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extern crate proc_macro;
extern crate proc_macro2;
extern crate syn;

extern crate quote;

use proc_macro2::TokenStream;

use syn::{
    parse_macro_input,
    DeriveInput,
};
use syn::parse::Error;
use syn::spanned::Spanned;

use quote::quote;

mod util;
mod field_info;
mod struct_info;
mod builder_attr;


/// `TypedBuilder` is not a real type - deriving it will generate a `::builder()` method on your
/// struct that will return a compile-time checked builder. Set the fields using setters with the
/// same name as the struct's fields that accept `Into` types for the type of the field, and call
/// `.build()` when you are done to create your object.
///
/// Trying to set the same fields twice will generate a compile-time error. Trying to build without
/// setting one of the fields will also generate a compile-time error - unless that field is marked
/// as `#[builder(default)]`, in which case the `::default()` value of it's type will be picked. If
/// you want to set a different default, use `#[builder(default=...)]`.
///
/// # Examples
///
/// ```
/// #[macro_use]
/// extern crate typed_builder;
///
/// #[derive(PartialEq, TypedBuilder)]
/// struct Foo {
///     // Mandatory Field:
///     x: i32,
///
///     // #[default] without parameter - use the type's default
///     #[builder(default)]
///     y: Option<i32>,
///
///     // Or you can set the default
///     #[builder(default=20)]
///     z: i32,
///
///     // If the default cannot be parsed, you must encode it as a string
///     #[builder(default_code="vec![30, 40]")]
///     w: Vec<u32>,
/// }
///
/// fn main() {
///     assert!(
///         Foo::builder().x(1).y(2).z(3).w(vec![4, 5]).build()
///         == Foo { x: 1, y: Some(2), z: 3, w: vec![4, 5] });
///
///     // Change the order of construction:
///     assert!(
///         Foo::builder().z(1).x(2).w(vec![4, 5]).y(3).build()
///         == Foo { x: 2, y: Some(3), z: 1, w: vec![4, 5] });
///
///     // Optional fields are optional:
///     assert!(
///         Foo::builder().x(1).build()
///         == Foo { x: 1, y: None, z: 20, w: vec![30, 40] });
///
///     // This will not compile - because we did not set x:
///     // Foo::builder().build();
///
///     // This will not compile - because we set y twice:
///     // Foo::builder().x(1).y(2).y(3);
/// }
/// ```
#[proc_macro_derive(TypedBuilder, attributes(builder))]
pub fn derive_typed_builder(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    match impl_my_derive(&input) {
        Ok(output) => {
            output.into()
        },
        Err(error) =>{
            error.to_compile_error().into()
        }
    }
}

fn impl_my_derive(ast: &syn::DeriveInput) -> Result<TokenStream, Error> {
    let data = match &ast.data {
        syn::Data::Struct(data) => {
            match &data.fields {
                syn::Fields::Named(fields) => {
                    let struct_info = struct_info::StructInfo::new(&ast, fields.named.iter())?;
                    let builder_creation = struct_info.builder_creation_impl()?;
                    let conversion_helper = struct_info.conversion_helper_impl()?;
                    let fields = struct_info.fields.iter().map(|f| struct_info.field_impl(f).unwrap());
                    let fields = quote!(#(#fields)*);
                    let build_method = struct_info.build_method_impl();

                    quote!{
                        #builder_creation
                        #conversion_helper
                        #( #fields )*
                        #build_method
                    }
                }
                syn::Fields::Unnamed(_) => return Err(Error::new(ast.span(), "SmartBuilder is not supported for tuple structs")),
                syn::Fields::Unit => return Err(Error::new(ast.span(), "SmartBuilder is not supported for unit structs")),
            }
        }
        syn::Data::Enum(_) => return Err(Error::new(ast.span(), "SmartBuilder is not supported for enums")),
        syn::Data::Union(_) => return Err(Error::new(ast.span(), "SmartBuilder is not supported for unions")),
    };
    Ok(data)
}