mutate

type MutationConfig struct {
	Rules []MutationRule `json:"mutations" yaml:"mutations"`
}

type MutationResult struct {
	Rule     MutationRule `json:"rule" yaml:"rule"`
	OldValue string       `json:"old_value" yaml:"old_value"`
	NewValue string       `json:"new_value" yaml:"new_value"`
	Applied  bool         `json:"applied" yaml:"applied"`
	Error    string       `json:"error,omitempty" yaml:"error,omitempty"`
	Diff     string       `json:"diff,omitempty" yaml:"diff,omitempty"`
}

type MutationRule struct {
	Path     string `json:"path" yaml:"path"`                           // file path relative to repo root
	Type     string `json:"type" yaml:"type"`                           // jsonPath, yamlPath, tomlKey, regexReplace, exec
	Field    string `json:"field" yaml:"field"`                         // path expression (dot-notation, regex pattern, or shell command)
	Replace  string `json:"replace,omitempty" yaml:"replace,omitempty"` // replacement template (for regex)
	Global   bool   `json:"global,omitempty" yaml:"global,omitempty"`   // replace all matches (regex only)
	RepoRoot string `json:"-" yaml:"-"`                                 // runtime-only: set by engine, not serialized
}

type Mutator interface {
	// Apply performs the mutation on file content, returning updated content and result
	Apply(content []byte, field string, newValue string, rule MutationRule) ([]byte, *MutationResult, error)
}