use lazaret_core::identity::{
    GenerationId, MountIdentity, NamespaceIdentity, PidfsProcessIdentityV1,
};
use lazaret_core::records::{
    Participant, ParticipantOwnership, ParticipantRole, PersistedHostProcessOwnership,
};
use lazaret_linux::process::{PidfsRecoveryMatch, match_recovery_process};

use crate::state_anchor::RuntimeOwnersAbsent;

#[derive(Clone, Copy, Debug, Default, Eq, PartialEq)]
pub struct RuntimeRecoveryOwnership {
    pub host_coordinator: Option<PidfsProcessIdentityV1>,
    pub runtime_supervisor: Option<PidfsProcessIdentityV1>,
    pub attached_runsc: Option<PidfsProcessIdentityV1>,
    pub connectivity_helper: Option<PidfsProcessIdentityV1>,
    pub state_anchor_daemon: Option<PidfsProcessIdentityV1>,
    pub git_routing_daemon: Option<PidfsProcessIdentityV1>,
    pub state_anchor_user_namespace: Option<NamespaceIdentity>,
    pub state_anchor_mount_namespace: Option<NamespaceIdentity>,
    pub state_anchor_mount: Option<MountIdentity>,
}

/// Extracts one generation's exact process and private-mount recovery authority.
///
/// # Errors
/// Refuses unequal copies of the constitutive HC or RS identities, and incomplete State Anchor
/// namespace/mount evidence. Staged identities remain cleanup authority.
pub fn runtime_recovery_ownership(
    participants: &[Participant],
    generation_id: GenerationId,
) -> Result<RuntimeRecoveryOwnership, &'static str> {
    let mut result = RuntimeRecoveryOwnership::default();
    for participant in participants
        .iter()
        .filter(|participant| participant.generation_id() == generation_id)
    {
        let Some(ownership) = participant.ownership() else {
            continue;
        };
        match ownership {
            ParticipantOwnership::Sandbox(sandbox) => {
                merge_process(
                    &mut result.host_coordinator,
                    &sandbox.host_coordinator,
                    "Sandbox HC identity mismatch",
                )?;
                merge_process(
                    &mut result.runtime_supervisor,
                    &sandbox.runtime_supervisor,
                    "Sandbox RS identity mismatch",
                )?;
                merge_process(
                    &mut result.attached_runsc,
                    &sandbox.attached_runsc,
                    "attached runsc identity mismatch",
                )?;
            }
            ParticipantOwnership::Network(network) => merge_process(
                &mut result.runtime_supervisor,
                &network.runtime_supervisor,
                "Network RS identity mismatch",
            )?,
            ParticipantOwnership::Helper(helper) => {
                merge_process(
                    &mut result.connectivity_helper,
                    &helper.connectivity_helper,
                    "connectivity-helper identity mismatch",
                )?;
                merge_process(
                    &mut result.runtime_supervisor,
                    &helper.runtime_supervisor,
                    "Helper RS identity mismatch",
                )?;
            }
            ParticipantOwnership::StateAnchor(anchor) => {
                merge_process(
                    &mut result.state_anchor_daemon,
                    &anchor.daemon,
                    "State Anchor daemon identity mismatch",
                )?;
                let evidence = (anchor.user_namespace, anchor.mount_namespace, anchor.mount);
                if evidence == (None, None, None) {
                    continue;
                }
                let (Some(user), Some(mount_namespace), Some(mount)) = evidence else {
                    return Err("State Anchor recovery evidence is incomplete");
                };
                merge_value(
                    &mut result.state_anchor_user_namespace,
                    user,
                    "State Anchor user namespace mismatch",
                )?;
                merge_value(
                    &mut result.state_anchor_mount_namespace,
                    mount_namespace,
                    "State Anchor mount namespace mismatch",
                )?;
                merge_value(
                    &mut result.state_anchor_mount,
                    mount,
                    "State Anchor mount identity mismatch",
                )?;
            }
            ParticipantOwnership::GitRouting(routing) => merge_process(
                &mut result.git_routing_daemon,
                &routing.daemon,
                "Git-routing daemon identity mismatch",
            )?,
            ParticipantOwnership::PreparedLower(_) | ParticipantOwnership::Publication(_) => {}
        }
    }
    Ok(result)
}

fn merge_process(
    target: &mut Option<PidfsProcessIdentityV1>,
    observed: &PersistedHostProcessOwnership,
    mismatch: &'static str,
) -> Result<(), &'static str> {
    let Ok(observed) = observed.authoritative_pidfs() else {
        return Ok(());
    };
    merge_value(target, *observed, mismatch)
}

fn merge_value<T: Copy + Eq>(
    target: &mut Option<T>,
    observed: T,
    mismatch: &'static str,
) -> Result<(), &'static str> {
    match target {
        None => *target = Some(observed),
        Some(current) if *current == observed => {}
        Some(_) => return Err(mismatch),
    }
    Ok(())
}

#[must_use]
pub fn recovery_role_order() -> [ParticipantRole; 7] {
    [
        ParticipantRole::Publication,
        ParticipantRole::Sandbox,
        ParticipantRole::Helper,
        ParticipantRole::Network,
        ParticipantRole::GitRouting,
        ParticipantRole::StateAnchor,
        ParticipantRole::PreparedLower,
    ]
}

/// Proves the constitutive RS and attached runsc are absent before private-mount reconciliation.
///
/// # Errors
/// Refuses a live or stopped exact authority and every unreadable or ambiguous observation.
pub fn prove_runtime_owners_absent(
    generation_id: GenerationId,
    ownership: &RuntimeRecoveryOwnership,
) -> Result<RuntimeOwnersAbsent, std::io::Error> {
    for identity in [ownership.attached_runsc, ownership.runtime_supervisor]
        .into_iter()
        .flatten()
    {
        match match_recovery_process(identity) {
            Ok(PidfsRecoveryMatch::BootMismatch) => {}
            Ok(PidfsRecoveryMatch::Matched(process)) if process.has_exited()? => {}
            Ok(PidfsRecoveryMatch::Matched(_)) => {
                return Err(std::io::Error::other(
                    "constitutive runtime authority remains present",
                ));
            }
            Err(error) if error.raw_os_error() == Some(rustix::io::Errno::SRCH.raw_os_error()) => {}
            Err(error) => return Err(error),
        }
    }
    Ok(RuntimeOwnersAbsent::for_generation(generation_id))
}

#[cfg(test)]
mod tests {
    use lazaret_core::identity::{
        BootId, BundleDigest, ContainerId, DeviceId, HostPath, HostPidLocator, MountId,
        PidfsDeviceId, PidfsInodeId, PidfsProcessAuthorityV1, ProcessStartTimeTicks,
    };
    use lazaret_core::records::{
        HelperOwnership, ParticipantState, SandboxOwnership, StateAnchorOwnership,
    };

    use super::*;

    fn process(value: u64) -> PidfsProcessIdentityV1 {
        PidfsProcessIdentityV1::new(
            PidfsProcessAuthorityV1 {
                boot_id: BootId::new([1; 16]),
                pidfs_st_dev: PidfsDeviceId::new(value),
                pidfs_st_ino: PidfsInodeId::new(value),
            },
            HostPidLocator::new(u32::try_from(value).unwrap()),
            ProcessStartTimeTicks::new(value),
        )
    }

    fn participant(role: ParticipantRole, ownership: ParticipantOwnership) -> Participant {
        Participant::snapshot(
            GenerationId::new(1),
            role,
            ParticipantState::Intent,
            Some(ownership),
        )
        .unwrap()
    }

    #[test]
    fn inventory_accepts_staged_cleanup_authority_and_rejects_cross_role_rs_mismatch() {
        let rs = process(2);
        let sandbox = participant(
            ParticipantRole::Sandbox,
            ParticipantOwnership::Sandbox(SandboxOwnership {
                container_id: Some(ContainerId::new([3; 32])),
                runtime_root: Some(HostPath::new(b"/runtime".to_vec())),
                bundle_digest: Some(BundleDigest::new([4; 32])),
                host_coordinator: PersistedHostProcessOwnership::committed(process(1)),
                runtime_supervisor: PersistedHostProcessOwnership::staged(rs),
                attached_runsc: PersistedHostProcessOwnership::staged(process(3)),
            }),
        );
        let helper = |runtime_supervisor| {
            participant(
                ParticipantRole::Helper,
                ParticipantOwnership::Helper(HelperOwnership {
                    network_sidecar_id: None,
                    connectivity_helper: PersistedHostProcessOwnership::staged(process(4)),
                    runtime_supervisor: PersistedHostProcessOwnership::committed(
                        runtime_supervisor,
                    ),
                }),
            )
        };
        let inventory =
            runtime_recovery_ownership(&[sandbox.clone(), helper(rs)], GenerationId::new(1))
                .unwrap();
        assert_eq!(inventory.runtime_supervisor, Some(rs));
        assert_eq!(inventory.attached_runsc, Some(process(3)));
        assert_eq!(inventory.connectivity_helper, Some(process(4)));
        assert!(
            runtime_recovery_ownership(&[sandbox, helper(process(99))], GenerationId::new(1),)
                .is_err()
        );
    }

    #[test]
    fn inventory_requires_complete_private_mount_evidence() {
        let incomplete = participant(
            ParticipantRole::StateAnchor,
            ParticipantOwnership::StateAnchor(StateAnchorOwnership {
                lower_artifact_id: None,
                upper_path: Some(HostPath::new(b"upper".to_vec())),
                work_path: None,
                merged_path: None,
                daemon: PersistedHostProcessOwnership::staged(process(5)),
                user_namespace: Some(NamespaceIdentity {
                    device: DeviceId::new(6),
                    inode: lazaret_core::identity::InodeId::new(7),
                }),
                mount_namespace: None,
                mount: None,
            }),
        );
        assert!(runtime_recovery_ownership(&[incomplete], GenerationId::new(1)).is_err());

        let complete = participant(
            ParticipantRole::StateAnchor,
            ParticipantOwnership::StateAnchor(StateAnchorOwnership {
                lower_artifact_id: None,
                upper_path: Some(HostPath::new(b"upper".to_vec())),
                work_path: None,
                merged_path: None,
                daemon: PersistedHostProcessOwnership::staged(process(5)),
                user_namespace: Some(NamespaceIdentity {
                    device: DeviceId::new(6),
                    inode: lazaret_core::identity::InodeId::new(7),
                }),
                mount_namespace: Some(NamespaceIdentity {
                    device: DeviceId::new(8),
                    inode: lazaret_core::identity::InodeId::new(9),
                }),
                mount: Some(MountIdentity {
                    mount_id: MountId::new(10),
                    device: DeviceId::new(11),
                    inode: lazaret_core::identity::InodeId::new(12),
                }),
            }),
        );
        assert!(runtime_recovery_ownership(&[complete], GenerationId::new(1)).is_ok());
    }
}