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use nom::{
branch::alt,
bytes::complete::{is_not, tag},
character::complete::{multispace0, multispace1},
combinator::{eof, map, value},
error::ParseError,
sequence::delimited,
sequence::tuple,
Finish, IResult,
};
use std::str::FromStr;
// TODO: It might work well to use clap and parse_from for this particular case
#[derive(Clone)]
pub enum Command {
Whitespace,
Exit,
GitInit(String),
GitUploadPack(String),
GitReceivePack(String),
}
impl FromStr for Command {
// the error must be owned as well
type Err = String;
fn from_str(s: &str) -> Result<Self, Self::Err> {
match command_parser(s).finish() {
Ok((remaining, command)) => {
if remaining.trim().is_empty() {
Ok(command)
} else {
Err(s.trim().to_owned())
}
}
Err(_) => Err(s.trim().to_owned()),
}
}
}
fn command_parser(input: &str) -> IResult<&str, Command> {
alt((
value(Command::Exit, eof),
value(Command::Whitespace, tuple((multispace1, eof))),
value(Command::Exit, ws(tag("exit"))),
map(
ws(tuple((tag("git-init"), multispace1, not_space))),
|(_, _, repo_name)| Command::GitInit(repo_name.to_owned()),
),
map(
ws(tuple((tag("git upload-pack"), multispace1, not_space))),
|(_, _, git_dir)| Command::GitUploadPack(git_dir.to_owned()),
),
map(
ws(tuple((tag("git receive-pack"), multispace1, not_space))),
|(_, _, git_dir)| Command::GitReceivePack(git_dir.to_owned()),
),
))(input)
}
/// A combinator that takes a parser `inner` and produces a parser that also consumes both leading and
/// trailing whitespace, returning the output of `inner`.
fn ws<'a, F, O, E: ParseError<&'a str>>(inner: F) -> impl FnMut(&'a str) -> IResult<&'a str, O, E>
where
F: FnMut(&'a str) -> IResult<&'a str, O, E>,
{
delimited(multispace0, inner, multispace0)
}
fn not_space(s: &str) -> IResult<&str, &str> {
is_not(" \t\r\n")(s)
}
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