// SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
// SPDX-License-Identifier: Apache-2.0

use anyhow::Result;
use derive_builder::Builder;
use figment::{
    Figment,
    providers::{Env, Format, Serialized, Toml},
};
use serde::{Deserialize, Serialize};
use std::fmt;
use std::sync::OnceLock;
use validator::Validate;

pub mod environment_names;

/// Default system host for health and metrics endpoints
const DEFAULT_SYSTEM_HOST: &str = "0.0.0.0";

/// Default system port for health and metrics endpoints (-1 = disabled)
const DEFAULT_SYSTEM_PORT: i16 = -1;

/// Default health endpoint paths
const DEFAULT_SYSTEM_HEALTH_PATH: &str = "/health";
const DEFAULT_SYSTEM_LIVE_PATH: &str = "/live";

/// Default health check configuration
/// This is the wait time before sending canary health checks when no activity is detected
pub const DEFAULT_CANARY_WAIT_TIME_SECS: u64 = 10;
/// Default timeout for individual health check requests
pub const DEFAULT_HEALTH_CHECK_REQUEST_TIMEOUT_SECS: u64 = 3;

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct WorkerConfig {
    /// Grace shutdown period for the system server.
    pub graceful_shutdown_timeout: u64,
}

impl WorkerConfig {
    /// Instantiates and reads server configurations from appropriate sources.
    /// Panics on invalid configuration.
    pub fn from_settings() -> Self {
        // All calls should be global and thread safe.
        Figment::new()
            .merge(Serialized::defaults(Self::default()))
            .merge(Env::prefixed("DYN_WORKER_"))
            .extract()
            .unwrap() // safety: Called on startup, so panic is reasonable
    }
}

impl Default for WorkerConfig {
    fn default() -> Self {
        WorkerConfig {
            graceful_shutdown_timeout: if cfg!(debug_assertions) {
                1 // Debug build: 1 second
            } else {
                30 // Release build: 30 seconds
            },
        }
    }
}

#[derive(Debug, Deserialize, Serialize, PartialEq, Clone)]
#[serde(rename_all = "lowercase")]
pub enum HealthStatus {
    Ready,
    NotReady,
}

/// Runtime configuration
/// Defines the configuration for Tokio runtimes
#[derive(Serialize, Deserialize, Validate, Debug, Builder, Clone)]
#[builder(build_fn(private, name = "build_internal"), derive(Debug, Serialize))]
pub struct RuntimeConfig {
    /// Number of async worker threads
    /// If set to 1, the runtime will run in single-threaded mode
    /// Set this at runtime with environment variable DYN_RUNTIME_NUM_WORKER_THREADS. Defaults to
    /// number of cores.
    #[validate(range(min = 1))]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub num_worker_threads: Option<usize>,

    /// Maximum number of blocking threads
    /// Blocking threads are used for blocking operations, this value must be greater than 0.
    /// Set this at runtime with environment variable DYN_RUNTIME_MAX_BLOCKING_THREADS. Defaults to
    /// 512.
    #[validate(range(min = 1))]
    #[builder(default = "512")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub max_blocking_threads: usize,

    /// System status server host for health and metrics endpoints
    /// Set this at runtime with environment variable DYN_SYSTEM_HOST
    #[builder(default = "DEFAULT_SYSTEM_HOST.to_string()")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub system_host: String,

    /// System status server port for health and metrics endpoints
    /// Set to -1 to disable the system status server (default)
    /// Set to 0 to bind to a random available port
    /// Set to a positive port number (e.g. 8081) to bind to a specific port
    /// Set this at runtime with environment variable DYN_SYSTEM_PORT
    #[builder(default = "DEFAULT_SYSTEM_PORT")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub system_port: i16,

    /// Health and metrics System status server enabled (DEPRECATED)
    /// This field is deprecated. Use system_port instead (set to positive value to enable)
    /// Environment variable DYN_SYSTEM_ENABLED is deprecated
    #[deprecated(
        note = "Use system_port instead. Set DYN_SYSTEM_PORT to enable the system metrics server."
    )]
    #[builder(default = "false")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub system_enabled: bool,

    /// Starting Health Status
    /// Set this at runtime with environment variable DYN_SYSTEM_STARTING_HEALTH_STATUS
    #[builder(default = "HealthStatus::NotReady")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub starting_health_status: HealthStatus,

    /// Use Endpoint Health Status
    /// When using endpoint health status, health status
    /// is the AND of individual endpoint health
    /// Set this at runtime with environment variable DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS
    /// with the list of endpoints to consider for system health
    #[builder(default = "vec![]")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub use_endpoint_health_status: Vec<String>,

    /// Health endpoint paths
    /// Set this at runtime with environment variable DYN_SYSTEM_HEALTH_PATH
    #[builder(default = "DEFAULT_SYSTEM_HEALTH_PATH.to_string()")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub system_health_path: String,
    /// Set this at runtime with environment variable DYN_SYSTEM_LIVE_PATH
    #[builder(default = "DEFAULT_SYSTEM_LIVE_PATH.to_string()")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub system_live_path: String,

    /// Number of threads for the Rayon compute pool
    /// If not set, defaults to num_cpus / 2
    /// Set this at runtime with environment variable DYN_COMPUTE_THREADS
    #[builder(default = "None")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub compute_threads: Option<usize>,

    /// Stack size for compute threads in bytes
    /// Defaults to 2MB (2097152 bytes)
    /// Set this at runtime with environment variable DYN_COMPUTE_STACK_SIZE
    #[builder(default = "Some(2 * 1024 * 1024)")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub compute_stack_size: Option<usize>,

    /// Thread name prefix for compute pool threads
    /// Set this at runtime with environment variable DYN_COMPUTE_THREAD_PREFIX
    #[builder(default = "\"compute\".to_string()")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub compute_thread_prefix: String,

    /// Enable active health checking with payloads
    /// Set this at runtime with environment variable DYN_HEALTH_CHECK_ENABLED
    #[builder(default = "false")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub health_check_enabled: bool,

    /// Canary wait time in seconds (time to wait before sending health check when no activity)
    /// Set this at runtime with environment variable DYN_CANARY_WAIT_TIME
    #[builder(default = "DEFAULT_CANARY_WAIT_TIME_SECS")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub canary_wait_time_secs: u64,

    /// Health check request timeout in seconds
    /// Set this at runtime with environment variable DYN_HEALTH_CHECK_REQUEST_TIMEOUT
    #[builder(default = "DEFAULT_HEALTH_CHECK_REQUEST_TIMEOUT_SECS")]
    #[builder_field_attr(serde(skip_serializing_if = "Option::is_none"))]
    pub health_check_request_timeout_secs: u64,
}

impl fmt::Display for RuntimeConfig {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // If None, it defaults to "number of cores", so we indicate that.
        match self.num_worker_threads {
            Some(val) => write!(f, "num_worker_threads={val}, ")?,
            None => write!(f, "num_worker_threads=default (num_cores), ")?,
        }

        write!(f, "max_blocking_threads={}, ", self.max_blocking_threads)?;
        write!(f, "system_host={}, ", self.system_host)?;
        write!(f, "system_port={}, ", self.system_port)?;
        write!(
            f,
            "use_endpoint_health_status={:?}",
            self.use_endpoint_health_status
        )?;
        write!(
            f,
            "starting_health_status={:?}",
            self.starting_health_status
        )?;
        write!(f, ", system_health_path={}", self.system_health_path)?;
        write!(f, ", system_live_path={}", self.system_live_path)?;
        write!(f, ", health_check_enabled={}", self.health_check_enabled)?;
        write!(f, ", canary_wait_time_secs={}", self.canary_wait_time_secs)?;
        write!(
            f,
            ", health_check_request_timeout_secs={}",
            self.health_check_request_timeout_secs
        )?;

        Ok(())
    }
}

impl RuntimeConfig {
    pub fn builder() -> RuntimeConfigBuilder {
        RuntimeConfigBuilder::default()
    }

    pub(crate) fn figment() -> Figment {
        Figment::new()
            .merge(Serialized::defaults(RuntimeConfig::default()))
            .merge(Toml::file("/opt/dynamo/defaults/runtime.toml"))
            .merge(Toml::file("/opt/dynamo/etc/runtime.toml"))
            .merge(Env::prefixed("DYN_RUNTIME_").filter_map(|k| {
                let full_key = format!("DYN_RUNTIME_{}", k.as_str());
                // filters out empty environment variables
                match std::env::var(&full_key) {
                    Ok(v) if !v.is_empty() => Some(k.into()),
                    _ => None,
                }
            }))
            .merge(Env::prefixed("DYN_SYSTEM_").filter_map(|k| {
                let full_key = format!("DYN_SYSTEM_{}", k.as_str());
                // filters out empty environment variables
                match std::env::var(&full_key) {
                    Ok(v) if !v.is_empty() => {
                        // Map DYN_SYSTEM_* to the correct field names
                        let mapped_key = match k.as_str() {
                            "HOST" => "system_host",
                            "PORT" => "system_port",
                            "ENABLED" => "system_enabled",
                            "USE_ENDPOINT_HEALTH_STATUS" => "use_endpoint_health_status",
                            "STARTING_HEALTH_STATUS" => "starting_health_status",
                            "HEALTH_PATH" => "system_health_path",
                            "LIVE_PATH" => "system_live_path",
                            _ => k.as_str(),
                        };
                        Some(mapped_key.into())
                    }
                    _ => None,
                }
            }))
            .merge(Env::prefixed("DYN_COMPUTE_").filter_map(|k| {
                let full_key = format!("DYN_COMPUTE_{}", k.as_str());
                // filters out empty environment variables
                match std::env::var(&full_key) {
                    Ok(v) if !v.is_empty() => {
                        // Map DYN_COMPUTE_* to the correct field names
                        let mapped_key = match k.as_str() {
                            "THREADS" => "compute_threads",
                            "STACK_SIZE" => "compute_stack_size",
                            "THREAD_PREFIX" => "compute_thread_prefix",
                            _ => k.as_str(),
                        };
                        Some(mapped_key.into())
                    }
                    _ => None,
                }
            }))
            .merge(Env::prefixed("DYN_HEALTH_CHECK_").filter_map(|k| {
                let full_key = format!("DYN_HEALTH_CHECK_{}", k.as_str());
                // filters out empty environment variables
                match std::env::var(&full_key) {
                    Ok(v) if !v.is_empty() => {
                        // Map DYN_HEALTH_CHECK_* to the correct field names
                        let mapped_key = match k.as_str() {
                            "ENABLED" => "health_check_enabled",
                            "REQUEST_TIMEOUT" => "health_check_request_timeout_secs",
                            _ => k.as_str(),
                        };
                        Some(mapped_key.into())
                    }
                    _ => None,
                }
            }))
            .merge(Env::prefixed("DYN_CANARY_").filter_map(|k| {
                let full_key = format!("DYN_CANARY_{}", k.as_str());
                // filters out empty environment variables
                match std::env::var(&full_key) {
                    Ok(v) if !v.is_empty() => {
                        // Map DYN_CANARY_* to the correct field names
                        let mapped_key = match k.as_str() {
                            "WAIT_TIME" => "canary_wait_time_secs",
                            _ => k.as_str(),
                        };
                        Some(mapped_key.into())
                    }
                    _ => None,
                }
            }))
    }

    /// Load the runtime configuration from the environment and configuration files
    /// Configuration is priorities in the following order, where the last has the lowest priority:
    /// 1. Environment variables (top priority)
    ///    TO DO: Add documentation for configuration files. Paths should be configurable.
    /// 2. /opt/dynamo/etc/runtime.toml
    /// 3. /opt/dynamo/defaults/runtime.toml (lowest priority)
    ///
    /// Environment variables are prefixed with `DYN_RUNTIME_` and `DYN_SYSTEM`
    pub fn from_settings() -> Result<RuntimeConfig> {
        use environment_names::runtime::system as env_system;
        // Check for deprecated environment variables
        if std::env::var(env_system::DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS).is_ok() {
            tracing::warn!(
                "DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS is deprecated and no longer used. \
                System health is now determined by endpoints that register with health check payloads. \
                Please update your configuration to register health check payloads directly on endpoints."
            );
        }

        if std::env::var(env_system::DYN_SYSTEM_ENABLED).is_ok() {
            tracing::warn!(
                "DYN_SYSTEM_ENABLED is deprecated. \
                System metrics server is now controlled solely by DYN_SYSTEM_PORT. \
                Set DYN_SYSTEM_PORT to a positive value to enable the server, or set to -1 to disable (default)."
            );
        }

        let config: RuntimeConfig = Self::figment().extract()?;
        config.validate()?;
        Ok(config)
    }

    /// Check if System server should be enabled
    /// System server is enabled when DYN_SYSTEM_PORT is set to 0 or a positive value
    /// Port 0 binds to a random available port
    /// Negative values disable the server
    pub fn system_server_enabled(&self) -> bool {
        self.system_port >= 0
    }

    pub fn single_threaded() -> Self {
        RuntimeConfig {
            num_worker_threads: Some(1),
            max_blocking_threads: 1,
            system_host: DEFAULT_SYSTEM_HOST.to_string(),
            system_port: DEFAULT_SYSTEM_PORT,
            #[allow(deprecated)]
            system_enabled: false,
            starting_health_status: HealthStatus::NotReady,
            use_endpoint_health_status: vec![],
            system_health_path: DEFAULT_SYSTEM_HEALTH_PATH.to_string(),
            system_live_path: DEFAULT_SYSTEM_LIVE_PATH.to_string(),
            compute_threads: Some(1),
            compute_stack_size: Some(2 * 1024 * 1024),
            compute_thread_prefix: "compute".to_string(),
            health_check_enabled: false,
            canary_wait_time_secs: DEFAULT_CANARY_WAIT_TIME_SECS,
            health_check_request_timeout_secs: DEFAULT_HEALTH_CHECK_REQUEST_TIMEOUT_SECS,
        }
    }

    /// Create a new default runtime configuration
    pub(crate) fn create_runtime(&self) -> std::io::Result<tokio::runtime::Runtime> {
        tokio::runtime::Builder::new_multi_thread()
            .worker_threads(
                self.num_worker_threads
                    .unwrap_or_else(|| std::thread::available_parallelism().unwrap().get()),
            )
            .max_blocking_threads(self.max_blocking_threads)
            .enable_all()
            .build()
    }
}

impl Default for RuntimeConfig {
    fn default() -> Self {
        let num_cores = std::thread::available_parallelism().unwrap().get();
        Self {
            num_worker_threads: Some(num_cores),
            max_blocking_threads: num_cores,
            system_host: DEFAULT_SYSTEM_HOST.to_string(),
            system_port: DEFAULT_SYSTEM_PORT,
            #[allow(deprecated)]
            system_enabled: false,
            starting_health_status: HealthStatus::NotReady,
            use_endpoint_health_status: vec![],
            system_health_path: DEFAULT_SYSTEM_HEALTH_PATH.to_string(),
            system_live_path: DEFAULT_SYSTEM_LIVE_PATH.to_string(),
            compute_threads: None,
            compute_stack_size: Some(2 * 1024 * 1024),
            compute_thread_prefix: "compute".to_string(),
            health_check_enabled: false,
            canary_wait_time_secs: DEFAULT_CANARY_WAIT_TIME_SECS,
            health_check_request_timeout_secs: DEFAULT_HEALTH_CHECK_REQUEST_TIMEOUT_SECS,
        }
    }
}

impl RuntimeConfigBuilder {
    /// Build and validate the runtime configuration
    pub fn build(&self) -> Result<RuntimeConfig> {
        let config = self.build_internal()?;
        config.validate()?;
        Ok(config)
    }
}

/// Check if a string is truthy
/// This will be used to evaluate environment variables or any other subjective
/// configuration parameters that can be set by the user that should be evaluated
/// as a boolean value.
pub fn is_truthy(val: &str) -> bool {
    matches!(val.to_lowercase().as_str(), "1" | "true" | "on" | "yes")
}

pub fn parse_bool(val: &str) -> anyhow::Result<bool> {
    if is_truthy(val) {
        Ok(true)
    } else if is_falsey(val) {
        Ok(false)
    } else {
        anyhow::bail!(
            "Invalid boolean value: '{}'. Expected one of: true/false, 1/0, on/off, yes/no",
            val
        )
    }
}

/// Check if a string is falsey
/// This will be used to evaluate environment variables or any other subjective
/// configuration parameters that can be set by the user that should be evaluated
/// as a boolean value (opposite of is_truthy).
pub fn is_falsey(val: &str) -> bool {
    matches!(val.to_lowercase().as_str(), "0" | "false" | "off" | "no")
}

/// Check if an environment variable is truthy
pub fn env_is_truthy(env: &str) -> bool {
    match std::env::var(env) {
        Ok(val) => is_truthy(val.as_str()),
        Err(_) => false,
    }
}

/// Check if an environment variable is falsey
pub fn env_is_falsey(env: &str) -> bool {
    match std::env::var(env) {
        Ok(val) => is_falsey(val.as_str()),
        Err(_) => false,
    }
}

/// Check whether JSONL logging enabled
/// Set the `DYN_LOGGING_JSONL` environment variable a [`is_truthy`] value
pub fn jsonl_logging_enabled() -> bool {
    env_is_truthy(environment_names::logging::DYN_LOGGING_JSONL)
}

/// Check whether logging with ANSI terminal escape codes and colors is disabled.
/// Set the `DYN_SDK_DISABLE_ANSI_LOGGING` environment variable a [`is_truthy`] value
pub fn disable_ansi_logging() -> bool {
    env_is_truthy(environment_names::logging::DYN_SDK_DISABLE_ANSI_LOGGING)
}

/// Check whether to use local timezone for logging timestamps (default is UTC)
/// Set the `DYN_LOG_USE_LOCAL_TZ` environment variable to a [`is_truthy`] value
pub fn use_local_timezone() -> bool {
    env_is_truthy(environment_names::logging::DYN_LOG_USE_LOCAL_TZ)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_runtime_config_with_env_vars() -> Result<()> {
        use environment_names::runtime;
        temp_env::with_vars(
            vec![
                (runtime::DYN_RUNTIME_NUM_WORKER_THREADS, Some("24")),
                (runtime::DYN_RUNTIME_MAX_BLOCKING_THREADS, Some("32")),
            ],
            || {
                let config = RuntimeConfig::from_settings()?;
                assert_eq!(config.num_worker_threads, Some(24));
                assert_eq!(config.max_blocking_threads, 32);
                Ok(())
            },
        )
    }

    #[test]
    fn test_runtime_config_defaults() -> Result<()> {
        use environment_names::runtime;
        temp_env::with_vars(
            vec![
                (runtime::DYN_RUNTIME_NUM_WORKER_THREADS, None::<&str>),
                (runtime::DYN_RUNTIME_MAX_BLOCKING_THREADS, Some("")),
            ],
            || {
                let config = RuntimeConfig::from_settings()?;

                let default_config = RuntimeConfig::default();
                assert_eq!(config.num_worker_threads, default_config.num_worker_threads);
                assert_eq!(
                    config.max_blocking_threads,
                    default_config.max_blocking_threads
                );
                Ok(())
            },
        )
    }

    #[test]
    fn test_runtime_config_rejects_invalid_thread_count() -> Result<()> {
        use environment_names::runtime;
        temp_env::with_vars(
            vec![
                (runtime::DYN_RUNTIME_NUM_WORKER_THREADS, Some("0")),
                (runtime::DYN_RUNTIME_MAX_BLOCKING_THREADS, Some("0")),
            ],
            || {
                let result = RuntimeConfig::from_settings();
                assert!(result.is_err());
                if let Err(e) = result {
                    assert!(
                        e.to_string()
                            .contains("num_worker_threads: Validation error")
                    );
                    assert!(
                        e.to_string()
                            .contains("max_blocking_threads: Validation error")
                    );
                }
                Ok(())
            },
        )
    }

    #[test]
    fn test_runtime_config_system_server_env_vars() -> Result<()> {
        use environment_names::runtime::system;
        temp_env::with_vars(
            vec![
                (system::DYN_SYSTEM_HOST, Some("127.0.0.1")),
                (system::DYN_SYSTEM_PORT, Some("9090")),
            ],
            || {
                let config = RuntimeConfig::from_settings()?;
                assert_eq!(config.system_host, "127.0.0.1");
                assert_eq!(config.system_port, 9090);
                Ok(())
            },
        )
    }

    #[test]
    fn test_system_server_disabled_by_default() {
        use environment_names::runtime::system;
        temp_env::with_vars(vec![(system::DYN_SYSTEM_PORT, None::<&str>)], || {
            let config = RuntimeConfig::from_settings().unwrap();
            assert!(!config.system_server_enabled());
            assert_eq!(config.system_port, -1);
        });
    }

    #[test]
    fn test_system_server_disabled_with_negative_port() {
        use environment_names::runtime::system;
        temp_env::with_vars(vec![(system::DYN_SYSTEM_PORT, Some("-1"))], || {
            let config = RuntimeConfig::from_settings().unwrap();
            assert!(!config.system_server_enabled());
            assert_eq!(config.system_port, -1);
        });
    }

    #[test]
    fn test_system_server_enabled_with_port() {
        use environment_names::runtime::system;
        temp_env::with_vars(vec![(system::DYN_SYSTEM_PORT, Some("9527"))], || {
            let config = RuntimeConfig::from_settings().unwrap();
            assert!(config.system_server_enabled());
            assert_eq!(config.system_port, 9527);
        });
    }

    #[test]
    fn test_system_server_starting_health_status_ready() {
        use environment_names::runtime::system;
        temp_env::with_vars(
            vec![(system::DYN_SYSTEM_STARTING_HEALTH_STATUS, Some("ready"))],
            || {
                let config = RuntimeConfig::from_settings().unwrap();
                assert!(config.starting_health_status == HealthStatus::Ready);
            },
        );
    }

    #[test]
    fn test_system_use_endpoint_health_status() {
        use environment_names::runtime::system;
        temp_env::with_vars(
            vec![(
                system::DYN_SYSTEM_USE_ENDPOINT_HEALTH_STATUS,
                Some("[\"ready\"]"),
            )],
            || {
                let config = RuntimeConfig::from_settings().unwrap();
                assert!(config.use_endpoint_health_status == vec!["ready"]);
            },
        );
    }

    #[test]
    fn test_system_health_endpoint_path_default() {
        use environment_names::runtime::system;
        temp_env::with_vars(vec![(system::DYN_SYSTEM_HEALTH_PATH, None::<&str>)], || {
            let config = RuntimeConfig::from_settings().unwrap();
            assert_eq!(
                config.system_health_path,
                DEFAULT_SYSTEM_HEALTH_PATH.to_string()
            );
        });

        temp_env::with_vars(vec![(system::DYN_SYSTEM_LIVE_PATH, None::<&str>)], || {
            let config = RuntimeConfig::from_settings().unwrap();
            assert_eq!(
                config.system_live_path,
                DEFAULT_SYSTEM_LIVE_PATH.to_string()
            );
        });
    }

    #[test]
    fn test_system_health_endpoint_path_custom() {
        use environment_names::runtime::system;
        temp_env::with_vars(
            vec![(system::DYN_SYSTEM_HEALTH_PATH, Some("/custom/health"))],
            || {
                let config = RuntimeConfig::from_settings().unwrap();
                assert_eq!(config.system_health_path, "/custom/health");
            },
        );

        temp_env::with_vars(
            vec![(system::DYN_SYSTEM_LIVE_PATH, Some("/custom/live"))],
            || {
                let config = RuntimeConfig::from_settings().unwrap();
                assert_eq!(config.system_live_path, "/custom/live");
            },
        );
    }

    #[test]
    fn test_is_truthy_and_falsey() {
        // Test truthy values
        assert!(is_truthy("1"));
        assert!(is_truthy("true"));
        assert!(is_truthy("TRUE"));
        assert!(is_truthy("on"));
        assert!(is_truthy("yes"));

        // Test falsey values
        assert!(is_falsey("0"));
        assert!(is_falsey("false"));
        assert!(is_falsey("FALSE"));
        assert!(is_falsey("off"));
        assert!(is_falsey("no"));

        // Test opposite behavior
        assert!(!is_truthy("0"));
        assert!(!is_falsey("1"));

        // Test env functions
        temp_env::with_vars(vec![("TEST_TRUTHY", Some("true"))], || {
            assert!(env_is_truthy("TEST_TRUTHY"));
            assert!(!env_is_falsey("TEST_TRUTHY"));
        });

        temp_env::with_vars(vec![("TEST_FALSEY", Some("false"))], || {
            assert!(!env_is_truthy("TEST_FALSEY"));
            assert!(env_is_falsey("TEST_FALSEY"));
        });

        // Test missing env vars
        temp_env::with_vars(vec![("TEST_MISSING", None::<&str>)], || {
            assert!(!env_is_truthy("TEST_MISSING"));
            assert!(!env_is_falsey("TEST_MISSING"));
        });
    }
}
