: filepath.ToSlash(relPath),
+				OriginalPath: filepath.Join(req.WorkingDir, relPath),
+				BaseName:     entry.Name(),
+				IsDir:        isDir,
+				Depth:        depth,
+			}
+
+			if candidate.RelativePath == "." {
+				return nil
+			}
+
+			return fn(candidate)
+		},
+	)
+}