fips/src/config.rs

//! FIPS Configuration System
//!
//! Loads configuration from YAML files with a cascading priority system:
//! 1. `./fips.yaml` (current directory - highest priority)
//! 2. `~/.config/fips/fips.yaml` (user config directory)
//! 3. `/etc/fips/fips.yaml` (system - lowest priority)
//!
//! Values from higher priority files override those from lower priority files.
//!
//! # YAML Structure
//!
//! The YAML structure mirrors the sysctl-style paths in the architecture docs.
//! For example, `node.identity.nsec` in the docs corresponds to:
//!
//! ```yaml
//! node:
//!   identity:
//!     nsec: "nsec1..."
//! ```

use crate::{Identity, IdentityError};
use serde::{Deserialize, Serialize};
use std::path::{Path, PathBuf};
use thiserror::Error;

/// Default config filename.
const CONFIG_FILENAME: &str = "fips.yaml";

/// Errors that can occur during configuration loading.
#[derive(Debug, Error)]
pub enum ConfigError {
    #[error("failed to read config file {path}: {source}")]
    ReadFile {
        path: PathBuf,
        source: std::io::Error,
    },

    #[error("failed to parse config file {path}: {source}")]
    ParseYaml {
        path: PathBuf,
        source: serde_yaml::Error,
    },

    #[error("identity error: {0}")]
    Identity(#[from] IdentityError),
}

/// Identity configuration (`node.identity.*`).
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct IdentityConfig {
    /// Secret key in nsec (bech32) or hex format (`node.identity.nsec`).
    /// If not specified, a new keypair will be generated.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub nsec: Option<String>,
}

/// Node configuration (`node.*`).
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct NodeConfig {
    /// Identity configuration (`node.identity.*`).
    #[serde(default)]
    pub identity: IdentityConfig,

    /// Leaf-only mode (`node.leaf_only`).
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub leaf_only: bool,
}

/// Default TUN device name.
const DEFAULT_TUN_NAME: &str = "fips0";

/// Default TUN MTU (IPv6 minimum).
const DEFAULT_TUN_MTU: u16 = 1280;

/// TUN interface configuration (`tun.*`).
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct TunConfig {
    /// Enable TUN interface (`tun.enabled`).
    #[serde(default, skip_serializing_if = "std::ops::Not::not")]
    pub enabled: bool,

    /// TUN device name (`tun.name`). Defaults to "fips0".
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub name: Option<String>,

    /// TUN MTU (`tun.mtu`). Defaults to 1280 (IPv6 minimum).
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub mtu: Option<u16>,

}

impl TunConfig {
    /// Get the TUN device name, using default if not configured.
    pub fn name(&self) -> &str {
        self.name.as_deref().unwrap_or(DEFAULT_TUN_NAME)
    }

    /// Get the TUN MTU, using default if not configured.
    pub fn mtu(&self) -> u16 {
        self.mtu.unwrap_or(DEFAULT_TUN_MTU)
    }
}

/// Root configuration structure.
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct Config {
    /// Node configuration (`node.*`).
    #[serde(default)]
    pub node: NodeConfig,

    /// TUN interface configuration (`tun.*`).
    #[serde(default)]
    pub tun: TunConfig,
}

impl Config {
    /// Create a new empty configuration.
    pub fn new() -> Self {
        Self::default()
    }

    /// Load configuration from the standard search paths.
    ///
    /// Files are loaded in reverse priority order and merged:
    /// 1. `/etc/fips/fips.yaml` (loaded first, lowest priority)
    /// 2. `~/.config/fips/fips.yaml` (user config)
    /// 3. `./fips.yaml` (loaded last, highest priority)
    ///
    /// Returns a tuple of (config, paths_loaded) where paths_loaded contains
    /// the paths that were successfully loaded.
    pub fn load() -> Result<(Self, Vec<PathBuf>), ConfigError> {
        let search_paths = Self::search_paths();
        Self::load_from_paths(&search_paths)
    }

    /// Load configuration from specific paths.
    ///
    /// Paths are processed in order, with later paths overriding earlier ones.
    pub fn load_from_paths(paths: &[PathBuf]) -> Result<(Self, Vec<PathBuf>), ConfigError> {
        let mut config = Config::default();
        let mut loaded_paths = Vec::new();

        for path in paths {
            if path.exists() {
                let file_config = Self::load_file(path)?;
                config.merge(file_config);
                loaded_paths.push(path.clone());
            }
        }

        Ok((config, loaded_paths))
    }

    /// Load configuration from a single file.
    pub fn load_file(path: &Path) -> Result<Self, ConfigError> {
        let contents = std::fs::read_to_string(path).map_err(|e| ConfigError::ReadFile {
            path: path.to_path_buf(),
            source: e,
        })?;

        serde_yaml::from_str(&contents).map_err(|e| ConfigError::ParseYaml {
            path: path.to_path_buf(),
            source: e,
        })
    }

    /// Get the standard search paths in priority order (lowest to highest).
    pub fn search_paths() -> Vec<PathBuf> {
        let mut paths = Vec::new();

        // System config (lowest priority)
        paths.push(PathBuf::from("/etc/fips").join(CONFIG_FILENAME));

        // User config directory
        if let Some(config_dir) = dirs::config_dir() {
            paths.push(config_dir.join("fips").join(CONFIG_FILENAME));
        }

        // Home directory (legacy location)
        if let Some(home_dir) = dirs::home_dir() {
            paths.push(home_dir.join(".fips.yaml"));
        }

        // Current directory (highest priority)
        paths.push(PathBuf::from(".").join(CONFIG_FILENAME));

        paths
    }

    /// Merge another configuration into this one.
    ///
    /// Values from `other` override values in `self` when present.
    pub fn merge(&mut self, other: Config) {
        // Merge node.identity section
        if other.node.identity.nsec.is_some() {
            self.node.identity.nsec = other.node.identity.nsec;
        }
        // Merge node.leaf_only
        if other.node.leaf_only {
            self.node.leaf_only = true;
        }
        // Merge tun section
        if other.tun.enabled {
            self.tun.enabled = true;
        }
        if other.tun.name.is_some() {
            self.tun.name = other.tun.name;
        }
        if other.tun.mtu.is_some() {
            self.tun.mtu = other.tun.mtu;
        }
    }

    /// Create an Identity from this configuration.
    ///
    /// If an nsec is configured, uses that to create the identity.
    /// Otherwise, generates a new random identity.
    pub fn create_identity(&self) -> Result<Identity, ConfigError> {
        match &self.node.identity.nsec {
            Some(nsec) => Ok(Identity::from_secret_str(nsec)?),
            None => Ok(Identity::generate()),
        }
    }

    /// Check if an identity is configured (vs. will be generated).
    pub fn has_identity(&self) -> bool {
        self.node.identity.nsec.is_some()
    }

    /// Check if leaf-only mode is configured.
    pub fn is_leaf_only(&self) -> bool {
        self.node.leaf_only
    }

    /// Serialize this configuration to YAML.
    pub fn to_yaml(&self) -> Result<String, serde_yaml::Error> {
        serde_yaml::to_string(self)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;
    use tempfile::TempDir;

    #[test]
    fn test_empty_config() {
        let config = Config::new();
        assert!(config.node.identity.nsec.is_none());
        assert!(!config.has_identity());
    }

    #[test]
    fn test_parse_yaml_with_nsec() {
        let yaml = r#"
node:
  identity:
    nsec: nsec1qyqsqypqxqszqg9qyqsqypqxqszqg9qyqsqypqxqszqg9qyqsqypqxfnm5g9
"#;
        let config: Config = serde_yaml::from_str(yaml).unwrap();
        assert!(config.node.identity.nsec.is_some());
        assert!(config.has_identity());
    }

    #[test]
    fn test_parse_yaml_with_hex() {
        let yaml = r#"
node:
  identity:
    nsec: "0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20"
"#;
        let config: Config = serde_yaml::from_str(yaml).unwrap();
        assert!(config.node.identity.nsec.is_some());

        let identity = config.create_identity().unwrap();
        assert!(!identity.npub().is_empty());
    }

    #[test]
    fn test_parse_yaml_empty() {
        let yaml = "";
        let config: Config = serde_yaml::from_str(yaml).unwrap();
        assert!(config.node.identity.nsec.is_none());
    }

    #[test]
    fn test_parse_yaml_partial() {
        let yaml = r#"
node:
  identity: {}
"#;
        let config: Config = serde_yaml::from_str(yaml).unwrap();
        assert!(config.node.identity.nsec.is_none());
    }

    #[test]
    fn test_merge_configs() {
        let mut base = Config::new();
        base.node.identity.nsec = Some("base_nsec".to_string());

        let mut override_config = Config::new();
        override_config.node.identity.nsec = Some("override_nsec".to_string());

        base.merge(override_config);
        assert_eq!(
            base.node.identity.nsec,
            Some("override_nsec".to_string())
        );
    }

    #[test]
    fn test_merge_preserves_base_when_override_empty() {
        let mut base = Config::new();
        base.node.identity.nsec = Some("base_nsec".to_string());

        let override_config = Config::new();

        base.merge(override_config);
        assert_eq!(base.node.identity.nsec, Some("base_nsec".to_string()));
    }

    #[test]
    fn test_create_identity_from_nsec() {
        let mut config = Config::new();
        config.node.identity.nsec = Some(
            "0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20".to_string(),
        );

        let identity = config.create_identity().unwrap();
        assert!(!identity.npub().is_empty());
    }

    #[test]
    fn test_create_identity_generates_new() {
        let config = Config::new();
        let identity = config.create_identity().unwrap();
        assert!(!identity.npub().is_empty());
    }

    #[test]
    fn test_load_from_file() {
        let temp_dir = TempDir::new().unwrap();
        let config_path = temp_dir.path().join("fips.yaml");

        let yaml = r#"
node:
  identity:
    nsec: "0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20"
"#;
        fs::write(&config_path, yaml).unwrap();

        let config = Config::load_file(&config_path).unwrap();
        assert!(config.node.identity.nsec.is_some());
    }

    #[test]
    fn test_load_from_paths_merges() {
        let temp_dir = TempDir::new().unwrap();

        // Create two config files
        let low_priority = temp_dir.path().join("low.yaml");
        let high_priority = temp_dir.path().join("high.yaml");

        fs::write(
            &low_priority,
            r#"
node:
  identity:
    nsec: "low_priority_nsec"
"#,
        )
        .unwrap();

        fs::write(
            &high_priority,
            r#"
node:
  identity:
    nsec: "high_priority_nsec"
"#,
        )
        .unwrap();

        let paths = vec![low_priority.clone(), high_priority.clone()];
        let (config, loaded) = Config::load_from_paths(&paths).unwrap();

        assert_eq!(loaded.len(), 2);
        assert_eq!(
            config.node.identity.nsec,
            Some("high_priority_nsec".to_string())
        );
    }

    #[test]
    fn test_load_skips_missing_files() {
        let temp_dir = TempDir::new().unwrap();
        let existing = temp_dir.path().join("exists.yaml");
        let missing = temp_dir.path().join("missing.yaml");

        fs::write(
            &existing,
            r#"
node:
  identity:
    nsec: "existing_nsec"
"#,
        )
        .unwrap();

        let paths = vec![missing, existing.clone()];
        let (config, loaded) = Config::load_from_paths(&paths).unwrap();

        assert_eq!(loaded.len(), 1);
        assert_eq!(loaded[0], existing);
        assert_eq!(config.node.identity.nsec, Some("existing_nsec".to_string()));
    }

    #[test]
    fn test_search_paths_includes_expected() {
        let paths = Config::search_paths();

        // Should include current directory
        assert!(paths.iter().any(|p| p.ends_with("fips.yaml")));

        // Should include /etc/fips
        assert!(paths
            .iter()
            .any(|p| p.starts_with("/etc/fips") && p.ends_with("fips.yaml")));
    }

    #[test]
    fn test_to_yaml() {
        let mut config = Config::new();
        config.node.identity.nsec = Some("test_nsec".to_string());

        let yaml = config.to_yaml().unwrap();
        assert!(yaml.contains("node:"));
        assert!(yaml.contains("identity:"));
        assert!(yaml.contains("nsec:"));
        assert!(yaml.contains("test_nsec"));
    }

    #[test]
    fn test_to_yaml_empty_nsec_omitted() {
        let config = Config::new();
        let yaml = config.to_yaml().unwrap();

        // Empty nsec should not be serialized
        assert!(!yaml.contains("nsec:"));
    }
}