package blogposts

import (
	"errors"
	"io/fs"
	"strings"
)

var markdownSuffix = map[string]struct{}{
	"md": {},
}

var ErrUnknownFileType = errors.New("unknown file type, must be markdown")

func NewPostsFromFS(fileSystem fs.FS) ([]Post, error) {
	dir, err := fs.ReadDir(fileSystem, ".")
	if err != nil {
		return nil, err
	}
	var posts []Post
	for _, f := range dir {
		fileName := f.Name()
		if !isMarkdownFile(fileName) {
			return nil, ErrUnknownFileType
		}
		post, err := getPost(fileSystem, fileName)
		if err != nil {
			return nil, err
		}
		posts = append(posts, post)
	}
	return posts, nil
}

func isMarkdownFile(fileName string) bool {
	splitted := strings.Split(fileName, ".")
	_, ok := markdownSuffix[splitted[len(splitted)-1:][0]]
	return ok
}