//! Viewer discovery and command handling.
//!
//! Viewers are MoQ publishers: each creates a broadcast under the viewer prefix
//! with a "command" track containing JSON button states and reset requests. The
//! command track is read through [`moq_json`], so snapshots and merge-patch
//! deltas are reconstructed into a full command before dispatch. This module
//! discovers viewer broadcasts and relays their commands to the emulator thread
//! via an mpsc channel.

use std::time::Duration;

use crate::emulator::Button;

/// A single timestamp entry from the viewer.
#[derive(serde::Deserialize, Debug)]
struct RawTimestamp {
	label: String,
	/// Media timestamp in milliseconds.
	ts: f64,
}

/// A parsed timestamp entry with Duration.
#[derive(Debug)]
pub struct TimestampEntry {
	pub label: String,
	pub ts: Duration,
}

/// A command sent by a viewer.
#[derive(serde::Deserialize, Debug)]
#[serde(tag = "type")]
enum RawCommand {
	#[serde(rename = "buttons")]
	Buttons {
		#[serde(default)]
		buttons: Vec<Button>,
		/// Ordered media timestamps at each pipeline stage.
		#[serde(default)]
		timestamps: Vec<RawTimestamp>,
	},
	#[serde(rename = "reset")]
	Reset {},
}

/// A command with viewer identity attached.
#[derive(Debug)]
pub enum Command {
	/// Full button state for a viewer.
	Buttons {
		buttons: Vec<Button>,
		viewer_id: String,
		/// Ordered media timestamps at each pipeline stage.
		timestamps: Vec<TimestampEntry>,
	},
	Reset,
	/// A viewer disconnected or went offline.
	ViewerLeft {
		viewer_id: String,
	},
}

/// Handles discovered viewers: subscribes to their command tracks.
pub async fn handle_viewers(
	viewer_origin: &mut moq_net::announce::Consumer,
	cmd_tx: &tokio::sync::mpsc::Sender<Command>,
) -> anyhow::Result<()> {
	loop {
		let Some(moq_net::announce::Update { path, broadcast }) = viewer_origin.next().await else {
			break;
		};

		let viewer_id = path.to_string();

		if let Some(broadcast) = broadcast {
			tracing::info!(%viewer_id, "viewer connected");
			let cmd_tx = cmd_tx.clone();
			let vid = viewer_id.clone();
			tokio::spawn(async move {
				if let Err(e) = handle_viewer_commands(&vid, broadcast, &cmd_tx).await {
					tracing::warn!(viewer_id = %vid, error = %e, "viewer command error");
				}
				tracing::info!(viewer_id = %vid, "viewer disconnected");
				let _ = cmd_tx.send(Command::ViewerLeft { viewer_id: vid }).await;
			});
		} else {
			tracing::info!(%viewer_id, "viewer went offline");
			let _ = cmd_tx
				.send(Command::ViewerLeft {
					viewer_id: viewer_id.clone(),
				})
				.await;
		}
	}
	Ok(())
}

async fn handle_viewer_commands(
	viewer_id: &str,
	broadcast: moq_net::broadcast::Consumer,
	cmd_tx: &tokio::sync::mpsc::Sender<Command>,
) -> anyhow::Result<()> {
	let track = broadcast.track("command")?.subscribe(None).await?;
	let mut commands =
		moq_json::snapshot::Consumer::<RawCommand>::new(track, moq_json::snapshot::ConsumerConfig::default());

	loop {
		let command = match commands.next().await {
			Ok(Some(command)) => command,
			Ok(None) => break,
			// A malformed command is skipped; a track error ends the stream.
			Err(moq_json::Error::Json(err)) => {
				tracing::warn!(%viewer_id, %err, "invalid command");
				continue;
			}
			Err(err) => return Err(err.into()),
		};

		match command {
			RawCommand::Buttons { buttons, timestamps } => {
				let timestamps: Vec<_> = timestamps
					.into_iter()
					.filter_map(|t| {
						let ts = Duration::try_from_secs_f64(t.ts / 1000.0).ok()?;
						Some(TimestampEntry { label: t.label, ts })
					})
					.collect();
				let _ = cmd_tx
					.send(Command::Buttons {
						buttons,
						viewer_id: viewer_id.to_string(),
						timestamps,
					})
					.await;
			}
			RawCommand::Reset {} => {
				tracing::info!(%viewer_id, "reset");
				let _ = cmd_tx.send(Command::Reset).await;
			}
		}
	}

	Ok(())
}
