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use SReg;

// TODO: s/addr/num

/// `SP` low register number.
pub const SP_LO_NUM: u8 = 32;
/// `SP` high register number.
pub const SP_HI_NUM: u8 = 33;

#[derive(Clone,Debug,PartialEq,Eq)]
pub struct Register
{
    pub name: String,
    pub value: u8,
}

/// The register file.
#[derive(Clone,Debug,PartialEq,Eq)]
pub struct RegisterFile
{
    registers: Vec<Register>,
    pub sreg: SReg,
}

impl RegisterFile
{
    pub fn new(registers: Vec<Register>) -> Self {
        RegisterFile {
            registers: registers,
            sreg: SReg::new(),
        }
    }

    pub fn registers(&self) -> ::std::slice::Iter<Register> {
        self.registers.iter()
    }

    /// Gets a register, or `None` if it doesn't exist.
    pub fn gpr(&self, addr: u8)
        -> Option<u8> {

        self.registers.get(addr as usize).map(|r| r.value)
    }

    /// Gets a mutable register, or `None` if it doesn't exist.
    pub fn gpr_mut(&mut self, addr: u8)
        -> Option<&mut u8> {

        self.registers.get_mut(addr as usize).map(|r| &mut r.value)
    }

    // TODO: remove, unnecessary
    pub fn gpr_val(&self, addr: u8)
        -> Option<u8> {
        self.gpr(addr)
    }

    pub fn gpr_pair(&self, addr: u8)
        -> Option<(u8,u8)> {
        assert!(addr % 2 == 0,
                "GPR pairs must be even");

        let lo = self.gpr(addr).unwrap();
        let hi = self.gpr(addr+1).unwrap();

        Some((lo, hi))
    }

    pub fn gpr_pair_val(&self, addr: u8)
        -> Option<u16> {
        let (lo,hi) = self.gpr_pair(addr).unwrap();
        let val = ((hi as u16) << 8) | lo as u16;
        Some(val)
    }

    pub fn set_gpr_pair(&mut self, low: u8, val: u16) {
        let val_lo = ((val & 0x00ff) >> 0) as u8;
        let val_hi = ((val & 0xff00) >> 8) as u8;

        *self.gpr_mut(low).unwrap() = val_lo;
        *self.gpr_mut(low+1).unwrap() = val_hi;
    }

    /// Checks if a flag is set in SREG.
    pub fn sreg_flag(&self, mask: u8) -> bool {
        (self.sreg.0.value & mask) == mask
    }

    pub fn sreg_flag_set(&mut self, mask: u8) {
        self.sreg.0.value |= mask;
    }

    pub fn sreg_flag_clear(&mut self, mask: u8) {
        self.sreg.0.value &= !mask;
    }
}