//! `flow runner` (docs/m0.md §5): claim a job from OxygenHub, fetch the

//! repository into a cache with the job's token, write the state into a

//! workspace, run it in its tier, stream the log, report the receipt.

//! One job at a time.

use crate::home::{Home, RunnerConfig};

use crate::{microvm, workspace};

use anyhow::{bail, Context, Result};

use flow_core::api::{Claim, ClaimRequest, Finish, LogBatch, Record, MAX_RECORD_TEXT};

use flow_core::{scope_tree_hash, Receipt};

use oxy_core::hash::ChangeHash;

use oxy_core::repo::Repo;

use std::path::PathBuf;

use std::time::{Duration, Instant};

pub struct Hub {

    base: String,

    token: String,

    agent: ureq::Agent,

}

impl Hub {

    pub fn new(cfg: &RunnerConfig) -> Result<Hub> {

        let tls = oxy_core::protocol::tls_client_config(cfg.ca.as_deref()).map_err(|e| anyhow::anyhow!("{e}"))?;

        let agent = ureq::AgentBuilder::new().tls_config(tls).timeout(Duration::from_secs(60)).build();

        Ok(Hub { base: cfg.hub.trim_end_matches('/').to_string(), token: cfg.token.clone(), agent })

    }

    fn post(&self, path: &str, body: &impl serde::Serialize) -> Result<Option<ureq::Response>> {

        let url = format!("{}/api/v1{path}", self.base);

        match self.agent.post(&url).set("Authorization", &format!("Bearer {}", self.token)).send_json(body) {

            Ok(r) if r.status() == 204 => Ok(None),

            Ok(r) => Ok(Some(r)),

            Err(ureq::Error::Status(code, r)) => bail!("{url}: HTTP {code}: {}", r.into_string().unwrap_or_default()),

            Err(e) => bail!("{url}: {e}"),

        }

    }

    pub fn claim(&self, req: &ClaimRequest) -> Result<Option<Claim>> {

        match self.post("/flow/claim", req)? {

            Some(r) => Ok(Some(r.into_json()?)),

            None => Ok(None),

        }

    }

    pub fn log(&self, job: i64, records: Vec<Record>) -> Result<()> {

        self.post(&format!("/flow/jobs/{job}/log"), &LogBatch { records })?;

        Ok(())

    }

    pub fn finish(&self, job: i64, f: &Finish) -> Result<()> {

        self.post(&format!("/flow/jobs/{job}/finish"), f)?;

        Ok(())

    }

}

pub fn serve(home: &Home) -> Result<()> {

    let cfg = home.config.runner.clone().context("flow.toml has no [runner] section")?;

    let hub = Hub::new(&cfg)?;

    let name = cfg.name.clone().unwrap_or_else(|| "flow".into());

    let req = ClaimRequest { runner: name.clone(), runtimes: vec!["microvm".into()] };

    eprintln!("flow runner {name}: polling {}", cfg.hub);

    let mut idle = Duration::from_secs(2);

    loop {

        match hub.claim(&req) {

            Ok(Some(claim)) => {

                idle = Duration::from_secs(2);

                let id = claim.job_id;

                eprintln!("job {id}: {} {} on {}", claim.repo, claim.job.name, claim.heads.first().map(|h| &h[..12]).unwrap_or("-"));

                let finish = run_claim(home, &hub, &cfg, &claim);

                let finish =

                    finish.unwrap_or_else(|e| Finish { exit_code: None, duration_ms: 0, receipt: None, error: Some(format!("{e:#}")) });

                eprintln!(

                    "job {id}: exit {:?}{}",

                    finish.exit_code,

                    finish.error.as_deref().map(|e| format!(" ({e})")).unwrap_or_default()

                );

                if let Err(e) = hub.finish(id, &finish) {

                    eprintln!("job {id}: reporting failed: {e:#}");

                }

            }

            Ok(None) => std::thread::sleep(idle),

            Err(e) => {

                eprintln!("claim: {e:#}");

                std::thread::sleep(idle);

                idle = (idle * 2).min(Duration::from_secs(60));

            }

        }

    }

}

/// Batches records to the hub every second (or every 200 lines).

struct LogSink<'a> {

    hub: &'a Hub,

    job: i64,

    buf: Vec<Record>,

    last: Instant,

}

impl LogSink<'_> {

    fn push(&mut self, mut r: Record) {

        if r.text.len() > MAX_RECORD_TEXT {

            let mut cut = MAX_RECORD_TEXT;

            while !r.text.is_char_boundary(cut) {

                cut -= 1;

            }

            r.text.truncate(cut);

        }

        self.buf.push(r);

        if self.buf.len() >= 200 || self.last.elapsed() >= Duration::from_secs(1) {

            self.flush();

        }

    }

    fn flush(&mut self) {

        if !self.buf.is_empty() {

            if let Err(e) = self.hub.log(self.job, std::mem::take(&mut self.buf)) {

                eprintln!("job {}: log: {e:#}", self.job);

            }

        }

        self.last = Instant::now();

    }

}

fn run_claim(home: &Home, hub: &Hub, cfg: &RunnerConfig, claim: &Claim) -> Result<Finish> {

    let started = Instant::now();

    let mut sink = LogSink { hub, job: claim.job_id, buf: Vec::new(), last: Instant::now() };

    let note =

        |sink: &mut LogSink, text: String| sink.push(Record { t: started.elapsed().as_millis() as u64, stream: "flow".into(), text });

    let heads: Vec<ChangeHash> = claim.heads.iter().map(|h| ChangeHash::from_hex(h).context("bad head")).collect::<Result<_>>()?;

    note(&mut sink, format!("fetching {} for state {}", claim.repo, claim.heads.iter().map(|h| &h[..12]).collect::<Vec<_>>().join("+")));

    let repo = cached_repo(home, cfg, claim)?;

    let scratch = home.root.join("work").join(format!("job-{}", claim.job_id));

    let _ = std::fs::remove_dir_all(&scratch);

    std::fs::create_dir_all(scratch.join("tree"))?;

    let result = (|| -> Result<Finish> {

        let files = workspace::export_state(&repo, &heads, &scratch.join("tree"))?;

        let scope_hash = scope_tree_hash(&claim.job.scope, files.iter().map(|(p, h)| (p.as_str(), *h)));

        workspace::image(&scratch.join("tree"), &scratch.join("workspace.ext4"))?;

        std::fs::remove_dir_all(scratch.join("tree"))?;

        note(

            &mut sink,

            format!(

                "booting a microVM: {} vCPU, {} MiB, rootfs {}",

                claim.sandbox.cpus,

                claim.sandbox.memory_mib,

                &claim.sandbox.rootfs[..12]

            ),

        );

        let outcome = microvm::run(

            home,

            &claim.sandbox,

            &claim.job,

            &scratch.join("workspace.ext4"),

            &scratch,

            Duration::from_secs(claim.timeout_s),

            &mut |r| sink.push(r),

        )?;

        let receipt = outcome.exit_code.map(|code| Receipt {

            job_name: claim.job.name.clone(),

            pipeline_hash: hex32(&claim.pipeline_hash),

            scope_tree_hash: scope_hash,

            inputs: vec![],

            environment: outcome.environment.hash(),

            outputs: vec![],

            exit_code: code as u32,

            duration_ms: outcome.duration_ms,

        });

        Ok(Finish {

            exit_code: outcome.exit_code,

            duration_ms: started.elapsed().as_millis() as u64,

            receipt,

            error: outcome.timed_out.then(|| "stopped at the time limit".to_string()),

        })

    })();

    let _ = std::fs::remove_dir_all(&scratch);

    sink.flush();

    result

}

fn hex32(s: &str) -> [u8; 32] {

    let mut out = [0; 32];

    if let Ok(v) = hex::decode(s) {

        if v.len() == 32 {

            out.copy_from_slice(&v);

        }

    }

    out

}

/// The runner's copy of a repository, fetched up to date with the job's token.

fn cached_repo(home: &Home, cfg: &RunnerConfig, claim: &Claim) -> Result<Repo> {

    let dir: PathBuf = home.root.join("repos").join(claim.repo.replace('/', "__"));

    let set_remote = |repo: &mut Repo| -> Result<()> {

        repo.config.set("remote.origin.url", &claim.clone_url).map_err(|e| anyhow::anyhow!("{e}"))?;

        repo.config.set("remote.origin.token", &claim.token).map_err(|e| anyhow::anyhow!("{e}"))?;

        if let Some(ca) = &cfg.ca {

            repo.config.set("remote.origin.ca", &ca.to_string_lossy()).map_err(|e| anyhow::anyhow!("{e}"))?;

        }

        repo.save_config().map_err(|e| anyhow::anyhow!("{e}"))

    };

    if dir.join(".oxy").is_dir() {

        let mut repo = Repo::open(&dir).map_err(|e| anyhow::anyhow!("{e}"))?;

        set_remote(&mut repo)?;

        repo.fetch("origin").map_err(|e| anyhow::anyhow!("fetch {}: {e}", claim.clone_url))?;

        return Ok(repo);

    }

    // First job for this repository: clone with the job's token.

    std::env::set_var("OXY_TOKEN", &claim.token);

    if let Some(ca) = &cfg.ca {

        std::env::set_var("OXY_CA", ca);

    }

    let cloned = Repo::clone(&claim.clone_url, &dir);

    std::env::remove_var("OXY_TOKEN");

    std::env::remove_var("OXY_CA");

    let mut repo = cloned.map_err(|e| {

        let _ = std::fs::remove_dir_all(&dir);

        anyhow::anyhow!("clone {}: {e}", claim.clone_url)

    })?;

    set_remote(&mut repo)?;

    Ok(repo)

}