nut_shell_macros/
lib.rs

1use proc_macro::TokenStream;
2use quote::quote;
3use syn::{Data, DeriveInput, Fields, parse_macro_input};
4
5/// Derives the `AccessLevel` trait for enums.
6///
7/// This macro automatically implements `from_str` and `as_str` methods
8/// for your access level enum, using the variant names as string representations.
9///
10/// # Example
11///
12/// ```ignore
13/// use nut_shell_macros::AccessLevel;
14///
15/// #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, AccessLevel)]
16/// pub enum MyAccessLevel {
17///     Guest = 0,
18///     User = 1,
19///     Admin = 2,
20/// }
21/// ```
22///
23/// This generates:
24///
25/// ```ignore
26/// impl AccessLevel for MyAccessLevel {
27///     fn from_str(s: &str) -> Option<Self> {
28///         match s {
29///             "Guest" => Some(Self::Guest),
30///             "User" => Some(Self::User),
31///             "Admin" => Some(Self::Admin),
32///             _ => None,
33///         }
34///     }
35///
36///     fn as_str(&self) -> &'static str {
37///         match self {
38///             Self::Guest => "Guest",
39///             Self::User => "User",
40///             Self::Admin => "Admin",
41///         }
42///     }
43/// }
44/// ```
45///
46/// # Requirements
47///
48/// - The type must be an enum
49/// - All variants must be unit variants (no fields)
50/// - Variant names will be used as the string representation
51#[proc_macro_derive(AccessLevel)]
52pub fn derive_access_level(input: TokenStream) -> TokenStream {
53    let input = parse_macro_input!(input as DeriveInput);
54
55    let name = &input.ident;
56
57    // Extract enum variants
58    let variants = match &input.data {
59        Data::Enum(data_enum) => &data_enum.variants,
60        _ => {
61            return syn::Error::new_spanned(&input, "AccessLevel can only be derived for enums")
62                .to_compile_error()
63                .into();
64        }
65    };
66
67    // Validate that all variants are unit variants (no fields)
68    for variant in variants {
69        if !matches!(variant.fields, Fields::Unit) {
70            return syn::Error::new_spanned(
71                variant,
72                "AccessLevel can only be derived for enums with unit variants (no fields)",
73            )
74            .to_compile_error()
75            .into();
76        }
77    }
78
79    // Generate match arms for from_str
80    let from_str_arms = variants.iter().map(|variant| {
81        let variant_name = &variant.ident;
82        let variant_str = variant_name.to_string();
83        quote! {
84            #variant_str => Some(Self::#variant_name)
85        }
86    });
87
88    // Generate match arms for as_str
89    let as_str_arms = variants.iter().map(|variant| {
90        let variant_name = &variant.ident;
91        let variant_str = variant_name.to_string();
92        quote! {
93            Self::#variant_name => #variant_str
94        }
95    });
96
97    // Generate the impl block
98    let expanded = quote! {
99        #[automatically_derived]
100        impl ::nut_shell::auth::AccessLevel for #name {
101            fn from_str(s: &str) -> Option<Self> {
102                match s {
103                    #(#from_str_arms,)*
104                    _ => None,
105                }
106            }
107
108            fn as_str(&self) -> &'static str {
109                match self {
110                    #(#as_str_arms,)*
111                }
112            }
113        }
114    };
115
116    TokenStream::from(expanded)
117}
nut_shell_macros/lib.rs

nut_shell_macros/
lib.rs
