//! The edge worker in Rust (REBUILD.md, part 2; commands/edge_node.ts): leases
//! ranges from the coordinator, reads their XOVER chunks from its stream,
//! indexes them (the same RangeIndexer as edge-bench, kept identical to
//! the TypeScript by check.ts) and posts the batches. One range per thread.
//!
//!   COORDINATOR_URL=… NODE_TOKEN=… edge-node [--threads N] [--batch-articles 500000] [--ranges N] [--max-mbit M]
//!
//! SIGTERM/SIGINT: each thread gives its range back after the current chunk
//! (the next worker resumes at the last stored batch).

use edge::indexer::{Batch, RangeIndexer};
use edge::names::Rules;
use edge::wire;
use flate2::write::GzEncoder;
use serde::Deserialize;
use std::collections::HashMap;
use std::io::{Read, Write};
use std::sync::atomic::{AtomicBool, AtomicI64, Ordering};
use std::sync::mpsc::{sync_channel, Receiver};
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};

#[global_allocator]
static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;

/// A batch is posted once this many files (completed, or cut at an edge) wait, whatever its articles (commands/edge_node.ts).
const MAX_PENDING_FILES: usize = 100_000;
const RETRIES: u32 = 8;
const IDLE: Duration = Duration::from_secs(30);
/// Without a post for this long, the range's lease is kept alive by a heartbeat.
const HEARTBEAT: Duration = Duration::from_secs(60);

fn log(level: &str, message: &str) {
    println!("[ {level} ] {message}");
}

#[derive(Deserialize)]
struct LeaseJson {
    range: RangeJson,
    rules: RulesJson,
}

#[derive(Deserialize)]
struct RangeJson {
    id: i64,
    group: String,
    start: i64,
    end: i64,
    next: i64,
}

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct RulesJson {
    version: i64,
    priorities: HashMap<String, u32>,
    #[serde(default)]
    dropped_signatures: Vec<String>,
    #[serde(default)]
    dropped_tools: Option<Vec<String>>,
    #[serde(default)]
    per_article_max_parts: Option<u32>,
    #[serde(default)]
    sample_percent: Option<f64>,
    #[serde(default)]
    drop_executables: Option<bool>,
    #[serde(default)]
    dropped_posters: Option<Vec<String>>,
}

impl RulesJson {
    fn rules(self) -> Rules {
        let mut rules = Rules::defaults(self.priorities.into_iter().collect());
        rules.version = self.version;
        rules.dropped_signatures = self.dropped_signatures.into_iter().collect();
        if let Some(tools) = self.dropped_tools {
            rules.dropped_tools = tools.into_iter().collect();
        }
        if let Some(n) = self.per_article_max_parts {
            rules.per_article_max_parts = n;
        }
        if let Some(p) = self.sample_percent {
            rules.sample_percent = p;
        }
        if let Some(e) = self.drop_executables {
            rules.drop_executables = e;
        }
        if let Some(posters) = self.dropped_posters {
            rules.dropped_posters = posters;
        }
        rules
    }
}

#[derive(Deserialize)]
struct StoredJson {
    releases: u64,
    candidates: u64,
}

#[derive(Debug)]
enum ApiError {
    /// 409: the range is no longer this node's (or the batch was stale): stop it, don't give it back.
    LeaseLost(String),
    /// 413: the batch was over the server's body limit; the range is tried again in smaller batches.
    TooLarge(String),
    Other(String),
}

impl std::fmt::Display for ApiError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            ApiError::LeaseLost(m) | ApiError::TooLarge(m) | ApiError::Other(m) => f.write_str(m),
        }
    }
}

/// The coordinator's node API, with retries for network trouble and 5xx (as the TypeScript Api).
struct Api {
    base: String,
    token: String,
    agent: ureq::Agent,
}

impl Api {
    fn new(base: &str, token: &str) -> Self {
        let agent: ureq::Agent = ureq::Agent::config_builder()
            .http_status_as_error(false)
            .timeout_connect(Some(Duration::from_secs(30)))
            .timeout_recv_response(Some(Duration::from_secs(600)))
            .build()
            .into();
        Api { base: base.trim_end_matches('/').to_string(), token: token.to_string(), agent }
    }

    /// A request, retried; `body`: JSON bytes (gzipped when `gzip`).
    fn request(&self, method: &str, path: &str, body: Option<&[u8]>, gzip: bool, accept: &str) -> Result<ureq::http::Response<ureq::Body>, ApiError> {
        let url = format!("{}/api/v1/node/{path}", self.base);
        let auth = format!("Bearer {}", self.token);
        for attempt in 1..=RETRIES {
            let result = match method {
                "GET" => self.agent.get(&url).header("Authorization", &auth).header("Accept", accept).call(),
                _ => {
                    let mut request = self.agent.post(&url).header("Authorization", &auth).header("Accept", accept).header("Content-Type", "application/json");
                    if gzip {
                        request = request.header("Content-Encoding", "gzip");
                    }
                    request.send(body.unwrap_or(b"{}"))
                }
            };
            match result {
                Ok(mut response) => {
                    let status = response.status().as_u16();
                    if status == 409 {
                        let text = response.body_mut().read_to_string().unwrap_or_default();
                        let message = serde_json::from_str::<serde_json::Value>(&text).ok().and_then(|v| v["error"].as_str().map(str::to_string)).unwrap_or_else(|| "lease lost".into());
                        return Err(ApiError::LeaseLost(message));
                    }
                    if status < 500 {
                        return Ok(response);
                    }
                    if attempt == RETRIES {
                        return Err(ApiError::Other(format!("{path}: HTTP {status}")));
                    }
                }
                Err(error) => {
                    if attempt == RETRIES {
                        return Err(ApiError::Other(format!("{path}: {error}")));
                    }
                }
            }
            std::thread::sleep(Duration::from_millis(60_000.min(1000 * 2u64.pow(attempt))));
        }
        unreachable!()
    }

    fn lease(&self) -> Result<Option<LeaseJson>, ApiError> {
        let mut response = self.request("POST", "lease", None, false, "application/json")?;
        match response.status().as_u16() {
            204 => Ok(None),
            200 => {
                let text = response.body_mut().read_to_string().map_err(|e| ApiError::Other(format!("lease: {e}")))?;
                serde_json::from_str(&text).map(Some).map_err(|e| ApiError::Other(format!("lease: {e}")))
            }
            status => Err(ApiError::Other(format!("lease: HTTP {status}"))),
        }
    }

    fn stream(&self, range: i64) -> Result<Box<dyn Read + Send>, ApiError> {
        let response = self.request("GET", &format!("ranges/{range}/stream"), None, false, "application/octet-stream")?;
        if response.status().as_u16() != 200 {
            return Err(ApiError::Other(format!("stream: HTTP {}", response.status())));
        }
        Ok(Box::new(response.into_body().into_reader()))
    }

    /// Posts a batch (gzipped JSON): the releases and candidates stored, and the bytes posted.
    fn batch(&self, range: i64, batch: &Batch) -> Result<(u64, u64, usize), ApiError> {
        let json = wire::to_json(batch);
        let mut gz = GzEncoder::new(Vec::with_capacity(json.len() / 3), flate2::Compression::new(1));
        gz.write_all(&json).unwrap();
        let body = gz.finish().unwrap();
        let mut response = self.request("POST", &format!("ranges/{range}/batches"), Some(&body), true, "application/json")?;
        if response.status().as_u16() == 413 {
            return Err(ApiError::TooLarge(format!("batch: HTTP {} ({} MB gzipped, {} MB of JSON)", response.status(), body.len() / 1_000_000, json.len() / 1_000_000)));
        }
        if response.status().as_u16() != 200 {
            return Err(ApiError::Other(format!("batch: HTTP {}", response.status())));
        }
        let text = response.body_mut().read_to_string().map_err(|e| ApiError::Other(format!("batch: {e}")))?;
        let stored: StoredJson = serde_json::from_str(&text).map_err(|e| ApiError::Other(format!("batch: {e}")))?;
        Ok((stored.releases, stored.candidates, body.len()))
    }

    fn call(&self, range: i64, action: &str) -> Result<(), ApiError> {
        let response = self.request("POST", &format!("ranges/{range}/{action}"), None, false, "application/json")?;
        match response.status().as_u16() {
            200..=299 => Ok(()),
            status => Err(ApiError::Other(format!("{action}: HTTP {status}"))),
        }
    }

    fn corrupt(&self, range: i64, from: i64) -> Result<(), ApiError> {
        let body = format!("{{\"from\":{from}}}");
        let response = self.request("POST", &format!("ranges/{range}/corrupt"), Some(body.as_bytes()), false, "application/json")?;
        match response.status().as_u16() {
            200..=299 => Ok(()),
            status => Err(ApiError::Other(format!("corrupt: HTTP {status}"))),
        }
    }
}

/// One frame of the range's stream: a chunk inflated (or why it didn't), or a keep-alive.
enum Frame {
    Chunk { from: i64, to: i64, text: Result<Vec<u8>, String> },
    KeepAlive,
    End,
    Failed(String),
}

/// Reads frames (8 B from, 8 B to, 4 B length, data) and inflates them, one frame ahead of the indexer.
fn read_frames(mut stream: Box<dyn Read + Send>, bytes_per_second: Option<f64>) -> Receiver<Frame> {
    let (tx, rx) = sync_channel::<Frame>(2);
    std::thread::spawn(move || {
        let mut decompressor = libdeflater::Decompressor::new();
        let started = Instant::now();
        let mut read_bytes = 0f64;
        loop {
            let mut head = [0u8; 20];
            match read_full(&mut stream, &mut head) {
                Ok(0) => {
                    let _ = tx.send(Frame::End);
                    return;
                }
                Ok(20) => {}
                Ok(n) => {
                    let _ = tx.send(Frame::Failed(format!("stream ended inside a frame ({n} bytes)")));
                    return;
                }
                Err(e) => {
                    let _ = tx.send(Frame::Failed(format!("stream: {e}")));
                    return;
                }
            }
            let from = u64::from_be_bytes(head[0..8].try_into().unwrap()) as i64;
            let to = u64::from_be_bytes(head[8..16].try_into().unwrap()) as i64;
            let length = u32::from_be_bytes(head[16..20].try_into().unwrap()) as usize;
            let mut data = vec![0u8; length];
            match read_full(&mut stream, &mut data) {
                Ok(n) if n == length => {}
                Ok(n) => {
                    let _ = tx.send(Frame::Failed(format!("stream ended inside a frame ({} of {length} bytes)", n)));
                    return;
                }
                Err(e) => {
                    let _ = tx.send(Frame::Failed(format!("stream: {e}")));
                    return;
                }
            }
            // --max-mbit: read no faster than the cap (TCP holds the coordinator back).
            if let Some(rate) = bytes_per_second {
                read_bytes += (20 + length) as f64;
                let due = Duration::from_secs_f64(((read_bytes - rate) / rate).max(0.0));
                let elapsed = started.elapsed();
                if due > elapsed {
                    std::thread::sleep(due - elapsed);
                }
            }
            let frame = if length == 0 && from == 0 {
                Frame::KeepAlive
            } else {
                Frame::Chunk { from, to, text: inflate(&data, &mut decompressor) }
            };
            if tx.send(frame).is_err() {
                return;
            }
        }
    });
    rx
}

/// Reads until `buf` is full or the stream ends: the bytes read.
fn read_full(stream: &mut dyn Read, buf: &mut [u8]) -> std::io::Result<usize> {
    let mut at = 0;
    while at < buf.len() {
        match stream.read(&mut buf[at..]) {
            Ok(0) => break,
            Ok(n) => at += n,
            Err(e) if e.kind() == std::io::ErrorKind::Interrupted => continue,
            Err(e) => return Err(e),
        }
    }
    Ok(at)
}

/// A chunk as the news server sent it (zlib; gzip too), whole.
fn inflate(raw: &[u8], d: &mut libdeflater::Decompressor) -> Result<Vec<u8>, String> {
    let mut out = vec![0u8; raw.len() * 4 + 4096];
    loop {
        let result = if raw.starts_with(&[0x1f, 0x8b]) { d.gzip_decompress(raw, &mut out) } else { d.zlib_decompress(raw, &mut out) };
        match result {
            Ok(n) => {
                out.truncate(n);
                return Ok(out);
            }
            Err(libdeflater::DecompressionError::InsufficientSpace) => out.resize(out.len() * 2, 0),
            Err(e) => return Err(e.to_string()),
        }
    }
}

struct Config {
    batch_articles: i64,
    bytes_per_second: Option<f64>,
    /// Ranges whose batch was too large (413), and how much smaller their batches are now (halved each time).
    smaller: Mutex<HashMap<i64, i64>>,
}

impl Config {
    /// Articles and pending files a batch of this range is posted at.
    fn limits(&self, range: i64) -> (i64, usize) {
        let divisor = self.smaller.lock().unwrap().get(&range).copied().unwrap_or(1);
        (self.batch_articles / divisor, MAX_PENDING_FILES / divisor as usize)
    }
}

#[derive(Default)]
struct Totals {
    headers: u64,
    releases: u64,
    candidates: u64,
    bytes: usize,
    post_ms: u128,
}

/// One leased range, start to finish (commands/edge_node.ts runRange).
fn run_range(api: &Arc<Api>, lease: LeaseJson, config: &Config, stopping: &AtomicBool) {
    let range = lease.range;
    let started = Instant::now();
    let mut indexer = RangeIndexer::new(&range.group, range.start, range.end, range.next, lease.rules.rules(), 5);
    let totals = Arc::new(Mutex::new(Totals::default()));
    let post_error: Arc<Mutex<Option<ApiError>>> = Arc::new(Mutex::new(None));
    let last_contact = Arc::new(AtomicI64::new(0));
    let since = Instant::now();
    // Posts in order on their own thread; the indexer goes on meanwhile (one batch may wait).
    let (post_tx, post_rx) = sync_channel::<Batch>(1);
    let poster = {
        let (api, totals, post_error, last_contact) = (api.clone(), totals.clone(), post_error.clone(), last_contact.clone());
        std::thread::spawn(move || {
            for batch in post_rx {
                if post_error.lock().unwrap().is_some() {
                    continue;
                }
                let at = Instant::now();
                match api.batch(range.id, &batch) {
                    Ok((releases, candidates, bytes)) => {
                        let mut t = totals.lock().unwrap();
                        t.post_ms += at.elapsed().as_millis();
                        t.bytes += bytes;
                        t.headers += batch.headers;
                        t.releases += releases;
                        t.candidates += candidates;
                        last_contact.store(since.elapsed().as_millis() as i64, Ordering::Relaxed);
                    }
                    Err(e) => *post_error.lock().unwrap() = Some(e),
                }
            }
        })
    };
    let frames = match api.stream(range.id) {
        Ok(stream) => read_frames(stream, config.bytes_per_second),
        Err(e) => {
            log("error", &format!("Range {} failed: {e}; giving it back.", range.id));
            let _ = api.call(range.id, "release");
            return;
        }
    };
    let (batch_articles, max_pending) = config.limits(range.id);
    let mut batch_from = range.next;
    let mut reached_end = false;
    let mut corrupt: Option<(i64, i64, String)> = None;
    let mut failure: Option<String> = None;
    for frame in frames.iter() {
        if stopping.load(Ordering::Relaxed) || post_error.lock().unwrap().is_some() {
            break;
        }
        // Keep the lease while no batch goes out (slow ranges wait for the spool).
        if since.elapsed().as_millis() as i64 - last_contact.load(Ordering::Relaxed) > HEARTBEAT.as_millis() as i64 {
            last_contact.store(since.elapsed().as_millis() as i64, Ordering::Relaxed);
            let _ = api.call(range.id, "heartbeat");
        }
        match frame {
            Frame::KeepAlive => continue,
            Frame::End => break,
            Frame::Failed(e) => {
                failure = Some(e);
                break;
            }
            Frame::Chunk { from, to, text } => {
                let data = match text {
                    Ok(data) => data,
                    Err(e) => {
                        corrupt = Some((from, to, e));
                        break;
                    }
                };
                indexer.add_text(&String::from_utf8_lossy(&data), to + 1);
                reached_end = to >= range.end;
                if reached_end {
                    indexer.finish();
                }
                if reached_end || to + 1 - batch_from >= batch_articles || indexer.pending() >= max_pending {
                    if post_tx.send(indexer.take()).is_err() {
                        break;
                    }
                    batch_from = to + 1;
                }
                if reached_end {
                    break;
                }
            }
        }
    }
    drop(post_tx);
    let _ = poster.join();
    let post_error = post_error.lock().unwrap().take();
    if let Some((from, to, e)) = corrupt {
        // The server's compressed reply cut short: reported, fetched plain next time.
        log("warn", &format!("Range {}: chunk {from}–{to} doesn't inflate ({e}); reported, the range goes back", range.id));
        let _ = api.corrupt(range.id, from);
        return;
    }
    match post_error {
        Some(ApiError::LeaseLost(m)) => {
            log("warn", &format!("Range {}: {m}", range.id));
            return;
        }
        Some(ApiError::TooLarge(m)) => {
            // Batches already stored stay; from the resume point on, half the size (a batch is at least a chunk).
            let divisor = {
                let mut smaller = config.smaller.lock().unwrap();
                let d = smaller.entry(range.id).or_insert(1);
                *d = (*d * 2).min(64);
                *d
            };
            log("warn", &format!("Range {}: {m}; giving it back, its batches 1/{divisor} the size from now on.", range.id));
            let _ = api.call(range.id, "release");
            return;
        }
        Some(ApiError::Other(m)) => {
            log("error", &format!("Range {} failed: {m}; giving it back.", range.id));
            let _ = api.call(range.id, "release");
            return;
        }
        None => {}
    }
    if let Some(e) = failure {
        log("error", &format!("Range {} failed: {e}; giving it back.", range.id));
        let _ = api.call(range.id, "release");
        return;
    }
    if !reached_end {
        log("info", &format!("Range {}: giving it back.", range.id));
        let _ = api.call(range.id, "release");
        return;
    }
    match api.call(range.id, "finish") {
        Ok(()) => {
            let t = totals.lock().unwrap();
            let seconds = started.elapsed().as_secs_f64();
            log(
                "info",
                &format!(
                    "{} {}–{}: {} headers in {:.0} s ({:.0}/s), {} release chunks, {} probe candidates; posted {:.1} MB in {:.1} s.",
                    range.group,
                    range.start,
                    range.end,
                    t.headers,
                    seconds,
                    t.headers as f64 / seconds,
                    t.releases,
                    t.candidates,
                    t.bytes as f64 / 1e6,
                    t.post_ms as f64 / 1000.0
                ),
            );
        }
        Err(e) => log("warn", &format!("Range {}: {e}", range.id)),
    }
}

fn main() {
    let args: Vec<String> = std::env::args().collect();
    let flag = |name: &str| args.iter().position(|a| a == name).and_then(|i| args.get(i + 1)).cloned();
    let url = std::env::var("COORDINATOR_URL").expect("COORDINATOR_URL is needed");
    let token = std::env::var("NODE_TOKEN").expect("NODE_TOKEN is needed");
    let threads: usize = flag("--threads")
        .or_else(|| std::env::var("EDGE_PROCESSES").ok())
        .map(|v| v.parse().unwrap())
        .filter(|&n| n > 0)
        .unwrap_or_else(|| std::thread::available_parallelism().map(|n| n.get()).unwrap_or(1));
    let ranges: Option<usize> = flag("--ranges").map(|v| v.parse().unwrap());
    let max_mbit: Option<f64> = flag("--max-mbit").or_else(|| std::env::var("EDGE_MAX_MBIT").ok()).map(|v| v.parse().unwrap()).filter(|&m: &f64| m > 0.0);
    let config = Arc::new(Config {
        batch_articles: flag("--batch-articles").map(|v| v.parse().unwrap()).unwrap_or(500_000),
        // The node's cap, shared by its threads.
        bytes_per_second: max_mbit.map(|m| m * 1e6 / 8.0 / threads as f64),
        smaller: Mutex::new(HashMap::new()),
    });
    let stopping = Arc::new(AtomicBool::new(false));
    signal_hook::flag::register(signal_hook::consts::SIGTERM, stopping.clone()).unwrap();
    signal_hook::flag::register(signal_hook::consts::SIGINT, stopping.clone()).unwrap();
    let api = Arc::new(Api::new(&url, &token));
    log("info", &format!("Starting {threads} worker threads{}.", max_mbit.map(|m| format!(" (download cap {m} Mbit/s)")).unwrap_or_default()));
    let workers: Vec<_> = (0..threads)
        .map(|_| {
            let (api, config, stopping) = (api.clone(), config.clone(), stopping.clone());
            std::thread::spawn(move || {
                let mut done = 0;
                while !stopping.load(Ordering::Relaxed) && ranges.is_none_or(|n| done < n) {
                    match api.lease() {
                        Ok(Some(lease)) => {
                            run_range(&api, lease, &config, &stopping);
                            done += 1;
                        }
                        Ok(None) if ranges.is_some() => break,
                        Ok(None) => idle(&stopping),
                        Err(e) => {
                            log("warn", &format!("Lease failed: {e}"));
                            idle(&stopping);
                        }
                    }
                }
            })
        })
        .collect();
    for worker in workers {
        let _ = worker.join();
    }
}

fn idle(stopping: &AtomicBool) {
    let until = Instant::now() + IDLE;
    while Instant::now() < until && !stopping.load(Ordering::Relaxed) {
        std::thread::sleep(Duration::from_millis(500));
    }
}