use crate::models::DNSQuery;
use crate::models::DNSResponse;
use crate::proto::Coder;

pub struct UdpCoder {}


impl Coder for UdpCoder {
    fn decode(datagram: &[u8]) -> Result<DNSQuery, DNSParseError> {
        let message = Message::try_from(datagram)?;
        Ok(DNSQuery {
            id: message.header.id,
            questions: vec![],
        })

    }
    
    fn encode(respone: DNSResponse) -> Result<Vec<u8>, DNSParseError> {
        todo!();
    }
}

#[derive(Debug, Clone, PartialEq)]
pub enum DNSParseError {
    DatagramTooShort
}

#[derive(Debug, PartialEq, Clone, Copy)]
enum MessageType {
    Query,
    Response,
}

impl From<bool> for MessageType {
    fn from(value: bool) -> MessageType {
        match value {
            false => Self::Query,
            true => Self::Response,
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
struct Header {
    /// used by the requester to match up replies to outstanding queries
    id: u16,
    /// specifies whether this message is a query or a response
    message_type: MessageType,
    opcode: u8,
    /// specifies that the responding name server is an authority for the domain name in question section
    authorative_answer: bool,
    /// specifies that this message was truncated due to length greater than that permitted on the transmission channel
    truncated: bool,
    /// it directs the name server to pursue the query recursively
    recursion_desired: bool,
    /// denotes whether recursive query support is available in the name server
    recursion_available: bool,
    // no support of rfc4035 at the moment
    //pub authentic_data: bool,
    // no support of rfc4035 at the moment
    //pub checking_disabled: bool,
    response_code: u8,
    /// TODO: add documuentation about this count
    query_count: u16,
    /// TODO: add documuentation about this count
    answer_count: u16,
    /// TODO: add documuentation about this count
    name_server_count: u16,
    /// TODO: add documuentation about this count
    additional_count: u16,
}

#[derive(Debug, Clone)]
struct Question {
    name: String,
    r#type: u16,
    class: u16,
}

#[derive(Debug, Clone)]
struct ResourceRecord {
    name: String,
    r#type: u16,
    class: u16,
    ttl: u32,
    data: String,
}

#[derive(Debug, Clone)]
pub struct Message {
    header: Header,
    questions: Vec<Question>,
    answers: Vec<ResourceRecord>,
    authorities: Vec<ResourceRecord>,
    additionals: Vec<ResourceRecord>,
}

impl TryFrom<&[u8]> for Message {
    type Error = DNSParseError;

    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
        todo!();
    }
}

impl TryFrom<&[u8]> for Header {
    type Error = DNSParseError;

    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
        const QR_MASK: u8 = 0b10000000;
        const OPCODE_MASK: u8 = 0b01111000;
        const AA_MASK: u8 = 0b00000100;
        const TC_MASK: u8 = 0b00000010;
        const RD_MASK: u8 = 0b00000001;

        const RA_MASK: u8 = 0b10000000;
        // no support of rfc4035 at the moment
        //const AD_MASK: u8 = 0b00100000;
        //const CD_MASK: u8 = 0b00010000;
        const RCODE_MASK: u8 = 0b00001111;

        const OPCODE_OFFSET: u8 = 3;

        if value.len() < 12 {
            return Err(DNSParseError::DatagramTooShort);
        }

        let id = u16::from_be_bytes((&value[..2]).try_into().unwrap());

        let message_type = MessageType::from(value[2] & QR_MASK != 0);
        let opcode =(value[2] & OPCODE_MASK) >> OPCODE_OFFSET;

        let authorative_answer = (value[2] & AA_MASK) != 0;
        let truncated = (value[2] & TC_MASK) != 0;
        let recursion_desired = (value[2] & RD_MASK) != 0;
        let recursion_available = (value[3] & RA_MASK) != 0;

        // no support for rfc4035 at the moment
        //let authentic_data = (datagram[2] & AD_MASK) != 0;
        //let checking_disabled = (datagram[2] & CD_MASK) != 0;

        let response_code = value[3] & RCODE_MASK;
        let query_count = u16::from_be_bytes((value[4..6]).try_into().unwrap());
        let answer_count = u16::from_be_bytes((value[6..8]).try_into().unwrap());
        let name_server_count = u16::from_be_bytes((value[8..10]).try_into().unwrap());
        let additional_count = u16::from_be_bytes((value[10..12]).try_into().unwrap());

        Ok(Header {
            id,
            message_type,
            opcode,
            authorative_answer,
            truncated,
            recursion_desired,
            recursion_available,
            //authentic_data,    // no support of rfc4035 at the moment
            //checking_disabled, // no support of rfc4035 at the moment
            response_code,
            query_count,
            answer_count,
            name_server_count,
            additional_count,
        })
    }
}