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//! Postfix [XFORWARD] SMTP extension parser
//!
//! [XFORWARD]: http://www.postfix.org/XFORWARD_README.html

use nom::branch::alt;
use nom::bytes::complete::{tag, tag_no_case};
use nom::combinator::{opt, map};
use nom::multi::{many1};
use nom::sequence::{delimited, preceded, separated_pair};

use crate::rfc5234::{crlf, wsp};
use crate::rfc3461::xtext;
use crate::util::*;

/// XFORWARD parameter name and value.
///
/// `"[UNAVAILABLE]"` is represented with a value of `None`.
#[derive(Clone, Debug)]
pub struct Param(pub &'static str, pub Option<String>);

fn command_name(input: &[u8]) -> NomResult<&'static str> {
    alt((map(tag_no_case("addr"), |_| "addr"),
         map(tag_no_case("helo"), |_| "helo"),
         map(tag_no_case("ident"), |_| "ident"),
         map(tag_no_case("name"), |_| "name"),
         map(tag_no_case("port"), |_| "port"),
         map(tag_no_case("proto"), |_| "proto"),
         map(tag_no_case("source"), |_| "source")))(input)
}

fn unavailable(input: &[u8]) -> NomResult<Option<String>> {
    map(tag_no_case("[unavailable]"), |_| None)(input)
}

fn value(input: &[u8]) -> NomResult<Option<String>> {
    alt((unavailable, map(xtext, |x| Some(ascii_to_string(x).into()))))(input)
}

fn param(input: &[u8]) -> NomResult<Param> {
    map(separated_pair(command_name, tag("="), value),
        |(c, v)| Param(c, v))(input)
}

/// Parse a XFORWARD b`"attr1=value attr2=value"` string.
///
/// Returns a vector of [`Param`].
///
/// The parameter names must be valid and are normalized to
/// lowercase. The values are xtext decoded and a value of
/// `[UNAVAILABLE]` is translated to `None`. No other validation is
/// done.
pub fn xforward_params(input: &[u8]) -> NomResult<Vec<Param>> {
    fold_prefix0(preceded(opt(many1(wsp)), param),
                 preceded(many1(wsp), param))(input)
}

pub fn command(input: &[u8]) -> NomResult<Vec<Param>> {
    delimited(tag_no_case("XFORWARD "), xforward_params, crlf)(input)
}