use sexp::SourcePosition;

use crate::asm::data::{Rd, RdObj, Wr, RdWr};
use crate::asm::data::literal::{DebugMsg, Label, RoutineName};
use crate::asm::instr::Op;
use crate::asm::instr::op::OpKind;
use std::fmt::{Display, Formatter};
use std::fmt;
use crate::asm::error::CrsnError;
use crate::asm::patches::ErrWithPos;

#[derive(Debug)]
pub enum Barrier {
    /// Barrier that logically opens a section that cannot be jumped into, typically a routine
    Open(Label),
    /// Closing counterpart to the Open barrier
    Close(Label),
    /// Stand-alone barrier
    Standalone,
}

#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub enum SleepUnit {
    Usec, Msec, Sec
}

impl SleepUnit {
    pub fn micros(self) -> u64 {
        match self {
            SleepUnit::Usec => 1,
            SleepUnit::Msec => 1000,
            SleepUnit::Sec => 1000000,
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub enum LdsValue {
    Values(Vec<Rd>),
    Handle(RdObj),
    Chars(String),
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct BitSlice {
    pub width: u32,
    pub src_pos: u32,
    pub dst_pos: u32
}

impl Display for BitSlice {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        if self.is_full() {
            return Ok(());
        }

        write!(f, "{}", self.width)?;
        if self.src_pos != 0 || self.dst_pos != 0 {
            write!(f, "/{}", self.dst_pos)?;
        }
        if self.src_pos != 0 {
            write!(f, "/{}", self.src_pos)?;
        }
        Ok(())
    }
}

impl Default for BitSlice {
    fn default() -> Self {
        Self {
            width: 64,
            src_pos: 0,
            dst_pos: 0
        }
    }
}

impl BitSlice {
    pub fn full() -> Self {
        Self::default()
    }

    /// Parse LEN (no SRC and DST)
    pub fn parse1(src: &str, pos: &SourcePosition) -> Result<Option<Self>, CrsnError> {
        match Self::parse(src, pos) {
            Ok(Some(slice)) => {
                if slice.src_pos != 0 || slice.dst_pos != 0 {
                    return Err(CrsnError::Parse("Excess bit slice modifiers".into(), pos.clone()));
                }

                Ok(Some(BitSlice {
                    width: slice.width,
                    src_pos: 0,
                    dst_pos: 0
                }))
            }
            other => other
        }
    }

    /// Parse LEN/SRC
    pub fn parse2(src: &str, pos: &SourcePosition) -> Result<Option<Self>, CrsnError> {
        match Self::parse(src, pos) {
            Ok(Some(slice)) => {
                if slice.src_pos != 0 {
                    return Err(CrsnError::Parse("Excess bit slice modifiers".into(), pos.clone()));
                }

                Ok(Some(BitSlice {
                    width: slice.width,
                    src_pos: slice.dst_pos,
                    dst_pos: 0
                }))
            }
            other => other
        }
    }

    /// Parse a bit slice LEN/DST/SRC
    /// - String not starting with a digit is rejected as `Ok(None)`
    /// - Empty string is parsed as a full slice
    pub fn parse(src: &str, pos: &SourcePosition) -> Result<Option<Self>, CrsnError> {
        if src.is_empty() {
            return Ok(Some(BitSlice::full()));
        }

        if !src.starts_with(|c: char| c.is_ascii_digit()) {
            return Ok(None);
        }

        // We have a opXX, opXX/YY, or opXX/YY/ZZ
        let mut numbers : Vec<u32> = vec![];
        for p in src.split('/') {
            numbers.push(p.parse().err_pos(pos)?);
        }

        let slice = BitSlice {
            width: numbers[0],
            src_pos: numbers.get(2).copied().unwrap_or(0),
            dst_pos: numbers.get(1).copied().unwrap_or(0)
        };

        if slice.width == 0 || slice.width > 64 {
            return Err(CrsnError::Parse("Bit slice width must be 1-64".into(), pos.clone()));
        }

        // Validation
        if slice.src_pos + slice.width > 64 {
            return Err(CrsnError::Parse("Invalid source bit slice".into(), pos.clone()));
        }
        if slice.dst_pos + slice.width > 64 {
            return Err(CrsnError::Parse("Invalid destination bit slice".into(), pos.clone()));
        }

        Ok(Some(slice))
    }

    pub fn is_full(self) -> bool {
        self.width == 64
    }
}

#[derive(Debug)]
pub enum BuiltinOp {
    /// Do nothing (costs one cycle)
    Nop,
    /// Stop execution
    Halt,
    /// Sleep
    Sleep {
        count: Rd,
        unit_us: SleepUnit,
    },
    /// Mark a jump target.
    Label(Label),
    /// Jump to a label
    Jump(Label),
    /// Mark a far jump target (can be jumped to from another routine).
    /// This label is preserved in optimized code.
    FarLabel(Label),
    /// Jump to a label that can be in another function
    FarJump(Label),
    /// Call a routine with arguments.
    /// The arguments are passed as argX. Return values are stored in resX registers.
    Call(RoutineName, Vec<Rd>),
    /// Exit the current routine with return values
    Ret(Vec<Rd>),
    /// Mark a routine entry point (call target).
    /// The RoutineName struct includes its arity
    Routine(RoutineName),
    /// Skip backward or forward. The skip count can be defined by an argument.
    Skip(Rd),
    /// Deny jumps, skips and run across this address, producing a run-time fault.
    Barrier {
        kind: Barrier,
        msg: Option<DebugMsg>,
    },
    /// Generate a run-time fault with a debugger message
    Fault(Option<DebugMsg>),
    /// Deallocate an extension object.
    /// The object is released and the handle becomes invalid.
    Delete(RdObj),
    /// Move a value
    Load { dst: Wr, src: Rd },
    /// Move bits of a value
    LoadBits { dst: RdWr, src: Rd, slice: BitSlice },
    /// Move N values
    LoadMultiple { dst: Wr, src: Rd, count: Rd },
    /// Move values from a string or integer list
    LoadSequence { dst: Wr, value: LdsValue },
    /// Swap two registers
    Exchange { a: RdWr, b: RdWr, slice : BitSlice },
    /// Store runtime status to a register
    StoreFlags { dst: Wr },
    /// Load runtime status from a register
    LoadFlags { src: Rd },
}

impl BuiltinOp {
    pub fn into_op(self: BuiltinOp, pos: SourcePosition) -> Op {
        Op {
            kind: self.into(),
            pos,
            cond: None,
        }
    }
}

impl From<BuiltinOp> for OpKind {
    fn from(bo: BuiltinOp) -> Self {
        OpKind::BuiltIn(bo)
    }
}