cargo-kconfig 0.0.4

/*
 Cargo KConfig - KConfig parser
 Copyright (C) 2022  Sjoerd van Leent

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Copyright Notice: GPLv2

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
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This program is distributed in the hope that it will be useful,
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GNU General Public License for more details.

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this software and associated documentation files (the “Software”), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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*/

use proc_macro::{Delimiter, Group, Ident, TokenStream, TokenTree};

use super::{
    eval::Eval,
    util::{is_comma, must_be_assign, must_be_comma, next_token},
};

/// There are four ways the run can be invoked:
///
/// <config-expression>, <rust-expression>
/// <config-expression>, <success-expression>, <failure-expression>
/// tag = <name>, <config-expression>, <rust-expression>
/// tag = <name>, <config-expression>, <success-expression>, <failure-expression>
pub(crate) fn run(input: TokenStream) -> TokenStream {
    let mut iter = input.into_iter();
    let tt = next_token(&mut iter);

    let eval_success = eval(tt, &mut iter);

    let mut result_ok = Vec::<TokenTree>::new();
    let mut result_nok = Vec::<TokenTree>::new();

    let mut first_arm = true;

    loop {
        let next_token = iter.next();
        match next_token {
            Some(tt) => match tt {
                TokenTree::Punct(punct) => match punct.as_char() {
                    ',' => match first_arm {
                        true => first_arm = false,
                        false => panic!("Tertiary evaluation arm not supported"),
                    },
                    _ => match first_arm {
                        true => result_ok.push(TokenTree::Punct(punct)),
                        false => result_nok.push(TokenTree::Punct(punct)),
                    },
                },
                _ => match first_arm {
                    true => result_ok.push(tt),
                    false => result_nok.push(tt),
                },
            },
            None => break,
        }
    }

    match eval_success {
        true => result_ok.into_iter().collect(),
        false => result_nok.into_iter().collect(),
    }
}

fn eval(mut tt: TokenTree, iter: &mut proc_macro::token_stream::IntoIter) -> bool {
    match tt {
        // if the tokentree starts with a group, and state
        // equals start, then this is a tag-less invocation
        TokenTree::Group(g) => {
            let eval = Eval::new_tagged("default", &g);
            let result = eval.eval().as_bool();
            tt = next_token(iter);
            must_be_comma(&tt);
            if !result {
                return false;
            }
        }

        // If the tokentree starts with an identifier, then this
        // can be a tagged expression, only if the identifier
        // equals "tag"
        TokenTree::Ident(i) => {
            let mut v = Vec::<TokenTree>::new();

            let tag_name = if i.to_string() == "tag" {
                tt = next_token(iter);

                must_be_assign(&tt);

                tt = next_token(iter);

                let tag_name = match tt {
                    TokenTree::Ident(i) => i.to_string(),
                    _ => panic!("Expected identifier with tag name"),
                };

                tt = next_token(iter);
                must_be_comma(&tt);

                tag_name
            } else {
                let backup = Ident::new(&i.to_string(), i.span());
                v.push(TokenTree::Ident(backup));
                "default".to_owned()
            };

            loop {
                tt = next_token(iter);
                if is_comma(&tt) {
                    break;
                }
                v.push(tt);
            }

            let mut s = TokenStream::new();
            s.extend(v.into_iter());

            let group = Group::new(Delimiter::Parenthesis, s);
            let eval = Eval::new_tagged(&tag_name, &group);
            if !eval.eval().as_bool() {
                return false;
            }
        }

        TokenTree::Punct(_) | TokenTree::Literal(_) => {
            if is_comma(&tt) {
                panic!("Expected tag assignment or expression, not comma")
            }
            let mut v = Vec::<TokenTree>::new();
            v.push(tt);
            loop {
                tt = next_token(iter);
                if is_comma(&tt) {
                    break;
                }
                v.push(tt);
            }

            let mut s = TokenStream::new();
            s.extend(v.into_iter());

            let group = Group::new(Delimiter::Parenthesis, s);
            let eval = Eval::new_tagged("default", &group);
            if !eval.eval().as_bool() {
                return false;
            }
        }
    }
    true
}