use std::collections::BTreeMap;
use std::ffi::OsString;
use std::fs;
use std::io;
use std::os::unix::ffi::OsStrExt;
use std::os::unix::fs::MetadataExt;
use std::path::{Path, PathBuf};
use std::process::ExitCode;
use std::sync::atomic::{AtomicU64, Ordering};

use lazaret_core::configuration::{
    ConfigurationLoadRequest, SandboxLayoutV1, load_trusted_configuration,
};
use lazaret_core::identity::{CoordinatorId, DomainId, GenerationId};
use lazaret_core::records::{
    ArtifactState, HostProcessOwnershipSlot, PreparedArtifact, ProcessOwnershipCommitAck,
};
use lazaret_linux::process::{
    ProcessOwnershipContext, current_process_identity, dispatch_private_process_role,
};
use lazaret_state_anchor::{
    FuseOverlayfsMount, ProtectedRuntimeFiles, RuntimeStateAnchorAuthority, StateAnchorAcquisition,
    StateAnchorLaunchAuthority, StateAnchorLayout, StateAnchorSandboxView,
    unmount_after_coordinator_loss,
};
use rustix::process::Signal;

static SEQUENCE: AtomicU64 = AtomicU64::new(0);

fn main() -> ExitCode {
    let arguments = std::env::args_os().skip(1).collect::<Vec<_>>();
    if let Some(result) = dispatch_private_process_role(&arguments) {
        return exit(result);
    }
    exit(run())
}

fn exit(result: io::Result<()>) -> ExitCode {
    match result {
        Ok(()) => ExitCode::SUCCESS,
        Err(error) => {
            eprintln!("State Anchor lifecycle fixture failed: {error}");
            ExitCode::FAILURE
        }
    }
}

#[allow(clippy::too_many_lines)]
fn run() -> io::Result<()> {
    match fs::metadata("/dev/fuse") {
        Ok(_) => {}
        Err(error) if error.kind() == io::ErrorKind::NotFound => {
            eprintln!("skipped: /dev/fuse is unavailable");
            return Ok(());
        }
        Err(error) => return Err(error),
    }
    let tree = TestTree::new()?;
    let configuration = configuration(&tree)?;
    let lower = tree.path.join("prepared-lower");
    fs::create_dir_all(lower.join("usr/bin"))?;
    fs::create_dir_all(lower.join("etc"))?;
    fs::write(lower.join("usr/bin/base-tool"), b"base")?;
    for name in ["resolv.conf", "hosts", "hostname"] {
        fs::write(lower.join("etc").join(name), b"image")?;
    }
    let metadata = lower.metadata()?;
    let artifact = PreparedArtifact {
        prepared_artifact_id: lazaret_core::identity::PreparedArtifactId::new([8; 32]),
        source_identity: lazaret_core::identity::SourceIdentity::new(b"fixture".to_vec()),
        selected_manifest_digest: lazaret_core::identity::SelectedManifestDigest::new([9; 32]),
        policy_id: lazaret_core::identity::PolicyId::new([10; 32]),
        id_map_digest: lazaret_core::identity::IdMapDigest::new([11; 32]),
        path: lazaret_core::identity::HostPath::new(lower.as_os_str().as_encoded_bytes().to_vec()),
        device: lazaret_core::identity::DeviceId::new(metadata.dev()),
        inode: lazaret_core::identity::InodeId::new(metadata.ino()),
        state: ArtifactState::Available,
    };
    let layout = StateAnchorLayout::create(&configuration).map_err(io::Error::other)?;

    let launch =
        StateAnchorLaunchAuthority::capture(&layout, &artifact).map_err(io::Error::other)?;
    let runtime_authority = RuntimeStateAnchorAuthority::from_inherited(
        launch.lower_fd(),
        launch.persistent_anchor_fd(),
        launch.runtime_anchor_fd(),
        launch.expected_lower(),
    )
    .map_err(io::Error::other)?;
    let expected = std::cell::Cell::new(None);
    let runtime_mount = runtime_authority
        .acquire(
            current_process_identity()?,
            ProcessOwnershipContext {
                domain_id: DomainId::new([1; 32]),
                generation_id: GenerationId::new(1),
                coordinator_id: CoordinatorId::new([3; 32]),
                slot: HostProcessOwnershipSlot::StateAnchorDaemon,
            },
            |staged| {
                expected.set(Some(staged));
                Ok(())
            },
            |staged| Ok(ProcessOwnershipCommitAck::v1(staged)),
            |readiness| {
                if expected.get() != Some(readiness.staged())
                    || lazaret_linux::filesystem::current_mount_identity(layout.merged())?
                        != readiness.mount()
                {
                    return Err(io::Error::other(
                        "inherited State Anchor readiness changed authority",
                    ));
                }
                Ok(())
            },
        )
        .map_err(io::Error::other)?;
    runtime_mount.unmount().map_err(io::Error::other)?;

    let first = acquire(&layout, &artifact)?;
    fs::write(
        layout.merged().join("usr/bin/installed-tool"),
        b"persistent",
    )?;
    fs::write(layout.merged().join("etc/developer.conf"), b"persistent")?;
    if lower.join("usr/bin/installed-tool").exists()
        || lower.join("etc/developer.conf").exists()
        || !layout.upper().join("usr/bin/installed-tool").exists()
        || !layout.upper().join("etc/developer.conf").exists()
    {
        return Err(io::Error::other(
            "writes did not remain upper-only over the read-only lower",
        ));
    }
    let view = StateAnchorSandboxView::from_mounted(&layout, &artifact, first.mount_identity())
        .map_err(io::Error::other)?;
    view.revalidate().map_err(io::Error::other)?;
    layout
        .replace_protected_runtime_files(&ProtectedRuntimeFiles {
            resolv_conf: b"nameserver 192.0.2.53\n",
            hosts: b"127.0.0.1 localhost\n",
            hostname: b"lazaret\n",
        })
        .map_err(io::Error::other)?;
    let runtime_sources = view.protected_runtime_mounts().collect::<Vec<_>>();
    if runtime_sources.len() != 3
        || runtime_sources
            .iter()
            .any(|(source, _)| source.starts_with(&lower) || source.starts_with(layout.upper()))
    {
        return Err(io::Error::other(
            "protected runtime files are not host-private runtime material",
        ));
    }
    if lower.join("etc/resolv.conf").read_link().is_ok()
        || fs::read(lower.join("etc/resolv.conf"))? != b"image"
        || layout.upper().join("etc/resolv.conf").exists()
        || fs::read(&runtime_sources[0].0)? != b"nameserver 192.0.2.53\n"
    {
        return Err(io::Error::other(
            "runtime-file replacement escaped transient storage",
        ));
    }
    drop(view);
    let wrong = lazaret_linux::filesystem::current_mount_identity(layout.upper())?;
    if unmount_after_coordinator_loss(&layout, wrong).is_ok() {
        return Err(io::Error::other(
            "ownership mismatch unmounted foreign identity",
        ));
    }
    first.unmount().map_err(io::Error::other)?;

    let second = acquire(&layout, &artifact)?;
    if fs::read(layout.merged().join("usr/bin/installed-tool"))? != b"persistent"
        || fs::read(layout.merged().join("etc/developer.conf"))? != b"persistent"
    {
        return Err(io::Error::other(
            "upper state did not persist across remount",
        ));
    }
    let identity = second.mount_identity();
    second.process().send_signal(Signal::KILL)?;
    while !second.process().has_exited()? {
        std::thread::yield_now();
    }
    unmount_after_coordinator_loss(&layout, identity).map_err(io::Error::other)?;
    second
        .finish_after_external_unmount()
        .map_err(io::Error::other)?;
    drop(tree);
    Ok(())
}

fn acquire<'layout, 'configuration>(
    layout: &'layout StateAnchorLayout<'configuration>,
    artifact: &PreparedArtifact,
) -> io::Result<FuseOverlayfsMount<'layout, 'configuration>> {
    let expected = std::cell::Cell::new(None);
    FuseOverlayfsMount::acquire(
        layout,
        StateAnchorAcquisition {
            lower: Path::new(std::ffi::OsStr::from_bytes(artifact.path.as_bytes())),
            expected_lower: (artifact.device.get(), artifact.inode.get()),
            expected_parent: current_process_identity()?,
            ownership: ProcessOwnershipContext {
                domain_id: DomainId::new([1; 32]),
                generation_id: GenerationId::new(2),
                coordinator_id: CoordinatorId::new([3; 32]),
                slot: HostProcessOwnershipSlot::StateAnchorDaemon,
            },
        },
        |staged| {
            expected.set(Some(staged));
            Ok(())
        },
        |staged| {
            if expected.get() != Some(staged) {
                return Err(io::Error::other("staged process identity changed"));
            }
            Ok(ProcessOwnershipCommitAck::v1(staged))
        },
        |readiness| {
            if expected.get() != Some(readiness.staged()) {
                return Err(io::Error::other("ready process identity changed"));
            }
            if lazaret_linux::filesystem::current_mount_identity(layout.merged())?
                != readiness.mount()
            {
                return Err(io::Error::other(
                    "readiness preceded exact mount verification",
                ));
            }
            Ok(())
        },
    )
    .map_err(io::Error::other)
}

struct TestTree {
    path: PathBuf,
}

impl TestTree {
    fn new() -> io::Result<Self> {
        let path = std::env::temp_dir().join(format!(
            "lazaret state-anchor,:{}-{}",
            std::process::id(),
            SEQUENCE.fetch_add(1, Ordering::Relaxed)
        ));
        fs::create_dir(&path)?;
        Ok(Self { path })
    }
}

impl Drop for TestTree {
    fn drop(&mut self) {
        let _ = fs::remove_dir_all(&self.path);
    }
}

fn configuration(
    tree: &TestTree,
) -> io::Result<lazaret_core::configuration::ResolvedDomainConfiguration> {
    let configuration_directory = tree.path.join("configuration");
    let workspace = tree.path.join("workspace");
    let runtime = tree.path.join("runtime");
    fs::create_dir(&configuration_directory)?;
    fs::create_dir(&workspace)?;
    fs::create_dir(&runtime)?;
    let configuration_path = configuration_directory.join("lazaret.toml");
    fs::write(
        &configuration_path,
        format!(
            "schema = \"lazaret-trusted-host-config-v1\"\n[storage]\ndata_root = \"{}\"\n[network]\ndefault_allow = [\"192.0.2.10/32\"]\n[profiles.default]\nimage = \"example.invalid/fixture:v1\"\npersistent_dirs = [\"/usr\", \"/etc\"]\n[profiles.default.readiness]\ndenied = [{{ address = \"10.20.30.40\", port = 443 }}]\npermitted = [{{ address = \"192.0.2.10\", port = 443 }}]\ndns = [{{ resolver = \"198.51.100.53\", query = \"example.invalid\" }}]\n",
            tree.path.join("data").display()
        ),
    )?;
    let layout = SandboxLayoutV1::from_production_layout([
        "/workspace".to_owned(),
        "/proc".to_owned(),
        "/sys".to_owned(),
        "/dev".to_owned(),
        "/run/lazaret".to_owned(),
    ])
    .map_err(io::Error::other)?;
    load_trusted_configuration(ConfigurationLoadRequest {
        explicit_configuration_path: Some(configuration_path),
        selected_profile: "default".to_owned(),
        workspace,
        home: tree.path.join("home"),
        xdg_config_home: None,
        xdg_data_home: None,
        xdg_runtime_dir: runtime,
        environment: BTreeMap::<String, OsString>::new(),
        sandbox_layout: layout,
    })
    .map_err(io::Error::other)
}