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use anyhow::Result;
use async_trait::async_trait;
use automerge::ChangeHash;
use automerge::sync::Message;
use sha2::{Digest, Sha256};
use std::boxed::Box;
use std::future::Future;
use std::pin::Pin;
pub use crate::document::replica::Epoch;
pub mod firewall;
pub mod mycelium;
/// Random identifier of one run of a node (from start to exit).
pub type RunId = [u8; 16];
/// Most heads listed in a keepalive; more are sent as a digest. A head takes 34 bytes on
/// the wire, so 32 of them keep a keepalive within one Mycelium chunk (1300 bytes; see
/// the size test in `mycelium`). There are rarely more heads than nodes that wrote
/// concurrently since the last merging write.
pub const MAX_LISTED_HEADS: usize = 32;
/// A document's heads, compactly: the heads themselves while there are few, otherwise a
/// digest of them. Two summaries are equal exactly when the heads are, whatever form
/// each took (nodes with different limits still agree).
#[derive(Debug, Clone)]
pub enum HeadsSummary {
/// Sorted.
Heads(Vec<ChangeHash>),
/// SHA-256 over the sorted heads.
Digest([u8; 32]),
}
impl HeadsSummary {
pub fn of(mut heads: Vec<ChangeHash>) -> Self {
heads.sort_unstable();
if heads.len() <= MAX_LISTED_HEADS {
Self::Heads(heads)
} else {
Self::Digest(digest_of(&heads))
}
}
/// The digest of the heads, computed if they are listed.
pub fn digest(&self) -> [u8; 32] {
match self {
Self::Heads(heads) => digest_of(heads),
Self::Digest(digest) => *digest,
}
}
/// The heads, if listed.
pub fn heads(&self) -> Option<&[ChangeHash]> {
match self {
Self::Heads(heads) => Some(heads),
Self::Digest(_) => None,
}
}
}
impl PartialEq for HeadsSummary {
fn eq(&self, other: &Self) -> bool {
match (self, other) {
(Self::Heads(a), Self::Heads(b)) => a == b,
_ => self.digest() == other.digest(),
}
}
}
impl Eq for HeadsSummary {}
/// SHA-256 over sorted heads.
fn digest_of(sorted_heads: &[ChangeHash]) -> [u8; 32] {
let mut hasher = Sha256::new();
for head in sorted_heads {
hasher.update(head.0);
}
hasher.finalize().into()
}
/// PING and PONG. Addressed to one peer: `syncs_with_you` is about the recipient.
#[derive(Debug, Clone)]
pub struct Keepalive {
/// Only comparable between nodes on the same epoch.
pub heads: HeadsSummary,
pub epoch: Epoch,
/// The sender is ready (same meaning as `SyncEnvelope::ready`).
pub ready: bool,
/// The sender would sync with the recipient: counts it as an active member on its
/// own epoch.
pub syncs_with_you: bool,
}
#[derive(Debug)]
pub enum ParsedMessage {
Hello(HelloRequest),
HelloReply(HelloReply),
Sync(SyncEnvelope),
Ping(Keepalive),
Pong(Keepalive),
}
impl ParsedMessage {
/// Every message carries the sender's epoch.
pub fn epoch(&self) -> Epoch {
match self {
ParsedMessage::Hello(hello) => hello.epoch,
ParsedMessage::HelloReply(reply) => reply.epoch,
ParsedMessage::Sync(envelope) => envelope.epoch,
ParsedMessage::Ping(keepalive) | ParsedMessage::Pong(keepalive) => keepalive.epoch,
}
}
}
#[derive(Debug, Clone)]
pub struct HelloRequest {
/// The sender's swarm, if it knows it (a new node doesn't yet). A receiver in
/// another swarm doesn't answer.
pub swarm_id: Option<String>,
pub epoch: Epoch,
/// Proof of the swarm key (`swarm::auth`); empty without one.
pub auth: Vec<u8>,
/// The sender is ready (same meaning as `SyncEnvelope::ready`).
pub ready: bool,
/// Random per run of the sender; the reply echoes it.
pub run_id: RunId,
}
#[derive(Debug, Clone)]
pub struct HelloReply {
pub swarm_id: String,
pub peers: Vec<String>,
pub epoch: Epoch,
/// Proof of the swarm key (`swarm::auth`); empty without one.
pub auth: Vec<u8>,
/// The sender is ready.
pub ready: bool,
/// The `run_id` of the HELLO answered. A reply to a HELLO from an earlier run of the
/// recipient (delivered late, or queued while it was down) is ignored.
pub run_id: RunId,
/// How long before this HELLO the sender had last heard from the recipient, if ever
/// (in milliseconds): tells a restarted node how long it was away.
pub away_ms: Option<u64>,
}
#[derive(Debug, Clone)]
pub struct SyncEnvelope {
pub swarm_id: String,
/// Epoch of the document the message was generated from.
pub epoch: Epoch,
pub message: Message,
/// The sender was ready when it generated the message: its document is the swarm's,
/// not one it is still filling (joining, rejoining). Only such a peer can tell a
/// catching-up node that it has everything; an empty document says nothing else.
pub ready: bool,
}
/// A message serialized for the wire. Cloning is cheap (shared buffer).
#[derive(Clone, Debug)]
pub struct EncodedMessage {
pub peer: String,
pub body: bytes::Bytes,
}
pub type HandlerFn = dyn Fn(String, ParsedMessage) -> Pin<Box<dyn Future<Output = Result<()>> + Send>>
+ Send
+ Sync
+ 'static;
pub type MessageHandler = Box<HandlerFn>;
#[async_trait]
pub trait Transport: Send + Sync {
/// This node's identity on the transport (for Mycelium: its public key).
fn local_id(&self) -> &str;
/// Resolves a seed (anything that leads to a node, e.g. an address) to that node's
/// identity, as `local_id` gives it on that node.
async fn resolve_seed(&self, seed: &str) -> Result<String>;
fn encode(&self, peer: &str, message: &ParsedMessage) -> Result<EncodedMessage>;
async fn send_encoded(&self, message: &EncodedMessage) -> Result<()>;
/// Sends an outbound message payload to a targeted peer on a specific topic.
async fn send_message(&self, peer: &str, message: &ParsedMessage) -> Result<()> {
let encoded = self.encode(peer, message)?;
self.send_encoded(&encoded).await
}
/// Starts the long-polling inbound event loops, driving messages to the provided handler closure.
async fn start_consumer(&self, handler: MessageHandler) -> Result<()>;
/// Asynchronously monitors for fatal network client or sub-process failures.
async fn wait_for_exit(&self) -> std::io::Result<std::process::ExitStatus>;
}
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