/*
 *  Copyright (C) 2023 - Vito Caputo - <vcaputo@pengaru.com>
 *
 *  This program is free software: you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 2 as published
 *  by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

#include "til_stream.h"
#include "til_tap.h"

/* A stream in libtil is basically a hash table for tracking dynamic
 * information for modules to create/modify/access.  The objects stored in the
 * table are "stream pipes" and endpoints called taps, making this something
 * like a miniature in-memory implementation of named pipes, conceptually
 * anyways (there are no actual file descriptors).
 */

#if 0
/* example usage: */
typedef struct foo_t {
	struct {
		til_tap_t	position;
	} taps;
	struct {
		v2f_t		position;
	} vars;

	v2f_t	*position;
} foo_t;

foo_t * foo_create_context(void)
{
	foo_t	*foo = malloc(sizeof(foo_t));

	/* This creates an isolated (pipe-)tap binding our local position variable and pointer
	 * to a name for later "tapping" onto a stream.
	 */
	foo->taps.position = til_tap_init_v2f(&foo->position, 1, &foo->vars.position, "position");
}

foo_render(foo_t *foo, til_fb_fragment_t *fragment)
{
	if (!til_stream_tap_context(fragment->stream, foo, &foo->taps.position)) {
		/* got nothing, we're driving position */
		foo->position->x = cosf(ticks);
		foo->position->y = sinf(ticks);
	} /* else { got something, just use foo->position as-is */
}
#endif


#define TIL_STREAM_BUCKETS_COUNT	256

typedef struct til_stream_pipe_t til_stream_pipe_t;

struct til_stream_pipe_t {
	til_stream_pipe_t	*next;
	const void		*owner;		/* for untap_owner() differentiation */
	const void		*owner_foo;	/* supplemental pointer for owner's use */
	char			*parent_path;
	const til_tap_t		*driving_tap;	/* tap producing values for the pipe */
	uint32_t		hash;		/* hash of (driving_tap->name_hash ^ .parent_hash) */
};

typedef struct til_stream_t {
	pthread_mutex_t		mutex;
	til_stream_pipe_t	*buckets[TIL_STREAM_BUCKETS_COUNT];
} til_stream_t;


til_stream_t * til_stream_new(void)
{
	til_stream_t	*stream;

	stream = calloc(1, sizeof(til_stream_t));
	if (!stream)
		return NULL;

	pthread_mutex_init(&stream->mutex, NULL);

	return stream;
}


til_stream_t * til_stream_free(til_stream_t *stream)
{
	if (!stream)
		return NULL;

	for (int i = 0; i < TIL_STREAM_BUCKETS_COUNT; i++) {
		for (til_stream_pipe_t *p = stream->buckets[i], *p_next; p != NULL; p = p_next) {
			p_next = p->next;
			free(p->parent_path);
			free(p);
		}
	}

	pthread_mutex_destroy(&stream->mutex);
	free(stream);

	return NULL;
}


/* Taps the key-named type-typed pipe on the supplied stream.
 * If this is the first use of the pipe on this stream, new pipe will be created.
 * If the pipe exists on this stream, and the type/n_elems match, existing pipe will be used as-is.
 * If the pipe exists on this stream, but the type/n_elems mismatch, it's a program error and asserted
 *
 * -errno is returned on error, 0 when tap is driving, 1 when tap is passenger.
 *
 * If stream is NULL it's treated as if the key doesn't exist without a pipe creation.
 */
int til_stream_tap(til_stream_t *stream, const void *owner, const void *owner_foo, const char *parent_path, uint32_t parent_hash, const til_tap_t *tap)
{
	uint32_t		hash, bucket;
	til_stream_pipe_t	*pipe;

	assert(tap);

	if (!stream) {
		*(tap->ptr) = tap->elems;

		return 0;
	}

	pthread_mutex_lock(&stream->mutex);

	hash = (tap->name_hash ^ parent_hash);
	bucket = hash % TIL_STREAM_BUCKETS_COUNT;
	for (pipe = stream->buckets[bucket]; pipe != NULL; pipe = pipe->next) {
		if (pipe->hash == hash) {
			if (pipe->driving_tap == tap) {
				/* this is the pipe and we're driving */
				*(tap->ptr) = pipe->driving_tap->elems;

				pthread_mutex_unlock(&stream->mutex);
				return 0;
			}

			if (pipe->driving_tap->elems == *(tap->ptr) ||
			    (!strcmp(pipe->driving_tap->name, tap->name) && !strcmp(pipe->parent_path, parent_path))) {
				if (pipe->driving_tap->type != tap->type ||
				    pipe->driving_tap->n_elems != tap->n_elems) {
					assert(0); /* I don't really want to handle such errors at runtime */
					return -1;
				}

				/* this looks to be the pipe, but we're not driving, should we be? */
				if (pipe->driving_tap->inactive)
					pipe->driving_tap = tap;

				*(tap->ptr) = pipe->driving_tap->elems;

				pthread_mutex_unlock(&stream->mutex);
				return (tap != pipe->driving_tap);
			}
		}
	}

	/* matching pipe not found, create new one with tap as driver */
	pipe = calloc(1, sizeof(til_stream_pipe_t));
	if (!pipe) {
		pthread_mutex_unlock(&stream->mutex);
		return -ENOMEM;
	}

	pipe->owner = owner;
	pipe->owner_foo = owner_foo;
	pipe->driving_tap = tap;

	pipe->parent_path = strdup(parent_path);
	if (!pipe->parent_path) {
		free(pipe);

		pthread_mutex_unlock(&stream->mutex);
		return -ENOMEM;
	}

	pipe->hash = hash;
	pipe->next = stream->buckets[bucket];
	stream->buckets[bucket] = pipe;

	pthread_mutex_unlock(&stream->mutex);
	return 0;
}


/* remove all pipes belonging to owner in stream */
void til_stream_untap_owner(til_stream_t *stream, const void *owner)
{
	for (int i = 0; i < TIL_STREAM_BUCKETS_COUNT; i++) {
		for (til_stream_pipe_t *p = stream->buckets[i], *p_next, *p_prev; p != NULL; p = p_next) {
			p_next = p->next;

			if (p->owner == owner) {
				if (p == stream->buckets[i])
					stream->buckets[i] = p_next;
				else
					p_prev->next = p_next;

				free(p);
			} else
				p_prev = p;
		}
	}
}


/* We need the higher-order types defined in order to print their contents.
 * libtil should probably just formally define these smoewhere for modules to
 * make use of.  Until now it's been very deliberate to try leave modules to be
 * relatively self-contained, even if they often reinvent the wheel as a
 * result... it's relatively harmless for small functionalities while keeping
 * the listings easier to grok as a whole esp. for a newcomer who isn't
 * necessarily comfortable jumping around a sprawling tree of files.
 */
typedef struct v2f_t { float	x, y; } v2f_t;

typedef struct v3f_t {
	float	x, y, z;
} v3f_t;

typedef struct v4f_t {
	float	x, y, z, w;
} v4f_t;


static int til_stream_fprint_pipe_cb(void *arg, til_stream_pipe_t *pipe, const void *owner, const void *owner_foo, const til_tap_t *driving_tap)
{
	FILE	*out = arg;

	fprintf(out, "%s/%s: ", pipe->parent_path, pipe->driving_tap->name);

	for (size_t j = 0; j < pipe->driving_tap->n_elems; j++) {
		const char	*sep = j ? ", " : "";

		switch (pipe->driving_tap->type) {
		case TIL_TAP_TYPE_I8:
			fprintf(out, "%"PRIi8"%s",
				*(*((int8_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_I16:
			fprintf(out, "%"PRIi16"%s",
				*(*((int16_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_I32:
			fprintf(out, "%"PRIi32"%s",
				*(*((int32_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_I64:
			fprintf(out, "%"PRIi64"%s",
				*(*((int64_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_U8:
			fprintf(out, "%"PRIu8"%s",
				*(*((int8_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_U16:
			fprintf(out, "%"PRIu16"%s",
				*(*((int16_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_U32:
			fprintf(out, "%"PRIu32"%s",
				*(*((int32_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_U64:
			fprintf(out, "%"PRIu64"%s",
				*(*((int64_t **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_FLOAT:
			fprintf(out, "%f%s",
				*(*((float **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_DOUBLE:
			fprintf(out, "%f%s",
				*(*((double **)pipe->driving_tap->ptr)),
				sep);
			break;

		case TIL_TAP_TYPE_V2F:
			fprintf(out, "{%f,%f}%s",
				(*((v2f_t **)pipe->driving_tap->ptr))->x,
				(*((v2f_t **)pipe->driving_tap->ptr))->y,
				sep);
			break;

		case TIL_TAP_TYPE_V3F:
			fprintf(out, "{%f,%f,%f}%s",
				(*((v3f_t **)pipe->driving_tap->ptr))->x,
				(*((v3f_t **)pipe->driving_tap->ptr))->y,
				(*((v3f_t **)pipe->driving_tap->ptr))->z,
				sep);
			break;

		case TIL_TAP_TYPE_V4F:
			fprintf(out, "{%f,%f,%f,%f}%s",
				(*((v4f_t **)pipe->driving_tap->ptr))->x,
				(*((v4f_t **)pipe->driving_tap->ptr))->y,
				(*((v4f_t **)pipe->driving_tap->ptr))->z,
				(*((v4f_t **)pipe->driving_tap->ptr))->w,
				sep);
			break;

		case TIL_TAP_TYPE_M4F:
			fprintf(out, "M4F TODO%s", sep);
			break;

		case TIL_TAP_TYPE_VOIDP:
			fprintf(out, "%p%s", *((void **)pipe->driving_tap->ptr), sep);
			break;

		default:
			assert(0);
		}
		fprintf(out, "\n");
	}

	return 1;
}


/* XXX: note that while yes, this does acquire stream->mutex to serialize access to the table/pipes,
 * this mutex does not serialize access to the tapped variables.  So if this print is performed
 * during the threaded rendering phase of things, it will technically be racy.  The only strictly
 * correct place to perform this print race-free is in the rendering loop between submissions to
 * the rendering threads.  Arguably if careful about only printing while serial, there's no need
 * to acquire the mutex - but it's also an uncontended lock if that's the case so just take the
 * mutex anyways since we're accessing the underlying structure it protects.
 */
void til_stream_fprint(til_stream_t *stream, FILE *out)
{
	fprintf(out, "Pipes on stream %p:\n", stream);
	(void) til_stream_for_each_pipe(stream, til_stream_fprint_pipe_cb, out);
	fprintf(out, "\n");
}


/* returns -errno on error (from pipe_cb), 0 otherwise */
int til_stream_for_each_pipe(til_stream_t *stream, til_stream_iter_func_t pipe_cb, void *cb_context)
{
	assert(stream);
	assert(pipe_cb);

	pthread_mutex_lock(&stream->mutex);

	for (int i = 0; i < TIL_STREAM_BUCKETS_COUNT; i++) {
		for (til_stream_pipe_t *p = stream->buckets[i]; p != NULL; p = p->next) {
			int	r;

			r = pipe_cb(cb_context, p, p->owner, p->owner_foo, p->driving_tap);
			if (r < 0) {
				pthread_mutex_unlock(&stream->mutex);
				return r;
			}
		}
	}

	pthread_mutex_unlock(&stream->mutex);
	return 0;
}


void til_stream_pipe_set_owner(til_stream_pipe_t *pipe, const void *owner, const void *owner_foo)
{
	assert(pipe);

	pipe->owner = owner;
	pipe->owner_foo = owner_foo;
}


/* NULLing out the driving_tap isn't supported, since the tap name is part of the pipe's identity,
 * just set tap.inactive to indicate another tap should take over driving.
 */
void til_stream_pipe_set_driving_tap(til_stream_pipe_t *pipe, const til_tap_t *driving_tap)
{
	assert(pipe);
	assert(driving_tap);

	pipe->driving_tap = driving_tap;
}