package mdx
import "github.com/gomarkdown/markdown"
import "github.com/gomarkdown/markdown/html"
import "github.com/gomarkdown/markdown/parser"
import "github.com/d5/tengo/v2"
import "bytes"

func GetModule() tengo.Importable {
	return &tengo.BuiltinModule{Attrs:map[string]tengo.Object{
		"new": &tengo.BuiltinFunction{
			Name: "new",
			Value: func(
				args ...tengo.Object,
			) (tengo.Object, error){
				return MakeDefaultMarkdown(), nil
			},
		},
	}}
}

type Markdown struct {
	tengo.ObjectImpl
	MakeParser func() *parser.Parser
	MakeRenderer func() *html.Renderer
}

func MakeDefaultMarkdown() *Markdown {
	return &Markdown{
		MakeParser: MakeDefaultParser,
		MakeRenderer: MakeDefaultRenderer,
	}
}

func (md *Markdown) TypeName() string {
	return "*Markdown"
}

func (md *Markdown) String() string {
	if md == nil {
		return "<nil>"
	}
	return "&Markdown{...}"
}

func (md *Markdown) Render(
	data []byte,
) ([]byte, error) {
	doc := md.MakeParser().Parse(data)
	rendered := markdown.Render(doc, md.MakeRenderer())
	return rendered, nil
}

func (md *Markdown) CanCall() bool {
	return md != nil
}

func (md *Markdown) Call(
	args ...tengo.Object,
) (tengo.Object, error) {
	var b bytes.Buffer
	for _, arg := range args {
		str, ok := tengo.ToString(arg)
		if !ok {
			return nil, tengo.ErrInvalidArgumentType{
				Name: "v",
				Expected: "stringer",
				Found: arg.TypeName(),
			}
		}
		b.Write([]byte(str))
	}

	rendered, err := md.Render(b.Bytes())
	if err != nil {
		return nil, err
	}

	return tengo.FromInterface(rendered)
}

func MakeDefaultParser() *parser.Parser {
	return parser.NewWithExtensions(
		parser.CommonExtensions | parser.AutoHeadingIDs |
			parser.NoEmptyLineBeforeBlock | parser.Attributes |
			parser.Tables,
	)
}

func MakeDefaultRenderer() *html.Renderer {
	return html.NewRenderer(
		html.RendererOptions{
			Flags: html.CommonFlags | html.HrefTargetBlank,
		},
	)
}