CLI tessellate command custom formatting

Add --format flag to tessellate subcommand.
Update CLI readme.

Closes #289

cli/Cargo.toml

@@ -17,3 +17,5 @@ gfx = "0.17.1"
 gfx_device_gl = "0.15.0"
 gfx_window_glutin = "0.20.0"
 glutin = "0.12.0"
+itertools = "0.7.8"
+regex = "1.0.0"

cli/README.md

@@ -26,7 +26,7 @@ Tessellates an SVG path. The output is a vertex buffer and an index buffer in te
 
 Run ```$> lyon tessellate --help``` for more details.
 
-### examples
+### example
 
 ```
 $> lyon tessellate "M 0 0 L 10 0  10 10 L 0 10 z"
@@ -58,6 +58,48 @@ indices: 6
 triangles: 2
 ```
 
+To specify the output format use ```--format <FORMAT_STRING>```.
+
+There are 3 format markers, one for *vertices*, *indices* and for *triangles* (triplets of indices). Each format marker starts with ```@```, has a separator block (```{sep=...}```), a format block (```{fmt=...}``` and it ends with ```@```. In the blocks ```{``` and ```}``` characters have to be escaped!
+
+
+#### list of format variables
+- ```@vertices```
+	* ```{position.x}``` or ```{pos.x}```
+	* ```{position.y}``` or ```{pos.y}```
+- ```@indices```
+	* ```{index}``` or ```{i}```
+- ```@triangles```
+	* ```{index0}``` or ```{i0}```
+	* ```{index1}``` or ```{i1}```
+	* ```{index2}``` or ```{i2}```
+
+#### examples
+
+```
+$> lyon tessellate --format "vertices: [@vertices{sep=, }{fmt=({position.x}, {position.y})}@]" "M 0 0 L 10 0  10 10 L 0 10 z"
+vertices: [(0, 0), (10, 0), (0, 10), (10, 10)]
+
+$> lyon tessellate --format "@indices{sep=, }{fmt=[{index}]}@" "M 0 0 L 10 0  10 10 L 0 10 z"
+[0], [1], [2], [2], [1], [3]
+
+$> lyon tessellate --format '\{\n "triangles": \{\n@triangles{sep=,\n}{fmt=  "triangle": \{\n   "{i0}",\n   "{i1}",\n   "{i2}"\n  \}}@\n \}\n\}' "M 0 0 L 10 0  10 10 L 0 10 z"
+{
+ "triangles": {
+  "triangle": {
+   "1",
+   "0",
+   "2"
+  },
+  "triangle": {
+   "1",
+   "2",
+   "3"
+  }
+ }
+}
+```
+
 ## ```show```
 
 Opens a window with an interactive path viewer.

cli/src/main.rs

@@ -6,6 +6,8 @@ extern crate gfx;
 extern crate gfx_window_glutin;
 extern crate gfx_device_gl;
 extern crate glutin;
+extern crate regex;
+extern crate itertools;
 
 mod commands;
 mod tessellate;
@@ -56,6 +58,13 @@ fn main() {
                 .takes_value(true)
                 .required(false)
             )
+            .arg(Arg::with_name("FORMAT")
+                 .long("format")
+                 .help("Prints the output with the specified format")
+                 .value_name("FORMAT_STRING")
+                 .takes_value(true)
+                 .required(false)
+            )
         )
         .subcommand(
             declare_input_path(SubCommand::with_name("path"))
@@ -147,6 +156,7 @@ fn main() {
             Ok(Ok(buffers)) => {
                 tessellate::write_output(buffers,
                                          command.is_present("COUNT"),
+                                         command.value_of("FORMAT"),
                                          float_precision,
                                          output).unwrap();
             }