From ec9c540839730be08dbb150b1ef49973e071b19c Mon Sep 17 00:00:00 2001
From: Temirkhan Myrzamadi <hirrolot@gmail.com>
Date: Thu, 23 Jul 2020 23:56:25 +0600
Subject: [PATCH] Add #[handler], #[bot_dialogue]

---
 Cargo.toml |  2 +-
 src/lib.rs | 43 ++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 557f7802..b9af08b5 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,7 +10,7 @@ edition = "2018"
 
 [dependencies]
 quote = "1.0.3"
-syn = "1.0.13"
+syn = { version = "1.0.13",  features = ["full"] }
 
 [lib]
 proc-macro = true
diff --git a/src/lib.rs b/src/lib.rs
index 1e9c9d51..9c26f972 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,5 @@
+// TODO: refactor this shit.
+
 mod attr;
 mod command;
 mod command_enum;
@@ -15,7 +17,46 @@ use crate::{
 };
 use proc_macro::TokenStream;
 use quote::{quote, ToTokens};
-use syn::{parse_macro_input, DeriveInput, Fields};
+use syn::{parse_macro_input, DeriveInput, Fields, ItemEnum};
+
+use std::fmt::Write;
+
+#[proc_macro_attribute]
+pub fn handler(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    item
+}
+
+#[proc_macro_attribute]
+pub fn bot_dialogue(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(item as ItemEnum);
+    let mut dispatch_fn = "".to_owned();
+
+    write!(dispatch_fn, "impl {0} {{ pub fn dispatch(self, cx: teloxide::dispatching::UpdateWithCx<teloxide::types::Message>) -> TransitionOut<{0}> {{ match self {{", input.ident).unwrap();
+
+    for variant in input.variants.iter() {
+        if let Some(handler) = variant
+            .attrs
+            .iter()
+            .find(|attr| match attr.path.get_ident() {
+                Some(ident) => ident == "handler",
+                None => false,
+            })
+        {
+            let mut handler_fn = handler.tokens.to_string()[1..].to_owned();
+            handler_fn.pop();
+
+            write!(
+                dispatch_fn,
+                "{}::{}(state) => {}(cx, state).await,",
+                input.ident, variant.ident, handler_fn
+            )
+            .unwrap();
+        }
+    }
+
+    write!(dispatch_fn, "}} }} }}").unwrap();
+    dispatch_fn.parse().unwrap()
+}
 
 macro_rules! get_or_return {
     ($($some:tt)*) => {