feat: cache github api

This commit allows The Senpy Club API to cache GitHub's API response,
refreshing the cache every fifty accesses.

This commit also gets rid of a few dependencies which were replaced by
their standard library counterparts.

5 files changed, 64 insertions, 50 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 4c71625..8caad89 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,7 +2,7 @@
 
 [package]
 name = "api-worker"
-version = "0.1.0"
+version = "0.2.0"
 authors = ["Fuwn <[email protected]>"]
 edition = "2021"
 description = "API (as a Cloudflare Worker!)"
@@ -38,11 +38,6 @@ dotenv = "0.15.0"
 # Worker
 worker = "0.0.9"
 
-# Utility
-cfg-if = "1.0.0"
-const_format = "0.2.22"
-lazy_static = "1.4.0"
-
 # Web
 reqwest = { version = "0.11.10", features = ["json"] }
 
diff --git a/src/constants.rs b/src/constants.rs
index 6f3e6e4..ad46dfd 100644
--- a/src/constants.rs
+++ b/src/constants.rs
@@ -16,27 +16,29 @@
 // Copyright (C) 2022-2022 Fuwn <[email protected]>
 // SPDX-License-Identifier: GPL-3.0-only
 
-use const_format::formatcp;
-
-lazy_static::lazy_static! {
-  pub static ref INDEX: String = {
-    format!(
-      include_str!("index.rst"),
-      format_args!(
-        "https://github.com/senpy-club/api-worker/tree/{}",
-        env!("VERGEN_GIT_SHA"),
-      )
-    )
-  };
-}
+use std::lazy::SyncLazy;
 
 const GITHUB_REPOSITORY: &str =
   "cat-milk/Anime-Girls-Holding-Programming-Books";
-pub const GITHUB_USER_CONTENT: &str = formatcp!(
-  "https://raw.githubusercontent.com/{}/master/",
-  GITHUB_REPOSITORY
-);
-pub const GITHUB_API_ENDPOINT: &str = formatcp!(
-  "https://api.github.com/repos/{}/git/trees/master?recursive=1",
-  GITHUB_REPOSITORY,
-);
+
+pub static INDEX: SyncLazy<String> = SyncLazy::new(|| {
+  format!(
+    include_str!("index.rst"),
+    format_args!(
+      "https://github.com/senpy-club/api-worker/tree/{}",
+      env!("VERGEN_GIT_SHA"),
+    )
+  )
+});
+pub static GITHUB_USER_CONTENT: SyncLazy<String> = SyncLazy::new(|| {
+  format!(
+    "https://raw.githubusercontent.com/{}/master/",
+    GITHUB_REPOSITORY
+  )
+});
+pub static GITHUB_API_ENDPOINT: SyncLazy<String> = SyncLazy::new(|| {
+  format!(
+    "https://api.github.com/repos/{}/git/trees/master?recursive=1",
+    GITHUB_REPOSITORY,
+  )
+});
diff --git a/src/lib.rs b/src/lib.rs
index 2287e89..507c927 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,6 +16,7 @@
 // Copyright (C) 2022-2022 Fuwn <[email protected]>
 // SPDX-License-Identifier: GPL-3.0-only
 
+#![feature(once_cell)]
 #![deny(
   warnings,
   nonstandard_style,
diff --git a/src/structures.rs b/src/structures.rs
index 3e9b7bc..4c59d51 100644
--- a/src/structures.rs
+++ b/src/structures.rs
@@ -20,7 +20,7 @@
 
 use serde_derive::{Deserialize, Serialize};
 
-#[derive(Serialize, Deserialize)]
+#[derive(Serialize, Deserialize, Clone)]
 pub struct GitHubAPIResponse {
   pub sha:       String,
   pub url:       String,
@@ -38,7 +38,7 @@ impl Default for GitHubAPIResponse {
   }
 }
 
-#[derive(Serialize, Deserialize, Default)]
+#[derive(Serialize, Deserialize, Default, Clone)]
 pub struct GitHubAPIResponseTree {
   pub path:   String,
   pub mode:   String,
diff --git a/src/utils.rs b/src/utils.rs
index 8bb70da..333a1c0 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -16,39 +16,55 @@
 // Copyright (C) 2022-2022 Fuwn <[email protected]>
 // SPDX-License-Identifier: GPL-3.0-only
 
+use std::{lazy::SyncLazy, sync::Mutex};
+
 use worker::Cors;
 
 use crate::{constants, structures::GitHubAPIResponse};
 
+static CACHE_UNSET: SyncLazy<Mutex<bool>> = SyncLazy::new(|| Mutex::new(true));
+static CACHE_ACCESS_COUNT: SyncLazy<Mutex<usize>> =
+  SyncLazy::new(|| Mutex::new(0));
+static GITHUB_API_CACHE: SyncLazy<Mutex<GitHubAPIResponse>> =
+  SyncLazy::new(|| Mutex::new(GitHubAPIResponse::default()));
+
 /// # Errors
 /// if GitHub API is unresponsive
 pub async fn github_api(
 ) -> Result<GitHubAPIResponse, Box<dyn std::error::Error>> {
-  let mut client = reqwest::Client::new()
-    .get(constants::GITHUB_API_ENDPOINT)
-    .header(
-      "User-Agent",
-      format!("senpy-club/api-worker - {}", env!("VERGEN_GIT_SHA")),
-    );
-
-  if std::env::var("GITHUB_TOKEN").is_ok() {
-    client = client.header(
-      "Authorization",
-      format!(
-        "token {}",
-        std::env::var("GITHUB_TOKEN").unwrap_or_else(|_| "Null".to_string())
-      ),
-    );
-  }
+  if *CACHE_UNSET.lock().unwrap()
+    || *CACHE_ACCESS_COUNT.lock().unwrap() % 50 == 0
+  {
+    *CACHE_UNSET.lock().unwrap() = false;
 
-  Ok(
-    client
+    let mut client = reqwest::Client::new()
+      .get(&*constants::GITHUB_API_ENDPOINT)
+      .header(
+        "User-Agent",
+        format!("senpy-club/api-worker - {}", env!("VERGEN_GIT_SHA")),
+      );
+
+    if std::env::var("GITHUB_TOKEN").is_ok() {
+      client = client.header(
+        "Authorization",
+        format!(
+          "token {}",
+          std::env::var("GITHUB_TOKEN").unwrap_or_else(|_| "Null".to_string())
+        ),
+      );
+    }
+
+    *GITHUB_API_CACHE.lock().unwrap() = client
       .send()
       .await?
       .json::<GitHubAPIResponse>()
       .await
-      .unwrap_or_default(),
-  )
+      .unwrap_or_default();
+  }
+
+  *CACHE_ACCESS_COUNT.lock().unwrap() += 1;
+
+  Ok((*GITHUB_API_CACHE.lock().unwrap()).clone())
 }
 
 /// # Panics
@@ -79,7 +95,7 @@ pub async fn filter_images_by_language(language: &str) -> Vec<String> {
     {
       images.push(format!(
         "{}{}",
-        constants::GITHUB_USER_CONTENT,
+        *constants::GITHUB_USER_CONTENT,
         // Pound symbols to URL (percent) encoding of pound symbol because we
         // are pushing a URL, not a string
         item.path.replace('#', "%23")