package markdown

import (
	"bufio"
	"errors"
	"io"
	"strings"

	"github.com/pelletier/go-toml/v2"
)

func isSeparator(line string) bool {
	line = strings.TrimSpace(line)
	for i := 0; i < len(line); i++ {
		if line[i] != '-' {
			return false
		}
	}
	return len(line) > 2
}

// Meta reads from r to extract TOML frontmatter
func Meta(r io.Reader, out interface{}) error {
	var content strings.Builder
	scanner := bufio.NewScanner(r)
	var seps int
	for scanner.Scan() {
		line := scanner.Text()
		if seps == 0 && content.Len() == 0 && !isSeparator(line) {
			return errors.New("no beginning separator")
		}
		if isSeparator(line) {
			seps++
			if content.Len() == 0 {
				continue
			}
			break
		}
		content.WriteString(line + "\n")
	}
	if seps != 2 {
		return errors.New("no ending separator")
	}

	if content.Len() > 0 {
		return toml.Unmarshal([]byte(content.String()), out)
	}
	return errors.New("no content")
}

// Content skips meta and returns document content
func Content(r io.Reader) (string, error) {
	var s strings.Builder
	scanner := bufio.NewScanner(r)
	var seps int
	for scanner.Scan() {
		if seps < 2 && isSeparator(scanner.Text()) {
			seps++
			continue
		}
		if seps >= 2 {
			s.WriteString(scanner.Text() + "\n")
		}
	}
	return s.String(), nil
}