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// arg_util.rs
// *************************************************************************
// * Copyright (C) 2019 Daniel Mueller (deso@posteo.net) *
// * *
// * This program is free software: you can redistribute it and/or modify *
// * it under the terms of the GNU General Public License as published by *
// * the Free Software Foundation, either version 3 of the License, or *
// * (at your option) any later version. *
// * *
// * This program is distributed in the hope that it will be useful, *
// * but WITHOUT ANY WARRANTY; without even the implied warranty of *
// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
// * GNU General Public License for more details. *
// * *
// * You should have received a copy of the GNU General Public License *
// * along with this program. If not, see <http://www.gnu.org/licenses/>. *
// *************************************************************************
macro_rules! count {
($head:ident) => { 1 };
($head:ident, $($tail:ident),*) => {
1 + count!($($tail),*)
}
}
/// A macro for generating an enum with a set of simple (i.e., no
/// parameters) variants and their textual representations.
// TODO: Right now we hard code the derives we create. We may want to
// make this set configurable.
macro_rules! Enum {
( $name:ident, [ $( $var:ident => ($str:expr, $exec:expr), ) *] ) => {
Enum! {$name, [
$( $var => $str, )*
]}
#[allow(unused_qualifications)]
impl $name {
fn execute(
self,
ctx: &mut crate::args::ExecCtx<'_>,
args: ::std::vec::Vec<::std::string::String>,
) -> crate::Result<()> {
match self {
$(
$name::$var => $exec(ctx, args),
)*
}
}
}
};
( $name:ident, [ $( $var:ident => $str:expr, ) *] ) => {
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum $name {
$(
$var,
)*
}
impl $name {
#[allow(unused)]
pub fn all(&self) -> [$name; count!($($var),*) ] {
$name::all_variants()
}
pub fn all_variants() -> [$name; count!($($var),*) ] {
[
$(
$name::$var,
)*
]
}
}
impl ::std::convert::AsRef<str> for $name {
fn as_ref(&self) -> &'static str {
match *self {
$(
$name::$var => $str,
)*
}
}
}
impl ::std::fmt::Display for $name {
fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
write!(f, "{}", self.as_ref())
}
}
impl ::std::str::FromStr for $name {
type Err = ();
fn from_str(s: &str) -> ::std::result::Result<Self, Self::Err> {
match s {
$(
$str => Ok($name::$var),
)*
_ => Err(()),
}
}
}
};
}
/// A macro for formatting the variants of an enum (as created by the
/// Enum!{} macro) ready to be used in a help text. The supplied `fmt`
/// needs to contain the named parameter `{variants}`, which will be
/// replaced with a generated version of the enum's variants.
macro_rules! fmt_enum {
( $enm:ident ) => {{
fmt_enum!($enm.all())
}};
( $all:expr ) => {{
$all
.iter()
.map(::std::convert::AsRef::as_ref)
.collect::<::std::vec::Vec<_>>()
.join("|")
}};
}
/// A macro for generating the help text for a command/subcommand. The
/// argument is the variable representing the command (which in turn is
/// an enum).
/// Note that the name of this variable is embedded into the help text!
macro_rules! cmd_help {
( $cmd:ident ) => {
format!(
concat!("The ", stringify!($cmd), " to execute ({})"),
fmt_enum!($cmd)
)
};
}
#[cfg(test)]
mod tests {
Enum! {Command, [
Var1 => "var1",
Var2 => "2",
Var3 => "crazy",
]}
#[test]
fn all_variants() {
assert_eq!(
Command::all_variants(),
[Command::Var1, Command::Var2, Command::Var3]
)
}
#[test]
fn text_representations() {
assert_eq!(Command::Var1.as_ref(), "var1");
assert_eq!(Command::Var2.as_ref(), "2");
assert_eq!(Command::Var3.as_ref(), "crazy");
}
}
|
