use std::io::Error;
use std::mem::size_of;
use std::fmt::Debug;

use log::trace;
use crc32c;

use kf_protocol::bytes::Buf;
use kf_protocol::bytes::BufMut;

use kf_protocol::Decoder;
use kf_protocol::Encoder;
use kf_protocol::Version;
use kf_protocol_derive::Decode;

use crate::Offset;
use crate::Size;
use super::DefaultRecord;

pub type DefaultBatchRecords = Vec<DefaultRecord>;
pub type DefaultBatch = Batch<DefaultBatchRecords>;


pub trait BatchRecords: Default + Debug + Encoder + Decoder {

    /// how many bytes does record wants to process
    fn remainder_bytes(&self,remainder: usize ) -> usize {
        remainder
    }

}


impl BatchRecords for DefaultBatchRecords {}



/// size of the offset and length
pub const BATCH_PREAMBLE_SIZE: usize =  
        size_of::<Offset>()     // Offset
        + size_of::<i32>();       // i32


#[derive(Default,Debug)]
pub struct Batch<R> where R: BatchRecords {
    pub base_offset: Offset,
    pub batch_len: i32,       // only for decoding
    pub header: BatchHeader,
    pub records: R
}

impl <R>Batch<R> where R: BatchRecords {

    pub fn get_mut_header(&mut self) -> &mut BatchHeader {
        &mut self.header
    }

    pub fn get_header(&self) -> &BatchHeader {
        &self.header
    }

    pub fn get_base_offset(&self) -> Offset {
        self.base_offset
    }

    pub fn set_base_offset(&mut self,offset: Offset)  {
        self.base_offset = offset;
    }

    pub fn base_offset(mut self, offset: Offset) -> Self {
        self.base_offset = offset;
        self
    }

    pub fn set_offset_delta(&mut self,delta: i32) {
        self.header.last_offset_delta = delta;
    }

    pub fn get_last_offset(&self) -> Offset {
        self.get_base_offset() + self.get_last_offset_delta() as Offset
    }
    

    /// get last offset delta
    pub fn get_last_offset_delta(&self) -> Size {
        self.get_header().last_offset_delta as Size
    }

    /// decode from buf stored in the file
    /// read all excluding records
    pub fn decode_from_file_buf<T>(&mut self, src: &mut T,version: Version) -> Result<(), Error> where T: Buf,
    {
        trace!("decoding premable");
        self.base_offset.decode(src,version)?;
        self.batch_len.decode(src,version)?;
        self.header.decode(src,version)?;
        Ok(())
    }


}




impl Batch<DefaultBatchRecords>  {


    /// add new record, this will update the offset to correct
    pub fn add_record(&mut self,mut record: DefaultRecord) {
        let last_offset_delta = if self.records.len() == 0 { 0 } else { self.records.len() as Offset };
        record.preamble.set_offset_delta(last_offset_delta);
        self.header.last_offset_delta = last_offset_delta as i32;
        self.records.push(record)
    }

}



impl <R>Decoder for Batch<R> where R: BatchRecords  {

    fn decode<T>(&mut self, src: &mut T,version: Version) -> Result<(), Error> where T: Buf,
    {
        trace!("decoding batch");
        self.decode_from_file_buf(src,version)?;
        self.records.decode(src,version)?;
        Ok(())
    }
}



// Record batch contains 12 bytes of pre-amble plus header + records
impl <R>Encoder for Batch<R>  where R: BatchRecords {

    fn write_size(&self,version: Version) -> usize {
        BATCH_PREAMBLE_SIZE + BATCH_HEADER_SIZE + self.records.write_size(version)
    }

    fn encode<T>(&self, dest: &mut T,version: Version) -> Result<(), Error> where T: BufMut
    {
        trace!("Encoding Batch");
        self.base_offset.encode(dest,version)?;
        let batch_len: i32 = (BATCH_HEADER_SIZE + self.records.write_size(version)) as i32;
        batch_len.encode(dest,version)?;

        // encode parts of header
        self.header.partition_leader_epoch.encode(dest,version)?;
        self.header.magic.encode(dest,version)?;


        let mut out: Vec<u8> = Vec::new();
        let buf = &mut out;
        self.header.attributes.encode(buf,version)?;
        self.header.last_offset_delta.encode(buf,version)?;
        self.header.first_timestamp.encode(buf,version)?;
        self.header.max_time_stamp.encode(buf,version)?;
        self.header.producer_id.encode(buf,version)?;
        self.header.producer_epoch.encode(buf,version)?;
        self.header.first_sequence.encode(buf,version)?;
        self.records.encode(buf,version)?;

        let crc = crc32c::crc32c(&out);
        crc.encode(dest,version)?;
        dest.put_slice(&out);        
        Ok(())
    }
}


#[derive(Debug,Decode)]
pub struct BatchHeader {
    pub partition_leader_epoch: i32,
    pub magic: i8,
    pub crc: u32,
    pub attributes: i16,
    pub last_offset_delta: i32,
    pub first_timestamp: i64,
    pub max_time_stamp: i64,
    pub producer_id: i64,
    pub producer_epoch: i16,
    pub first_sequence: i32,
}


impl Default for BatchHeader {  

    fn default() -> Self {
        BatchHeader {
            partition_leader_epoch: -1,
            magic: 2,
            crc: 0,
            attributes: 0,
            last_offset_delta: 0,
            first_timestamp: 0,
            max_time_stamp: 0,
            producer_id: -1,
            producer_epoch: -1,
            first_sequence: -1,
        }
    }

}

#[allow(dead_code)]
pub const BATCH_HEADER_SIZE: usize =  
        size_of::<i32>()     // partition leader epoch
        + size_of::<u8>()       // magic
        + size_of::<i32>()      //crc
        + size_of::<i16>()      // i16
        + size_of::<i32>()      // last offset delta
        + size_of::<i64>()      // first_timestamp
        + size_of::<i64>()      // max_time_stamp
        + size_of::<i64>()      //producer id
        + size_of::<i16>()      // produce_epoch
        + size_of::<i32>();      // first sequence



#[cfg(test)]
mod test {

   
    use std::io::Cursor;
    use std::io::Error as IoError;

    use kf_protocol::Decoder;
    use kf_protocol::Encoder;

    use crate::DefaultRecord;
    use crate::DefaultBatch;
    

    #[test]
    fn test_encode_and_decode_batch() -> Result<(),IoError> {

        let record: DefaultRecord = vec![0x74,0x65,0x73,0x74].into();
        let mut batch = DefaultBatch::default();
        batch.records.push(record);
        batch.header.first_timestamp = 1555478494747;
        batch.header.max_time_stamp = 1555478494747;

        let bytes = batch.as_bytes(0)?;
        println!("batch raw bytes: {:#X?}",bytes.as_ref());

        let batch = DefaultBatch::decode_from(&mut Cursor::new(bytes),0)?;
        println!("batch: {:#?}",batch);
        
        let decoded_record = batch.records.get(0).unwrap();
        println!("record crc: {}",batch.header.crc);
        assert_eq!(batch.header.crc, 1514417201);
        if let Some(ref b) = decoded_record.value.inner_value_ref() {
            assert_eq!(b.as_slice(),"test".to_owned().as_bytes());
        } else {
            assert!(false);
        }
        
        
        Ok(())

    }

    /*  raw batch encoded

    0000   02 00 00 00 45 00 00 c7 00 00 40 00 40 06 00 00
    0010   c0 a8 07 30 c0 a8 07 30 d1 b9 23 84 29 ba 3d 48
    0020   0b 13 89 98 80 18 97 62 90 6a 00 00 01 01 08 0a
    0030   1e 6f 09 0d 1e 6f 09 06 00 00 00 8f 00 00 00 05
    0040   00 00 00 03 00 10 63 6f 6e 73 6f 6c 65 2d 70 72
    0050   6f 64 75 63 65 72 ff ff 00 01 00 00 05 dc 00 00
    0060   00 01 00 13 6d 79 2d 72 65 70 6c 69 63 61 74 65
    0070   64 2d 74 6f 70 69 63 00 00 00 01 00 00 00 00 00
    0080   00 00 48 00 00 00 00 00 00 00 00 00 00 00 3c ff
    0090   ff ff ff 02 5a 44 2c 31 00 00 00 00 00 00 00 00
    00a0   01 6a 29 be 3e 1b 00 00 01 6a 29 be 3e 1b ff ff
    00b0   ff ff ff ff ff ff ff ff ff ff ff ff 00 00 00 01
    00c0   14 00 00 00 01 08 74 65 73 74 00
    */

    #[test]
    fn test_records_offset() {

        let mut batch = DefaultBatch::default();

        batch.add_record(DefaultRecord::default());
        batch.add_record(DefaultRecord::default());
        batch.add_record(DefaultRecord::default());

        assert_eq!(batch.records.get(0).expect("index 0 should exists").get_offset_delta(),0);
        assert_eq!(batch.records.get(1).expect("index 1 should exists").get_offset_delta(),1);
        assert_eq!(batch.records.get(2).expect("index 2 should exists").get_offset_delta(),2);
        assert_eq!(batch.get_last_offset_delta(),2);

    }


}