package gophermap

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"io"
	"strconv"

	sr "tildegit.org/tjp/sliderule"
	"tildegit.org/tjp/sliderule/gopher"
)

// Parse reads a gophermap document from a reader.
func Parse(input io.Reader) (gopher.MapDocument, error) {
	rdr := bufio.NewReader(input)
	doc := gopher.MapDocument{}

	for num := 1; ; num += 1 {
		line, err := rdr.ReadBytes('\n')
		isEOF := errors.Is(err, io.EOF)
		if err != nil && !isEOF {
			return nil, err
		}

		if len(line) > 2 && !bytes.Equal(line, []byte(".\r\n")) {
			if line[len(line)-2] != '\r' || line[len(line)-1] != '\n' {
				return nil, InvalidLine(num)
			}

			item := gopher.MapItem{Type: sr.Status(line[0])}

			spl := bytes.Split(line[1:len(line)-2], []byte{'\t'})
			if item.Type != gopher.InfoMessageType && len(spl) != 4 {
				return nil, InvalidLine(num)
			}
			item.Display = string(spl[0])

			if len(spl) > 1 {
				item.Selector = string(spl[1])
			}
			if len(spl) > 2 {
				item.Hostname = string(spl[2])
			}
			if len(spl) > 3 {
				item.Port = string(spl[3])
				if _, err = strconv.Atoi(item.Port); err != nil {
					return nil, InvalidLine(num)
				}
			}

			doc = append(doc, item)
		}

		if isEOF {
			break
		}
	}

	return doc, nil
}

// InvalidLine is returned from Parse when the reader contains a line which is invalid gophermap.
type InvalidLine int

// Error implements the error interface.
func (il InvalidLine) Error() string {
	return fmt.Sprintf("Invalid gophermap on line %d.", il)
}