package chip8

import (
	"fmt"
	"testing"
)

func slicesEqual(x, y []byte) bool {
	if len(x) != len(y) {
		return false
	}
	for i, xi := range x {
		if xi != y[i] {
			return false
		}
	}
	return true
}

// This test is kinda shit, there's so much stuff we ain't testing
// Maybe fix
func TestCreateCPU(t *testing.T) {
	prog := []byte{1, 2, 3, 4}
	newCPU := NewCHIP8(prog)
	if !slicesEqual(newCPU.memory[200:204], prog) {
		t.Errorf("CPU not initalized properly")
	}
}

func TestClearDisplay(t *testing.T) {
	cpu := Chip8{opcode: 0x00E0}
	for i := range cpu.graphics {
		cpu.graphics[i] = byte(i % 255)
	}
	cpu.zeroIndexOpcodes()
	graphicsArray := cpu.GetGraphicsBuffer()
	graphicsSlice := graphicsArray[:]
	emptySlice := make([]byte, len(cpu.graphics))
	if !slicesEqual(graphicsSlice, emptySlice) {
		t.Errorf("Graphics buffer not cleared properly")
	}
}

func TestLeaveFunction(t *testing.T) {
	cpu := Chip8{pc: 50, opcode: 0x00EE}
	cpu.stack = append(cpu.stack, 1, 2, 3, 4, 5)
	cpu.zeroIndexOpcodes()
	if cpu.pc != 4 && len(cpu.stack) != 4 {
		t.Errorf("TestLeaveFunction not in expected state")
	}
}

func TestGoTo(t *testing.T) {
	cpu := Chip8{opcode: 0x3420}
	cpu.goTo()
	if cpu.pc != 0x420 {
		t.Errorf("Test GoTo not working as expected")
	}
}

func TestCallSubroutine(t *testing.T) {
	cpu := Chip8{opcode: 0x3420, pc: 43}
	cpu.callSubroutine()
	if (cpu.pc != 420) && (cpu.stack[0] != 43) && (len(cpu.stack) != 1) {
		t.Errorf("CallSubroutine not working as expected")
	}
}

func TestSkipIfRegisterEqual(t *testing.T) {
	var tests = []struct {
		register, regValue byte
		compValue, want    uint16
	}{
		{0, 2, 4, 0},
		{0, 2, 2, 2},
		{15, 2, 2, 2},
		{15, 1, 12, 0},
	}

	for _, tt := range tests {
		testname := fmt.Sprintf("Reg:%d,RegVal:%d,Comp:%d", tt.register, tt.regValue, tt.compValue)
		t.Run(testname, func(t *testing.T) {
			cpu := Chip8{opcode: tt.compValue + uint16(tt.register)<<8}
			cpu.registers[tt.register] = tt.regValue
			cpu.skipIfRegisterEqual()
			if tt.want != cpu.pc {
				t.Errorf("PC is %d, Wanted %d", cpu.pc, tt.want)
			}
		})
	}
}

func TestSkipIfRegisterNotEqual(t *testing.T) {
	var tests = []struct {
		register, regValue byte
		compValue, want    uint16
	}{
		{0, 2, 4, 2},
		{0, 2, 2, 0},
		{15, 2, 2, 0},
		{15, 1, 12, 2},
	}

	for _, tt := range tests {
		testname := fmt.Sprintf("Reg:%d,RegVal:%d,Comp:%d", tt.register, tt.regValue, tt.compValue)
		t.Run(testname, func(t *testing.T) {
			cpu := Chip8{opcode: tt.compValue + uint16(tt.register)<<8}
			cpu.registers[tt.register] = tt.regValue
			cpu.skipIfRegisterNotEqual()
			if tt.want != cpu.pc {
				t.Errorf("PC is %d, Wanted %d", cpu.pc, tt.want)
			}
		})
	}
}

func TestSkipIfRegistersEqual(t *testing.T) {
	var tests = []struct {
		reg1, reg2, val1, val2 byte
	}{
		{0, 2, 4, 2},
		{0, 2, 2, 2},
		{15, 1, 2, 0},
		{15, 4, 12, 12},
	}

	for _, tt := range tests {
		testname := fmt.Sprintf("Reg1:%d,Reg2:%d,val1:%d,val2:%d", tt.reg1, tt.reg2, tt.val1, tt.val2)
		t.Run(testname, func(t *testing.T) {
			cpu := Chip8{opcode: uint16(tt.reg1)<<8 + uint16(tt.reg2)<<4}
			cpu.registers[tt.reg1] = tt.val1
			cpu.registers[tt.reg2] = tt.val2
			cpu.skipIfRegistersEqual()
			if (2 != cpu.pc) && (tt.val1 == tt.val2) {
				t.Errorf("PC is %d, Wanted %d", cpu.pc, 2)
			} else if (0 != cpu.pc) && (tt.val1 != tt.val2) {
				t.Errorf("PC is %d, Wanted %d", cpu.pc, 2)
			}
		})
	}
}

func TestSetRegisterTo(t *testing.T) {
	cpu := Chip8{opcode: 0x0824}
	cpu.setRegisterTo()
	if cpu.registers[8] != 0x24 {
		t.Errorf("Register 8 is %d wanted %d", cpu.registers[8], 0x24)
	}
}

func TestRegisterPlusEqualsNN(t *testing.T) {
	var tests = []struct {
		register, initalVal, toAdd, expected byte
	}{
		{0, 2, 2, 4},
		{0, 254, 3, 1},
		{15, 2, 0, 2},
		{15, 250, 6, 0},
	}
	for _, tt := range tests {
		testname := fmt.Sprintf("Register:%d,inital:%d,toAdd:%d,expected:%d", tt.register, tt.initalVal, tt.toAdd, tt.expected)
		t.Run(testname, func(t *testing.T) {
			cpu := Chip8{opcode: uint16(tt.register)<<8 + uint16(tt.toAdd)}
			cpu.registers[tt.register] = tt.initalVal
			cpu.registerPlusEqualsNN()
			if cpu.registers[tt.register] != tt.expected {
				t.Errorf("Register is %d, wanted %d", cpu.registers[tt.register], tt.expected)
			}
		})
	}
}