type HeadingContext interface {
	// Page is the page containing the heading.
	Page() interface{}
	// Level is the level of the header (i.e. 1 for top-level, 2 for sub-level, etc.).
	Level() int
	// Anchor is the HTML id assigned to the heading.
	Anchor() string
	// Text is the rendered (HTML) heading text, excluding the heading marker.
	Text() string
	// PlainText is the unrendered version of Text.
	PlainText() string
}

type HeadingRenderer interface {
	// Render writes the rendered content to w using the data in w.
	RenderHeading(w io.Writer, ctx HeadingContext) error
	identity.Provider
}

type LinkContext interface {
	Page() interface{}
	Destination() string
	Title() string
	Text() string
	PlainText() string
}

type LinkRenderer interface {
	RenderLink(w io.Writer, ctx LinkContext) error
	identity.Provider
}

type Renderers struct {
	LinkRenderer    LinkRenderer
	ImageRenderer   LinkRenderer
	HeadingRenderer HeadingRenderer
}