dejavu-cli 0.3.0

Stop showing coding agents the same command output twice.
Documentation 
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//! `DEJAVU_*` environment variable names and the ambient session view.

use std::path::PathBuf;

pub const ACTIVE: &str = "DEJAVU_ACTIVE";
pub const BIN: &str = "DEJAVU_BIN";
pub const REPO_ROOT: &str = "DEJAVU_REPO_ROOT";
pub const CACHE_DIR: &str = "DEJAVU_CACHE_DIR";
pub const SESSION_ID: &str = "DEJAVU_SESSION_ID";
pub const SHIM_DIR: &str = "DEJAVU_SHIM_DIR";
pub const MODE: &str = "DEJAVU";
pub const DISABLED: &str = "DEJAVU_DISABLED";
/// Force reduction even outside a session / agent context (`DEJAVU_FORCE=1`).
pub const FORCE: &str = "DEJAVU_FORCE";
/// The user's original ZDOTDIR (or $HOME), sourced by the wrapper zdot files.
pub const ORIG_ZDOTDIR: &str = "DEJAVU_ORIG_ZDOTDIR";

/// Environment markers that IDE-embedded agents set in the shells they drive.
/// `AI_AGENT` is the cross-vendor convention (VS Code sets
/// `AI_AGENT=github_copilot_vscode_agent` + `COPILOT_AGENT=1` in agent-tool
/// terminals only, never in user terminals).
pub const AGENT_MARKERS: &[&str] = &[
    "AI_AGENT",
    "COPILOT_AGENT",
    "CLAUDECODE",
    "CODEX_SANDBOX",
    "CURSOR_AGENT",
];

/// True when the user asks Dejavu to force passthrough everywhere.
pub fn is_disabled() -> bool {
    let legacy_flag = std::env::var_os(DISABLED).is_some_and(|v| v == "1");
    let mode_off = std::env::var_os(MODE).is_some_and(|v| {
        matches!(
            v.to_string_lossy().to_ascii_lowercase().as_str(),
            "off" | "0" | "false" | "disabled"
        )
    });
    legacy_flag || mode_off
}

/// True when running inside a `dejavu start` session.
pub fn is_active() -> bool {
    std::env::var_os(ACTIVE).is_some_and(|v| v == "1")
}

/// True when `DEJAVU_FORCE=1` overrides the global-mode reduction gates.
pub fn is_forced() -> bool {
    std::env::var_os(FORCE).is_some_and(|v| v == "1")
}

/// True when an agent marker is present in the environment (an IDE-embedded
/// agent is driving this shell).
pub fn agent_marker_present() -> bool {
    AGENT_MARKERS
        .iter()
        .any(|m| std::env::var_os(m).is_some_and(|v| !v.is_empty()))
}

/// Whether output reduction is allowed for this invocation.
///
/// - Inside a `dejavu start` session: always (the agent captures via pipes).
/// - `DEJAVU_FORCE=1`: always (explicit human election).
/// - Global activation (shims on PATH, no session): only when an agent marker
///   is present AND stdout is a terminal. IDE agents like Copilot run commands
///   in a real pty, while programs that PARSE output (`$(git …)`, pipelines,
///   the IDE SCM) read through pipes — so this pair of gates means a reduced
///   envelope can only ever land in front of an agent, never a parser.
pub fn reduction_allowed(stdout_is_tty: bool) -> bool {
    is_active() || is_forced() || (agent_marker_present() && stdout_is_tty)
}

/// The ambient session, reconstructed from `DEJAVU_*` env vars. `None` when a
/// shim is somehow invoked outside a session.
#[derive(Debug, Clone)]
pub struct AgentEnv {
    pub bin: PathBuf,
    pub repo_root: PathBuf,
    pub cache_dir: PathBuf,
    pub session_id: String,
    pub shim_dir: PathBuf,
}

impl AgentEnv {
    pub fn from_current() -> Option<AgentEnv> {
        Some(AgentEnv {
            bin: std::env::var_os(BIN)?.into(),
            repo_root: std::env::var_os(REPO_ROOT)?.into(),
            cache_dir: std::env::var_os(CACHE_DIR)?.into(),
            session_id: std::env::var_os(SESSION_ID)?.to_string_lossy().into_owned(),
            shim_dir: std::env::var_os(SHIM_DIR)?.into(),
        })
    }
}