feat(day34): add file I/O + JSON todo lesson

Author: 0xBoji

Cargo.toml

@@ -9,6 +9,7 @@ edition = "2021"
 rayon = "1.5"
 tokio = { version = "1", features = ["full"] }
 serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
 actix-web = "4"
 axum = "0.7.7"
 # # for actix crates
@@ -18,4 +19,4 @@ axum = "0.7.7"
 utoipa = { version = "4.2.3", features = ["axum_extras"] }
 utoipa-swagger-ui = { version = "7.1.0", features = ["axum"] }
 tokio-postgres = "0.7"
-deadpool-postgres = "0.10"
+deadpool-postgres = "0.10"

src/day34_to_day36/mod.rs

@@ -0,0 +1,8 @@
+pub mod todo_json;
+
+pub fn run() {
+    println!("Days 34-36: File I/O and JSON");
+    if let Err(err) = todo_json::run() {
+        eprintln!("Todo JSON lesson failed: {err}");
+    }
+}

src/day34_to_day36/todo_json.rs

@@ -0,0 +1,87 @@
+use serde::{Deserialize, Serialize};
+use std::error::Error;
+use std::fs;
+use std::path::Path;
+
+const TODO_FILE: &str = "data/day34_todo.json";
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+struct TodoItem {
+    id: u32,
+    title: String,
+    done: bool,
+}
+
+#[derive(Debug, Serialize, Deserialize, Default)]
+struct TodoStore {
+    items: Vec<TodoItem>,
+}
+
+impl TodoStore {
+    fn add_task(&mut self, title: impl Into<String>) {
+        let next_id = self.items.last().map_or(1, |item| item.id + 1);
+        self.items.push(TodoItem {
+            id: next_id,
+            title: title.into(),
+            done: false,
+        });
+    }
+
+    fn mark_done(&mut self, id: u32) -> bool {
+        if let Some(item) = self.items.iter_mut().find(|item| item.id == id) {
+            item.done = true;
+            true
+        } else {
+            false
+        }
+    }
+
+    fn load(path: &Path) -> Result<Self, Box<dyn Error>> {
+        if !path.exists() {
+            return Ok(Self::default());
+        }
+
+        let content = fs::read_to_string(path)?;
+        let store = serde_json::from_str(&content)?;
+        Ok(store)
+    }
+
+    fn save(&self, path: &Path) -> Result<(), Box<dyn Error>> {
+        if let Some(parent) = path.parent() {
+            fs::create_dir_all(parent)?;
+        }
+
+        let json = serde_json::to_string_pretty(self)?;
+        fs::write(path, json)?;
+        Ok(())
+    }
+}
+
+pub fn run() -> Result<(), Box<dyn Error>> {
+    println!("\nLesson: Build a tiny Todo with File I/O + JSON");
+    println!("Data file: {TODO_FILE}");
+
+    let path = Path::new(TODO_FILE);
+    let mut store = TodoStore::load(path)?;
+
+    if store.items.is_empty() {
+        store.add_task("Read ownership chapter again");
+        store.add_task("Practice borrowing with 3 small exercises");
+    }
+
+    if let Some(first_open_id) = store.items.iter().find(|item| !item.done).map(|item| item.id) {
+        store.mark_done(first_open_id);
+    }
+
+    store.save(path)?;
+
+    println!("Current tasks:");
+    for item in &store.items {
+        let status = if item.done { "done" } else { "todo" };
+        println!("- [{}] #{} {}", status, item.id, item.title);
+    }
+
+    println!("Saved to {}", path.display());
+    Ok(())
+}
+

src/main.rs

@@ -31,6 +31,9 @@ pub mod day28_to_day30;
 //Day 31 to day 33
 pub mod day31_to_day33;
 
+//Day 34 to day 36
+pub mod day34_to_day36;
+
 fn main() {
     // day01_to_day03::run();
     // day04_to_day06::run();
@@ -42,6 +45,7 @@ fn main() {
     // day22_to_day24::run();
     // day25_to_day27::run();
     // day28_to_day30::run();
-    day31_to_day33::run();
+    // day31_to_day33::run();
+    day34_to_day36::run();
 
 }