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mod structure;

use proc_macro::TokenStream;
use quote::ToTokens;
use structure::StructureInput;
use syn::parse_macro_input;

#[macro_use]
extern crate quote;
extern crate syn;

extern crate proc_macro2;

/// A derivable macro for declaring a builder pattern.
///
/// ## Examples
///
/// ```rust
/// use builder_pattern::*;
///
/// #[derive(Builder)]
/// struct Person {
///     name: String,
///     age: i32,
///     #[default(Gender::Nonbinary)]
///     gender: Gender,
/// }
///
/// let p1 = Person::new().name(String::from("Joe")).age(27).build();
/// // Orders does not matter.
/// let p2 = Person::new().age(32).name(String::from("Jack")).gender(Gender::Male).build();
/// // `name` field required - Compilation error.
/// let p3 = Person::new().age(15).build();
/// ```
///
/// It considers all fields without `default` attribute as required.
/// If the attribute is provided, the expression in the parantheses is evaluated as a default value.
///
/// When the insuficient number of arguments is provided, the compilation will fail.
#[proc_macro_derive(Builder, attributes(default))]
pub fn derive_builder(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as StructureInput);
    TokenStream::from(input.into_token_stream())
}