Initial implementation (#4)

src/lib.rs

@@ -2,14 +2,16 @@ mod utils;
 
 use wasm_bindgen::prelude::*;
 
-#[wasm_bindgen]
-extern "C" {
-    fn alert(s: &str);
-}
+#[cfg(feature = "wee_alloc")]
+#[global_allocator]
+static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
 
 #[wasm_bindgen]
-pub fn greet() {
+pub fn merge(files: js_sys::Array) -> wasm_bindgen::JsValue {
     utils::set_panic_hook();
+    let files: Vec<String> = utils::translate_js_to_rust(files);
+    let merged: gpx::Gpx = utils::join_gpx_files(files);
+    let out_vec: Vec<u8> = utils::write_gpx_to_buffer(merged);
 
-    alert("Hello, gpx-web-utils!");
+    JsValue::from_str(&String::from_utf8(out_vec).unwrap())
 }

src/utils.rs

@@ -1,10 +1,46 @@
 pub fn set_panic_hook() {
-    // When the `console_error_panic_hook` feature is enabled, we can call the
-    // `set_panic_hook` function at least once during initialization, and then
-    // we will get better error messages if our code ever panics.
-    //
-    // For more details see
-    // https://github.com/rustwasm/console_error_panic_hook#readme
     #[cfg(feature = "console_error_panic_hook")]
     console_error_panic_hook::set_once();
 }
+
+pub fn translate_js_to_rust(files: js_sys::Array) -> Vec<String> {
+    // https://github.com/rustwasm/wasm-bindgen/issues/111
+    files.iter().map(|f| f.as_string().unwrap()).collect()
+}
+
+pub fn join_gpx_files(files: Vec<String>) -> gpx::Gpx {
+    let mut merged: gpx::Gpx = Default::default();
+
+    for file in files.iter() {
+        let buffer = std::io::BufReader::new(file.as_bytes());
+        let mut parsed_gpx: gpx::Gpx = gpx::read(buffer).expect("invalid gpx");
+
+        merged.tracks.append(&mut parsed_gpx.tracks);
+        merged.waypoints.append(&mut parsed_gpx.waypoints);
+    }
+
+    let link = gpx::Link {
+        href: String::from("https://gpx.thermokar.st"),
+        ..Default::default()
+    };
+    let author = gpx::Person {
+        link: Some(link),
+        ..Default::default()
+    };
+    let metadata = gpx::Metadata {
+        name: Some(String::from("merged")),
+        author: Some(author),
+        ..Default::default()
+    };
+    merged.metadata = Some(metadata);
+    merged.version = gpx::GpxVersion::Gpx11;
+
+    merged
+}
+
+pub fn write_gpx_to_buffer(gpx: gpx::Gpx) -> Vec<u8> {
+    let mut buffer = Vec::new();
+    gpx::write(&gpx, &mut buffer).unwrap();
+
+    buffer
+}