Add CalDAV dependencies and secure configuration

- Added comprehensive CalDAV/calendar dependencies:
  - reqwest for HTTP requests
  - ical for calendar parsing
  - chrono for date/time handling
  - serde for serialization
  - anyhow/thiserror for error handling
  - uuid for event generation
- Implemented secure config management:
  - dotenvy for environment variable loading
  - base64 for Basic Auth encoding
  - .env.example template for development
  - .gitignore updated to exclude secret files
- Created config.rs module with extensive documentation:
  - CalDAVConfig struct for server credentials
  - Environment-based configuration loading
  - HTTP Basic Auth helper methods
  - Comprehensive error handling
  - Full rustdoc documentation with examples

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/config.rs

@@ -0,0 +1,182 @@
+use serde::{Deserialize, Serialize};
+use std::env;
+
+/// Configuration for CalDAV server connection and authentication.
+/// 
+/// This struct holds all the necessary information to connect to a CalDAV server,
+/// including server URL, credentials, and optional collection paths.
+/// 
+/// # Security Note
+/// 
+/// The password field contains sensitive information and should be handled carefully.
+/// This struct implements `Debug` but in production, consider implementing a custom
+/// `Debug` that masks the password field.
+/// 
+/// # Example
+/// 
+/// ```rust
+/// use crate::config::CalDAVConfig;
+/// 
+/// // Load configuration from environment variables
+/// let config = CalDAVConfig::from_env()?;
+/// 
+/// // Use the configuration for HTTP requests
+/// let auth_header = format!("Basic {}", config.get_basic_auth());
+/// ```
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CalDAVConfig {
+    /// The base URL of the CalDAV server (e.g., "https://caldav.example.com/dav/")
+    pub server_url: String,
+    
+    /// Username for authentication with the CalDAV server
+    pub username: String,
+    
+    /// Password for authentication with the CalDAV server
+    /// 
+    /// **Security Note**: This contains sensitive information
+    pub password: String,
+    
+    /// Optional path to the calendar collection on the server
+    /// 
+    /// If not provided, the client will need to discover available calendars
+    /// through CalDAV PROPFIND requests
+    pub calendar_path: Option<String>,
+    
+    /// Optional path to the tasks/todo collection on the server
+    /// 
+    /// Some CalDAV servers store tasks separately from calendar events
+    pub tasks_path: Option<String>,
+}
+
+impl CalDAVConfig {
+    /// Creates a new CalDAVConfig by loading values from environment variables.
+    /// 
+    /// This method will attempt to load a `.env` file from the current directory
+    /// and then read the following required environment variables:
+    /// 
+    /// - `CALDAV_SERVER_URL`: The CalDAV server base URL
+    /// - `CALDAV_USERNAME`: Username for authentication
+    /// - `CALDAV_PASSWORD`: Password for authentication
+    /// 
+    /// Optional environment variables:
+    /// 
+    /// - `CALDAV_CALENDAR_PATH`: Path to calendar collection
+    /// - `CALDAV_TASKS_PATH`: Path to tasks collection
+    /// 
+    /// # Errors
+    /// 
+    /// Returns `ConfigError::MissingVar` if any required environment variable
+    /// is not set or cannot be read.
+    /// 
+    /// # Example
+    /// 
+    /// ```rust
+    /// use crate::config::CalDAVConfig;
+    /// 
+    /// match CalDAVConfig::from_env() {
+    ///     Ok(config) => {
+    ///         println!("Loaded config for server: {}", config.server_url);
+    ///     }
+    ///     Err(e) => {
+    ///         eprintln!("Failed to load config: {}", e);
+    ///     }
+    /// }
+    /// ```
+    pub fn from_env() -> Result<Self, ConfigError> {
+        // Attempt to load .env file, but don't fail if it doesn't exist
+        dotenvy::dotenv().ok();
+
+        let server_url = env::var("CALDAV_SERVER_URL")
+            .map_err(|_| ConfigError::MissingVar("CALDAV_SERVER_URL".to_string()))?;
+
+        let username = env::var("CALDAV_USERNAME")
+            .map_err(|_| ConfigError::MissingVar("CALDAV_USERNAME".to_string()))?;
+
+        let password = env::var("CALDAV_PASSWORD")
+            .map_err(|_| ConfigError::MissingVar("CALDAV_PASSWORD".to_string()))?;
+
+        // Optional paths - it's fine if these are not set
+        let calendar_path = env::var("CALDAV_CALENDAR_PATH").ok();
+        let tasks_path = env::var("CALDAV_TASKS_PATH").ok();
+
+        Ok(CalDAVConfig {
+            server_url,
+            username,
+            password,
+            calendar_path,
+            tasks_path,
+        })
+    }
+
+    /// Generates a Base64-encoded string for HTTP Basic Authentication.
+    /// 
+    /// This method combines the username and password in the format
+    /// `username:password` and encodes it using Base64, which is the
+    /// standard format for the `Authorization: Basic` HTTP header.
+    /// 
+    /// # Returns
+    /// 
+    /// A Base64-encoded string that can be used directly in the
+    /// `Authorization` header: `Authorization: Basic <returned_value>`
+    /// 
+    /// # Example
+    /// 
+    /// ```rust
+    /// use crate::config::CalDAVConfig;
+    /// 
+    /// let config = CalDAVConfig {
+    ///     server_url: "https://example.com".to_string(),
+    ///     username: "user".to_string(),
+    ///     password: "pass".to_string(),
+    ///     calendar_path: None,
+    ///     tasks_path: None,
+    /// };
+    /// 
+    /// let auth_value = config.get_basic_auth();
+    /// let auth_header = format!("Basic {}", auth_value);
+    /// ```
+    pub fn get_basic_auth(&self) -> String {
+        let credentials = format!("{}:{}", self.username, self.password);
+        base64::encode(&credentials)
+    }
+}
+
+/// Errors that can occur when loading or using CalDAV configuration.
+#[derive(Debug, thiserror::Error)]
+pub enum ConfigError {
+    /// A required environment variable is missing or cannot be read.
+    /// 
+    /// This error occurs when calling `CalDAVConfig::from_env()` and one of the
+    /// required environment variables (`CALDAV_SERVER_URL`, `CALDAV_USERNAME`,
+    /// or `CALDAV_PASSWORD`) is not set.
+    #[error("Missing environment variable: {0}")]
+    MissingVar(String),
+    
+    /// The configuration contains invalid or malformed values.
+    /// 
+    /// This could include malformed URLs, invalid authentication credentials,
+    /// or other configuration issues that prevent proper CalDAV operation.
+    #[error("Invalid configuration: {0}")]
+    Invalid(String),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::env;
+
+    #[test]
+    fn test_basic_auth_encoding() {
+        let config = CalDAVConfig {
+            server_url: "https://example.com".to_string(),
+            username: "testuser".to_string(),
+            password: "testpass".to_string(),
+            calendar_path: None,
+            tasks_path: None,
+        };
+
+        let auth = config.get_basic_auth();
+        let expected = base64::encode("testuser:testpass");
+        assert_eq!(auth, expected);
+    }
+}

src/main.rs

@@ -1,6 +1,8 @@
 use yew::prelude::*;
 
 mod app;
+mod config;
+
 use app::App;
 
 fn main() {