share database reader instance

src/main.rs

@@ -15,6 +15,8 @@ use rocket_contrib::templates::Template;
 use rand::distributions::Uniform;
 use rand::Rng;
 
+use std::sync::Arc;
+
 use chgk_ledb_lib::db;
 use chgk_ledb_lib::questions::Question;
 
@@ -32,18 +34,24 @@ impl<T, E> ErrorEmpty for Result<T, E> {
     }
 }
 
+type DataBaseInner = db::Reader<Question>;
+type DataBase = Arc<DataBaseInner>;
 struct AppState{
+    db: DataBase,
     database_distribution: Uniform<usize>,
 }
 
-fn open_db() -> db::Reader<Question> {
-    db::Reader::new(DB_FILENAME, 2048).expect("new db reader")
-}
+impl From<DataBaseInner> for AppState {
+    fn from(db: DataBaseInner) -> Self {
+        let last_id = db.len();
+        let database_distribution = rand::distributions::Uniform::new_inclusive(1usize, last_id);
+        let db = Arc::new(db);
 
-fn get_database_distribution() -> Uniform<usize> {
-    let last_id = open_db().len();
-
-    rand::distributions::Uniform::new_inclusive(1usize, last_id)
+        Self {
+            db,
+            database_distribution
+        }
+    }
 }
 
 fn random_question_id(database_distribution: &Uniform<usize>) -> usize {
@@ -51,12 +59,12 @@ fn random_question_id(database_distribution: &Uniform<usize>) -> usize {
     rng.sample(database_distribution)
 }
 
-fn get_question(id: usize) -> Result<Question, ()> {
-    open_db().get(id - 1).err_empty()
+fn get_question(db: &DataBase, id: usize) -> Result<Question, ()> {
+    db.get(id - 1).err_empty()
 }
 
 fn show_question_details(template_name: &'static str, data: &AppState, id: usize) -> Template {
-    match get_question(id) {
+    match get_question(&data.db, id) {
         Ok(question) => {
             let mut context = serde_json::to_value(question).expect("question serialize");
             if context.is_object() {
@@ -68,7 +76,7 @@ fn show_question_details(template_name: &'static str, data: &AppState, id: usize
         Err(_) => {
             use std::collections::HashMap;
             let context: HashMap<String, String> = HashMap::new();
-            Template::render("404", &context)
+            Template::render("404", context)
         }
     }
 }
@@ -103,13 +111,11 @@ fn index(data: State<AppState>) -> Redirect {
 fn not_found(_req: &rocket::Request) -> Template {
     use std::collections::HashMap;
     let context: HashMap<String, String> = HashMap::new();
-    Template::render("404", &context)
+    Template::render("404", context)
 }
 
 fn rocket() -> Rocket {
-    let state = AppState {
-        database_distribution: get_database_distribution(),
-    };
+    let state: AppState = db::Reader::new(DB_FILENAME, 2048).expect("open db").into();
 
     rocket::ignite()
         .manage(state)