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// license:BSD-3-Clause
// copyright-holders:hap
/*

This thing is a generic helper for PWM(strobed) display elements, to prevent
flickering and optionally handle perceived brightness levels.

Common usecase is to call matrix(selmask, datamask), a collision between the
2 masks implies a powered-on display element (eg. a LED, or VFD sprite).
The maximum matrix size is 64 by 64, simply due to uint64_t constraints.
If a larger size is needed, create an array of pwm_display_device.

If display elements are directly addressable, you can also use write_element
or write_row to set them.

Display element states are sent to output tags "y.x" where y is the matrix row
number, x is the row bit. It is also sent to "y.a" for all rows. The output state
is 0 for off, and >0 for on, depending on brightness level.

If segmask is defined, it is also sent to "multiy.b" where b is brightness level,
for use with multi-state elements. This usecase is not common though (one example
is Coleco Quarterback where some digit segments are brighter). And when brightness
level does not matter, it is also sent to "digity", for common 7seg leds.

If you use this device in a slot, or use multiple of them (or just don't want
to use the default output tags), set a callback.

Brightness tresholds (0.0 to 1.0) indicate how long an element was powered on
in the last frame, eg. 0.01 means a minimum on-time for 1%. Some games use two
levels of brightness by strobing elements longer.

TODO:
- SVG screens and rendlay digit elements don't support multiple brightness levels,
  the latter can be worked around with by stacking digits on top of eachother

*/

#include "emu.h"
#include "pwm.h"

#include <algorithm>


DEFINE_DEVICE_TYPE(PWM_DISPLAY, pwm_display_device, "pwm_display", "PWM Display")

//-------------------------------------------------
//  constructor
//-------------------------------------------------

pwm_display_device::pwm_display_device(const machine_config &mconfig, const char *tag, device_t *owner, u32 clock) :
	device_t(mconfig, PWM_DISPLAY, tag, owner, clock),
	m_out_x(*this, "%u.%u", 0U, 0U),
	m_out_a(*this, "%u.a", 0U),
	m_out_multi(*this, "multi%u.%u", 0U, 0U),
	m_out_digit(*this, "digit%u", 0U),
	m_output_x_cb(*this),
	m_output_a_cb(*this),
	m_output_multi_cb(*this),
	m_output_digit_cb(*this)
{
	// set defaults
	set_refresh(attotime::from_hz(60));
	set_interpolation(0.5);
	set_bri_levels(0.01);
	set_bri_minimum(0);
	set_bri_maximum(0.0);
	set_size(0, 0);
	reset_segmask();
}


//-------------------------------------------------
//  device_start/reset
//-------------------------------------------------

void pwm_display_device::device_start()
{
	// resolve handlers
	m_external_output = !m_output_x_cb.isunset() || !m_output_a_cb.isunset() || !m_output_multi_cb.isunset() || !m_output_digit_cb.isunset();

	if (!m_external_output)
	{
		m_out_x.resolve();
		m_out_a.resolve();
		m_out_multi.resolve();
		m_out_digit.resolve();
	}

	// initialize
	m_rowsel = 0;
	m_rowdata_last = 0;
	std::fill(std::begin(m_rowdata), std::end(m_rowdata), 0);

	for (auto &bri : m_bri)
		std::fill(std::begin(bri), std::end(bri), 0.0);

	m_frame_timer = timer_alloc(FUNC(pwm_display_device::frame_tick), this);
	m_sync_time = machine().time();

	// register for savestates
	save_item(NAME(m_width));
	save_item(NAME(m_height));
	save_item(NAME(m_framerate_set));
	save_item(NAME(m_framerate));
	save_item(NAME(m_interpolation));
	save_item(NAME(m_levels));
	save_item(NAME(m_level_min));
	save_item(NAME(m_level_max));

	save_item(NAME(m_segmask));
	save_item(NAME(m_rowsel));
	save_item(NAME(m_rowdata));
	save_item(NAME(m_rowdata_last));

	save_item(NAME(m_bri));
	save_item(NAME(m_sync_time));
	save_item(NAME(m_acc));
}

void pwm_display_device::device_reset()
{
	if (m_height > 64 || m_width > 64)
		fatalerror("%s: Invalid size %d*%d, maximum is 64*64!\n", tag(), m_height, m_width);

	schedule_frame();
	m_sync_time = machine().time();
}


//-------------------------------------------------
//  public handlers (most of the interface is in the .h file)
//-------------------------------------------------

pwm_display_device &pwm_display_device::set_bri_levels(double l0, double l1, double l2, double l3)
{
	// init brightness level(s) (if you need to set more than 4, use set_bri_one)
	reset_bri_levels();
	set_bri_one(0, l0);
	set_bri_one(1, l1);
	set_bri_one(2, l2);
	set_bri_one(3, l3);

	return *this;
}

pwm_display_device &pwm_display_device::set_segmask(u64 digits, u64 mask)
{
	// set a segment mask per selected digit, but leave unselected ones alone
	for (int y = 0; y < m_height; y++)
	{
		if (digits & 1)
			m_segmask[y] = mask;
		digits >>= 1;
	}

	return *this;
}

void pwm_display_device::matrix_partial(u8 start, u8 height, u64 rowsel, u64 rowdata)
{
	sync();

	u64 selmask = (u64(1) << height) - 1;
	rowsel &= selmask;
	selmask <<= start;
	m_rowsel = (m_rowsel & ~selmask) | (rowsel << start);

	// update selected rows
	u64 rowmask = (u64(1) << m_width) - 1;
	m_rowdata_last = rowdata & rowmask;
	for (int y = start; y < (start + height) && y < m_height; y++)
	{
		m_rowdata[y] = (rowsel & 1) ? (rowdata & rowmask) : 0;
		rowsel >>= 1;
	}
}


//-------------------------------------------------
//  internal handlers
//-------------------------------------------------

void pwm_display_device::schedule_frame()
{
	std::fill_n(*m_acc, m_height * std::size(m_acc[0]), attotime::zero);

	m_framerate = m_framerate_set;
	m_frame_timer->adjust(m_framerate);
}

TIMER_CALLBACK_MEMBER(pwm_display_device::frame_tick)
{
	const double frame_time = m_framerate.as_double();
	const double factor0 = m_interpolation;
	const double factor1 = 1.0 - factor0;

	// determine brightness cutoff
	u8 max_levels = 1;
	for (; m_levels[max_levels] < 1.0; max_levels++) { ; }
	double cutoff = m_level_max;

	if (cutoff == 0.0)
		cutoff = 4 * m_levels[max_levels - 1];
	if (cutoff > 1.0)
		cutoff = 1.0;

	sync(); // final timeslice

	for (int y = 0; y < m_height; y++)
	{
		u64 multi_row[0x40];
		std::fill(std::begin(multi_row), std::end(multi_row), 0);

		for (int x = 0; x <= m_width; x++)
		{
			// determine brightness level
			double bri = m_bri[y][x] * factor1 + (m_acc[y][x].as_double() / frame_time) * factor0;
			if (bri > cutoff)
				bri = cutoff;
			m_bri[y][x] = bri;

			u8 level;
			for (level = 0; bri > m_levels[level]; level++) { ; }

			// output to y.x, or y.a when always-on
			if (x != m_width)
			{
				multi_row[level] |= (u64(1) << x);

				if (m_external_output)
					m_output_x_cb(x << 6 | y, level);
				else
					m_out_x[y][x] = level;
			}
			else
			{
				if (m_external_output)
					m_output_a_cb(y, level);
				else
					m_out_a[y] = level;
			}
		}

		// multi-state outputs
		if (m_segmask[y] != 0)
		{
			u64 digit_row = 0;

			for (int b = 0; b <= max_levels; b++)
			{
				multi_row[b] &= m_segmask[y];
				if (b > m_level_min)
					digit_row |= multi_row[b];

				// output to multiy.b
				if (m_external_output)
					m_output_multi_cb(b << 6 | y, digit_row);
				else
					m_out_multi[y][b] = multi_row[b];
			}

			// output to digity (single brightness level)
			if (m_external_output)
				m_output_digit_cb(y, digit_row);
			else
				m_out_digit[y] = digit_row;
		}
	}

	schedule_frame();
}

void pwm_display_device::sync()
{
	const attotime now = machine().time();
	const attotime last = m_sync_time;
	m_sync_time = now;

	if (last >= now)
		return;

	const attotime diff = now - last;
	u64 sel = m_rowsel;

	// accumulate active time
	for (int y = 0; y < m_height; y++)
	{
		u64 row = m_rowdata[y];

		if (sel & 1)
			m_acc[y][m_width] += diff;

		for (int x = 0; x < m_width; x++)
		{
			if (row & 1)
				m_acc[y][x] += diff;
			row >>= 1;
		}
		sel >>= 1;
	}
}