//! Shared OpenFUT destination configuration.
//!
//! This crate is the **single source of truth** for where FIFA's intercepted
//! EA traffic is redirected. It is consumed by both the launcher (which writes
//! `openfut.cfg`) and `openfut_hook.dll` (which reads it and rewrites sockets).
//!
//! Design rules enforced here:
//!   * There is exactly ONE configured OpenFUT destination (host + ports).
//!   * Missing/invalid configuration is a hard error — it NEVER silently
//!     degrades to `127.0.0.1`/localhost. Loopback is only ever used if the
//!     user explicitly configures it.
//!   * The address/port -> WinSock representation helpers live here and are
//!     unit-tested on the host, so the byte-order logic the socket hooks depend
//!     on is verified without needing WinSock or FIFA.
//!
//! ## EA source ports vs OpenFUT destination ports
//!
//! FIFA connects to a handful of EA endpoints on fixed ports. Those source
//! ports are *signatures* used to recognise traffic that must be intercepted —
//! they are hardcoded on purpose (see [`ea_ports`]). Each recognised EA source
//! port maps to an OpenFUT *destination* port, which comes from configuration
//! ([`OpenFutPorts`]). Source port = fixed EA signature; destination port =
//! configurable OpenFUT service.

use std::fmt;
use std::net::{Ipv4Addr, ToSocketAddrs};
use std::str::FromStr;

/// EA source ports FIFA dials. These are fixed EA endpoint signatures used to
/// recognise traffic for interception — NOT OpenFUT configuration. Do not make
/// these configurable; changing them would stop us recognising EA traffic.
pub mod ea_ports {
    /// EA HTTPS (UTAS / EAWebKit / footapi) — the game dials EA hosts on 443.
    pub const HTTPS: u16 = 443;
    /// EA Blaze redirector (gosredirector) source port.
    pub const BLAZE_REDIRECTOR: u16 = 10041;
    /// FIFA 17's `winter15.gosredirector.ea.com` endpoint source port. This is
    /// an observed, fixed vendor-port signature; it maps to the same configured
    /// OpenFUT redirector destination as the newer 10041 endpoint.
    pub const FIFA17_BLAZE_REDIRECTOR: u16 = 42230;
    /// EA Blaze main server source port.
    pub const BLAZE_MAIN: u16 = 42127;
}

/// Default OpenFUT *destination* ports, derived from the current OpenFUT server
/// implementation (bridge listens on 8443 for HTTPS; Blaze services keep their
/// native ports). The launcher may pre-populate these; the user may change them
/// without recompiling anything.
pub mod default_ports {
    /// OpenFUT bridge HTTPS listener (EA :443 is redirected here).
    pub const HTTPS: u16 = 8443;
    /// OpenFUT FIFA 17 Blaze redirector listener.
    pub const BLAZE_REDIRECTOR: u16 = 42127;
    /// OpenFUT FIFA 17 Blaze main listener.
    pub const BLAZE_MAIN: u16 = 42130;
}

/// OpenFUT destination ports. Each field is where an intercepted EA source port
/// is redirected. Not collapsed into one port: OpenFUT runs distinct services
/// (bridge HTTPS + two Blaze listeners) that FIFA reaches on distinct ports.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct OpenFutPorts {
    /// Destination for EA :443 traffic (bridge HTTPS).
    pub https: u16,
    /// Destination for EA :10041 traffic (Blaze redirector).
    pub blaze_redirector: u16,
    /// Destination for EA :42127 traffic (Blaze main).
    pub blaze_main: u16,
}

impl Default for OpenFutPorts {
    fn default() -> Self {
        Self {
            https: default_ports::HTTPS,
            blaze_redirector: default_ports::BLAZE_REDIRECTOR,
            blaze_main: default_ports::BLAZE_MAIN,
        }
    }
}

impl OpenFutPorts {
    /// Map a recognised EA *source* port to its OpenFUT *destination* port.
    /// Returns `None` for ports we don't intercept (the socket hook then leaves
    /// the connection untouched).
    pub fn map_source_port(&self, ea_source_port: u16) -> Option<u16> {
        match ea_source_port {
            ea_ports::HTTPS => Some(self.https),
            ea_ports::BLAZE_REDIRECTOR | ea_ports::FIFA17_BLAZE_REDIRECTOR => {
                Some(self.blaze_redirector)
            }
            ea_ports::BLAZE_MAIN => Some(self.blaze_main),
            _ => None,
        }
    }
}

/// The parsed OpenFUT server configuration: what host to redirect EA traffic to
/// and which destination ports to use. `host` may be an IPv4 literal or a
/// hostname; resolution to a concrete [`Ipv4Addr`] happens in [`Self::resolve`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ServerConfig {
    /// User-configured OpenFUT server host (IPv4 literal or hostname). Never
    /// defaulted to loopback — an empty host is a [`ConfigError::ServerMissing`].
    pub host: String,
    pub ports: OpenFutPorts,
}

/// A [`ServerConfig`] whose host has been resolved to a concrete IPv4 address.
/// This is what the socket hooks consume — all three interception layers share
/// exactly this resolved destination.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ResolvedServer {
    /// The concrete IPv4 the EA connection's destination is rewritten to.
    pub redirect_ip: Ipv4Addr,
    pub ports: OpenFutPorts,
}

/// Errors loading/validating OpenFUT server configuration. Every one of these
/// must BLOCK operation — none of them may fall back to loopback.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ConfigError {
    /// No config file present (e.g. `openfut.cfg` missing).
    ConfigMissing,
    /// Config present but no server host set.
    ServerMissing,
    /// Host could not be parsed/resolved to an IPv4 address.
    InvalidAddress(String),
    /// A port value was not a valid `u16` / was zero.
    InvalidPort(String),
    /// Config bytes were structurally unparseable.
    MalformedConfig(String),
}

impl fmt::Display for ConfigError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            ConfigError::ConfigMissing => {
                write!(f, "No OpenFUT server configured (config file missing)")
            }
            ConfigError::ServerMissing => write!(
                f,
                "No OpenFUT server configured. Enter the hostname or IP address of your OpenFUT server."
            ),
            ConfigError::InvalidAddress(a) => write!(f, "Invalid OpenFUT server address: {a}"),
            ConfigError::InvalidPort(p) => write!(f, "Invalid OpenFUT port: {p}"),
            ConfigError::MalformedConfig(m) => write!(f, "Malformed OpenFUT config: {m}"),
        }
    }
}

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

impl ServerConfig {
    /// Parse `openfut.cfg` contents.
    ///
    /// Two accepted formats:
    ///   * **Structured** (preferred), one `key=value` per line:
    ///     ```text
    ///     host=192.168.1.50
    ///     https_port=8443
    ///     blaze_redirector_port=10041
    ///     blaze_main_port=42127
    ///     ```
    ///     `host` is required; any omitted port uses its default.
    ///   * **Legacy**, a single bare line containing just the host
    ///     (IPv4 or hostname). Ports default. This keeps old deployments working.
    ///
    /// An empty/whitespace-only body is [`ConfigError::ServerMissing`], NOT a
    /// silent loopback fallback.
    pub fn parse(contents: &str) -> Result<Self, ConfigError> {
        let trimmed = contents.trim();
        if trimmed.is_empty() {
            return Err(ConfigError::ServerMissing);
        }

        // Legacy single-token form: no '=' anywhere and a single line.
        let has_kv = trimmed.lines().any(|l| l.contains('='));
        if !has_kv {
            let host = trimmed.trim();
            if host.is_empty() {
                return Err(ConfigError::ServerMissing);
            }
            return Ok(Self {
                host: host.to_string(),
                ports: OpenFutPorts::default(),
            });
        }

        let mut host: Option<String> = None;
        let mut ports = OpenFutPorts::default();

        for (lineno, raw) in trimmed.lines().enumerate() {
            let line = raw.trim();
            if line.is_empty() || line.starts_with('#') {
                continue;
            }
            let (key, value) = line.split_once('=').ok_or_else(|| {
                ConfigError::MalformedConfig(format!("line {}: expected key=value", lineno + 1))
            })?;
            let key = key.trim();
            let value = value.trim();
            match key {
                "host" | "server" | "redirect_ip" => {
                    if value.is_empty() {
                        return Err(ConfigError::ServerMissing);
                    }
                    host = Some(value.to_string());
                }
                "https_port" => ports.https = parse_port(value)?,
                "blaze_redirector_port" => ports.blaze_redirector = parse_port(value)?,
                "blaze_main_port" => ports.blaze_main = parse_port(value)?,
                other => {
                    return Err(ConfigError::MalformedConfig(format!(
                        "line {}: unknown key '{other}'",
                        lineno + 1
                    )));
                }
            }
        }

        let host = host.ok_or(ConfigError::ServerMissing)?;
        Ok(Self { host, ports })
    }

    /// Serialize to the structured `openfut.cfg` format.
    pub fn to_cfg_string(&self) -> String {
        format!(
            "host={}\nhttps_port={}\nblaze_redirector_port={}\nblaze_main_port={}\n",
            self.host, self.ports.https, self.ports.blaze_redirector, self.ports.blaze_main
        )
    }

    /// Validate the host is a syntactically acceptable IPv4 literal or hostname.
    /// Does NOT perform DNS (no network) — use [`Self::resolve`] for that.
    pub fn validate(&self) -> Result<(), ConfigError> {
        let host = self.host.trim();
        if host.is_empty() {
            return Err(ConfigError::ServerMissing);
        }
        if Ipv4Addr::from_str(host).is_ok() {
            return Ok(());
        }
        if is_plausible_hostname(host) {
            Ok(())
        } else {
            Err(ConfigError::InvalidAddress(host.to_string()))
        }
    }

    /// Resolve the configured host to a concrete IPv4 destination.
    ///
    /// This is the single shared resolution path all hooks rely on: an IPv4
    /// literal is used directly; a hostname is resolved via the platform
    /// resolver ([`ToSocketAddrs`]). Only IPv4 results are used (WinSock
    /// interception here is IPv4). Never falls back to loopback.
    pub fn resolve(&self) -> Result<ResolvedServer, ConfigError> {
        let host = self.host.trim();
        if host.is_empty() {
            return Err(ConfigError::ServerMissing);
        }

        // IPv4 literal: no DNS needed.
        if let Ok(ip) = Ipv4Addr::from_str(host) {
            return Ok(ResolvedServer {
                redirect_ip: ip,
                ports: self.ports,
            });
        }

        // Hostname: resolve via the platform resolver. Port is irrelevant to
        // the lookup; we only need an address. Take the first IPv4 answer.
        let ip = (host, 0u16)
            .to_socket_addrs()
            .map_err(|e| ConfigError::InvalidAddress(format!("{host}: {e}")))?
            .find_map(|sa| match sa.ip() {
                std::net::IpAddr::V4(v4) => Some(v4),
                std::net::IpAddr::V6(_) => None,
            })
            .ok_or_else(|| ConfigError::InvalidAddress(format!("{host}: no IPv4 address found")))?;

        Ok(ResolvedServer {
            redirect_ip: ip,
            ports: self.ports,
        })
    }
}

fn parse_port(value: &str) -> Result<u16, ConfigError> {
    let n: u16 = value
        .parse()
        .map_err(|_| ConfigError::InvalidPort(value.to_string()))?;
    if n == 0 {
        return Err(ConfigError::InvalidPort(value.to_string()));
    }
    Ok(n)
}

/// Lenient hostname sanity check (RFC-1123-ish). Not a full validator — just
/// enough to reject obvious garbage while accepting `.local`/`.home` names.
fn is_plausible_hostname(host: &str) -> bool {
    if host.is_empty() || host.len() > 253 {
        return false;
    }
    host.split('.').all(|label| {
        !label.is_empty()
            && label.len() <= 63
            && label.chars().all(|c| c.is_ascii_alphanumeric() || c == '-')
            && !label.starts_with('-')
            && !label.ends_with('-')
    })
}

// ── WinSock representation helpers ───────────────────────────────────────────
// These convert a resolved destination into the exact in-memory representation
// WinSock's `sockaddr_in` expects. Kept here (not in the DLL) so the byte-order
// contract the socket hooks depend on is unit-tested on the host.

/// Value to store in `sockaddr_in.sin_addr.S_un.S_addr`.
///
/// WinSock stores the four IPv4 octets in network byte order in memory. Reading
/// those bytes back as a native-endian `u32` (how the hook's `SockaddrIn.sin_addr`
/// field is typed) is exactly `from_ne_bytes(octets)`. On little-endian x86_64
/// this yields e.g. `127.0.0.1 -> 0x0100_007F`, matching the value the original
/// hooks hardcoded — confirming the conversion is correct.
pub fn sin_addr_from_ipv4(ip: Ipv4Addr) -> u32 {
    u32::from_ne_bytes(ip.octets())
}

/// Value to store in `sockaddr_in.sin_port` — the port in network byte order.
pub fn sin_port_nbo(port: u16) -> u16 {
    port.to_be()
}

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

    #[test]
    fn configured_ipv4_survives_parsing() {
        let c = ServerConfig::parse("host=192.168.1.50\n").unwrap();
        assert_eq!(c.host, "192.168.1.50");
        assert_eq!(c.ports, OpenFutPorts::default());
    }

    #[test]
    fn legacy_bare_host_line_parses() {
        let c = ServerConfig::parse("10.0.0.7\n").unwrap();
        assert_eq!(c.host, "10.0.0.7");
        assert_eq!(c.ports, OpenFutPorts::default());
    }

    #[test]
    fn missing_server_does_not_become_loopback() {
        // Empty config is an explicit error, never 127.0.0.1.
        assert_eq!(
            ServerConfig::parse("").unwrap_err(),
            ConfigError::ServerMissing
        );
        assert_eq!(
            ServerConfig::parse("   \n\n").unwrap_err(),
            ConfigError::ServerMissing
        );
        assert_eq!(
            ServerConfig::parse("https_port=8443\n").unwrap_err(),
            ConfigError::ServerMissing
        );
    }

    #[test]
    fn invalid_server_is_rejected() {
        let c = ServerConfig {
            host: "not a host!!".into(),
            ports: OpenFutPorts::default(),
        };
        assert!(matches!(c.validate(), Err(ConfigError::InvalidAddress(_))));
    }

    #[test]
    fn configured_port_survives_parsing() {
        let c = ServerConfig::parse(
            "host=srv.home\nhttps_port=9000\nblaze_redirector_port=11000\nblaze_main_port=42000\n",
        )
        .unwrap();
        assert_eq!(c.ports.https, 9000);
        assert_eq!(c.ports.blaze_redirector, 11000);
        assert_eq!(c.ports.blaze_main, 42000);
    }

    #[test]
    fn invalid_port_is_rejected() {
        assert!(matches!(
            ServerConfig::parse("host=x\nhttps_port=0\n"),
            Err(ConfigError::InvalidPort(_))
        ));
        assert!(matches!(
            ServerConfig::parse("host=x\nhttps_port=99999\n"),
            Err(ConfigError::InvalidPort(_))
        ));
    }

    #[test]
    fn unknown_key_is_malformed() {
        assert!(matches!(
            ServerConfig::parse("host=x\nbogus=1\n"),
            Err(ConfigError::MalformedConfig(_))
        ));
    }

    #[test]
    fn roundtrip_cfg_string() {
        let c = ServerConfig {
            host: "192.168.1.50".into(),
            ports: OpenFutPorts {
                https: 8443,
                blaze_redirector: 10041,
                blaze_main: 42127,
            },
        };
        let s = c.to_cfg_string();
        assert_eq!(ServerConfig::parse(&s).unwrap(), c);
    }

    #[test]
    fn configured_ipv4_becomes_correct_sockaddr() {
        // Resolve an IPv4 literal and confirm the sin_addr value.
        let c = ServerConfig::parse("host=192.168.1.50\n").unwrap();
        let r = c.resolve().unwrap();
        assert_eq!(r.redirect_ip, Ipv4Addr::new(192, 168, 1, 50));
        // sin_addr is the octets as a native-endian u32.
        assert_eq!(
            sin_addr_from_ipv4(r.redirect_ip),
            u32::from_ne_bytes([192, 168, 1, 50])
        );
    }

    #[test]
    fn loopback_sockaddr_matches_legacy_constant() {
        // Guards the byte-order contract: the old hooks hardcoded 0x0100_007F
        // for 127.0.0.1. Our helper must reproduce it on this (LE) host.
        assert_eq!(sin_addr_from_ipv4(Ipv4Addr::new(127, 0, 0, 1)), 0x0100_007F);
    }

    #[test]
    fn sin_port_is_network_byte_order() {
        // 443 -> 0xBB01, 42127 -> 0x8FA4 (matches the legacy hook constants).
        assert_eq!(sin_port_nbo(443), 0xBB01);
        assert_eq!(sin_port_nbo(42127), 0x8FA4);
        assert_eq!(sin_port_nbo(10041), 0x3927);
    }

    #[test]
    fn port_mapping_source_to_destination() {
        let p = OpenFutPorts::default();
        assert_eq!(p.map_source_port(ea_ports::HTTPS), Some(8443));
        assert_eq!(p.map_source_port(ea_ports::BLAZE_REDIRECTOR), Some(42127));
        assert_eq!(
            p.map_source_port(ea_ports::FIFA17_BLAZE_REDIRECTOR),
            Some(42127)
        );
        assert_eq!(p.map_source_port(ea_ports::BLAZE_MAIN), Some(42130));
        assert_eq!(p.map_source_port(12345), None);
    }

    #[test]
    fn resolve_literal_ipv4_no_dns() {
        let c = ServerConfig::parse("host=127.0.0.1\n").unwrap();
        let r = c.resolve().unwrap();
        assert_eq!(r.redirect_ip, Ipv4Addr::LOCALHOST);
    }

    #[test]
    fn resolve_empty_host_errors() {
        let c = ServerConfig {
            host: "   ".into(),
            ports: OpenFutPorts::default(),
        };
        assert_eq!(c.resolve().unwrap_err(), ConfigError::ServerMissing);
    }
}