app: Create CommonComponent

This is a utility that gathers common parts of components, like task
and error handling.

app/src/infra/common_component.rs

@@ -0,0 +1,68 @@
+use anyhow::{Error, Result};
+use yew::{
+    prelude::*,
+    services::{fetch::FetchTask, ConsoleService},
+};
+
+pub trait CommonComponent<C: Component + CommonComponent<C>>: Component {
+    fn handle_msg(&mut self, msg: <Self as Component>::Message) -> Result<bool>;
+    fn mut_common(&mut self) -> &mut CommonComponentParts<C>;
+}
+
+pub struct CommonComponentParts<C: CommonComponent<C>> {
+    pub link: ComponentLink<C>,
+    pub props: <C as Component>::Properties,
+    pub error: Option<Error>,
+    pub task: Option<FetchTask>,
+}
+
+impl<C: CommonComponent<C>> CommonComponentParts<C> {
+    pub fn create(props: <C as Component>::Properties, link: ComponentLink<C>) -> Self {
+        Self {
+            link,
+            props,
+            error: None,
+            task: None,
+        }
+    }
+
+    pub fn update(com: &mut C, msg: <C as Component>::Message) -> ShouldRender {
+        com.mut_common().error = None;
+        match com.handle_msg(msg) {
+            Err(e) => {
+                ConsoleService::error(&e.to_string());
+                com.mut_common().error = Some(e);
+                true
+            }
+            Ok(b) => b,
+        }
+    }
+
+    pub fn call_backend<M, Req, Cb, Resp>(
+        &mut self,
+        method: M,
+        req: Req,
+        callback: Cb,
+    ) -> Result<()>
+    where
+        M: Fn(Req, Callback<Resp>) -> Result<FetchTask>,
+        Cb: Fn(Resp) -> <C as Component>::Message + 'static,
+    {
+        self.task = Some(method(req, self.link.callback(callback))?);
+        Ok(())
+    }
+}
+
+impl<C: Component + CommonComponent<C>> std::ops::Deref for CommonComponentParts<C> {
+    type Target = <C as Component>::Properties;
+
+    fn deref(&self) -> &<Self as std::ops::Deref>::Target {
+        &self.props
+    }
+}
+
+impl<C: Component + CommonComponent<C>> std::ops::DerefMut for CommonComponentParts<C> {
+    fn deref_mut(&mut self) -> &mut <Self as std::ops::Deref>::Target {
+        &mut self.props
+    }
+}

app/src/infra/mod.rs

@@ -1,4 +1,5 @@
 pub mod api;
+pub mod common_component;
 pub mod cookies;
 pub mod graphql;
 pub mod modal;