//! Optional matrix-tuwunel wiring: shared registration token (host) +
//! per-agent UIAA registration → `<agent-state>/matrix-token`. No-op
//! when the `hive-matrix` container isn't running, so operators who
//! haven't flipped `hyperhive.matrix.enable = true` pay nothing.
//!
//! See `docs/matrix.md::Provisioning flow (registration token)` for
//! the full UIAA round-trip, token-file shape, and host/container
//! bind-mount layout.

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

use anyhow::{Context, Result};
use reqwest::StatusCode;

use crate::coordinator::Coordinator;

/// nspawn container name for the matrix homeserver — mirrors
/// `hive-forge` and matches the bare-name allow-list the lifecycle
/// scanner skips over.
const MATRIX_CONTAINER: &str = "hive-matrix";
/// Local-host URL of the tuwunel client-server API. Shares the host
/// netns so `localhost:<port>` resolves both from the daemon and from
/// inside any sub-agent container.
const MATRIX_HTTP: &str = "http://localhost:8008";
/// Host path of the matrix registration token. Must match
/// `hyperhive.matrix.registrationTokenFile` in `nix/modules/hive-matrix.nix`
/// (same path is bind-mounted read-only into the tuwunel container so
/// the homeserver can read it via `registration_token_file`).
const REGISTER_TOKEN_PATH: &str = "/var/lib/hyperhive/matrix-register-token";
/// Length (bytes) of the random registration token. 32 raw bytes ⇒
/// 64-char hex string; comfortable for a long-lived shared secret.
const REGISTER_TOKEN_BYTES: usize = 32;
/// HTTP timeout for registration round-trips. UIAA is two POSTs; even
/// the slow path should finish well inside this budget.
const HTTP_TIMEOUT_SECS: u64 = 10;
/// Length (bytes) of the throwaway per-agent matrix password. Random
/// 32-byte hex — agents never log in with the password (they
/// authenticate by `access_token`), so it's protocol overhead. We
/// store it nowhere.
const PASSWORD_BYTES: usize = 32;

/// Matrix localpart for the hive system admin account. Registered
/// before any agent account in [`ensure_all`] so it becomes the first
/// user on the homeserver — Conduit/tuwunel grants admin rights to the
/// first registered user automatically. Not an agent; has no state dir.
pub const HIVE_ADMIN_LOCALPART: &str = "hive";

/// Host path for the hive admin matrix access token. Outside every
/// purgeable path — not deleted by `destroy --purge` on any agent.
#[must_use]
pub fn admin_token_path() -> PathBuf {
    PathBuf::from("/var/lib/hyperhive/matrix-admin-token")
}

/// Token file inside the agent's bind-mounted state dir (visible as
/// `/state/matrix-token` from inside the container).
fn token_path(name: &str) -> PathBuf {
    Coordinator::agent_notes_dir(name).join("matrix-token")
}

/// Password file for the agent's matrix account. Stored OUTSIDE the
/// purgeable `agent_state_root` tree so it survives `destroy --purge`
/// and allows re-login recovery when the same agent name is re-spawned.
///
/// Path: `/var/lib/hyperhive/matrix-creds/<name>-password`
///
/// The token file lives inside the agent's bind-mounted state dir (under
/// `agent_notes_dir`) so the agent container can read it; the password
/// file is host-side only (agents never log in by password — they use
/// the access token exclusively) and belongs with other hive-c0re
/// credential state, not inside the purgeable per-agent tree.
fn password_path(name: &str) -> PathBuf {
    PathBuf::from("/var/lib/hyperhive/matrix-creds").join(format!("{name}-password"))
}

/// Legacy password path (inside the old purgeable `agent_notes_dir`).
/// Used only during the one-time migration in [`ensure_user_for`] to
/// move credentials from old deployments to the new location. Safe to
/// call after `destroy --purge` — the path will simply not exist and
/// the migration is a no-op.
fn legacy_password_path(name: &str) -> PathBuf {
    Coordinator::agent_notes_dir(name).join("matrix-password")
}

/// Host path where the hive Matrix Space room ID is persisted.
/// Outside every purgeable path — not deleted by `destroy --purge`.
#[must_use]
pub fn hive_space_room_id_path() -> PathBuf {
    PathBuf::from("/var/lib/hyperhive/matrix-space-room-id")
}

/// Probe whether `hive-matrix` exists as a nixos-container. Cheap —
/// `nixos-container list` is just a directory scan in /etc. Same shape
/// as `forge::is_present` — routed through hive-priv since
/// `nixos-container` needs root and hive-c0re runs unprivileged.
pub async fn is_present() -> bool {
    let Ok(stdout) = crate::priv_client::list_containers().await else {
        return false;
    };
    stdout.lines().any(|l| l.trim() == MATRIX_CONTAINER)
}

/// Read `n` cryptographic-quality bytes from `/dev/urandom` and return
/// them hex-encoded. Avoids pulling a workspace `rand` dep just for
/// 32 bytes of randomness; the kernel's CSPRNG is more than enough for
/// a long-lived shared secret on the same host.
fn random_hex(n: usize) -> Result<String> {
    use std::io::Read;
    let mut buf = vec![0_u8; n];
    let mut f = std::fs::File::open("/dev/urandom").context("open /dev/urandom")?;
    f.read_exact(&mut buf).context("read /dev/urandom")?;
    let mut hex = String::with_capacity(n * 2);
    for b in &buf {
        use std::fmt::Write as _;
        write!(hex, "{b:02x}").ok();
    }
    Ok(hex)
}

/// Ensure the registration token file exists; returns its contents.
/// Generates a fresh 32-byte hex token on first call (mode 0600,
/// root-only), then re-reads on subsequent calls. The hive-matrix
/// nixos module bind-mounts this file read-only into the tuwunel
/// container so the homeserver can authenticate registration requests
/// against the same secret hive-c0re holds.
pub fn ensure_register_token() -> Result<String> {
    use std::os::unix::fs::PermissionsExt;
    let path = Path::new(REGISTER_TOKEN_PATH);
    if let Ok(existing) = std::fs::read_to_string(path) {
        let trimmed = existing.trim().to_owned();
        if !trimmed.is_empty() {
            return Ok(trimmed);
        }
    }
    let token = random_hex(REGISTER_TOKEN_BYTES)?;
    if let Some(parent) = path.parent() {
        std::fs::create_dir_all(parent).ok();
    }
    std::fs::write(path, format!("{token}\n"))
        .with_context(|| format!("write registration token to {}", path.display()))?;
    let _ = std::fs::set_permissions(path, std::fs::Permissions::from_mode(0o600));
    tracing::info!(path = %path.display(), "matrix: generated registration token");
    Ok(token)
}

/// Build the localpart of a matrix user id for `agent`. Matrix
/// usernames are 1-255 chars from the `[a-z0-9._=-/]` alphabet; agent
/// names already conform (hyperhive enforces a strict subset), so no
/// escaping is needed at the boundary.
fn user_localpart(agent: &str) -> &str {
    agent
}

/// Send a single registration POST and parse the response. Returns
/// `Ok((status, body))` on any successful HTTP round-trip (including
/// the expected 401 from the first UIAA leg); errors only on transport
/// failure. Body is the parsed JSON value — UIAA passes session +
/// flow state via JSON, never via headers.
async fn register_post(
    client: &reqwest::Client,
    body: &serde_json::Value,
) -> Result<(StatusCode, serde_json::Value)> {
    let url = format!("{MATRIX_HTTP}/_matrix/client/v3/register");
    let resp = client
        .post(&url)
        .json(body)
        .send()
        .await
        .context("matrix: POST /register")?;
    let status = resp.status();
    let json = resp
        .json::<serde_json::Value>()
        .await
        .context("matrix: parse /register response")?;
    Ok((status, json))
}

/// Generate a throwaway random password for matrix UIAA registration.
/// `PASSWORD_BYTES` raw bytes ⇒ 64-char hex string. Agents authenticate
/// by `access_token` so the password is protocol overhead we never
/// persist; the operator path in `hivectl` lets the caller supply a
/// real password instead so they can log into a matrix web client
/// (`m.login.password`).
pub fn random_password() -> Result<String> {
    random_hex(PASSWORD_BYTES)
}

/// Run the matrix-spec UIAA flow to register `agent` with the given
/// `password` and return the resulting access token. Two round-trips:
/// first POST elicits the 401 + session id, second POST supplies the
/// registration token in the `auth` block. If the homeserver returns
/// 200 on the first POST (no flow stages required — `allow_registration`
/// with no token), we take the access token directly.
///
/// Caller picks the password: agents use [`random_password`] (throwaway
/// — they auth by `access_token`), operators on the `hivectl` path
/// supply their own so they can log into matrix web clients.
async fn register_user(
    client: &reqwest::Client,
    agent: &str,
    register_token: &str,
    password: &str,
) -> Result<String> {
    let localpart = user_localpart(agent);
    let initial = serde_json::json!({
        "username": localpart,
        "password": password,
        // device_id stays stable across re-runs of ensure_user_for so
        // a re-mint doesn't strand orphan devices in tuwunel.
        "device_id": format!("hyperhive-{agent}"),
        "initial_device_display_name": format!("hyperhive ({agent})"),
        "inhibit_login": false,
    });
    let (status, body) = register_post(client, &initial).await?;
    // Some servers accept the first POST when allow_registration is
    // open. Take the access_token + we're done.
    if status.is_success() {
        return extract_access_token(&body);
    }
    if status != StatusCode::UNAUTHORIZED {
        anyhow::bail!("matrix: /register first leg HTTP {status}, body: {body}");
    }
    let session = body["session"]
        .as_str()
        .with_context(|| format!("matrix: missing UIAA session in 401, body: {body}"))?;
    let authed = serde_json::json!({
        "username": localpart,
        "password": password,
        "device_id": format!("hyperhive-{agent}"),
        "initial_device_display_name": format!("hyperhive ({agent})"),
        "inhibit_login": false,
        "auth": {
            "type": "m.login.registration_token",
            "token": register_token,
            "session": session,
        },
    });
    let (status, body) = register_post(client, &authed).await?;
    if !status.is_success() {
        anyhow::bail!("matrix: /register auth leg HTTP {status}, body: {body}");
    }
    extract_access_token(&body)
}

/// Pull `access_token` out of a successful /register response.
fn extract_access_token(body: &serde_json::Value) -> Result<String> {
    body["access_token"]
        .as_str()
        .map(str::to_owned)
        .with_context(|| format!("matrix: missing access_token in response: {body}"))
}

/// Login with `m.login.password` and return the access token. Fallback
/// for when registration fails with `M_USER_IN_USE` — the account
/// already exists in the homeserver but the token file was lost. Fails
/// if the stored password no longer matches (e.g. homeserver wiped),
/// in which case manual recovery via `hivectl matrix create-user` is
/// required.
async fn login_user(client: &reqwest::Client, agent: &str, password: &str) -> Result<String> {
    let url = format!("{MATRIX_HTTP}/_matrix/client/v3/login");
    let body = serde_json::json!({
        "type": "m.login.password",
        "identifier": {
            "type": "m.id.user",
            "user": user_localpart(agent),
        },
        "password": password,
        "device_id": format!("hyperhive-{agent}"),
        "initial_device_display_name": format!("hyperhive ({agent})"),
    });
    let resp = client
        .post(&url)
        .json(&body)
        .send()
        .await
        .context("matrix: POST /login")?;
    let status = resp.status();
    let json = resp
        .json::<serde_json::Value>()
        .await
        .context("matrix: parse /login response")?;
    if !status.is_success() {
        anyhow::bail!("matrix: /login HTTP {status} for agent {agent}, body: {json}");
    }
    extract_access_token(&json)
}

/// Auto-recovery helper: reset a user's matrix password via the admin API
/// when the locally stored password is missing. Requires a valid hive admin
/// token at [`admin_token_path()`]. Returns the new password (already
/// persisted to [`password_path(name)`]) on success.
///
/// Called by [`ensure_user_for`] when registration returns `M_USER_IN_USE`
/// but the password file is absent — covers the case where agent state dirs
/// were wiped but the homeserver still has the accounts.
async fn auto_reset_password(client: &reqwest::Client, name: &str) -> anyhow::Result<String> {
    let admin_token = read_admin_token()
        .context("matrix: admin token unavailable for auto-recovery; provision hive admin first")?;
    let server_name = discover_server_name(client)
        .await
        .context("matrix: discover_server_name for auto-recovery")?;
    let effective_password =
        reset_user_password(client, &admin_token, name, &server_name)
            .await
            .with_context(|| {
                format!("matrix: admin-room password reset for {name} (auto-recovery)")
            })?;
    tracing::info!(%name, "matrix: auto-recovered password via admin-room reset");
    Ok(effective_password)
}

// ---------------------------------------------------------------------------
// Admin-room fallback for password reset
// ---------------------------------------------------------------------------

/// Percent-encode a matrix room ID for use in a URL path segment.
/// Only `:` needs encoding; `!` and alphanumerics are path-safe.
fn encode_room_id_for_url(room_id: &str) -> String {
    room_id.replace(':', "%3A")
}

/// Look up the room ID for the `#admins:<server>` alias.
async fn discover_admin_room_id(
    client: &reqwest::Client,
    admin_token: &str,
    server_name: &str,
) -> Result<String> {
    // #admins:server → %23admins%3A<server>
    let encoded_alias = format!("%23admins%3A{server_name}");
    let url = format!("{MATRIX_HTTP}/_matrix/client/v3/directory/room/{encoded_alias}");
    let resp = client
        .get(&url)
        .bearer_auth(admin_token)
        .send()
        .await
        .context("matrix: GET admin room alias")?;
    let status = resp.status();
    let json = resp
        .json::<serde_json::Value>()
        .await
        .context("matrix: parse admin room alias response")?;
    if !status.is_success() {
        anyhow::bail!("matrix: admin room alias lookup failed: HTTP {status}, body: {json}");
    }
    json["room_id"]
        .as_str()
        .map(|s| s.to_owned())
        .ok_or_else(|| {
            anyhow::anyhow!("matrix: admin room alias response missing room_id: {json}")
        })
}

/// Try to parse the new password from an admin-room bot response.
/// Conduwuit/tuwunel responds with a message like:
/// "Done: Password of user @user:server has been reset. The new password is: <password>"
///
/// Handles several format variants emitted by different tuwunel / conduwuit
/// versions — "new password is:", "password is:", "changed to:", etc.
///
/// Uses [`str::to_ascii_lowercase`] for case folding — unlike `to_lowercase`,
/// ASCII lowercasing is guaranteed to produce a same-byte-length string, so the
/// byte offset from `find` is always a valid index into the original `bot_message`
/// and we never slice at a non-char boundary.
fn extract_new_password(bot_message: &str) -> Option<String> {
    // ASCII lowercase: same byte length as the original, so positions from
    // `lower.find(marker)` are valid byte indices into `bot_message`.
    let lower = bot_message.to_ascii_lowercase();
    for marker in &[
        // Explicit "is:" variants (most common in conduwuit / tuwunel):
        "new password is: ",
        "new password is:",
        "password is: ",
        "password is:",
        // "changed to:" / "reset to:" / "set to:" variants:
        "changed to: ",
        "changed to:",
        "reset to: ",
        "reset to:",
        "set to: ",
        "set to:",
        // Generic "… to: <pw>" form. tuwunel's actual reset-password reply is
        // "Successfully reset password for @user:server to: <password>" — the
        // password follows " to: " but no recognised verb sits adjacent to it,
        // so the markers above miss it. Matrix user ids / server names can't
        // contain " to: ", so this only ever anchors on the prose delimiter.
        // Placed after the specific verb markers and before the bare
        // "password:" last resort.
        " to: ",
        // Bare "new password:" without "is":
        "new password: ",
        "new password:",
        // Bare "password:" as last resort (must come after more specific markers):
        "password: ",
        "password:",
    ] {
        if let Some(pos) = lower.find(marker) {
            let rest = &bot_message[pos + marker.len()..];
            // Strip leading whitespace, then a leading code-span backtick:
            // tuwunel renders the password as a code span, so the plain
            // `body` carries literal backticks ("… to: `<pw>`").
            let rest = rest.trim_start().trim_start_matches('`');
            // The password ends at the first whitespace OR the closing
            // backtick. Generated passwords contain neither, so this never
            // truncates a real password mid-token.
            let end = rest
                .find(|c: char| c.is_whitespace() || c == '`')
                .unwrap_or(rest.len());
            let pw = rest[..end].trim();
            if !pw.is_empty() {
                return Some(pw.to_owned());
            }
        }
    }
    None
}

#[cfg(test)]
mod extract_new_password_tests {
    use super::extract_new_password;

    #[test]
    fn tuwunel_style_response() {
        let msg = "Done: Password of user @atlas:pr1ma.darkest.space has been reset. The new password is: abc123XYZ!";
        assert_eq!(extract_new_password(msg).as_deref(), Some("abc123XYZ!"));
    }

    #[test]
    fn case_insensitive_marker() {
        let msg = "Password reset complete. New Password Is: S3cr3tP@ss";
        assert_eq!(extract_new_password(msg).as_deref(), Some("S3cr3tP@ss"));
    }

    #[test]
    fn marker_without_trailing_space() {
        let msg = "new password is:hunter2";
        assert_eq!(extract_new_password(msg).as_deref(), Some("hunter2"));
    }

    #[test]
    fn shorter_marker_variant() {
        let msg = "Your password is: Tr0ub4dor&3";
        assert_eq!(extract_new_password(msg).as_deref(), Some("Tr0ub4dor&3"));
    }

    #[test]
    fn no_match_returns_none() {
        let msg = "Command not recognised. Please try again.";
        assert_eq!(extract_new_password(msg), None);
    }

    #[test]
    fn empty_after_marker_returns_none() {
        let msg = "new password is: ";
        assert_eq!(extract_new_password(msg), None);
    }

    #[test]
    fn password_stops_at_whitespace() {
        let msg = "New password is: abc123 (save it now)";
        assert_eq!(extract_new_password(msg).as_deref(), Some("abc123"));
    }

    #[test]
    fn changed_to_variant() {
        let msg = "Password of user @atlas:pr1ma.darkest.space has been changed to: Xyz987!";
        assert_eq!(extract_new_password(msg).as_deref(), Some("Xyz987!"));
    }

    #[test]
    fn reset_to_variant() {
        let msg = "Password for user @foo:bar has been reset to: hunter2";
        assert_eq!(extract_new_password(msg).as_deref(), Some("hunter2"));
    }

    #[test]
    fn tuwunel_reset_password_for_to_variant() {
        // The actual tuwunel admin-room reply observed in production — the
        // verb ("reset") is not adjacent to "to:", so only the generic
        // " to: " marker catches it.
        let msg = "Successfully reset password for @atlas:pr1ma.darkest.space to: N3wP@ssw0rd";
        assert_eq!(extract_new_password(msg).as_deref(), Some("N3wP@ssw0rd"));
    }

    #[test]
    fn to_marker_not_confused_by_user_id() {
        // The user id contains no " to: " so the marker only fires on the
        // real delimiter; the password is the token right after it.
        let msg = "Successfully reset password for @sock:pr1ma.darkest.space to: abc123XYZ";
        assert_eq!(extract_new_password(msg).as_deref(), Some("abc123XYZ"));
    }

    #[test]
    fn backtick_wrapped_password() {
        // tuwunel renders the password as a code span; the plain body
        // carries literal backticks. Strip them, don't capture them.
        let msg = "Successfully reset password for @atlas:pr1ma.darkest.space to: `N3wP@ssw0rd`";
        assert_eq!(extract_new_password(msg).as_deref(), Some("N3wP@ssw0rd"));
    }

    #[test]
    fn backtick_wrapped_with_trailing_text() {
        let msg = "Done. New password is: `hunter2` (store it now)";
        assert_eq!(extract_new_password(msg).as_deref(), Some("hunter2"));
    }

    #[test]
    fn bare_new_password_colon() {
        let msg = "New password: P@ssword1";
        assert_eq!(extract_new_password(msg).as_deref(), Some("P@ssword1"));
    }

    #[test]
    fn bare_password_colon_last_resort() {
        let msg = "Your account password: S3cr3t";
        assert_eq!(extract_new_password(msg).as_deref(), Some("S3cr3t"));
    }
}

/// Send a command to the Matrix admin room and poll for a bot response.
///
/// Strategy: send the command, capture its `event_id`, then poll backwards
/// (`dir=b&limit=20`) on each tick. Events in a backward response are
/// newest-first; we walk the list until we find our own command event_id,
/// then stop — everything before that marker in the list is a response that
/// arrived *after* our command. We check `body` and `formatted_body` of
/// every non-self message in that window.
///
/// This avoids forward-pagination token direction issues that occur with
/// some tuwunel builds: backward fetches are always anchored at the live
/// timeline end and need no stored token.
///
/// Generic over `T` so both password-returning and `()` callers share the loop.
async fn admin_room_send_and_poll<T>(
    client: &reqwest::Client,
    admin_token: &str,
    server_name: &str,
    room_url: &str,
    command: &str,
    check: impl Fn(&str) -> Option<T>,
) -> Result<T> {
    // Send the command; record the event_id so we can use it as an anchor.
    let txn_id = random_hex(8)?;
    let send_url = format!(
        "{MATRIX_HTTP}/_matrix/client/v3/rooms/{room_url}/send/m.room.message/{txn_id}"
    );
    let send_resp = client
        .put(&send_url)
        .bearer_auth(admin_token)
        .json(&serde_json::json!({"msgtype": "m.text", "body": command}))
        .send()
        .await
        .context("matrix: PUT admin room message")?;
    if !send_resp.status().is_success() {
        let body = send_resp.json::<serde_json::Value>().await.unwrap_or_default();
        anyhow::bail!("matrix: admin room send failed: {body}");
    }
    let send_json = send_resp
        .json::<serde_json::Value>()
        .await
        .unwrap_or_default();
    let our_event_id = send_json["event_id"]
        .as_str()
        .unwrap_or("")
        .to_owned();

    // Poll for bot response: fetch the 20 most recent events (newest-first)
    // on each tick. Walk the list until we hit our own command event_id;
    // everything *before* that marker arrived after our command.
    let own_user_id = format!("@{HIVE_ADMIN_LOCALPART}:{server_name}");
    let poll_url = format!(
        "{MATRIX_HTTP}/_matrix/client/v3/rooms/{room_url}/messages?dir=b&limit=20"
    );
    for _ in 0..15_u8 {
        tokio::time::sleep(std::time::Duration::from_secs(1)).await;
        let poll_json = client
            .get(&poll_url)
            .bearer_auth(admin_token)
            .send()
            .await
            .context("matrix: admin room poll")?
            .json::<serde_json::Value>()
            .await
            .context("matrix: parse admin room poll response")?;

        if let Some(events) = poll_json["chunk"].as_array() {
            for event in events {
                // Stop as soon as we reach our own command — everything
                // older (further into the list) predates our request.
                // If our_event_id is empty (malformed PUT response), we skip
                // this guard and inspect all 20 events — slight risk of a
                // false match from an older response, but an acceptable fallback.
                if !our_event_id.is_empty()
                    && event["event_id"].as_str() == Some(our_event_id.as_str())
                {
                    break;
                }
                if event["type"].as_str() != Some("m.room.message") {
                    continue;
                }
                if event["sender"].as_str() == Some(own_user_id.as_str()) {
                    continue;
                }
                // Check both plain body and formatted_body (HTML) — some
                // admin bots put the password only in formatted_body.
                let body = event["content"]["body"].as_str().unwrap_or_default();
                let formatted = event["content"]["formatted_body"]
                    .as_str()
                    .unwrap_or_default();
                for text in [body, formatted] {
                    if let Some(result) = check(text) {
                        return Ok(result);
                    }
                }
            }
        }
    }

    anyhow::bail!(
        "matrix: admin room command timed out after 15 seconds. \
         Command: '{command}'. No matching bot response received."
    )
}

/// Reset a user's password via the Matrix admin room (`#admins:<server>`).
/// Sends `!admin users reset-password @<localpart>:<server>` as @hive, polls for the bot's
/// response containing the new password.
///
/// Returns the new password; caller is responsible for persisting it.
async fn admin_room_reset_password(
    client: &reqwest::Client,
    admin_token: &str,
    server_name: &str,
    localpart: &str,
) -> Result<String> {
    let room_id = discover_admin_room_id(client, admin_token, server_name).await?;
    let room_url = encode_room_id_for_url(&room_id);
    let command = format!("!admin users reset-password @{localpart}:{server_name}");
    admin_room_send_and_poll(client, admin_token, server_name, &room_url, &command, extract_new_password)
        .await
        .with_context(|| {
            format!(
                "matrix: admin room reset-password for @{localpart}:{server_name}: \
                 no password response received within 15 seconds. \
                 Verify the admin room accepts '!admin users reset-password @user:server' commands."
            )
        })
}

/// Ensure `name` has a matrix user + token file on the local
/// homeserver. Skips provisioning entirely if the token file already
/// exists (treating a present token as proof the account is good).
/// To force re-provisioning, delete the token file.
///
/// When registration fails with `M_USER_IN_USE` (account exists in the
/// homeserver but the token file was deleted) this falls back to
/// `m.login.password` using the persisted `matrix-password` file. If
/// that file is also missing, recovery requires manual intervention:
/// `hivectl matrix create-user <name> --password <pw>`.
///
/// `client` is shared across the sweep so we build one reqwest
/// connection pool for all agents rather than one per call.
pub async fn ensure_user_for(
    client: &reqwest::Client,
    name: &str,
    register_token: &str,
) -> Result<()> {
    use std::os::unix::fs::PermissionsExt;
    let path = token_path(name);
    if path.exists()
        && let Ok(existing) = std::fs::read_to_string(&path)
        && !existing.trim().is_empty()
    {
        tracing::debug!(%name, "matrix: token already present");
        return Ok(());
    }

    // One-time migration: move the password from the old location inside
    // agent_notes_dir (purgeable) to the new location outside it.
    let new_pw_path = password_path(name);
    let old_pw_path = legacy_password_path(name);
    if !new_pw_path.exists() && old_pw_path.exists() {
        if let Some(parent) = new_pw_path.parent() {
            std::fs::create_dir_all(parent).ok();
        }
        if let Err(e) = std::fs::rename(&old_pw_path, &new_pw_path) {
            // Rename across filesystems or read-only src — copy + delete.
            if let Ok(content) = std::fs::read(&old_pw_path) {
                if std::fs::write(&new_pw_path, &content).is_ok() {
                    let _ = std::fs::remove_file(&old_pw_path);
                    tracing::info!(%name, "matrix: migrated password file to non-purgeable location");
                }
            } else {
                tracing::warn!(%name, rename_error = ?e, "matrix: password migration failed — could not read old path (old path stays)");
            }
        } else {
            tracing::info!(%name, "matrix: migrated password file to non-purgeable location");
        }
    }

    let password = random_password()?;
    let access_token = match register_user(client, name, register_token, &password).await {
        Ok(token) => {
            // Successful registration — persist the password so we can
            // fall back to login if the token file is deleted later.
            let pw_path = password_path(name);
            if let Some(parent) = pw_path.parent() {
                std::fs::create_dir_all(parent).ok();
            }
            if let Err(e) = std::fs::write(&pw_path, format!("{password}\n")) {
                tracing::warn!(%name, error = ?e, "matrix: failed to persist password (token still saved)");
            } else {
                let _ = std::fs::set_permissions(&pw_path, std::fs::Permissions::from_mode(0o600));
            }
            token
        }
        Err(reg_err) if reg_err.to_string().contains("M_USER_IN_USE") => {
            // Account already exists — try to re-login with the stored password.
            tracing::info!(%name, "matrix: user already exists, attempting login with stored password");
            let pw_path = password_path(name);
            let stored = match std::fs::read_to_string(&pw_path)
                .ok()
                .map(|s| s.trim().to_owned())
                .filter(|s| !s.is_empty())
            {
                Some(pw) => pw,
                None => {
                    // Password file missing — attempt auto-recovery via admin API.
                    // This covers the case where agent state dirs were wiped but the
                    // homeserver still has the accounts. Requires the hive admin
                    // token at /var/lib/hyperhive/matrix-admin-token.
                    tracing::info!(
                        %name,
                        "matrix: stored password missing, attempting admin-API auto-recovery"
                    );
                    match auto_reset_password(client, name).await {
                        Ok(new_pw) => new_pw,
                        Err(e) => {
                            anyhow::bail!(
                                "matrix: user {name} already exists but password is missing \
                                 and admin auto-recovery failed ({e:#}) — run:\n\
                                 hivectl matrix reset-password {name}\n\
                                 hivectl matrix create-user {name}"
                            )
                        }
                    }
                }
            };
            login_user(client, name, &stored).await.with_context(|| {
                format!(
                    "matrix: login fallback for {name} failed — if homeserver was wiped, delete \
                     the matrix-password file and retry"
                )
            })?
        }
        Err(other) => return Err(other),
    };

    // Write the token via hive-priv (root helper): hive-c0re runs as the
    // unprivileged `hive-core` user and cannot write to agent-owned state
    // directories directly. hive-priv writes the file 0600 and chowns it
    // to the agent user so it is readable from inside the container.
    crate::priv_client::write_agent_matrix_token(name, &access_token)
        .await
        .with_context(|| format!("matrix: write matrix-token for {name} via hive-priv"))?;
    tracing::info!(%name, "matrix: provisioned access token");
    Ok(())
}

/// Register a matrix account for `name` with the supplied `password`
/// and return the freshly-minted access token. Unlike [`ensure_user_for`],
/// the token is **not** persisted to disk — the caller is responsible
/// for storing it. Used by `hivectl matrix create-user` for human
/// (non-agent) accounts so we don't create stray
/// `/var/lib/hyperhive/agents/<name>/` directories for users that
/// aren't agents. For operator accounts the caller passes a real
/// password so the operator can `m.login.password` into matrix web
/// clients afterwards; for headless agent re-provisioning the caller
/// can pass [`random_password`] to keep the existing throwaway
/// behaviour.
///
/// **Not idempotent** (unlike [`forge::provision_user_token`]): the
/// matrix UIAA `/register` endpoint returns `M_USER_IN_USE` (HTTP 400)
/// on second call for the same localpart. Callers re-running this for
/// a known-existing matrix user should expect a hard error from this
/// fn and route to a password-reset path instead.
pub async fn provision_user_token(
    client: &reqwest::Client,
    name: &str,
    register_token: &str,
    password: &str,
) -> Result<String> {
    register_user(client, name, register_token, password).await
}

/// Per-agent matrix sync: ensure the agent has a matrix account + token.
/// All operations are idempotent; failures are logged as warnings but
/// don't abort the caller.
pub async fn sync_agent(client: &reqwest::Client, name: &str, register_token: &str) {
    if let Err(e) = ensure_user_for(client, name, register_token).await {
        tracing::warn!(%name, error = ?e, "matrix: ensure_user failed");
    }
}

/// Standalone per-agent sync that handles its own setup: checks if
/// hive-matrix is present, reads the registration token, and builds
/// an HTTP client before delegating to [`sync_agent`]. Mirrors the
/// setup in [`ensure_all`] so the rebuild path and the startup sweep
/// stay equivalent. No-op when the matrix container is absent.
pub async fn sync_agent_standalone(name: &str) {
    if !is_present().await {
        return;
    }
    let register_token = match ensure_register_token() {
        Ok(t) => t,
        Err(e) => {
            tracing::warn!(%name, error = ?e, "matrix: ensure_register_token failed");
            return;
        }
    };
    let client = match reqwest::Client::builder()
        .timeout(std::time::Duration::from_secs(HTTP_TIMEOUT_SECS))
        .build()
    {
        Ok(c) => c,
        Err(e) => {
            tracing::warn!(%name, error = ?e, "matrix: build HTTP client failed");
            return;
        }
    };
    sync_agent(&client, name, &register_token).await;
}

/// Ensure the hive system admin matrix user exists and its token is
/// persisted at [`admin_token_path()`]. Must be called BEFORE
/// [`ensure_all`]'s agent loop so this account is the first to register
/// and becomes the homeserver admin automatically (Conduit/tuwunel:
/// first registered user = admin).
///
/// Idempotent — skips when the token file already exists and is
/// non-empty. Does NOT promote the account via API (that requires
/// admin rights which this fn bootstraps); on a fresh homeserver the
/// first-registered rule fires automatically; on an existing homeserver
/// the operator must promote the account once via `hivectl matrix
/// `hivectl matrix promote-user hive` or the conduit admin room.
pub async fn ensure_admin_user(client: &reqwest::Client, register_token: &str) -> Result<()> {
    use std::os::unix::fs::PermissionsExt;
    let path = admin_token_path();
    if path.exists()
        && let Ok(existing) = std::fs::read_to_string(&path)
        && !existing.trim().is_empty()
    {
        tracing::debug!("matrix: hive admin token already present");
        return Ok(());
    }
    let password = random_password()?;
    let access_token = match register_user(client, HIVE_ADMIN_LOCALPART, register_token, &password)
        .await
    {
        Ok(token) => {
            let pw_path = password_path(HIVE_ADMIN_LOCALPART);
            if let Some(parent) = pw_path.parent() {
                std::fs::create_dir_all(parent).ok();
            }
            if let Err(e) = std::fs::write(&pw_path, format!("{password}\n")) {
                tracing::warn!(error = ?e, "matrix: failed to persist hive admin password");
            } else {
                let _ = std::fs::set_permissions(&pw_path, std::fs::Permissions::from_mode(0o600));
            }
            token
        }
        Err(reg_err) if reg_err.to_string().contains("M_USER_IN_USE") => {
            tracing::info!("matrix: hive admin user already exists, re-logging in");
            let pw_path = password_path(HIVE_ADMIN_LOCALPART);
            let stored = std::fs::read_to_string(&pw_path)
                .ok()
                .map(|s| s.trim().to_owned())
                .filter(|s| !s.is_empty())
                .with_context(|| {
                    format!(
                        "matrix: hive admin user exists but password missing at {} — \
                         manual recovery: reset password via admin API or conduit admin room",
                        pw_path.display()
                    )
                })?;
            login_user(client, HIVE_ADMIN_LOCALPART, &stored).await?
        }
        Err(other) => return Err(other),
    };
    if let Some(parent) = path.parent() {
        std::fs::create_dir_all(parent).ok();
    }
    std::fs::write(&path, format!("{access_token}\n"))
        .with_context(|| format!("matrix: write hive admin token to {}", path.display()))?;
    let _ = std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o600));
    tracing::info!(path = %path.display(), "matrix: provisioned hive admin token");
    Ok(())
}

/// Promote a user to homeserver admin via the Matrix admin room
/// (`#admins:<server>`). Sends `!admin users make-user-admin @<localpart>:<server>` as
/// @hive, polls for the bot's "Done:" success response.
///
/// tuwunel 1.6.x does not implement `/_synapse/admin/v2/users`; all admin
/// operations go through the admin room.
pub async fn promote_user_to_admin(
    client: &reqwest::Client,
    admin_token: &str,
    localpart: &str,
    server_name: &str,
) -> Result<()> {
    let room_id = discover_admin_room_id(client, admin_token, server_name).await?;
    let room_url = encode_room_id_for_url(&room_id);
    let command = format!("!admin users make-user-admin @{localpart}:{server_name}");
    admin_room_send_and_poll(client, admin_token, server_name, &room_url, &command, |body| {
        let lower = body.to_ascii_lowercase();
        if lower.starts_with("done") || lower.contains("made") && lower.contains("admin") {
            Some(())
        } else {
            None
        }
    })
    .await
    .with_context(|| {
        format!(
            "matrix: admin room make-user-admin for @{localpart}:{server_name}: \
             no success response within 15 seconds. \
             Verify the admin room accepts '!admin users make-user-admin @user:server' commands."
        )
    })
}

/// Reset a user's password via the Matrix admin room (`#admins:<server>`).
///
/// Sends `!admin users reset-password @<localpart>:<server>` to the admin room as @hive,
/// polls for the bot's response containing the new password, and persists
/// it to the non-purgeable creds path so [`ensure_user_for`] can re-login
/// on the next provisioning sweep.
///
/// Returns the new password for use in subsequent `login_user` calls.
pub async fn reset_user_password(
    client: &reqwest::Client,
    admin_token: &str,
    localpart: &str,
    server_name: &str,
) -> Result<String> {
    let pw = admin_room_reset_password(client, admin_token, server_name, localpart)
        .await
        .with_context(|| {
            format!("matrix: admin-room password reset for @{localpart}:{server_name}")
        })?;
    persist_password(localpart, &pw);
    Ok(pw)
}

/// Persist the matrix password for `localpart` to the non-purgeable creds path.
fn persist_password(localpart: &str, password: &str) {
    use std::os::unix::fs::PermissionsExt;
    let pw_path = password_path(localpart);
    if let Some(parent) = pw_path.parent() {
        std::fs::create_dir_all(parent).ok();
    }
    if let Err(e) = std::fs::write(&pw_path, format!("{password}\n")) {
        tracing::warn!(%localpart, error = ?e, "matrix: failed to persist reset password");
    } else {
        let _ = std::fs::set_permissions(&pw_path, std::fs::Permissions::from_mode(0o600));
    }
}

/// Discover the matrix `server_name` from the running homeserver via
/// `GET /_matrix/key/v2/server` (unauthenticated federation key endpoint).
/// The response JSON always includes `"server_name"` per the matrix spec.
pub async fn discover_server_name(client: &reqwest::Client) -> Result<String> {
    let url = format!("{MATRIX_HTTP}/_matrix/key/v2/server");
    let resp = client
        .get(&url)
        .send()
        .await
        .context("matrix: GET /_matrix/key/v2/server")?;
    let status = resp.status();
    let body = resp
        .json::<serde_json::Value>()
        .await
        .context("matrix: parse /_matrix/key/v2/server response")?;
    if !status.is_success() {
        anyhow::bail!("matrix: /_matrix/key/v2/server returned HTTP {status}, body: {body}");
    }
    body["server_name"]
        .as_str()
        .map(str::to_owned)
        .with_context(|| {
            format!("matrix: /_matrix/key/v2/server response missing server_name field: {body}")
        })
}

/// Read the hive admin access token from disk. Returns an error if it
/// is absent — callers should gate their admin-API calls on this.
pub fn read_admin_token() -> Result<String> {
    let path = admin_token_path();
    std::fs::read_to_string(&path)
        .ok()
        .map(|s| s.trim().to_owned())
        .filter(|s| !s.is_empty())
        .with_context(|| {
            format!(
                "hive admin matrix token not found at {} — \
                 ensure hive-c0re has started at least once with matrix enabled \
                 (it provisions the admin account on boot)",
                path.display()
            )
        })
}

/// Create the hive Matrix Space room using the admin account and persist
/// its room ID to [`hive_space_room_id_path()`]. Idempotent — returns
/// the stored room ID immediately if the file already exists.
///
/// The Space is a private `m.space` room owned by `@hive`. All agents
/// are invited after their accounts are provisioned in [`ensure_all`].
///
/// # Errors
///
/// Returns an error if the Matrix homeserver is unreachable, the
/// `createRoom` call fails, or the room-ID file cannot be written.
pub async fn ensure_hive_space(client: &reqwest::Client, admin_token: &str) -> Result<String> {
    use std::os::unix::fs::PermissionsExt;
    let path = hive_space_room_id_path();
    if let Ok(existing) = std::fs::read_to_string(&path) {
        let trimmed = existing.trim().to_owned();
        if !trimmed.is_empty() {
            tracing::debug!(room_id = %trimmed, "matrix: hive space already provisioned");
            return Ok(trimmed);
        }
    }
    let url = format!("{MATRIX_HTTP}/_matrix/client/v3/createRoom");
    let body = serde_json::json!({
        "name": "hive",
        "creation_content": { "type": "m.space" },
        "preset": "private_chat",
        "visibility": "private",
    });
    let resp = client
        .post(&url)
        .bearer_auth(admin_token)
        .json(&body)
        .send()
        .await
        .context("matrix: POST /createRoom (hive space)")?;
    let status = resp.status();
    let json = resp
        .json::<serde_json::Value>()
        .await
        .context("matrix: parse /createRoom response")?;
    if !status.is_success() {
        anyhow::bail!("matrix: createRoom HTTP {status}, body: {json}");
    }
    let room_id = json["room_id"]
        .as_str()
        .with_context(|| format!("matrix: createRoom missing room_id: {json}"))?
        .to_owned();
    if let Some(parent) = path.parent() {
        std::fs::create_dir_all(parent).ok();
    }
    std::fs::write(&path, format!("{room_id}\n"))
        .with_context(|| format!("matrix: write space room_id to {}", path.display()))?;
    let _ = std::fs::set_permissions(&path, std::fs::Permissions::from_mode(0o600));
    tracing::info!(%room_id, "matrix: created hive space");
    Ok(room_id)
}

/// Invite `@{localpart}:{server_name}` to `room_id` using the admin
/// account. Idempotent — treats already-member responses as success.
async fn invite_to_room(
    client: &reqwest::Client,
    admin_token: &str,
    room_id: &str,
    localpart: &str,
    server_name: &str,
) -> Result<()> {
    // `:` must be percent-encoded in the room-id path segment; `!` is
    // permitted in URL path characters per RFC 3986.
    let encoded_room_id = room_id.replace(':', "%3A");
    let url = format!("{MATRIX_HTTP}/_matrix/client/v3/rooms/{encoded_room_id}/invite");
    let user_id = format!("@{localpart}:{server_name}");
    let resp = client
        .post(&url)
        .bearer_auth(admin_token)
        .json(&serde_json::json!({ "user_id": user_id }))
        .send()
        .await
        .with_context(|| format!("matrix: POST /rooms/.../invite for {user_id}"))?;
    let status = resp.status();
    if status.is_success() {
        tracing::debug!(%user_id, %room_id, "matrix: invited to hive space");
        return Ok(());
    }
    // 403 with M_FORBIDDEN or M_BAD_STATE typically means the user is
    // already a member or has a pending invite — both are fine.
    if status == StatusCode::FORBIDDEN {
        let body = resp.json::<serde_json::Value>().await.unwrap_or_default();
        let errcode = body["errcode"].as_str().unwrap_or("");
        if errcode == "M_FORBIDDEN" || errcode == "M_BAD_STATE" {
            tracing::debug!(%user_id, %room_id, %errcode, "matrix: invite skipped (already member/invited)");
            return Ok(());
        }
        anyhow::bail!("matrix: invite {user_id} to {room_id}: HTTP {status}, body: {body}");
    }
    let body = resp.json::<serde_json::Value>().await.unwrap_or_default();
    anyhow::bail!("matrix: invite {user_id} to {room_id}: HTTP {status}, body: {body}")
}

/// Sweep every existing container (manager + sub-agents) and ensure
/// each has a matrix user + token on the local homeserver. Called once
/// at hive-c0re startup, alongside `forge::ensure_all`. No-op when the
/// hive-matrix container isn't running. Per-step failures are logged
/// but don't abort the sweep.
pub async fn ensure_all() {
    if !is_present().await {
        tracing::debug!("matrix: hive-matrix container absent, skipping user sweep");
        return;
    }
    let register_token = match ensure_register_token() {
        Ok(t) => t,
        Err(e) => {
            tracing::warn!(error = ?e, "matrix: ensure_register_token failed");
            return;
        }
    };
    // One HTTP client for the whole sweep — connection pool is
    // reused across agents.
    let client = match reqwest::Client::builder()
        .timeout(std::time::Duration::from_secs(HTTP_TIMEOUT_SECS))
        .build()
    {
        Ok(c) => c,
        Err(e) => {
            tracing::warn!(error = ?e, "matrix: build HTTP client failed; skipping sweep");
            return;
        }
    };
    // Provision hive admin user FIRST so it's the first registered
    // account on a fresh homeserver (Conduit/tuwunel makes the first
    // registered user admin automatically).
    if let Err(e) = ensure_admin_user(&client, &register_token).await {
        tracing::warn!(error = ?e, "matrix: ensure_admin_user failed");
    }
    let Ok(containers) = crate::lifecycle::list().await else {
        tracing::warn!("matrix: nixos-container list failed; skipping user sweep");
        return;
    };
    let mut agent_names: Vec<String> = Vec::new();
    for c in &containers {
        let Some(name) = c.strip_prefix(crate::lifecycle::AGENT_PREFIX) else {
            continue;
        };
        sync_agent(&client, name, &register_token).await;
        agent_names.push(name.to_owned());
    }

    // Provision the hive Space and invite all agents (+ the admin account).
    // server_name is needed to form full Matrix user IDs for invites.
    let admin_token = match read_admin_token() {
        Ok(t) => t,
        Err(e) => {
            tracing::warn!(error = ?e, "matrix: skipping hive space provisioning (no admin token)");
            return;
        }
    };
    let room_id = match ensure_hive_space(&client, &admin_token).await {
        Ok(id) => id,
        Err(e) => {
            tracing::warn!(error = ?e, "matrix: ensure_hive_space failed");
            return;
        }
    };
    let server_name = match discover_server_name(&client).await {
        Ok(s) => s,
        Err(e) => {
            tracing::warn!(error = ?e, "matrix: discover_server_name failed; skipping space invites");
            return;
        }
    };
    // Invite @hive admin first, then all agents.
    if let Err(e) = invite_to_room(
        &client,
        &admin_token,
        &room_id,
        HIVE_ADMIN_LOCALPART,
        &server_name,
    )
    .await
    {
        tracing::warn!(error = ?e, "matrix: invite @hive to space failed");
    }
    for name in &agent_names {
        if let Err(e) = invite_to_room(&client, &admin_token, &room_id, name, &server_name).await {
            tracing::warn!(%name, error = ?e, "matrix: invite agent to space failed");
        }
    }
}

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

    #[test]
    fn random_hex_is_well_formed_and_correct_length() {
        let h = random_hex(16).expect("/dev/urandom readable");
        assert_eq!(h.len(), 32);
        assert!(h.chars().all(|c| c.is_ascii_hexdigit()));
    }

    #[test]
    fn random_hex_two_calls_differ() {
        // Sanity check — not a statistical claim, just guards
        // against ever accidentally returning a constant.
        let a = random_hex(16).expect("/dev/urandom readable");
        let b = random_hex(16).expect("/dev/urandom readable");
        assert_ne!(a, b);
    }

    #[test]
    fn extract_access_token_pulls_from_success_body() {
        let body = serde_json::json!({
            "user_id": "@alice:matrix.example.org",
            "access_token": "syt_abc123",
            "device_id": "ABC",
        });
        assert_eq!(extract_access_token(&body).unwrap(), "syt_abc123");
    }

    #[test]
    fn extract_access_token_errors_on_missing_field() {
        let body = serde_json::json!({"user_id": "@alice:matrix.example.org"});
        let err = extract_access_token(&body).unwrap_err();
        assert!(err.to_string().contains("missing access_token"));
    }
}