//! Daemon view over the unified Maestro config.
//!
//! Reads `[daemon]` (hostname, bind_addr, state_dir, worktree_root, …) and
//! `[spawn]` from `~/.config/maestro/config.toml`.
//!
//! Precedence per field: **env > file > default**. Every field has a default,
//! so a missing config file is fine — the daemon starts with defaults.
//!
//! Default config path: `~/.config/maestro/config.toml` (override via
//! `$MAESTRO_CONFIG`).

use std::net::SocketAddr;
use std::path::{Path, PathBuf};

use maestro_config::MaestroConfigFile;

pub use maestro_config::default_config_path;

/// Default bind address when neither env nor file specify one.
pub const DEFAULT_BIND_ADDR: &str = "127.0.0.1:7070";

/// Default recency cap (days) for the durable spawn history (#24) when
/// `[daemon].spawn_history_days` is unset. `0` in config disables history.
pub const DEFAULT_SPAWN_HISTORY_DAYS: u32 = 30;

/// Default scan roots for project discovery (#54) when `[spawn].project_roots`
/// is unset: the whole home directory, with the scanner's own ignore list
/// keeping it cheap.
pub const DEFAULT_PROJECT_ROOTS: [&str; 1] = ["~"];
/// Default directory depth for project discovery (#54) when
/// `[spawn].project_scan_depth` is unset.
pub const DEFAULT_PROJECT_SCAN_DEPTH: u32 = 3;

/// Env var that overrides `[daemon].bind_addr`.
pub const ENV_DAEMON_BIND_ADDR: &str = "MAESTRO_DAEMON_BIND_ADDR";
/// Env var that overrides `[daemon].tmux_tmpdir`.
pub const ENV_DAEMON_TMUX_TMPDIR: &str = "MAESTRO_DAEMON_TMUX_TMPDIR";

fn default_bind_addr() -> SocketAddr {
    DEFAULT_BIND_ADDR.parse().expect("valid default bind_addr")
}

#[derive(Debug, thiserror::Error)]
pub enum ConfigError {
    #[error(transparent)]
    Inner(#[from] maestro_config::ConfigError),
    #[error("io: {0}")]
    Io(#[from] std::io::Error),
    #[error("invalid [spawn].presets: {0}")]
    SpawnPresets(#[from] maestro_config::SpawnConfigError),
}

/// Resolved, validated daemon configuration ready to drive the binary.
#[derive(Debug, Clone)]
pub struct DaemonConfig {
    /// Hostname advertised to clients, for display only.
    pub hostname: String,
    /// Home directory of the OS user the daemon runs as, advertised to clients
    /// so they can prefill a spawn form's working directory. Empty when `$HOME`
    /// can't be resolved (NAP-328).
    pub home_dir: String,
    pub bind_addr: SocketAddr,
    pub state_dir: PathBuf,
    /// `[daemon].worktree_root` override (#56). `None` — the default — places
    /// worktrees inside their base repo at `<repo>/worktrees/<branch>`;
    /// operators who want them elsewhere set this.
    pub worktree_root: Option<PathBuf>,
    /// Per-session PTY replay buffer cap in bytes (NAP-229). Each new attach
    /// receives this much of the prior PTY output before the live stream.
    /// Default `pty::DEFAULT_REPLAY_BYTES`; `0` disables.
    pub pty_replay_bytes: usize,
    /// `TMUX_TMPDIR` exported for every `tmux` invocation (NAP-234).
    /// `None` lets tmux pick its own default (`/tmp/tmux-$UID`); `Some(p)`
    /// forces sockets under `p` so bare `tmux ls` in a matching user shell
    /// sees maestro sessions.
    pub tmux_tmpdir: Option<PathBuf>,
    /// Recency cap (days) for the durable spawn history that backs the spawn
    /// form's "recent dirs" picker (#24). `0` disables history. Default
    /// [`DEFAULT_SPAWN_HISTORY_DAYS`].
    pub spawn_history_days: u32,
    /// Resolved spawn-form command presets (#22/#26): `[spawn].presets` (or the
    /// built-ins) with the implicit `custom` tile appended. Advertised to
    /// clients in `GET /api/info`.
    pub spawn_presets: Vec<maestro_config::SpawnPreset>,
    /// Project-discovery scan roots (#54): `[spawn].project_roots` (default
    /// [`DEFAULT_PROJECT_ROOTS`]) with `~` expanded against the daemon's home.
    pub project_roots: Vec<PathBuf>,
    /// Project-discovery depth (#54): `[spawn].project_scan_depth`, default
    /// [`DEFAULT_PROJECT_SCAN_DEPTH`].
    pub project_scan_depth: u32,
    /// Whether the daemon installs the Claude Code activity hook on first
    /// start when none is present (#106): `[hooks].auto_install`, default
    /// `true`.
    pub hooks_auto_install: bool,
    /// Canonical leader key advertised to clients in `GET /api/info` (#159):
    /// `[tui].leader`, default [`maestro_config::DEFAULT_LEADER`]. The daemon
    /// never binds it itself; it serves it so the web client and the TUI read
    /// one knob.
    pub leader: String,
}

impl DaemonConfig {
    pub fn sidecar_dir(&self) -> PathBuf {
        self.state_dir.join("sessions")
    }

    pub fn fifo_dir(&self) -> PathBuf {
        self.state_dir.join("fifos")
    }

    /// JSONL spawn-history log path (#24): `<state_dir>/spawn-history.jsonl`.
    pub fn spawn_history_path(&self) -> PathBuf {
        self.state_dir.join("spawn-history.jsonl")
    }
}

/// Env-var overrides applied by [`load_config`]. Tests pass explicit
/// `Option`s; production reads from real env vars in `main`.
#[derive(Debug, Clone, Default)]
pub struct EnvOverrides {
    pub bind_addr: Option<String>,
    pub tmux_tmpdir: Option<String>,
}

impl EnvOverrides {
    /// Read every supported env var from the process environment.
    pub fn from_env() -> Self {
        Self {
            bind_addr: std::env::var(ENV_DAEMON_BIND_ADDR).ok(),
            tmux_tmpdir: std::env::var(ENV_DAEMON_TMUX_TMPDIR).ok(),
        }
    }
}

/// Resolve the runtime configuration: env overrides on top of the unified
/// file, then defaults. A missing file is not an error.
pub fn load_config(path: &Path, env: EnvOverrides) -> Result<DaemonConfig, ConfigError> {
    let file = MaestroConfigFile::load(path)?;

    let daemon = file.daemon;
    // Resolve spawn presets up front so a bad `[spawn].presets` (empty/dup id,
    // empty command) refuses startup with a clear error, like other config
    // validation (#22/#26).
    let spawn_presets = file.spawn.resolve()?;

    let hostname = daemon.hostname.unwrap_or_else(system_hostname);
    let home_dir = dirs::home_dir()
        .map(|p| p.to_string_lossy().into_owned())
        .unwrap_or_default();

    let bind_addr = match env.bind_addr {
        Some(raw) => maestro_config::parse_bind_addr(&raw, ENV_DAEMON_BIND_ADDR)?,
        None => daemon.bind_addr.unwrap_or_else(default_bind_addr),
    };

    let state_dir = match daemon.state_dir {
        Some(p) => p,
        None => default_state_dir()?,
    };

    let pty_replay_bytes = daemon
        .pty_replay_bytes
        .unwrap_or(crate::pty::DEFAULT_REPLAY_BYTES);
    let tmux_tmpdir = env
        .tmux_tmpdir
        .map(PathBuf::from)
        .or(daemon.tmux_tmpdir)
        .or_else(dirs::runtime_dir);
    let spawn_history_days = daemon
        .spawn_history_days
        .unwrap_or(DEFAULT_SPAWN_HISTORY_DAYS);

    // `~` in scan roots means the daemon's own home; an unresolvable home
    // leaves the tilde as-is and the scanner treats the root as missing.
    let project_roots: Vec<PathBuf> = file
        .spawn
        .project_roots
        .unwrap_or_else(|| {
            DEFAULT_PROJECT_ROOTS
                .iter()
                .map(|s| s.to_string())
                .collect()
        })
        .iter()
        .map(|root| expand_tilde(root, &home_dir))
        .collect();
    let project_scan_depth = file
        .spawn
        .project_scan_depth
        .unwrap_or(DEFAULT_PROJECT_SCAN_DEPTH);

    Ok(DaemonConfig {
        hostname,
        home_dir,
        bind_addr,
        state_dir,
        worktree_root: daemon.worktree_root,
        pty_replay_bytes,
        tmux_tmpdir,
        spawn_history_days,
        spawn_presets,
        project_roots,
        project_scan_depth,
        hooks_auto_install: file.hooks.auto_install(),
        leader: file.tui.leader().to_string(),
    })
}

/// Expand a leading `~` (or `~/…`) against `home`. Other paths pass through.
fn expand_tilde(path: &str, home: &str) -> PathBuf {
    match path.strip_prefix("~") {
        Some(_) if home.is_empty() => PathBuf::from(path),
        Some(rest) => {
            let mut p = PathBuf::from(home);
            p.push(rest.trim_start_matches('/'));
            p
        }
        None => PathBuf::from(path),
    }
}

pub fn default_state_dir() -> Result<PathBuf, ConfigError> {
    Ok(maestro_config::default_state_dir("maestro")?)
}

/// Read the kernel hostname via `gethostname(2)`. Falls back to `"unknown"`
/// on the (very unlikely) syscall failure.
pub fn system_hostname() -> String {
    let mut buf = [0u8; 256];
    let r = unsafe { libc::gethostname(buf.as_mut_ptr().cast(), buf.len()) };
    if r != 0 {
        return "unknown".into();
    }
    let nul = buf.iter().position(|&b| b == 0).unwrap_or(buf.len());
    String::from_utf8_lossy(&buf[..nul]).into_owned()
}

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

    /// #159: the leader the operator set for the TUI is what the daemon
    /// advertises, so rebinding it once moves both clients' chord.
    #[test]
    fn leader_defaults_to_ctrl_a_and_follows_the_tui_section() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");

        std::fs::write(&path, "").unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.leader, "ctrl-a");

        std::fs::write(
            &path,
            r#"
[tui]
leader = "ctrl-b"
"#,
        )
        .unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.leader, "ctrl-b");
    }

    #[test]
    fn hooks_auto_install_defaults_true_and_is_opt_out() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");

        std::fs::write(&path, "").unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert!(cfg.hooks_auto_install);

        std::fs::write(
            &path,
            r#"
[hooks]
auto_install = false
"#,
        )
        .unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert!(!cfg.hooks_auto_install);
    }

    #[test]
    fn empty_file_defaults_everything() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(&path, "").unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.bind_addr, default_bind_addr());
        assert!(cfg.state_dir.ends_with("maestro"));
        assert!(cfg.worktree_root.is_none());
        assert!(!cfg.hostname.is_empty());
    }

    #[test]
    fn missing_file_is_not_an_error() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("does-not-exist.toml");
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.bind_addr, default_bind_addr());
        assert!(!path.exists(), "load_config must not create the file");
    }

    #[test]
    fn env_overrides_file() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(
            &path,
            r#"
[daemon]
bind_addr = "127.0.0.1:1"
"#,
        )
        .unwrap();
        let env = EnvOverrides {
            bind_addr: Some("0.0.0.0:9999".into()),
            ..EnvOverrides::default()
        };
        let cfg = load_config(&path, env).unwrap();
        assert_eq!(cfg.bind_addr, "0.0.0.0:9999".parse().unwrap());
    }

    #[test]
    fn invalid_env_bind_addr_returns_diagnostic() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(&path, "").unwrap();
        let env = EnvOverrides {
            bind_addr: Some("not-an-addr".into()),
            ..EnvOverrides::default()
        };
        let err = load_config(&path, env).unwrap_err();
        match err {
            ConfigError::Inner(maestro_config::ConfigError::InvalidBindAddr {
                input, env, ..
            }) => {
                assert_eq!(input, "not-an-addr");
                assert_eq!(env, ENV_DAEMON_BIND_ADDR);
            }
            other => panic!("expected InvalidBindAddr, got {other:?}"),
        }
    }

    #[test]
    fn hostname_from_file_wins_over_gethostname() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(
            &path,
            r#"
[daemon]
hostname = "vm-42"
"#,
        )
        .unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.hostname, "vm-42");
    }

    #[test]
    fn spawn_history_days_defaults_and_overrides() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");

        std::fs::write(&path, "").unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.spawn_history_days, DEFAULT_SPAWN_HISTORY_DAYS);
        assert!(cfg.spawn_history_path().ends_with("spawn-history.jsonl"));

        std::fs::write(
            &path,
            r#"
[daemon]
spawn_history_days = 0
"#,
        )
        .unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.spawn_history_days, 0);
    }

    #[test]
    fn project_scan_defaults_to_home_root_at_depth_3() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(&path, "").unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.project_scan_depth, DEFAULT_PROJECT_SCAN_DEPTH);
        assert_eq!(
            cfg.project_roots,
            vec![PathBuf::from(cfg.home_dir.clone())],
            "bare ~ must expand to the daemon's home"
        );
    }

    #[test]
    fn project_scan_roots_expand_tilde_and_pass_through_absolutes() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(
            &path,
            r#"
[spawn]
project_roots = ["~/code", "/srv/work"]
project_scan_depth = 5
"#,
        )
        .unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.project_scan_depth, 5);
        assert_eq!(
            cfg.project_roots,
            vec![
                PathBuf::from(cfg.home_dir.clone()).join("code"),
                PathBuf::from("/srv/work"),
            ]
        );
    }

    #[test]
    fn tilde_expansion_handles_bare_and_nested_forms() {
        assert_eq!(expand_tilde("~", "/home/u"), PathBuf::from("/home/u"));
        assert_eq!(
            expand_tilde("~/a/b", "/home/u"),
            PathBuf::from("/home/u/a/b")
        );
        assert_eq!(expand_tilde("/abs", "/home/u"), PathBuf::from("/abs"));
        // Unresolvable home leaves the tilde as-is rather than mangling it.
        assert_eq!(expand_tilde("~", ""), PathBuf::from("~"));
    }

    #[test]
    fn system_hostname_is_nonempty() {
        let h = system_hostname();
        assert!(!h.is_empty(), "gethostname returned empty string");
    }

    // NAP-234: tmux_tmpdir precedence is env > file > dirs::runtime_dir().
    // Tested without mutating the process env (which races other tests) by
    // feeding `EnvOverrides` directly.

    #[test]
    fn tmux_tmpdir_env_beats_file_and_runtime_dir() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(
            &path,
            r#"
[daemon]
tmux_tmpdir = "/from-file"
"#,
        )
        .unwrap();
        let env = EnvOverrides {
            tmux_tmpdir: Some("/from-env".into()),
            ..EnvOverrides::default()
        };
        let cfg = load_config(&path, env).unwrap();
        assert_eq!(cfg.tmux_tmpdir.as_deref(), Some(Path::new("/from-env")));
    }

    #[test]
    fn tmux_tmpdir_file_beats_runtime_dir() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(
            &path,
            r#"
[daemon]
tmux_tmpdir = "/from-file"
"#,
        )
        .unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        assert_eq!(cfg.tmux_tmpdir.as_deref(), Some(Path::new("/from-file")));
    }

    #[test]
    fn tmux_tmpdir_defaults_to_xdg_runtime_dir_when_unset() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.toml");
        std::fs::write(&path, "").unwrap();
        let cfg = load_config(&path, EnvOverrides::default()).unwrap();
        // dirs::runtime_dir() is `Some(_)` on any Linux host with
        // $XDG_RUNTIME_DIR set (CI included). When it's `None`, the daemon
        // falls through to None and tmux uses /tmp; either is acceptable —
        // but on this test runner the env var is always present.
        assert_eq!(cfg.tmux_tmpdir, dirs::runtime_dir());
    }
}