// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *   ALSA sequencer Priority Queue
 *   Copyright (c) 1998-1999 by Frank van de Pol <fvdpol@coil.demon.nl>
 */

#include <linux/time.h>
#include <linux/slab.h>
#include <sound/core.h>
#include "seq_timer.h"
#include "seq_prioq.h"


/* Implementation is a simple linked list for now...

   This priority queue orders the events on timestamp. For events with an
   equeal timestamp the queue behaves as a FIFO. 

   *
   *           +-------+
   *  Head --> | first |
   *           +-------+
   *                 |next
   *           +-----v-+
   *           |       |
   *           +-------+
   *                 |
   *           +-----v-+
   *           |       |
   *           +-------+
   *                 |
   *           +-----v-+
   *  Tail --> | last  |
   *           +-------+
   *

 */



/* create new prioq (constructor) */
struct snd_seq_prioq *snd_seq_prioq_new(void)
{
        struct snd_seq_prioq *f;

        f = kzalloc_obj(*f);
        if (!f)
                return NULL;
        
        spin_lock_init(&f->lock);
        f->head = NULL;
        f->tail = NULL;
        f->cells = 0;
        
        return f;
}

/* delete prioq (destructor) */
void snd_seq_prioq_delete(struct snd_seq_prioq **fifo)
{
        struct snd_seq_prioq *f = *fifo;
        *fifo = NULL;

        if (f == NULL) {
                pr_debug("ALSA: seq: snd_seq_prioq_delete() called with NULL prioq\n");
                return;
        }

        /* release resources...*/
        /*....................*/
        
        if (f->cells > 0) {
                /* drain prioQ */
                while (f->cells > 0)
                        snd_seq_cell_free(snd_seq_prioq_cell_out(f, NULL));
        }
        
        kfree(f);
}




/* compare timestamp between events */
/* return 1 if a >= b; 0 */
static inline int compare_timestamp(struct snd_seq_event *a,
                                    struct snd_seq_event *b)
{
        if ((a->flags & SNDRV_SEQ_TIME_STAMP_MASK) == SNDRV_SEQ_TIME_STAMP_TICK) {
                /* compare ticks */
                return (snd_seq_compare_tick_time(&a->time.tick, &b->time.tick));
        } else {
                /* compare real time */
                return (snd_seq_compare_real_time(&a->time.time, &b->time.time));
        }
}

/* compare timestamp between events */
/* return negative if a < b;
 *        zero     if a = b;
 *        positive if a > b;
 */
static inline int compare_timestamp_rel(struct snd_seq_event *a,
                                        struct snd_seq_event *b)
{
        if ((a->flags & SNDRV_SEQ_TIME_STAMP_MASK) == SNDRV_SEQ_TIME_STAMP_TICK) {
                /* compare ticks */
                if (a->time.tick > b->time.tick)
                        return 1;
                else if (a->time.tick == b->time.tick)
                        return 0;
                else
                        return -1;
        } else {
                /* compare real time */
                if (a->time.time.tv_sec > b->time.time.tv_sec)
                        return 1;
                else if (a->time.time.tv_sec == b->time.time.tv_sec) {
                        if (a->time.time.tv_nsec > b->time.time.tv_nsec)
                                return 1;
                        else if (a->time.time.tv_nsec == b->time.time.tv_nsec)
                                return 0;
                        else
                                return -1;
                } else
                        return -1;
        }
}

/* enqueue cell to prioq */
int snd_seq_prioq_cell_in(struct snd_seq_prioq * f,
                          struct snd_seq_event_cell * cell)
{
        struct snd_seq_event_cell *cur, *prev;
        int remaining;
        int prior;

        if (snd_BUG_ON(!f || !cell))
                return -EINVAL;
        
        /* check flags */
        prior = (cell->event.flags & SNDRV_SEQ_PRIORITY_MASK);

        guard(spinlock_irqsave)(&f->lock);

        /* check if this element needs to inserted at the end (ie. ordered 
           data is inserted) This will be very likeley if a sequencer 
           application or midi file player is feeding us (sequential) data */
        if (f->tail && !prior) {
                if (compare_timestamp(&cell->event, &f->tail->event)) {
                        /* add new cell to tail of the fifo */
                        f->tail->next = cell;
                        f->tail = cell;
                        cell->next = NULL;
                        f->cells++;
                        return 0;
                }
        }
        /* traverse list of elements to find the place where the new cell is
           to be inserted... Note that this is a order n process ! */

        prev = NULL;            /* previous cell */
        cur = f->head;          /* cursor */

        remaining = f->cells;
        while (cur != NULL) {
                /* compare timestamps */
                int rel = compare_timestamp_rel(&cell->event, &cur->event);

                if (remaining-- <= 0) {
                        pr_err("ALSA: seq: inconsistent prioq cell count\n");
                        return -EINVAL;
                }

                if (rel < 0)
                        /* new cell has earlier schedule time, */
                        break;
                else if (rel == 0 && prior)
                        /* equal schedule time and prior to others */
                        break;
                /* new cell has equal or larger schedule time, */
                /* move cursor to next cell */
                prev = cur;
                cur = cur->next;
        }

        /* insert it before cursor */
        if (prev != NULL)
                prev->next = cell;
        cell->next = cur;

        if (f->head == cur) /* this is the first cell, set head to it */
                f->head = cell;
        if (cur == NULL) /* reached end of the list */
                f->tail = cell;
        f->cells++;
        return 0;
}

/* return 1 if the current time >= event timestamp */
static int event_is_ready(struct snd_seq_event *ev, void *current_time)
{
        if ((ev->flags & SNDRV_SEQ_TIME_STAMP_MASK) == SNDRV_SEQ_TIME_STAMP_TICK)
                return snd_seq_compare_tick_time(current_time, &ev->time.tick);
        else
                return snd_seq_compare_real_time(current_time, &ev->time.time);
}

/* dequeue cell from prioq */
struct snd_seq_event_cell *snd_seq_prioq_cell_out(struct snd_seq_prioq *f,
                                                  void *current_time)
{
        struct snd_seq_event_cell *cell;

        if (f == NULL) {
                pr_debug("ALSA: seq: snd_seq_prioq_cell_in() called with NULL prioq\n");
                return NULL;
        }

        guard(spinlock_irqsave)(&f->lock);
        cell = f->head;
        if (cell && current_time && !event_is_ready(&cell->event, current_time))
                cell = NULL;
        if (cell) {
                f->head = cell->next;

                /* reset tail if this was the last element */
                if (f->tail == cell)
                        f->tail = NULL;

                cell->next = NULL;
                f->cells--;
        }

        return cell;
}

/* return number of events available in prioq */
int snd_seq_prioq_avail(struct snd_seq_prioq * f)
{
        if (f == NULL) {
                pr_debug("ALSA: seq: snd_seq_prioq_cell_in() called with NULL prioq\n");
                return 0;
        }
        return f->cells;
}

/* remove cells matching with the condition */
static void prioq_remove_cells(struct snd_seq_prioq *f,
                               bool (*match)(struct snd_seq_event_cell *cell,
                                             void *arg),
                               void *arg)
{
        register struct snd_seq_event_cell *cell, *next;
        struct snd_seq_event_cell *prev = NULL;
        struct snd_seq_event_cell *freefirst = NULL, *freeprev = NULL, *freenext;

        /* collect all removed cells */
        scoped_guard(spinlock_irqsave, &f->lock) {
                for (cell = f->head; cell; cell = next) {
                        next = cell->next;
                        if (!match(cell, arg)) {
                                prev = cell;
                                continue;
                        }

                        /* remove cell from prioq */
                        if (cell == f->head)
                                f->head = cell->next;
                        else
                                prev->next = cell->next;
                        if (cell == f->tail)
                                f->tail = cell->next;
                        f->cells--;

                        /* add cell to free list */
                        cell->next = NULL;
                        if (freefirst == NULL)
                                freefirst = cell;
                        else
                                freeprev->next = cell;
                        freeprev = cell;
                }
        }

        /* remove selected cells */
        while (freefirst) {
                freenext = freefirst->next;
                snd_seq_cell_free(freefirst);
                freefirst = freenext;
        }
}

struct prioq_match_arg {
        int client;
        int timestamp;
};

static inline bool prioq_match(struct snd_seq_event_cell *cell, void *arg)
{
        struct prioq_match_arg *v = arg;

        if (cell->event.source.client == v->client ||
            cell->event.dest.client == v->client)
                return true;
        if (!v->timestamp)
                return false;
        switch (cell->event.flags & SNDRV_SEQ_TIME_STAMP_MASK) {
        case SNDRV_SEQ_TIME_STAMP_TICK:
                if (cell->event.time.tick)
                        return true;
                break;
        case SNDRV_SEQ_TIME_STAMP_REAL:
                if (cell->event.time.time.tv_sec ||
                    cell->event.time.time.tv_nsec)
                        return true;
                break;
        }
        return false;
}

/* remove cells for left client */
void snd_seq_prioq_leave(struct snd_seq_prioq *f, int client, int timestamp)
{
        struct prioq_match_arg arg = { client, timestamp };

        return prioq_remove_cells(f, prioq_match, &arg);
}

struct prioq_remove_match_arg {
        int client;
        struct snd_seq_remove_events *info;
};

static bool prioq_remove_match(struct snd_seq_event_cell *cell, void *arg)
{
        struct prioq_remove_match_arg *v = arg;
        struct snd_seq_event *ev = &cell->event;
        struct snd_seq_remove_events *info = v->info;
        int res;

        if (ev->source.client != v->client)
                return false;

        if (info->remove_mode & SNDRV_SEQ_REMOVE_DEST) {
                if (ev->dest.client != info->dest.client ||
                                ev->dest.port != info->dest.port)
                        return false;
        }
        if (info->remove_mode & SNDRV_SEQ_REMOVE_DEST_CHANNEL) {
                if (! snd_seq_ev_is_channel_type(ev))
                        return false;
                /* data.note.channel and data.control.channel are identical */
                if (ev->data.note.channel != info->channel)
                        return false;
        }
        if (info->remove_mode & SNDRV_SEQ_REMOVE_TIME_AFTER) {
                if (info->remove_mode & SNDRV_SEQ_REMOVE_TIME_TICK)
                        res = snd_seq_compare_tick_time(&ev->time.tick, &info->time.tick);
                else
                        res = snd_seq_compare_real_time(&ev->time.time, &info->time.time);
                if (!res)
                        return false;
        }
        if (info->remove_mode & SNDRV_SEQ_REMOVE_TIME_BEFORE) {
                if (info->remove_mode & SNDRV_SEQ_REMOVE_TIME_TICK)
                        res = snd_seq_compare_tick_time(&ev->time.tick, &info->time.tick);
                else
                        res = snd_seq_compare_real_time(&ev->time.time, &info->time.time);
                if (res)
                        return false;
        }
        if (info->remove_mode & SNDRV_SEQ_REMOVE_EVENT_TYPE) {
                if (ev->type != info->type)
                        return false;
        }
        if (info->remove_mode & SNDRV_SEQ_REMOVE_IGNORE_OFF) {
                /* Do not remove off events */
                switch (ev->type) {
                case SNDRV_SEQ_EVENT_NOTEOFF:
                /* case SNDRV_SEQ_EVENT_SAMPLE_STOP: */
                        return false;
                default:
                        break;
                }
        }
        if (info->remove_mode & SNDRV_SEQ_REMOVE_TAG_MATCH) {
                if (info->tag != ev->tag)
                        return false;
        }

        return true;
}

/* remove cells matching remove criteria */
void snd_seq_prioq_remove_events(struct snd_seq_prioq * f, int client,
                                 struct snd_seq_remove_events *info)
{
        struct prioq_remove_match_arg arg = { client, info };

        return prioq_remove_cells(f, prioq_remove_match, &arg);
}