agentsec_core/

config.rs

//! Edge-resolved configuration.
//!
//! [`Config`] is the single value that carries all environment-derived
//! state through the crate. Library code **never** reads `std::env`
//! directly — the binary's `main` resolves the env once into a [`Config`]
//! and passes `&Config` down the call graph.
//!
//! ## Why this lives here
//!
//! Env reads are a side effect of the process boundary. Putting them in
//! library functions makes the library:
//!
//! - **unsafe to test in parallel** (process env is global mutable state)
//! - **dependent on global ordering** (which fn ran first wins)
//! - **untestable without `unsafe { set_var }`** in tests
//!
//! By contrast, with `Config` resolved once at the outer rim and threaded
//! through as `&Config`:
//!
//! - tests construct a `Config` with literal field values; no env writes
//! - the only place that needs env-mock testing is
//!   [`Config::from_env_lookup`], which is a pure function over an
//!   injectable lookup closure
//! - the binary's `main` is the *only* place that calls
//!   [`Config::from_env`] (= `std::env::var`)
//!
//! ## What env vars are read
//!
//! | Var                  | Field                                  | Default                                  |
//! |----------------------|----------------------------------------|------------------------------------------|
//! | `AGENTSEC_HOME`      | [`Paths::home`]                        | `$HOME/.agentsec` ↓                      |
//! | `HOME`               | [`Paths::user_home`] (and home fallback) | `.`                                    |
//! | `ANTHROPIC_API_KEY`  | [`LlmConfig::api_key`]                 | `None` (semantic sanitize layer no-op)   |
//! | `AGENTSEC_LLM_MODEL` | [`LlmConfig::model`]                   | `claude-haiku-4-5-20251001`              |

use std::path::PathBuf;

/// Default LLM model id used when `AGENTSEC_LLM_MODEL` is not set.
pub const DEFAULT_LLM_MODEL: &str = "claude-haiku-4-5-20251001";

/// All edge-resolved runtime configuration. Constructed once by the
/// binary's `main` and passed by reference to library functions.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Config {
    /// Filesystem paths AgentSec reads / writes.
    pub paths: Paths,
    /// LLM-backed sanitize layer configuration.
    pub llm: LlmConfig,
}

/// Filesystem paths. See *crate root §Runtime data root* for the layout
/// rules and *crate root §Read-only invariants* for what may / may not
/// be written.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Paths {
    /// AgentSec runtime data root (`$AGENTSEC_HOME` or `$HOME/.agentsec`).
    pub home: PathBuf,
    /// The user's home directory (`$HOME`). Used by
    /// [`crate::scan::inventory`] to build absolute paths for the
    /// `~/.claude/*` target list. Distinct from [`Self::home`].
    pub user_home: PathBuf,
}

impl Paths {
    /// `<home>/snapshots/` — scan snapshot files.
    pub fn snapshots(&self) -> PathBuf {
        self.home.join("snapshots")
    }
    /// `<home>/scans/` — SessionStart hook summary.
    pub fn scans(&self) -> PathBuf {
        self.home.join("scans")
    }
    /// `<home>/web_log/` — one JSON row per `web::fetch_and_sanitize`.
    pub fn web_log(&self) -> PathBuf {
        self.home.join("web_log")
    }
    /// `<home>/paste_log/` — one JSON row per `paste::detect`.
    pub fn paste_log(&self) -> PathBuf {
        self.home.join("paste_log")
    }
}

/// Semantic-sanitize-layer configuration. See
/// [`crate::web::sanitize::semantic_layer`] for fail-open semantics.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct LlmConfig {
    /// Anthropic API key. `None` ⇒ the semantic layer is a no-op (the
    /// regex layer alone protects).
    pub api_key: Option<String>,
    /// Anthropic model id for the semantic layer. Defaults to
    /// [`DEFAULT_LLM_MODEL`].
    pub model: String,
}

impl Config {
    /// Build a [`Config`] by reading process environment variables.
    ///
    /// **This is the only function in the crate that touches
    /// `std::env`.** Call it once at the binary's outer rim
    /// (`fn main`) and thread `&Config` through everything else.
    pub fn from_env() -> Self {
        Self::from_env_lookup(|k| std::env::var(k).ok())
    }

    /// Build a [`Config`] from an arbitrary lookup closure.
    ///
    /// Pure function over the injected lookup — exposed so tests can pass
    /// a `HashMap`-backed closure and verify the parse rules without
    /// touching real process env.
    ///
    /// # Examples
    ///
    /// ```
    /// use agentsec_core::config::{Config, DEFAULT_LLM_MODEL};
    /// use std::collections::HashMap;
    ///
    /// let env: HashMap<&str, &str> = [
    ///     ("AGENTSEC_HOME", "/tmp/agentsec-test"),
    ///     ("HOME", "/home/test-user"),
    /// ]
    /// .into_iter()
    /// .collect();
    ///
    /// let cfg = Config::from_env_lookup(|k| env.get(k).map(|s| s.to_string()));
    /// assert_eq!(cfg.paths.home, std::path::PathBuf::from("/tmp/agentsec-test"));
    /// assert_eq!(cfg.paths.user_home, std::path::PathBuf::from("/home/test-user"));
    /// assert_eq!(cfg.llm.api_key, None);
    /// assert_eq!(cfg.llm.model, DEFAULT_LLM_MODEL);
    /// ```
    pub fn from_env_lookup<F>(lookup: F) -> Self
    where
        F: Fn(&str) -> Option<String>,
    {
        let user_home = lookup("HOME").unwrap_or_else(|| ".".into());
        let home = lookup("AGENTSEC_HOME").map_or_else(
            || PathBuf::from(&user_home).join(".agentsec"),
            PathBuf::from,
        );
        let user_home = PathBuf::from(user_home);

        let api_key = lookup("ANTHROPIC_API_KEY").filter(|s| !s.is_empty());
        let model = lookup("AGENTSEC_LLM_MODEL").unwrap_or_else(|| DEFAULT_LLM_MODEL.to_string());

        Self {
            paths: Paths { home, user_home },
            llm: LlmConfig { api_key, model },
        }
    }
}

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

    fn map_lookup<'a>(pairs: &'a [(&'a str, &'a str)]) -> impl Fn(&str) -> Option<String> + 'a {
        let map: HashMap<&str, &str> = pairs.iter().copied().collect();
        move |k| map.get(k).map(|s| (*s).to_string())
    }

    #[test]
    fn empty_env_uses_all_defaults() {
        let cfg = Config::from_env_lookup(|_| None);
        // No HOME ⇒ user_home falls back to ".".
        assert_eq!(cfg.paths.user_home, PathBuf::from("."));
        // No AGENTSEC_HOME ⇒ home falls back to ./.agentsec.
        assert_eq!(cfg.paths.home, PathBuf::from("./.agentsec"));
        assert_eq!(cfg.llm.api_key, None);
        assert_eq!(cfg.llm.model, DEFAULT_LLM_MODEL);
    }

    #[test]
    fn home_only_derives_agentsec_home() {
        let cfg = Config::from_env_lookup(map_lookup(&[("HOME", "/home/alice")]));
        assert_eq!(cfg.paths.user_home, PathBuf::from("/home/alice"));
        assert_eq!(cfg.paths.home, PathBuf::from("/home/alice/.agentsec"));
    }

    #[test]
    fn agentsec_home_overrides_default() {
        let cfg = Config::from_env_lookup(map_lookup(&[
            ("HOME", "/home/alice"),
            ("AGENTSEC_HOME", "/var/lib/agentsec"),
        ]));
        assert_eq!(cfg.paths.home, PathBuf::from("/var/lib/agentsec"));
        // user_home is untouched by AGENTSEC_HOME — they're distinct.
        assert_eq!(cfg.paths.user_home, PathBuf::from("/home/alice"));
    }

    #[test]
    fn paths_methods_join_under_home() {
        let cfg = Config::from_env_lookup(map_lookup(&[("AGENTSEC_HOME", "/tmp/x")]));
        assert_eq!(cfg.paths.snapshots(), PathBuf::from("/tmp/x/snapshots"));
        assert_eq!(cfg.paths.scans(), PathBuf::from("/tmp/x/scans"));
        assert_eq!(cfg.paths.web_log(), PathBuf::from("/tmp/x/web_log"));
        assert_eq!(cfg.paths.paste_log(), PathBuf::from("/tmp/x/paste_log"));
    }

    #[test]
    fn empty_api_key_treated_as_absent() {
        // Some shells export ANTHROPIC_API_KEY= when the secret isn't
        // configured; an empty string must not flip the semantic layer on.
        let cfg = Config::from_env_lookup(map_lookup(&[("ANTHROPIC_API_KEY", "")]));
        assert_eq!(cfg.llm.api_key, None);
    }

    #[test]
    fn api_key_and_model_are_picked_up() {
        let cfg = Config::from_env_lookup(map_lookup(&[
            ("ANTHROPIC_API_KEY", "sk-test"),
            ("AGENTSEC_LLM_MODEL", "claude-sonnet-4-6"),
        ]));
        assert_eq!(cfg.llm.api_key, Some("sk-test".to_string()));
        assert_eq!(cfg.llm.model, "claude-sonnet-4-6");
    }
}