Update Cargo.lock

.gitignore

@@ -1,18 +1 @@
-# ---> Rust
-# Generated by Cargo
-# will have compiled files and executables
-debug/
-target/
-
-# These are backup files generated by rustfmt
-**/*.rs.bk
-
-# MSVC Windows builds of rustc generate these, which store debugging information
-*.pdb
-
-# RustRover
-#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
-#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
-#  and can be added to the global gitignore or merged into this file.  For a more nuclear
-#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
-#.idea/
+/target

AGENTS.md

@@ -0,0 +1,122 @@
+# Agent Guidelines for opencode-testing
+
+This is a Rust project using Edition 2024.
+
+## Build/Test Commands
+
+```bash
+# Build the project
+cargo build
+
+# Build for release
+cargo build --release
+
+# Run the application
+cargo run
+
+# Run all tests
+cargo test
+
+# Run a specific test (e.g., test named `test_calculate_area`)
+cargo test test_calculate_area
+
+# Run tests in a specific module
+cargo test module_name::
+
+# Run with output visible
+cargo test -- --nocapture
+
+# Check for compilation errors without building
+cargo check
+
+# Watch mode for development (requires cargo-watch)
+cargo watch -x "run"
+```
+
+## Code Quality Commands
+
+```bash
+# Format code (rustfmt)
+cargo fmt
+
+# Check formatting without making changes
+cargo fmt -- --check
+
+# Run clippy lints
+cargo clippy
+
+# Run clippy with all features and warnings as errors
+cargo clippy --all-features -- -D warnings
+```
+
+## Code Style Guidelines
+
+### Formatting
+- Use `cargo fmt` with default settings
+- Max line width: 100 characters (default)
+- Use 4 spaces for indentation (default)
+- Trailing commas in multi-line lists
+
+### Naming Conventions
+- Variables, functions, modules: `snake_case`
+- Types (structs, enums, traits): `CamelCase`
+- Constants, statics: `SCREAMING_SNAKE_CASE`
+- Lifetimes: `'lowercase`
+- Generic type parameters: `CamelCase` (single uppercase letter preferred: `T`, `K`, `V`)
+- Macros: `snake_case!`
+
+### Import Organization
+Group imports in this order, separated by blank lines:
+1. Standard library imports (`std::`, `core::`, `alloc::`)
+2. External crate imports
+3. Internal crate imports (`crate::`)
+4. Super module imports (`super::`)
+5. Current module imports (`self::`)
+
+Use `use` statements not `extern crate`.
+
+### Types and Type Safety
+- Prefer explicit types over `impl Trait` in public APIs
+- Use `Option<T>` and `Result<T, E>` for fallible operations
+- Avoid `unwrap()` and `expect()` in production code; handle errors properly
+- Use `?` operator for error propagation
+- Prefer `&str` over `&String`, `&[T]` over `&Vec<T>` for function parameters
+
+### Error Handling
+- Define custom error types using `thiserror` or `enum` for complex error cases
+- Use `anyhow` for application code error handling
+- Propagate errors with `?` operator
+- Provide context with `map_err()` when needed
+
+### Functions
+- Keep functions small and focused on a single task
+- Max 5-7 parameters; use structs for more complex parameter sets
+- Document public functions with `///` doc comments
+- Use early returns to reduce nesting
+
+### Comments and Documentation
+- Use `//` for inline comments
+- Use `///` for public API documentation
+- Use `//!` for module-level documentation
+- Document panics, unsafe code, and complex algorithms
+
+### Unsafe Code
+- Avoid unsafe code unless absolutely necessary
+- Document all safety invariants with `// SAFETY:` comments
+- Keep unsafe blocks as small as possible
+
+### Testing
+- Write unit tests in the same file as the code: `#[cfg(test)]` module
+- Use descriptive test names: `test_<scenario>_<expected_behavior>`
+- Use `assert!`, `assert_eq!`, `assert_ne!` for assertions
+- Organize tests with submodules for different scenarios
+
+### Memory Management
+- Prefer ownership and borrowing over cloning when possible
+- Use `.clone()` explicitly when needed
+- Consider `Cow<'_, T>` for data that may be borrowed or owned
+
+### Performance
+- Avoid premature optimization; write clear code first
+- Use iterators instead of loops when appropriate
+- Profile before optimizing

Cargo.lock

@@ -0,0 +1,249 @@
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Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "todo_app"
+version = "0.1.0"
+edition = "2026"
+authors = ["Jakob Rönnbäck <jakob@rowanbrook.net>"]
+description = "A simple command-line todo list manager"
+license = "MIT"
+repository = "https://gitea.rowanbrook.net/jakob/Learn-Rust-through-projects.git"
+keywords = ["cli", "todo", "productivity"]
+categories = ["command-line-utilities"]
+
+[[bin]]
+name = "todo"
+path = "src/main.rs"
+
+[dependencies]
+clap = { version = "4.0.0", features = ["derive"] }
+serde = { version = "1.0.130", features = ["derive"] }
+serde_json = "1.0.130"

LICENSE

@@ -1,18 +0,0 @@
-MIT License
-
-Copyright (c) 2026 jakob
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of this software and 
-associated documentation files (the "Software"), to deal in the Software without restriction, including 
-without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
-copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the 
-following conditions:
-
-The above copyright notice and this permission notice shall be included in all copies or substantial 
-portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT 
-LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO 
-EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER 
-IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE 
-USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -1,3 +0,0 @@
-# Learn-Rust-through-projects
-
-Example code from the book "Learn Rust through projects" by Julia Lornfield

src/main.rs

@@ -0,0 +1,140 @@
+use clap::{Parser, Subcommand};
+use serde::{Deserialize, Serialize};
+use std::fmt;
+use std::fs;
+use std::path::Path;
+
+#[derive(Parser)]
+#[command(name = "todo")]
+#[command(about = "A simple todo list manager")]
+struct Cli {
+    #[command(subcommand)]
+    command: Commands,
+}
+
+#[derive(Subcommand)]
+enum Commands {
+    Add { task: String },
+    List,
+    Complete { id: usize },
+    Remove { id: usize },
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+struct Task {
+    id: usize,
+    description: String,
+    completed: bool,
+}
+
+#[derive(Serialize, Deserialize, Debug)]
+struct TodoList {
+    tasks: Vec<Task>,
+    next_id: usize,
+}
+
+#[derive(Debug)]
+enum TodoError {
+    FileError(String),
+    ParseError(String),
+    TaskNotFound(usize),
+    InvalidInput(String),
+}
+
+impl fmt::Display for TodoError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TodoError::FileError(msg) => write!(f, "File error: {}", msg),
+            TodoError::ParseError(msg) => write!(f, "Parse error: {}", msg),
+            TodoError::TaskNotFound(id) => write!(f, "Task {} not found", id),
+            TodoError::InvalidInput(msg) => write!(f, "Invalid input: {}", msg),
+        }
+    }
+}
+
+impl std::error::Error for TodoError {}
+
+impl TodoList {
+    fn new() -> Self {
+        TodoList {
+            tasks: Vec::new(),
+            next_id: 1,
+        }
+    }
+
+    fn load_from_file(filename: &str) -> Result<Self, Box<dyn std::error::Error>> {
+        if Path::new(filename).exists() {
+            let contents = fs::read_to_string(filename)?;
+            let todo_list = serde_json::from_str(&contents)?;
+            Ok(todo_list)
+        } else {
+            Ok(TodoList::new())
+        }
+    }
+
+    fn save_to_file(&self, filename: &str) -> Result<(), Box<dyn std::error::Error>> {
+        let json = serde_json::to_string_pretty(self)?;
+        fs::write(filename, json)?;
+        Ok(())
+    }
+
+    fn add_task(&mut self, description: String) -> Result<(), TodoError> {
+        if description.trim().is_empty() {
+            return Err(TodoError::InvalidInput(
+                "Task description cannot be empty".to_string(),
+            ));
+        }
+
+        let task = Task {
+            id: self.next_id,
+            description,
+            completed: false,
+        };
+
+        self.tasks.push(task);
+        self.next_id += 1;
+        Ok(())
+    }
+
+    fn complete_task(&mut self, id: usize) -> Result<(), TodoError> {
+        match self.tasks.iter_mut().find(|task| task.id == id) {
+            Some(task) => {
+                task.completed = true;
+                Ok(())
+            }
+            None => Err(TodoError::TaskNotFound(id)),
+        }
+    }
+}
+
+fn main() {
+    let cli = Cli::parse();
+
+    if let Err(e) = run_command(cli) {
+        eprintln!("Error: {}", e);
+        std::process::exit(1);
+    }
+}
+
+fn run_command(cli: Cli) -> Result<(), TodoError> {
+    let mut todo_list =
+        TodoList::load_from_file("tasks.json").map_err(|e| TodoError::FileError(e.to_string()))?;
+
+    match cli.command {
+        Commands::Add { task } => {
+            todo_list.add_task(task)?;
+            println!("Task added successfully");
+        }
+        Commands::Complete { id } => {
+            todo_list.complete_task(id)?;
+            println!("Task {} marked as complete", id);
+        }
+        _ => {} // Handle other commands
+    }
+
+    todo_list
+        .save_to_file("todo.json")
+        .map_err(|e| TodoError::FileError(e.to_string()))?;
+
+    Ok(())
+}