// icodes
pub struct Icode {}

impl Icode {
    // Official names
    pub const BRK: u8 = 0x00u8;
    pub const LIT: u8 = 0b10000000; // AKA keep Yes really. Per spec;
    pub const LIT2: u8 = 0b10100000; // AKA keep Yes really. Per spec;
    pub const INC: u8 = 0x01;
    pub const POP: u8 = 0x02;
    pub const NIP: u8 = 0x03;
    pub const SWP: u8 = 0x04;
    pub const ROT: u8 = 0x05;
    pub const DUP: u8 = 0x06;
    pub const OVR: u8 = 0x07;
    pub const EQL: u8 = 0x08;
    pub const NEQ: u8 = 0x09;
    pub const GTH: u8 = 0x0a;
    pub const LTH: u8 = 0x0b;
    pub const JMP: u8 = 0x0c;
    pub const JCN: u8 = 0x0d;
    pub const JSR: u8 = 0x0e;
    pub const STH: u8 = 0x0f;
    pub const LDZ: u8 = 0x10;
    pub const STZ: u8 = 0x11;
    pub const LDR: u8 = 0x12;
    pub const STR: u8 = 0x13;
    pub const LDA: u8 = 0x14;
    pub const STA: u8 = 0x15;
    pub const DEI: u8 = 0x16;
    pub const DEO: u8 = 0x17;
    pub const ADD: u8 = 0x18;
    pub const SUB: u8 = 0x19;
    pub const MUL: u8 = 0x1a;
    pub const DIV: u8 = 0x1b;
    pub const AND: u8 = 0x1c;
    pub const ORA: u8 = 0x1d;
    pub const EOR: u8 = 0x1e;
    pub const SFT: u8 = 0x1f;

    // Opcode flags
    pub const SHORT: u8 = 0x20;
    pub const RETURN: u8 = 0x40;
    pub const KEEP: u8 = 0x80;

    // Hacking around the official names for some things
    pub const XOR: u8 = Icode::EOR;
    pub const EQ: u8 = Icode::EQL;
    pub const NE: u8 = Icode::NEQ;
    pub const GT: u8 = Icode::GTH;
    pub const LT: u8 = Icode::LTH;
    pub const OR: u8 = Icode::ORA;
    pub const NOP: u8 = Icode::POP | Icode::KEEP;

    pub const fn parse(opcode: u8) -> (u8, u8, u8, u8) {
        let kflag: u8 = (opcode >> 7) & 0x1;
        let rflag: u8 = (opcode >> 6) & 0x1;
        let sflag: u8 = (opcode >> 5) & 0x1;
        let icode: u8 = opcode & 0x1F;
        (kflag, rflag, sflag, icode)
    }

    pub const fn nameof(opcode: u8) -> &'static str {
        match opcode {
            // Nonstandard icodes + extensions
            Icode::LIT | Icode::LIT2 => &"LIT", // AKA keep Yes really. Per spec,
            Icode::NOP => &"NOP",
            // Standard icodes
            Icode::BRK => &"BRK",
            Icode::INC => &"INC",
            Icode::POP => &"POP",
            Icode::NIP => &"NIP",
            Icode::SWP => &"SWP",
            Icode::ROT => &"ROT",
            Icode::DUP => &"DUP",
            Icode::OVR => &"OVR",
            Icode::EQL => &"EQL",
            Icode::NEQ => &"NEQ",
            Icode::GTH => &"GTH",
            Icode::LTH => &"LTH",
            Icode::JMP => &"JMP",
            Icode::JCN => &"JNC",
            Icode::JSR => &"JSR",
            Icode::STH => &"STH",
            Icode::LDZ => &"LDZ",
            Icode::STZ => &"STZ",
            Icode::LDR => &"LDR",
            Icode::STR => &"STR",
            Icode::LDA => &"LDA",
            Icode::STA => &"STA",
            Icode::DEI => &"DEI",
            Icode::DEO => &"DEO",
            Icode::ADD => &"ADD",
            Icode::SUB => &"SUB",
            Icode::MUL => &"MUL",
            Icode::DIV => &"DIV",
            Icode::AND => &"AND",
            Icode::ORA => &"ORA",
            Icode::EOR => &"EOR",
            Icode::SFT => &"SFT",
            _ => Icode::nameof(opcode & 0x1F),
        }
    }
}