Optimize json loading, filter and reduce

Cargo.lock

@@ -1229,7 +1229,7 @@ dependencies = [
 
 [[package]]
 name = "sticker-usage-analyzer"
-version = "0.1.0"
+version = "1.0.0"
 dependencies = [
  "chrono",
  "maud",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sticker-usage-analyzer"
-version = "0.1.0"
+version = "1.0.0"
 edition = "2021"
 
 [dependencies]

src/main.rs

@@ -1,6 +1,6 @@
 use maud::{html, Markup, DOCTYPE};
 use rocket::{Rocket,Build,launch,get,routes,fs::{FileServer}};
-use std::collections::HashMap;
+use std::{fs::OpenOptions, io::BufReader, collections::HashMap};
 use chrono::prelude::*;
 
 
@@ -105,36 +105,23 @@ fn rocket() -> Rocket<Build> {
 
 #[get("/")]
 fn index() -> Markup {
-    println!("Parsing JSON... (this can take a moment)");
     let tg_export_result: Chat = serde_json::from_reader(
-        std::fs::OpenOptions::new().read(true).open("./result.json").expect("Could not open ./result.json")
+        BufReader::new(OpenOptions::new().read(true).open("./result.json").expect("Could not open ./result.json"))
     ).expect("Could not parse result.json");
-    println!("Done!");
 
-    let mut messages: Vec<ScoredChatMessage> = tg_export_result.messages.into_iter().filter(|m| {
-        return if let Some(media_type) = &m.media_type {
-            *media_type == MediaType::Sticker
-        } else {
-            false
-        }
-    }).fold(HashMap::new(), |mut acc: HashMap<String, ScoredChatMessage>, message| {
-        let file = message.file.as_ref().expect("No file").to_owned();
-        if acc.contains_key(&file) {
-            if let Some(scored_chat_message) = acc.get_mut(&file) {
-                let message_date = message.date_unixtime.parse().expect("Could not parse date_unixtime");
-                if scored_chat_message.last_used < message_date {
-                    scored_chat_message.last_used = message_date;
-                }
-                scored_chat_message.times = scored_chat_message.times + 1;
+    let mut messages: Vec<ScoredChatMessage> = tg_export_result.messages.into_iter()
+        .filter(|m| matches!(m.media_type, Some(MediaType::Sticker)))
+        .fold(HashMap::new(), |mut acc: HashMap<String, ScoredChatMessage>, message| {
+            if let Some(ref file) = message.file {
+                let message_date = (&message.date_unixtime).parse().expect("Could not parse date_unixtime");
+                let entry = acc.entry(file.to_owned()).or_insert_with(|| ScoredChatMessage::from(message));
+                entry.last_used = entry.last_used.max(message_date);
+                entry.times += 1;
             }
-        } else {
-            acc.insert(file, ScoredChatMessage::from(message));
-        }
-
-        acc
-    })
-    .into_values()
-    .collect();
+            acc
+        })
+        .into_values()
+        .collect();
 
     messages.sort_by(|a, b| b.times.cmp(&a.times));