remem-ai 0.6.79

use std::cell::RefCell;
use std::ffi::OsString;
use std::path::{Path, PathBuf};

use anyhow::{anyhow, Result};

thread_local! {
    static DATA_DIR_OVERRIDE: RefCell<Option<PathBuf>> = const { RefCell::new(None) };
    #[cfg(test)]
    static HOME_DIR_OVERRIDE: RefCell<Option<Option<PathBuf>>> = const { RefCell::new(None) };
}

pub(crate) fn with_data_dir<T>(dir: &Path, f: impl FnOnce() -> T) -> T {
    let _guard = DataDirOverrideGuard::set(dir.to_path_buf());
    f()
}

#[cfg(test)]
pub fn data_dir() -> PathBuf {
    try_data_dir().unwrap_or_else(|error| panic!("{error}"))
}

pub fn try_data_dir() -> Result<PathBuf> {
    resolve_data_dir(
        DATA_DIR_OVERRIDE.with(|slot| slot.borrow().clone()),
        std::env::var_os("REMEM_DATA_DIR"),
        resolved_home_dir(),
    )
}

#[cfg(not(test))]
fn resolved_home_dir() -> Option<PathBuf> {
    dirs::home_dir()
}

#[cfg(test)]
fn resolved_home_dir() -> Option<PathBuf> {
    HOME_DIR_OVERRIDE
        .with(|slot| slot.borrow().clone())
        .unwrap_or_else(dirs::home_dir)
}

#[cfg(test)]
struct HomeDirOverrideGuard {
    previous: Option<Option<PathBuf>>,
}

#[cfg(test)]
impl HomeDirOverrideGuard {
    fn set(value: Option<PathBuf>) -> Self {
        let previous = HOME_DIR_OVERRIDE.with(|slot| slot.replace(Some(value)));
        Self { previous }
    }
}

#[cfg(test)]
impl Drop for HomeDirOverrideGuard {
    fn drop(&mut self) {
        let previous = self.previous.take();
        HOME_DIR_OVERRIDE.with(|slot| slot.replace(previous));
    }
}

/// Resolves the remem data directory from an explicit override,
/// `REMEM_DATA_DIR`, or the home directory. The database and SQLCipher key live
/// under this directory, so a cwd fallback would silently place key material in
/// an unexpected location and split the store from `~/.remem`. A missing home
/// directory without an explicit override is an unrecoverable misconfiguration:
/// fail closed.
pub(crate) fn resolve_data_dir(
    override_path: Option<PathBuf>,
    remem_data_dir: Option<OsString>,
    home_dir: Option<PathBuf>,
) -> Result<PathBuf> {
    if let Some(path) = override_path {
        return Ok(path);
    }
    if let Some(path) = remem_data_dir.filter(|value| !value.is_empty()) {
        return Ok(PathBuf::from(path));
    }
    home_dir
        .map(|home| home.join(".remem"))
        .ok_or_else(|| anyhow!("cannot resolve remem data dir: HOME is unset; set REMEM_DATA_DIR"))
}

struct DataDirOverrideGuard {
    previous: Option<PathBuf>,
}

impl DataDirOverrideGuard {
    fn set(path: PathBuf) -> Self {
        let previous = DATA_DIR_OVERRIDE.with(|slot| slot.replace(Some(path)));
        Self { previous }
    }
}

impl Drop for DataDirOverrideGuard {
    fn drop(&mut self) {
        let previous = self.previous.take();
        DATA_DIR_OVERRIDE.with(|slot| {
            slot.replace(previous);
        });
    }
}

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

    struct EnvRestore {
        config: Option<OsString>,
        data_dir: Option<OsString>,
        home: Option<OsString>,
    }

    impl Drop for EnvRestore {
        fn drop(&mut self) {
            unsafe {
                match self.config.take() {
                    Some(value) => std::env::set_var("REMEM_CONFIG", value),
                    None => std::env::remove_var("REMEM_CONFIG"),
                }
                match self.data_dir.take() {
                    Some(value) => std::env::set_var("REMEM_DATA_DIR", value),
                    None => std::env::remove_var("REMEM_DATA_DIR"),
                }
                match self.home.take() {
                    Some(value) => std::env::set_var("HOME", value),
                    None => std::env::remove_var("HOME"),
                }
            }
        }
    }

    #[test]
    fn resolve_data_dir_prefers_override_then_env_then_home() {
        let override_path = PathBuf::from("/tmp/override");
        assert_eq!(
            resolve_data_dir(
                Some(override_path.clone()),
                Some(OsString::from("/tmp/env")),
                Some(PathBuf::from("/home/user")),
            )
            .unwrap(),
            override_path
        );
        assert_eq!(
            resolve_data_dir(
                None,
                Some("/tmp/env".into()),
                Some(PathBuf::from("/home/user"))
            )
            .unwrap(),
            PathBuf::from("/tmp/env")
        );
        assert_eq!(
            resolve_data_dir(None, None, Some(PathBuf::from("/home/user"))).unwrap(),
            PathBuf::from("/home/user/.remem")
        );
    }

    #[test]
    fn resolve_data_dir_uses_env_even_without_home() {
        assert_eq!(
            resolve_data_dir(None, Some(OsString::from("/tmp/env")), None).unwrap(),
            PathBuf::from("/tmp/env")
        );
    }

    #[test]
    fn resolve_data_dir_ignores_empty_env_and_falls_back_to_home() {
        assert_eq!(
            resolve_data_dir(
                None,
                Some(OsString::new()),
                Some(PathBuf::from("/home/user"))
            )
            .unwrap(),
            PathBuf::from("/home/user/.remem")
        );
    }

    #[test]
    fn resolve_data_dir_fails_closed_without_home_or_env() {
        let error = resolve_data_dir(None, None, None).unwrap_err().to_string();
        assert!(error.contains("HOME is unset"));
        assert!(error.contains("REMEM_DATA_DIR"));
        assert!(!error.contains(".remem"));
    }

    #[test]
    fn production_path_apis_return_errors_without_home_or_data_dir() {
        let _lock = crate::runtime_config::TEST_ENV_LOCK
            .lock()
            .expect("env lock");
        let _restore = EnvRestore {
            config: std::env::var_os("REMEM_CONFIG"),
            data_dir: std::env::var_os("REMEM_DATA_DIR"),
            home: std::env::var_os("HOME"),
        };
        unsafe {
            std::env::remove_var("REMEM_CONFIG");
            std::env::remove_var("REMEM_DATA_DIR");
            std::env::remove_var("HOME");
        }
        let _home_override = HomeDirOverrideGuard::set(None);

        let db_error = crate::db::try_db_path().unwrap_err().to_string();
        let config_error = crate::runtime_config::config_path()
            .unwrap_err()
            .to_string();
        assert!(db_error.contains("HOME is unset"), "{db_error}");
        assert!(config_error.contains("HOME is unset"), "{config_error}");
    }
}