add help switch

src/main.rs

@@ -20,7 +20,7 @@ async fn main() {
                     write_all().await;
                 }
                 "--help" => {
-                    panic!("not implemented");
+                    print_help();
                 }
                 _ => {
                     panic!("bad command {}", cmd);
@@ -53,6 +53,20 @@ async fn main() {
     }
 }
 
+fn print_help() {
+    println!(
+        r"
+    Usage: sfwikiscraper <options> 
+
+    --help: display this help
+    --all: fetch all recipes
+    --tier <tier>: fetches all recipes of the nth tier
+    --item <url>: fetches the recipe (only by url for now)
+    --test <url>: parse the json format shipped in <url>
+    "
+    );
+}
+
 async fn fetch_data(url: String) -> Vec<Value> {
     let webdata = reqwest::get(url)
         .await
@@ -150,11 +164,14 @@ async fn write_all() {
             &join_all(
                 (0..9)
                     .into_iter()
-                    .map(|i| async move { fetch_tier(i.to_string()).await })
+                    .map(|i| async move { fetch_tier(i.to_string()).await }),
             )
             .await
             .into_iter()
-            .reduce(|mut acc, e| { acc.extend(e.iter().cloned()); acc })
+            .reduce(|mut acc, e| {
+                acc.extend(e.iter().cloned());
+                acc
+            }),
         )
         .unwrap()
         .as_bytes(),