//! Async client for the `hive-priv` privileged-helper socket.
//!
//! Exposes a standalone async function per operation. Each call opens a
//! fresh connection to `/run/hive/priv.sock`, sends one JSON line, reads
//! the response, and closes. Connection-per-call is intentional: priv
//! calls are infrequent (once per rebuild step), so simplicity wins over
//! a persistent connection.

use anyhow::{Context as _, Result, bail};
use hive_sh4re::priv_proto::{
    BindMount, CredentialMount, InfraAction, InfraContainer, JournalQuery, NetworkIsolation,
    PRIV_SOCK, PrivEvent, PrivRequest, PrivResponse, PrivStream,
};
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::UnixStream;

/// Send a single request to `hive-priv` and return the response.
/// For streaming ops use `call_streaming` instead.
pub async fn call(req: &PrivRequest) -> Result<PrivResponse> {
    let mut stream = UnixStream::connect(PRIV_SOCK)
        .await
        .context("connect to hive-priv socket")?;
    let line = serde_json::to_string(req).context("serialise PrivRequest")? + "\n";
    stream
        .write_all(line.as_bytes())
        .await
        .context("send request to hive-priv")?;
    stream.shutdown().await.context("shutdown write half")?;
    let mut resp_line = String::new();
    BufReader::new(stream)
        .read_line(&mut resp_line)
        .await
        .context("read response from hive-priv")?;
    // New hive-priv sends `PrivEvent::Done(PrivResponse)` (untagged, wire-
    // identical to bare `PrivResponse`) — deserialise as `PrivEvent` to
    // handle both the old bare format and the new tagged format.
    match serde_json::from_str::<PrivEvent>(&resp_line).context("parse PrivResponse")? {
        PrivEvent::Done(resp) => Ok(resp),
        PrivEvent::Line(_) => bail!("unexpected stream line from non-streaming priv op"),
    }
}

/// Send a streaming request to `hive-priv`, calling `on_line` for each
/// `PrivEvent::Line` as it arrives, then returning the terminal
/// `PrivResponse`. Used for long-running ops (`create` / `update`).
pub async fn call_streaming(
    req: &PrivRequest,
    mut on_line: impl FnMut(PrivStream, &str),
) -> Result<PrivResponse> {
    let mut stream = UnixStream::connect(PRIV_SOCK)
        .await
        .context("connect to hive-priv socket (streaming)")?;
    let line = serde_json::to_string(req).context("serialise PrivRequest")? + "\n";
    stream
        .write_all(line.as_bytes())
        .await
        .context("send request to hive-priv")?;
    stream.shutdown().await.context("shutdown write half")?;
    let mut reader = BufReader::new(stream);
    loop {
        let mut event_line = String::new();
        reader
            .read_line(&mut event_line)
            .await
            .context("read event from hive-priv")?;
        if event_line.is_empty() {
            bail!("hive-priv closed connection before sending Done event");
        }
        match serde_json::from_str::<PrivEvent>(&event_line).context("parse PrivEvent")? {
            PrivEvent::Line(l) => on_line(l.stream, &l.data),
            PrivEvent::Done(resp) => return Ok(resp),
        }
    }
}

pub async fn start_container(name: &str) -> Result<()> {
    ok(call(&PrivRequest::StartContainer {
        name: name.to_owned(),
    })
    .await?)
}

pub async fn stop_container(name: &str) -> Result<()> {
    ok(call(&PrivRequest::StopContainer {
        name: name.to_owned(),
    })
    .await?)
}

pub async fn kill_container(name: &str) -> Result<()> {
    ok(call(&PrivRequest::KillContainer {
        name: name.to_owned(),
    })
    .await?)
}

pub async fn update_container(name: &str) -> Result<(String, String)> {
    check(
        call(&PrivRequest::UpdateContainer {
            name: name.to_owned(),
            stream: false,
        })
        .await?,
    )
}

/// Streaming variant: forward stdout/stderr lines to `on_line` as they
/// arrive. Returns `Ok(())` on success; the callback is responsible for
/// appending lines to `build_logs` or otherwise capturing the output.
pub async fn update_container_streaming(
    name: &str,
    on_line: impl FnMut(PrivStream, &str),
) -> Result<()> {
    ok(call_streaming(
        &PrivRequest::UpdateContainer {
            name: name.to_owned(),
            stream: true,
        },
        on_line,
    )
    .await?)
}

pub async fn create_container(name: &str) -> Result<(String, String)> {
    check(
        call(&PrivRequest::CreateContainer {
            name: name.to_owned(),
            stream: false,
        })
        .await?,
    )
}

/// Streaming variant: forward stdout/stderr lines to `on_line` as they
/// arrive. Returns `Ok(())` on success.
pub async fn create_container_streaming(
    name: &str,
    on_line: impl FnMut(PrivStream, &str),
) -> Result<()> {
    ok(call_streaming(
        &PrivRequest::CreateContainer {
            name: name.to_owned(),
            stream: true,
        },
        on_line,
    )
    .await?)
}

pub async fn destroy_container(name: &str) -> Result<()> {
    ok(call(&PrivRequest::DestroyContainer {
        name: name.to_owned(),
    })
    .await?)
}

pub async fn list_containers() -> Result<String> {
    let (stdout, _) = check(call(&PrivRequest::ListContainers).await?)?;
    Ok(stdout)
}

/// Read a container's journal via the root helper (`journalctl -M`).
/// Returns `(stdout, stderr)`; a non-zero journalctl exit is reported in
/// `stderr` rather than as an `Err`, so callers can surface either.
pub async fn read_container_journal(
    container: &str,
    query: JournalQuery,
) -> Result<(String, String)> {
    check(
        call(&PrivRequest::ReadContainerJournal {
            container: container.to_owned(),
            query,
        })
        .await?,
    )
}

pub async fn write_nspawn_flags(
    container: &str,
    binds: &[BindMount],
    isolation: Option<NetworkIsolation>,
    load_credentials: &[CredentialMount],
) -> Result<()> {
    ok(call(&PrivRequest::WriteNspawnFlags {
        container: container.to_owned(),
        binds: binds.to_vec(),
        isolation,
        load_credentials: load_credentials.to_vec(),
    })
    .await?)
}

pub async fn write_resource_limits(
    container: &str,
    memory_max: &str,
    cpu_quota: &str,
) -> Result<()> {
    ok(call(&PrivRequest::WriteResourceLimits {
        container: container.to_owned(),
        memory_max: memory_max.to_owned(),
        cpu_quota: cpu_quota.to_owned(),
    })
    .await?)
}

pub async fn remove_service_dropin(container: &str) -> Result<()> {
    ok(call(&PrivRequest::RemoveServiceDropin {
        container: container.to_owned(),
    })
    .await?)
}

pub async fn daemon_reload() -> Result<()> {
    ok(call(&PrivRequest::DaemonReload).await?)
}

pub async fn reload_gateway_nginx() -> Result<()> {
    ok(call(&PrivRequest::ReloadGatewayNginx).await?)
}

pub async fn chown_socket_dir(agent_name: &str, uid: u32, gid: u32) -> Result<()> {
    ok(call(&PrivRequest::ChownSocketDir {
        agent_name: agent_name.to_owned(),
        uid,
        gid,
    })
    .await?)
}

pub async fn chmod_socket_dir(agent_name: &str, mode: u32) -> Result<()> {
    ok(call(&PrivRequest::ChmodSocketDir {
        agent_name: agent_name.to_owned(),
        mode,
    })
    .await?)
}

/// Run `forgejo admin <args>` inside the `hive-forge` container via
/// hive-priv (which runs as root and can nsenter into the container).
/// Returns `(stdout, stderr)` on success.
pub async fn run_forge_admin(args: &[&str]) -> Result<(String, String)> {
    let owned: Vec<String> = args.iter().map(|s| (*s).to_owned()).collect();
    check(call(&PrivRequest::RunForgeAdmin { args: owned }).await?)
}

/// Write the Forgejo access token for `agent_name` to
/// `<agent_state_root>/<agent_name>/state/forge-token` via hive-priv
/// (running as root). The file is written 0600 and chowned to the agent
/// user so it is readable from inside the agent container.
pub async fn write_agent_forge_token(agent_name: &str, token: &str) -> Result<()> {
    ok(call(&PrivRequest::WriteAgentForgeToken {
        agent_name: agent_name.to_owned(),
        token: token.to_owned(),
    })
    .await?)
}

/// Write a Matrix access token for `agent_name` via hive-priv (running as
/// root). `account: None` writes the hive-internal
/// `<state>/matrix-token`; `account: Some(name)` writes
/// `<state>/matrix-token-<name>` for an extra (external) account. The file
/// is written 0600 and chowned to the agent user so it is readable from
/// inside the agent container. hive-priv validates the account suffix.
///
/// `homeserver: Some(url)` (only meaningful with `account: Some`) also
/// writes the sidecar `<state>/matrix-account-<name>.json` so the daemon
/// can auto-discover the extra account without a `matrixAccounts` config
/// declaration (see issue tracker "external matrix account auto-discovery").
pub async fn write_agent_matrix_token(
    agent_name: &str,
    token: &str,
    account: Option<&str>,
    homeserver: Option<&str>,
) -> Result<()> {
    ok(call(&PrivRequest::WriteAgentMatrixToken {
        agent_name: agent_name.to_owned(),
        token: token.to_owned(),
        account: account.map(ToOwned::to_owned),
        homeserver: homeserver.map(ToOwned::to_owned),
    })
    .await?)
}

/// Restart `hive-matrix-daemon.service` inside an agent container via
/// `systemctl --machine=h-<agent_name> restart hive-matrix-daemon.service`.
/// Non-fatal: callers should handle errors gracefully — if the container is
/// not running the restart will fail (the unit starts naturally on next boot).
pub async fn restart_matrix_daemon(agent_name: &str) -> Result<()> {
    ok(call(&PrivRequest::RestartMatrixDaemon {
        agent_name: agent_name.to_owned(),
    })
    .await?)
}

/// Restart a hive infrastructure container on the host (thin wrapper over
/// [`control_infra_container`] with `action = Restart`). hive-priv
/// re-validates `container` against its root-side allowlist; callers must
/// already have checked the requesting agent holds the `infra_admin`
/// capability.
pub async fn restart_infra_container(container: InfraContainer) -> Result<()> {
    control_infra_container(container, InfraAction::Restart).await
}

/// Start / stop / restart a hive infrastructure container (`hive-ci`,
/// `hive-gateway`, `hive-forge`, `hive-matrix`) on the host via `systemctl
/// <action> container@<container>.service`. The [`InfraContainer`] enum is
/// the allowlist — hive-priv needs no name re-validation. Used by the
/// hive-wide `hivectl stop` / `hivectl start` flow.
pub async fn control_infra_container(container: InfraContainer, action: InfraAction) -> Result<()> {
    ok(call(&PrivRequest::ControlInfraContainer { container, action }).await?)
}

/// Ensure the agent's persistent state root is a btrfs subvolume when the
/// host FS supports it (via hive-priv, which runs as root). Idempotent and
/// progressive: a no-op when the root already exists or the FS isn't btrfs.
/// Safe to call on every provision.
pub async fn ensure_agent_subvolume(agent_name: &str) -> Result<()> {
    ok(call(&PrivRequest::EnsureAgentSubvolume {
        agent_name: agent_name.to_owned(),
    })
    .await?)
}

/// Delete the agent's state root iff it is a btrfs subvolume (purge path
/// only). No-op for plain dirs / missing paths — hive-c0re's own
/// `remove_dir_all` handles those.
pub async fn delete_agent_subvolume(agent_name: &str) -> Result<()> {
    ok(call(&PrivRequest::DeleteAgentSubvolume {
        agent_name: agent_name.to_owned(),
    })
    .await?)
}

/// Enable btrfs qgroup accounting on the agent-state filesystem (operator
/// opt-in; prerequisite for usage reads + quotas). Idempotent; no-op off
/// btrfs. Via hive-priv (root).
///
/// # Errors
/// Returns an error if the hive-priv call fails or `btrfs quota enable`
/// reports a non-zero exit.
pub async fn ensure_btrfs_quota() -> Result<()> {
    ok(call(&PrivRequest::EnsureBtrfsQuota).await?)
}

/// Read an agent state subvolume's btrfs qgroup usage, returning
/// `(referenced_bytes, exclusive_bytes)`. Via hive-priv (root).
///
/// # Errors
/// Returns an error if the hive-priv call fails, `btrfs qgroup show` exits
/// non-zero (e.g. quota not enabled — the message propagates so the caller
/// can surface it), or the output has no level-0 qgroup row to parse.
pub async fn read_subvolume_usage(agent_name: &str) -> Result<(u64, u64)> {
    let (stdout, _) = check(
        call(&PrivRequest::ReadSubvolumeUsage {
            agent_name: agent_name.to_owned(),
        })
        .await?,
    )?;
    parse_qgroup_usage(&stdout).with_context(|| format!("parse qgroup usage for {agent_name}"))
}

/// Set or clear a btrfs qgroup size limit on an agent's state subvolume.
/// `limit_bytes = None` clears it. Requires quota enabled. Via hive-priv.
///
/// # Errors
/// Returns an error if the hive-priv call fails or `btrfs qgroup limit`
/// reports a non-zero exit (e.g. quota not enabled).
pub async fn set_subvolume_quota(agent_name: &str, limit_bytes: Option<u64>) -> Result<()> {
    ok(call(&PrivRequest::SetSubvolumeQuota {
        agent_name: agent_name.to_owned(),
        limit_bytes,
    })
    .await?)
}

/// Convert an existing plain-dir agent state root into a btrfs subvolume in
/// place (operator opt-in; via hive-priv as root). The caller must stop the
/// agent first (so its state bind-mount is gone) and restart it after.
/// Idempotent: a no-op when the root is already a subvolume.
///
/// # Errors
/// Returns an error if the hive-priv call fails, the state dir is missing,
/// the FS isn't btrfs, or the migration (subvolume create / copy / swap)
/// fails — in which case the original dir is left untouched.
pub async fn upgrade_agent_subvolume(agent_name: &str) -> Result<()> {
    ok(call(&PrivRequest::UpgradeAgentSubvolume {
        agent_name: agent_name.to_owned(),
    })
    .await?)
}

/// Parse `(referenced, exclusive)` bytes from `btrfs qgroup show -f --raw`
/// output (a qgroup row is `<id-with-slash> <rfer> <excl> …`).
///
/// `-f <path>` already restricts the listing to qgroups impacting that path
/// (excluding ancestral qgroups — see btrfs-qgroup-show(8)), so it never
/// mixes in other agents' subvolumes. Among the rows it returns we select
/// the **level-0** qgroup (`0/<subvolid>`) — the subvolume's own automatic
/// usage qgroup — rather than blindly taking the last line. Picking the
/// `0/` leaf is unambiguous even if an operator has assigned the subvolume
/// to a higher-level aggregate qgroup (`1/<id>`, …) that `-F` would surface.
fn parse_qgroup_usage(out: &str) -> Result<(u64, u64)> {
    for line in out.lines() {
        let cols: Vec<&str> = line.split_whitespace().collect();
        if cols.len() >= 3
            && cols[0].starts_with("0/")
            && let (Ok(rfer), Ok(excl)) = (cols[1].parse::<u64>(), cols[2].parse::<u64>())
        {
            return Ok((rfer, excl));
        }
    }
    bail!("no level-0 qgroup data row in `btrfs qgroup show` output: {out:?}")
}

fn check(resp: PrivResponse) -> Result<(String, String)> {
    if resp.ok {
        Ok((resp.stdout, resp.stderr))
    } else {
        bail!(
            "{}",
            resp.error.as_deref().unwrap_or("hive-priv returned error")
        )
    }
}

fn ok(resp: PrivResponse) -> Result<()> {
    check(resp)?;
    Ok(())
}