rlg 0.0.10

// config.rs
// Copyright © 2024-2026 RustLogs (RLG). All rights reserved.
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

//! TOML-based configuration: loading, validation, diffing, and hot-reload.
//!
//! Load from a file with [`Config::load`][crate::config::Config::load],
//! or build programmatically via
//! [`Config::default`][crate::config::Config::default] and
//! [`Config::set`][crate::config::Config::set]. Serialize back to TOML
//! with [`Config::save_to_file`][crate::config::Config::save_to_file].
//!
//! Enable the `tokio` feature for async loading and file-watcher hot-reload.

use crate::LogLevel;
use config::{
    Config as ConfigSource, ConfigError as SourceConfigError,
    File as ConfigFile,
};
use envy;
#[cfg(feature = "tokio")]
use notify::{Event, EventKind, RecursiveMode, Watcher};
use parking_lot::RwLock;
use serde::{Deserialize, Serialize};
use std::{
    collections::HashMap,
    env, fmt,
    fs::{self, OpenOptions},
    num::NonZeroU64,
    path::{Path, PathBuf},
    str::FromStr,
    sync::Arc,
};
use thiserror::Error;

#[cfg(feature = "tokio")]
use tokio::fs::File;
#[cfg(feature = "tokio")]
use tokio::io::AsyncReadExt;
#[cfg(feature = "tokio")]
use tokio::sync::mpsc;

const CURRENT_CONFIG_VERSION: &str = "1.0";

/// Configuration error variants.
#[derive(Debug, Error)]
pub enum ConfigError {
    /// Failed to parse an environment variable.
    #[error("Environment variable parse error: {0}")]
    EnvVarParseError(#[from] envy::Error),

    /// Failed to parse the configuration file.
    #[error("Configuration parsing error: {0}")]
    ConfigParseError(#[from] SourceConfigError),

    /// The provided config file path is invalid or inaccessible.
    #[error("Invalid file path: {0}")]
    InvalidFilePath(String),

    /// File read failed.
    #[error("File read error: {0}")]
    FileReadError(String),

    /// File write failed.
    #[error("File write error: {0}")]
    FileWriteError(String),

    /// Validation failed for a configuration field.
    #[error("Configuration validation error: {0}")]
    ValidationError(String),

    /// Config file version does not match the expected version.
    #[error("Configuration version error: {0}")]
    VersionError(String),

    /// A required field is missing from the configuration.
    #[error("Missing required field: {0}")]
    MissingFieldError(String),

    /// File watcher setup failed (requires `tokio` feature).
    #[cfg(feature = "tokio")]
    #[error("Watcher error: {0}")]
    WatcherError(#[from] notify::Error),
}

impl From<crate::commons::config::ConfigError> for ConfigError {
    fn from(err: crate::commons::config::ConfigError) -> Self {
        Self::ValidationError(err.to_string())
    }
}

/// Log rotation policy variants.
#[derive(
    Clone,
    Copy,
    Debug,
    Deserialize,
    Serialize,
    Eq,
    PartialEq,
    Ord,
    PartialOrd,
    Hash,
)]
pub enum LogRotation {
    /// Size-based log rotation.
    Size(NonZeroU64),
    /// Time-based log rotation.
    Time(NonZeroU64),
    /// Date-based log rotation.
    Date,
    /// Count-based log rotation.
    Count(u32),
}

impl FromStr for LogRotation {
    type Err = ConfigError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let parts: Vec<&str> = s.trim().splitn(2, ':').collect();
        match parts[0].to_lowercase().as_str() {
            "size" => {
                let size_str = parts.get(1).ok_or_else(|| {
                    ConfigError::ValidationError(
                        "Missing size value for log rotation"
                            .to_string(),
                    )
                })?;
                let size = size_str.parse::<u64>().map_err(|_| ConfigError::ValidationError(format!("Invalid size value for log rotation: '{size_str}'")))?;
                Ok(Self::Size(NonZeroU64::new(size).ok_or_else(
                    || {
                        ConfigError::ValidationError(
                            "Log rotation size must be greater than 0"
                                .to_string(),
                        )
                    },
                )?))
            }
            "time" => {
                let time_str = parts.get(1).ok_or_else(|| {
                    ConfigError::ValidationError(
                        "Missing time value for log rotation"
                            .to_string(),
                    )
                })?;
                let time = time_str.parse::<u64>().map_err(|_| ConfigError::ValidationError(format!("Invalid time value for log rotation: '{time_str}'")))?;
                Ok(Self::Time(NonZeroU64::new(time).ok_or_else(
                    || {
                        ConfigError::ValidationError(
                            "Log rotation time must be greater than 0"
                                .to_string(),
                        )
                    },
                )?))
            }
            "date" => Ok(Self::Date),
            "count" => {
                let count = parts
                    .get(1)
                    .ok_or_else(|| ConfigError::ValidationError("Missing count value for log rotation".to_string()))?
                    .parse::<usize>()
                    .map_err(|_| ConfigError::ValidationError(format!("Invalid count value for log rotation: '{0}'", parts[1])))?;
                if count == 0 {
                    Err(ConfigError::ValidationError(
                        "Log rotation count must be greater than 0"
                            .to_string(),
                    ))
                } else {
                    Ok(Self::Count(
                        count.try_into().unwrap_or(u32::MAX),
                    ))
                }
            }
            _ => Err(ConfigError::ValidationError(format!(
                "Invalid log rotation option: '{s}'"
            ))),
        }
    }
}

/// Enum representing different logging destinations.
#[derive(Clone, Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
#[serde(tag = "type", content = "value")]
pub enum LoggingDestination {
    /// Log to a file.
    File(PathBuf),
    /// Log to standard output.
    Stdout,
    /// Log to a network destination.
    Network(String),
}

/// Configuration structure for the logging system.
#[derive(Debug, Clone, Serialize, Deserialize)]
// Allowed because Config contains no unsafe invariants that Deserialize could violate.
#[allow(clippy::unsafe_derive_deserialize)]
pub struct Config {
    /// Version of the configuration.
    #[serde(default = "default_version")]
    pub version: String,
    /// Profile name for the configuration.
    #[serde(default = "default_profile")]
    pub profile: String,
    /// Path to the log file.
    #[serde(default = "default_log_file_path")]
    pub log_file_path: PathBuf,
    /// Log level for the system.
    #[serde(default)]
    pub log_level: LogLevel,
    /// Log rotation settings.
    pub log_rotation: Option<LogRotation>,
    /// Log format string.
    #[serde(default = "default_log_format")]
    pub log_format: String,
    /// Logging destinations for the system.
    #[serde(default = "default_logging_destinations")]
    pub logging_destinations: Vec<LoggingDestination>,
    /// Environment variables for the system.
    #[serde(default)]
    pub env_vars: HashMap<String, String>,
}

fn default_version() -> String {
    CURRENT_CONFIG_VERSION.to_string()
}
fn default_profile() -> String {
    "default".to_string()
}
fn default_log_file_path() -> PathBuf {
    PathBuf::from("RLG.log")
}
fn default_log_format() -> String {
    "%level - %message".to_string()
}
fn default_logging_destinations() -> Vec<LoggingDestination> {
    vec![LoggingDestination::File(PathBuf::from("RLG.log"))]
}

impl Default for Config {
    fn default() -> Self {
        Self {
            version: default_version(),
            profile: default_profile(),
            log_file_path: default_log_file_path(),
            log_level: LogLevel::INFO,
            log_rotation: NonZeroU64::new(10 * 1024 * 1024)
                .map(LogRotation::Size),
            log_format: default_log_format(),
            logging_destinations: default_logging_destinations(),
            env_vars: HashMap::new(),
        }
    }
}

impl Config {
    /// Loads configuration from a file or falls back to defaults.
    ///
    /// This is the synchronous variant. See [`Config::load_async`] for the
    /// async equivalent (requires the `tokio` feature).
    ///
    /// # Errors
    ///
    /// Returns an error if the configuration file cannot be read,
    /// parsed, or if the version is unsupported.
    pub fn load<P: AsRef<Path>>(
        config_path: Option<P>,
    ) -> Result<Arc<RwLock<Self>>, ConfigError> {
        let config = if let Some(path) = config_path {
            let contents =
                fs::read_to_string(path.as_ref()).map_err(|e| {
                    ConfigError::FileReadError(e.to_string())
                })?;
            let config_source = ConfigSource::builder()
                .add_source(ConfigFile::from_str(
                    &contents,
                    config::FileFormat::Toml,
                ))
                .build()?;
            let version: String = config_source.get("version")?;
            if version != CURRENT_CONFIG_VERSION {
                return Err(ConfigError::VersionError(format!(
                    "Unsupported configuration version: {version}"
                )));
            }
            config_source.try_deserialize()?
        } else {
            Self::default()
        };
        config.validate()?;
        config.ensure_paths()?;
        Ok(Arc::new(RwLock::new(config)))
    }

    /// Loads configuration from a file or environment variables (async).
    ///
    /// Requires the `tokio` feature.
    ///
    /// # Errors
    ///
    /// This function returns an error if the configuration file cannot be read,
    /// parsed, or if the version is unsupported.
    #[cfg(feature = "tokio")]
    pub async fn load_async<P: AsRef<Path>>(
        config_path: Option<P>,
    ) -> Result<Arc<RwLock<Self>>, ConfigError> {
        let path_buf = config_path.map(|p| p.as_ref().to_path_buf());
        let config = if let Some(path) = path_buf {
            let mut file = File::open(&path).await.map_err(|e| {
                ConfigError::FileReadError(e.to_string())
            })?;
            let mut contents = String::new();
            file.read_to_string(&mut contents).await.map_err(|e| {
                ConfigError::FileReadError(e.to_string())
            })?;
            let config_source = ConfigSource::builder()
                .add_source(ConfigFile::from_str(
                    &contents,
                    config::FileFormat::Toml,
                ))
                .build()?;
            let version: String = config_source.get("version")?;
            if version != CURRENT_CONFIG_VERSION {
                return Err(ConfigError::VersionError(format!(
                    "Unsupported configuration version: {version}"
                )));
            }
            config_source.try_deserialize()?
        } else {
            Self::default()
        };
        config.validate()?;
        config.ensure_paths()?;
        Ok(Arc::new(RwLock::new(config)))
    }

    /// Saves the current configuration to a file in TOML format.
    ///
    /// This matches the TOML format expected by [`Config::load`].
    ///
    /// # Errors
    ///
    /// This function returns an error if the file cannot be written or
    /// if serialization fails.
    pub fn save_to_file<P: AsRef<Path>>(
        &self,
        path: P,
    ) -> Result<(), ConfigError> {
        let config_string =
            toml::to_string_pretty(self).map_err(|e| {
                ConfigError::FileWriteError(format!(
                    "Failed to serialize config to TOML: {e}"
                ))
            })?;
        fs::write(path, config_string).map_err(|e| {
            ConfigError::FileWriteError(format!(
                "Failed to write config file: {e}"
            ))
        })?;
        Ok(())
    }

    /// Sets a value in the configuration based on the specified key.
    ///
    /// # Errors
    ///
    /// This function returns an error if the value cannot be serialized or if the key is unknown.
    pub fn set<T: Serialize>(
        &mut self,
        key: &str,
        value: T,
    ) -> Result<(), ConfigError> {
        let val = serde_json::to_value(value)
            .map_err(|e| ConfigError::ValidationError(e.to_string()))?;

        match key {
            "version" => {
                if let Some(s) = val.as_str() {
                    self.version = s.to_string();
                } else {
                    return Err(ConfigError::ValidationError(
                        "Invalid version format".to_string(),
                    ));
                }
            }
            "profile" => {
                if let Some(s) = val.as_str() {
                    self.profile = s.to_string();
                } else {
                    return Err(ConfigError::ValidationError(
                        "Invalid profile format".to_string(),
                    ));
                }
            }
            "log_file_path" => {
                self.log_file_path = serde_json::from_value(val)
                    .map_err(|e| {
                        ConfigError::ConfigParseError(
                            SourceConfigError::Message(e.to_string()),
                        )
                    })?;
            }
            "log_level" => {
                self.log_level =
                    serde_json::from_value(val).map_err(|e| {
                        ConfigError::ConfigParseError(
                            SourceConfigError::Message(e.to_string()),
                        )
                    })?;
            }
            "log_rotation" => {
                self.log_rotation = serde_json::from_value(val)
                    .map_err(|e| {
                        ConfigError::ConfigParseError(
                            SourceConfigError::Message(e.to_string()),
                        )
                    })?;
            }
            "log_format" => {
                if let Some(s) = val.as_str() {
                    self.log_format = s.to_string();
                } else {
                    return Err(ConfigError::ValidationError(
                        "Invalid log format".to_string(),
                    ));
                }
            }
            "logging_destinations" => {
                self.logging_destinations = serde_json::from_value(val)
                    .map_err(|e| {
                        ConfigError::ConfigParseError(
                            SourceConfigError::Message(e.to_string()),
                        )
                    })?;
            }
            "env_vars" => {
                self.env_vars =
                    serde_json::from_value(val).map_err(|e| {
                        ConfigError::ConfigParseError(
                            SourceConfigError::Message(e.to_string()),
                        )
                    })?;
            }
            _ => {
                return Err(ConfigError::ValidationError(format!(
                    "Unknown configuration key: {key}"
                )));
            }
        }
        Ok(())
    }

    /// Validates the configuration settings.
    ///
    /// # Errors
    ///
    /// This function returns an error if any configuration setting is invalid.
    pub fn validate(&self) -> Result<(), ConfigError> {
        use crate::commons::validation::{
            Validator, validate_not_empty,
        };

        let mut v = Validator::new();
        v.check("version", || {
            validate_not_empty(self.version.trim()).map(|_| ())
        })
        .check("profile", || {
            validate_not_empty(self.profile.trim()).map(|_| ())
        })
        .check("log_format", || {
            validate_not_empty(self.log_format.trim()).map(|_| ())
        });

        // Path and destination checks remain manual (not string validations)
        if self.log_file_path.as_os_str().is_empty() {
            return Err(ConfigError::ValidationError(
                "Log file path cannot be empty".into(),
            ));
        }
        if self.logging_destinations.is_empty() {
            return Err(ConfigError::ValidationError(
                "At least one logging destination must be specified"
                    .into(),
            ));
        }
        for (key, value) in &self.env_vars {
            v.check(&format!("env_var_key_{key}"), || {
                validate_not_empty(key.trim()).map(|_| ())
            });
            v.check(&format!("env_var_val_{key}"), || {
                validate_not_empty(value.trim()).map(|_| ())
            });
        }

        v.finish().map_err(|errors| {
            let msgs: Vec<String> = errors
                .iter()
                .map(|(f, e)| format!("{f}: {e}"))
                .collect();
            ConfigError::ValidationError(msgs.join("; "))
        })
    }

    /// Creates directories and log files required by the configuration.
    ///
    /// # Errors
    ///
    /// This function returns an error if the directories or files cannot be created.
    pub fn ensure_paths(&self) -> Result<(), ConfigError> {
        if let Some(LoggingDestination::File(path)) =
            self.logging_destinations.first()
        {
            if let Some(parent_dir) = path.parent() {
                fs::create_dir_all(parent_dir).map_err(|e| {
                    ConfigError::ValidationError(format!(
                        "Failed to create directory for log file: {e}"
                    ))
                })?;
            }
            OpenOptions::new()
                .create(true)
                .append(true)
                .open(path)
                .map_err(|e| {
                    ConfigError::ValidationError(format!(
                        "Log file is not writable: {e}"
                    ))
                })?;
        }
        Ok(())
    }

    /// Expands environment variables in the configuration values.
    #[must_use]
    pub fn expand_env_vars(&self) -> Self {
        let mut new_config = self.clone();
        for (key, value) in &mut new_config.env_vars {
            if let Ok(env_value) = env::var(key) {
                *value = env_value;
            }
        }
        new_config
    }

    /// Hot-reloads configuration on file change.
    ///
    /// Requires the `tokio` feature.
    ///
    /// # Errors
    ///
    /// This function returns an error if the watcher cannot be initialized.
    #[cfg(feature = "tokio")]
    #[allow(clippy::incompatible_msrv)]
    pub fn hot_reload_async(
        config_path: &str,
        config: &Arc<RwLock<Self>>,
    ) -> Result<mpsc::Sender<()>, ConfigError> {
        let (stop_tx, mut stop_rx) = mpsc::channel::<()>(1);
        let (tx, mut rx) = mpsc::channel::<notify::Result<Event>>(100);

        let mut watcher = notify::recommended_watcher(move |res| {
            let _ = tx.blocking_send(res);
        })?;
        watcher.watch(
            Path::new(config_path),
            RecursiveMode::NonRecursive,
        )?;

        let config_clone = config.clone();
        let path_owned = config_path.to_string();
        tokio::spawn(async move {
            let _watcher = watcher; // Keep watcher alive for the lifetime of the task
            loop {
                tokio::select! {
                    Some(res) = rx.recv() => {
                        if let Ok(Event { kind: EventKind::Modify(_), .. }) = res
                            && let Ok(new_config) = Self::load_async(Some(&path_owned)).await {
                                let mut config_write = config_clone.write();
                                *config_write = new_config.read().clone();
                        }
                    }
                    _ = stop_rx.recv() => break,
                }
            }
        });
        Ok(stop_tx)
    }

    /// Compares two configurations and returns the differences.
    #[must_use]
    pub fn diff(
        config1: &Self,
        config2: &Self,
    ) -> HashMap<String, String> {
        let mut diffs = HashMap::new();
        macro_rules! config_diff_fields {
            ($c1:expr, $c2:expr, $diffs:expr;
             $( display $field:ident; )*
             $( debug $dfield:ident; )*
             $( path $pfield:ident; )*
            ) => {
                $(
                    if $c1.$field != $c2.$field {
                        $diffs.insert(
                            stringify!($field).to_string(),
                            format!("{} -> {}", $c1.$field, $c2.$field),
                        );
                    }
                )*
                $(
                    if $c1.$dfield != $c2.$dfield {
                        $diffs.insert(
                            stringify!($dfield).to_string(),
                            format!("{:?} -> {:?}", $c1.$dfield, $c2.$dfield),
                        );
                    }
                )*
                $(
                    if $c1.$pfield != $c2.$pfield {
                        $diffs.insert(
                            stringify!($pfield).to_string(),
                            format!("{} -> {}", $c1.$pfield.display(), $c2.$pfield.display()),
                        );
                    }
                )*
            };
        }
        config_diff_fields!(config1, config2, diffs;
            display version;
            display profile;
            display log_format;
            debug log_level;
            debug log_rotation;
            debug logging_destinations;
            debug env_vars;
            path log_file_path;
        );
        diffs
    }

    /// Overrides the current configuration with values from another configuration.
    #[must_use]
    pub fn override_with(&self, other: &Self) -> Self {
        let mut env_vars = self.env_vars.clone();
        env_vars.extend(other.env_vars.clone());
        Self {
            version: other.version.clone(),
            profile: other.profile.clone(),
            log_file_path: other.log_file_path.clone(),
            log_level: other.log_level,
            log_rotation: other.log_rotation,
            log_format: other.log_format.clone(),
            logging_destinations: other.logging_destinations.clone(),
            env_vars,
        }
    }
}

impl TryFrom<env::Vars> for Config {
    type Error = ConfigError;
    fn try_from(vars: env::Vars) -> Result<Self, Self::Error> {
        envy::from_iter(vars).map_err(ConfigError::EnvVarParseError)
    }
}

impl fmt::Display for LogRotation {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Size(size) => write!(f, "Size: {size} bytes"),
            Self::Time(seconds) => write!(f, "Time: {seconds} seconds"),
            Self::Date => write!(f, "Date-based rotation"),
            Self::Count(count) => write!(f, "Count: {count} logs"),
        }
    }
}

#[cfg(all(test, not(miri)))]
mod tests {
    use super::*;

    #[cfg(feature = "tokio")]
    #[tokio::test]
    #[cfg_attr(miri, ignore)]
    async fn test_config_hot_reload_async_full() {
        use parking_lot::RwLock;
        use std::sync::Arc;
        use tokio::time::{Duration, sleep};

        let temp_dir = tempfile::tempdir().unwrap();
        let config_path = temp_dir.path().join("config.toml");
        let config = Config::default();
        config.save_to_file(&config_path).unwrap();

        let shared_config = Arc::new(RwLock::new(Config::default()));
        let stop_tx = Config::hot_reload_async(
            config_path.to_str().unwrap(),
            &shared_config,
        )
        .unwrap();

        // Trigger Modify
        let new_config = Config {
            profile: "modified".to_string(),
            ..Config::default()
        };
        new_config.save_to_file(&config_path).unwrap();

        sleep(Duration::from_millis(200)).await;

        let _ = stop_tx.send(()).await;
    }

    #[test]
    fn test_config_set_exhaustive() {
        let mut config = Config::default();
        assert!(config.set("version", 123).is_err());
        assert!(config.set("profile", 123).is_err());
        assert!(config.set("log_file_path", 123).is_err());
        assert!(config.set("log_level", 123).is_err());
        assert!(config.set("log_rotation", 123).is_err());
        assert!(config.set("log_format", 123).is_err());
        assert!(config.set("logging_destinations", 123).is_err());
        assert!(config.set("env_vars", 123).is_err());
        assert!(config.set("unknown_key", "value").is_err());
    }

    #[test]
    fn test_config_set_unknown_key() {
        let mut config = Config::default();
        let res = config.set("absolutely_unknown_key_123", "value");
        assert!(res.is_err());
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_config_save_to_file_fail_unit() {
        let config = Config::default();
        let dir_path = env::temp_dir();
        let res = config.save_to_file(&dir_path);
        assert!(res.is_err());
    }

    #[test]
    fn test_commons_config_error_conversion() {
        let commons_err =
            crate::commons::config::ConfigError::MissingKey(
                "test_key".to_string(),
            );
        let config_err: ConfigError = commons_err.into();
        assert!(matches!(config_err, ConfigError::ValidationError(_)));
        assert!(config_err.to_string().contains("test_key"));
    }

    #[test]
    fn test_log_rotation_exhaustive() {
        assert!(LogRotation::from_str("count:0").is_err());
        assert!(LogRotation::from_str("size:0").is_err());
        assert!(LogRotation::from_str("time:0").is_err());
        assert!(LogRotation::from_str("invalid:xxx").is_err());
    }

    #[test]
    fn test_log_rotation_valid() {
        let size = LogRotation::from_str("size:1024").unwrap();
        assert!(matches!(size, LogRotation::Size(_)));

        let time = LogRotation::from_str("time:3600").unwrap();
        assert!(matches!(time, LogRotation::Time(_)));

        let date = LogRotation::from_str("date").unwrap();
        assert!(matches!(date, LogRotation::Date));

        let count = LogRotation::from_str("count:10").unwrap();
        assert!(matches!(count, LogRotation::Count(10)));
    }

    #[test]
    fn test_log_rotation_missing_values() {
        assert!(LogRotation::from_str("size").is_err());
        assert!(LogRotation::from_str("time").is_err());
        assert!(LogRotation::from_str("count").is_err());
    }

    #[test]
    fn test_log_rotation_invalid_numbers() {
        assert!(LogRotation::from_str("size:abc").is_err());
        assert!(LogRotation::from_str("time:xyz").is_err());
        assert!(LogRotation::from_str("count:abc").is_err());
    }

    #[test]
    fn test_log_rotation_display() {
        let size = LogRotation::Size(NonZeroU64::new(1024).unwrap());
        assert_eq!(size.to_string(), "Size: 1024 bytes");

        let time = LogRotation::Time(NonZeroU64::new(3600).unwrap());
        assert_eq!(time.to_string(), "Time: 3600 seconds");

        assert_eq!(
            LogRotation::Date.to_string(),
            "Date-based rotation"
        );

        assert_eq!(LogRotation::Count(5).to_string(), "Count: 5 logs");
    }

    #[test]
    fn test_config_default_values() {
        let config = Config::default();
        assert_eq!(config.version, "1.0");
        assert_eq!(config.profile, "default");
        assert_eq!(config.log_file_path, PathBuf::from("RLG.log"));
        assert_eq!(config.log_level, LogLevel::INFO);
        assert!(config.log_rotation.is_some());
        assert_eq!(config.log_format, "%level - %message");
        assert!(!config.logging_destinations.is_empty());
        assert!(config.env_vars.is_empty());
    }

    #[test]
    fn test_config_set_valid_values() {
        let mut config = Config::default();
        assert!(config.set("version", "2.0").is_ok());
        assert_eq!(config.version, "2.0");

        assert!(config.set("profile", "production").is_ok());
        assert_eq!(config.profile, "production");

        assert!(config.set("log_format", "%time %level %msg").is_ok());
        assert_eq!(config.log_format, "%time %level %msg");

        assert!(config.set("log_file_path", "/tmp/test.log").is_ok());
        assert_eq!(
            config.log_file_path,
            PathBuf::from("/tmp/test.log")
        );
    }

    #[test]
    fn test_config_set_log_level() {
        let mut config = Config::default();
        assert!(config.set("log_level", "DEBUG").is_ok());
        assert_eq!(config.log_level, LogLevel::DEBUG);
    }

    #[test]
    fn test_config_set_log_rotation() {
        let mut config = Config::default();
        assert!(config.set("log_rotation", Option::<()>::None).is_ok());
        assert!(config.log_rotation.is_none());
    }

    #[test]
    fn test_config_set_logging_destinations() {
        let mut config = Config::default();
        let dests = vec![LoggingDestination::Stdout];
        assert!(config.set("logging_destinations", &dests).is_ok());
        assert_eq!(config.logging_destinations.len(), 1);
    }

    #[test]
    fn test_config_set_env_vars() {
        let mut config = Config::default();
        let mut vars = HashMap::new();
        vars.insert("KEY".to_string(), "VALUE".to_string());
        assert!(config.set("env_vars", &vars).is_ok());
        assert_eq!(config.env_vars.get("KEY").unwrap(), "VALUE");
    }

    #[test]
    fn test_config_validate_empty_path() {
        let config = Config {
            log_file_path: PathBuf::from(""),
            ..Config::default()
        };
        assert!(config.validate().is_err());
    }

    #[test]
    fn test_config_validate_empty_destinations() {
        let mut config = Config::default();
        config.logging_destinations.clear();
        assert!(config.validate().is_err());
    }

    #[test]
    fn test_config_validate_empty_version() {
        let config = Config {
            version: "  ".to_string(),
            ..Config::default()
        };
        assert!(config.validate().is_err());
    }

    #[test]
    fn test_config_validate_empty_profile() {
        let config = Config {
            profile: "  ".to_string(),
            ..Config::default()
        };
        assert!(config.validate().is_err());
    }

    #[test]
    fn test_config_validate_empty_log_format() {
        let config = Config {
            log_format: "  ".to_string(),
            ..Config::default()
        };
        assert!(config.validate().is_err());
    }

    #[test]
    fn test_config_validate_empty_env_var() {
        let mut config = Config::default();
        config.env_vars.insert(String::new(), "val".to_string());
        assert!(config.validate().is_err());
    }

    #[test]
    #[allow(unsafe_code)]
    #[cfg_attr(miri, ignore)]
    fn test_config_expand_env_vars() {
        // SAFETY: this test owns the value for the duration of the
        // expand_env_vars call; no other thread reads it.
        unsafe { env::set_var("RLG_TEST_EXPAND_KEY", "expected") };
        let mut config = Config::default();
        config.env_vars.insert(
            "RLG_TEST_EXPAND_KEY".to_string(),
            "placeholder".to_string(),
        );
        let expanded = config.expand_env_vars();
        assert_eq!(
            expanded.env_vars["RLG_TEST_EXPAND_KEY"],
            "expected"
        );
        // SAFETY: cleanup.
        unsafe { env::remove_var("RLG_TEST_EXPAND_KEY") };
    }

    #[test]
    fn test_config_expand_env_vars_missing() {
        let mut config = Config::default();
        config.env_vars.insert(
            "DEFINITELY_NOT_SET_VAR_XYZ_123".to_string(),
            "original".to_string(),
        );
        let expanded = config.expand_env_vars();
        assert_eq!(
            expanded.env_vars["DEFINITELY_NOT_SET_VAR_XYZ_123"],
            "original"
        );
    }

    #[test]
    fn test_config_diff_no_changes() {
        let c1 = Config::default();
        let c2 = Config::default();
        let diffs = Config::diff(&c1, &c2);
        assert!(diffs.is_empty());
    }

    #[test]
    fn test_config_diff_with_changes() {
        let c1 = Config::default();
        let c2 = Config {
            version: "2.0".to_string(),
            profile: "prod".to_string(),
            log_format: "%msg".to_string(),
            log_level: LogLevel::DEBUG,
            log_file_path: PathBuf::from("/var/log/app.log"),
            ..Config::default()
        };
        let diffs = Config::diff(&c1, &c2);
        assert!(diffs.contains_key("version"));
        assert!(diffs.contains_key("profile"));
        assert!(diffs.contains_key("log_format"));
        assert!(diffs.contains_key("log_level"));
        assert!(diffs.contains_key("log_file_path"));
    }

    #[test]
    fn test_config_override_with() {
        let c1 = Config::default();
        let mut c2 = Config {
            version: "2.0".to_string(),
            profile: "prod".to_string(),
            ..Config::default()
        };
        c2.env_vars
            .insert("NEW_KEY".to_string(), "new_val".to_string());
        let merged = c1.override_with(&c2);
        assert_eq!(merged.version, "2.0");
        assert_eq!(merged.profile, "prod");
        assert!(merged.env_vars.contains_key("NEW_KEY"));
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_config_ensure_paths() {
        let config = Config::default();
        // Default config points to RLG.log in current dir — should succeed
        assert!(config.ensure_paths().is_ok());
    }

    #[test]
    fn test_config_ensure_paths_stdout_dest() {
        let config = Config {
            logging_destinations: vec![LoggingDestination::Stdout],
            ..Config::default()
        };
        // Stdout destination doesn't match File pattern — should succeed
        assert!(config.ensure_paths().is_ok());
    }

    #[test]
    fn test_config_envy_from_iter_succeeds_with_defaults() {
        // All `Config` fields have serde defaults; `envy::from_iter`
        // should succeed even with an empty iterator.
        let empty: Vec<(String, String)> = Vec::new();
        let cfg: Config = envy::from_iter(empty).unwrap();
        assert!(!cfg.version.is_empty());
    }

    #[test]
    fn test_config_envy_from_iter_rejects_bad_type() {
        // Force an `envy::Error` by supplying a typed field with
        // unparseable contents. `log_level` deserializes from a string,
        // and `LogLevel::from_str` rejects unknown labels.
        let bad = vec![(
            "log_level".to_string(),
            "NOT_A_REAL_LEVEL".to_string(),
        )];
        let result: Result<Config, _> = envy::from_iter(bad);
        let err = result.unwrap_err();
        // Whatever the wording, the key error must surface somehow.
        let msg = err.to_string().to_lowercase();
        assert!(!msg.is_empty(), "got: {err}");
    }

    #[test]
    fn test_config_try_from_real_env_vars() {
        // Exercises the `TryFrom<env::Vars>` impl with the process's
        // actual env (which always has serde defaults available).
        let result = Config::try_from(env::vars());
        assert!(result.is_ok() || result.is_err());
    }

    #[test]
    fn test_logging_destination_debug() {
        let file_dest =
            LoggingDestination::File(PathBuf::from("/tmp/test.log"));
        let stdout_dest = LoggingDestination::Stdout;
        let network_dest =
            LoggingDestination::Network("localhost:9200".into());
        assert!(format!("{file_dest:?}").contains("File"));
        assert!(format!("{stdout_dest:?}").contains("Stdout"));
        assert!(format!("{network_dest:?}").contains("Network"));
    }

    #[test]
    fn test_config_error_display_all_variants() {
        let err = ConfigError::InvalidFilePath("bad".into());
        assert!(err.to_string().contains("Invalid file path"));

        let err = ConfigError::FileReadError("read fail".into());
        assert!(err.to_string().contains("File read error"));

        let err = ConfigError::FileWriteError("write fail".into());
        assert!(err.to_string().contains("File write error"));

        let err = ConfigError::ValidationError("invalid".into());
        assert!(err.to_string().contains("validation error"));

        let err = ConfigError::VersionError("bad version".into());
        assert!(err.to_string().contains("version error"));

        let err = ConfigError::MissingFieldError("field_x".into());
        assert!(err.to_string().contains("Missing required field"));
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_config_save_and_load() {
        let temp_dir = tempfile::tempdir().unwrap();
        let path = temp_dir.path().join("test_config.toml");
        let config = Config::default();
        config.save_to_file(&path).unwrap();
        assert!(path.exists());
    }

    #[cfg(feature = "tokio")]
    #[tokio::test]
    #[cfg_attr(miri, ignore)]
    async fn test_load_async_with_valid_toml() {
        let temp_dir = tempfile::tempdir().unwrap();
        let config_path = temp_dir.path().join("config.toml");
        let toml_content = r#"
version = "1.0"
profile = "test"
log_file_path = "test.log"
log_format = "%level - %message"

[[logging_destinations]]
type = "File"
value = "test.log"
"#;
        fs::write(&config_path, toml_content).unwrap();
        let result = Config::load_async(Some(&config_path)).await;
        assert!(result.is_ok());
        let config = result.unwrap();
        let c = config.read();
        assert_eq!(c.version, "1.0");
        assert_eq!(c.profile, "test");
        drop(c);
    }

    #[cfg(feature = "tokio")]
    #[tokio::test]
    #[cfg_attr(miri, ignore)]
    async fn test_load_async_with_bad_version() {
        let temp_dir = tempfile::tempdir().unwrap();
        let config_path = temp_dir.path().join("bad_version.toml");
        let toml_content = r#"
version = "99.0"
profile = "test"
log_file_path = "test.log"
log_format = "%level - %message"

[[logging_destinations]]
type = "File"
value = "test.log"
"#;
        fs::write(&config_path, toml_content).unwrap();
        let result = Config::load_async(Some(&config_path)).await;
        assert!(result.is_err());
    }

    #[cfg(feature = "tokio")]
    #[tokio::test]
    #[cfg_attr(miri, ignore)]
    async fn test_load_async_no_path() {
        let result = Config::load_async(None::<&str>).await;
        assert!(result.is_ok());
    }

    #[cfg(feature = "tokio")]
    #[tokio::test]
    #[cfg_attr(miri, ignore)]
    async fn test_load_async_nonexistent_file() {
        let result = Config::load_async(Some(
            "/tmp/definitely_not_exists_rlg_test.toml",
        ))
        .await;
        assert!(result.is_err());
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_load_sync_with_valid_toml() {
        let temp_dir = tempfile::tempdir().unwrap();
        let config_path = temp_dir.path().join("config.toml");
        let toml_content = r#"
version = "1.0"
profile = "test"
log_file_path = "test.log"
log_format = "%level - %message"

[[logging_destinations]]
type = "File"
value = "test.log"
"#;
        fs::write(&config_path, toml_content).unwrap();
        let result = Config::load(Some(&config_path));
        assert!(result.is_ok());
        let config = result.unwrap();
        let c = config.read();
        assert_eq!(c.version, "1.0");
        assert_eq!(c.profile, "test");
        drop(c);
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_load_sync_no_path() {
        let result = Config::load(None::<&str>);
        assert!(result.is_ok());
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_load_sync_nonexistent_file() {
        let result = Config::load(Some(
            "/tmp/definitely_not_exists_rlg_test.toml",
        ));
        assert!(result.is_err());
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_load_sync_bad_version() {
        let temp_dir = tempfile::tempdir().unwrap();
        let config_path = temp_dir.path().join("bad_version.toml");
        let toml_content = r#"
version = "99.0"
profile = "test"
log_file_path = "test.log"
log_format = "%level - %message"

[[logging_destinations]]
type = "File"
value = "test.log"
"#;
        fs::write(&config_path, toml_content).unwrap();
        let result = Config::load(Some(&config_path));
        assert!(result.is_err());
    }

    #[test]
    fn test_config_save_to_file_success() {
        let temp_dir = tempfile::tempdir().unwrap();
        let path = temp_dir.path().join("save_test_config.toml");
        let config = Config::default();
        assert!(config.save_to_file(&path).is_ok());
        let contents = fs::read_to_string(&path).unwrap();
        assert!(contents.contains("version"));
    }

    #[test]
    #[cfg_attr(miri, ignore)]
    fn test_config_save_and_load_roundtrip() {
        let temp_dir = tempfile::tempdir().unwrap();
        let path = temp_dir.path().join("roundtrip.toml");
        let config = Config::default();
        config.save_to_file(&path).unwrap();
        let loaded = Config::load(Some(&path)).unwrap();
        let guard = loaded.read();
        let version = guard.version.clone();
        let profile = guard.profile.clone();
        let log_level = guard.log_level;
        drop(guard);
        assert_eq!(version, config.version);
        assert_eq!(profile, config.profile);
        assert_eq!(log_level, config.log_level);
    }
}