Basic todo example with lru cache and in-memory db

src/lru_cache/handlers.rs

@@ -0,0 +1,137 @@
+/// These are our API handlers, the ends of each filter chain.
+/// Notice how thanks to using `Filter::and`, we can define a function
+/// with the exact arguments we'd expect from each filter in the chain.
+/// No tuples are needed, it's auto flattened for the functions.
+use anyhow::anyhow;
+use http_api_problem::HttpApiProblem;
+use std::convert::Infallible;
+use tracing::debug;
+use warp::http::StatusCode;
+
+use crate::models::{Environment, ListOptions, Todo};
+use crate::problem::reject_anyhow;
+
+pub async fn list_todos(
+    opts: ListOptions,
+    env: Environment,
+) -> Result<impl warp::Reply, warp::Rejection> {
+    env.caches
+        .list_todos
+        .get_response(opts.clone(), || async {
+            // Just return a JSON array of todos, applying the limit and offset.
+            let todos = env.db.lock().await;
+            let todos: Vec<Todo> = todos
+                .clone()
+                .into_iter()
+                .skip(opts.offset.unwrap_or(0))
+                .take(opts.limit.unwrap_or(std::usize::MAX))
+                .collect();
+            Ok(warp::reply::json(&todos))
+        })
+        .await
+}
+
+pub async fn get_todo(id: u64, env: Environment) -> Result<impl warp::Reply, warp::Rejection> {
+    env.caches
+        .todos
+        .get_response(id, || async {
+            debug!("get_todo: id={}", id);
+            let mut vec = env.db.lock().await;
+
+            // Look for the specified Todo...
+            for todo in vec.iter_mut() {
+                if todo.id == id {
+                    return Ok(warp::reply::json(&todo));
+                }
+            }
+
+            debug!("    -> todo id not found!");
+
+            // If the for loop didn't return OK, then the ID doesn't exist...
+            Err(anyhow!(HttpApiProblem::new(format!(
+                "Todo {} not found",
+                id
+            ))
+            .set_status(StatusCode::NOT_FOUND)))
+        })
+        .await
+}
+
+pub async fn create_todo(create: Todo, env: Environment) -> Result<impl warp::Reply, Infallible> {
+    debug!("create_todo: {:?}", create);
+
+    let mut vec = env.db.lock().await;
+
+    for todo in vec.iter() {
+        if todo.id == create.id {
+            debug!("    -> id already exists: {}", create.id);
+            // Todo with id already exists, return `400 BadRequest`.
+            return Ok(StatusCode::BAD_REQUEST);
+        }
+    }
+
+    // No existing Todo with id, so insert and return `201 Created`.
+    vec.push(create);
+
+    env.caches.list_todos.clear().await;
+    Ok(StatusCode::CREATED)
+}
+
+pub async fn update_todo(
+    id: u64,
+    update: Todo,
+    env: Environment,
+) -> Result<impl warp::Reply, warp::Rejection> {
+    debug!("update_todo: id={}, todo={:?}", id, update);
+    let mut vec = env.db.lock().await;
+
+    // Look for the specified Todo...
+    for todo in vec.iter_mut() {
+        if todo.id == id {
+            *todo = update;
+            env.caches
+                .todos
+                .delete_response(id)
+                .await
+                .map_err(reject_anyhow)?;
+            env.caches.list_todos.clear().await;
+            return Ok(StatusCode::OK);
+        }
+    }
+
+    debug!("    -> todo id not found!");
+
+    // If the for loop didn't return OK, then the ID doesn't exist...
+    Ok(StatusCode::NOT_FOUND)
+}
+
+pub async fn delete_todo(id: u64, env: Environment) -> Result<impl warp::Reply, warp::Rejection> {
+    debug!("delete_todo: id={}", id);
+
+    let mut vec = env.db.lock().await;
+
+    let len = vec.len();
+    vec.retain(|todo| {
+        // Retain all Todos that aren't this id...
+        // In other words, remove all that *are* this id...
+        todo.id != id
+    });
+
+    // If the vec is smaller, we found and deleted a Todo!
+    let deleted = vec.len() != len;
+
+    if deleted {
+        env.caches
+            .todos
+            .delete_response(id)
+            .await
+            .map_err(reject_anyhow)?;
+        env.caches.list_todos.clear().await;
+        // respond with a `204 No Content`, which means successful,
+        // yet no body expected...
+        Ok(StatusCode::NO_CONTENT)
+    } else {
+        debug!("    -> todo id not found!");
+        Ok(StatusCode::NOT_FOUND)
+    }
+}