//! Per-agent tool-group configuration. Stored at
//! `/var/lib/hyperhive/meta/tool-groups.json` alongside `topology.json`
//! and the meta `flake.nix`.
//!
//! Format: a JSON object mapping agent name to an array of
//! `hive_sh4re::ToolGroup` snake_case strings:
//!
//! ```json
//! {
//!   "alice": ["messaging", "meta", "inbox", "lifecycle"],
//!   "bob":   ["messaging", "meta", "inbox"]
//! }
//! ```
//!
//! An absent entry (or an absent file) means "use the harness role
//! default" — agents get `messaging + meta + inbox`, the manager gets
//! all groups. `render_flake` in `meta.rs` reads this file and
//! injects `HIVE_TOOL_GROUPS` into each agent's systemd service env;
//! agents with no entry get no env var and the harness falls back.
//!
//! Write path: `set_groups` is called from the dashboard action handler
//! that the operator uses to grant/revoke tool groups per agent.
//! The manager may also request group changes via an approval; hive-c0re
//! applies the change on approval, commits the file, and cascades a rebuild.

use std::collections::BTreeMap;
use std::path::PathBuf;

const TOOL_GROUPS_FILE: &str = "tool-groups.json";

#[must_use]
pub fn tool_groups_path() -> PathBuf {
    crate::meta::meta_dir().join(TOOL_GROUPS_FILE)
}

/// Read the per-agent tool-group map. Returns an empty map when the
/// file is absent or unparsable — callers treat a missing entry as
/// "use role default".
#[must_use]
pub fn read() -> BTreeMap<String, Vec<String>> {
    let path = tool_groups_path();
    let Ok(raw) = std::fs::read_to_string(&path) else {
        return BTreeMap::new();
    };
    serde_json::from_str(&raw).unwrap_or_default()
}

/// Look up the configured tool groups for one agent. Returns an empty
/// vec when the agent has no entry — callers should treat this as
/// "use the harness role default."
#[must_use]
pub fn groups_for(name: &str) -> Vec<String> {
    read().get(name).cloned().unwrap_or_default()
}

/// Persist the full tool-groups map. Sorted JSON output keeps diffs
/// minimal. Best-effort — returns `io::Error` so callers decide
/// whether to abort or log.
pub fn write(map: &BTreeMap<String, Vec<String>>) -> std::io::Result<()> {
    let path = tool_groups_path();
    if let Some(parent) = path.parent() {
        std::fs::create_dir_all(parent)?;
    }
    let text = serde_json::to_string_pretty(map)
        .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
    std::fs::write(&path, format!("{text}\n"))
}

/// Set the tool groups for one agent and persist the map. An empty
/// `groups` vec removes the entry (agent reverts to role default).
pub fn set_groups(name: &str, groups: &[String]) -> std::io::Result<()> {
    let mut current = read();
    if groups.is_empty() {
        current.remove(name);
    } else {
        current.insert(name.to_owned(), groups.to_vec());
    }
    write(&current)
}

/// Drop the entry for an agent that is being destroyed. Idempotent.
pub fn remove_agent(name: &str) -> std::io::Result<()> {
    let mut current = read();
    if current.remove(name).is_some() {
        write(&current)?;
    }
    Ok(())
}