state-shift 2.0.0

Macros for implementing Type-State-Pattern on your structs and methods
Documentation 
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use proc_macro::TokenTree;
use syn::{punctuated::Punctuated, Attribute, Ident, Token};

/// Helper function to find and remove an attribute by name
fn find_and_remove_attr(attrs: &mut Vec<Attribute>, attr_name: &str) -> Option<Attribute> {
    let pos = attrs
        .iter()
        .position(|attr| attr.path().is_ident(attr_name))?;
    Some(attrs.remove(pos))
}

/// Helper function to modify identifiers based on single-letter or prefixed names
fn modify_args_with_struct_name(
    args: Punctuated<Ident, Token![,]>,
    struct_name: &Ident,
) -> Punctuated<Ident, Token![,]> {
    args.into_iter()
        .map(|ident| {
            if is_single_letter(&ident) {
                ident
            } else {
                Ident::new(&format!("{}{}", struct_name, ident), ident.span())
            }
        })
        .collect()
}

pub fn extract_macro_args(
    attrs: &mut Vec<Attribute>,
    macro_name: &str,
    struct_name: &Ident,
) -> Option<Punctuated<Ident, Token![,]>> {
    let attr = find_and_remove_attr(attrs, macro_name)?;
    let args: Punctuated<Ident, Token![,]> =
        attr.parse_args_with(Punctuated::parse_terminated).ok()?;
    Some(modify_args_with_struct_name(args, struct_name))
}

pub fn is_single_letter(ident: &Ident) -> bool {
    ident.to_string().len() == 1
}

pub fn extract_idents_from_group(
    token: &TokenTree,
    struct_name: &Ident,
    error_msg: &str,
) -> Vec<Ident> {
    match token {
        proc_macro::TokenTree::Group(group) => group
            .stream()
            .into_iter()
            .filter_map(|tt| {
                if let proc_macro::TokenTree::Ident(ident) = tt {
                    Some(Ident::new(
                        &format!("{}{}", struct_name, ident),
                        ident.span().into(),
                    ))
                } else {
                    None
                }
            })
            .collect(),
        _ => panic!("{}", error_msg),
    }
}