use ferris_boi::{
    cpu::{instructions::Instruction, Processor},
    register,
};

use crate::testutil;

use test_case::test_case;

#[test_case(0x32, 0x64, 0x63)]
#[test_case(0x22, 0x64, 0x65)]
fn test_load_to_register_address_then_do_arithmetic(
    opcode: u8,
    hl_value_before: u16,
    hl_value_after: u16,
) {
    let mut processor = Processor::default();
    processor
        .registers
        .set_combined_register(register::Combined::HL, hl_value_before);
    processor.registers.a = 10;

    let data = [opcode, 0x00];
    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x00]);
    processor.run_instruction(ins);
    assert_eq!(10, processor.memory.get(hl_value_before.into()).unwrap());
    assert_eq!(
        hl_value_after,
        processor
            .registers
            .get_combined_register(register::Combined::HL)
    );
}

#[test_case(0x01, register::SixteenBit::Combined(register::Combined::BC))]
#[test_case(0x11, register::SixteenBit::Combined(register::Combined::DE))]
#[test_case(0x21, register::SixteenBit::Combined(register::Combined::HL))]
#[test_case(
    0x31,
    register::SixteenBit::Single(register::SingleSixteenBit::StackPointer)
)]
fn test_load_16bit_immediate_to_register(opcode: u8, expected_dst_register: register::SixteenBit) {
    let mut processor = Processor::default();
    // The manual doesn't specify this is little endian, but from what I can gather
    // from googling, it should be.
    //
    // Note this excerpt from the Tetris disassembly
    // l05c0:  ld      hl,0ff02h       ; 05c0 21 02 ff   !..
    let data = [opcode, 0x34, 0x12, 0x05];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x05]);
    processor.run_instruction(ins);

    assert_eq!(
        0x1234,
        processor
            .registers
            .get_16bit_register(expected_dst_register)
    );
}

#[test]
fn test_load_from_hl_to_sp() {
    let mut processor = Processor::default();
    processor
        .registers
        .set_combined_register(register::Combined::HL, 0x1234);
    let data = [0xF9, 0x00];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x00]);
    processor.run_instruction(ins);

    assert_eq!(0x1234, processor.registers.stack_pointer);
}

#[test_case(0xFF00, 0, 0xFF00)]
#[test_case(0xFF00, 16, 0xFF10)]
#[test_case(0xFF00, -5, 0xFEFB)]
#[test_case(0xFF00, 127, 0xFF7F)]
#[test_case(0xFF00, -127, 0xFE81)]
#[test_case(0xFF00, -128, 0xFE80)]
#[test_case(0xFFFF, 10, 0x0009)]
fn test_load_effective_address(start_sp: u16, value: i8, expected_sp: u16) {
    let mut processor = Processor::default();
    processor.registers.set_16bit_register(
        register::SixteenBit::Single(register::SingleSixteenBit::StackPointer),
        start_sp,
    );

    let unsigned_value = if value >= 0 {
        value as u8
    } else if value == i8::MIN {
        i8::MIN.unsigned_abs()
    } else {
        !(value.unsigned_abs()) + 1
    };

    let data = [0xF8, unsigned_value, 0x00];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x00]);
    processor.run_instruction(ins);

    assert_eq!(
        expected_sp,
        processor
            .registers
            .get_combined_register(register::Combined::HL)
    );
}

#[test_case(0x0000, 0x00, 0, 0; "no addition")]
#[test_case(0x00FF, 0x20, 0, 1; "overflow")]
#[test_case(0x00C0, 0x7f, 0, 1; "overflow 2")]
#[test_case(0x00FF, 0x01, 1, 1; "overflow with half carry")]
#[test_case(0x000A, 0x0C, 1, 0; "half carry")]
#[test_case(0x0018, -0x4, 1, 1; "negative both carry")]
#[test_case(0x000F, -0x01, 1, 1; "underflow with half carry")]
#[test_case(0x00FE, -0x0F, 0, 1; "underflow with no half carry")]
#[test_case(0xFFFF, 0xA, 1, 1; "16 bit overflow results in both carries")]
fn test_load_effective_address_flags(starting_sp: u16, add_value: i8, half_carry: u8, carry: u8) {
    let mut processor = Processor::default();
    processor.registers.stack_pointer = starting_sp;

    let unsigned_value = if add_value >= 0 {
        add_value as u8
    } else if add_value == i8::MIN {
        i8::MIN.unsigned_abs()
    } else {
        !(add_value.unsigned_abs()) + 1
    };

    let data = [0xF8, unsigned_value, 0x00];
    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x00]);
    processor.run_instruction(ins);

    testutil::assert_flags_eq!(
        processor,
        (register::Flag::HalfCarry, half_carry),
        (register::Flag::Carry, carry),
        (register::Flag::Zero, 0),
        (register::Flag::Subtract, 0),
    );
}

#[test_case(0xC5, register::Combined::BC)]
#[test_case(0xD5, register::Combined::DE)]
#[test_case(0xE5, register::Combined::HL)]
fn test_stack_push(opcode: u8, src: register::Combined) {
    let mut processor = Processor::default();
    processor.registers.set_combined_register(src, 0x1234);
    processor.registers.stack_pointer = 0xFFFE;
    let data = [opcode, 0x01];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x01]);
    processor.run_instruction(ins);

    // we want to pop the LSB first (i.e. we write the MSB first)
    // https://rgbds.gbdev.io/docs/v0.5.2/gbz80.7#PUSH_r16
    assert_eq!(0x12, processor.memory.get(0xFFFE - 1).unwrap());
    assert_eq!(0x34, processor.memory.get(0xFFFE - 2).unwrap());
    assert_eq!(0xFFFE - 2, processor.registers.stack_pointer);
}

#[test]
fn test_stack_push_from_af() {
    let mut processor = Processor::default();
    processor
        .registers
        .set_combined_register(register::Combined::AF, 0x1234);
    processor.registers.stack_pointer = 0xFFFE;
    let data = [0xF5, 0x01];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x01]);
    processor.run_instruction(ins);

    // we want to pop the LSB first (i.e. we write the MSB first)
    // https://rgbds.gbdev.io/docs/v0.5.2/gbz80.7#PUSH_r16
    assert_eq!(0x12, processor.memory.get(0xFFFE - 1).unwrap());
    assert_eq!(0x30, processor.memory.get(0xFFFE - 2).unwrap());
    assert_eq!(0xFFFE - 2, processor.registers.stack_pointer);
}

#[test_case(0xC1, register::Combined::BC)]
#[test_case(0xD1, register::Combined::DE)]
#[test_case(0xE1, register::Combined::HL)]
fn test_stack_pop(opcode: u8, dst: register::Combined) {
    let mut processor = Processor::default();
    processor.registers.stack_pointer = 0xFFF0;
    processor
        .memory
        .set_both(((0xFFF0, 0x34), (0xFFF1, 0x12)))
        .expect("failed to set values in memory");
    let data = [opcode, 0x01];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x01]);
    processor.run_instruction(ins);

    assert_eq!(0x1234, processor.registers.get_combined_register(dst));
    assert_eq!(0xFFF0 + 2, processor.registers.stack_pointer);
}

#[test]
fn test_stack_pop_to_af() {
    let mut processor = Processor::default();
    processor.registers.stack_pointer = 0xFFF0;
    processor
        .memory
        .set_both(((0xFFF0, 0x34), (0xFFF1, 0x12)))
        .expect("failed to set values in memory");
    let data = [0xF1, 0x01];

    let (ins, extra_data) = Instruction::from_data(&data).expect("could not parse instruction");

    assert_eq!(extra_data, &[0x01]);
    processor.run_instruction(ins);

    assert_eq!(
        0x1230,
        processor
            .registers
            .get_combined_register(register::Combined::AF)
    );
    assert_eq!(0xFFF0 + 2, processor.registers.stack_pointer);
}