use std::collections::{HashMap, VecDeque};

use crsn::asm::data::literal::Value;
use crsn::asm::instr::cond::Flag;
use crsn::module::{EvalRes, OpTrait};
use crsn::runtime::fault::Fault;
use crsn::runtime::run_thread::{state::RunState, ThreadInfo};
use crsn::sexp;
use crsn::sexp::{atom_qs, Sexp};
use crsn::utils::A;

use crate::defs::{BufIoMode, BufOps, BufValue};
use crsn::asm::data::Wr;

#[derive(Debug, Default, Clone)]
struct Buffer {
    data: VecDeque<Value>,
    iomode: BufIoMode,
}

#[derive(Debug, Default)]
struct ExtData {
    buffers: HashMap<Value, Buffer>,
}

// TODO optimize and DRY

impl OpTrait for BufOps {
    fn execute(&self, info: &ThreadInfo, state: &mut RunState) -> Result<EvalRes, Fault> {
        let eres = EvalRes::default();
        match self {
            BufOps::New { dst, value } => {
                let id = info.unique_handle();

                let que = match value {
                    BufValue::Zeros(len) => {
                        let len = state.read(len)? as usize;
                        let mut que = VecDeque::with_capacity(len);
                        que.resize(len, 0);
                        que
                    }
                    BufValue::Values(vals) => {
                        let mut que = VecDeque::with_capacity(vals.len());
                        for val in vals {
                            que.push_back(state.read(val)?);
                        }
                        que
                    }
                    BufValue::Chars(string) => {
                        let mut que = VecDeque::new();
                        for val in string.chars() {
                            que.push_back(val as Value);
                        }
                        que
                    }
                };

                let data: &mut ExtData = state.ext_mut();
                data.buffers.insert(id, Buffer {
                    data: que,
                    iomode: Default::default()
                });
                state.write(dst, id)?;
            }

            BufOps::SetIoMode { obj, mode } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;

                buf.iomode = *mode;
            }

            BufOps::Push { obj, src } => {
                state.clear_status();
                let val = state.read(src)?;
                let handle = state.read_obj(obj)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                buf.data.push_back(val);
            }

            BufOps::Pop { dst, obj } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                if let Some(val) = buf.data.pop_back() {
                    let empty = buf.data.is_empty();
                    state.write(dst, val)?;
                    state.update_status(val);
                    state.set_flag(Flag::Empty, empty);
                } else {
                    state.set_flag(Flag::Empty, true);
                    state.set_flag(Flag::Overflow, true);
                }
            }

            BufOps::Read { dst, obj, idx } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let idx = state.read(idx)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                if let Some(val) = buf.data.get(idx as usize) {
                    let val = *val;
                    state.update_status(val);
                    state.write(dst, val)?;
                } else {
                    state.set_flag(Flag::Overflow, true);
                }
            }

            BufOps::GetLen { dst, obj } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                let val = buf.data.len() as Value;
                state.write(dst, val)?;
                state.update_status(val);
            }

            BufOps::Write { obj, idx, value } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let val = state.read(value)?;
                let idx = state.read(idx)? as usize;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                if idx < buf.data.len() {
                    buf.data[idx] = val;
                } else if idx == buf.data.len() {
                    buf.data.push_back(val);
                } else {
                    state.set_flag(Flag::Overflow, true);
                }
            }

            BufOps::CompareSwap { obj, idx, expected, src } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let idx = state.read(idx)? as usize;
                let expected = state.read(expected)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                if idx < buf.data.len() {
                    if buf.data[idx] == expected {
                        // This looks stupid and it is stupid - the dance is needed to satisfy the borrow checker.
                        let val = state.read(src)?;
                        let store: &mut ExtData = state.ext_mut();
                        let buf = store.buffers.get_mut(&handle).unwrap();
                        buf.data[idx] = val;
                        state.set_flag(Flag::Equal, true);
                    }
                } else if idx == buf.data.len() && expected == 0 {
                    let val = state.read(src)?;
                    let store: &mut ExtData = state.ext_mut();
                    let buf = store.buffers.get_mut(&handle).unwrap();
                    buf.data.push_back(val);
                    state.set_flag(Flag::Equal, true);
                } else {
                    state.set_flag(Flag::Overflow, true);
                }
            }

            BufOps::Insert { obj, idx, value } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let val = state.read(value)?;
                let idx = state.read(idx)? as usize;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                if idx < buf.data.len() {
                    buf.data.insert(idx, val);
                } else if idx == buf.data.len() {
                    buf.data.push_back(val);
                } else {
                    state.set_flag(Flag::Overflow, true);
                }
            }

            BufOps::Remove { dst, obj, idx } => {
                state.clear_status();
                let handle = state.read_obj(obj)?;
                let idx = state.read(idx)? as usize;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                if idx < buf.data.len() {
                    let val = buf.data.remove(idx).unwrap();
                    let empty = buf.data.is_empty();
                    state.update_status(val);
                    state.write(dst, val)?;
                    state.set_flag(Flag::Empty, empty);
                } else {
                    state.set_flag(Flag::Overflow, true);
                }
            }

            BufOps::Resize { obj, len } => {
                let handle = state.read_obj(obj)?;
                let len = state.read(len)? as usize;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                buf.data.resize(len, 0);
            }

            BufOps::Reverse { obj } => {
                let handle = state.read_obj(obj)?;
                let store: &mut ExtData = state.ext_mut();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                let len = buf.data.len();
                if len > 1 {
                    let mut start = 0;
                    let mut end = len - 1;
                    while start < end {
                        buf.data.swap(start, end);
                        start += 1;
                        end -= 1;
                    }
                }
            }

            BufOps::AppendBuf { obj, obj2 } => {
                let handle = state.read_obj(obj)?;
                let handle2 = state.read_obj(obj2)?;
                let store: &mut ExtData = state.ext_mut();
                // TODO figure out how to avoid cloning
                let buf2 = store.buffers.get(&handle2).ok_or_else(|| Fault::ObjectNotExist(handle))?.data.clone();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                buf.data.extend(buf2);
            }

            BufOps::PrependBuf { obj, obj2 } => {
                let handle = state.read_obj(obj)?;
                let handle2 = state.read_obj(obj2)?;
                let store: &mut ExtData = state.ext_mut();
                // TODO figure out how to avoid cloning
                let buf2 = store.buffers.get(&handle2).ok_or_else(|| Fault::ObjectNotExist(handle))?.data.clone();
                let buf = store.buffers.get_mut(&handle).ok_or_else(|| Fault::ObjectNotExist(handle))?;
                for v in buf2.into_iter().rev() {
                    buf.data.push_front(v);
                }
            }
        }

        Ok(eres)
    }

    fn to_sexp(&self) -> Sexp {
        match self {
            BufOps::Push { obj, src } => sexp::list(&[A("push"), A(obj), A(src)]),
            BufOps::Pop { dst, obj } => sexp::list(&[A("pop"), A(dst), A(obj)]),

            BufOps::New { dst, value } => {
                match value {
                    BufValue::Zeros(n) => {
                        sexp::list(&[A("mkbf"), A(dst), A(n)])
                    }
                    BufValue::Values(vals) => {
                        let mut vals: Vec<_> = vals.iter().map(A).collect();
                        vals.insert(0, A(dst));
                        vals.insert(0, A("mkbfv"));
                        sexp::list(&vals)
                    }
                    BufValue::Chars(str) => {
                        sexp::list(&[A("mkbfv"), A(dst), atom_qs(str)])
                    }
                }
            }

            BufOps::Read { dst, obj, idx } => {
                sexp::list(&[A("bfrd"), A(dst), A(obj), A(idx)])
            }

            BufOps::GetLen { dst, obj } => {
                sexp::list(&[A("bfsz"), A(dst), A(obj)])
            }

            BufOps::Write { obj, idx, value } => {
                sexp::list(&[A("bfwr"), A(obj), A(idx), A(value)])
            }

            BufOps::CompareSwap { obj, idx, expected , src } => {
                sexp::list(&[A("bfcas"), A(obj), A(idx), A(expected), A(src)])
            }

            BufOps::Insert { obj, idx, value } => {
                sexp::list(&[A("bfins"), A(obj), A(idx), A(value)])
            }

            BufOps::Remove { dst, obj, idx } => {
                sexp::list(&[A("bfrm"), A(dst), A(obj), A(idx)])
            }

            BufOps::Resize { obj, len } => {
                sexp::list(&[A("bfrsz"), A(obj), A(len)])
            }

            BufOps::Reverse { obj } => {
                sexp::list(&[A("bfrev"), A(obj)])
            }

            BufOps::AppendBuf { obj, obj2 } => {
                sexp::list(&[A("bfapp"), A(obj), A(obj2)])
            }

            BufOps::PrependBuf { obj, obj2 } => {
                sexp::list(&[A("bfprep"), A(obj), A(obj2)])
            }
            BufOps::SetIoMode { obj, mode } => {
                sexp::list(&[A("bfio"), A(obj), A(mode.to_value())])
            }
        }
    }
}


pub(crate) fn drop_obj(state: &mut RunState, handle: Value) -> Result<Option<()>, Fault> {
    let store: &mut ExtData = state.ext_mut();
    Ok(store.buffers.remove(&handle).map(|_| ()))
}

/// Run-time method called to read an object (using the object handle syntax)
pub(crate) fn read_obj(state: &mut RunState, handle: Value)
            -> Result<Option<Value>, Fault>
{
    let store: &mut ExtData = state.ext_mut();
    if let Some(buf) = store.buffers.get_mut(&handle) {
        match match buf.iomode {
            BufIoMode::Queue => buf.data.pop_front(),
            BufIoMode::ReverseQueue => buf.data.pop_back(),
            BufIoMode::Stack => buf.data.pop_back(),
            BufIoMode::ReverseStack => buf.data.pop_front()
        } {
            None => {
                state.set_flag(Flag::Overflow, true);
                state.set_flag(Flag::Empty, true);
                Ok(Some(0))
            }
            Some(val) => {
                let em = buf.data.is_empty();
                state.set_flag(Flag::Empty, em);
                Ok(Some(val))
            }
        }
    } else {
        Ok(None)
    }
}

/// Run-time method called to read all from an object (using the object handle syntax)
pub(crate) fn read_obj_all(state: &mut RunState, whandle: Wr, rhandle: Value)
                       -> Result<Option<()>, Fault>
{
    let store: &mut ExtData = state.ext_mut();
    if let Some(buf) = store.buffers.get_mut(&rhandle) {
        for v in buf.data.clone() { // FIXME potentially needless clone (but allows "aliasing")
            state.write(whandle, v)?;
        }
        Ok(Some(()))
    } else {
        Ok(None)
    }
}

/// Run-time method called to write an object (using the object handle syntax)
pub(crate) fn write_obj(state: &mut RunState, handle: Value, value: Value) -> Result<Option<()>, Fault>
{
    let store: &mut ExtData = state.ext_mut();
    if let Some(buf) = store.buffers.get_mut(&handle) {
        match buf.iomode {
            BufIoMode::Queue => buf.data.push_back(value),
            BufIoMode::ReverseQueue => buf.data.push_front(value),
            BufIoMode::Stack => buf.data.push_back(value),
            BufIoMode::ReverseStack => buf.data.push_front(value)
        }

        Ok(Some(()))
    } else {
        Ok(None)
    }
}