//! 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::permissions::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 default"
//! (`AGENT_DEFAULT`: `messaging + meta + inbox + execution`). `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 to `AGENT_DEFAULT`.
//!
//! Write path: `set_groups` is called from the dashboard action handler
//! that the operator uses to grant/revoke tool groups per agent.

use std::collections::BTreeMap;
use std::path::{Path, PathBuf};

use anyhow::Context as _;

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

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

/// Read the per-agent tool-group map. An absent file is the empty map —
/// callers treat a missing entry as "use role default". A file that
/// exists but can't be read or parsed is an error.
pub fn read() -> std::io::Result<BTreeMap<String, Vec<String>>> {
    super::read_map(&tool_groups_path())
}

/// 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." Errors as [`read`] does.
pub fn groups_for(name: &str) -> std::io::Result<Vec<String>> {
    Ok(read()?.get(name).cloned().unwrap_or_default())
}

/// Validate a slice of group name strings against `ToolGroup::ALL`.
/// Returns `Ok(())` when all names are known, or `Err` listing the
/// unrecognised names so callers can surface a useful error message.
pub fn validate_groups(groups: &[String]) -> anyhow::Result<()> {
    let valid: std::collections::BTreeSet<&str> = hive_sh4re::permissions::ToolGroup::ALL
        .iter()
        .map(|g| <&str>::from(*g))
        .collect();
    let unknown: Vec<&str> = groups
        .iter()
        .map(String::as_str)
        .filter(|s| !valid.contains(s))
        .collect();
    if unknown.is_empty() {
        Ok(())
    } else {
        anyhow::bail!(
            "unknown tool group(s): {}; valid names are: {}",
            unknown.join(", "),
            hive_sh4re::permissions::ToolGroup::ALL
                .iter()
                .map(|g| <&str>::from(*g))
                .collect::<Vec<_>>()
                .join(", ")
        )
    }
}

/// Set the tool groups for one agent and persist the map. An empty
/// `groups` vec removes the entry (agent reverts to role default).
/// Returns an error if any name is not in `ToolGroup::ALL`, or if the
/// existing file can't be read or parsed — the file is then left
/// untouched.
pub fn set_groups(name: &str, groups: &[String]) -> anyhow::Result<()> {
    set_groups_at(&tool_groups_path(), name, groups)
}

fn set_groups_at(path: &Path, name: &str, groups: &[String]) -> anyhow::Result<()> {
    if !groups.is_empty() {
        validate_groups(groups)?;
    }
    let mut current: BTreeMap<String, Vec<String>> = super::read_map(path)?;
    if groups.is_empty() {
        current.remove(name);
    } else {
        current.insert(name.to_owned(), groups.to_vec());
    }
    super::write_map(path, &current).with_context(|| format!("write tool-groups for {name}"))
}

/// Drop the entry for an agent that is being destroyed. Idempotent.
/// Fails without writing if the existing file can't be read or parsed.
pub fn remove_agent(name: &str) -> std::io::Result<()> {
    remove_agent_at(&tool_groups_path(), name)
}

fn remove_agent_at(path: &Path, name: &str) -> std::io::Result<()> {
    let mut current: BTreeMap<String, Vec<String>> = super::read_map(path)?;
    if current.remove(name).is_some() {
        super::write_map(path, &current)?;
    }
    Ok(())
}

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

    const TRUNCATED: &str = "{\n  \"alice\": [\"messaging\", \"meta\"],\n  \"bob\": [\"mess";

    fn corrupt_file() -> (tempfile::TempDir, PathBuf) {
        let dir = tempfile::tempdir().expect("tempdir");
        let path = dir.path().join(TOOL_GROUPS_FILE);
        std::fs::write(&path, TRUNCATED).expect("seed");
        (dir, path)
    }

    #[test]
    fn set_groups_leaves_a_corrupt_file_untouched() {
        let (_dir, path) = corrupt_file();
        let err = set_groups_at(&path, "ruth", &["messaging".to_owned()])
            .expect_err("a corrupt file must not be overwritten");
        let kind = err
            .downcast_ref::<std::io::Error>()
            .map(std::io::Error::kind);
        assert_eq!(kind, Some(std::io::ErrorKind::InvalidData));
        assert_eq!(std::fs::read(&path).expect("read"), TRUNCATED.as_bytes());
    }

    #[test]
    fn remove_agent_leaves_a_corrupt_file_untouched() {
        let (_dir, path) = corrupt_file();
        let err =
            remove_agent_at(&path, "alice").expect_err("a corrupt file must not be overwritten");
        assert_eq!(err.kind(), std::io::ErrorKind::InvalidData);
        assert_eq!(std::fs::read(&path).expect("read"), TRUNCATED.as_bytes());
    }

    #[test]
    fn set_groups_keeps_other_agents_entries() {
        let dir = tempfile::tempdir().expect("tempdir");
        let path = dir.path().join(TOOL_GROUPS_FILE);
        set_groups_at(&path, "alice", &["inbox".to_owned()]).expect("set on missing file");
        set_groups_at(&path, "ruth", &["messaging".to_owned()]).expect("set");
        let map: BTreeMap<String, Vec<String>> =
            crate::agent_config::read_map(&path).expect("read");
        assert_eq!(map["alice"], vec!["inbox".to_owned()]);
        assert_eq!(map["ruth"], vec!["messaging".to_owned()]);
    }
}