use std::borrow::Cow;
use std::convert::TryFrom;

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

use crate::asm::data::{DataDisp, Rd, RdData, reg, Wr, WrData};
use crate::asm::data::literal::{ConstantName, Label, RegisterAlias, Value};
use crate::asm::error::CrsnError;
use crate::asm::parse::ParserContext;
use crate::asm::parse::sexp_expect::expect_string_atom;
use std::num::TryFromIntError;
use crate::asm::patches::ErrWithPos;

fn is_valid_identifier(name: &str) -> bool {
    name.starts_with(|c: char| c.is_ascii_alphabetic() || c == '_')
        && name.chars().find(|c| !c.is_ascii_alphanumeric() && *c != '_').is_none()
}

/// Parse register alias
pub fn parse_reg_alias(name: Sexp) -> Result<(RegisterAlias, SourcePosition), CrsnError> {
    // trace!("parse reg alias: {:?}", name);

    let (name, namepos) = expect_string_atom(name)?;

    if !is_valid_identifier(&name) {
        return Err(CrsnError::Parse(format!("\"{}\" is not an allowed register alias.", name).into(), namepos));
    }

    Ok((name, namepos))
}

/// Parse constant name
pub fn parse_constant_name(name: Sexp) -> Result<(ConstantName, SourcePosition), CrsnError> {
    // trace!("parse const name: {:?}", name);

    let (name, namepos) = expect_string_atom(name)?;

    if !is_valid_identifier(&name) {
        return Err(CrsnError::Parse(format!("\"{}\" is not an allowed constant name.", name).into(), namepos));
    }

    Ok((name, namepos))
}

/// Parse a label
pub fn parse_label(name: Sexp) -> Result<Label, CrsnError> {
    // trace!("parse label: {:?}", name);
    let (name, namepos) = expect_string_atom(name)?;
    Ok(parse_label_str(&name, namepos)?)
}

pub fn parse_label_str(name: &str, pos: SourcePosition) -> Result<Label, CrsnError> {
    let label = name.trim_start_matches(':');

    Ok(if label.starts_with('#') {
        let val = parse_u64(&label[1..], pos.clone())?;
        Label::Numbered(u32::try_from(val).err_pos(pos)?)
    } else {
        Label::Named(label.to_string())
    })
}

/// Parse data disposition (address/value, without the read/write restriction)
pub fn parse_data_disp(tok: Sexp, pcx: &ParserContext) -> Result<DataDisp, CrsnError> {
    // trace!("parse data: {:?}", tok);

    // TODO implement masks

    match tok {
        Sexp::Atom(Atom::I(val), pos) => {
            Ok(DataDisp::Immediate(unsafe { std::mem::transmute(val) }))
        }
        Sexp::Atom(Atom::S(s), pos) => {
            if s == "_" {
                return Ok(DataDisp::Discard);
            }

            // check if we have an alias defined
            {
                let pstate = pcx.state.borrow();
                if let Some(val) = pstate.constants.get(&s) {
                    return Ok(DataDisp::Immediate(*val));
                }

                if let Some(val) = pstate.reg_aliases.get(&s) {
                    return Ok(DataDisp::Register(*val));
                }
            }

            if let Some(reference) = s.strip_prefix('@') {
                let pstate = pcx.state.borrow();
                if let Some(val) = pstate.reg_aliases.get(reference) {
                    Ok(DataDisp::ObjectPtr(*val))
                } else {
                    let reg = reg::parse_reg(reference, pos.clone())?;

                    if pstate.reg_aliases.values().find(|v| **v == reg).is_some() {
                        Err(CrsnError::Parse(format!("Sym exists for register {}, direct access denied. Unsym it if needed.", reg).into(), pos))
                    } else {
                        Ok(DataDisp::ObjectPtr(reg))
                    }
                }
            } else if s.starts_with(|c: char| c.is_ascii_digit()) {
                Ok(DataDisp::Immediate(unsafe { std::mem::transmute(parse_i64(&s, pos)?) }))
            } else {
                let reg = reg::parse_reg(&s, pos.clone())?;

                let pstate = pcx.state.borrow();
                if pstate.reg_aliases.values().find(|v| **v == reg).is_some() {
                    Err(CrsnError::Parse(format!("Sym exists for register {}, direct access denied. Unsym it if needed.", reg).into(), pos))
                } else {
                    Ok(DataDisp::Register(reg))
                }
            }
        }
        other => {
            Err(CrsnError::Parse(format!("bad data disp: {:?}", other).into(), other.pos().clone()))
        }
    }
}

/// Parse immediate value
pub fn parse_value(tok: Sexp, pcx: &ParserContext) -> Result<Value, CrsnError> {
    match tok {
        Sexp::Atom(Atom::I(val), pos) => {
            Ok(unsafe { std::mem::transmute(val) })
        }
        Sexp::Atom(Atom::S(s), pos) => {
            let pstate = pcx.state.borrow();
            if let Some(val) = pstate.constants.get(&s) {
                return Ok(*val);
            }

            Ok(unsafe { std::mem::transmute(parse_i64(&s, pos)?) })
        }
        other => {
            Err(CrsnError::Parse(format!("bad value format: {:?}", other).into(), other.pos().clone()))
        }
    }
}


pub fn parse_u64(literal: &str, pos: SourcePosition) -> Result<u64, CrsnError> {
    // trace!("parse u64 from {}", literal);
    let mut without_underscores = Cow::Borrowed(literal);
    if without_underscores.contains('_') {
        without_underscores = without_underscores.replace('_', "").into();
    }

    if let Some(hex) = without_underscores.strip_prefix("0x") {
        Ok(u64::from_str_radix(hex, 16).err_pos(pos)?)
    } else if let Some(hex) = without_underscores.strip_prefix("0b") {
        Ok(u64::from_str_radix(hex, 2).err_pos(pos)?)
    } else {
        Ok(u64::from_str_radix(&without_underscores, 10).err_pos(pos)?)
    }
}

pub fn parse_i64(literal: &str, pos: SourcePosition) -> Result<i64, CrsnError> {
    // trace!("parse i64 from {}", literal);
    if let Some(_value) = literal.strip_prefix("-") {
        Ok(-1 * i64::try_from(parse_u64(literal, pos.clone())?).err_pos(pos)?)
    } else {
        Ok(i64::try_from(parse_u64(literal, pos.clone())?).err_pos(pos)?)
    }
}

pub fn parse_rd(tok: Sexp, pcx: &ParserContext) -> Result<Rd, CrsnError> {
    let pos = tok.pos().clone();
    Ok(Rd::new(RdData::try_from(parse_data_disp(tok, pcx)?).err_pos(pos)?))
}

pub fn parse_wr(tok: Sexp, pcx: &ParserContext) -> Result<Wr, CrsnError> {
    let pos = tok.pos().clone();
    Ok(Wr::new(WrData::try_from(parse_data_disp(tok, pcx)?).err_pos(pos)?))
}