use std::fmt::{self, Display, Formatter};
use std::ops::Not;

use sexp::SourcePosition;

use crate::asm::error::CrsnError;

/// Condition flag
#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
pub enum Cond {
    /// Equality
    Equal,
    /// Inequality
    NotEqual,
    /// Equal to zero
    Zero,
    /// Not equal zero
    NotZero,
    /// A < B
    Lower,
    /// A <= B
    LowerOrEqual,
    /// A > B
    Greater,
    /// A >= B
    GreaterOrEqual,
    /// A > 0
    Positive,
    /// A <= 0
    NonPositive,
    /// A < 0
    Negative,
    /// A >= 0
    NonNegative,
    /// Arithmetic operation caused an integer operand to overflow
    Overflow,
    /// No overflow
    NotOverflow,
    /// Arithmetic (or other) operation was invalid.
    /// Example: division by zero
    Invalid,
    /// Operation was valid
    Valid,
    /// Arithmetic carry
    Carry,
    /// Carry not set
    NotCarry,
    // Full
    Full,
    /// Not full
    NotFull,
    // Empty
    Empty,
    /// Not empty
    NotEmpty,
}

pub fn parse_cond(text: &str, pos: &SourcePosition) -> Result<Cond, CrsnError> {
    Ok(match text.trim_end_matches('?') {
        "eq" | "=" | "==" => Cond::Equal,
        "ne" | "<>" | "!=" | "≠" => Cond::NotEqual,
        "z" | "0" => Cond::Zero,
        "nz" | "<>0" | "!0" => Cond::NotZero,
        "lt" | "<" => Cond::Lower,
        "le" | "<=" | "≤" => Cond::LowerOrEqual,
        "gt" | ">" => Cond::Greater,
        "ge" | ">=" | "≥" => Cond::GreaterOrEqual,
        "pos" | "+" | ">0" => Cond::Positive,
        "neg" | "-" | "<0" => Cond::Negative,
        "npos" | "0-" | "<=0" | "≥0" => Cond::NonPositive,
        "nneg" | "0+" | ">=0" | "≤0" => Cond::NonNegative,
        "c" => Cond::Carry,
        "nc" => Cond::NotCarry,
        "em" => Cond::Empty,
        "nem" => Cond::NotEmpty,
        "f" => Cond::Full,
        "nf" => Cond::NotFull,
        "valid" => Cond::Valid,
        "inval" => Cond::Invalid,
        "ov" => Cond::Overflow,
        "nov" => Cond::NotOverflow,
        _ => {
            return Err(CrsnError::Parse(format!("Unknown cond: {}", text).into(), pos.clone()));
        }
    })
}

impl Display for Cond {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_str(match self {
            Cond::Equal => "eq",
            Cond::NotEqual => "ne",
            Cond::Zero => "z",
            Cond::NotZero => "nz",
            Cond::Empty => "emp",
            Cond::NotEmpty => "nemp",
            Cond::Full => "full",
            Cond::NotFull => "nfull",
            Cond::Lower => "lt",
            Cond::LowerOrEqual => "le",
            Cond::Greater => "gt",
            Cond::GreaterOrEqual => "ge",
            Cond::Positive => "pos",
            Cond::Negative => "neg",
            Cond::NonPositive => "npos",
            Cond::NonNegative => "nneg",
            Cond::Overflow => "ov",
            Cond::NotOverflow => "nov",
            Cond::Carry => "c",
            Cond::NotCarry => "nc",
            Cond::Invalid => "inval",
            Cond::Valid => "valid",
        })
    }
}

impl Not for Cond {
    type Output = Cond;

    fn not(self) -> Self::Output {
        match self {
            Cond::Equal => Cond::NotEqual,
            Cond::Zero => Cond::NotZero,
            Cond::Overflow => Cond::NotOverflow,
            Cond::Carry => Cond::NotCarry,

            Cond::Empty => Cond::NotEmpty,
            Cond::NotEmpty => Cond::Empty,

            Cond::Full => Cond::NotFull,
            Cond::NotFull => Cond::Full,

            Cond::Positive => Cond::NonPositive,
            Cond::Negative => Cond::NonNegative,
            Cond::NonPositive => Cond::Positive,
            Cond::NonNegative => Cond::Negative,

            Cond::NotEqual => Cond::Equal,
            Cond::NotZero => Cond::Zero,
            Cond::NotOverflow => Cond::Overflow,
            Cond::NotCarry => Cond::Carry,

            Cond::Lower => Cond::GreaterOrEqual,
            Cond::Greater => Cond::LowerOrEqual,
            Cond::LowerOrEqual => Cond::Greater,
            Cond::GreaterOrEqual => Cond::Lower,

            Cond::Invalid => Cond::Valid,
            Cond::Valid => Cond::Invalid,
        }
    }
}