package addressparsing

import "strings"

// FixUnquotedMarkers quotes unquoted "<>,;:@".
//
// Deprecated: Doesn't seem to be useful: `x @y .com` -> `x "@y" ".com"` != `"x@y.com"`
func FixUnquotedMarkers(s string) string {
    const markers = "<>,;:@"

    b := new(strings.Builder)
    FmapSplitByWhitespaceQuotedText(s, func(z string) {
        switch {
        case IsWS(z[0]) || z[0] == '"':
            b.WriteString(z)
        case strings.IndexAny(z, markers) == -1:
            b.WriteString(z)
        default:
            b.WriteString(QuoteString(z))
        }
    })

    return b.String()
}

// BUG(jfrech): 2024-06-12: This function should be called "Quote".
func QuoteString(s string) string {
    var n int
    for _, c := range []byte(s) {
        if c == '"' || c == '\\' {
            n++
        }
    }
    n += len(s)
    if n < 0 {
        panic("len overflow")
    }
    n += 2
    if n < 0 {
        panic("len overflow")
    }

    buf := make([]byte, n)
    buf[0] = '"'
    buf[len(buf)-1] = '"'
    b := buf[1:len(buf)-1]

    // fast-path: nothing interior to quote
    if n == len(s)+2 {
        copy(b, s)
        return string(buf)
    }

    for _, c := range []byte(s) {
        if c == '"' || c == '\\' {
            b[0] = '\\'
            b = b[1:]
        }
        b[0] = c
        b = b[1:]
    }
    if len(b) != 0 {
        panic("unreachable")
    }

    return string(buf)
}

// FmapSplitByWhitespaceQuotedText calls f with successive non-zero slices
// out of s which are split by whitespace/quote/text edges.
func FmapSplitByWhitespaceQuotedText(s string, f func(z string)) {
    for len(s) > 0 {
        k := func() (k int) {
            switch {
            case s[0] == '"':
loop:
                for k = 1; k < len(s); k++ {
                    switch s[k] {
                    case '"':
                        break loop
                    case '\\':
                        k++
                    }
                }

                return min(len(s), k+1)

            case IsWS(s[0]):
                for k < len(s) && IsWS(s[k]) {
                    k++
                }

                return k

            default:
                for k < len(s) && !IsWS(s[k]) && s[k] != '"' {
                    k++
                }

                return k
            }
        }()

        if k <= 0 {
            panic("unreachable")
        }
        f(s[:k])
        s = s[k:]
    }
}

func QuoteIfNecessary(s string) string {
    if strings.IndexAny(s, "\"\\" + "<>:;," + "@" + "\r\n\t " + "()") == -1 {
        return s
    }

    return QuoteString(s)
}