1 files changed, 90 insertions, 0 deletions
diff --git a/derive/src/from/mod.rs b/derive/src/from/mod.rs
new file mode 100644
index 0000000..2855d1a
--- /dev/null
+++ b/derive/src/from/mod.rs
@@ -0,0 +1,90 @@
+use quote::quote;
+use syn;
+use syn::parse_macro_input;
+
+use darling::{FromDeriveInput, FromVariant};
+
+#[derive(Debug, FromDeriveInput)]
+#[darling(attributes(from), supports(enum_any))]
+struct Enum {
+    ident: syn::Ident,
+    attrs: Vec<syn::Attribute>,
+}
+
+#[derive(Debug, FromVariant)]
+#[darling(attributes(from))]
+struct EnumField {
+    ident: syn::Ident,
+    fields: darling::ast::Fields<syn::Type>,
+
+    #[darling(default)]
+    ignore: bool,
+}
+
+pub fn from(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as syn::DeriveInput);
+    // println!("{:#?}", input);
+
+    let network = Enum::from_derive_input(&input).unwrap();
+    // println!("{:#?}", network);
+
+    let enum_name = network.ident;
+
+    let fields: Vec<EnumField> = match &input.data {
+        syn::Data::Enum(data) => data
+            .variants
+            .iter()
+            .map(|field| EnumField::from_variant(field).expect("Could not parse field"))
+            .collect(),
+        _ => panic!("from: not an enum"),
+    };
+
+    let derives = fields
+        .iter()
+        .filter(|field| field.fields.fields.len() > 0 && !field.ignore)
+        .map(|field| {
+            let variant = &field.ident;
+            let inner_type = &field.fields.fields[0];
+            let inner_type_str = format!("{}", quote! { #inner_type });
+
+            quote! {
+                impl From<#inner_type> for #enum_name {
+                    fn from(input: #inner_type) -> Self {
+                        Self::#variant(input)
+                    }
+                }
+
+                impl std::convert::TryFrom<#enum_name> for #inner_type {
+                    type Error = String;
+
+                    fn try_from(input: #enum_name) -> Result<Self, Self::Error> {
+                        match input {
+                            #enum_name::#variant(input) => Ok(input),
+                            v => Err(format!("variant::from: {} wrong variant expected: {:?}", #inner_type_str, v)),
+                        }
+                    }
+                }
+
+                impl std::convert::TryFrom<&#enum_name> for #inner_type {
+                    type Error = String;
+
+                    fn try_from(input: &#enum_name) -> Result<Self, Self::Error> {
+                        match input {
+                            #enum_name::#variant(input) => Ok(input.clone()),
+                            v => Err(format!("variant::from: {} wrong variant expected: {:?}", #inner_type_str, v)),
+                        }
+                    }
+                }
+            }
+        });
+
+    // println!("{:#?}", fields);
+
+    let gen = quote! {
+        #(#derives)*
+    };
+
+    // println!("{}", gen);
+
+    gen.into()
+}