use std::fmt::Display;
use std::net::{IpAddr, Ipv6Addr};
use std::str::FromStr;
use std::fmt::Formatter;
use mlua::{FromLua, FromLuaMulti, Lua, UserData, UserDataFields, UserDataMethods, Value};

#[derive(Copy, Clone)]
struct Cidr {
    addr: IpAddr,
    prefix: u8,
}

impl Display for Cidr {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}/{}", self.addr, self.prefix)
    }
}

impl Cidr {
    fn to_v6(&self) -> Self {
        match self.addr {
            IpAddr::V4(ip) => Cidr {
                addr: IpAddr::V6(ip.to_ipv6_mapped()),
                prefix: self.prefix + 96,
            },
            IpAddr::V6(_) => *self,
        }
    }
}

#[repr(transparent)]
#[derive(Copy, Clone)]
struct IpAddrWrapper(IpAddr);

impl IpAddrWrapper {
    fn octet_len(&self) -> usize {
        match &self.0 {
            IpAddr::V4(_) => 4,
            IpAddr::V6(_) => 16,
        }
    }

    fn to_v6(&self) -> Ipv6Addr {
        match self.0 {
            IpAddr::V4(v4) => v4.to_ipv6_mapped(),
            IpAddr::V6(v6) => v6
        }
    }
}

impl UserData for IpAddrWrapper {
    fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
        fields.add_field_method_get("version", |_, ip| Ok(if ip.0.is_ipv4() { 4} else {6}));
        fields.add_field_method_get("is_ipv4", |_, ip| Ok(ip.0.is_ipv4()));
        fields.add_field_method_get("is_ipv6", |_, ip| Ok(ip.0.is_ipv6()));
        fields.add_field_method_get("bytes", |lua, ip| match &ip.0 {
            IpAddr::V4(v4) => lua.create_string(v4.octets()),
            IpAddr::V6(v6) => lua.create_string(v6.octets()),
        });
        fields.add_meta_field("__name", "IpAddr");
    }

    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
        methods.add_method("to_v6", |_, ip, ()| match &ip.0 {
            IpAddr::V4(v4) => Ok(IpAddrWrapper(IpAddr::V6(v4.to_ipv6_mapped()))),
            IpAddr::V6(v6) => Ok(IpAddrWrapper(IpAddr::V6(*v6))),
        });
        methods.add_meta_method("__index", |_, ip, index: usize| match &ip.0 {
            IpAddr::V4(ip) if 1 <= index && index <= 4 => Ok(ip.octets()[index-1]),
            IpAddr::V6(ip) if 1 <= index && index <= 16 => Ok(ip.octets()[index-1]),
            _ => Err(mlua::Error::runtime("Index out of range")),
        });
        methods.add_meta_method_mut("__newindex", |_, ip, (index, value): (usize, u8)| {
            match &mut ip.0 {
                IpAddr::V4(ip) if 1 <= index && index <= 4 => {
                    let mut octets = ip.octets();
                    octets[index-1] = value;
                    IpAddr::V4(octets.into());
                },
                IpAddr::V6(ip) if 1 <= index && index <= 16 => {
                    let mut octets = ip.octets();
                    octets[index-1] = value;
                    IpAddr::V6(octets.into());
                },
                _ => return Err(mlua::Error::runtime("Index out of range")),
            };
            Ok(())
        });
        methods.add_meta_method("__tostring", |_, ip, ()|  Ok(ip.0.to_string()));
        methods.add_meta_function("__call", |lua, args: mlua::MultiValue| Ok(IpAddrWrapper({
            eprintln!("IpAddr __call Received {} args", args.len());
            if args.len() == 4 {
                // IPV4 direct bytes
                let (a,b,c,d) = <(u8,u8,u8,u8)>::from_lua_args(args, 0, Some("sftpd.IpAddr"), lua)?;
                IpAddr::V4([a,b,c,d].into())
            } else if args.len() == 16 {
                let mut octets = [0u8;16];
                for i in 0..16 {
                    octets[i] = u8::from_lua(args.get(i).unwrap().clone(), lua)?;
                }
                IpAddr::V6(octets.into())
            } else if args.len() == 1 {
                return IpAddrWrapper::from_lua(args[0].clone(), lua);
            } else {
                return Err(mlua::Error::runtime("Invalid arguments to stfptd.IpAddr"))
            }
        })));
        methods.add_meta_method("__eq", |_, me, other: IpAddrWrapper| Ok(me.to_v6() == other.to_v6()))
    }
}

impl<'lua> FromLua<'lua> for IpAddrWrapper {
    fn from_lua(value: Value<'lua>, _: &'lua Lua) -> mlua::Result<Self> {
        return if let Some(ud) = value.as_userdata() {
            Ok(ud.borrow::<IpAddrWrapper>()?.clone())
        } else if let Some(s) = value.as_str() {
            IpAddr::from_str(s)
                .map(IpAddrWrapper)
                .map_err(mlua::Error::external)
        } else {
            Err(mlua::Error::FromLuaConversionError {
                from: value.type_name(),
                to: "IpAddr",
                message: None,
            })
        }
    }
}

impl UserData for Cidr {
    fn add_fields<'lua, F: UserDataFields<'lua, Self>>(fields: &mut F) {
        fields.add_field_method_get("addr", |_lua, cidr| Ok(IpAddrWrapper(cidr.addr)));
        fields.add_field_method_set("addr", |_lua, cidr, value: IpAddrWrapper| {
            if cidr.addr.is_ipv4() ^ value.0.is_ipv4() {
                return Err(mlua::Error::runtime(format!(
                    "Cannot assign v{} addr to v{} CIDR",
                    if value.0.is_ipv4() { 4 } else { 6 },
                    if cidr.addr.is_ipv4() { 4 } else { 6 },
                )));
            }
            cidr.addr = value.0;
            Ok(())
        });
        fields.add_field_method_get("prefix", |_lua, cidr| Ok(cidr.prefix));
        fields.add_field_method_set("prefix", |_lua, cidr, value: u8| {
            if value >= if cidr.addr.is_ipv4() { 32 } else { 128 } {
                return Err(mlua::Error::runtime("Invalid prefix length"));
            }
            cidr.prefix = value;
            Ok(())
        });
    }

    fn add_methods<'lua, M: UserDataMethods<'lua, Self>>(methods: &mut M) {
        methods.add_method("contains", |_, cidr, addr: IpAddrWrapper| {
            let addr = u128::from_be_bytes(addr.to_v6().octets());
            let cidr = cidr.to_v6();
            if cidr.prefix == 0 {
                // Global network
                return Ok(true)
            }
            let mask = (!0u128) << (128 - cidr.prefix);
            let network = u128::from_be_bytes(IpAddrWrapper(cidr.addr).to_v6().octets());

            Ok(addr & mask == network & mask)
        });

        methods.add_meta_method("__tostring", |_, cidr, ()| Ok(cidr.to_string()));
        methods.add_meta_method("__eq", |_, cidr, other: Cidr| {
            let cidr = cidr.to_v6();
            let other = other.to_v6();
            Ok(cidr.prefix == other.prefix && cidr.addr == other.addr)
        });

        methods.add_meta_function("__call", |lua, args: mlua::MultiValue| {
            if args.len() == 0 {
                Ok(Cidr{addr: IpAddr::V6(Ipv6Addr::UNSPECIFIED), prefix: 0})
            } else if args.len() == 1 {
                Cidr::from_lua_args(args, 0, Some("stftpd.Cidr"), lua)
            } else {
                let (IpAddrWrapper(addr), prefix) = <(IpAddrWrapper, u8)>::from_lua_args(args, 0, Some("stftpd.Cidr"), lua)?;
                let max_prefix = if addr.is_ipv4() { 32 } else { 64 };
                if prefix > max_prefix {
                    return Err(mlua::Error::runtime("Invalid prefix"));
                }
                Ok(Cidr{addr, prefix})
            }
        });
    }
}

impl<'lua> FromLua<'lua> for Cidr {
    fn from_lua(value: Value<'lua>, _: &'lua Lua) -> mlua::Result<Self> {
        return if let Some(ud) = value.as_userdata() {
            Ok(ud.borrow::<Cidr>()?.clone())
        } else if let Some(s) = value.as_str() {
            let (addr, prefix) = s.split_once("/")
                .map(|(a,p)| (a,Some(p)))
                .unwrap_or((s, None));
            let addr = IpAddr::from_str(addr)?;
            let prefix = prefix.map(u8::from_str)
                .transpose()
                .map_err(mlua::Error::external)?;

            let max_prefix = if addr.is_ipv4() { 32 } else { 128 };
            let prefix = prefix.unwrap_or(max_prefix);
            if prefix > max_prefix {
                return Err(mlua::Error::runtime("CIDR prefix to long"))
            }

            Ok(Cidr {
                addr, prefix
            })
        } else {
            Err(mlua::Error::FromLuaConversionError {
                from: value.type_name(),
                to: "Cidr",
                message: None,
            })
        }
    }
}

pub fn register(lua: &'static Lua) -> anyhow::Result<()> {
    let globals = lua.globals();
    let stftpd: Value = globals.get("stftpd")?;
    let stftpd = if stftpd.is_nil() {
        let newtab = lua.create_table()?;
        globals.set("stftpd", newtab.clone())?;
        newtab
    } else {
        stftpd.as_table().unwrap().clone()
    };
    stftpd.set("Cidr", lua.create_proxy::<Cidr>()?)?;
    stftpd.set("IpAddr", lua.create_proxy::<IpAddrWrapper>()?)?;

    Ok(())
}