/// bcachefs-package-ci: self-hosted .deb build orchestrator
///
/// Reconcile loop that builds Debian packages for bcachefs-tools across
/// a matrix of distros and architectures. Runs as `aptbcachefsorg` user
/// on evilpiepirate.org, with arm64 builds dispatched via ssh to farm1.
///
/// State is filesystem-based under $STATE_DIR:
///   desired              — target commit hash (written by post-receive hook)
///   builds/$commit/
///     source/status      — source package build state
///     source/log         — build log
///     $distro-$arch/     — per-job state + log + artifacts
///
/// The reconcile pattern: no queue. We know what we want (latest commit
/// with packages for every distro×arch) and what we have (filesystem state).
/// The loop fills the gap. New push = update desired, loop picks it up.
/// Same pattern as ktest CI and the filesystem's own reconcile pass.

use anyhow::{Context, Result};
use chrono::Local;
use log::{error, info, warn};
use std::fmt;
use std::fs;
use std::io::{self, Write};
use std::path::{Path, PathBuf};
use std::process::{Child, Command, Stdio};
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;
use std::time::{Duration, Instant};

// ---------------------------------------------------------------------------
// Build matrix
// ---------------------------------------------------------------------------

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
#[serde(rename_all = "lowercase")]
enum Distro {
    Unstable,
    Forky,
    Trixie,
    Questing,
    Plucky,
}

impl Distro {
    const ALL: &[Distro] = &[
        Distro::Unstable,
        Distro::Forky,
        Distro::Trixie,
        Distro::Questing,
        Distro::Plucky,
    ];

    fn is_ubuntu(self) -> bool {
        matches!(self, Distro::Plucky | Distro::Questing)
    }

    fn as_str(self) -> &'static str {
        match self {
            Distro::Unstable => "unstable",
            Distro::Forky => "forky",
            Distro::Trixie => "trixie",
            Distro::Questing => "questing",
            Distro::Plucky => "plucky",
        }
    }

    /// Mirror URL for sbuild chroot creation
    fn mirror(self) -> &'static str {
        if self.is_ubuntu() {
            "http://archive.ubuntu.com/ubuntu"
        } else {
            "http://deb.debian.org/debian"
        }
    }
}

impl fmt::Display for Distro {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(self.as_str())
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
#[serde(rename_all = "lowercase")]
enum Arch {
    Amd64,
    Ppc64el,
    Arm64,
}

impl Arch {
    const ALL: &[Arch] = &[Arch::Amd64, Arch::Ppc64el, Arch::Arm64];

    fn as_str(self) -> &'static str {
        match self {
            Arch::Amd64 => "amd64",
            Arch::Ppc64el => "ppc64el",
            Arch::Arm64 => "arm64",
        }
    }

    /// Whether this arch is built via cross-compilation on amd64
    fn is_cross(self) -> bool {
        matches!(self, Arch::Ppc64el)
    }

    /// Whether this arch is built on a remote host
    fn is_remote(self) -> bool {
        matches!(self, Arch::Arm64)
    }
}

impl fmt::Display for Arch {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str(self.as_str())
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct Job {
    distro: Distro,
    arch:   Arch,
}

impl Job {
    fn name(&self) -> String {
        format!("{}-{}", self.distro, self.arch)
    }
}

impl fmt::Display for Job {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}-{}", self.distro, self.arch)
    }
}

fn build_matrix() -> Vec<Job> {
    let mut jobs = Vec::new();
    for &distro in Distro::ALL {
        for &arch in Arch::ALL {
            // ppc64el cross-build is broken on Ubuntu
            if arch == Arch::Ppc64el && distro.is_ubuntu() {
                continue;
            }
            jobs.push(Job { distro, arch });
        }
    }
    jobs
}

// ---------------------------------------------------------------------------
// Job state (filesystem-backed)
// ---------------------------------------------------------------------------

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum JobStatus {
    Pending,
    Building,
    Done,
    Failed,
}

impl JobStatus {
    fn as_str(self) -> &'static str {
        match self {
            JobStatus::Pending  => "pending",
            JobStatus::Building => "building",
            JobStatus::Done     => "done",
            JobStatus::Failed   => "failed",
        }
    }

    fn parse(s: &str) -> Option<JobStatus> {
        match s.trim() {
            "pending"  => Some(JobStatus::Pending),
            "building" => Some(JobStatus::Building),
            "done"     => Some(JobStatus::Done),
            "failed"   => Some(JobStatus::Failed),
            _          => None,
        }
    }
}

/// Filesystem-backed state for one commit's builds
struct BuildState {
    state_dir: PathBuf,
}

impl BuildState {
    fn new(state_dir: PathBuf) -> Self {
        Self { state_dir }
    }

    /// Read the desired commit hash (written by post-receive hook)
    fn desired_commit(&self) -> Result<Option<String>> {
        let path = self.state_dir.join("desired");
        match fs::read_to_string(&path) {
            Ok(s) => {
                let commit = s.trim().to_string();
                if commit.is_empty() {
                    Ok(None)
                } else {
                    Ok(Some(commit))
                }
            }
            Err(e) if e.kind() == io::ErrorKind::NotFound => Ok(None),
            Err(e) => Err(e).context("reading desired commit"),
        }
    }

    fn commit_dir(&self, commit: &str) -> PathBuf {
        self.state_dir.join("builds").join(commit)
    }

    fn job_dir(&self, commit: &str, job_name: &str) -> PathBuf {
        self.commit_dir(commit).join(job_name)
    }

    fn read_status(&self, commit: &str, job_name: &str) -> JobStatus {
        let status_path = self.job_dir(commit, job_name).join("status");
        match fs::read_to_string(&status_path) {
            Ok(s) => JobStatus::parse(&s).unwrap_or(JobStatus::Pending),
            Err(_) => JobStatus::Pending,
        }
    }

    fn write_status(&self, commit: &str, job_name: &str, status: JobStatus) -> Result<()> {
        let dir = self.job_dir(commit, job_name);
        fs::create_dir_all(&dir)
            .with_context(|| format!("creating job dir {}", dir.display()))?;
        let path = dir.join("status");
        fs::write(&path, status.as_str())
            .with_context(|| format!("writing status to {}", path.display()))?;
        self.regenerate_html();
        Ok(())
    }

    fn regenerate_html(&self) {
        let script = self.state_dir.join("scripts/generate-status-html.sh");
        if script.exists() {
            let _ = Command::new("bash")
                .arg(&script)
                .env("STATE_DIR", &self.state_dir)
                .status();
        }
    }

    fn log_path(&self, commit: &str, job_name: &str) -> PathBuf {
        let now = chrono::Utc::now().format("%Y%m%dT%H%M%S");
        self.job_dir(commit, job_name).join(format!("log-{}", now))
    }

    fn pid_path(&self, commit: &str, job_name: &str) -> PathBuf {
        self.job_dir(commit, job_name).join("pid")
    }

    /// Check if a "building" job's process is actually still running.
    /// If the orchestrator crashed and restarted, a job might be marked
    /// "building" with a stale PID. Detect and recover.
    fn is_process_alive(&self, commit: &str, job_name: &str) -> bool {
        let pid_path = self.pid_path(commit, job_name);
        let pid_str = match fs::read_to_string(&pid_path) {
            Ok(s) => s,
            Err(_) => return false,
        };
        let pid: u32 = match pid_str.trim().parse() {
            Ok(p) => p,
            Err(_) => return false,
        };
        // kill(pid, 0) checks if process exists without sending a signal
        unsafe { libc::kill(pid as i32, 0) == 0 }
    }

    fn result_dir(&self, commit: &str, job_name: &str) -> PathBuf {
        self.job_dir(commit, job_name).join("result")
    }
}

// ---------------------------------------------------------------------------
// Configuration
// ---------------------------------------------------------------------------

struct Config {
    /// Path to the bare git repo
    git_repo:    PathBuf,
    /// Root of the state directory
    state_dir:   PathBuf,
    /// Path to ci/scripts/ in the repo checkout
    scripts_dir: PathBuf,
    /// SSH target for arm64 builds
    arm64_host:  String,
    /// Aptly root directory
    aptly_root:  PathBuf,
    /// Maximum concurrent local builds
    max_local_jobs: usize,
    /// Maximum concurrent remote (arm64) builds
    max_remote_jobs: usize,
    /// Poll interval when idle
    poll_interval: Duration,
    /// Pinned Rust version for rustup
    rust_version: String,
    /// Maximum time for a single build before it gets killed
    build_timeout: Duration,
}

impl Default for Config {
    fn default() -> Self {
        Self {
            git_repo:       PathBuf::from("/var/www/git/bcachefs-tools.git"),
            state_dir:      PathBuf::from("/home/aptbcachefsorg/package-ci"),
            scripts_dir:    PathBuf::from("/home/aptbcachefsorg/package-ci/scripts"),
            arm64_host:     "farm1.evilpiepirate.org".into(),
            aptly_root:     PathBuf::from("/home/aptbcachefsorg/uploads/aptly"),
            max_local_jobs:  2,
            max_remote_jobs: 1,
            poll_interval:   Duration::from_secs(60),
            rust_version:    "1.89.0".into(),
            build_timeout:   Duration::from_secs(2 * 60 * 60), // 2 hours
        }
    }
}

// ---------------------------------------------------------------------------
// Running process tracking
// ---------------------------------------------------------------------------

struct RunningJob {
    child:      Child,
    job_name:   String,
    commit:     String,
    remote:     bool,
    started_at: Instant,
}

// ---------------------------------------------------------------------------
// Orchestrator
// ---------------------------------------------------------------------------

struct Orchestrator {
    config:  Config,
    state:   BuildState,
    running: Vec<RunningJob>,
    last_desired: Option<String>,
}

impl Orchestrator {
    fn new(config: Config) -> Self {
        let state = BuildState::new(config.state_dir.clone());
        Self {
            config,
            state,
            running: Vec::new(),
            last_desired: None,
        }
    }

    /// One iteration of the reconcile loop
    fn reconcile(&mut self) -> Result<()> {
        // Reap finished children first
        self.reap_children()?;

        let commit = match self.state.desired_commit()? {
            Some(c) => c,
            None => return Ok(()),
        };

        // Log when desired commit changes
        if self.last_desired.as_deref() != Some(&commit) {
            info!("[{}] new desired commit", &commit[..12]);
            self.last_desired = Some(commit.clone());
        }

        // Phase 1: source package
        let source_status = self.effective_status(&commit, "source");
        match source_status {
            JobStatus::Done => {}
            JobStatus::Building => {
                // Source still building, can't start binaries yet
                return Ok(());
            }
            JobStatus::Failed => {
                // Nothing to do until new push or manual retry
                return Ok(());
            }
            JobStatus::Pending => {
                info!("[{}] starting source package build", &commit[..12]);
                self.spawn_source_build(&commit)?;
                return Ok(());
            }
        }

        // Phase 2: binary builds
        let matrix = build_matrix();
        let mut still_running = false;
        let mut any_failed = false;

        for job in &matrix {
            let name = job.name();
            let status = self.effective_status(&commit, &name);
            match status {
                JobStatus::Done => {}
                JobStatus::Building => {
                    still_running = true;
                }
                JobStatus::Failed => {
                    any_failed = true;
                }
                JobStatus::Pending => {
                    still_running = true;
                    if self.have_build_slot(job) {
                        info!("[{}] starting binary build: {}", &commit[..12], name);
                        self.spawn_binary_build(&commit, job)?;
                    }
                }
            }
        }

        // Phase 3: publish when nothing is still building/pending
        // Publish even if some builds failed — partial results are better than nothing
        if !still_running {
            let pub_status = self.effective_status(&commit, "publish");
            if pub_status == JobStatus::Pending {
                if any_failed {
                    info!("[{}] some builds failed, publishing successful ones", &commit[..12]);
                } else {
                    info!("[{}] all builds complete, publishing", &commit[..12]);
                }
                self.spawn_publish(&commit)?;
            }
        }

        Ok(())
    }

    /// Get effective status, fixing up stale "building" entries
    fn effective_status(&self, commit: &str, job_name: &str) -> JobStatus {
        let status = self.state.read_status(commit, job_name);
        if status == JobStatus::Building {
            // Check if it's one of our tracked children
            let is_tracked = self.running.iter()
                .any(|r| r.commit == commit && r.job_name == job_name);
            if !is_tracked && !self.state.is_process_alive(commit, job_name) {
                // Stale "building" from a crashed orchestrator run.
                // Reset to failed so it can be retried on next push.
                warn!("[{}] {} marked building but process dead, marking failed",
                      &commit[..12], job_name);
                let _ = self.state.write_status(commit, job_name, JobStatus::Failed);
                return JobStatus::Failed;
            }
        }
        status
    }

    /// Reap finished child processes, kill timed-out builds, update state
    fn reap_children(&mut self) -> Result<()> {
        let mut i = 0;
        while i < self.running.len() {
            // Kill builds that have exceeded the timeout
            if self.running[i].started_at.elapsed() > self.config.build_timeout {
                let job = self.running.remove(i);
                error!("[{}] {} timed out after {:?}, killing",
                       &job.commit[..12], job.job_name,
                       job.started_at.elapsed());
                let mut child = job.child;
                let _ = child.kill();
                let _ = child.wait();
                self.state.write_status(&job.commit, &job.job_name, JobStatus::Failed)?;
                let _ = fs::remove_file(self.state.pid_path(&job.commit, &job.job_name));
                continue;
            }

            match self.running[i].child.try_wait() {
                Ok(Some(exit_status)) => {
                    let job = self.running.remove(i);
                    let status = if exit_status.success() {
                        JobStatus::Done
                    } else {
                        JobStatus::Failed
                    };
                    if status == JobStatus::Failed {
                        let tail = Self::log_tail(&self.state.job_dir(&job.commit, &job.job_name));
                        warn!("[{}] {} failed: {}", &job.commit[..12], job.job_name, tail);
                    } else {
                        info!("[{}] {} finished: {:?}", &job.commit[..12], job.job_name, status);
                    }
                    self.state.write_status(&job.commit, &job.job_name, status)?;
                    let _ = fs::remove_file(self.state.pid_path(&job.commit, &job.job_name));
                }
                Ok(None) => {
                    i += 1;
                }
                Err(e) => {
                    error!("error waiting on child: {}", e);
                    i += 1;
                }
            }
        }
        Ok(())
    }

    fn log_tail(job_dir: &Path) -> String {
        // Find the most recent log file in the job directory
        let latest = fs::read_dir(job_dir).ok()
            .and_then(|entries| {
                entries.filter_map(|e| e.ok())
                    .filter(|e| e.file_name().to_str()
                        .map_or(false, |n| n.starts_with("log-")))
                    .max_by_key(|e| e.file_name())
            });
        let Some(entry) = latest else { return "(no log)".into() };
        let content = fs::read_to_string(entry.path()).unwrap_or_default();
        content.lines()
            .rev()
            .find(|l| !l.trim().is_empty())
            .unwrap_or("(empty log)")
            .to_string()
    }

    fn have_build_slot(&self, job: &Job) -> bool {
        let (local, remote) = self.running.iter()
            .filter(|r| r.job_name != "source" && r.job_name != "publish")
            .fold((0, 0), |(l, r), j| {
                if j.remote { (l, r + 1) } else { (l + 1, r) }
            });

        if job.arch.is_remote() {
            remote < self.config.max_remote_jobs
        } else {
            local < self.config.max_local_jobs
        }
    }

    fn spawn_source_build(&mut self, commit: &str) -> Result<()> {
        self.state.write_status(commit, "source", JobStatus::Building)?;
        let log_file = fs::File::create(self.state.log_path(commit, "source"))
            .context("creating source build log")?;

        let child = Command::new(&self.config.scripts_dir.join("build-source.sh"))
            .arg(commit)
            .arg(&self.config.git_repo)
            .arg(self.state.result_dir(commit, "source"))
            .arg(&self.config.rust_version)
            .stdout(Stdio::from(log_file.try_clone()?))
            .stderr(Stdio::from(log_file))
            .spawn()
            .context("spawning source build")?;

        self.write_pid(commit, "source", &child)?;
        self.running.push(RunningJob {
            child,
            job_name: "source".into(),
            commit: commit.into(),
            remote: false,
            started_at: Instant::now(),
        });
        Ok(())
    }

    fn spawn_binary_build(&mut self, commit: &str, job: &Job) -> Result<()> {
        let name = job.name();
        self.state.write_status(commit, &name, JobStatus::Building)?;
        let log_file = fs::File::create(self.state.log_path(commit, &name))
            .context("creating binary build log")?;

        let source_result = self.state.result_dir(commit, "source");
        let build_result = self.state.result_dir(commit, &name);
        fs::create_dir_all(&build_result)?;

        let child = if job.arch.is_remote() {
            // arm64: scp artifacts to farm1, build there, scp results back
            Command::new(&self.config.scripts_dir.join("build-binary-remote.sh"))
                .arg(&self.config.arm64_host)
                .arg(job.distro.as_str())
                .arg(job.arch.as_str())
                .arg(commit)
                .arg(&source_result)
                .arg(&build_result)
                .arg(&self.config.rust_version)
                .stdout(Stdio::from(log_file.try_clone()?))
                .stderr(Stdio::from(log_file))
                .spawn()
                .with_context(|| format!("spawning remote build for {}", name))?
        } else {
            Command::new(&self.config.scripts_dir.join("build-binary.sh"))
                .arg(job.distro.as_str())
                .arg(job.arch.as_str())
                .arg(commit)
                .arg(&source_result)
                .arg(&build_result)
                .arg(&self.config.rust_version)
                .stdout(Stdio::from(log_file.try_clone()?))
                .stderr(Stdio::from(log_file))
                .spawn()
                .with_context(|| format!("spawning local build for {}", name))?
        };

        self.write_pid(commit, &name, &child)?;
        self.running.push(RunningJob {
            child,
            job_name: name,
            commit: commit.into(),
            remote: job.arch.is_remote(),
            started_at: Instant::now(),
        });
        Ok(())
    }

    fn spawn_publish(&mut self, commit: &str) -> Result<()> {
        self.state.write_status(commit, "publish", JobStatus::Building)?;
        let log_file = fs::File::create(self.state.log_path(commit, "publish"))
            .context("creating publish log")?;

        let child = Command::new(&self.config.scripts_dir.join("publish.sh"))
            .arg(commit)
            .env("STATE_DIR", &self.config.state_dir)
            .stdout(Stdio::from(log_file.try_clone()?))
            .stderr(Stdio::from(log_file))
            .spawn()
            .context("spawning publish")?;

        self.write_pid(commit, "publish", &child)?;
        self.running.push(RunningJob {
            child,
            job_name: "publish".into(),
            commit: commit.into(),
            remote: false,
            started_at: Instant::now(),
        });
        Ok(())
    }

    fn write_pid(&self, commit: &str, job_name: &str, child: &Child) -> Result<()> {
        let pid_path = self.state.pid_path(commit, job_name);
        fs::write(&pid_path, child.id().to_string())
            .with_context(|| format!("writing pid to {}", pid_path.display()))
    }

    /// Kill all running children (for clean shutdown)
    fn kill_all(&mut self) {
        for job in &mut self.running {
            info!("killing {}", job.job_name);
            let _ = job.child.kill();
        }
        // Wait for them to exit
        for job in &mut self.running {
            let _ = job.child.wait();
        }
        self.running.clear();
    }
}

// ---------------------------------------------------------------------------
// Signal handling
// ---------------------------------------------------------------------------

struct Signals {
    shutdown: Arc<AtomicBool>,
    wakeup:   Arc<AtomicBool>,
}

fn setup_signals() -> Result<Signals> {
    let wakeup = Arc::new(AtomicBool::new(false));
    let shutdown = Arc::new(AtomicBool::new(false));

    // SIGUSR1 = wake up (new push arrived)
    signal_hook::flag::register(signal_hook::consts::SIGUSR1, Arc::clone(&wakeup))?;
    // SIGTERM/SIGINT = clean shutdown
    signal_hook::flag::register(signal_hook::consts::SIGTERM, Arc::clone(&shutdown))?;
    signal_hook::flag::register(signal_hook::consts::SIGINT, Arc::clone(&shutdown))?;

    Ok(Signals { shutdown, wakeup })
}

fn write_pid_file(state_dir: &Path) -> Result<()> {
    let pid_path = state_dir.join("orchestrator.pid");
    fs::write(&pid_path, std::process::id().to_string())
        .with_context(|| format!("writing PID file {}", pid_path.display()))
}

fn remove_pid_file(state_dir: &Path) {
    let _ = fs::remove_file(state_dir.join("orchestrator.pid"));
}

// ---------------------------------------------------------------------------
// Main
// ---------------------------------------------------------------------------

fn main() -> Result<()> {
    env_logger::Builder::from_env(env_logger::Env::default().default_filter_or("info"))
        .format(|buf, record| {
            writeln!(buf, "{} [{}] {}",
                     Local::now().format("%Y-%m-%d %H:%M:%S"),
                     record.level(),
                     record.args())
        })
        .init();

    let config = Config::default();
    info!("bcachefs-ci starting");
    info!("  git repo:    {}", config.git_repo.display());
    info!("  state dir:   {}", config.state_dir.display());
    info!("  aptly root:  {}", config.aptly_root.display());
    info!("  arm64 host:  {}", config.arm64_host);
    info!("  rust version: {}", config.rust_version);

    // Ensure state directory exists
    fs::create_dir_all(&config.state_dir)
        .context("creating state directory")?;

    write_pid_file(&config.state_dir)?;

    let poll_interval = config.poll_interval;
    let state_dir = config.state_dir.clone();
    let mut orchestrator = Orchestrator::new(config);

    let signals = setup_signals()?;

    info!("entering reconcile loop (poll every {}s, SIGUSR1 for immediate wake)",
          poll_interval.as_secs());

    while !signals.shutdown.load(Ordering::Relaxed) {
        if let Err(e) = orchestrator.reconcile() {
            error!("reconcile error: {:?}", e);
        }

        // Sleep in small increments; break early on SIGUSR1 or shutdown
        let start = Instant::now();
        while start.elapsed() < poll_interval
            && !signals.shutdown.load(Ordering::Relaxed)
            && !signals.wakeup.swap(false, Ordering::Relaxed)
        {
            std::thread::sleep(Duration::from_millis(500));
        }
    }

    info!("shutting down, killing running builds");
    orchestrator.kill_all();
    remove_pid_file(&state_dir);
    info!("bcachefs-ci stopped");
    Ok(())
}
