Add extension normalization command

internal/extension/summary.go

@@ -0,0 +1,92 @@
+package extension
+
+import (
+	"strings"
+)
+
+// PreviewStatus represents the outcome for a single preview entry.
+type PreviewStatus string
+
+const (
+	PreviewStatusChanged  PreviewStatus = "changed"
+	PreviewStatusNoChange PreviewStatus = "no_change"
+	PreviewStatusSkipped  PreviewStatus = "skipped"
+)
+
+// PreviewEntry captures a single original → proposed path mapping for preview output.
+type PreviewEntry struct {
+	OriginalPath    string
+	ProposedPath    string
+	Status          PreviewStatus
+	SourceExtension string
+}
+
+// Conflict describes a proposed rename that cannot be applied safely.
+type Conflict struct {
+	OriginalPath string
+	ProposedPath string
+	Reason       string
+}
+
+// ExtensionSummary aggregates counts, conflicts, warnings, and ledger metadata.
+type ExtensionSummary struct {
+	TotalCandidates int
+	TotalChanged    int
+	NoChange        int
+
+	PerExtensionCounts map[string]int
+	Conflicts          []Conflict
+	Warnings           []string
+	Entries            []PreviewEntry
+
+	LedgerMetadata map[string]any
+}
+
+// NewSummary constructs an empty ExtensionSummary with initialized maps.
+func NewSummary() *ExtensionSummary {
+	return &ExtensionSummary{
+		PerExtensionCounts: make(map[string]int),
+		LedgerMetadata:     make(map[string]any),
+	}
+}
+
+// RecordEntry appends a preview entry and updates aggregate counters.
+func (s *ExtensionSummary) RecordEntry(entry PreviewEntry) {
+	s.Entries = append(s.Entries, entry)
+	s.TotalCandidates++
+
+	switch entry.Status {
+	case PreviewStatusChanged:
+		s.TotalChanged++
+	case PreviewStatusNoChange:
+		s.NoChange++
+	}
+
+	if entry.SourceExtension != "" {
+		key := strings.ToLower(entry.SourceExtension)
+		s.PerExtensionCounts[key]++
+	}
+}
+
+// AddConflict registers a new conflict encountered during planning.
+func (s *ExtensionSummary) AddConflict(conflict Conflict) {
+	s.Conflicts = append(s.Conflicts, conflict)
+}
+
+// AddWarning ensures warning messages are collected without duplication.
+func (s *ExtensionSummary) AddWarning(message string) {
+	if message == "" {
+		return
+	}
+	for _, existing := range s.Warnings {
+		if existing == message {
+			return
+		}
+	}
+	s.Warnings = append(s.Warnings, message)
+}
+
+// HasConflicts reports whether any blocking conflicts were recorded.
+func (s *ExtensionSummary) HasConflicts() bool {
+	return len(s.Conflicts) > 0
+}