//! Large transfers as deltas (`docs/peers.md`): a node joining a swarm with much
//! history, and one returning after much was written, get the bulk as a blob, and no
//! sync message they receive is larger than the threshold.
//!
//! The nodes use 1 KiB chunks, so the threshold is 16 KiB, and a few hundred KiB of
//! writes are well above it.

use std::time::Duration;

use serde_json::json;

use super::{Sim, read, write};
use crate::node::NodeConfig;
use crate::state::AppState;
use crate::swarm::bootstrap::Start;

const SOON: Duration = Duration::from_secs(10);
/// Catching up a few hundred KiB in 1 KiB chunks.
const CATCH_UP: Duration = Duration::from_secs(60);
const CHUNK: u32 = 1024;
/// 16 chunks (`swarm::blob`).
const THRESHOLD: u64 = 16 * CHUNK as u64;

fn small_chunks(config: &mut NodeConfig) {
    config.blob_chunk_bytes = CHUNK;
}

/// About 1 KB that doesn't compress (Automerge compresses large changes).
fn noise(seed: u64) -> String {
    let mut rng = crate::testrand::Rng::new(seed);
    (0..63)
        .map(|_| format!("{:016x}", rng.next_u64()))
        .collect()
}

/// `count` writes of about 1 KB each, under `prefix`.
async fn write_much(node: &AppState, prefix: &str, count: usize) {
    for i in 0..count {
        write(node, &format!("{prefix}/{i}"), json!(noise(i as u64))).await;
    }
}

fn largest_sync_received(node: &AppState) -> u64 {
    node.stats.snapshot().largest_sync_received
}

fn blob_bytes_received(node: &AppState) -> u64 {
    node.traffic.total().received.blob.bytes
}

#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
async fn joining_node_gets_the_history_as_a_delta() {
    let sim = Sim::new(41);
    let a = sim.start_with("a", &[], Start::Genesis, small_chunks);
    sim.wait_ready(&[&a], SOON).await;
    write_much(&a, "history", 200).await;

    let b = sim.start_with("b", &["a"], Start::Join, small_chunks);
    sim.wait_ready(&[&b], CATCH_UP).await;
    sim.wait_converged(&[&a, &b], CATCH_UP).await;
    assert_eq!(read(&b, "history/199").await, Some(json!(noise(199))));

    assert!(
        blob_bytes_received(&b) > 100 * 1_000,
        "{} blob bytes received",
        blob_bytes_received(&b)
    );
    assert!(
        largest_sync_received(&b) <= THRESHOLD,
        "a sync message of {} bytes",
        largest_sync_received(&b)
    );
}

#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
async fn returning_node_gets_what_it_missed_as_a_delta() {
    let sim = Sim::new(42);
    let a = sim.start_with("a", &[], Start::Genesis, small_chunks);
    let b = sim.start_with("b", &["a"], Start::Join, small_chunks);
    let (a, b) = (&a, &b);
    sim.wait_ready(&[a, b], SOON).await;
    write(a, "early", json!(1)).await;
    sim.wait_converged(&[a, b], SOON).await;

    sim.net.take_down("b");
    write_much(a, "while/away", 200).await;
    let blobs_before = blob_bytes_received(b);
    sim.net.bring_up("b");

    sim.wait_converged(&[a, b], CATCH_UP).await;
    assert_eq!(read(b, "while/away/199").await, Some(json!(noise(199))));
    assert!(blob_bytes_received(b) - blobs_before > 100 * 1_000);
    assert!(
        largest_sync_received(b) <= THRESHOLD,
        "a sync message of {} bytes",
        largest_sync_received(b)
    );
}