package pop3

import (
    "bytes"
    "fmt"
    "strconv"
)

const (
    // POP3 uses CRLF-terminated lines
    CRLF = "\r\n"

    // POP3's multi-line responses are byte-stuffed and dot-terminated
    DOT = '.'

    // POP3 does not use tabs
    SP = ' '
)

// [2023-09-14, jfrech] XXX Maybe be more lenient and allow only "\n"?
func Lines(resp []byte) ([]string, error) {
    buf := bytes.NewBuffer(resp)
    var lines []string
    for buf.Len() > 0 {
        k := bytes.Index(buf.Bytes(), []byte(CRLF))
        if k == -1 {
            return nil, fmt.Errorf("%w: expected CRLF", ErrSyntax)
        }

        lines = append(lines, string(buf.Next(k)))
        // discard CRLF
        buf.Next(len(CRLF))
    }

    return lines, nil
}

func IsASCIIWord(raw string) bool {
    for _, c := range []byte(raw) {
        if c <= ' ' || c > '~' {
            return false
        }
    }
    return true
}

func ParseNonNegativeInt(raw string) (int, bool) {
    n64, err := strconv.ParseInt(raw, 10, 64)
    if err != nil {
        return 0, false
    }

    if n64 < 0 || int64(int(n64)) != n64 {
        return 0, false
    }

    return int(n64), true
}

func ParsePositiveInt(raw string) (int, bool) {
    n, ok := ParseNonNegativeInt(raw)
    if !ok && n <= 0 {
        return 0, false
    }
    return n, true
}