Add json as an output type.

* Uses serde_json
* Doesn't handle macro values very well.
* Handles maps and lists just fine.
* doesn't pretty print the values though.

Cargo.toml

@@ -14,6 +14,7 @@ version        = "^3.2"
 [dependencies]
 nom_locate  = "^0.1.1"
 clap        = "~2.26.0"
+serde_json = "~1.0.9"
 
 [lib]
 name = "ucglib"

TODO.md

@@ -5,11 +5,12 @@
 You should be able to ask the compiler to tell you any value or set of values in the
 compiled configuration.
 
-## Translation Language (Experiemental)
+## Translation Language (Experimental)
 
 For some configuration file formats we need a way to specify a particular
 organiztion for a given configuration structure. Some options here could be
 
+* Simple data export (json) 
 * A Functional Transform similar to xslt or css transforms.
 * A Templating language
 * Annotations.

src/convert/flags.rs

@@ -25,9 +25,7 @@ impl FlagConverter {
     pub fn new() -> Self {
         FlagConverter {}
     }
-}
 
-impl FlagConverter {
     fn write(&self, v: &Val, w: &mut Write) -> Result<()> {
         match v {
             &Val::Float(ref f) => {
@@ -45,6 +43,10 @@ impl FlagConverter {
             }
             &Val::Tuple(ref flds) => {
                 for &(ref name, ref val) in flds.iter() {
+                    if val.is_tuple() {
+                        eprintln!("Skipping embedded tuple...");
+                        return Ok(());
+                    }
                     try!(write!(w, "--{} ", name.val));
                     // TODO(jwall): What if the value is a tuple?
                     try!(self.write(&val, w));
@@ -61,6 +63,6 @@ impl FlagConverter {
 
 impl Converter for FlagConverter {
     fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result<()> {
-        return self.write(&v, &mut w);
+        self.write(&v, &mut w)
     }
 }

src/convert/json.rs

@@ -0,0 +1,86 @@
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+use std::rc::Rc;
+use std::io::Write;
+use std::io::Result;
+
+use serde_json;
+
+use ast;
+use build::Val;
+use convert::traits::Converter;
+
+pub struct JsonConverter {}
+
+impl JsonConverter {
+    pub fn new() -> Self {
+        JsonConverter {}
+    }
+
+    fn convert_list(&self, items: &Vec<Rc<Val>>) -> Result<serde_json::Value> {
+        let mut v = Vec::new();
+        for val in items.iter() {
+            v.push(try!(self.convert_value(val)));
+        }
+        Ok(serde_json::Value::Array(v))
+    }
+
+    fn convert_tuple(&self, items: &Vec<(ast::Positioned<String>, Rc<Val>)>) -> Result<serde_json::Value> {
+        let mut mp = serde_json::Map::new();
+        for &(ref k, ref v) in items.iter() {
+            mp.entry(k.val.clone()).or_insert(try!(self.convert_value(v)));
+        }
+        Ok(serde_json::Value::Object(mp))
+    }
+
+    fn convert_value(&self, v: &Val) -> Result<serde_json::Value> {
+        let jsn_val = match v {
+            &Val::Float(f) => {
+                let n = match serde_json::Number::from_f64(f) {
+                    Some(n) => n,
+                    // In theory this should never happen. But on the off chance that it does...
+                    None => panic!("Float is too large or Not a Number {}", f),
+                };
+                serde_json::Value::Number(n)
+            },
+            &Val::Int(i) => {
+                let n = match serde_json::Number::from_f64(i as f64) {
+                    Some(n) => n,
+                    // In theory this should never happen. But on the off chance that it does...
+                    None => panic!("Float is too large or Not a Number {}", i),
+                };
+                serde_json::Value::Number(n)
+            },
+            &Val::String(ref s) => serde_json::Value::String(s.clone()),
+            &Val::Macro(_) => {
+                // TODO(jwall): We probably want to actually skip this but for now
+                // we'll use null
+                eprintln!("Skipping macro encoding as null...");
+                serde_json::Value::Null
+            },
+            &Val::List(ref l) => try!(self.convert_list(l)),
+            &Val::Tuple(ref t) => try!(self.convert_tuple(t)),
+        };
+        Ok(jsn_val)
+    }
+    
+    fn write(&self, v: &Val, w: &mut Write) -> Result<()> {
+        let jsn_val = try!(self.convert_value(v));
+        try!(serde_json::to_writer(w, &jsn_val));
+        Ok(())
+    }
+}
+
+impl Converter for JsonConverter {
+    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result<()> {
+        self.write(&v, &mut w)
+    }
+}

src/convert/mod.rs

@@ -12,6 +12,7 @@
 //  See the License for the specific language governing permissions and
 //  limitations under the License.
 pub mod flags;
+pub mod json;
 pub mod traits;
 
 use std::io;
@@ -29,6 +30,9 @@ impl ConverterRunner {
         if typ == "flags" {
             return Ok(ConverterRunner { converter: Box::new(flags::FlagConverter::new()) });
         }
+        if typ == "json" {
+            return Ok(ConverterRunner { converter: Box::new(json::JsonConverter::new()) });
+        }
         return Err(format!("Unknown Target output type: {}", typ));
     }
 

src/lib.rs

@@ -17,6 +17,7 @@
 extern crate nom;
 #[macro_use]
 extern crate nom_locate;
+extern crate serde_json;
 
 #[macro_use]
 pub mod ast;

src/main.rs

@@ -34,7 +34,7 @@ fn do_flags<'a>() -> clap::ArgMatches<'a> {
             (@subcommand build =>
              (about: "Compile a specific ucg file.")
              (@arg sym: --sym +takes_value "Specify a specific let binding in the ucg file to output.")
-             (@arg target: --target -t +required +takes_value "Target output type.")
+             (@arg target: --target -t +required +takes_value "Target output type. (flags, json)")
              (@arg out: --out -o +takes_value "Output file to write to.")
              (@arg INPUT: +required "Input ucg file to build.")
             )