feat: add replace subcommand with multi-pattern support

internal/history/history.go

@@ -0,0 +1,122 @@
+package history
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const ledgerFileName = ".renamer"
+
+// Operation records a single rename from source to target.
+type Operation struct {
+	From string `json:"from"`
+	To   string `json:"to"`
+}
+
+// Entry represents a batch of operations appended to the ledger.
+type Entry struct {
+	Timestamp  time.Time      `json:"timestamp"`
+	Command    string         `json:"command"`
+	WorkingDir string         `json:"workingDir"`
+	Operations []Operation    `json:"operations"`
+	Metadata   map[string]any `json:"metadata,omitempty"`
+}
+
+// Append writes a new entry to the ledger in newline-delimited JSON format.
+func Append(workingDir string, entry Entry) error {
+	entry.Timestamp = time.Now().UTC()
+	entry.WorkingDir = workingDir
+
+	path := ledgerPath(workingDir)
+
+	file, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	enc := json.NewEncoder(file)
+	return enc.Encode(entry)
+}
+
+// Undo reverts the most recent ledger entry and removes it from the ledger file.
+func Undo(workingDir string) (Entry, error) {
+	path := ledgerPath(workingDir)
+
+	file, err := os.Open(path)
+	if errors.Is(err, os.ErrNotExist) {
+		return Entry{}, errors.New("no ledger entries available")
+	} else if err != nil {
+		return Entry{}, err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	entries := make([]Entry, 0)
+	for scanner.Scan() {
+		line := scanner.Bytes()
+		if len(line) == 0 {
+			continue
+		}
+		var e Entry
+		if err := json.Unmarshal(append([]byte(nil), line...), &e); err != nil {
+			return Entry{}, err
+		}
+		entries = append(entries, e)
+	}
+	if err := scanner.Err(); err != nil {
+		return Entry{}, err
+	}
+	if len(entries) == 0 {
+		return Entry{}, errors.New("no ledger entries available")
+	}
+
+	last := entries[len(entries)-1]
+
+	// Revert operations in reverse order.
+	for i := len(last.Operations) - 1; i >= 0; i-- {
+		op := last.Operations[i]
+		source := filepath.Join(workingDir, op.To)
+		destination := filepath.Join(workingDir, op.From)
+		if err := os.Rename(source, destination); err != nil {
+			return Entry{}, err
+		}
+	}
+
+	// Rewrite ledger without the last entry.
+	if len(entries) == 1 {
+		if err := os.Remove(path); err != nil && !errors.Is(err, os.ErrNotExist) {
+			return Entry{}, err
+		}
+	} else {
+		tmp := path + ".tmp"
+		output, err := os.OpenFile(tmp, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0o644)
+		if err != nil {
+			return Entry{}, err
+		}
+		enc := json.NewEncoder(output)
+		for _, e := range entries[:len(entries)-1] {
+			if err := enc.Encode(e); err != nil {
+				output.Close()
+				return Entry{}, err
+			}
+		}
+		if err := output.Close(); err != nil {
+			return Entry{}, err
+		}
+		if err := os.Rename(tmp, path); err != nil {
+			return Entry{}, err
+		}
+	}
+
+	return last, nil
+}
+
+// ledgerPath returns the absolute path to the ledger file under workingDir.
+func ledgerPath(workingDir string) string {
+	return filepath.Join(workingDir, ledgerFileName)
+}