//! Turns the printers' own camera URLs into a go2rtc configuration.
//!
//! `go2rtc.rs` has supervised a go2rtc process since before this module
//! existed, and go2rtc has never had anything to serve: nothing wrote its
//! config file. `CONTINUUM_GO2RTC_CONFIG` pointed at `./go2rtc.yaml`, which
//! did not exist in the repository or anywhere else. This writes it.
//!
//! ## Where the URL comes from
//!
//! Not from `printers.toml`. A printer reports its own camera URL in
//! `print.push_status`'s `ipcam` block, so asking an operator to copy it into
//! a config file would be asking them to keep a second copy of something the
//! machine already tells us - and to update it by hand when the printer's
//! address changes.
//!
//! ## What does not work, which is most printers
//!
//! Only the X1/H2 class publishes an `rtsp_url`. Confirmed against two real
//! machines: an H2C reports `rtsps://<ip>:322/streaming/live/1`, and a P1P
//! reports an `ipcam` block with no URL in it at all. A P1/A1 camera is
//! reachable only over Bambu's proprietary port-6000 JPEG stream, which this
//! crate does not speak, so those printers get no stream here and say so
//! rather than advertising one that will not play.
//!
//! That is not just an inference from the missing field - it is confirmed at
//! the network layer (2026-10-15). The H2C accepts TCP on 322; the P1P
//! *refuses* 322 and listens on 6000. So a P1P has no RTSP endpoint to
//! restream, and no amount of guessing a URL would produce one.
//!
//! That is also why this module reads the *reported* URL and never builds one
//! from the printer's IP: the fact that a printer has a camera and the fact
//! that the camera has an RTSP endpoint are different facts, and only the
//! second one is useful.
//!
//! ## What is confirmed to work
//!
//! Measured end to end against a live H2C with go2rtc 1.9.14 (2026-10-18):
//! this module's generated config is enough for go2rtc to connect to
//! `rtsps://bblp:<access_code>@<ip>:322/streaming/live/1` and pull video -
//! 984,604 bytes over `rtsp+tcp`, no certificate complaint and no
//! authentication failure. The printer runs LIVE555 and sends **H.264 High
//! profile, level 4.1**, which a browser plays natively over WebRTC, so no
//! transcoding step (and no ffmpeg on the gateway) is needed. The
//! `rtspx://` prefix that go2rtc documents for skipping TLS verification is
//! not required here.

use std::collections::BTreeMap;
use std::time::Duration;

use tokio::sync::Notify;
use tracing::{info, warn};

use crate::printer::{GenericPrinter, PrinterHandle};
use crate::uplink::SharedFleet;

/// How often to rebuild the configuration from what the printers report.
///
/// A camera URL changes when a printer's address changes, which is a DHCP
/// lease event, not something that needs watching closely. The first useful
/// rebuild is the one a few seconds after startup, once the first reports
/// have arrived - before that the fleet has nothing to say.
const REBUILD_INTERVAL: Duration = Duration::from_secs(30);

/// The username every Bambu uses for its own services - MQTT, FTPS, and the
/// camera. Not a guess: it is what `bambu_mqtt` and `bambu_ftps` already
/// authenticate with.
const CAMERA_USER: &str = "bblp";

/// One printer's playable stream.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct CameraSource {
    /// Our own printer id, which doubles as the go2rtc stream name. Using it
    /// for both means the cloud can name a stream without the gateway having
    /// to report a mapping: `camera_stream` in telemetry is this id.
    pub stream_name: String,
    /// The full source URL, credentials included.
    pub url: String,
}

/// Builds the source URL for one printer, or `None` if it has no stream.
///
/// The credentials go in the URL because that is the only place go2rtc takes
/// them for an RTSP source. The consequence is that the printer's access code
/// ends up in a file on disk - which is not a new exposure (`printers.toml`
/// already holds it, and that file is gitignored for this reason) but it does
/// mean the generated config deserves the same treatment, and must never be
/// logged.
pub fn source_for(printer: &PrinterHandle, report_url: Option<&str>) -> Option<CameraSource> {
    let PrinterHandle::Bambu(bambu) = printer else {
        // Nothing else has a camera path here yet. A Prusa's is a separate
        // product, and a Klipper camera is whatever the user configured.
        return None;
    };

    let url = report_url?;
    if url.is_empty() {
        return None;
    }

    // `rtsps://1.2.3.4:322/streaming/live/1` -> `rtsps://bblp:code@1.2.3.4:322/...`
    let with_credentials = match url.split_once("://") {
        Some((scheme, rest)) => {
            // A URL that already carries credentials is left alone rather
            // than having a second set spliced in.
            if rest.contains('@') {
                url.to_string()
            } else {
                format!("{scheme}://{CAMERA_USER}:{}@{rest}", bambu.access_code)
            }
        }
        // Not a URL shape this understands. Refused rather than guessed at:
        // a malformed source makes go2rtc fail to load the whole file, which
        // would take every *working* stream down with it.
        None => {
            warn!(
                printer = %bambu.display_name(),
                "the printer reported a camera URL with no scheme; ignoring it"
            );
            return None;
        }
    };

    Some(CameraSource {
        stream_name: printer.base().id.clone(),
        url: with_credentials,
    })
}

/// Renders a go2rtc configuration.
///
/// Hand-written YAML rather than a serializer, for the same reason the
/// `.3mf` reader is hand-rolled: it is a fixed, tiny shape, and a dependency
/// for ten lines of output is a dependency to license and audit. The values
/// are quoted and the keys are our own printer ids, which `fleet.rs`
/// constrains.
///
/// `listen` is explicit rather than left to go2rtc's defaults, because the
/// cloud is told this address and a default that changes between go2rtc
/// versions would change where the stream lives without anything saying so.
/// Basic-auth credentials for go2rtc's API listener.
///
/// The API is what serves WebRTC, so without this anyone who can reach
/// `http://<gateway>:1984` can watch any printer with a camera - and the
/// listener defaults to `:1984`, every interface. Measured against go2rtc
/// 1.9.14, `username`/`password` under `api:` really does enforce it: from a
/// non-loopback address, no credentials and wrong credentials both get 401
/// and the correct ones get 200, on `/api/webrtc`, `/api/ws`,
/// `/api/frame.jpeg` and the web UI alike.
///
/// **Loopback is exempt**, which is a deliberate convenience of go2rtc's and
/// worth knowing twice over: it is why a probe from the gateway itself still
/// works with no credentials, and it is why a probe from the gateway itself
/// cannot be used to check that auth is on. Test from another host.
pub struct ApiAuth {
    pub username: String,
    pub password: String,
}

impl ApiAuth {
    /// The operator's password if they set one, otherwise a fresh random one.
    ///
    /// Generated once per run and then held, never re-derived: `render_config`
    /// is called every `REBUILD_INTERVAL` and its output is compared
    /// byte-for-byte to decide whether to restart go2rtc, so a password that
    /// changed per call would restart it - and drop every live viewer - every
    /// 30 seconds, forever.
    ///
    /// A generated password is never logged. It is written into the config
    /// file, which already holds every printer's access code and is already
    /// documented as a secret, so that is where an operator reads it from -
    /// one secret store rather than two.
    pub fn new() -> anyhow::Result<Self> {
        let password = match std::env::var("CONTINUUM_GO2RTC_PASSWORD") {
            Ok(set) if !set.is_empty() => set,
            // `||` semantics, not `??`: an empty value in a deployment
            // template is "unset", not "the empty password".
            _ => random_secret()?,
        };
        Ok(Self { username: "continuum".to_string(), password })
    }
}

/// 32 bytes of kernel randomness, base64url so it is safe unquoted in YAML.
///
/// Read from `/dev/urandom` with the standard library rather than pulling in
/// a crate for it: the gateway is Linux, this is the one place that needs
/// randomness, and a new dependency would need a licence review (see
/// `continuum-common/docs/LICENSES.md`).
fn random_secret() -> anyhow::Result<String> {
    use base64::Engine;
    use std::io::Read;

    let mut bytes = [0u8; 32];
    std::fs::File::open("/dev/urandom")?.read_exact(&mut bytes)?;
    Ok(base64::engine::general_purpose::URL_SAFE_NO_PAD.encode(bytes))
}

/// Escapes a value for a YAML double-quoted scalar.
///
/// Only needed for an operator-supplied password - a generated one is
/// base64url and has nothing to escape - but a password containing a quote
/// would otherwise produce a config go2rtc cannot parse, and the symptom
/// would be a camera that silently never appears.
fn yaml_quoted(value: &str) -> String {
    value.replace('\\', "\\\\").replace('"', "\\\"")
}

pub fn render_config(api_listen: &str, sources: &[CameraSource], auth: &ApiAuth) -> String {
    let mut out = String::from(
        "# Generated by continuum-proxy. Do not edit: it is rewritten from\n\
         # what the printers themselves report, so an edit here is lost on\n\
         # the next rebuild. Contains printer access codes - treat it as a\n\
         # secret and keep it out of version control.\n",
    );

    // Sorted, so an unchanged fleet renders byte-identical output and the
    // change detection below does not restart go2rtc on every rebuild.
    let ordered: BTreeMap<&str, &str> = sources
        .iter()
        .map(|s| (s.stream_name.as_str(), s.url.as_str()))
        .collect();

    out.push_str("streams:\n");
    if ordered.is_empty() {
        // An empty mapping, written explicitly. `streams:` with nothing
        // under it is a null in YAML, and go2rtc is entitled to treat that
        // differently from an empty map.
        out.push_str("  {}\n");
    }
    for (name, url) in &ordered {
        out.push_str(&format!("  {name}: \"{url}\"\n"));
    }

    out.push_str(&format!("api:\n  listen: \"{api_listen}\"\n"));
    // Not optional, and there is no flag to turn it off. The alternative is
    // an unauthenticated video feed of someone's workshop reachable by
    // anything on their network, which is not a thing to leave behind a
    // setting. Nothing in this crate calls go2rtc's API, so nothing here
    // breaks; a browser cannot use these credentials directly either way -
    // see the CORS note in the module docs.
    out.push_str(&format!(
        "  username: \"{}\"\n  password: \"{}\"\n",
        yaml_quoted(&auth.username),
        yaml_quoted(&auth.password),
    ));

    // Closes go2rtc's own RTSP server, and this has to be explicit.
    //
    // Leaving the key out does NOT leave the server off - go2rtc defaults to
    // :8554. Measured against go2rtc 1.9.14 with a config that omitted it:
    // `rtsp://<gateway>:8554/<printer>` answered a DESCRIBE carrying a real
    // video SDP, with no credentials sent at all. Every printer's camera was
    // republished to anything that could reach the port.
    //
    // Nothing needs it: a browser is served over WebRTC through the API
    // listener above. An empty `listen` is how go2rtc is told not to bind.
    out.push_str("rtsp:\n  listen: \"\"\n");

    // `webrtc:` is deliberately left alone, and with TURN in the picture that
    // is now a decision worth stating rather than an omission.
    //
    // go2rtc keeps its default media port and its default candidate
    // gathering, which produces a host candidate and - measured against
    // 1.9.14 - a server-reflexive one it discovers by STUN on its own. That
    // is everything this end needs. No `ice_servers` here, and in particular
    // **no TURN credentials on the gateway**: the viewer's browser is pinned
    // to relay-only, so the browser allocates the relay and go2rtc simply
    // sends to it from its own candidate. Only one side of a WebRTC session
    // has to hold a relay for the media to traverse one.
    //
    // That asymmetry is what makes this tractable at all, because go2rtc
    // reads its config exactly once at startup: TURN credentials are
    // short-lived, so rotating them here would mean restarting go2rtc and
    // dropping every viewer on a timer. Keeping them browser-side moves the
    // rotation to a request that is already per-viewer.
    //
    // This is not a second open stream server either way: a WebRTC session
    // exists only after an SDP offer through the API, and that API now
    // requires a password.
    out
}

/// Collects every printer that currently has a playable stream.
pub async fn sources(fleet: &SharedFleet) -> Vec<CameraSource> {
    let fleet = fleet.lock().await;
    let mut found = Vec::new();

    for printer in fleet.iter() {
        let report_url = printer
            .print_status()
            .await
            .and_then(|report| report.ipcam)
            .and_then(|ipcam| ipcam.rtsp_url);

        if let Some(source) = source_for(printer, report_url.as_deref()) {
            found.push(source);
        }
    }

    found
}

/// Rewrites the config whenever what the printers report changes, and asks
/// the watchdog to restart go2rtc when it does.
///
/// Restart rather than reload: go2rtc can reload some of its configuration
/// over its own API, but a restart is the behaviour we can be sure of, and
/// the watchdog was already built to restart it. A stream interruption at the
/// moment a printer's camera URL changes is acceptable; a stream that is
/// silently serving the old address is not.
pub async fn run(
    fleet: SharedFleet,
    config_path: String,
    api_listen: String,
    auth: ApiAuth,
    restart: std::sync::Arc<Notify>,
) {
    let mut ticker = tokio::time::interval(REBUILD_INTERVAL);
    let mut last_written: Option<String> = None;

    loop {
        ticker.tick().await;

        // Collected once and kept, so the count logged below describes the
        // config actually written rather than a second, later reading of the
        // fleet that could disagree with it.
        let found = sources(&fleet).await;
        let desired = render_config(&api_listen, &found, &auth);
        if last_written.as_deref() == Some(desired.as_str()) {
            continue;
        }

        // Compare against the file too, not just our own memory of it: on
        // startup `last_written` is `None`, and rewriting an identical file
        // would restart go2rtc - and therefore drop every live viewer - for
        // no reason, every time the daemon restarts.
        if last_written.is_none()
            && let Ok(existing) = tokio::fs::read_to_string(&config_path).await
            && existing == desired
        {
            last_written = Some(desired);
            continue;
        }

        match write_atomically(&config_path, &desired).await {
            Ok(()) => {
                // Counted from the sources, not from the rendered text. It
                // used to be `matches("\n  ").count() - 1`, which reported
                // one stream for a config with none - the `{}` of an empty
                // mapping indents exactly like a stream does. A log line
                // that says a camera is being served when none is makes the
                // one thing this task is for impossible to check.
                let count = found.len();
                // The content is never logged: it holds access codes.
                info!(path = %config_path, streams = count, "wrote go2rtc config, restarting it");
                last_written = Some(desired);
                restart.notify_one();
            }
            Err(err) => warn!(path = %config_path, ?err, "could not write the go2rtc config"),
        }
    }
}

/// Writes through a temporary file and renames.
///
/// go2rtc may be reading this file at any moment - the watchdog restarts it
/// on a five-second loop - and a partially written config is a config that
/// fails to parse, which takes every working stream down. A rename is atomic
/// on the same filesystem, so a reader sees either the old file or the new
/// one.
async fn write_atomically(path: &str, contents: &str) -> std::io::Result<()> {
    let temp = format!("{path}.tmp");
    tokio::fs::write(&temp, contents).await?;
    tokio::fs::rename(&temp, path).await
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::printer::{BambuPrinter, BambuProtocolPreference, BambuTls};

    fn printer(id: &str) -> PrinterHandle {
        PrinterHandle::Bambu(BambuPrinter::new(
            id,
            "Test Printer",
            "192.168.0.21",
            "12345678",
            "SN123",
            BambuTls::Insecure,
            BambuProtocolPreference::Auto,
        ))
    }

    /// A fixed credential, so the byte-identical assertions below stay
    /// meaningful. A real one is 32 random bytes and would make every
    /// rendered config differ from every other.
    fn test_auth() -> ApiAuth {
        ApiAuth { username: "continuum".into(), password: "test-password".into() }
    }

    /// The URL shape confirmed from a real H2C's `ipcam` block.
    #[test]
    fn a_reported_rtsps_url_gets_the_printer_credentials_spliced_in() {
        let source = source_for(&printer("h2c"), Some("rtsps://192.168.0.21:322/streaming/live/1"))
            .expect("an rtsps URL is playable");
        assert_eq!(source.stream_name, "h2c");
        assert_eq!(source.url, "rtsps://bblp:12345678@192.168.0.21:322/streaming/live/1");
    }

    /// What a P1P reports: an `ipcam` block that says a camera exists without
    /// giving anything to connect to. Advertising a stream here would make a
    /// UI offer a player that can never load.
    #[test]
    fn a_printer_that_reports_no_url_has_no_stream() {
        assert_eq!(source_for(&printer("p1p"), None), None);
        assert_eq!(source_for(&printer("p1p"), Some("")), None);
    }

    /// Splicing a second set of credentials into a URL that already has some
    /// would produce `bblp:code@user:pass@host`, which is not a host.
    #[test]
    fn a_url_that_already_carries_credentials_is_left_alone() {
        let source = source_for(&printer("h2c"), Some("rtsps://someone:else@10.0.0.5:322/live"))
            .expect("still playable");
        assert_eq!(source.url, "rtsps://someone:else@10.0.0.5:322/live");
    }

    /// Refused rather than guessed at, because one bad entry makes go2rtc
    /// fail to load the whole file and takes every working stream with it.
    #[test]
    fn a_url_with_no_scheme_is_refused_rather_than_repaired() {
        assert_eq!(source_for(&printer("h2c"), Some("192.168.0.21:322/streaming/live/1")), None);
    }

    /// `streams:` with nothing under it is YAML for null, not for an empty
    /// map, and a gateway with no streamable camera is the normal state of a
    /// P1-only farm - so this is the output that must be valid, not a corner.
    #[test]
    fn an_empty_fleet_renders_an_explicit_empty_map() {
        let config = render_config(":1984", &[], &test_auth());
        assert!(config.contains("streams:\n  {}\n"), "got:\n{config}");
        assert!(config.contains("listen: \":1984\""), "got:\n{config}");
    }

    /// The change detection in `run` compares rendered output, so an
    /// unchanged fleet in a different order must render identically or
    /// go2rtc gets restarted - dropping every live viewer - every 30s.
    #[test]
    fn the_same_fleet_in_a_different_order_renders_identically() {
        let a = CameraSource { stream_name: "aaa".into(), url: "rtsps://one".into() };
        let b = CameraSource { stream_name: "zzz".into(), url: "rtsps://two".into() };
        assert_eq!(
            render_config(":1984", &[a.clone(), b.clone()], &test_auth()),
            render_config(":1984", &[b, a], &test_auth()),
        );
    }

    /// The config must *actively* close go2rtc's RTSP server.
    ///
    /// This test used to assert the opposite thing - that the rendered
    /// config contained no `rtsp:` key - and concluded from that that no
    /// RTSP server was opened. It passed, and it was worthless: go2rtc
    /// defaults to :8554 when the key is absent. Measured against go2rtc
    /// 1.9.14, a config with no `rtsp:` block answered an unauthenticated
    /// DESCRIBE on `rtsp://<gateway>:8554/h2c` with a real video SDP.
    ///
    /// A test that asserts a key is missing cannot tell "off" from
    /// "defaulted on". This one asserts the value that turns it off.
    #[test]
    fn the_generated_config_closes_the_rtsp_server() {
        let source = CameraSource { stream_name: "h2c".into(), url: "rtsps://x".into() };
        let config = render_config(":1984", &[source], &test_auth());
        assert!(config.contains("rtsp:\n  listen: \"\"\n"), "got:\n{config}");
    }

    /// An empty fleet must still close it - a gateway with no cameras is the
    /// common case, and it is the config most likely to be left running.
    #[test]
    fn an_empty_config_closes_the_rtsp_server_too() {
        assert!(render_config(":1984", &[], &test_auth()).contains("rtsp:\n  listen: \"\"\n"));
    }

    /// The API listener is what serves WebRTC, and it defaults to every
    /// interface, so a config without this is a video feed of someone's
    /// workshop open to their whole network.
    ///
    /// Asserts the values, for the same reason as the RTSP test above: a
    /// `username:` key with the wrong content would pass an existence check
    /// and authenticate nobody.
    #[test]
    fn the_generated_config_demands_a_password_on_the_api() {
        let source = CameraSource { stream_name: "h2c".into(), url: "rtsps://x".into() };
        let config = render_config(":1984", &[source], &test_auth());
        assert!(
            config.contains("  username: \"continuum\"\n  password: \"test-password\"\n"),
            "got:\n{config}"
        );
    }

    /// Even with no cameras. A gateway that acquires one later keeps the
    /// config it was already running, and an unauthenticated listener with
    /// no streams is one printer away from an unauthenticated listener with
    /// one.
    #[test]
    fn an_empty_config_demands_a_password_too() {
        assert!(render_config(":1984", &[], &test_auth()).contains("  password: \"test-password\"\n"));
    }

    /// Byte-identical output for the same inputs, which is what stops the
    /// rebuild loop restarting go2rtc.
    ///
    /// The credential is the live hazard here: it is generated once per run
    /// precisely so this holds. Were it re-derived per render, every 30s tick
    /// would see a changed config, restart go2rtc and drop every viewer -
    /// forever, and the only symptom would be video that dies every half
    /// minute.
    #[test]
    fn the_same_fleet_and_credential_render_identically() {
        let source = CameraSource { stream_name: "h2c".into(), url: "rtsps://x".into() };
        assert_eq!(
            render_config(":1984", std::slice::from_ref(&source), &test_auth()),
            render_config(":1984", &[source], &test_auth()),
        );
    }

    /// An operator-supplied password is not guaranteed to be YAML-safe, and
    /// a config go2rtc cannot parse means a camera that silently never
    /// appears - the hardest kind of failure to trace back to a password.
    #[test]
    fn an_awkward_operator_password_is_escaped() {
        let auth = ApiAuth {
            username: "continuum".into(),
            password: r#"he said "hi"\ok"#.into(),
        };
        let config = render_config(":1984", &[], &auth);
        assert!(
            config.contains(r#"  password: "he said \"hi\"\\ok""#),
            "got:\n{config}"
        );
    }
}