use std::cell::RefCell;
use std::ffi::{OsStr, OsString};
use std::fmt;
use std::fs::File;
use std::io::{Read, Write};
use std::os::fd::{AsFd, OwnedFd};
use std::os::unix::ffi::OsStringExt;
use std::os::unix::fs::{FileExt, PermissionsExt};
use std::path::{Path, PathBuf};
use std::sync::{Arc, Mutex};

use lazaret_core::configuration::{ConfinedPathPlan, ResolvedDomainConfiguration};
use lazaret_core::identity::{BundleDigest, ContainerId, HostPath, MountIdentity};
use lazaret_core::network::{ReachabilityExpectation, derive_ipv4_policy};
use lazaret_core::records::{
    Generation, GenerationIdentity, HostProcessOwnershipSlot, IpAddress, PreparedArtifact, Session,
};
use lazaret_ignored_workspace::git_common_directory;
use lazaret_linux::filesystem::{RegularFileMailbox, mount_identity, namespace_identity};
use lazaret_linux::process::{
    ProcessOwnershipContext, TargetCommand, child_broker, current_process_identity,
};
use lazaret_runtime_supervisor::network::NetworkProbeRequest;
use lazaret_runtime_supervisor::sandbox::{
    RootProcess, SandboxBuildRequest, SandboxBundle, build_sandbox_bundle,
    build_sandbox_bundle_with_workspace,
};
use lazaret_runtime_supervisor::supervision::{
    RuntimeGitRoutingAuthority, RuntimeGitRoutingLaunch, RuntimeNetworkLaunch,
    RuntimeSupervisorLaunch,
};
use lazaret_state_anchor::{StateAnchorLaunchAuthority, StateAnchorLayout};
use lazaret_storage_catalog::Catalog;
use rustix::event::{PollFd, PollFlags, Timespec, poll};
use rustix::fs::{
    AtFlags, FileType, Mode, OFlags, RawDir, ResolveFlags, fchmod, fstat, mkdirat, openat2, statat,
    unlinkat,
};
use rustix::io::{FdFlags, dup, fcntl_setfd};
use rustix::pipe::{PipeFlags, pipe_with};
use sha2::{Digest, Sha256};

use crate::bootstrap::{BootstrapPlan, CoordinatorLifecycle, coordinator_lifecycle};
use crate::control::RunscNonInteractiveExecutor;
use crate::domain_store::HostCoordinatorDomainStore;
use crate::terminal::RunscInteractiveSessionExecutor;
use crate::waiter::{BootstrapWaitOutcome, BootstrapWaiterFace};

const NETWORK_NAMESPACE_PATH: &str = "/proc/self/ns/net";

#[derive(Debug)]
pub struct ColdStartError(String);

impl fmt::Display for ColdStartError {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter.write_str(&self.0)
    }
}

impl std::error::Error for ColdStartError {}

impl ColdStartError {
    pub(crate) fn service(error: impl fmt::Display) -> Self {
        Self(error.to_string())
    }
}

fn failure(error: impl fmt::Display) -> ColdStartError {
    ColdStartError(error.to_string())
}

pub struct ColdStartInputs<'a> {
    pub store: Arc<HostCoordinatorDomainStore>,
    pub catalog: &'a Catalog,
    pub configuration: &'a ResolvedDomainConfiguration,
    pub generation: Generation,
    pub prepared_artifact: &'a PreparedArtifact,
    pub prepared_artifact_authority: &'a File,
    pub prepared_artifact_label: &'a Path,
    pub root_process: RootProcess,
    pub resolver_addresses: Vec<IpAddress>,
    pub network_probe: NetworkProbeRequest,
    pub reachability: ReachabilityExpectation,
    pub container_id: ContainerId,
    pub invoking_uid: u32,
    pub escalation_client: &'a File,
    pub sandbox_init: &'a File,
}

pub struct BootstrapOwnerGuard {
    descriptor: OwnedFd,
}

impl BootstrapOwnerGuard {
    /// Adopts the private bootstrap entry's pipe standard input.
    ///
    /// # Errors
    /// Refuses a standard input that cannot be duplicated or is not a pipe.
    pub fn from_stdin() -> Result<Self, ColdStartError> {
        let stdin = std::io::stdin();
        Self::from_inherited(dup(&stdin).map_err(failure)?)
    }

    /// Adopts an inherited bootstrap-owner lifetime pipe without PID sampling.
    ///
    /// # Errors
    /// Refuses a descriptor that is not a pipe or cannot be confined to this process.
    pub fn from_inherited(descriptor: OwnedFd) -> Result<Self, ColdStartError> {
        let metadata = fstat(&descriptor).map_err(failure)?;
        if !FileType::from_raw_mode(metadata.st_mode).is_fifo() {
            return Err(ColdStartError(
                "bootstrap-owner lifetime descriptor is not a pipe".into(),
            ));
        }
        fcntl_setfd(descriptor.as_fd(), FdFlags::CLOEXEC).map_err(failure)?;
        Ok(Self { descriptor })
    }

    /// Observes whether the exact retained bootstrap-owner pipe still has a writer.
    ///
    /// # Errors
    /// Returns a polling failure for the retained descriptor.
    pub fn is_live(&self) -> std::io::Result<bool> {
        let mut descriptors = [PollFd::new(&self.descriptor, PollFlags::IN)];
        poll(&mut descriptors, Some(&Timespec::default()))?;
        Ok(!descriptors[0]
            .revents()
            .intersects(PollFlags::IN | PollFlags::HUP | PollFlags::ERR))
    }
}

pub struct ColdStart<'a> {
    store: Arc<HostCoordinatorDomainStore>,
    catalog: &'a Catalog,
    configuration: &'a ResolvedDomainConfiguration,
    generation: Generation,
    generation_identity: GenerationIdentity,
    prepared_artifact: &'a PreparedArtifact,
    state_anchor_layout: StateAnchorLayout<'a>,
    runtime_launch: Option<RuntimeSupervisorLaunch>,
    sandbox_bundle: SandboxBundle,
    network_policy: lazaret_core::network::CanonicalDerivedNetworkPolicy,
    network_probe: NetworkProbeRequest,
    reachability: ReachabilityExpectation,
    container_id: ContainerId,
    runtime_root: PathBuf,
    bundle_digest: BundleDigest,
    invoking_uid: u32,
    staging: RuntimeStaging,
    git_routing: Option<GitRoutingLayout>,
}

impl<'a> ColdStart<'a> {
    /// Stages one generation from validated component authorities.
    ///
    /// # Errors
    /// Refuses mismatched generation/configuration/probe inputs, changed host authority, unsafe
    /// staging paths, or component construction failure.
    #[allow(clippy::too_many_lines)]
    pub fn stage(inputs: ColdStartInputs<'a>) -> Result<Self, ColdStartError> {
        require_inputs(&inputs)?;
        let runtime_domain = host_path(
            inputs
                .configuration
                .runtime_domain_root()
                .canonical_label()
                .as_bytes(),
        );
        let state_anchor_layout = StateAnchorLayout::create(inputs.configuration)
            .map_err(|error| failure(format!("State Anchor layout: {error}")))?;
        let staging = RuntimeStaging::create(
            inputs.configuration.runtime_domain_root(),
            inputs.container_id,
            inputs.escalation_client,
            inputs.sandbox_init,
            inputs.invoking_uid,
        )
        .map_err(|error| failure(format!("runtime staging: {error}")))?;
        let git_routing = GitRoutingLayout::create(
            inputs.configuration,
            inputs.container_id,
            inputs.invoking_uid,
        )
        .map_err(|error| failure(format!("Git-routing staging: {error}")))?;
        let expected_network_namespace = namespace_identity(Path::new(NETWORK_NAMESPACE_PATH))
            .map_err(|error| failure(format!("network namespace: {error}")))?;
        let request = SandboxBuildRequest {
            configuration: inputs.configuration,
            container_id: inputs.container_id,
            expected_network_namespace,
            root_process: inputs.root_process,
            terminal: None,
            prepared_root: inputs.prepared_artifact_label.to_owned(),
        };
        let sandbox_bundle = match &git_routing {
            Some(git_routing) => {
                build_sandbox_bundle_with_workspace(request, git_routing.mountpoint_label.clone())
            }
            None => build_sandbox_bundle(request),
        }
        .map_err(|error| failure(format!("sandbox bundle: {error}")))?;
        staging
            .write_bundle(sandbox_bundle.specification_json())
            .map_err(|error| failure(format!("bundle staging: {error}")))?;
        let network_policy = derive_ipv4_policy(inputs.configuration, inputs.resolver_addresses)
            .map_err(|error| failure(format!("network policy: {error}")))?;
        let ownership = ProcessOwnershipContext {
            domain_id: inputs.generation.domain_id,
            generation_id: inputs.generation.generation_id,
            coordinator_id: inputs.generation.coordinator_id,
            slot: HostProcessOwnershipSlot::SandboxRuntimeSupervisor,
        };
        let state_anchor = StateAnchorLaunchAuthority::capture_retained(
            &state_anchor_layout,
            inputs.prepared_artifact,
            inputs.prepared_artifact_label,
            inputs.prepared_artifact_authority,
        )
        .map_err(|error| failure(format!("State Anchor authority: {error}")))?;
        let mut runtime_launch = RuntimeSupervisorLaunch::from_networked_runsc_command(
            ownership,
            sandbox_bundle.command(),
            RuntimeNetworkLaunch {
                policy: &network_policy,
                configuration_fingerprint: inputs.generation.configuration_fingerprint,
                network_sidecar_id: inputs.generation.network_sidecar_id,
            },
        )
        .map_err(|error| failure(format!("Runtime Supervisor launch: {error}")))?
        .with_state_anchor(state_anchor)
        .map_err(|error| failure(format!("Runtime Supervisor handoff: {error}")))?;
        if let Some(git_routing) = &git_routing {
            runtime_launch = runtime_launch
                .with_git_routing(
                    git_routing
                        .launch_authority(inputs.configuration)
                        .map_err(|error| failure(format!("Git-routing authority: {error}")))?,
                )
                .map_err(|error| failure(format!("Runtime Supervisor handoff: {error}")))?;
        }
        let bundle_digest =
            BundleDigest::new(Sha256::digest(sandbox_bundle.specification_json()).into());
        let generation_identity = GenerationIdentity {
            agent_profile: inputs.configuration.selected_profile().to_owned(),
            domain_id: inputs.generation.domain_id,
            generation_id: inputs.generation.generation_id,
            configuration_fingerprint: inputs.generation.configuration_fingerprint,
            coordinator_id: inputs.generation.coordinator_id,
            sandbox_id: inputs.generation.sandbox_id,
        };
        Ok(Self {
            store: inputs.store,
            catalog: inputs.catalog,
            configuration: inputs.configuration,
            generation: inputs.generation,
            generation_identity,
            prepared_artifact: inputs.prepared_artifact,
            state_anchor_layout,
            runtime_launch: Some(runtime_launch),
            sandbox_bundle,
            network_policy,
            network_probe: inputs.network_probe,
            reachability: inputs.reachability,
            container_id: inputs.container_id,
            runtime_root: runtime_domain.join("runsc"),
            bundle_digest,
            invoking_uid: inputs.invoking_uid,
            staging,
            git_routing,
        })
    }

    /// Runs cold start and exposes the exact retained lifecycle to one service loop.
    ///
    /// # Errors
    /// Returns staging, lifecycle, or service-loop failure. The service is single-use.
    pub fn run<Service>(
        mut self,
        bootstrap_owner: Session,
        owner_guard: &BootstrapOwnerGuard,
        service: Service,
    ) -> Result<(), ColdStartError>
    where
        Service: FnOnce(
            &Mutex<CoordinatorLifecycle<'_, '_>>,
            &RefCell<BootstrapWaiterFace>,
            &BootstrapOwnerGuard,
            lazaret_core::identity::SessionId,
        ) -> Result<(), ColdStartError>,
    {
        let bootstrap_owner_session_id = bootstrap_owner.session_id;
        let waiters = RefCell::new(
            BootstrapWaiterFace::bind(
                self.configuration,
                self.generation.generation_id,
                self.invoking_uid,
            )
            .map_err(failure)?,
        );
        let store = Arc::clone(&self.store);
        let generation = self.generation.clone();
        let plan = self.take_plan()?;
        let mut lifecycle = coordinator_lifecycle(&store, plan).map_err(failure)?;
        let bootstrap = lifecycle.bootstrap_new_domain_while_owner_live_and_service(
            generation,
            bootstrap_owner,
            || owner_guard.is_live().unwrap_or(false),
            |lifecycle| {
                waiters
                    .borrow_mut()
                    .admit_pending(lifecycle)
                    .map_err(crate::bootstrap::LifecycleServiceError::service)
            },
            |lifecycle| {
                let mut waiters = waiters.borrow_mut();
                waiters
                    .admit_pending(lifecycle)
                    .map_err(crate::bootstrap::LifecycleServiceError::service)?;
                waiters
                    .withdraw()
                    .map_err(crate::bootstrap::LifecycleServiceError::service)
            },
        );
        match bootstrap {
            Ok(true) => {
                for session_id in waiters.borrow_mut().notify(BootstrapWaitOutcome::Published) {
                    lifecycle.disconnect_session(session_id).map_err(failure)?;
                }
            }
            Ok(false) => {
                let mut waiters = waiters.borrow_mut();
                let withdrawal = waiters.withdraw();
                let disconnected = waiters.notify(BootstrapWaitOutcome::Failed);
                withdrawal.map_err(failure)?;
                drop(waiters);
                for session_id in disconnected {
                    lifecycle.disconnect_session(session_id).map_err(failure)?;
                }
                return Err(ColdStartError(
                    "bootstrap owner disconnected before publication".into(),
                ));
            }
            Err(error) => {
                let mut waiters = waiters.borrow_mut();
                let _ = waiters.withdraw();
                let _ = waiters.notify(BootstrapWaitOutcome::Failed);
                return Err(failure(error));
            }
        }
        service(
            &Mutex::new(lifecycle),
            &waiters,
            owner_guard,
            bootstrap_owner_session_id,
        )
    }

    fn take_plan(&mut self) -> Result<BootstrapPlan<'_>, ColdStartError> {
        let interactive_executor = RunscInteractiveSessionExecutor::new(
            Arc::clone(&self.store),
            &self.generation_identity,
            self.container_id,
            current_process_identity().map_err(failure)?,
            self.sandbox_bundle.command(),
            self.runtime_root.clone(),
        )
        .map_err(failure)?;
        let prompt_transport = interactive_executor.prompt_transport();
        Ok(BootstrapPlan {
            store: Arc::clone(&self.store),
            catalog: self.catalog,
            configuration: self.configuration,
            generation_identity: self.generation_identity.clone(),
            prepared_artifact: self.prepared_artifact,
            state_anchor_layout: &self.state_anchor_layout,
            runtime_launch: self
                .runtime_launch
                .take()
                .ok_or_else(|| ColdStartError("cold start was already consumed".into()))?,
            sandbox_bundle: &self.sandbox_bundle,
            network_policy: &self.network_policy,
            network_probe: self.network_probe.clone(),
            reachability: &self.reachability,
            container_id: self.container_id,
            runtime_root: self.runtime_root.clone(),
            bundle_digest: self.bundle_digest,
            invoking_uid: self.invoking_uid,
            non_interactive_executor: Arc::new(
                RunscNonInteractiveExecutor::from_run_command(
                    self.sandbox_bundle.command(),
                    self.container_id,
                )
                .map_err(failure)?,
            ),
            interactive_executor: Arc::new(interactive_executor),
            prompt_transport,
            runtime_staging: &self.staging,
            git_routing: self.git_routing.as_ref().map(|routing| {
                crate::bootstrap::BootstrapGitRouting {
                    mountpoint: routing.mountpoint(),
                    host_root: routing.host_root(),
                    isolated_root: routing.isolated_root(),
                }
            }),
        })
    }
}

fn require_inputs(inputs: &ColdStartInputs<'_>) -> Result<(), ColdStartError> {
    if inputs.generation.domain_id != inputs.configuration.domain_id()
        || inputs.generation.configuration_fingerprint
            != inputs.configuration.configuration_fingerprint()
        || inputs.network_probe.domain_id != inputs.generation.domain_id
        || inputs.network_probe.generation_id != inputs.generation.generation_id
        || inputs.resolver_addresses.is_empty()
        || inputs.invoking_uid != rustix::process::getuid().as_raw()
    {
        return Err(ColdStartError("cold-start inputs disagree".into()));
    }
    Ok(())
}

mod git_routing;
mod runtime_staging;

use git_routing::GitRoutingLayout;
#[cfg(test)]
use git_routing::parse_global_excludes_path;
pub(crate) use runtime_staging::RuntimeStaging;
use runtime_staging::{
    FileIdentity, confined_resolve_flags, hex, host_path, open_or_create_private_directory,
    remove_staging_directory, require_private_file,
};

#[cfg(test)]
mod tests;