diff

type Config[S any] struct {
	// Usage is the one-line command usage string.
	Usage string
	// ArgsUsage is the positional-arguments usage string.
	ArgsUsage string
	// Description is the long help text.
	Description string
	// ParseDiffArgs parses the raw positional args into two version specs.
	ParseDiffArgs func(args []string) (S, S, error)
	// NewPresenter builds the provider Presenter bound to the two specs.
	NewPresenter func(ctx context.Context, spec1, spec2 S) (Presenter, error)
}

type Options struct {
	ParseJSON bool
	NoPager   bool
	Output    output.Format
}

type Presenter interface {
	// Fetch resolves both specs and loads their entries via the provider usecase.
	Fetch(ctx context.Context) error
	// OldValue and NewValue return the two raw values to be compared.
	OldValue() string
	NewValue() string
	// Labels returns the unified-diff header labels for the old and new sides.
	Labels() (oldLabel, newLabel string)
	// RenderJSON writes the provider JSON output. diff is the pre-computed raw
	// unified diff (empty when the versions are identical).
	RenderJSON(stdout io.Writer, oldValue, newValue string, identical bool, diff string) error
	// Hints writes the provider-specific hints shown when versions are identical.
	Hints(stderr io.Writer)
}

type Runner struct {
	Presenter Presenter
	Options   Options
	Stdout    io.Writer
	Stderr    io.Writer
}