use sexp::{SourcePosition, Sexp, Atom};

use crate::asm::error::CrsnError;
use crate::asm::instr::op::OpKind;
use crate::asm::parse::arg_parser::TokenParser;
use crate::module::{CrsnExtension, ParseRes};
use crate::asm::data::literal::{Value, Label};
use crate::asm::instr::{Flatten, Op};
use crate::asm::parse::parse_instructions;
use crate::builtin::defs::BuiltinOp;
use crate::asm::instr::flatten::jumps_to_skips;
use crate::asm::data::{Rd, RdData};
use crate::asm::parse::parse_data::parse_label;

pub mod defs;
pub mod exec;
pub mod parse;

pub(crate) const RT_OPT_TIMESLICE : u64 = 1;

#[derive(Debug, Clone)]
pub struct BuiltinOps;

impl BuiltinOps {
    pub fn new() -> Box<dyn CrsnExtension> {
        Box::new(Self)
    }
}

impl CrsnExtension for BuiltinOps {
    fn name(&self) -> &'static str {
        "builtin"
    }

    fn parse_op<'a>(&self, pos: &SourcePosition, keyword: &str, args: TokenParser<'a>) -> Result<ParseRes<'a, OpKind>, CrsnError> {
        parse::parse_op(pos, keyword, args)
    }

    /// Get value of an extension-provided constant.
    /// This constant may be an object handle, or a constant value used as argument in some other instruction.
    fn get_constant_value<'a>(&self, name: &str) -> Option<Value> {
        match name {
            "RT_TIMESLICE" => Some(RT_OPT_TIMESLICE),
            _ => None,
        }
    }

    /// Parse a generic S-expression (non-op) that started with the given keyword
    ///
    /// pcx is available on the arg_tokens parser
    fn parse_syntax<'a>(&self, pos: &SourcePosition, keyword: &str, mut tokens: TokenParser<'a>)
                        -> Result<ParseRes<'a, Box<dyn Flatten>>, CrsnError>
    {
        if keyword == "crit" || keyword == "critical" {
            let pcx = tokens.pcx;
            let opts = parse_instructions(tokens.into_iter(), pos, pcx)?;

            let flattened = jumps_to_skips(opts.flatten(&pcx.state.borrow_mut().label_num)?)?;

            let len = flattened.len();

            for (n, op) in flattened.iter().enumerate() {
                match op.kind {
                    OpKind::BuiltIn(BuiltinOp::Skip(Rd(RdData::Immediate(skip)))) => {
                        let signed = i64::from_ne_bytes(skip.to_ne_bytes());
                        let target = n as i64 + signed;
                        if target < 0 || target > len as i64 {
                            return Err(CrsnError::Parse("Cannot jump out of a critical section!".into(), op.pos()));
                        }
                    }
                    /* Non-constant skip cannot be validated */
                    OpKind::BuiltIn(BuiltinOp::Skip(_)) => {
                        return Err(CrsnError::Parse("Variable skips are not allowed in a critical section".into(), op.pos()));
                    }
                    /* Yield in critical makes zero sense */
                    OpKind::BuiltIn(BuiltinOp::Yield { .. }) => {
                        return Err(CrsnError::Parse("Yield in a critical section!".into(), op.pos()));
                    }
                    /* This is likely a bug */
                    OpKind::BuiltIn(BuiltinOp::Ret(_)) => {
                        return Err(CrsnError::Parse("Ret in a critical section!".into(), op.pos()));
                    }
                    /* Probably also a bug. If someone really wants this, they can start and end the critical section manually. */
                    OpKind::BuiltIn(BuiltinOp::FarJump(_)) => {
                        return Err(CrsnError::Parse("Far jump a critical section!".into(), op.pos()));
                    }
                    _ => {}
                }
            }

            let vec : Vec<Box<dyn Flatten>> = vec![
                Box::new(Op {
                    kind: OpKind::BuiltIn(BuiltinOp::CriticalBegin),
                    cond: None,
                    pos: pos.clone(),
                }),
                Box::new(flattened),
                Box::new(Op {
                    kind: OpKind::BuiltIn(BuiltinOp::CriticalEnd),
                    cond: None,
                    pos: pos.clone(),
                }),
            ];

            return Ok(ParseRes::Parsed(Box::new(vec)));
        }

        if keyword == "loop" {
            let mut end_label = None;
            let label = if let Some(Sexp::Atom(Atom::S(_), _)) = tokens.peek() {
                let label = parse_label(tokens.next().unwrap())?;
                if let Label::Named(n) = &label {
                    end_label = Some(Label::Named(format!("{}-end", n)));
                }
                label
            } else {
                Label::unique(&tokens.pcx.state.borrow().label_num)
            };

            let pcx = tokens.pcx;
            let inner = parse_instructions(tokens.into_iter(), pos, pcx)?;

            let mut vec : Vec<Box<dyn Flatten>> = vec![
                Box::new(Op {
                    kind: OpKind::BuiltIn(BuiltinOp::Label(label.clone())),
                    cond: None,
                    pos: pos.clone(),
                }),
                inner,
                Box::new(Op {
                    kind: OpKind::BuiltIn(BuiltinOp::Jump(label)),
                    cond: None,
                    pos: pos.clone(),
                }),
            ];

            if let Some(el) = end_label {
                vec.push(Box::new(Op {
                    kind: OpKind::BuiltIn(BuiltinOp::Label(el)),
                    cond: None,
                    pos: pos.clone(),
                }));
            }

            return Ok(ParseRes::Parsed(Box::new(vec)))
        }

        Ok(ParseRes::Unknown(tokens))
    }
}