// Copyright 2015-2019 Benjamin Fry <benjaminfry@me.com>
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.

//! Dynamic Delegation Discovery System

use crate::error::*;
use crate::rr::domain::Name;
use crate::serialize::binary::*;

/// [RFC 3403 DDDS DNS Database, October 2002](https://tools.ietf.org/html/rfc3403#section-4)
///
/// ```text
/// 4.1 Packet Format
///
///   The packet format of the NAPTR RR is given below.  The DNS type code
///   for NAPTR is 35.
///
///      The packet format for the NAPTR record is as follows
///                                       1  1  1  1  1  1
///         0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///       |                     ORDER                     |
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///       |                   PREFERENCE                  |
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///       /                     FLAGS                     /
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///       /                   SERVICES                    /
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///       /                    REGEXP                     /
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///       /                  REPLACEMENT                  /
///       /                                               /
///       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
///
///   <character-string> and <domain-name> as used here are defined in RFC
///   1035 [7].
/// ```
#[derive(Debug, PartialEq, Eq, Hash, Clone)]
pub struct NAPTR {
    order: u16,
    preference: u16,
    flags: Box<[u8]>,
    services: Box<[u8]>,
    regexp: Box<[u8]>,
    replacement: Name,
}

impl NAPTR {
    /// Constructs a new NAPTR record
    ///
    /// # Arguments
    ///
    /// * `order` - the order in which the NAPTR records MUST be processed in order to accurately represent the ordered list of Rules.
    /// * `preference` - this field is equivalent to the Priority value in the DDDS Algorithm.
    /// * `flags` - flags to control aspects of the rewriting and interpretation of the fields in the record.  Flags are single characters from the set A-Z and 0-9.
    /// * `services` - the Service Parameters applicable to this this delegation path.
    /// * `regexp` - substitution expression that is applied to the original string held by the client in order to construct the next domain name to lookup.
    /// * `replacement` - the next domain-name to query for depending on the potential values found in the flags field.
    pub fn new(
        order: u16,
        preference: u16,
        flags: Box<[u8]>,
        services: Box<[u8]>,
        regexp: Box<[u8]>,
        replacement: Name,
    ) -> Self {
        Self {
            order,
            preference,
            flags,
            services,
            regexp,
            replacement,
        }
    }

    /// ```text
    ///   ORDER
    ///      A 16-bit unsigned integer specifying the order in which the NAPTR
    ///      records MUST be processed in order to accurately represent the
    ///      ordered list of Rules.  The ordering is from lowest to highest.
    ///      If two records have the same order value then they are considered
    ///      to be the same rule and should be selected based on the
    ///      combination of the Preference values and Services offered.
    /// ```
    pub fn order(&self) -> u16 {
        self.order
    }

    /// ```text
    ///   PREFERENCE
    ///      Although it is called "preference" in deference to DNS
    ///      terminology, this field is equivalent to the Priority value in the
    ///      DDDS Algorithm.  It is a 16-bit unsigned integer that specifies
    ///      the order in which NAPTR records with equal Order values SHOULD be
    ///      processed, low numbers being processed before high numbers.  This
    ///      is similar to the preference field in an MX record, and is used so
    ///      domain administrators can direct clients towards more capable
    ///      hosts or lighter weight protocols.  A client MAY look at records
    ///      with higher preference values if it has a good reason to do so
    ///      such as not supporting some protocol or service very well.
    ///
    ///      The important difference between Order and Preference is that once
    ///      a match is found the client MUST NOT consider records with a
    ///      different Order but they MAY process records with the same Order
    ///      but different Preferences.  The only exception to this is noted in
    ///      the second important Note in the DDDS algorithm specification
    ///      concerning allowing clients to use more complex Service
    ///      determination between steps 3 and 4 in the algorithm.  Preference
    ///      is used to give communicate a higher quality of service to rules
    ///      that are considered the same from an authority standpoint but not
    ///      from a simple load balancing standpoint.
    ///
    ///      It is important to note that DNS contains several load balancing
    ///      mechanisms and if load balancing among otherwise equal services
    ///      should be needed then methods such as SRV records or multiple A
    ///      records should be utilized to accomplish load balancing.
    /// ```
    pub fn preference(&self) -> u16 {
        self.preference
    }

    /// ```text
    ///   FLAGS
    ///      A <character-string> containing flags to control aspects of the
    ///      rewriting and interpretation of the fields in the record.  Flags
    ///      are single characters from the set A-Z and 0-9.  The case of the
    ///      alphabetic characters is not significant.  The field can be empty.
    ///
    ///      It is up to the Application specifying how it is using this
    ///      Database to define the Flags in this field.  It must define which
    ///      ones are terminal and which ones are not.
    /// ```
    pub fn flags(&self) -> &[u8] {
        &self.flags
    }

    /// ```text
    ///   SERVICES
    ///      A <character-string> that specifies the Service Parameters
    ///      applicable to this this delegation path.  It is up to the
    ///      Application Specification to specify the values found in this
    ///      field.
    /// ```
    pub fn services(&self) -> &[u8] {
        &self.services
    }

    /// ```text
    ///   REGEXP
    ///      A <character-string> containing a substitution expression that is
    ///      applied to the original string held by the client in order to
    ///      construct the next domain name to lookup.  See the DDDS Algorithm
    ///      specification for the syntax of this field.
    ///
    ///      As stated in the DDDS algorithm, The regular expressions MUST NOT
    ///      be used in a cumulative fashion, that is, they should only be
    ///      applied to the original string held by the client, never to the
    ///      domain name p  roduced by a previous NAPTR rewrite.  The latter is
    ///      tempting in some applications but experience has shown such use to
    ///      be extremely fault sensitive, very error prone, and extremely
    ///      difficult to debug.
    /// ```
    pub fn regexp(&self) -> &[u8] {
        &self.regexp
    }

    /// ```text
    ///   REPLACEMENT
    ///      A <domain-name> which is the next domain-name to query for
    ///      depending on the potential values found in the flags field.  This
    ///      field is used when the regular expression is a simple replacement
    ///      operation.  Any value in this field MUST be a fully qualified
    ///      domain-name.  Name compression is not to be used for this field.
    ///
    ///      This field and the REGEXP field together make up the Substitution
    ///      Expression in the DDDS Algorithm.  It is simply a historical
    ///      optimization specifically for DNS compression that this field
    ///      exists.  The fields are also mutually exclusive.  If a record is
    ///      returned that has values for both fields then it is considered to
    ///      be in error and SHOULD be either ignored or an error returned.
    /// ```
    pub fn replacement(&self) -> &Name {
        &self.replacement
    }
}

/// verifies that the flags are valid
pub fn verify_flags(flags: &[u8]) -> bool {
    flags.iter().all(|c| match c {
        b'0'...b'9' => true,
        b'a'...b'z' => true,
        b'A'...b'Z' => true,
        _ => false,
    })
}

/// Read the RData from the given Decoder
pub fn read(decoder: &mut BinDecoder) -> ProtoResult<NAPTR> {
    Ok(NAPTR::new(
        decoder.read_u16()?.unverified(/*any u16 is valid*/),
        decoder.read_u16()?.unverified(/*any u16 is valid*/),
        // must be 0-9a-z
        decoder
            .read_character_data()?
            .verify_unwrap(|s| verify_flags(s))
            .map_err(|_e| ProtoError::from("flags are not within range [a-zA-Z0-9]"))?
            .to_vec()
            .into_boxed_slice(),
        decoder.read_character_data()?.unverified(/*any chardata*/).to_vec().into_boxed_slice(),
        decoder.read_character_data()?.unverified(/*any chardata*/).to_vec().into_boxed_slice(),
        Name::read(decoder)?,
    ))
}

/// Declares the method for emiting this type
pub fn emit(encoder: &mut BinEncoder, naptr: &NAPTR) -> ProtoResult<()> {
    naptr.order.emit(encoder)?;
    naptr.preference.emit(encoder)?;
    encoder.emit_character_data(&naptr.flags)?;
    encoder.emit_character_data(&naptr.services)?;
    encoder.emit_character_data(&naptr.regexp)?;

    encoder.with_canonical_names(|encoder| naptr.replacement.emit(encoder))?;
    Ok(())
}

#[test]
pub fn test() {
    use std::str::FromStr;

    let rdata = NAPTR::new(
        8,
        16,
        b"aa11AA".to_vec().into_boxed_slice(),
        b"services".to_vec().into_boxed_slice(),
        b"regexpr".to_vec().into_boxed_slice(),
        Name::from_str("naptr.example.com").unwrap(),
    );

    let mut bytes = Vec::new();
    let mut encoder: BinEncoder = BinEncoder::new(&mut bytes);
    assert!(emit(&mut encoder, &rdata).is_ok());
    let bytes = encoder.into_bytes();

    println!("bytes: {:?}", bytes);

    let mut decoder: BinDecoder = BinDecoder::new(bytes);
    let read_rdata = read(&mut decoder);
    assert!(
        read_rdata.is_ok(),
        format!("error decoding: {:?}", read_rdata.unwrap_err())
    );
    assert_eq!(rdata, read_rdata.unwrap());
}

#[test]
pub fn test_bad_data() {
    use std::str::FromStr;

    let rdata = NAPTR::new(
        8,
        16,
        b"aa11AA-".to_vec().into_boxed_slice(),
        b"services".to_vec().into_boxed_slice(),
        b"regexpr".to_vec().into_boxed_slice(),
        Name::from_str("naptr.example.com").unwrap(),
    );

    let mut bytes = Vec::new();
    let mut encoder: BinEncoder = BinEncoder::new(&mut bytes);
    assert!(emit(&mut encoder, &rdata).is_ok());
    let bytes = encoder.into_bytes();

    println!("bytes: {:?}", bytes);

    let mut decoder: BinDecoder = BinDecoder::new(bytes);
    let read_rdata = read(&mut decoder);
    assert!(
        read_rdata.is_err(),
        "should have failed decoding with bad flag data"
    );
}