package markdown

import "fmt"
import "bytes"
import "strings"
import "html/template"
import "github.com/yuin/goldmark"
import "github.com/yuin/goldmark/parser"
import "git.tebibyte.media/sashakoshka/step"

var _ step.FuncProvider = new(Provider)

// Provider provides Markdown functions.
type Provider struct {
	// Options contains parse options that are passed to the converter.
	Options []parser.ParseOption
}

// FuncMap fulfills the step.FuncProvider interface.
func (this *Provider) FuncMap () template.FuncMap {
	stat := &state {
		options: this.Options,
	}
	return template.FuncMap {
		"markdown": stat.funcMarkdown,
	}
}

type state struct {
	options []parser.ParseOption
}

func (this *state) funcMarkdown (input any) (template.HTML, error) {
	builder := strings.Builder { }
	err := goldmark.Convert(toBytes(input), &builder, this.options...)
	if err != nil { return "", nil }
	return template.HTML(builder.String()), nil
}

func toBytes (data any) []byte {
	switch data := data.(type) {
	case []byte:        return data
	case string:        return []byte(data)
	case template.HTML: return []byte(data)
	default:
		buffer := bytes.Buffer { }
		fmt.Fprint(&buffer, data)
		return buffer.Bytes()
	}
}