add date filter

Cargo.toml

@@ -15,6 +15,7 @@ build = "build.rs"
 [dependencies]
 regex = "0.1"
 lazy_static = "0.1.15"
+chrono = "0.2.22"
 clippy = {version = "0.0", optional = true}
 
 [build-dependencies]

src/filters.rs

@@ -4,6 +4,8 @@ use std::error::Error;
 use value::Value;
 use value::Value::*;
 
+use chrono::DateTime;
+
 use self::FilterError::*;
 
 #[derive(Debug)]
@@ -232,6 +234,25 @@ pub fn last(input: &Value, _args: &[Value]) -> FilterResult {
     }
 }
 
+pub fn date(input: &Value, args: &[Value]) -> FilterResult {
+    if args.len() != 1 {
+        return Err(FilterError::InvalidArgumentCount(format!("expected 1, {} given", args.len())));
+    }
+
+    let date = match input {
+        &Value::Str(ref s) => try!(DateTime::parse_from_str(&s, "%d %B %Y %H:%M:%S %z")
+                                   .map_err(|e| FilterError::InvalidType(format!("Invalid date format: {}", e)))),
+        _ => return Err(FilterError::InvalidType("String expected".to_owned())),
+    };
+
+    let format = match args[0] {
+        Value::Str(ref s) => s,
+        _ => return Err(InvalidArgument(0, "Str expected".to_owned())),
+    };
+
+    Ok(Value::Str(format!("{}", date.format(format))))
+}
+
 #[cfg(test)]
 mod tests {
 
@@ -383,4 +404,9 @@ mod tests {
         assert_eq!(unit!(last, Array(vec![tos!("test"), tos!("last")])), tos!("last"));
         assert_eq!(unit!(last, Array(vec![])), tos!(""));
     }
+
+    #[test]
+    fn unit_date() {
+        assert_eq!(unit!(date, tos!("13 Jun 2016 02:30:00 +0300"), &[tos!("%Y-%m-%d")]), tos!("2016-06-13"));
+    }
 }

src/lib.rs

@@ -61,6 +61,7 @@
 #[macro_use]
 extern crate lazy_static;
 extern crate regex;
+extern crate chrono;
 
 use std::collections::HashMap;
 use lexer::Element;

src/template.rs

@@ -1,6 +1,6 @@
 use Renderable;
 use context::Context;
-use filters::{size, upcase, downcase, capitalize, minus, plus, times, divided_by, ceil, floor, round, prepend, append, first, last, pluralize, replace};
+use filters::{size, upcase, downcase, capitalize, minus, plus, times, divided_by, ceil, floor, round, prepend, append, first, last, pluralize, replace, date};
 use error::Result;
 
 pub struct Template {
@@ -27,6 +27,7 @@ impl Renderable for Template {
         context.add_filter("append", Box::new(append));
         context.add_filter("replace", Box::new(replace));
         context.add_filter("pluralize", Box::new(pluralize));
+        context.add_filter("date", Box::new(date));
 
         let mut buf = String::new();
         for el in &self.elements {