feat(engine): infrastructure

* allow usage of cmn.rs for common types (like Error types)
* instantiate an engine and handle errors, in an initial quick and dirty
  way.

 Fixes #52

src/mako/cli/lib/docopt.mako

@@ -13,7 +13,7 @@
     upload_protocols_used = set()
     output_used = False
 %>\
-docopt!(Args derive Debug, "
+docopt!(Options derive Debug, "
 Usage: 
 % for resource in sorted(c.rta_map.keys()):
     % for method in sorted(c.rta_map[resource]):

src/mako/cli/lib/engine.mako

@@ -0,0 +1,24 @@
+<%namespace name="util" file="../../lib/util.mako"/>\
+<%!
+    from cli import (mangle_subcommand, new_method_context, PARAM_FLAG, STRUCT_FLAG, UPLOAD_FLAG, OUTPUT_FLAG, VALUE_ARG,
+                     CONFIG_DIR, SCOPE_FLAG, is_request_value_property, FIELD_SEP, docopt_mode, FILE_ARG, MIME_ARG, OUT_ARG)
+
+    v_arg = '<%s>' % VALUE_ARG
+%>\
+<%def name="new(c)">\
+mod cmn;
+use cmn::{InvalidOptionsError, ArgumentError};
+
+struct Engine {
+    opts: Options,
+}
+
+
+impl Engine {
+    fn new(options: Options) -> Result<Engine, InvalidOptionsError> {
+        Ok(Engine {
+            opts: options,
+        })
+    }
+}
+</%def>

src/mako/cli/main.rs.mako

@@ -1,4 +1,5 @@
 <%namespace name="docopt" file="lib/docopt.mako"/>\
+<%namespace name="engine" file="lib/engine.mako"/>\
 <%namespace name="util" file="../lib/util.mako"/>\
 <%  
     from util import (new_context, rust_comment)
@@ -9,16 +10,30 @@
 <%block filter="rust_comment">\
 <%util:gen_info source="${self.uri}" />\
 </%block>
-#![feature(plugin)]
+#![feature(plugin, exit_status)]
 #![plugin(docopt_macros)]
 
 extern crate docopt;
 extern crate rustc_serialize;
 
+use std::io;
+use std::env;
+use std::io::Write;
+
 ${docopt.new(c)}\
 
+${engine.new(c)}\
+
 fn main() {
-    let args: Args = Args::docopt().decode().unwrap_or_else(|e| e.exit());
-    println!("{:?}", args);
-    println!("Hello, ${id} !");
+    let opts: Options = Options::docopt().decode().unwrap_or_else(|e| e.exit());
+    println!("{:?}", opts);
+    match Engine::new(opts) {
+        Err(e) => {
+            write!(io::stderr(), "{:?}", e).ok();
+            env::set_exit_status(e.exit_code);
+        },
+        Ok(mut engine) => {
+
+        }
+    }
 }

src/rust/cli/cmn.rs

@@ -0,0 +1,12 @@
+
+
+#[derive(Debug)]
+pub enum ArgumentError {
+    ConfigurationDirectoryInaccessible(String),
+}
+
+#[derive(Debug)]
+pub struct InvalidOptionsError {
+    pub issues: Vec<ArgumentError>,
+    pub exit_code: i32,
+}