1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124

use proc_macro2::TokenStream;
use quote::{format_ident, quote};
use std::cmp::min;
use syn::{spanned::Spanned, Data, DeriveInput, Error, Field, Fields, Ident, Result, Type};

struct ParsedFields {
	fields: Vec<(Ident, Type)>,
	named: bool
}

impl ParsedFields {
	fn from_named<I>(fields: I) -> Self
	where
		I: Iterator<Item = Field>
	{
		let fields = fields.map(|field| (field.ident.unwrap(), field.ty)).collect();
		Self { fields, named: true }
	}

	fn from_unnamed<I>(fields: I) -> Self
	where
		I: Iterator<Item = Field>
	{
		let fields = fields
			.enumerate()
			.map(|(i, field)| (format_ident!("arg{}", i), field.ty))
			.collect();
		Self { fields, named: false }
	}

	fn from_unit() -> Self {
		Self {
			fields: Vec::new(),
			named: false
		}
	}
}

pub fn expand_from_body(input: DeriveInput) -> Result<TokenStream> {
	let ident = input.ident;
	let generics = input.generics;

	let strukt = match input.data {
		Data::Enum(inum) => Err(inum.enum_token.span()),
		Data::Struct(strukt) => Ok(strukt),
		Data::Union(uni) => Err(uni.union_token.span())
	}
	.map_err(|span| Error::new(span, "#[derive(FromBody)] only works for structs"))?;

	let fields = match strukt.fields {
		Fields::Named(named) => ParsedFields::from_named(named.named.into_iter()),
		Fields::Unnamed(unnamed) => ParsedFields::from_unnamed(unnamed.unnamed.into_iter()),
		Fields::Unit => ParsedFields::from_unit()
	};

	let mut where_clause = quote!();
	let mut block = quote!();
	let mut body_ident = format_ident!("_body");
	let mut type_ident = format_ident!("_type");

	if let Some(body_field) = fields.fields.get(0) {
		body_ident = body_field.0.clone();
		let body_ty = &body_field.1;
		where_clause = quote! {
			#where_clause
			#body_ty: for<'a> From<&'a [u8]>,
		};
		block = quote! {
			#block
			let #body_ident: &[u8] = &#body_ident;
			let #body_ident: #body_ty = #body_ident.into();
		};
	}

	if let Some(type_field) = fields.fields.get(1) {
		type_ident = type_field.0.clone();
		let type_ty = &type_field.1;
		where_clause = quote! {
			#where_clause
			#type_ty: From<::gotham_restful::Mime>,
		};
		block = quote! {
			#block
			let #type_ident: #type_ty = #type_ident.into();
		};
	}

	for field in &fields.fields[min(2, fields.fields.len())..] {
		let field_ident = &field.0;
		let field_ty = &field.1;
		where_clause = quote! {
			#where_clause
			#field_ty: ::std::default::Default,
		};
		block = quote! {
			#block
			let #field_ident: #field_ty = Default::default();
		};
	}

	let field_names: Vec<&Ident> = fields.fields.iter().map(|field| &field.0).collect();
	let ctor = if fields.named {
		quote!(Self { #(#field_names),* })
	} else {
		quote!(Self ( #(#field_names),* ))
	};

	Ok(quote! {
		impl #generics ::gotham_restful::FromBody for #ident #generics
		where #where_clause
		{
			type Err = ::std::convert::Infallible;

			fn from_body(
				#body_ident: ::gotham_restful::gotham::hyper::body::Bytes,
				#type_ident: ::gotham_restful::Mime
			) -> ::std::result::Result<Self, ::std::convert::Infallible>
			{
				#block
				::std::result::Result::Ok(#ctor)
			}
		}
	})
}