#include <assert.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "til.h"
#include "til_fb.h"
#include "til_module_context.h"
#include "til_settings.h"
#include "til_stream.h"
#include "til_tap.h"
#include "til_util.h"

/* Copyright (C) 2023 - Vito Caputo <vcaputo@pengaru.com> */

/* This implements a rudimentary mixing module for things like fades */

typedef enum mixer_style_t {
	MIXER_STYLE_FADE,
	MIXER_STYLE_FLICKER,
} mixer_style_t;

typedef struct mixer_input_t {
	til_module_context_t	*module_ctxt;
	/* XXX: it's expected that inputs will get more settable attributes to stick in here */
} mixer_input_t;

typedef struct mixer_context_t {
	til_module_context_t	til_module_context;

	struct {
		til_tap_t		T;
	}			taps;

	struct {
		float			T;
	}			vars;

	float			*T;

	mixer_input_t		inputs[2];
	til_fb_fragment_t	*snapshots[2];
} mixer_context_t;

typedef struct mixer_setup_input_t {
	char			*module;
	til_setup_t		*setup;
} mixer_setup_input_t;

typedef struct mixer_setup_t {
	til_setup_t		til_setup;

	mixer_style_t		style;
	mixer_setup_input_t	inputs[2];
} mixer_setup_t;

#define MIXER_DEFAULT_STYLE	MIXER_STYLE_FADE


static void mixer_update_taps(mixer_context_t *ctxt, til_stream_t *stream, unsigned ticks)
{
	if (!til_stream_tap_context(stream, &ctxt->til_module_context, NULL, &ctxt->taps.T))
		*ctxt->T = cosf(ticks * .001f) * .5f + .5f;
	else /* we're not driving the tap, so let's update our local copy just once */
		ctxt->vars.T = *ctxt->T; /* FIXME: taps need synchronization/thread-safe details fleshed out / atomics */
}


static til_module_context_t * mixer_create_context(const til_module_t *module, til_stream_t *stream, unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup)
{
	mixer_setup_t	*s = (mixer_setup_t *)setup;
	mixer_context_t	*ctxt;
	int		r;

	assert(setup);

	ctxt = til_module_context_new(module, sizeof(mixer_context_t), stream, seed, ticks, n_cpus, setup);
	if (!ctxt)
		return NULL;

	for (size_t i = 0; i < nelems(s->inputs); i++) {
		const til_module_t	*input_module;

		input_module = til_lookup_module(((mixer_setup_t *)setup)->inputs[i].module);
		r =  til_module_create_context(input_module, stream, rand_r(&seed), ticks, n_cpus, s->inputs[i].setup, &ctxt->inputs[i].module_ctxt);
		if (r < 0)
			return til_module_context_free(&ctxt->til_module_context);
	}

	ctxt->taps.T = til_tap_init_float(ctxt, &ctxt->T, 1, &ctxt->vars.T, "T");
	mixer_update_taps(ctxt, stream, ticks);

	return &ctxt->til_module_context;
}


static void mixer_destroy_context(til_module_context_t *context)
{
	mixer_context_t	*ctxt = (mixer_context_t *)context;

	for (size_t i = 0; i < nelems(ctxt->inputs); i++)
		til_module_context_free(ctxt->inputs[i].module_ctxt);

	free(context);
}


static inline float randf(unsigned *seed)
{
	return 1.f / ((float)RAND_MAX) * rand_r(seed);
}


static void mixer_prepare_frame(til_module_context_t *context, til_stream_t *stream, unsigned ticks, til_fb_fragment_t **fragment_ptr, til_frame_plan_t *res_frame_plan)
{
	mixer_context_t		*ctxt = (mixer_context_t *)context;
	til_fb_fragment_t	*fragment = *fragment_ptr;
	size_t			i = 0;

	*res_frame_plan = (til_frame_plan_t){ .fragmenter = til_fragmenter_slice_per_cpu_x16 };

	mixer_update_taps(ctxt, stream, ticks);

	switch (((mixer_setup_t *)context->setup)->style) {
	case MIXER_STYLE_FLICKER:
		if (randf(&context->seed) < ctxt->vars.T)
			i = 1;
		else
			i = 0;

		til_module_render(ctxt->inputs[i].module_ctxt, stream, ticks, &fragment);
		break;

	case MIXER_STYLE_FADE: {
		float	T = ctxt->vars.T;

		if (T < 1.f) {
			til_module_render(ctxt->inputs[0].module_ctxt, stream, ticks, &fragment);

			if (T > 0.f)
				ctxt->snapshots[0] = til_fb_fragment_snapshot(&fragment, 0);
		}

		if (T > 0.f) {
			til_module_render(ctxt->inputs[1].module_ctxt, stream, ticks, &fragment);
			if (T < 1.f)
				ctxt->snapshots[1] = til_fb_fragment_snapshot(&fragment, 0);
		}
		break;
	}

	default:
		assert(0);
	}

	*fragment_ptr = fragment;
}


/* derived from modules/drizzle pixel_mult_scalar(), there's definitely room for optimizations */
static inline uint32_t pixels_lerp(uint32_t a_pixel, uint32_t b_pixel, float one_sub_T, float T)
{
	uint32_t	pixel;
	float		a, b;

	/* r */
	a = ((uint8_t)(a_pixel >> 16));
	a *= one_sub_T;
	b = ((uint8_t)(b_pixel >> 16));
	b *= T;

	pixel = (((uint32_t)(a+b)) << 16);

	/* g */
	a = ((uint8_t)(a_pixel >> 8));
	a *= one_sub_T;
	b = ((uint8_t)(b_pixel >> 8));
	b *= T;

	pixel |= (((uint32_t)(a+b)) << 8);

	/* b */
	a = ((uint8_t)a_pixel);
	a *= one_sub_T;
	b = ((uint8_t)b_pixel);
	b *= T;

	pixel |= ((uint32_t)(a+b));

	return pixel;
}


static void mixer_render_fragment(til_module_context_t *context, til_stream_t *stream, unsigned ticks, unsigned cpu, til_fb_fragment_t **fragment_ptr)
{
	mixer_context_t		*ctxt = (mixer_context_t *)context;
	til_fb_fragment_t	*fragment = *fragment_ptr;

	switch (((mixer_setup_t *)context->setup)->style) {
	case MIXER_STYLE_FLICKER:
		/* handled in prepare_frame() */
		break;

	case MIXER_STYLE_FADE: {
		uint32_t		*dest = fragment->buf;
		til_fb_fragment_t	*snapshot_a, *snapshot_b;
		uint32_t		*a, *b;
		float			T = ctxt->vars.T;
		float			one_sub_T = 1.f - T;

		if (T <= 0.f || T  >= 1.f)
			break;

		assert(ctxt->snapshots[0]);
		assert(ctxt->snapshots[1]);

		snapshot_a = ctxt->snapshots[0];
		snapshot_b = ctxt->snapshots[1];
		a = snapshot_a->buf + (fragment->y - snapshot_a->y) * snapshot_a->pitch + (fragment->x - snapshot_a->x);
		b = snapshot_b->buf + (fragment->y - snapshot_b->y) * snapshot_b->pitch + (fragment->x - snapshot_b->x);

		/* for the tweens, we already have snapshots sitting in ctxt->snapshots[],
		 * which we now interpolate the pixels out of in parallel
		 */
		for (unsigned y = 0, h = fragment->height, w = fragment->width; y < h; y++) {
			unsigned x = 0;

			/* go four-wide if there's enough, note even without SSE this is a bit quicker a la unrolled loop */
			if ((w & ~3U)) {
				for (; x < (w & ~3U); x += 4) {
					/* TODO: explore adding a SIMD/SSE implementation, this is an ideal application for it */
					*dest = pixels_lerp(*a, *b, one_sub_T, T);
					dest++;
					a++;
					b++;

					*dest = pixels_lerp(*a, *b, one_sub_T, T);
					dest++;
					a++;
					b++;

					*dest = pixels_lerp(*a, *b, one_sub_T, T);
					dest++;
					a++;
					b++;

					*dest = pixels_lerp(*a, *b, one_sub_T, T);
					dest++;
					a++;
					b++;
				}
			}

			/* pick up any tail pixels */
			for (; x < w; a++, b++, dest++, x++)
				*dest = pixels_lerp(*a, *b, one_sub_T, T);

			a += snapshot_a->pitch - w; /* things are a little awkward because we're fragmenting a threaded render within what was snapshotted */
			b += snapshot_b->pitch - w;
			dest += fragment->stride;
		}

		break;
	}

	default:
		assert(0);
	}

	*fragment_ptr = fragment;
}


static void mixer_finish_frame(til_module_context_t *context, til_stream_t *stream, unsigned int ticks, til_fb_fragment_t **fragment_ptr)
{
	mixer_context_t	*ctxt = (mixer_context_t *)context;

	for (int i = 0; i < 2; i++) {
		if (!ctxt->snapshots[i])
			continue;

		ctxt->snapshots[i] = til_fb_fragment_reclaim(ctxt->snapshots[i]);
	}
}


static void mixer_setup_free(til_setup_t *setup)
{
	mixer_setup_t	*s = (mixer_setup_t *)setup;

	if (s) {
		for (size_t i = 0; i < nelems(s->inputs); i++) {
			free(s->inputs[i].module);
			til_setup_free(s->inputs[i].setup);
		}
		free(setup);
	}
}


static int mixer_setup(const til_settings_t *settings, til_setting_t **res_setting, const til_setting_desc_t **res_desc, til_setup_t **res_setup)
{
	const char		*style_values[] = {
					"fade",
					"flicker",
					NULL
				};
	const char		*style;
	const til_settings_t	*inputs_settings[2];
	til_setting_t		*inputs_module_setting[2];
	const char		*inputs[2];
	int			r;

	r = til_settings_get_and_describe_value(settings,
						&(til_setting_spec_t){
							.name = "Mixer blend style",
							.key = "style",
							.values = style_values,
							.preferred = style_values[MIXER_DEFAULT_STYLE],
							.annotations = NULL
						},
						&style,
						res_setting,
						res_desc);
	if (r)
		return r;

	{
		const char *input_names[2] = { "First module to mix", "Second module to mix" };
		const char *input_keys[2] = { "a_module", "b_module" };
		const char *input_module_name_names[2] = { "First module's name", "Second module's name" };
		const char *input_preferred[2] = { "blank", "compose" };

		for (int i = 0; i < 2; i++) {
			const til_module_t	*mod;

			r = til_settings_get_and_describe_value(settings,
								&(til_setting_spec_t){
									.name = input_names[i],
									.key = input_keys[i],
									.preferred = input_preferred[i],
									.as_nested_settings = 1,
								},
								&inputs[i],
								res_setting,
								res_desc);
			if (r)
				return r;

			assert(res_setting && *res_setting);
			assert((*res_setting)->value_as_nested_settings);

			inputs_settings[i] = (*res_setting)->value_as_nested_settings;
			inputs[i] = til_settings_get_value_by_idx(inputs_settings[i], 0, &inputs_module_setting[i]);
			if (!inputs[i] || !inputs_module_setting[i]->desc) {
				r = til_setting_desc_new(inputs_settings[i],
							&(til_setting_spec_t){
								.name = input_module_name_names[i],
								.preferred = input_preferred[i],
								.as_label = 1,
							},
							res_desc);
				if (r < 0)
					return r;

				*res_setting = inputs[i] ? inputs_module_setting[i] : NULL;

				return 1;
			}

			mod = til_lookup_module(inputs[i]);
			if (!mod) {
				*res_setting = inputs_module_setting[i];

				return -EINVAL;
			}

			if (mod->setup) {
				r = mod->setup(inputs_settings[i], res_setting, res_desc, NULL);
				if (r)
					return r;
			}
		}
	}

	if (res_setup) {
		mixer_setup_t	*setup;

		setup = til_setup_new(settings, sizeof(*setup), mixer_setup_free);
		if (!setup)
			return -ENOMEM;

		/* TODO move checkers_value_to_pos() to libtil and use it here */
		for (int i = 0; style_values[i]; i++) {
			if (!strcasecmp(style_values[i], style))
				setup->style = i;
		}

		for (int i = 0; i < 2; i++) {
			const til_module_t	*input_module;

			setup->inputs[i].module = strdup(inputs[i]);
			if (!setup->inputs[i].module) { /* FIXME: why don't we just stow the til_module_t* */
				til_setup_free(&setup->til_setup);

				return -ENOMEM;
			}

			input_module = til_lookup_module(inputs[i]);
			if (!input_module) {
				til_setup_free(&setup->til_setup);

				return -EINVAL;
			}

			r = til_module_setup_finalize(input_module, inputs_settings[i], &setup->inputs[i].setup);
			if (r < 0) {
				til_setup_free(&setup->til_setup);

				return r;
			}
		}

		*res_setup = &setup->til_setup;
	}

	return 0;
}


til_module_t	mixer_module = {
	.create_context = mixer_create_context,
	.destroy_context = mixer_destroy_context,
	.prepare_frame = mixer_prepare_frame,
	.render_fragment = mixer_render_fragment,
	.finish_frame = mixer_finish_frame,
	.name = "mixer",
	.description = "Module blender",
	.setup = mixer_setup,
	.flags = TIL_MODULE_EXPERIMENTAL,
};