From 86441cf10bd70f6b377574d89ffc60a7a7069bde Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sun, 11 Sep 2022 22:21:29 +0200
Subject: [PATCH] wow it works

---
 mono-fmt-macro/Cargo.toml |   3 +-
 mono-fmt-macro/src/lib.rs | 110 +++++++++++++++++++++++++++++++++++---
 src/lib.rs                |   7 ++-
 3 files changed, 109 insertions(+), 11 deletions(-)

diff --git a/mono-fmt-macro/Cargo.toml b/mono-fmt-macro/Cargo.toml
index 09fd01c..41083c8 100644
--- a/mono-fmt-macro/Cargo.toml
+++ b/mono-fmt-macro/Cargo.toml
@@ -9,5 +9,6 @@ proc-macro = true
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+proc-macro2 = "1.0.43"
 quote = "1.0.21"
-syn = "1.0.99"
+syn = { version = "1.0.99", features = ["full"] }
diff --git a/mono-fmt-macro/src/lib.rs b/mono-fmt-macro/src/lib.rs
index aedb30f..18c5862 100644
--- a/mono-fmt-macro/src/lib.rs
+++ b/mono-fmt-macro/src/lib.rs
@@ -1,31 +1,129 @@
+use std::{iter::Peekable, str::Chars};
+
 use proc_macro::TokenStream;
-use quote::quote;
+use proc_macro2::Span;
+use quote::{quote, ToTokens};
 use syn::{
     parse::{Parse, ParseStream},
-    Expr, parse_macro_input,
+    parse_macro_input,
+    punctuated::Punctuated,
+    Expr, LitStr, Token,
 };
 
 struct Input {
     format_str: String,
-    items: Vec<Expr>,
+    exprs: Punctuated<Expr, Token![,]>,
 }
 
 impl Parse for Input {
     fn parse(input: ParseStream) -> syn::Result<Self> {
         let first = input.parse::<syn::LitStr>()?;
+
+        let mut exprs = Punctuated::new();
+
+        if !input.is_empty() {
+            let _ = input.parse::<Token![,]>();
+        }
+
+        while !input.is_empty() {
+            let punct = input.parse()?;
+            exprs.push(punct);
+            if input.is_empty() {
+                break;
+            }
+            let value = input.parse()?;
+            exprs.push(value);
+        }
+
         Ok(Self {
             format_str: first.value(),
-            items: Vec::new(),
+            exprs,
         })
     }
 }
 
+enum FmtPart {
+    Literal(String),
+    Debug(Expr),
+    Display(Expr),
+}
+
+struct Formatter<'a, I> {
+    string: Peekable<Chars<'a>>,
+    exprs: I,
+    fmt_parts: Vec<FmtPart>,
+}
+
+impl<'a, I> Formatter<'a, I>
+where
+    I: Iterator<Item = Expr>,
+{
+    fn parse(mut self) -> Vec<FmtPart> {
+        let mut next_string = String::new();
+        while let Some(char) = self.string.next() {
+            match char {
+                '{' => {
+                    self.save_string(std::mem::take(&mut next_string));
+                    if self.string.next() != Some('}') {
+                        panic!("only supports display formatting!");
+                    }
+                    let expr = self
+                        .exprs
+                        .next()
+                        .expect("missing argument for display formatting");
+                    self.fmt_parts.push(FmtPart::Display(expr));
+                }
+                other => {
+                    next_string.push(other);
+                }
+            }
+        }
+        self.save_string(next_string);
+
+        self.fmt_parts
+    }
+
+    fn save_string(&mut self, string: String) {
+        if string.is_empty() {
+            return;
+        }
+        self.fmt_parts.push(FmtPart::Literal(string));
+    }
+}
+
+impl ToTokens for FmtPart {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        let own_tokens = match self {
+            FmtPart::Literal(lit) => {
+                let literal = LitStr::new(lit, Span::call_site());
+                quote! { mono_fmt::_private::Str(#literal) }
+            }
+            FmtPart::Display(expr) => {
+                quote! { mono_fmt::_private::DisplayArg(#expr) }
+            }
+            FmtPart::Debug(expr) => {
+                quote! { mono_fmt::_private::DebugArg(#expr) }
+            }
+        };
+
+        tokens.extend(own_tokens);
+    }
+}
+
 #[proc_macro]
 pub fn format_args(tokens: TokenStream) -> TokenStream {
     let input = parse_macro_input!(tokens as Input);
-    let str = input.format_str;
+
+    let formatter = Formatter {
+        string: input.format_str.chars().peekable(),
+        exprs: input.exprs.into_iter(),
+        fmt_parts: Vec::new(),
+    };
+
+    let fmt_parts = formatter.parse();
+
     quote! {
-        (mono_fmt::_private::Str(#str),)
+        (#(#fmt_parts),*,)
     }
     .into()
 }
diff --git a/src/lib.rs b/src/lib.rs
index 35dad59..e4a7af9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -139,7 +139,6 @@ mod tests {
     // for the macros
     use crate as mono_fmt;
 
-    use crate::arguments::DebugArg;
     use crate::format;
 
     #[test]
@@ -149,8 +148,8 @@ mod tests {
     }
 
     #[test]
-    fn debug() {
-        let result = format((DebugArg("uwu"),));
-        assert_eq!(result, "\"uwu\"");
+    fn display() {
+        let result = format!("{}", "uwu");
+        assert_eq!(result, "uwu");
     }
 }