package tests

import (
	"testing"

	"crecher.net/gones/v2/cart"
	"crecher.net/gones/v2/nes"
)

func newTestConsole(t *testing.T) *nes.Console {
	t.Helper()
	c, err := cart.Load("testdata/nestest.nes")
	if err != nil {
		t.Fatal(err)
	}
	return nes.New(c)
}

func strobe(n *nes.Console) {
	n.Write(0x4016, 1)
	n.Write(0x4016, 0)
}

func readBits(n *nes.Console, addr uint16, count int) []uint8 {
	bits := make([]uint8, count)
	for i := range bits {
		bits[i] = n.Read(addr) & 1
	}
	return bits
}

func equalBits(a, b []uint8) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}

func TestControllerReadsButtonsInOrder(t *testing.T) {
	n := newTestConsole(t)
	n.SetButtons(0, nes.ButtonA|nes.ButtonStart|nes.ButtonRight)
	strobe(n)

	//				+---------------------- A
	//				|  +------------------- B
	//				|  |  +---------------- Select
	//				|  |  |  +------------- Start
	//				|  |  |  |  +---------- Up
	//				|  |  |  |  |  +------- Down
	//				|  |  |  |  |  |  +---- Left
	//				|  |  |  |  |  |  |  +- Right
	//				|  |  |  |  |  |  |  |
	want := []uint8{1, 0, 0, 1, 0, 0, 0, 1}
	if got := readBits(n, 0x4016, 8); !equalBits(got, want) {
		t.Errorf("bits = %v, want %v", got, want)
	}
}

func TestControllerReturnsOneAfterEightReads(t *testing.T) {
	n := newTestConsole(t)
	strobe(n)
	readBits(n, 0x4016, 8)
	if got := readBits(n, 0x4016, 3); !equalBits(got, []uint8{1, 1, 1}) {
		t.Errorf("bits after 8 reads = %v, want [1 1 1]", got)
	}
}

func TestControllerStrobeHighKeepsReturningA(t *testing.T) {
	n := newTestConsole(t)
	n.SetButtons(0, nes.ButtonA)
	n.Write(0x4016, 1)
	if got := readBits(n, 0x4016, 3); !equalBits(got, []uint8{1, 1, 1}) {
		t.Errorf("bits = %v, want [1 1 1]", got)
	}

	n.SetButtons(0, nes.ButtonB)
	if got := readBits(n, 0x4016, 2); !equalBits(got, []uint8{0, 0}) {
		t.Errorf("bits after releasing A = %v, want [0 0]", got)
	}
}

func TestControllerLatchesOnStrobe(t *testing.T) {
	n := newTestConsole(t)
	n.SetButtons(0, nes.ButtonA)
	strobe(n)
	n.SetButtons(0, 0) // released after the latch, the readout should not change

	want := []uint8{1, 0, 0, 0, 0, 0, 0, 0}
	if got := readBits(n, 0x4016, 8); !equalBits(got, want) {
		t.Errorf("bits = %v, want %v", got, want)
	}
}

func TestControllerPortsAreIndependentWithSharedStrobe(t *testing.T) {
	n := newTestConsole(t)
	n.SetButtons(0, nes.ButtonA)
	n.SetButtons(1, nes.ButtonSelect)
	strobe(n)

	if got := readBits(n, 0x4016, 3); !equalBits(got, []uint8{1, 0, 0}) {
		t.Errorf("port 1 bits = %v, want [1 0 0]", got)
	}
	if got := readBits(n, 0x4017, 3); !equalBits(got, []uint8{0, 0, 1}) {
		t.Errorf("port 2 bits = %v, want [0 0 1]", got)
	}
}

func TestControllerReadHasOpenBusBit6(t *testing.T) {
	n := newTestConsole(t)
	strobe(n)
	if got := n.Read(0x4016); got != 0x40 {
		t.Errorf("$4016 with nothing pressed = %#02x, want 0x40", got)
	}
}