From 3eaaeb1244a20e7ae28ae12f042654dcbe30d2a9 Mon Sep 17 00:00:00 2001
From: lemonsh <lemon@lemonsh.moe>
Date: Sun, 17 Jul 2022 19:15:38 +0200
Subject: [PATCH] Add message history module

---
 src/history.rs | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 src/history.rs

diff --git a/src/history.rs b/src/history.rs
new file mode 100644
index 0000000..45c4d04
--- /dev/null
+++ b/src/history.rs
@@ -0,0 +1,50 @@
+use std::collections::{HashMap, VecDeque};
+use anyhow::anyhow;
+use tokio::sync::RwLock;
+
+pub struct MessageHistory {
+    map: RwLock<HashMap<String, VecDeque<String>>>,
+    maxlen: usize
+}
+
+impl MessageHistory {
+    pub fn new(maxlen: usize) -> MessageHistory {
+        MessageHistory {
+            map: RwLock::new(HashMap::new()),
+            maxlen
+        }
+    }
+
+    pub fn max_len(&self) -> usize {
+        self.maxlen
+    }
+
+    pub async fn last_msg(&self, user: &str) -> Option<String> {
+        let map = self.map.read().await;
+        map.get(user).and_then(|d| d.get(0)).map(|s| s.to_string())
+    }
+
+    pub async fn last_msgs(&self, user: &str, count: usize) -> Option<Vec<String>> {
+        let map = self.map.read().await;
+        if let Some(deque) = map.get(user) {
+            let count = if deque.len() < count { deque.len() } else {count};
+            Some(deque.range(..count).rev().map(ToString::to_string).collect())
+        } else {
+            None
+        }
+    }
+
+    pub async fn add_message(&self, user: &str, message: &str) {
+        let mut map = self.map.write().await;
+        if let Some(deque) = map.get_mut(user) {
+            if deque.len() == self.maxlen {
+                deque.remove(deque.len()-1);
+            }
+            deque.push_front(message.to_string());
+        } else {
+            let mut deque = VecDeque::with_capacity(self.maxlen);
+            deque.push_front(message.to_string());
+            map.insert(user.to_string(), deque);
+        }
+    }
+}
\ No newline at end of file