/*
 * Copyright (c) 2012 Neratec Solutions AG
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <linux/slab.h>
#include <linux/spinlock.h>

#include "ath.h"
#include "dfs_pattern_detector.h"
#include "dfs_pri_detector.h"

struct ath_dfs_pool_stats global_dfs_pool_stats = {};

#define DFS_POOL_STAT_INC(c) (global_dfs_pool_stats.c++)
#define DFS_POOL_STAT_DEC(c) (global_dfs_pool_stats.c--)
#define GET_PRI_TO_USE(MIN, MAX, RUNTIME) \
    (MIN + PRI_TOLERANCE == MAX - PRI_TOLERANCE ? MIN + PRI_TOLERANCE : RUNTIME)

/**
 * struct pulse_elem - elements in pulse queue
 * @ts: time stamp in usecs
 */
struct pulse_elem {
    struct list_head head;
    uint64_t ts;
};

/**
 * pde_get_multiple() - get number of multiples considering a given tolerance
 * @return factor if abs(val - factor*fraction) <= tolerance, 0 otherwise
 */
static uint32_t pde_get_multiple(uint32_t val, uint32_t fraction, uint32_t tolerance) {
    uint32_t remainder;
    uint32_t factor;
    uint32_t delta;

    if (fraction == 0) { return 0; }

    delta = (val < fraction) ? (fraction - val) : (val - fraction);

    if (delta <= tolerance)
    /* val and fraction are within tolerance */
    {
        return 1;
    }

    factor = val / fraction;
    remainder = val % fraction;
    if (remainder > tolerance) {
        /* no exact match */
        if ((fraction - remainder) <= tolerance)
        /* remainder is within tolerance */
        {
            factor++;
        } else {
            factor = 0;
        }
    }
    return factor;
}

/**
 * DOC: Singleton Pulse and Sequence Pools
 *
 * Instances of pri_sequence and pulse_elem are kept in singleton pools to
 * reduce the number of dynamic allocations. They are shared between all
 * instances and grow up to the peak number of simultaneously used objects.
 *
 * Memory is freed after all references to the pools are released.
 */
static uint32_t singleton_pool_references;
static LIST_HEAD(pulse_pool);
static LIST_HEAD(pseq_pool);
static DEFINE_SPINLOCK(pool_lock);

static void pool_register_ref(void) {
    spin_lock_bh(&pool_lock);
    singleton_pool_references++;
    DFS_POOL_STAT_INC(pool_reference);
    spin_unlock_bh(&pool_lock);
}

static void pool_deregister_ref(void) {
    spin_lock_bh(&pool_lock);
    singleton_pool_references--;
    DFS_POOL_STAT_DEC(pool_reference);
    if (singleton_pool_references == 0) {
        /* free singleton pools with no references left */
        struct pri_sequence *ps, *ps0;
        struct pulse_elem *p, *p0;

        list_for_each_entry_safe(p, p0, &pulse_pool, head) {
            list_del(&p->head);
            DFS_POOL_STAT_DEC(pulse_allocated);
            kfree(p);
        }
        list_for_each_entry_safe(ps, ps0, &pseq_pool, head) {
            list_del(&ps->head);
            DFS_POOL_STAT_DEC(pseq_allocated);
            kfree(ps);
        }
    }
    spin_unlock_bh(&pool_lock);
}

static void pool_put_pulse_elem(struct pulse_elem* pe) {
    spin_lock_bh(&pool_lock);
    list_add(&pe->head, &pulse_pool);
    DFS_POOL_STAT_DEC(pulse_used);
    spin_unlock_bh(&pool_lock);
}

static void pool_put_pseq_elem(struct pri_sequence* pse) {
    spin_lock_bh(&pool_lock);
    list_add(&pse->head, &pseq_pool);
    DFS_POOL_STAT_DEC(pseq_used);
    spin_unlock_bh(&pool_lock);
}

static struct pri_sequence* pool_get_pseq_elem(void) {
    struct pri_sequence* pse = NULL;
    spin_lock_bh(&pool_lock);
    if (!list_empty(&pseq_pool)) {
        pse = list_first_entry(&pseq_pool, struct pri_sequence, head);
        list_del(&pse->head);
        DFS_POOL_STAT_INC(pseq_used);
    }
    spin_unlock_bh(&pool_lock);
    return pse;
}

static struct pulse_elem* pool_get_pulse_elem(void) {
    struct pulse_elem* pe = NULL;
    spin_lock_bh(&pool_lock);
    if (!list_empty(&pulse_pool)) {
        pe = list_first_entry(&pulse_pool, struct pulse_elem, head);
        list_del(&pe->head);
        DFS_POOL_STAT_INC(pulse_used);
    }
    spin_unlock_bh(&pool_lock);
    return pe;
}

static struct pulse_elem* pulse_queue_get_tail(struct pri_detector* pde) {
    struct list_head* l = &pde->pulses;
    if (list_empty(l)) { return NULL; }
    return list_entry(l->prev, struct pulse_elem, head);
}

static bool pulse_queue_dequeue(struct pri_detector* pde) {
    struct pulse_elem* p = pulse_queue_get_tail(pde);
    if (p != NULL) {
        list_del_init(&p->head);
        pde->count--;
        /* give it back to pool */
        pool_put_pulse_elem(p);
    }
    return (pde->count > 0);
}

/* remove pulses older than window */
static void pulse_queue_check_window(struct pri_detector* pde) {
    uint64_t min_valid_ts;
    struct pulse_elem* p;

    /* there is no delta time with less than 2 pulses */
    if (pde->count < 2) { return; }

    if (pde->last_ts <= pde->window_size) { return; }

    min_valid_ts = pde->last_ts - pde->window_size;
    while ((p = pulse_queue_get_tail(pde)) != NULL) {
        if (p->ts >= min_valid_ts) { return; }
        pulse_queue_dequeue(pde);
    }
}

static bool pulse_queue_enqueue(struct pri_detector* pde, uint64_t ts) {
    struct pulse_elem* p = pool_get_pulse_elem();
    if (p == NULL) {
        p = kmalloc(sizeof(*p), GFP_ATOMIC);
        if (p == NULL) {
            DFS_POOL_STAT_INC(pulse_alloc_error);
            return false;
        }
        DFS_POOL_STAT_INC(pulse_allocated);
        DFS_POOL_STAT_INC(pulse_used);
    }
    INIT_LIST_HEAD(&p->head);
    p->ts = ts;
    list_add(&p->head, &pde->pulses);
    pde->count++;
    pde->last_ts = ts;
    pulse_queue_check_window(pde);
    if (pde->count >= pde->max_count) { pulse_queue_dequeue(pde); }
    return true;
}

static bool pseq_handler_create_sequences(struct pri_detector* pde, uint64_t ts,
                                          uint32_t min_count) {
    struct pulse_elem* p;
    list_for_each_entry(p, &pde->pulses, head) {
        struct pri_sequence ps, *new_ps;
        struct pulse_elem* p2;
        uint32_t tmp_false_count;
        uint64_t min_valid_ts;
        uint32_t delta_ts = ts - p->ts;

        if (delta_ts < pde->rs->pri_min)
        /* ignore too small pri */
        {
            continue;
        }

        if (delta_ts > pde->rs->pri_max)
        /* stop on too large pri (sorted list) */
        {
            break;
        }

        /* build a new sequence with new potential pri */
        ps.count = 2;
        ps.count_falses = 0;
        ps.first_ts = p->ts;
        ps.last_ts = ts;
        ps.pri = GET_PRI_TO_USE(pde->rs->pri_min, pde->rs->pri_max, ts - p->ts);
        ps.dur = ps.pri * (pde->rs->ppb - 1) + 2 * pde->rs->max_pri_tolerance;

        p2 = p;
        tmp_false_count = 0;
        min_valid_ts = ts - ps.dur;
        /* check which past pulses are candidates for new sequence */
        list_for_each_entry_continue(p2, &pde->pulses, head) {
            uint32_t factor;
            if (p2->ts < min_valid_ts)
            /* stop on crossing window border */
            {
                break;
            }
            /* check if pulse match (multi)PRI */
            factor = pde_get_multiple(ps.last_ts - p2->ts, ps.pri, pde->rs->max_pri_tolerance);
            if (factor > 0) {
                ps.count++;
                ps.first_ts = p2->ts;
                /*
                 * on match, add the intermediate falses
                 * and reset counter
                 */
                ps.count_falses += tmp_false_count;
                tmp_false_count = 0;
            } else {
                /* this is a potential false one */
                tmp_false_count++;
            }
        }
        if (ps.count <= min_count)
        /* did not reach minimum count, drop sequence */
        {
            continue;
        }

        /* this is a valid one, add it */
        ps.deadline_ts = ps.first_ts + ps.dur;
        new_ps = pool_get_pseq_elem();
        if (new_ps == NULL) {
            new_ps = kmalloc(sizeof(*new_ps), GFP_ATOMIC);
            if (new_ps == NULL) {
                DFS_POOL_STAT_INC(pseq_alloc_error);
                return false;
            }
            DFS_POOL_STAT_INC(pseq_allocated);
            DFS_POOL_STAT_INC(pseq_used);
        }
        memcpy(new_ps, &ps, sizeof(ps));
        INIT_LIST_HEAD(&new_ps->head);
        list_add(&new_ps->head, &pde->sequences);
    }
    return true;
}

/* check new ts and add to all matching existing sequences */
static uint32_t pseq_handler_add_to_existing_seqs(struct pri_detector* pde, uint64_t ts) {
    uint32_t max_count = 0;
    struct pri_sequence *ps, *ps2;
    list_for_each_entry_safe(ps, ps2, &pde->sequences, head) {
        uint32_t delta_ts;
        uint32_t factor;

        /* first ensure that sequence is within window */
        if (ts > ps->deadline_ts) {
            list_del_init(&ps->head);
            pool_put_pseq_elem(ps);
            continue;
        }

        delta_ts = ts - ps->last_ts;
        factor = pde_get_multiple(delta_ts, ps->pri, pde->rs->max_pri_tolerance);
        if (factor > 0) {
            ps->last_ts = ts;
            ps->count++;

            if (max_count < ps->count) { max_count = ps->count; }
        } else {
            ps->count_falses++;
        }
    }
    return max_count;
}

static struct pri_sequence* pseq_handler_check_detection(struct pri_detector* pde) {
    struct pri_sequence* ps;

    if (list_empty(&pde->sequences)) { return NULL; }

    list_for_each_entry(ps, &pde->sequences, head) {
        /*
         * we assume to have enough matching confidence if we
         * 1) have enough pulses
         * 2) have more matching than false pulses
         */
        if ((ps->count >= pde->rs->ppb_thresh) &&
            (ps->count * pde->rs->num_pri >= ps->count_falses)) {
            return ps;
        }
    }
    return NULL;
}

/* free pulse queue and sequences list and give objects back to pools */
static void pri_detector_reset(struct pri_detector* pde, uint64_t ts) {
    struct pri_sequence *ps, *ps0;
    struct pulse_elem *p, *p0;
    list_for_each_entry_safe(ps, ps0, &pde->sequences, head) {
        list_del_init(&ps->head);
        pool_put_pseq_elem(ps);
    }
    list_for_each_entry_safe(p, p0, &pde->pulses, head) {
        list_del_init(&p->head);
        pool_put_pulse_elem(p);
    }
    pde->count = 0;
    pde->last_ts = ts;
}

static void pri_detector_exit(struct pri_detector* de) {
    pri_detector_reset(de, 0);
    pool_deregister_ref();
    kfree(de);
}

static struct pri_sequence* pri_detector_add_pulse(struct pri_detector* de,
                                                   struct pulse_event* event) {
    uint32_t max_updated_seq;
    struct pri_sequence* ps;
    uint64_t ts = event->ts;
    const struct radar_detector_specs* rs = de->rs;

    /* ignore pulses not within width range */
    if ((rs->width_min > event->width) || (rs->width_max < event->width)) { return NULL; }

    if ((ts - de->last_ts) < rs->max_pri_tolerance)
    /* if delta to last pulse is too short, don't use this pulse */
    {
        return NULL;
    }
    /* radar detector spec needs chirp, but not detected */
    if (rs->chirp && rs->chirp != event->chirp) { return NULL; }

    de->last_ts = ts;

    max_updated_seq = pseq_handler_add_to_existing_seqs(de, ts);

    if (!pseq_handler_create_sequences(de, ts, max_updated_seq)) {
        pri_detector_reset(de, ts);
        return NULL;
    }

    ps = pseq_handler_check_detection(de);

    if (ps == NULL) { pulse_queue_enqueue(de, ts); }

    return ps;
}

struct pri_detector* pri_detector_init(const struct radar_detector_specs* rs) {
    struct pri_detector* de;

    de = kzalloc(sizeof(*de), GFP_ATOMIC);
    if (de == NULL) { return NULL; }
    de->exit = pri_detector_exit;
    de->add_pulse = pri_detector_add_pulse;
    de->reset = pri_detector_reset;

    INIT_LIST_HEAD(&de->sequences);
    INIT_LIST_HEAD(&de->pulses);
    de->window_size = rs->pri_max * rs->ppb * rs->num_pri;
    de->max_count = rs->ppb * 2;
    de->rs = rs;

    pool_register_ref();
    return de;
}