use bitbuffer::{BitRead, BitReadSized, LittleEndian};
use serde::{Deserialize, Serialize};
use serde_repr::{Deserialize_repr, Serialize_repr};

use crate::demo::message::stringtable::log_base2;
use crate::demo::packet::datatable::{ClassId, SendTable};
use crate::demo::parser::ParseBitSkip;
use crate::demo::sendprop::{SendProp, SendPropIdentifier, SendPropValue};
use crate::{Parse, ParseError, ParserState, ReadResult, Result, Stream};
use parse_display::{Display, FromStr};
use std::cmp::min;

use std::fmt;
use std::hint::unreachable_unchecked;
use std::num::NonZeroU32;

#[derive(
    Debug,
    Copy,
    Clone,
    PartialEq,
    Eq,
    Hash,
    Serialize,
    Deserialize,
    Display,
    Ord,
    PartialOrd,
    FromStr,
    Default,
)]
pub struct EntityId(u32);

impl From<u32> for EntityId {
    fn from(num: u32) -> Self {
        EntityId(num)
    }
}

#[derive(BitRead, Clone, Copy, Debug, PartialEq, Eq, Serialize_repr, Deserialize_repr)]
#[discriminant_bits = 2]
#[repr(u8)]
pub enum PVS {
    Preserve = 0,
    Leave = 1,
    Enter = 2,
    Delete = 3,
}

#[derive(Debug, Clone)]
pub struct PacketEntity {
    pub server_class: ClassId,
    pub entity_index: EntityId,
    pub props: Vec<SendProp>,
    pub in_pvs: bool,
    pub pvs: PVS,
    pub serial_number: u32,
    pub delay: Option<u32>,
}

impl fmt::Display for PacketEntity {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(f, "{}({}) {{", self.entity_index, self.server_class)?;
        for child in self.props.iter() {
            writeln!(f, "\t{}", child)?;
        }
        write!(f, "}}")
    }
}

impl PacketEntity {
    pub fn get_prop_by_identifier(&mut self, index: &SendPropIdentifier) -> Option<&mut SendProp> {
        self.props.iter_mut().find(|prop| prop.index == *index)
    }

    pub fn apply_update(&mut self, props: Vec<SendProp>) {
        for prop in props {
            match self.get_prop_by_identifier(&prop.index) {
                Some(existing_prop) => existing_prop.value = prop.value,
                None => self.props.push(prop),
            }
        }
    }

    pub fn get_prop_by_name(&self, table_name: &str, name: &str) -> Option<&SendProp> {
        let identifier = SendPropIdentifier::new(table_name, name);
        self.props.iter().find(|prop| prop.index == identifier)
    }
}

fn read_bit_var<'a, T: BitReadSized<'a, LittleEndian>>(stream: &mut Stream<'a>) -> ReadResult<T> {
    let ty: u8 = stream.read_sized(2)?;

    let bits = match ty {
        0 => 4,
        1 => 8,
        2 => 12,
        3 => 32,
        _ => unsafe { unreachable_unchecked() },
    };
    stream.read_sized(bits)
}

#[derive(Debug)]
pub struct PacketEntitiesMessage {
    pub entities: Vec<PacketEntity>,
    pub removed_entities: Vec<EntityId>,
    pub max_entries: u16,
    pub delta: Option<NonZeroU32>,
    pub base_line: u8,
    pub updated_base_line: bool,
}

fn get_send_table<'a, 'b>(state: &'b ParserState, class: ClassId) -> Result<&'b SendTable> {
    state
        .send_tables
        .get(usize::from(class))
        .ok_or_else(|| ParseError::UnknownServerClass(class))
}

fn get_entity_for_update(
    state: &ParserState,
    entity_index: EntityId,
    pvs: PVS,
) -> Result<PacketEntity> {
    let class_id = *state
        .entity_classes
        .get(&entity_index)
        .ok_or_else(|| ParseError::UnknownEntity(entity_index))?;

    Ok(PacketEntity {
        server_class: class_id,
        entity_index,
        props: Vec::with_capacity(8),
        in_pvs: false,
        pvs,
        serial_number: 0,
        delay: None,
    })
}

impl Parse<'_> for PacketEntitiesMessage {
    fn parse(stream: &mut Stream, state: &ParserState) -> Result<Self> {
        let max_entries = stream.read_sized(11)?;
        let delta: Option<u32> = stream.read()?;
        let base_line = stream.read_sized(1)?;
        let updated_entries: u16 = stream.read_sized(11)?;
        let length: u32 = stream.read_sized(20)?;
        let updated_base_line = stream.read()?;
        let mut data = stream.read_bits(length as usize)?;

        let mut entities = Vec::with_capacity(min(updated_entries, 128) as usize);
        let mut removed_entities = Vec::new();

        let mut last_index: i32 = -1;

        for _ in 0..updated_entries {
            let diff: u32 = read_bit_var(&mut data)?;
            last_index = last_index.saturating_add(diff as i32).saturating_add(1);
            let entity_index = EntityId::from(last_index as u32);

            let pvs = data.read()?;
            if pvs == PVS::Enter {
                let mut entity =
                    Self::read_enter(&mut data, entity_index, state, base_line as usize)?;
                let send_table = get_send_table(state, entity.server_class)?;
                Self::read_update(&mut data, send_table, &mut entity.props)?;

                entities.push(entity);
            } else if pvs == PVS::Preserve {
                let mut entity = get_entity_for_update(state, entity_index, pvs)?;
                let send_table = get_send_table(state, entity.server_class)?;

                Self::read_update(&mut data, send_table, &mut entity.props)?;

                entities.push(entity);
            } else if state.entity_classes.contains_key(&entity_index) {
                let entity = get_entity_for_update(state, entity_index, pvs)?;
                entities.push(entity);
            }
        }

        if delta.is_some() {
            while data.read()? {
                removed_entities.push(data.read_sized::<u32>(11)?.into())
            }
        }

        Ok(PacketEntitiesMessage {
            entities,
            removed_entities,
            max_entries,
            delta: delta.and_then(NonZeroU32::new),
            base_line,
            updated_base_line,
        })
    }
}

impl PacketEntitiesMessage {
    fn read_enter(
        stream: &mut Stream,
        entity_index: EntityId,
        state: &ParserState,
        baseline_index: usize,
    ) -> Result<PacketEntity> {
        let bits = log_base2(state.server_classes.len()) + 1;
        let class_index: ClassId = stream.read_sized::<u16>(bits as usize)?.into();

        let serial = stream.read_sized(10)?;
        let send_table = state
            .send_tables
            .get(usize::from(class_index))
            .ok_or_else(|| ParseError::UnknownServerClass(class_index))?;

        let props = match state.instance_baselines[baseline_index].get(&entity_index) {
            Some(baseline) => baseline.clone(),
            None => match state.static_baselines.get(&class_index) {
                Some(_static_baseline) => state.get_static_baseline(class_index, send_table)?,
                None => Vec::with_capacity(8),
            },
        };

        Ok(PacketEntity {
            server_class: class_index,
            entity_index,
            props,
            in_pvs: true,
            pvs: PVS::Enter,
            serial_number: serial,
            delay: None,
        })
    }

    pub fn read_update(
        stream: &mut Stream,
        send_table: &SendTable,
        props: &mut Vec<SendProp>,
    ) -> Result<()> {
        let mut index: i32 = -1;

        while stream.read()? {
            let diff: u32 = read_bit_var(stream)?;
            index = index.saturating_add(diff as i32).saturating_add(1);

            match send_table.flattened_props.get(index as usize) {
                Some(definition) => {
                    let value = SendPropValue::parse(stream, &definition.parse_definition)?;
                    props.push(SendProp {
                        index: definition.identifier,
                        value,
                    });
                }
                None => {
                    return Err(ParseError::PropIndexOutOfBounds {
                        index,
                        prop_count: send_table.flattened_props.len(),
                    });
                }
            }
        }

        Ok(())
    }
}

impl ParseBitSkip<'_> for PacketEntitiesMessage {
    fn parse_skip(stream: &mut Stream) -> Result<()> {
        stream.skip_bits(11)?;
        if stream.read()? {
            stream.skip_bits(32)?;
        }
        stream.skip_bits(12)?;
        let length: u32 = stream.read_sized(20)?;
        stream
            .skip_bits(length as usize + 1)
            .map_err(ParseError::from)
    }
}