use bytes::Bytes;
use std::any::TypeId;
use std::collections::HashMap;
use std::io::Cursor;
use std::marker::PhantomData;

use crate::common_types::{Class, Type, types};
use crate::errors::*;
use crate::records::structs;
use crate::ser::{RRData, StaticRRData};
use crate::ser::text::DnsTextContext;

// this should be enough for registered names
const TYPE_NAME_MAX_LEN: usize = 16;

lazy_static::lazy_static!{
	static ref REGISTRY: Registry = Registry::init();
}

fn registry() -> &'static Registry {
	&*REGISTRY
}

pub(crate) fn lookup_type_name(name: &str) -> Option<Type> {
	if name.len() >= TYPE_NAME_MAX_LEN { return None; }
	let mut name_buf_storage = [0u8; TYPE_NAME_MAX_LEN];
	let name_buf = &mut name_buf_storage[..name.len()];
	name_buf.copy_from_slice(name.as_bytes());

	name_buf.make_ascii_uppercase();

	let registry = registry();
	let &t = registry.names_to_type.get(name_buf)?;
	Some(t)
}

pub fn known_name_to_type(name: &str) -> Option<Type> {
	let registry = registry();
	let t = lookup_type_name(name)?;
	registry.type_parser.get(&t)?;

	Some(t)
}

pub fn deserialize_rr_data(ttl: u32, rr_class: Class, rr_type: Type, data: &mut Cursor<Bytes>) -> Result<Box<dyn RRData>> {
	let registry = registry();
	match registry.type_parser.get(&rr_type) {
		Some(p) => p.deserialize_rr_data(ttl, rr_class, rr_type, data),
		None => Ok(Box::new(super::UnknownRecord::deserialize(rr_type, data)?) as _),
	}
}

pub fn parse_rr_data(context: &DnsTextContext, data: &mut &str) -> Result<Box<dyn RRData>> {
	let registry = registry();
	let t = match context.record_type() {
		Some(t) => t,
		None => failure::bail!("require record type to parse record data"),
	};
	match registry.type_parser.get(&t) {
		Some(p) => p.parse_rr_data(context, data),
		None => failure::bail!("unknown type: {}", t),
	}
}

pub(crate) fn lookup_type_to_name(rrtype: Type) -> Option<&'static str> {
	let registry = registry();
	registry.type_names.get(&rrtype).map(|s| s as _)
}

#[doc(hidden)]
pub fn check_registration<T: StaticRRData + Sync + 'static>() {
	registry().check_registration::<T>();
}

#[derive(Clone, Copy, Debug)]
struct TagRRDataType<T: RRData>(PhantomData<T>);

trait RRDataTypeParse: 'static {
	fn type_id(&self) -> TypeId {
		TypeId::of::<Self>()
	}

	fn deserialize_rr_data(&self, ttl: u32, rr_class: Class, rr_type: Type, data: &mut Cursor<Bytes>) -> Result<Box<dyn RRData>>;

	fn parse_rr_data(&self, context: &DnsTextContext, data: &mut &str) -> Result<Box<dyn RRData>>;
}

impl<T: RRData + 'static> RRDataTypeParse for TagRRDataType<T> {
	fn deserialize_rr_data(&self, ttl: u32, rr_class: Class, rr_type: Type, data: &mut Cursor<Bytes>) -> Result<Box<dyn RRData>> {
		T::deserialize_rr_data(ttl, rr_class, rr_type, data).map(|d| Box::new(d) as _)
	}

	fn parse_rr_data(&self, context: &DnsTextContext, data: &mut &str) -> Result<Box<dyn RRData>> {
		T::dns_parse_rr_data(context, data).map(|d| Box::new(d) as _)
	}
}

struct Registry {
	// store (ascii) upper-case names.
	names_to_type: HashMap<Vec<u8>, Type>,
	type_names: HashMap<Type, String>,
	type_parser: HashMap<Type, Box<dyn RRDataTypeParse + Sync>>,
	// make sure registrations are in order
	prev_type: Option<Type>,
}

impl Registry {
	fn init() -> Self {
		let mut r = Registry {
			names_to_type: HashMap::new(),
			type_names: HashMap::new(),
			type_parser: HashMap::new(),
			prev_type: None,
		};

		r.register_known::<structs::A>();
		r.register_known::<structs::NS>();
		r.register_known::<structs::MD>();
		r.register_known::<structs::MF>();
		r.register_known::<structs::CNAME>();
		r.register_known::<structs::SOA>();
		r.register_known::<structs::MB>();
		r.register_known::<structs::MG>();
		r.register_known::<structs::MR>();
		r.register_unknown("NULL"      , types::NULL);
		r.register_unknown("WKS"       , types::WKS);
		r.register_known::<structs::PTR>();
		r.register_known::<structs::HINFO>();
		r.register_known::<structs::MINFO>();
		r.register_known::<structs::MX>();
		r.register_known::<structs::TXT>();
		r.register_known::<structs::RP>();
		r.register_known::<structs::AFSDB>();
		r.register_unknown("X25"       , types::X25);
		r.register_unknown("ISDN"      , types::ISDN);
		r.register_known::<structs::RT>();
		r.register_unknown("NSAP"      , types::NSAP);
		r.register_known::<structs::NSAP_PTR>();
		r.register_known::<structs::SIG>();
		r.register_known::<structs::KEY>();
		r.register_known::<structs::PX>();
		r.register_known::<structs::GPOS>();
		r.register_known::<structs::AAAA>();
		r.register_known::<structs::LOC>();
		r.register_known::<structs::NXT>();
		r.register_unknown("EID"       , types::EID);
		r.register_unknown("NIMLOC"    , types::NIMLOC);
		r.register_known::<structs::SRV>();
		r.register_unknown("ATMA"      , types::ATMA);
		r.register_known::<structs::NAPTR>();
		r.register_known::<structs::KX>();
		r.register_known::<structs::CERT>();
		r.register_known::<structs::A6>();
		r.register_known::<structs::DNAME>();
		r.register_unknown("SINK"      , types::SINK);
		r.register_unknown("OPT"       , types::OPT);
		r.register_known::<structs::APL>();
		r.register_known::<structs::DS>();
		r.register_known::<structs::SSHFP>();
		r.register_known::<structs::IPSECKEY>();
		r.register_known::<structs::RRSIG>();
		r.register_known::<structs::NSEC>();
		r.register_known::<structs::DNSKEY>();
		r.register_known::<structs::DHCID>();
		r.register_known::<structs::NSEC3>();
		r.register_known::<structs::NSEC3PARAM>();
		r.register_known::<structs::TLSA>();
		r.register_known::<structs::SMIMEA>();
		r.register_unknown("HIP"       , types::HIP);
		r.register_known::<structs::NINFO>();
		r.register_known::<structs::RKEY>();
		r.register_unknown("TALINK"    , types::TALINK);
		r.register_known::<structs::CDS>();
		r.register_known::<structs::CDNSKEY>();
		r.register_known::<structs::OPENPGPKEY>();
		r.register_unknown("CSYNC"     , types::CSYNC);
		r.register_unknown("ZONEMD"    , types::ZONEMD);
		r.register_known::<structs::SPF>();
		r.register_unknown("UINFO"     , types::UINFO);
		r.register_unknown("UID"       , types::UID);
		r.register_unknown("GID"       , types::GID);
		r.register_unknown("UNSPEC"    , types::UNSPEC);
		r.register_unknown("NID"       , types::NID);
		r.register_unknown("L32"       , types::L32);
		r.register_unknown("L64"       , types::L64);
		r.register_unknown("LP"        , types::LP);
		r.register_known::<structs::EUI48>();
		r.register_known::<structs::EUI64>();
		r.register_known::<structs::TKEY>();
		r.register_known::<structs::TSIG>();
		r.register_unknown("IXFR"      , types::IXFR);
		r.register_unknown("AXFR"      , types::AXFR);
		r.register_unknown("MAILB"     , types::MAILB);
		r.register_unknown("MAILA"     , types::MAILA);
		r.register_unknown("ANY"       , types::ANY);
		r.register_known::<structs::URI>();
		r.register_known::<structs::CAA>();
		r.register_unknown("AVC"       , types::AVC);
		r.register_unknown("DOA"       , types::DOA);
		r.register_unknown("AMTRELAY"  , types::AMTRELAY);
		r.register_unknown("TA"        , types::TA);
		r.register_known::<structs::DLV>();
		r.register_known::<structs::ALIAS>();

		// "ALL" could be an alias for the ANY type?
		// assert!(r.names_to_type.insert("ALL".into(), types::ANY).is_none());

		r
	}

	fn register_name(&mut self, name: &str, rrtype: Type) {
		assert!(self.prev_type < Some(rrtype), "registration not in order");
		self.prev_type = Some(rrtype);
		let mut name: String = name.into();
		name.make_ascii_uppercase();
		assert!(!name.starts_with("TYPE"), "must not register generic name: {}", name);
		assert!(name.len() <= TYPE_NAME_MAX_LEN, "name too long: {} - maybe you need to increase TYPE_NAME_MAX_LEN", name);
		assert!(self.names_to_type.insert(name.clone().into_bytes(), rrtype).is_none());
		self.type_names.insert(rrtype, name);
	}

	fn register_unknown(&mut self, name: &'static str, rrtype: Type) {
		self.register_name(name, rrtype);
	}

	fn register_known<T: StaticRRData + Sync + 'static>(&mut self) {
		let rrtype = T::TYPE;
		let name = T::NAME;
		self.register_name(name, rrtype);
		self.type_parser.insert(rrtype, Box::new(TagRRDataType::<T>(PhantomData)));
	}

	fn check_registration<T: StaticRRData + Sync + 'static>(&self) {
		assert_eq!(self.names_to_type.get(T::NAME.as_bytes()), Some(&T::TYPE));
		let p: &dyn RRDataTypeParse = &**self.type_parser.get(&T::TYPE).expect("no parser registered");
		let tid = TypeId::of::<TagRRDataType<T>>();
		assert_eq!(p.type_id(), tid);
	}
}