// license:BSD-3-Clause
// copyright-holders:Wilbert Pol
/******************************************************************************
    Acorn Electron driver

    MESS Driver By:

    Wilbert Pol

******************************************************************************/

#include "emu.h"
#include "includes/electron.h"
#include "sound/beep.h"
#include "imagedev/cassette.h"


void electron_state::waitforramsync()
{
	int cycles = 0;

	if (!(m_ula.screen_mode & 4) && machine().first_screen()->hpos()<640)
	{
		cycles += (640 - machine().first_screen()->hpos()) / 8;
	}
	if (cycles & 1) cycles++;

	m_maincpu->adjust_icount(-cycles);
}


void electron_state::device_timer(emu_timer &timer, device_timer_id id, int param, void *ptr)
{
	switch (id)
	{
	case TIMER_TAPE_HANDLER:
		electron_tape_timer_handler(ptr, param);
		break;
	case TIMER_SETUP_BEEP:
		setup_beep(ptr, param);
		break;
	case TIMER_SCANLINE_INTERRUPT:
		electron_scanline_interrupt(ptr, param);
		break;
	default:
		assert_always(false, "Unknown id in electron_state::device_timer");
	}
}


void electron_state::electron_tape_start()
{
	if (m_ula.tape_running )
	{
		return;
	}
	m_ula.tape_steps = 0;
	m_ula.tape_value = 0x80808080;
	m_ula.high_tone_set = 0;
	m_ula.bit_count = 0;
	m_ula.tape_running = 1;
	m_tape_timer->adjust(attotime::zero, 0, attotime::from_hz(4800));
}

void electron_state::electron_tape_stop()
{
	m_ula.tape_running = 0;
	m_tape_timer->reset();
}

#define TAPE_LOW    0x00;
#define TAPE_HIGH   0xFF;

TIMER_CALLBACK_MEMBER(electron_state::electron_tape_timer_handler)
{
	if ( m_ula.cassette_motor_mode )
	{
		double tap_val;
		tap_val = m_cassette->input();
		if ( tap_val < -0.5 )
		{
			m_ula.tape_value = ( m_ula.tape_value << 8 ) | TAPE_LOW;
			m_ula.tape_steps++;
		}
		else if ( tap_val > 0.5 )
		{
			m_ula.tape_value = ( m_ula.tape_value << 8 ) | TAPE_HIGH;
			m_ula.tape_steps++;
		}
		else
		{
			m_ula.tape_steps = 0;
			m_ula.bit_count = 0;
			m_ula.high_tone_set = 0;
			m_ula.tape_value = 0x80808080;
		}
		if ( m_ula.tape_steps > 2 && ( m_ula.tape_value == 0x0000FFFF || m_ula.tape_value == 0x00FF00FF ) )
		{
			m_ula.tape_steps = 0;
			switch( m_ula.bit_count )
			{
			case 0: /* start bit */
				m_ula.start_bit = ( ( m_ula.tape_value == 0x0000FFFF ) ? 0 : 1 );
				//logerror( "++ Read start bit: %d\n", m_ula.start_bit );
				if ( m_ula.start_bit )
				{
					if ( m_ula.high_tone_set )
					{
						m_ula.bit_count--;
					}
				}
				else
				{
					m_ula.high_tone_set = 0;
				}
				break;
			case 1: case 2: case 3: case 4:
			case 5: case 6: case 7: case 8:
				//logerror( "++ Read regular bit: %d\n", m_ula.tape_value == 0x0000FFFF ? 0 : 1 );
				m_ula.tape_byte = ( m_ula.tape_byte >> 1 ) | ( m_ula.tape_value == 0x0000FFFF ? 0 : 0x80 );
				break;
			case 9: /* stop bit */
				m_ula.stop_bit = ( ( m_ula.tape_value == 0x0000FFFF ) ? 0 : 1 );
				//logerror( "++ Read stop bit: %d\n", m_ula.stop_bit );
				if ( m_ula.start_bit && m_ula.stop_bit && m_ula.tape_byte == 0xFF && ! m_ula.high_tone_set )
				{
					electron_interrupt_handler( INT_SET, INT_HIGH_TONE );
					m_ula.high_tone_set = 1;
				}
				else if ( ! m_ula.start_bit && m_ula.stop_bit )
				{
					//logerror( "-- Byte read from tape: %02x\n", m_ula.tape_byte );
					electron_interrupt_handler( INT_SET, INT_RECEIVE_FULL );
				}
				else
				{
					logerror( "Invalid start/stop bit combination detected: %d,%d\n", m_ula.start_bit, m_ula.stop_bit );
				}
				break;
			}
			m_ula.bit_count = ( m_ula.bit_count + 1 ) % 10;
		}
	}
}

READ8_MEMBER(electron_state::electron_read_keyboard)
{
	uint8_t data = 0;

	//logerror( "PC=%04x: keyboard read from paged rom area, address: %04x", activecpu_get_pc(), offset );
	for (int i = 0; i < 14; i++)
	{
		if (!(offset & 1))
			data |= m_keybd[i]->read() & 0x0f;

		offset = offset >> 1;
	}
	//logerror( ", data: %02x\n", data );
	return data;
}

READ8_MEMBER(electron_state::electron_mem_r)
{
	//waitforramsync();
	return m_ram->read(offset);
}

WRITE8_MEMBER(electron_state::electron_mem_w)
{
	//waitforramsync();
	m_ram->write(offset, data);
}

READ8_MEMBER(electron_state::electron_fred_r)
{
	logerror("FRED: read fc%02x\n", offset);
	return 0xff;
}

WRITE8_MEMBER(electron_state::electron_fred_w)
{
}

READ8_MEMBER(electron_state::electron_jim_r)
{
	logerror("JIM: read fd%02x\n", offset);
	return 0xff;
}

WRITE8_MEMBER(electron_state::electron_jim_w)
{
}

READ8_MEMBER(electron_state::electron_sheila_r)
{
	uint8_t data = ((uint8_t *)memregion("user1")->base())[0x43E00 + offset];
	switch ( offset & 0x0f )
	{
	case 0x00:  /* Interrupt status */
		data = m_ula.interrupt_status;
		m_ula.interrupt_status &= ~0x02;
		break;
	case 0x01:  /* Unknown */
		break;
	case 0x04:  /* Cassette data shift register */
		electron_interrupt_handler(INT_CLEAR, INT_RECEIVE_FULL );
		data = m_ula.tape_byte;
		break;
	}
	logerror( "ULA: read offset %02x: %02x\n", offset, data );
	return data;
}

static const int electron_palette_offset[4] = { 0, 4, 5, 1 };
static const uint16_t electron_screen_base[8] = { 0x3000, 0x3000, 0x3000, 0x4000, 0x5800, 0x5800, 0x6000, 0x5800 };

WRITE8_MEMBER(electron_state::electron_sheila_w)
{
	int i = electron_palette_offset[(( offset >> 1 ) & 0x03)];
	logerror( "ULA: write offset %02x <- %02x\n", offset & 0x0f, data );
	switch( offset & 0x0f )
	{
	case 0x00:  /* Interrupt control */
		m_ula.interrupt_control = data;
		break;
	case 0x01:  /* Unknown */
		break;
	case 0x02:  /* Screen start address #1 */
		m_ula.screen_start = ( m_ula.screen_start & 0x7e00 ) | ( ( data & 0xe0 ) << 1 );
		logerror( "screen_start changed to %04x\n", m_ula.screen_start );
		break;
	case 0x03:  /* Screen start address #2 */
		m_ula.screen_start = ( m_ula.screen_start & 0x1c0 ) | ( ( data & 0x3f ) << 9 );
		logerror( "screen_start changed to %04x\n", m_ula.screen_start );
		break;
	case 0x04:  /* Cassette data shift register */
		break;
	case 0x05:  /* Interrupt clear and paging */
		/* rom page requests are honoured when currently bank 0-7 or 12-15 is switched in,
		 * or when 8-11 is currently switched in only switching to bank 8-15 is allowed.
		 *
		 * Rompages 10 and 11 both select the Basic ROM.
		 * Rompages 8 and 9 both select the keyboard.
		 */
		if ( ( ( m_ula.rompage & 0x0C ) != 0x08 ) || ( data & 0x08 ) )
		{
			m_ula.rompage = data & 0x0f;
			if ( m_ula.rompage == 8 || m_ula.rompage == 9 )
			{
				m_ula.rompage = 8;
				space.install_read_handler( 0x8000, 0xbfff, read8_delegate(FUNC(electron_state::electron_read_keyboard),this));
			}
			else
			{
				space.install_read_bank( 0x8000, 0xbfff, "bank2");
			}
			membank("bank2")->set_entry(m_ula.rompage);
		}
		if ( data & 0x10 )
		{
			electron_interrupt_handler( INT_CLEAR, INT_DISPLAY_END );
		}
		if ( data & 0x20 )
		{
			electron_interrupt_handler( INT_CLEAR, INT_RTC );
		}
		if ( data & 0x40 )
		{
			electron_interrupt_handler( INT_CLEAR, INT_HIGH_TONE );
		}
		if ( data & 0x80 )
		{
		}
		break;
	case 0x06:  /* Counter divider */
		if ( m_ula.communication_mode == 0x01)
		{
		/* GUESS
		 * the Advanced Users manual says this is the correct algorithm
		 * but the divider is wrong(?), says 16 but results in high pitch,
		 * 32 is more close
		 */
			m_beeper->set_clock( 1000000 / ( 32 * ( data + 1 ) ) );
		}
		break;
	case 0x07:  /* Misc. */
		m_ula.communication_mode = ( data >> 1 ) & 0x03;
		switch( m_ula.communication_mode )
		{
		case 0x00:  /* cassette input */
			m_beeper->set_state( 0 );
			electron_tape_start();
			break;
		case 0x01:  /* sound generation */
			m_beeper->set_state( 1 );
			electron_tape_stop();
			break;
		case 0x02:  /* cassette output */
			m_beeper->set_state( 0 );
			electron_tape_stop();
			break;
		case 0x03:  /* not used */
			m_beeper->set_state( 0 );
			electron_tape_stop();
			break;
		}
		m_ula.screen_mode = ( data >> 3 ) & 0x07;
		m_ula.screen_base = electron_screen_base[ m_ula.screen_mode ];
		m_ula.screen_size = 0x8000 - m_ula.screen_base;
		m_ula.vram = (uint8_t *)m_ram->pointer() + m_ula.screen_base;
		logerror( "ULA: screen mode set to %d\n", m_ula.screen_mode );
		m_ula.cassette_motor_mode = ( data >> 6 ) & 0x01;
		m_cassette->change_state(m_ula.cassette_motor_mode ? CASSETTE_MOTOR_ENABLED : CASSETTE_MOTOR_DISABLED, CASSETTE_MOTOR_DISABLED );
		m_ula.capslock_mode = ( data >> 7 ) & 0x01;
		break;
	case 0x08: case 0x0A: case 0x0C: case 0x0E:
		// video_update
		m_ula.current_pal[i+10] = (m_ula.current_pal[i+10] & 0x01) | (((data & 0x80) >> 5) | ((data & 0x08) >> 1));
		m_ula.current_pal[i+8] = (m_ula.current_pal[i+8] & 0x01) | (((data & 0x40) >> 4) | ((data & 0x04) >> 1));
		m_ula.current_pal[i+2] = (m_ula.current_pal[i+2] & 0x03) | ((data & 0x20) >> 3);
		m_ula.current_pal[i] = (m_ula.current_pal[i] & 0x03) | ((data & 0x10) >> 2);
		break;
	case 0x09: case 0x0B: case 0x0D: case 0x0F:
		// video_update
		m_ula.current_pal[i+10] = (m_ula.current_pal[i+10] & 0x06) | ((data & 0x08) >> 3);
		m_ula.current_pal[i+8] = (m_ula.current_pal[i+8] & 0x06) | ((data & 0x04) >> 2);
		m_ula.current_pal[i+2] = (m_ula.current_pal[i+2] & 0x04) | (((data & 0x20) >> 4) | ((data & 0x02) >> 1));
		m_ula.current_pal[i] = (m_ula.current_pal[i] & 0x04) | (((data & 0x10) >> 3) | ((data & 0x01)));
		break;
	}
}

void electron_state::electron_interrupt_handler(int mode, int interrupt)
{
	if ( mode == INT_SET )
	{
		m_ula.interrupt_status |= interrupt;
	}
	else
	{
		m_ula.interrupt_status &= ~interrupt;
	}
	if ( m_ula.interrupt_status & m_ula.interrupt_control & ~0x83 )
	{
		m_ula.interrupt_status |= 0x01;
		m_maincpu->set_input_line(0, ASSERT_LINE );
	}
	else
	{
		m_ula.interrupt_status &= ~0x01;
		m_maincpu->set_input_line(0, CLEAR_LINE );
	}
}

/**************************************
   Machine Initialisation functions
***************************************/

TIMER_CALLBACK_MEMBER(electron_state::setup_beep)
{
	m_beeper->set_state( 0 );
	m_beeper->set_clock( 300 );
}

void electron_state::machine_reset()
{
	membank("bank2")->set_entry(0);

	m_ula.communication_mode = 0x04;
	m_ula.screen_mode = 0;
	m_ula.cassette_motor_mode = 0;
	m_ula.capslock_mode = 0;
	m_ula.screen_start = 0x3000;
	m_ula.screen_base = 0x3000;
	m_ula.screen_size = 0x8000 - 0x3000;
	m_ula.screen_addr = 0;
	m_ula.tape_running = 0;
	m_ula.vram = (uint8_t *)m_ram->pointer() + m_ula.screen_base;
}

void electron_state::machine_start()
{
	uint8_t *lo_rom, *up_rom;
	std::string region_tag;
	memory_region *cart_rom = memregion(region_tag.assign(m_cart->tag()).append(GENERIC_ROM_REGION_TAG).c_str());

	if (cart_rom)
		up_rom = cart_rom->base();
	else
		up_rom = memregion("user1")->base() + 12 * 0x4000;
	if (cart_rom && cart_rom->bytes() > 0x4000)
		lo_rom = cart_rom->base() + 0x4000;
	else
		lo_rom = memregion("user1")->base();

	membank("bank2")->configure_entries(0, 1, lo_rom, 0x4000);
	membank("bank2")->configure_entries(1, 1, up_rom, 0x4000);

	for (int page = 2; page < 16; page++)
		membank("bank2")->configure_entries(page, 1, memregion("user1")->base() + page * 0x4000, 0x4000);

	m_ula.interrupt_status = 0x82;
	m_ula.interrupt_control = 0x00;
	timer_set(attotime::zero, TIMER_SETUP_BEEP);
	m_tape_timer = timer_alloc(TIMER_TAPE_HANDLER);
}

DEVICE_IMAGE_LOAD_MEMBER( electron_state, electron_cart )
{
	if (image.software_entry() == nullptr)
	{
		uint32_t filesize = image.length();

		if (filesize != 16384)
		{
			image.seterror(IMAGE_ERROR_UNSPECIFIED, "Invalid size: Only size 16384 is supported");
			return image_init_result::FAIL;
		}

		m_cart->rom_alloc(filesize, GENERIC_ROM8_WIDTH, ENDIANNESS_LITTLE);
		image.fread(m_cart->get_rom_base(), filesize);
		return image_init_result::PASS;
	}
	else
	{
		int upsize = image.get_software_region_length("uprom");
		int losize = image.get_software_region_length("lorom");

		if (upsize != 16384 && upsize != 0)
		{
			image.seterror(IMAGE_ERROR_UNSPECIFIED, "Invalid size for uprom");
			return image_init_result::FAIL;
		}

		if (losize != 16384 && losize != 0)
		{
			image.seterror(IMAGE_ERROR_UNSPECIFIED, "Invalid size for lorom");
			return image_init_result::FAIL;
		}

		m_cart->rom_alloc(upsize + losize, GENERIC_ROM8_WIDTH, ENDIANNESS_LITTLE);

		if (upsize)
			memcpy(m_cart->get_rom_base(), image.get_software_region("uprom"), upsize);

		if (losize)
			memcpy(m_cart->get_rom_base() + upsize, image.get_software_region("lorom"), losize);

		return image_init_result::PASS;
	}
}
