use crate::filechunkread::FileChunkRead;
use crate::needminbuffer::NeedMinBuffer;
use bitshuffle::bitshuffle_decompress;
use bytes::{Buf, BytesMut};
use err::Error;
use futures_util::{Stream, StreamExt};
use items::eventfull::EventFull;
use items::{
     RangeCompletableItem, StatsItem,
    StreamItem, WithLen,
};
use netpod::histo::HistoLog2;
use netpod::log::*;
use netpod::timeunits::SEC;
use netpod::{ByteSize, ChannelConfig, EventDataReadStats, NanoRange, ScalarType, Shape};
use parse::channelconfig::CompressionMethod;
use std::path::PathBuf;
use std::pin::Pin;
use std::task::{Context, Poll};
use std::time::Instant;

pub struct EventChunker {
    inp: NeedMinBuffer,
    state: DataFileState,
    need_min: u32,
    channel_config: ChannelConfig,
    errored: bool,
    completed: bool,
    range: NanoRange,
    stats_conf: EventChunkerConf,
    seen_beyond_range: bool,
    sent_beyond_range: bool,
    data_emit_complete: bool,
    final_stats_sent: bool,
    parsed_bytes: u64,
    dbg_path: PathBuf,
    max_ts: u64,
    expand: bool,
    do_decompress: bool,
    decomp_dt_histo: HistoLog2,
    item_len_emit_histo: HistoLog2,
    seen_before_range_count: usize,
    seen_after_range_count: usize,
    unordered_warn_count: usize,
    repeated_ts_warn_count: usize,
}

impl Drop for EventChunker {
    fn drop(&mut self) {
        // TODO collect somewhere
        debug!(
            "EventChunker  Drop Stats:\ndecomp_dt_histo: {:?}\nitem_len_emit_histo: {:?}",
            self.decomp_dt_histo, self.item_len_emit_histo
        );
    }
}

enum DataFileState {
    FileHeader,
    Event,
}

struct ParseResult {
    events: EventFull,
    parsed_bytes: u64,
}

#[derive(Clone, Debug)]
pub struct EventChunkerConf {
    pub disk_stats_every: ByteSize,
}

impl EventChunkerConf {
    pub fn new(disk_stats_every: ByteSize) -> Self {
        Self { disk_stats_every }
    }
}

impl EventChunker {
    // TODO   `expand` flag usage
    pub fn from_start(
        inp: Pin<Box<dyn Stream<Item = Result<FileChunkRead, Error>> + Send>>,
        channel_config: ChannelConfig,
        range: NanoRange,
        stats_conf: EventChunkerConf,
        dbg_path: PathBuf,
        expand: bool,
        do_decompress: bool,
    ) -> Self {
        trace!("EventChunker::from_start");
        let mut inp = NeedMinBuffer::new(inp);
        inp.set_need_min(6);
        Self {
            inp,
            state: DataFileState::FileHeader,
            need_min: 6,
            channel_config,
            errored: false,
            completed: false,
            range,
            stats_conf,
            seen_beyond_range: false,
            sent_beyond_range: false,
            data_emit_complete: false,
            final_stats_sent: false,
            parsed_bytes: 0,
            dbg_path,
            max_ts: 0,
            expand,
            do_decompress,
            decomp_dt_histo: HistoLog2::new(8),
            item_len_emit_histo: HistoLog2::new(0),
            seen_before_range_count: 0,
            seen_after_range_count: 0,
            unordered_warn_count: 0,
            repeated_ts_warn_count: 0,
        }
    }

    // TODO   `expand` flag usage
    pub fn from_event_boundary(
        inp: Pin<Box<dyn Stream<Item = Result<FileChunkRead, Error>> + Send>>,
        channel_config: ChannelConfig,
        range: NanoRange,
        stats_conf: EventChunkerConf,
        dbg_path: PathBuf,
        expand: bool,
        do_decompress: bool,
    ) -> Self {
        let mut ret = Self::from_start(inp, channel_config, range, stats_conf, dbg_path, expand, do_decompress);
        ret.state = DataFileState::Event;
        ret.need_min = 4;
        ret.inp.set_need_min(4);
        ret
    }

    fn parse_buf(&mut self, buf: &mut BytesMut) -> Result<ParseResult, Error> {
        span!(Level::INFO, "EventChunker::parse_buf").in_scope(|| self.parse_buf_inner(buf))
    }

    fn parse_buf_inner(&mut self, buf: &mut BytesMut) -> Result<ParseResult, Error> {
        let mut ret = EventFull::empty();
        let mut parsed_bytes = 0;
        use byteorder::{ReadBytesExt, BE};
        loop {
            if (buf.len() as u32) < self.need_min {
                break;
            }
            match self.state {
                DataFileState::FileHeader => {
                    if buf.len() < 6 {
                        Err(Error::with_msg("need min 6 for FileHeader"))?;
                    }
                    let mut sl = std::io::Cursor::new(buf.as_ref());
                    let fver = sl.read_i16::<BE>().unwrap();
                    if fver != 0 {
                        Err(Error::with_msg("unexpected data file version"))?;
                    }
                    let len = sl.read_i32::<BE>().unwrap();
                    if len <= 0 || len >= 128 {
                        Err(Error::with_msg("large channel header len"))?;
                    }
                    let totlen = len as usize + 2;
                    if buf.len() < totlen {
                        self.need_min = totlen as u32;
                        break;
                    } else {
                        sl.advance(len as usize - 8);
                        let len2 = sl.read_i32::<BE>().unwrap();
                        if len != len2 {
                            Err(Error::with_msg("channel header len mismatch"))?;
                        }
                        String::from_utf8(buf.as_ref()[6..(len as usize + 6 - 8)].to_vec())?;
                        self.state = DataFileState::Event;
                        self.need_min = 4;
                        buf.advance(totlen);
                        parsed_bytes += totlen as u64;
                    }
                }
                DataFileState::Event => {
                    let p0 = 0;
                    let mut sl = std::io::Cursor::new(buf.as_ref());
                    let len = sl.read_i32::<BE>().unwrap();
                    if len < 20 || len > 1024 * 1024 * 20 {
                        Err(Error::with_msg("unexpected large event chunk"))?;
                    }
                    let len = len as u32;
                    if (buf.len() as u32) < len {
                        self.need_min = len as u32;
                        break;
                    } else {
                        let mut sl = std::io::Cursor::new(buf.as_ref());
                        let len1b = sl.read_i32::<BE>().unwrap();
                        assert!(len == len1b as u32);
                        let _ttl = sl.read_i64::<BE>().unwrap();
                        let ts = sl.read_i64::<BE>().unwrap() as u64;
                        let pulse = sl.read_i64::<BE>().unwrap() as u64;
                        if ts == self.max_ts {
                            if self.repeated_ts_warn_count < 20 {
                                let msg = format!(
                                    "EventChunker  repeated event ts ix {}  ts {}.{}  max_ts {}.{}  config {:?}  path {:?}",
                                    self.repeated_ts_warn_count,
                                    ts / SEC,
                                    ts % SEC,
                                    self.max_ts / SEC,
                                    self.max_ts % SEC,
                                    self.channel_config.shape,
                                    self.dbg_path
                                );
                                warn!("{}", msg);
                                self.repeated_ts_warn_count += 1;
                            }
                        }
                        if ts < self.max_ts {
                            if self.unordered_warn_count < 20 {
                                let msg = format!(
                                    "EventChunker  unordered event ix {}  ts {}.{}  max_ts {}.{}  config {:?}  path {:?}",
                                    self.unordered_warn_count,
                                    ts / SEC,
                                    ts % SEC,
                                    self.max_ts / SEC,
                                    self.max_ts % SEC,
                                    self.channel_config.shape,
                                    self.dbg_path
                                );
                                warn!("{}", msg);
                                self.unordered_warn_count += 1;
                                let e = Error::with_public_msg_no_trace(msg);
                                return Err(e);
                            }
                        }
                        self.max_ts = ts;
                        if ts >= self.range.end {
                            self.seen_after_range_count += 1;
                            if !self.expand || self.seen_after_range_count >= 2 {
                                self.seen_beyond_range = true;
                                self.data_emit_complete = true;
                                break;
                            }
                        }
                        if ts < self.range.beg {
                            self.seen_before_range_count += 1;
                            if self.seen_before_range_count > 1 {
                                let msg = format!(
                                    "seen before range: event ts {}.{}  range beg {}.{}  range end {}.{}  pulse {}  config {:?}  path {:?}",
                                    ts / SEC,
                                    ts % SEC,
                                    self.range.beg / SEC,
                                    self.range.beg % SEC,
                                    self.range.end / SEC,
                                    self.range.end % SEC,
                                    pulse,
                                    self.channel_config.shape,
                                    self.dbg_path
                                );
                                warn!("{}", msg);
                                let e = Error::with_public_msg(msg);
                                Err(e)?;
                            }
                        }
                        let _ioc_ts = sl.read_i64::<BE>().unwrap();
                        let status = sl.read_i8().unwrap();
                        let severity = sl.read_i8().unwrap();
                        let optional = sl.read_i32::<BE>().unwrap();
                        if status != 0 {
                            Err(Error::with_msg(format!("status != 0: {}", status)))?;
                        }
                        if severity != 0 {
                            Err(Error::with_msg(format!("severity != 0: {}", severity)))?;
                        }
                        if optional != -1 {
                            Err(Error::with_msg(format!("optional != -1: {}", optional)))?;
                        }
                        let type_flags = sl.read_u8().unwrap();
                        let type_index = sl.read_u8().unwrap();
                        if type_index > 13 {
                            Err(Error::with_msg(format!("type_index: {}", type_index)))?;
                        }
                        let scalar_type = ScalarType::from_dtype_index(type_index)?;
                        use super::dtflags::*;
                        let is_compressed = type_flags & COMPRESSION != 0;
                        let is_array = type_flags & ARRAY != 0;
                        let is_big_endian = type_flags & BIG_ENDIAN != 0;
                        let is_shaped = type_flags & SHAPE != 0;
                        if let Shape::Wave(_) = self.channel_config.shape {
                            if !is_array {
                                Err(Error::with_msg(format!("dim1 but not array {:?}", self.channel_config)))?;
                            }
                        }
                        let compression_method = if is_compressed { sl.read_u8().unwrap() } else { 0 };
                        let shape_dim = if is_shaped { sl.read_u8().unwrap() } else { 0 };
                        assert!(compression_method <= 0);
                        assert!(!is_shaped || (shape_dim >= 1 && shape_dim <= 2));
                        let mut shape_lens = [0, 0, 0, 0];
                        for i1 in 0..shape_dim {
                            shape_lens[i1 as usize] = sl.read_u32::<BE>().unwrap();
                        }
                        let shape_this = {
                            if is_shaped {
                                if shape_dim == 1 {
                                    Shape::Wave(shape_lens[0])
                                } else if shape_dim == 2 {
                                    Shape::Image(shape_lens[0], shape_lens[1])
                                } else {
                                    err::todoval()
                                }
                            } else {
                                Shape::Scalar
                            }
                        };
                        let comp_this = if is_compressed {
                            if compression_method == 0 {
                                Some(CompressionMethod::BitshuffleLZ4)
                            } else {
                                err::todoval()
                            }
                        } else {
                            None
                        };
                        let p1 = sl.position();
                        let k1 = len as u64 - (p1 - p0) - 4;
                        if is_compressed {
                            //debug!("event  ts {}  is_compressed {}", ts, is_compressed);
                            let value_bytes = sl.read_u64::<BE>().unwrap();
                            let block_size = sl.read_u32::<BE>().unwrap();
                            //debug!("event  len {}  ts {}  is_compressed {}  shape_dim {}  len-dim-0 {}  value_bytes {}  block_size {}", len, ts, is_compressed, shape_dim, shape_lens[0], value_bytes, block_size);
                            match self.channel_config.shape {
                                Shape::Scalar => {
                                    assert!(value_bytes < 1024 * 1);
                                }
                                Shape::Wave(_) => {
                                    assert!(value_bytes < 1024 * 64);
                                }
                                Shape::Image(_, _) => {
                                    assert!(value_bytes < 1024 * 1024 * 20);
                                }
                            }
                            assert!(block_size <= 1024 * 32);
                            let type_size = scalar_type.bytes() as u32;
                            let ele_count = value_bytes / type_size as u64;
                            let ele_size = type_size;
                            match self.channel_config.shape {
                                Shape::Scalar => {
                                    if is_array {
                                        Err(Error::with_msg(format!(
                                            "ChannelConfig expects Scalar but we find event is_array"
                                        )))?;
                                    }
                                }
                                Shape::Wave(dim1count) => {
                                    if dim1count != ele_count as u32 {
                                        Err(Error::with_msg(format!(
                                            "ChannelConfig expects {:?} but event has ele_count {}",
                                            self.channel_config.shape, ele_count,
                                        )))?;
                                    }
                                }
                                Shape::Image(n1, n2) => {
                                    let nt = n1 as usize * n2 as usize;
                                    if nt != ele_count as usize {
                                        Err(Error::with_msg(format!(
                                            "ChannelConfig expects {:?} but event has ele_count {}",
                                            self.channel_config.shape, ele_count,
                                        )))?;
                                    }
                                }
                            }
                            let decomp = {
                                if self.do_decompress {
                                    let ts1 = Instant::now();
                                    let decomp_bytes = (type_size * ele_count as u32) as usize;
                                    let mut decomp = BytesMut::with_capacity(decomp_bytes);
                                    unsafe {
                                        decomp.set_len(decomp_bytes);
                                    }
                                    // TODO limit the buf slice range
                                    match bitshuffle_decompress(
                                        &buf.as_ref()[(p1 as usize + 12)..(p1 as usize + k1 as usize)],
                                        &mut decomp,
                                        ele_count as usize,
                                        ele_size as usize,
                                        0,
                                    ) {
                                        Ok(c1) => {
                                            assert!(c1 as u64 + 12 == k1);
                                            let ts2 = Instant::now();
                                            let dt = ts2.duration_since(ts1);
                                            self.decomp_dt_histo.ingest(dt.as_secs() as u32 + dt.subsec_micros());
                                            Some(decomp)
                                        }
                                        Err(e) => {
                                            return Err(Error::with_msg(format!("decompression failed {:?}", e)))?;
                                        }
                                    }
                                } else {
                                    None
                                }
                            };
                            ret.add_event(
                                ts,
                                pulse,
                                buf.as_ref()[(p1 as usize)..(p1 as usize + k1 as usize)].to_vec(),
                                decomp,
                                ScalarType::from_dtype_index(type_index)?,
                                is_big_endian,
                                shape_this,
                                comp_this,
                            );
                        } else {
                            if len < p1 as u32 + 4 {
                                let msg = format!("uncomp  len: {}  p1: {}", len, p1);
                                Err(Error::with_msg(msg))?;
                            }
                            let vlen = len - p1 as u32 - 4;
                            // TODO in this case, decomp and comp is the same and not needed.
                            let decomp = BytesMut::from(&buf[p1 as usize..(p1 as u32 + vlen) as usize]);
                            ret.add_event(
                                ts,
                                pulse,
                                buf.as_ref()[(p1 as usize)..(p1 as usize + k1 as usize)].to_vec(),
                                Some(decomp),
                                ScalarType::from_dtype_index(type_index)?,
                                is_big_endian,
                                shape_this,
                                comp_this,
                            );
                        }
                        buf.advance(len as usize);
                        parsed_bytes += len as u64;
                        self.need_min = 4;
                    }
                }
            }
        }
        Ok(ParseResult {
            events: ret,
            parsed_bytes,
        })
    }
}

impl Stream for EventChunker {
    type Item = Result<StreamItem<RangeCompletableItem<EventFull>>, Error>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
        use Poll::*;
        'outer: loop {
            break if self.completed {
                panic!("EventChunker poll_next on completed");
            } else if self.errored {
                self.completed = true;
                Ready(None)
            } else if self.parsed_bytes >= self.stats_conf.disk_stats_every.bytes() as u64 {
                let item = EventDataReadStats {
                    parsed_bytes: self.parsed_bytes,
                };
                self.parsed_bytes = 0;
                let ret = StreamItem::Stats(StatsItem::EventDataReadStats(item));
                Ready(Some(Ok(ret)))
            } else if self.sent_beyond_range {
                self.completed = true;
                Ready(None)
            } else if self.final_stats_sent {
                self.sent_beyond_range = true;
                trace!("sent_beyond_range");
                if self.seen_beyond_range {
                    trace!("sent_beyond_range  RangeComplete");
                    Ready(Some(Ok(StreamItem::DataItem(RangeCompletableItem::RangeComplete))))
                } else {
                    trace!("sent_beyond_range  non-complete");
                    continue 'outer;
                }
            } else if self.data_emit_complete {
                let item = EventDataReadStats {
                    parsed_bytes: self.parsed_bytes,
                };
                self.parsed_bytes = 0;
                let ret = StreamItem::Stats(StatsItem::EventDataReadStats(item));
                self.final_stats_sent = true;
                Ready(Some(Ok(ret)))
            } else {
                match self.inp.poll_next_unpin(cx) {
                    Ready(Some(Ok(mut fcr))) => {
                        if false {
                            // TODO collect for stats:
                            info!(
                                "file read  bytes {}  ms {}",
                                fcr.buf().len(),
                                fcr.duration().as_millis()
                            );
                        }
                        let r = self.parse_buf(fcr.buf_mut());
                        match r {
                            Ok(res) => {
                                self.parsed_bytes += res.parsed_bytes;
                                if fcr.buf().len() > 0 {
                                    // TODO gather stats about this:
                                    self.inp.put_back(fcr);
                                }
                                match self.channel_config.shape {
                                    Shape::Scalar => {
                                        if self.need_min > 1024 * 8 {
                                            let msg =
                                                format!("spurious EventChunker asks for need_min {}", self.need_min);
                                            self.errored = true;
                                            return Ready(Some(Err(Error::with_msg(msg))));
                                        }
                                    }
                                    Shape::Wave(_) => {
                                        if self.need_min > 1024 * 32 {
                                            let msg =
                                                format!("spurious EventChunker asks for need_min {}", self.need_min);
                                            self.errored = true;
                                            return Ready(Some(Err(Error::with_msg(msg))));
                                        }
                                    }
                                    Shape::Image(_, _) => {
                                        if self.need_min > 1024 * 1024 * 20 {
                                            let msg =
                                                format!("spurious EventChunker asks for need_min {}", self.need_min);
                                            self.errored = true;
                                            return Ready(Some(Err(Error::with_msg(msg))));
                                        }
                                    }
                                }
                                let x = self.need_min;
                                self.inp.set_need_min(x);
                                if false {
                                    info!(
                                        "EventChunker  emits {} events  tss {:?}",
                                        res.events.len(),
                                        res.events.tss
                                    );
                                };
                                self.item_len_emit_histo.ingest(res.events.len() as u32);
                                let ret = StreamItem::DataItem(RangeCompletableItem::Data(res.events));
                                Ready(Some(Ok(ret)))
                            }
                            Err(e) => {
                                self.errored = true;
                                Ready(Some(Err(e.into())))
                            }
                        }
                    }
                    Ready(Some(Err(e))) => {
                        self.errored = true;
                        Ready(Some(Err(e)))
                    }
                    Ready(None) => {
                        self.data_emit_complete = true;
                        continue 'outer;
                    }
                    Pending => Pending,
                }
            };
        }
    }
}

#[cfg(test)]
mod test {
    //use err::Error;
    //use netpod::timeunits::*;
    //use netpod::{ByteSize, Nanos};

    /*
    #[test]
    fn read_expanded_for_range(range: netpod::NanoRange, nodeix: usize) -> Result<(usize, usize), Error> {
        let chn = netpod::Channel {
            backend: "testbackend".into(),
            name: "scalar-i32-be".into(),
        };
        // TODO read config from disk.
        let channel_config = ChannelConfig {
            channel: chn,
            keyspace: 2,
            time_bin_size: Nanos { ns: DAY },
            scalar_type: netpod::ScalarType::I32,
            byte_order: netpod::ByteOrder::big_endian(),
            shape: netpod::Shape::Scalar,
            array: false,
            compression: false,
        };
        let cluster = taskrun::test_cluster();
        let node = cluster.nodes[nodeix].clone();
        let buffer_size = 512;
        let event_chunker_conf = EventChunkerConf {
            disk_stats_every: ByteSize::kb(1024),
        };
    }
    */
}