package convert

import (
	"io"
	"os"

	"github.com/gomarkdown/markdown"
	"github.com/gomarkdown/markdown/html"
	"github.com/gomarkdown/markdown/parser"
)

// This function takes a Markdown document and returns an HTML document.
func MdToHTML(md []byte) ([]byte, error) {
	// create parser with extensions
	extensions := parser.CommonExtensions | parser.AutoHeadingIDs | parser.NoEmptyLineBeforeBlock
	p := parser.NewWithExtensions(extensions)
	doc := p.Parse(md)

	// build HTML renderer
	htmlFlags := html.CommonFlags | html.HrefTargetBlank
	opts := html.RendererOptions{Flags: htmlFlags}
	renderer := html.NewRenderer(opts)

	return markdown.Render(doc, renderer), nil
}

// WriteFile writes a given byte array to the given path.
func WriteFile(b []byte, p string) error {
	f, err := os.Create(p)
	if err != nil {
		return err
	}
	_, err = f.Write(b)
	defer f.Close()
	if err != nil {
		return err
	}
	return nil
}

// ReadFile reads a byte array from a given path.
func ReadFile(p string) ([]byte, error) {
	f, err := os.Open(p)
	if err != nil {
		return nil, err
	}
	var result []byte
	buf := make([]byte, 1024)
	for {
		n, err := f.Read(buf)
		// check for a non EOF error
		if err != nil && err != io.EOF {
			return nil, err
		}
		// n==0 when there are no chunks left to read
		if n == 0 {
			defer f.Close()
			break
		}
		result = append(result, buf[:n]...)
	}
	return result, nil
}

func ConvertFile(in string, out string) error {
	md, err := ReadFile(in)
	if err != nil {
		return err
	}
	html, err := MdToHTML(md)
	if err != nil {
		return err
	}
	err = WriteFile(html, out)
	return err
}