/*
 * Copyright (c) 2019, Arm Limited and affiliates.
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * \file ns_monitor.c
 * \brief Utility functions for nanostack maintenance
 *
 * This module tracks stack current heap usage and triggers GC if heap usage is too high.
 * GC is triggered by:
 *  1. Heap usage is above HEAP_USAGE_HIGH
 *  2. Heap usage is above HEAP_USAGE_CRITICAL
 *  3. If nsdynmemLIB memory allocation has failed since last check
 */

#include "nsconfig.h"
#include "ns_types.h"
#define HAVE_DEBUG
#include "ns_trace.h"
#include "nsdynmemLIB.h"
#include "ipv6_stack/ipv6_routing_table.h"
#include "NWK_INTERFACE/Include/protocol.h"

#define TRACE_GROUP "mntr"

typedef enum {
    NS_MONITOR_STATE_HEAP_GC_IDLE = 0,
    NS_MONITOR_STATE_HEAP_GC_HIGH,
    NS_MONITOR_STATE_GC_CRITICAL
} ns_monitor_state_e;

#define HEAP_HIGH_WATERWARK     (0.95)   /* Heap usage HIGH threshold */
#define HEAP_CRITICAL_WATERMARK (0.99)   /* Heap usage CRITICAL threshold */

#define NS_MAINTENANCE_TIMER_INTERVAL   10  // Maintenance interval

typedef struct ns_monitor__s {
    ns_mem_heap_size_t heap_high_watermark;
    ns_mem_heap_size_t heap_critical_watermark;
    uint32_t prev_heap_alloc_fail_cnt;
    ns_monitor_state_e ns_monitor_heap_gc_state;
    const mem_stat_t *mem_stats;
    uint16_t ns_maintenance_timer;
} ns_monitor_t;

static ns_monitor_t *ns_monitor_ptr = NULL;

typedef void (ns_maintenance_gc_cb)(bool full_gc);

/*
 * Garbage collection functions.
 * Add more GC performing functions to the table
 *
 */
static ns_maintenance_gc_cb *ns_maintenance_gc_functions[] = {
    ipv6_destination_cache_forced_gc
};

static void ns_monitor_heap_gc(bool full_gc)
{
    (void) full_gc;

    for (unsigned int i = 0; i < sizeof(ns_maintenance_gc_functions) / sizeof(ns_maintenance_gc_functions[0]); i++) {
        if (ns_maintenance_gc_functions[i]) {
            (ns_maintenance_gc_functions[i])(full_gc);
        }
    }
}

static void ns_monitor_periodic_heap_health_check(void)
{
    if (ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes > ns_monitor_ptr->heap_critical_watermark) {
        // Heap usage above CRITICAL
        if (ns_monitor_ptr->ns_monitor_heap_gc_state != NS_MONITOR_STATE_GC_CRITICAL) {
            ns_mem_heap_size_t prev_heap_sector_allocated_bytes = ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes;
            tr_debug("heap %lu/%lu", (unsigned long)ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes, (unsigned long)ns_monitor_ptr->mem_stats->heap_sector_size);
            ns_monitor_heap_gc(true);
            ns_monitor_ptr->ns_monitor_heap_gc_state = NS_MONITOR_STATE_GC_CRITICAL;
            tr_info("Stack GC critical: freed %lu bytes", (unsigned long)(prev_heap_sector_allocated_bytes - ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes));
        }
    } else if (ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes > ns_monitor_ptr->heap_high_watermark) {
        // Heap usage above HIGH
        if (ns_monitor_ptr->ns_monitor_heap_gc_state == NS_MONITOR_STATE_HEAP_GC_IDLE) {
            ns_mem_heap_size_t prev_heap_sector_allocated_bytes = ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes;
            tr_debug("heap %lu/%lu", (unsigned long)ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes, (unsigned long)ns_monitor_ptr->mem_stats->heap_sector_size);
            ns_monitor_heap_gc(false);
            ns_monitor_ptr->ns_monitor_heap_gc_state = NS_MONITOR_STATE_HEAP_GC_HIGH;
            tr_info("Stack GC high: freed %lu bytes", (unsigned long)(prev_heap_sector_allocated_bytes - ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes));
        }
    } else if (ns_monitor_ptr->mem_stats->heap_sector_allocated_bytes <= ns_monitor_ptr->heap_high_watermark) {
        // Heap usage in normal range
        ns_monitor_ptr->ns_monitor_heap_gc_state = NS_MONITOR_STATE_HEAP_GC_IDLE;
    }
}

void ns_monitor_timer(uint16_t seconds)
{
    if (ns_monitor_ptr) {
        ns_monitor_ptr->ns_maintenance_timer += seconds;

        if (ns_monitor_ptr->mem_stats->heap_alloc_fail_cnt > ns_monitor_ptr->prev_heap_alloc_fail_cnt) {
            // Heap allocation failure occurred since last check
            ns_monitor_ptr->prev_heap_alloc_fail_cnt = ns_monitor_ptr->mem_stats->heap_alloc_fail_cnt;
            if (ns_monitor_ptr->ns_monitor_heap_gc_state != NS_MONITOR_STATE_GC_CRITICAL) {
                ns_monitor_ptr->ns_monitor_heap_gc_state = NS_MONITOR_STATE_GC_CRITICAL;
                ns_monitor_heap_gc(true);
                ns_monitor_ptr->ns_maintenance_timer = 0;
            }
        }

        if (ns_monitor_ptr->ns_maintenance_timer >= NS_MAINTENANCE_TIMER_INTERVAL) {
            ns_monitor_ptr->ns_maintenance_timer -= NS_MAINTENANCE_TIMER_INTERVAL;
            ns_monitor_periodic_heap_health_check();
        }
    }
}

int ns_monitor_init(void)
{
    if (ns_monitor_ptr || !ns_dyn_mem_get_mem_stat()) {
        // already initialized or memory statistics not available
        return -2;
    }

    ns_monitor_ptr = ns_dyn_mem_alloc(sizeof(ns_monitor_t));

    if (ns_monitor_ptr) {
        ns_monitor_ptr->mem_stats = ns_dyn_mem_get_mem_stat();
        ns_monitor_ptr->heap_high_watermark = ns_monitor_ptr->mem_stats->heap_sector_size * HEAP_HIGH_WATERWARK;
        ns_monitor_ptr->heap_critical_watermark = ns_monitor_ptr->mem_stats->heap_sector_size * HEAP_CRITICAL_WATERMARK;
        ns_monitor_ptr->ns_monitor_heap_gc_state = NS_MONITOR_STATE_HEAP_GC_IDLE;
        ns_monitor_ptr->ns_maintenance_timer = 0;
        ns_monitor_ptr->prev_heap_alloc_fail_cnt = 0;
        return 0;
    }

    return -1;
}

int ns_monitor_clear(void)
{
    if (ns_monitor_ptr) {
        ns_dyn_mem_free(ns_monitor_ptr);
        ns_monitor_ptr = NULL;
        return 0;
    }

    return -1;
}

int ns_monitor_heap_gc_threshold_set(uint8_t percentage_high, uint8_t percentage_critical)
{
    if (ns_monitor_ptr && (percentage_critical <= 100) && (percentage_high < percentage_critical)) {
        ns_monitor_ptr->heap_high_watermark = ns_monitor_ptr->mem_stats->heap_sector_size * percentage_high / 100;
        ns_monitor_ptr->heap_critical_watermark = ns_monitor_ptr->mem_stats->heap_sector_size * percentage_critical / 100;
        tr_debug("Monitor set high:%lu, critical:%lu total:%lu", (unsigned long)ns_monitor_ptr->heap_high_watermark, (unsigned long)ns_monitor_ptr->heap_critical_watermark, (unsigned long)ns_monitor_ptr->mem_stats->heap_sector_size);
        return 0;
    }

    return -1;
}