//! Per-agent capability configuration. Stored at
//! `/var/lib/hyperhive/meta/capabilities.json` alongside `topology.json`
//! and `tool-groups.json`.
//!
//! Format: a JSON object mapping agent name to an array of
//! `hive_sh4re::Capability` `snake_case` strings:
//!
//! ```json
//! {
//!   "atlas": ["read_host_journal"],
//!   "ruth":  ["query_agent_state"]
//! }
//! ```
//!
//! An absent entry (or an absent file) means "no extra capabilities".
//! `render_flake` in `meta.rs` reads this file and injects
//! `HIVE_CAPABILITIES` into each agent's systemd service env; absent
//! entries emit no env var so agents without capabilities don't trigger
//! a spurious rebuild.
//!
//! Write path: `set_caps` is called from the dashboard action handler
//! that the operator uses to grant/revoke capabilities per agent.

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

const CAPABILITIES_FILE: &str = "capabilities.json";

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

/// Read the per-agent capability map. Returns an empty map when the
/// file is absent or unparsable — callers treat a missing entry as
/// "no extra capabilities".
#[must_use]
pub fn read() -> BTreeMap<String, Vec<String>> {
    let path = capabilities_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 capabilities for one agent. Returns an empty
/// vec when the agent has no entry.
#[must_use]
pub fn caps_for(name: &str) -> Vec<String> {
    read().get(name).cloned().unwrap_or_default()
}

/// Check whether an agent holds a specific capability.
#[must_use]
pub fn has_cap(name: &str, cap: hive_sh4re::Capability) -> bool {
    caps_for(name)
        .iter()
        .any(|s| s.eq_ignore_ascii_case(cap.as_str()))
}

/// Persist the full capability 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 = capabilities_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 capabilities for one agent and persist the map. An empty
/// `caps` vec removes the entry (agent has no capabilities).
pub fn set_caps(name: &str, caps: &[String]) -> std::io::Result<()> {
    let mut current = read();
    if caps.is_empty() {
        current.remove(name);
    } else {
        current.insert(name.to_owned(), caps.to_vec());
    }
    write(&current)
}

/// Remove an agent from the capability map entirely. Called by
/// `meta::sync_agents` when an agent is deprovisioned so stale entries
/// don't accumulate. No-op if the agent has no entry.
pub fn remove_agent(name: &str) -> std::io::Result<()> {
    let mut current = read();
    if current.remove(name).is_some() {
        write(&current)?;
    }
    Ok(())
}