//! Shared diagnostics and structured logging models.
//!
//! Runtime crates can convert these values into `tracing` fields, JSON logs, or
//! user-facing status lines without each component inventing its own vocabulary.

use std::net::IpAddr;

use lanparty_proto::{EthernetFrame, EthernetSafetyDrop, MacAddr};

#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
#[serde(rename_all = "snake_case")]
pub enum FrameDirection {
    TapToRelay,
    RelayToTap,
    RemoteToLan,
    LanToRemote,
    RelayIngress,
    RelayEgress,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
#[serde(rename_all = "snake_case")]
pub enum FrameAction {
    Forwarded,
    Dropped,
    Filtered,
    RateLimited,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
#[serde(rename_all = "snake_case")]
pub enum DropReason {
    Malformed,
    JumboFrame,
    InvalidSourceMac,
    UnauthorizedSourceMac,
    DuplicateMac,
    ControlPlaneEtherType,
    DhcpServerReply,
    Ipv6RouterAdvertisement,
    Ipv6Fragment,
    VlanTaggedFrame,
    TapMtuExceeded,
    DatagramBudget,
    UnknownDestination,
    RateLimit,
}

impl From<EthernetSafetyDrop> for DropReason {
    fn from(value: EthernetSafetyDrop) -> Self {
        match value {
            EthernetSafetyDrop::InvalidSourceMac => Self::InvalidSourceMac,
            EthernetSafetyDrop::JumboFrame => Self::JumboFrame,
            EthernetSafetyDrop::ControlPlaneEtherType => Self::ControlPlaneEtherType,
            EthernetSafetyDrop::VlanTaggedFrame => Self::VlanTaggedFrame,
            EthernetSafetyDrop::DhcpServerReply => Self::DhcpServerReply,
            EthernetSafetyDrop::Ipv6RouterAdvertisement => Self::Ipv6RouterAdvertisement,
            EthernetSafetyDrop::Ipv6Fragment => Self::Ipv6Fragment,
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
pub struct FrameLog {
    direction: FrameDirection,
    source_mac: Option<MacAddr>,
    destination_mac: Option<MacAddr>,
    ethertype_or_len: Option<u16>,
    frame_len: usize,
    peer_id: Option<u32>,
    action: FrameAction,
    drop_reason: Option<DropReason>,
}

impl FrameLog {
    #[must_use]
    pub fn from_ethernet(
        direction: FrameDirection,
        peer_id: Option<u32>,
        action: FrameAction,
        drop_reason: Option<DropReason>,
        frame: EthernetFrame<'_>,
    ) -> Self {
        Self {
            direction,
            source_mac: Some(frame.source()),
            destination_mac: Some(frame.destination()),
            ethertype_or_len: Some(frame.ethertype_or_len()),
            frame_len: frame.len(),
            peer_id,
            action,
            drop_reason,
        }
    }

    #[must_use]
    pub const fn malformed(
        direction: FrameDirection,
        peer_id: Option<u32>,
        frame_len: usize,
    ) -> Self {
        Self {
            direction,
            source_mac: None,
            destination_mac: None,
            ethertype_or_len: None,
            frame_len,
            peer_id,
            action: FrameAction::Dropped,
            drop_reason: Some(DropReason::Malformed),
        }
    }

    #[must_use]
    pub const fn direction(&self) -> FrameDirection {
        self.direction
    }

    #[must_use]
    pub const fn source_mac(&self) -> Option<MacAddr> {
        self.source_mac
    }

    #[must_use]
    pub const fn destination_mac(&self) -> Option<MacAddr> {
        self.destination_mac
    }

    #[must_use]
    pub const fn ethertype_or_len(&self) -> Option<u16> {
        self.ethertype_or_len
    }

    #[must_use]
    pub const fn frame_len(&self) -> usize {
        self.frame_len
    }

    #[must_use]
    pub const fn peer_id(&self) -> Option<u32> {
        self.peer_id
    }

    #[must_use]
    pub const fn action(&self) -> FrameAction {
        self.action
    }

    #[must_use]
    pub const fn drop_reason(&self) -> Option<DropReason> {
        self.drop_reason
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Default, serde::Deserialize, serde::Serialize)]
pub struct TunnelStats {
    ethernet_frames_tx: u64,
    ethernet_frames_rx: u64,
    #[serde(default)]
    broadcast_frames_tx: u64,
    #[serde(default)]
    broadcast_frames_rx: u64,
    datagrams_tx: u64,
    datagrams_rx: u64,
    dropped_frames: u64,
    malformed_frames: u64,
}

impl TunnelStats {
    #[must_use]
    pub const fn new(
        ethernet_frames_tx: u64,
        ethernet_frames_rx: u64,
        datagrams_tx: u64,
        datagrams_rx: u64,
        dropped_frames: u64,
        malformed_frames: u64,
    ) -> Self {
        Self {
            ethernet_frames_tx,
            ethernet_frames_rx,
            broadcast_frames_tx: 0,
            broadcast_frames_rx: 0,
            datagrams_tx,
            datagrams_rx,
            dropped_frames,
            malformed_frames,
        }
    }

    #[must_use]
    pub const fn with_broadcast_frames(
        mut self,
        broadcast_frames_tx: u64,
        broadcast_frames_rx: u64,
    ) -> Self {
        self.broadcast_frames_tx = broadcast_frames_tx;
        self.broadcast_frames_rx = broadcast_frames_rx;
        self
    }

    #[must_use]
    pub const fn ethernet_frames_tx(&self) -> u64 {
        self.ethernet_frames_tx
    }

    #[must_use]
    pub const fn ethernet_frames_rx(&self) -> u64 {
        self.ethernet_frames_rx
    }

    #[must_use]
    pub const fn broadcast_frames_tx(&self) -> u64 {
        self.broadcast_frames_tx
    }

    #[must_use]
    pub const fn broadcast_frames_rx(&self) -> u64 {
        self.broadcast_frames_rx
    }

    #[must_use]
    pub const fn datagrams_tx(&self) -> u64 {
        self.datagrams_tx
    }

    #[must_use]
    pub const fn datagrams_rx(&self) -> u64 {
        self.datagrams_rx
    }

    #[must_use]
    pub const fn dropped_frames(&self) -> u64 {
        self.dropped_frames
    }

    #[must_use]
    pub const fn malformed_frames(&self) -> u64 {
        self.malformed_frames
    }
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
pub struct RelayDiagnostics {
    reachable: bool,
    route_pinned: bool,
    gateway_connected: bool,
}

impl RelayDiagnostics {
    #[must_use]
    pub const fn new(reachable: bool, route_pinned: bool, gateway_connected: bool) -> Self {
        Self {
            reachable,
            route_pinned,
            gateway_connected,
        }
    }

    #[must_use]
    pub const fn reachable(&self) -> bool {
        self.reachable
    }

    #[must_use]
    pub const fn route_pinned(&self) -> bool {
        self.route_pinned
    }

    #[must_use]
    pub const fn gateway_connected(&self) -> bool {
        self.gateway_connected
    }
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
pub struct QuicDiagnostics {
    datagram_supported: bool,
    max_datagram_size: Option<u16>,
    #[serde(default)]
    relay_rtt_ms: Option<u64>,
}

impl QuicDiagnostics {
    #[must_use]
    pub const fn new(datagram_supported: bool, max_datagram_size: Option<u16>) -> Self {
        Self {
            datagram_supported,
            max_datagram_size,
            relay_rtt_ms: None,
        }
    }

    #[must_use]
    pub const fn with_relay_rtt_ms(mut self, relay_rtt_ms: Option<u64>) -> Self {
        self.relay_rtt_ms = relay_rtt_ms;
        self
    }

    #[must_use]
    pub const fn datagram_supported(&self) -> bool {
        self.datagram_supported
    }

    #[must_use]
    pub const fn max_datagram_size(&self) -> Option<u16> {
        self.max_datagram_size
    }

    #[must_use]
    pub const fn relay_rtt_ms(&self) -> Option<u64> {
        self.relay_rtt_ms
    }
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
pub struct TapDiagnostics {
    adapter_found: bool,
    mac: Option<MacAddr>,
    mtu: Option<u16>,
    ip: Option<IpAddr>,
}

impl TapDiagnostics {
    #[must_use]
    pub const fn new(
        adapter_found: bool,
        mac: Option<MacAddr>,
        mtu: Option<u16>,
        ip: Option<IpAddr>,
    ) -> Self {
        Self {
            adapter_found,
            mac,
            mtu,
            ip,
        }
    }

    #[must_use]
    pub const fn adapter_found(&self) -> bool {
        self.adapter_found
    }

    #[must_use]
    pub const fn mac(&self) -> Option<MacAddr> {
        self.mac
    }

    #[must_use]
    pub const fn mtu(&self) -> Option<u16> {
        self.mtu
    }

    #[must_use]
    pub const fn ip(&self) -> Option<IpAddr> {
        self.ip
    }
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
pub struct ClientDiagnostics {
    relay: RelayDiagnostics,
    quic: QuicDiagnostics,
    tap: TapDiagnostics,
    stats: TunnelStats,
}

impl ClientDiagnostics {
    #[must_use]
    pub const fn new(
        relay: RelayDiagnostics,
        quic: QuicDiagnostics,
        tap: TapDiagnostics,
        stats: TunnelStats,
    ) -> Self {
        Self {
            relay,
            quic,
            tap,
            stats,
        }
    }

    #[must_use]
    pub const fn relay(&self) -> &RelayDiagnostics {
        &self.relay
    }

    #[must_use]
    pub const fn quic(&self) -> &QuicDiagnostics {
        &self.quic
    }

    #[must_use]
    pub const fn tap(&self) -> &TapDiagnostics {
        &self.tap
    }

    #[must_use]
    pub const fn stats(&self) -> &TunnelStats {
        &self.stats
    }

    #[must_use]
    pub fn user_diagnostics(&self) -> Vec<UserDiagnostic> {
        let mut diagnostics = Vec::new();

        diagnostics.push(if self.relay.reachable() {
            UserDiagnostic::new(UserDiagnosticLevel::Info, "Connected to relay")
        } else {
            UserDiagnostic::new(UserDiagnosticLevel::Error, "Relay not reachable")
        });

        diagnostics.push(if self.relay.gateway_connected() {
            UserDiagnostic::new(UserDiagnosticLevel::Info, "Connected to LAN gateway")
        } else {
            UserDiagnostic::new(UserDiagnosticLevel::Warning, "Waiting for LAN gateway")
        });

        if !self.relay.route_pinned() {
            diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Warning,
                "Relay route not pinned",
            ));
        }

        if !self.tap.adapter_found() {
            diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Error,
                "TAP adapter not found",
            ));
        } else if self.tap.ip().is_none() {
            diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Warning,
                "Waiting for TAP IP",
            ));
        }

        if let Some(diagnostic) = tap_ip_user_diagnostic(self.tap.ip()) {
            diagnostics.push(diagnostic);
        }

        if let Some(rtt_ms) = self.quic.relay_rtt_ms() {
            diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Info,
                format!("Relay RTT: {rtt_ms} ms"),
            ));
        }

        match (
            self.stats.broadcast_frames_tx() > 0,
            self.stats.broadcast_frames_rx() > 0,
        ) {
            (true, true) => diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Info,
                "Broadcast traffic flowing",
            )),
            (true, false) => diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Warning,
                "Broadcast sent toward LAN; waiting for LAN broadcast reply",
            )),
            (false, true) => diagnostics.push(UserDiagnostic::new(
                UserDiagnosticLevel::Info,
                "LAN broadcast received",
            )),
            (false, false) => {}
        }

        diagnostics
    }
}

fn tap_ip_user_diagnostic(ip: Option<IpAddr>) -> Option<UserDiagnostic> {
    match ip {
        Some(IpAddr::V4(ip)) if ip.is_link_local() => Some(UserDiagnostic::new(
            UserDiagnosticLevel::Warning,
            format!("TAP has link-local IP {ip}; waiting for LAN DHCP"),
        )),
        Some(IpAddr::V4(ip)) => Some(UserDiagnostic::new(
            UserDiagnosticLevel::Info,
            format!("DHCP received: {ip}"),
        )),
        Some(ip) => Some(UserDiagnostic::new(
            UserDiagnosticLevel::Info,
            format!("TAP IP detected: {ip}"),
        )),
        None => None,
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
#[serde(rename_all = "snake_case")]
pub enum UserDiagnosticLevel {
    Info,
    Warning,
    Error,
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
pub struct UserDiagnostic {
    level: UserDiagnosticLevel,
    message: String,
}

impl UserDiagnostic {
    #[must_use]
    pub fn new(level: UserDiagnosticLevel, message: impl Into<String>) -> Self {
        Self {
            level,
            message: message.into(),
        }
    }

    #[must_use]
    pub const fn level(&self) -> UserDiagnosticLevel {
        self.level
    }

    #[must_use]
    pub fn message(&self) -> &str {
        &self.message
    }
}

#[derive(Debug, Clone, PartialEq, Eq, serde::Deserialize, serde::Serialize)]
#[serde(tag = "type", content = "payload", rename_all = "snake_case")]
pub enum DiagnosticEvent {
    Frame(FrameLog),
    Client(ClientDiagnostics),
    Stats(TunnelStats),
    User(UserDiagnostic),
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn builds_frame_log_from_ethernet_header() {
        let bytes = [
            0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x02, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0x08, 0x06,
        ];
        let frame = EthernetFrame::parse(&bytes).unwrap();

        let log = FrameLog::from_ethernet(
            FrameDirection::RemoteToLan,
            Some(7),
            FrameAction::Forwarded,
            None,
            frame,
        );

        assert_eq!(log.direction(), FrameDirection::RemoteToLan);
        assert_eq!(
            log.source_mac(),
            Some(MacAddr::new([0x02, 0xaa, 0xbb, 0xcc, 0xdd, 0xee]))
        );
        assert_eq!(log.destination_mac(), Some(MacAddr::BROADCAST));
        assert_eq!(log.ethertype_or_len(), Some(0x0806));
        assert_eq!(log.frame_len(), bytes.len());
        assert_eq!(log.peer_id(), Some(7));
        assert_eq!(log.action(), FrameAction::Forwarded);
        assert_eq!(log.drop_reason(), None);
    }

    #[test]
    fn builds_malformed_frame_log_without_header_fields() {
        let log = FrameLog::malformed(FrameDirection::RelayIngress, Some(3), 8);

        assert_eq!(log.direction(), FrameDirection::RelayIngress);
        assert_eq!(log.source_mac(), None);
        assert_eq!(log.destination_mac(), None);
        assert_eq!(log.ethertype_or_len(), None);
        assert_eq!(log.frame_len(), 8);
        assert_eq!(log.peer_id(), Some(3));
        assert_eq!(log.action(), FrameAction::Dropped);
        assert_eq!(log.drop_reason(), Some(DropReason::Malformed));
    }

    #[test]
    fn exposes_client_diagnostics() {
        let mac = MacAddr::new([0x02, 1, 2, 3, 4, 5]);
        let stats = TunnelStats::new(1, 2, 3, 4, 5, 6).with_broadcast_frames(7, 8);
        let diagnostics = ClientDiagnostics::new(
            RelayDiagnostics::new(true, true, true),
            QuicDiagnostics::new(true, Some(1400)),
            TapDiagnostics::new(
                true,
                Some(mac),
                Some(1200),
                Some("10.73.42.51".parse().unwrap()),
            ),
            stats,
        );

        assert!(diagnostics.relay().reachable());
        assert!(diagnostics.relay().route_pinned());
        assert!(diagnostics.relay().gateway_connected());
        assert!(diagnostics.quic().datagram_supported());
        assert_eq!(diagnostics.quic().max_datagram_size(), Some(1400));
        assert_eq!(diagnostics.quic().relay_rtt_ms(), None);
        assert!(diagnostics.tap().adapter_found());
        assert_eq!(diagnostics.tap().mac(), Some(mac));
        assert_eq!(diagnostics.tap().mtu(), Some(1200));
        assert_eq!(diagnostics.tap().ip().unwrap().to_string(), "10.73.42.51");
        assert_eq!(diagnostics.stats().broadcast_frames_tx(), 7);
        assert_eq!(diagnostics.stats().broadcast_frames_rx(), 8);
        assert_eq!(diagnostics.stats().dropped_frames(), 5);
    }

    #[test]
    fn defaults_missing_broadcast_stats_to_zero() {
        let stats: TunnelStats = serde_json::from_str(
            r#"{
                "ethernet_frames_tx": 1,
                "ethernet_frames_rx": 2,
                "datagrams_tx": 3,
                "datagrams_rx": 4,
                "dropped_frames": 5,
                "malformed_frames": 6
            }"#,
        )
        .unwrap();

        assert_eq!(stats.broadcast_frames_tx(), 0);
        assert_eq!(stats.broadcast_frames_rx(), 0);
    }

    #[test]
    fn defaults_missing_relay_rtt_to_unknown() {
        let diagnostics: QuicDiagnostics = serde_json::from_str(
            r#"{
                "datagram_supported": true,
                "max_datagram_size": 1400
            }"#,
        )
        .unwrap();

        assert_eq!(diagnostics.relay_rtt_ms(), None);
    }

    #[test]
    fn derives_user_diagnostics_from_client_snapshot() {
        let diagnostics = ClientDiagnostics::new(
            RelayDiagnostics::new(true, true, true),
            QuicDiagnostics::new(true, Some(1400)).with_relay_rtt_ms(Some(23)),
            TapDiagnostics::new(
                true,
                Some(MacAddr::new([0x02, 1, 2, 3, 4, 5])),
                Some(1200),
                Some("10.73.42.51".parse().unwrap()),
            ),
            TunnelStats::new(1, 2, 3, 4, 5, 6).with_broadcast_frames(7, 8),
        );

        let user_diagnostics = diagnostics.user_diagnostics();
        let messages: Vec<_> = user_diagnostics
            .iter()
            .map(UserDiagnostic::message)
            .collect();

        assert_eq!(
            messages,
            [
                "Connected to relay",
                "Connected to LAN gateway",
                "DHCP received: 10.73.42.51",
                "Relay RTT: 23 ms",
                "Broadcast traffic flowing",
            ]
        );
        assert!(
            user_diagnostics
                .iter()
                .all(|diagnostic| diagnostic.level() == UserDiagnosticLevel::Info)
        );
    }

    #[test]
    fn reports_user_diagnostic_warnings_for_missing_connections() {
        let diagnostics = ClientDiagnostics::new(
            RelayDiagnostics::new(false, false, false),
            QuicDiagnostics::new(false, None),
            TapDiagnostics::new(false, None, None, None),
            TunnelStats::default(),
        );

        let user_diagnostics = diagnostics.user_diagnostics();

        assert_eq!(
            user_diagnostics
                .iter()
                .map(UserDiagnostic::message)
                .collect::<Vec<_>>(),
            [
                "Relay not reachable",
                "Waiting for LAN gateway",
                "Relay route not pinned",
                "TAP adapter not found",
            ]
        );
        assert_eq!(user_diagnostics[0].level(), UserDiagnosticLevel::Error);
        assert_eq!(user_diagnostics[1].level(), UserDiagnosticLevel::Warning);
        assert_eq!(user_diagnostics[2].level(), UserDiagnosticLevel::Warning);
        assert_eq!(user_diagnostics[3].level(), UserDiagnosticLevel::Error);
    }

    #[test]
    fn reports_waiting_for_tap_ip_when_adapter_has_no_address() {
        let diagnostics = ClientDiagnostics::new(
            RelayDiagnostics::new(true, true, true),
            QuicDiagnostics::new(true, Some(1400)),
            TapDiagnostics::new(
                true,
                Some(MacAddr::new([0x02, 1, 2, 3, 4, 5])),
                Some(1200),
                None,
            ),
            TunnelStats::default(),
        );

        let user_diagnostics = diagnostics.user_diagnostics();

        assert_eq!(
            user_diagnostics
                .iter()
                .map(UserDiagnostic::message)
                .collect::<Vec<_>>(),
            [
                "Connected to relay",
                "Connected to LAN gateway",
                "Waiting for TAP IP",
            ]
        );
        assert_eq!(user_diagnostics[2].level(), UserDiagnosticLevel::Warning);
    }

    #[test]
    fn distinguishes_one_way_broadcast_diagnostics() {
        let mut diagnostics = ClientDiagnostics::new(
            RelayDiagnostics::new(true, true, true),
            QuicDiagnostics::new(true, Some(1400)),
            TapDiagnostics::new(
                true,
                Some(MacAddr::new([0x02, 1, 2, 3, 4, 5])),
                Some(1200),
                None,
            ),
            TunnelStats::default().with_broadcast_frames(1, 0),
        );
        let broadcast = diagnostics
            .user_diagnostics()
            .into_iter()
            .find(|diagnostic| diagnostic.message().contains("Broadcast"))
            .expect("outbound broadcast should produce a diagnostic");
        assert_eq!(broadcast.level(), UserDiagnosticLevel::Warning);
        assert_eq!(
            broadcast.message(),
            "Broadcast sent toward LAN; waiting for LAN broadcast reply"
        );

        diagnostics = ClientDiagnostics::new(
            RelayDiagnostics::new(true, true, true),
            QuicDiagnostics::new(true, Some(1400)),
            TapDiagnostics::new(
                true,
                Some(MacAddr::new([0x02, 1, 2, 3, 4, 5])),
                Some(1200),
                None,
            ),
            TunnelStats::default().with_broadcast_frames(0, 1),
        );
        let broadcast = diagnostics
            .user_diagnostics()
            .into_iter()
            .find(|diagnostic| diagnostic.message().contains("broadcast"))
            .expect("inbound broadcast should produce a diagnostic");
        assert_eq!(broadcast.level(), UserDiagnosticLevel::Info);
        assert_eq!(broadcast.message(), "LAN broadcast received");
    }

    #[test]
    fn reports_link_local_tap_ipv4_as_waiting_for_lan_dhcp() {
        let diagnostic = tap_ip_user_diagnostic(Some("169.254.10.20".parse().unwrap())).unwrap();

        assert_eq!(diagnostic.level(), UserDiagnosticLevel::Warning);
        assert_eq!(
            diagnostic.message(),
            "TAP has link-local IP 169.254.10.20; waiting for LAN DHCP"
        );
    }

    #[test]
    fn reports_ipv6_link_local_tap_ip_without_calling_it_dhcp() {
        let diagnostic = tap_ip_user_diagnostic(Some("fe80::1".parse().unwrap())).unwrap();

        assert_eq!(diagnostic.level(), UserDiagnosticLevel::Info);
        assert_eq!(diagnostic.message(), "TAP IP detected: fe80::1");
    }
}