Generalize http fetch (#488)

* Generalize http fetch

- allow bytes as request body
- expose request and response headers in API
- update http example to show response headers and allow POST requests

* clippy fixes

* add missing comment, pub

* doc comment fix

* fix: missing argument when feature syntect not enabled

* formatting fixes

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* remove commented out code

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* formatting fixes

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

* cargo fmt

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

egui_web/src/http.rs

@@ -7,67 +7,75 @@ pub use epi::http::{Request, Response};
 pub async fn fetch_async(request: &Request) -> Result<Response, String> {
     fetch_jsvalue(request)
         .await
-        .map_err(|err| err.as_string().unwrap_or_default())
+        .map_err(|err| err.as_string().unwrap_or(format!("{:#?}", err)))
 }
 
 /// NOTE: Ok(..) is returned on network error.
 /// Err is only for failure to use the fetch api.
 async fn fetch_jsvalue(request: &Request) -> Result<Response, JsValue> {
-    let Request { method, url, body } = request;
-
     // https://rustwasm.github.io/wasm-bindgen/examples/fetch.html
+    // https://github.com/seanmonstar/reqwest/blob/master/src/wasm/client.rs
 
     use wasm_bindgen::JsCast;
     use wasm_bindgen_futures::JsFuture;
 
     let mut opts = web_sys::RequestInit::new();
-    opts.method(method);
+    opts.method(&request.method);
     opts.mode(web_sys::RequestMode::Cors);
 
-    if !body.is_empty() {
-        opts.body(Some(&JsValue::from_str(body)));
+    if !request.body.is_empty() {
+        let body_bytes: &[u8] = &request.body;
+        let body_array: js_sys::Uint8Array = body_bytes.into();
+        let js_value: &JsValue = body_array.as_ref();
+        opts.body(Some(js_value));
     }
 
-    let request = web_sys::Request::new_with_str_and_init(url, &opts)?;
-    request.headers().set("Accept", "*/*")?;
+    let js_request = web_sys::Request::new_with_str_and_init(&request.url, &opts)?;
+
+    for h in &request.headers {
+        js_request.headers().set(h.0, h.1)?;
+    }
 
     let window = web_sys::window().unwrap();
-    let response = JsFuture::from(window.fetch_with_request(&request)).await?;
-    assert!(response.is_instance_of::<web_sys::Response>());
-    let response: web_sys::Response = response.dyn_into().unwrap();
-
-    // // TODO: support binary get
-
-    // let body = JsFuture::from(response.text()?).await?;
-    // let body = body.as_string().unwrap_or_default();
+    let response = JsFuture::from(window.fetch_with_request(&js_request)).await?;
+    let response: web_sys::Response = response.dyn_into()?;
 
     let array_buffer = JsFuture::from(response.array_buffer()?).await?;
     let uint8_array = js_sys::Uint8Array::new(&array_buffer);
     let bytes = uint8_array.to_vec();
 
-    let header_content_type = response
-        .headers()
-        .get("Content-Type")
-        .ok()
-        .flatten()
-        .unwrap_or_default();
+    // https://developer.mozilla.org/en-US/docs/Web/API/Headers
+    // "Note: When Header values are iterated over, [...] values from duplicate header names are combined."
+    let mut headers = std::collections::BTreeMap::<String, String>::new();
+    let js_headers: web_sys::Headers = response.headers();
+    let js_iter = js_sys::try_iter(&js_headers)
+        .expect("headers try_iter")
+        .expect("headers have an iterator");
 
-    let text = if header_content_type.starts_with("text")
-        || header_content_type == "application/javascript"
-    {
-        String::from_utf8(bytes.clone()).ok()
-    } else {
-        None
-    };
+    for item in js_iter {
+        let item = item.expect("headers iterator");
+        let array: js_sys::Array = item.into();
+        let v: Vec<JsValue> = array.to_vec();
+
+        let mut key = v[0]
+            .as_string()
+            .ok_or_else(|| JsValue::from_str("headers name"))?;
+        let value = v[1]
+            .as_string()
+            .ok_or_else(|| JsValue::from_str("headers value"))?;
+
+        // for easy lookup
+        key.make_ascii_lowercase();
+        headers.insert(key, value);
+    }
 
     Ok(Response {
-        status_text: response.status_text(),
         url: response.url(),
         ok: response.ok(),
         status: response.status(),
-        header_content_type,
+        status_text: response.status_text(),
         bytes,
-        text,
+        headers,
     })
 }