Start work on web UI command

cli/src/web_ui.rs

@@ -0,0 +1,60 @@
+use super::wasm;
+use std::fs;
+use std::net::TcpListener;
+use std::path::Path;
+use std::str::FromStr;
+use tiny_http::{Header, Response, Server};
+use webbrowser;
+
+const PLAYGROUND_JS: &'static [u8] = include_bytes!("../../docs/assets/js/playground.js");
+const LIB_JS: &'static [u8] = include_bytes!("../../lib/binding_web/tree-sitter.js");
+const LIB_WASM: &'static [u8] = include_bytes!("../../lib/binding_web/tree-sitter.wasm");
+const HTML: &'static [u8] = include_bytes!("./web_ui.html");
+
+pub fn serve(grammar_path: &Path) {
+    let port = get_available_port().expect("Couldn't find an available port");
+    let url = format!("127.0.0.1:{}", port);
+    let server = Server::http(&url).expect("Failed to start web server");
+    let grammar_name = wasm::get_grammar_name(&grammar_path.join("src"))
+        .map_err(|e| format!("Failed to get wasm filename: {:?}", e))
+        .unwrap();
+    let language_wasm = fs::read(format!("./tree-sitter-{}.wasm", grammar_name)).unwrap();
+
+    webbrowser::open(&format!("http://127.0.0.1:{}", port))
+        .map_err(|e| format!("Failed to open '{}' in a web browser. Error: {}", url, e))
+        .unwrap();
+
+    let html_header = Header::from_str("Content-type: text/html").unwrap();
+    let js_header = Header::from_str("Content-type: application/javascript").unwrap();
+    let wasm_header = Header::from_str("Content-type: application/wasm").unwrap();
+
+    for request in server.incoming_requests() {
+        let (body, header) = match request.url() {
+            "/" => (HTML, &html_header),
+            "/playground.js" => (PLAYGROUND_JS, &js_header),
+            "/tree-sitter.js" => (LIB_JS, &js_header),
+            "/tree-sitter.wasm" => (LIB_WASM, &wasm_header),
+            "/tree-sitter-parser.wasm" => (language_wasm.as_slice(), &wasm_header),
+            _ => {
+                request
+                    .respond(Response::from_string("Not found").with_status_code(404))
+                    .expect("Failed to write HTTP response");
+                continue;
+            }
+        };
+        let response = Response::from_string("")
+            .with_data(body, Some(body.len()))
+            .with_header(header.clone());
+        request
+            .respond(response)
+            .expect("Failed to write HTTP response");
+    }
+}
+
+fn get_available_port() -> Option<u16> {
+    (8000..12000).find(port_is_available)
+}
+
+fn port_is_available(port: &u16) -> bool {
+    TcpListener::bind(("127.0.0.1", *port)).is_ok()
+}