use crate::errors::*;
use crate::ser::packet::{DnsPacketData, DnsPacketWriteContext};
use crate::ser::text::{next_field, parse_with, DnsTextContext, DnsTextData, DnsTextFormatter};
use bytes::Bytes;
use smallvec::SmallVec;
use std::fmt;
use std::io::Cursor;
use std::str::FromStr;

use super::{DisplayLabels, DnsLabel, DnsLabelRef, DnsNameIterator, LabelOffsets};

/// A DNS name
///
/// Uses the "original" raw representation for storage (i.e. can share
/// memory with a parsed packet)
#[derive(Clone)]
pub struct DnsName {
	// in uncompressed form always includes terminating null octect;
	// but even in uncompressed form can include unused bytes at the
	// beginning
	//
	// may be empty for the root name (".", no labels)
	pub(super) data: Bytes,
	// either uncompressed or compressed offsets
	pub(super) label_offsets: LabelOffsets,
	// length of encoded form
	pub(super) total_len: u8,
}

impl DnsName {
	/// Create new name representing the DNS root (".")
	pub fn new_root() -> Self {
		DnsName {
			data: Bytes::new(),
			label_offsets: LabelOffsets::Uncompressed(SmallVec::new()),
			total_len: 1,
		}
	}

	/// Create new name representing the DNS root (".") and pre-allocate
	/// storage
	pub fn with_capacity(labels: u8, total_len: u8) -> Self {
		DnsName {
			data: Bytes::with_capacity(total_len as usize),
			label_offsets: LabelOffsets::Uncompressed(SmallVec::with_capacity(labels as usize)),
			total_len: 1,
		}
	}

	/// Parse text representation of a domain name
	pub fn parse(context: &DnsTextContext, value: &str) -> Result<Self> {
		super::name_text_parser::parse_name(context, value)
	}

	/// Returns whether name represents the DNS root (".")
	pub fn is_root(&self) -> bool {
		0 == self.label_count()
	}

	/// How many labels the name has (without the trailing empty label,
	/// at most 127)
	pub fn label_count(&self) -> u8 {
		self.label_offsets.len()
	}

	/// Iterator over the labels (in the order they are stored in memory,
	/// i.e. top-level name last).
	pub fn labels<'a>(&'a self) -> DnsNameIterator<'a> {
		DnsNameIterator {
			name: &self,
			front_label: 0,
			back_label: self.label_offsets.len(),
		}
	}

	/// Return label at index `ndx`
	///
	/// # Panics
	///
	/// panics if `ndx >= self.label_count()`.
	pub fn label_ref<'a>(&'a self, ndx: u8) -> DnsLabelRef<'a> {
		let pos = self.label_offsets.label_pos(ndx);
		let label_len = self.data[pos];
		debug_assert!(label_len < 64);
		let end = pos + 1 + label_len as usize;
		DnsLabelRef {
			label: &self.data[pos + 1..end],
		}
	}

	/// Return label at index `ndx`
	///
	/// # Panics
	///
	/// panics if `ndx >= self.label_count()`.
	pub fn label(&self, ndx: u8) -> DnsLabel {
		let pos = self.label_offsets.label_pos(ndx);
		let label_len = self.data[pos];
		debug_assert!(label_len < 64);
		let end = pos + 1 + label_len as usize;
		DnsLabel {
			label: self.data.slice(pos + 1, end),
		}
	}
}

impl<'a> IntoIterator for &'a DnsName {
	type Item = DnsLabelRef<'a>;
	type IntoIter = DnsNameIterator<'a>;

	fn into_iter(self) -> Self::IntoIter {
		self.labels()
	}
}

impl PartialEq<DnsName> for DnsName {
	fn eq(&self, rhs: &DnsName) -> bool {
		let a_labels = self.labels();
		let b_labels = rhs.labels();
		if a_labels.len() != b_labels.len() {
			return false;
		}
		a_labels.zip(b_labels).all(|(a, b)| a == b)
	}
}

impl<T> PartialEq<T> for DnsName
where
	T: AsRef<DnsName>,
{
	fn eq(&self, rhs: &T) -> bool {
		self == rhs.as_ref()
	}
}

impl Eq for DnsName {}

impl fmt::Debug for DnsName {
	fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
		DisplayLabels {
			labels: self,
			options: Default::default(),
		}
		.fmt(w)
	}
}

impl fmt::Display for DnsName {
	fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
		DisplayLabels {
			labels: self,
			options: Default::default(),
		}
		.fmt(w)
	}
}

impl FromStr for DnsName {
	type Err = ::failure::Error;

	fn from_str(s: &str) -> Result<Self> {
		parse_with(s, |data| DnsName::dns_parse(&DnsTextContext::new(), data))
	}
}

impl DnsTextData for DnsName {
	fn dns_parse(context: &DnsTextContext, data: &mut &str) -> Result<Self> {
		let field = next_field(data)?;
		DnsName::parse(context, field)
	}

	fn dns_format(&self, f: &mut DnsTextFormatter) -> fmt::Result {
		write!(f, "{}", self)
	}
}

impl DnsPacketData for DnsName {
	fn deserialize(data: &mut Cursor<Bytes>) -> Result<Self> {
		super::name_packet_parser::deserialize_name(data, false)
	}

	fn serialize(&self, context: &mut DnsPacketWriteContext, packet: &mut Vec<u8>) -> Result<()> {
		context.write_uncompressed_name(packet, self)
	}
}