3 files changed, 216 insertions, 0 deletions
diff --git a/askama_derive/src/generator.rs b/askama_derive/src/generator.rs
new file mode 100644
index 0000000..b1babce
--- /dev/null
+++ b/askama_derive/src/generator.rs
@@ -0,0 +1,101 @@
+use parser::{Expr, Node};
+use std::str;
+
+struct Generator {
+    buf: String,
+    indent: u8,
+    start: bool,
+}
+
+impl Generator {
+
+    fn new() -> Generator {
+        Generator { buf: String::new(), indent: 0, start: true }
+    }
+
+    fn init(&mut self, name: &str) {
+        self.write("impl askama::Template for ");
+        self.write(name);
+        self.writeln(" {");
+        self.indent();
+        self.writeln("fn render(&self) -> String {");
+        self.indent();
+        self.writeln("let mut buf = String::new();");
+    }
+
+    fn indent(&mut self) {
+        self.indent += 1;
+    }
+
+    fn dedent(&mut self) {
+        self.indent -= 1;
+    }
+
+    fn write(&mut self, s: &str) {
+        if self.start {
+            for _ in 0..(self.indent * 4) {
+                self.buf.push(' ');
+            }
+            self.start = false;
+        }
+        self.buf.push_str(s);
+    }
+
+    fn writeln(&mut self, s: &str) {
+        if s.is_empty() {
+            return;
+        }
+        self.write(s);
+        self.buf.push('\n');
+        self.start = true;
+    }
+
+    fn visit_lit(&mut self, s: &[u8]) {
+        self.write("buf.push_str(");
+        self.write(&format!("{:#?}", str::from_utf8(s).unwrap()));
+        self.writeln(");");
+    }
+
+    fn visit_var(&mut self, s: &[u8]) {
+        let var_name = str::from_utf8(s).unwrap();
+        let code = format!("std::fmt::Write::write_fmt(\
+            &mut buf, format_args!(\"{{}}\", self.{})).unwrap();", var_name);
+        self.writeln(&code);
+    }
+
+    fn visit_expr(&mut self, expr: &Expr) {
+        match expr {
+            &Expr::Var(s) => self.visit_var(s),
+        }
+    }
+
+    fn handle(&mut self, tokens: &Vec<Node>) {
+        for n in tokens {
+            match n {
+                &Node::Lit(val) => { self.visit_lit(val); },
+                &Node::Expr(ref val) => { self.visit_expr(&val); },
+            }
+        }
+    }
+
+    fn finalize(&mut self) {
+        self.writeln("buf");
+        self.dedent();
+        self.writeln("}");
+        self.dedent();
+        self.writeln("}");
+    }
+
+    fn result(self) -> String {
+        self.buf
+    }
+
+}
+
+pub fn generate(ctx_name: &str, tokens: &Vec<Node>) -> String {
+    let mut gen = Generator::new();
+    gen.init(ctx_name);
+    gen.handle(tokens);
+    gen.finalize();
+    gen.result()
+}
diff --git a/askama_derive/src/lib.rs b/askama_derive/src/lib.rs
new file mode 100644
index 0000000..d923e19
--- /dev/null
+++ b/askama_derive/src/lib.rs
@@ -0,0 +1,72 @@
+#![feature(proc_macro, proc_macro_lib)]
+
+#[macro_use]
+extern crate nom;
+extern crate proc_macro;
+#[macro_use]
+extern crate quote;
+extern crate syn;
+
+mod generator;
+mod parser;
+
+use proc_macro::TokenStream;
+use std::fs::File;
+use std::io::Read;
+use std::path::{Path, PathBuf};
+
+fn get_path_from_attrs(attrs: &Vec<syn::Attribute>) -> String {
+    for attr in attrs {
+        if attr.name() == "template" {
+            match attr.value {
+                syn::MetaItem::List(_, ref inner) => {
+                    match inner[0] {
+                        syn::NestedMetaItem::MetaItem(ref item) => {
+                            match item {
+                                &syn::MetaItem::NameValue(ref key, ref val) => {
+                                    assert_eq!(key.as_ref(), "path");
+                                    match val {
+                                        &syn::Lit::Str(ref s, _) => { return s.clone(); },
+                                        _ => panic!("template path must be a string"),
+                                    }
+                                },
+                                _ => panic!("template annotation must contain key/value pair"),
+                            }
+                        },
+                        _ => panic!("template annotation must contain item"),
+                    }
+                },
+                _ => panic!("template annotation must be of List type"),
+            }
+        }
+    }
+    panic!("template annotation not found");
+}
+
+fn get_template_source(tpl_file: &str) -> String {
+    let root = ::std::env::var("CARGO_MANIFEST_DIR").unwrap();
+    let mut path = PathBuf::from(root);
+    path.push("templates");
+    path.push(Path::new(tpl_file));
+    let mut f = File::open(path).unwrap();
+    let mut s = String::new();
+    f.read_to_string(&mut s).unwrap();
+    s
+}
+
+#[proc_macro_derive(Template, attributes(template))]
+pub fn derive_template(input: TokenStream) -> TokenStream {
+    let source = input.to_string();
+
+    let ast = syn::parse_macro_input(&source).unwrap();
+    let _ctx = match ast.body {
+        syn::Body::Struct(ref data) => data,
+        _ => panic!("#[derive(Template)] can only be used with structs"),
+    };
+
+    let name = &ast.ident;
+    let path = get_path_from_attrs(&ast.attrs);
+    let src = get_template_source(&path);
+    let tokens = parser::parse(&src);
+    generator::generate(name.as_ref(), &tokens).parse().unwrap()
+}
diff --git a/askama_derive/src/parser.rs b/askama_derive/src/parser.rs
new file mode 100644
index 0000000..5f3f8c5
--- /dev/null
+++ b/askama_derive/src/parser.rs
@@ -0,0 +1,43 @@
+use nom::{self, IResult};
+
+pub enum Expr<'a> {
+     Var(&'a [u8]),
+}
+
+pub enum Node<'a> {
+    Lit(&'a [u8]),
+    Expr(Expr<'a>),
+}
+
+fn take_content(i: &[u8]) -> IResult<&[u8], Node> {
+    if i.len() < 1 || i[0] == b'{' {
+        return IResult::Error(error_position!(nom::ErrorKind::TakeUntil, i));
+    }
+    for (j, c) in i.iter().enumerate() {
+        if *c == b'{' {
+            if i.len() < j + 2 {
+                return IResult::Done(&i[..0], Node::Lit(&i[..]));
+            } else if i[j + 1] == '{' as u8 {
+                return IResult::Done(&i[j..], Node::Lit(&i[..j]));
+            } else if i[j + 1] == '%' as u8 {
+                return IResult::Done(&i[j..], Node::Lit(&i[..j]));
+            }
+        }
+    }
+    IResult::Done(&i[..0], Node::Lit(&i[..]))
+}
+
+named!(expr_var<Expr>, map!(ws!(nom::alphanumeric), Expr::Var));
+
+named!(any_expr<Expr>, delimited!(tag!("{{"), expr_var, tag!("}}")));
+
+named!(expr_node<Node>, map!(any_expr, Node::Expr));
+
+named!(parse_template< Vec<Node> >, many1!(alt!(take_content | expr_node)));
+
+pub fn parse<'a>(src: &'a str) -> Vec<Node> {
+    match parse_template(src.as_bytes()) {
+        IResult::Done(_, res) => res,
+        _ => panic!("problems parsing template source"),
+    }
+}