package cpu

func ldaExec(c *CPU, op operand) { c.A = c.operandValue(op); c.setZN(c.A) }
func ldxExec(c *CPU, op operand) { c.X = c.operandValue(op); c.setZN(c.X) }
func ldyExec(c *CPU, op operand) { c.Y = c.operandValue(op); c.setZN(c.Y) }

func staExec(c *CPU, op operand) { c.write(op.addr, c.A) }
func stxExec(c *CPU, op operand) { c.write(op.addr, c.X) }
func styExec(c *CPU, op operand) { c.write(op.addr, c.Y) }

func taxExec(c *CPU, op operand) { c.X = c.A; c.setZN(c.X) }
func txaExec(c *CPU, op operand) { c.A = c.X; c.setZN(c.A) }
func tayExec(c *CPU, op operand) { c.Y = c.A; c.setZN(c.Y) }
func tyaExec(c *CPU, op operand) { c.A = c.Y; c.setZN(c.A) }
func tsxExec(c *CPU, op operand) { c.X = c.SP; c.setZN(c.X) }
func txsExec(c *CPU, op operand) { c.SP = c.X } // no flags affected

func phaExec(c *CPU, op operand) { c.push(c.A) }
func plaExec(c *CPU, op operand) { c.A = c.pop(); c.setZN(c.A) }
func phpExec(c *CPU, op operand) { c.push(c.Status | FlagB | FlagU) }
func plpExec(c *CPU, op operand) {
	pulled := c.pop()
	c.Status = (pulled &^ FlagB) | FlagU
}

func (c *CPU) addWithCarry(v uint8) {
	var carryIn uint16
	if c.flag(FlagC) {
		carryIn = 1
	}
	sum := uint16(c.A) + uint16(v) + carryIn
	result := uint8(sum)

	c.setFlag(FlagC, sum > 0xFF)
	c.setFlag(FlagV, (c.A^v)&0x80 == 0 && (c.A^result)&0x80 != 0)
	c.A = result
	c.setZN(c.A)
}

func adcExec(c *CPU, op operand) { c.addWithCarry(c.operandValue(op)) }
func sbcExec(c *CPU, op operand) { c.addWithCarry(^c.operandValue(op)) }

func andExec(c *CPU, op operand) { c.A &= c.operandValue(op); c.setZN(c.A) }
func oraExec(c *CPU, op operand) { c.A |= c.operandValue(op); c.setZN(c.A) }
func eorExec(c *CPU, op operand) { c.A ^= c.operandValue(op); c.setZN(c.A) }

func bitExec(c *CPU, op operand) {
	v := c.operandValue(op)
	c.setFlag(FlagZ, c.A&v == 0)
	c.setFlag(FlagV, v&0x40 != 0)
	c.setFlag(FlagN, v&0x80 != 0)
}

func aslExec(c *CPU, op operand) {
	v := c.operandValue(op)
	c.setFlag(FlagC, v&0x80 != 0)
	result := v << 1
	c.writeOperand(op, result)
	c.setZN(result)
}

func lsrExec(c *CPU, op operand) {
	v := c.operandValue(op)
	c.setFlag(FlagC, v&0x01 != 0)
	result := v >> 1
	c.writeOperand(op, result)
	c.setZN(result)
}

func rolExec(c *CPU, op operand) {
	v := c.operandValue(op)
	var carryIn uint8
	if c.flag(FlagC) {
		carryIn = 1
	}
	c.setFlag(FlagC, v&0x80 != 0)
	result := v<<1 | carryIn
	c.writeOperand(op, result)
	c.setZN(result)
}

func rorExec(c *CPU, op operand) {
	v := c.operandValue(op)
	var carryIn uint8
	if c.flag(FlagC) {
		carryIn = 0x80
	}
	c.setFlag(FlagC, v&0x01 != 0)
	result := v>>1 | carryIn
	c.writeOperand(op, result)
	c.setZN(result)
}

func incExec(c *CPU, op operand) { v := c.operandValue(op) + 1; c.writeOperand(op, v); c.setZN(v) }
func decExec(c *CPU, op operand) { v := c.operandValue(op) - 1; c.writeOperand(op, v); c.setZN(v) }

func inxExec(c *CPU, op operand) { c.X++; c.setZN(c.X) }
func dexExec(c *CPU, op operand) { c.X--; c.setZN(c.X) }
func inyExec(c *CPU, op operand) { c.Y++; c.setZN(c.Y) }
func deyExec(c *CPU, op operand) { c.Y--; c.setZN(c.Y) }

func (c *CPU) compare(reg, v uint8) {
	result := reg - v
	c.setFlag(FlagC, reg >= v)
	c.setZN(result)
}

func cmpExec(c *CPU, op operand) { c.compare(c.A, c.operandValue(op)) }
func cpxExec(c *CPU, op operand) { c.compare(c.X, c.operandValue(op)) }
func cpyExec(c *CPU, op operand) { c.compare(c.Y, c.operandValue(op)) }

func (c *CPU) branch(op operand, cond bool) {
	if !cond {
		return
	}
	c.extraCycles++
	if !samePage(c.PC, op.addr) {
		c.extraCycles++
	}
	c.PC = op.addr
}

func bccExec(c *CPU, op operand) { c.branch(op, !c.flag(FlagC)) }
func bcsExec(c *CPU, op operand) { c.branch(op, c.flag(FlagC)) }
func bneExec(c *CPU, op operand) { c.branch(op, !c.flag(FlagZ)) }
func beqExec(c *CPU, op operand) { c.branch(op, c.flag(FlagZ)) }
func bplExec(c *CPU, op operand) { c.branch(op, !c.flag(FlagN)) }
func bmiExec(c *CPU, op operand) { c.branch(op, c.flag(FlagN)) }
func bvcExec(c *CPU, op operand) { c.branch(op, !c.flag(FlagV)) }
func bvsExec(c *CPU, op operand) { c.branch(op, c.flag(FlagV)) }

func jmpExec(c *CPU, op operand) { c.PC = op.addr }

func jsrExec(c *CPU, op operand) {
	c.push16(c.PC - 1) // address of the last byte of the jsr instruction
	c.PC = op.addr
}

func rtsExec(c *CPU, op operand) { c.PC = c.pop16() + 1 }

func rtiExec(c *CPU, op operand) {
	pulled := c.pop()
	c.Status = (pulled &^ FlagB) | FlagU
	c.PC = c.pop16()
}

func clcExec(c *CPU, op operand) { c.setFlag(FlagC, false) }
func secExec(c *CPU, op operand) { c.setFlag(FlagC, true) }
func cliExec(c *CPU, op operand) { c.setFlag(FlagI, false) }
func seiExec(c *CPU, op operand) { c.setFlag(FlagI, true) }
func cldExec(c *CPU, op operand) { c.setFlag(FlagD, false) }
func sedExec(c *CPU, op operand) { c.setFlag(FlagD, true) }
func clvExec(c *CPU, op operand) { c.setFlag(FlagV, false) }

func nopExec(c *CPU, op operand) {}

func brkExec(c *CPU, op operand) {
	c.PC++ // brk is logically 2 bytes: the byte after the opcode is skipped
	c.interrupt(vectorIRQ, true)
}

func laxExec(c *CPU, op operand) {
	v := c.operandValue(op)
	c.A, c.X = v, v
	c.setZN(v)
}

func saxExec(c *CPU, op operand) { c.write(op.addr, c.A&c.X) }

func dcpExec(c *CPU, op operand) {
	v := c.operandValue(op) - 1
	c.writeOperand(op, v)
	c.compare(c.A, v)
}

func sloExec(c *CPU, op operand) {
	v := c.operandValue(op)
	c.setFlag(FlagC, v&0x80 != 0)
	result := v << 1
	c.writeOperand(op, result)
	c.A |= result
	c.setZN(c.A)
}

func rlaExec(c *CPU, op operand) {
	v := c.operandValue(op)
	var carryIn uint8
	if c.flag(FlagC) {
		carryIn = 1
	}
	c.setFlag(FlagC, v&0x80 != 0)
	result := v<<1 | carryIn
	c.writeOperand(op, result)
	c.A &= result
	c.setZN(c.A)
}

func sreExec(c *CPU, op operand) {
	v := c.operandValue(op)
	c.setFlag(FlagC, v&0x01 != 0)
	result := v >> 1
	c.writeOperand(op, result)
	c.A ^= result
	c.setZN(c.A)
}

func rraExec(c *CPU, op operand) {
	v := c.operandValue(op)
	var carryIn uint8
	if c.flag(FlagC) {
		carryIn = 0x80
	}
	c.setFlag(FlagC, v&0x01 != 0)
	result := v>>1 | carryIn
	c.writeOperand(op, result)
	c.addWithCarry(result)
}

func iscExec(c *CPU, op operand) {
	v := c.operandValue(op) + 1
	c.writeOperand(op, v)
	c.addWithCarry(^v)
}

func jamExec(c *CPU, op operand) {
	c.Jammed = true
	c.PC--
}