#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <inttypes.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_log.h"
#include "esp_err.h"
#include "esp_timer.h"
#include "nvs_flash.h"
#include "nvs.h"
#include "esp_event.h"
#include "esp_netif.h"
#include "esp_wifi.h"
#include "iperf.h"
#include "status_led.h"

static const char *TAG = "iperf";

static EventGroupHandle_t s_iperf_event_group = NULL;
#define IPERF_IP_READY_BIT   (1 << 0)
#define IPERF_STOP_REQ_BIT   (1 << 1)

// Check rate every 500ms
#define RATE_CHECK_INTERVAL_US    500000
// Minimum gap (Safety Limit)
#define MIN_PACING_INTERVAL_US    100

typedef struct {
    iperf_cfg_t cfg;
    bool finish;
    uint32_t buffer_len;
    uint8_t *buffer;
} iperf_ctrl_t;

static iperf_ctrl_t s_iperf_ctrl = {0};
static TaskHandle_t s_iperf_task_handle = NULL;
static esp_event_handler_instance_t instance_any_id;
static esp_event_handler_instance_t instance_got_ip;

static void iperf_network_event_handler(void* arg, esp_event_base_t event_base, int32_t event_id, void* event_data) {
    if (s_iperf_event_group == NULL) return;
    if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        xEventGroupSetBits(s_iperf_event_group, IPERF_IP_READY_BIT);
    }
    else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        xEventGroupClearBits(s_iperf_event_group, IPERF_IP_READY_BIT);
        status_led_set_state(LED_STATE_NO_CONFIG); // Yellow
    }
}

static bool iperf_wait_for_ip(void) {
    if (!s_iperf_event_group) s_iperf_event_group = xEventGroupCreate();
    ESP_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &iperf_network_event_handler, NULL, &instance_any_id));
    ESP_ERROR_CHECK(esp_event_handler_instance_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &iperf_network_event_handler, NULL, &instance_got_ip));

    esp_netif_t *netif = esp_netif_get_handle_from_ifkey("WIFI_STA_DEF");
    if (netif) {
        esp_netif_ip_info_t ip_info;
        if (esp_netif_get_ip_info(netif, &ip_info) == ESP_OK && ip_info.ip.addr != 0) {
            xEventGroupSetBits(s_iperf_event_group, IPERF_IP_READY_BIT);
        }
    }
    EventBits_t bits = xEventGroupWaitBits(s_iperf_event_group, IPERF_IP_READY_BIT | IPERF_STOP_REQ_BIT, pdFALSE, pdFALSE, portMAX_DELAY);
    esp_event_handler_instance_unregister(WIFI_EVENT, ESP_EVENT_ANY_ID, instance_any_id);
    esp_event_handler_instance_unregister(IP_EVENT, IP_EVENT_STA_GOT_IP, instance_got_ip);
    return !(bits & IPERF_STOP_REQ_BIT);
}

static void trim_whitespace(char *str) {
    char *end = str + strlen(str) - 1;
    while(end > str && isspace((unsigned char)*end)) end--;
    *(end+1) = 0;
}

static void iperf_read_nvs_config(iperf_cfg_t *cfg) {
    nvs_handle_t my_handle;
    if (nvs_open("storage", NVS_READONLY, &my_handle) != ESP_OK) return;

    uint32_t val;
    if (nvs_get_u32(my_handle, NVS_KEY_IPERF_PERIOD, &val) == ESP_OK) cfg->pacing_period_us = val;
    if (nvs_get_u32(my_handle, NVS_KEY_IPERF_BURST, &val) == ESP_OK) cfg->burst_count = val;
    if (nvs_get_u32(my_handle, NVS_KEY_IPERF_LEN, &val) == ESP_OK) cfg->send_len = val;
    if (nvs_get_u32(my_handle, NVS_KEY_IPERF_PORT, &val) == ESP_OK) cfg->dport = (uint16_t)val;

    size_t req;
    if (nvs_get_str(my_handle, NVS_KEY_IPERF_DST_IP, NULL, &req) == ESP_OK) {
        char *ip_str = malloc(req);
        if (ip_str) {
            nvs_get_str(my_handle, NVS_KEY_IPERF_DST_IP, ip_str, &req);
            trim_whitespace(ip_str);
            cfg->dip = inet_addr(ip_str);
            free(ip_str);
        }
    }
    nvs_close(my_handle);
}

void iperf_set_pps(uint32_t pps) {
    if (pps == 0) pps = 1;
    uint32_t period_us = 1000000 / pps;

    if (period_us < MIN_PACING_INTERVAL_US) {
        period_us = MIN_PACING_INTERVAL_US;
        ESP_LOGW(TAG, "PPS %" PRIu32 " clamped to max safe rate", pps);
    }

    if (s_iperf_task_handle != NULL) {
        s_iperf_ctrl.cfg.pacing_period_us = period_us;
        ESP_LOGI(TAG, "Runtime pacing updated to %" PRIu32 " PPS", pps);
    } else {
        s_iperf_ctrl.cfg.pacing_period_us = period_us;
    }
}

uint32_t iperf_get_pps(void) {
    if (s_iperf_ctrl.cfg.pacing_period_us == 0) return 0;
    return 1000000 / s_iperf_ctrl.cfg.pacing_period_us;
}

static esp_err_t iperf_start_udp_client(iperf_ctrl_t *ctrl) {
    if (!iperf_wait_for_ip()) return ESP_FAIL;

    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = htons(ctrl->cfg.dport > 0 ? ctrl->cfg.dport : 5001);
    addr.sin_addr.s_addr = ctrl->cfg.dip;

    int sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd < 0) {
        status_led_set_state(LED_STATE_FAILED);
        return ESP_FAIL;
    }

    status_led_set_state(LED_STATE_TRANSMITTING_SLOW); // Default state

    int64_t next_send_time = esp_timer_get_time();
    int64_t end_time = (ctrl->cfg.time == 0) ? INT64_MAX : esp_timer_get_time() + (int64_t)ctrl->cfg.time * 1000000LL;

    int64_t last_rate_check = esp_timer_get_time();
    uint32_t packets_since_check = 0;
    int64_t enomem_start_time = 0;

    while (!ctrl->finish && esp_timer_get_time() < end_time) {
        int64_t now = esp_timer_get_time();
        int64_t wait = next_send_time - now;

        if (wait > 2000) vTaskDelay(pdMS_TO_TICKS(wait / 1000));
        else while (esp_timer_get_time() < next_send_time) taskYIELD();

        for (int k = 0; k < ctrl->cfg.burst_count; k++) {
            int sent = sendto(sockfd, ctrl->buffer, ctrl->cfg.send_len, 0, (struct sockaddr *)&addr, sizeof(addr));

            if (sent > 0) {
                packets_since_check++;
                enomem_start_time = 0;

                // --- DYNAMIC RATE HEALTH CHECK ---
                if (now - last_rate_check > RATE_CHECK_INTERVAL_US) {
                    int64_t interval = now - last_rate_check;
                    double cycles = (double)interval / (double)ctrl->cfg.pacing_period_us;
                    uint32_t expected_pkts = (uint32_t)(cycles * ctrl->cfg.burst_count);

                    // Threshold: 75% of expected rate
                    uint32_t threshold = (expected_pkts * 3) / 4;

                    led_state_t target = (packets_since_check >= threshold)
                                       ? LED_STATE_TRANSMITTING      // Busy (Fast Flash)
                                       : LED_STATE_TRANSMITTING_SLOW; // Slow (Slow Pulse)

                    if (status_led_get_state() != target) status_led_set_state(target);

                    last_rate_check = now;
                    packets_since_check = 0;
                }

            } else {
                if (errno == 12) { // ENOMEM
                    if (status_led_get_state() != LED_STATE_STALLED) status_led_set_state(LED_STATE_STALLED);

                    if (enomem_start_time == 0) enomem_start_time = now;
                    else if (now - enomem_start_time > 10000000) {
                        status_led_set_state(LED_STATE_FAILED); goto exit;
                    }
                    vTaskDelay(pdMS_TO_TICKS(10));
                } else {
                    status_led_set_state(LED_STATE_FAILED); goto exit;
                }
            }
        }
        next_send_time += ctrl->cfg.pacing_period_us;
    }

exit:
    if (status_led_get_state() != LED_STATE_FAILED) {
        EventBits_t bits = xEventGroupGetBits(s_iperf_event_group);
        status_led_set_state((bits & IPERF_IP_READY_BIT) ? LED_STATE_CONNECTED : LED_STATE_NO_CONFIG);
    }
    close(sockfd);
    return ESP_OK;
}

static void iperf_task(void *arg) {
    iperf_start_udp_client((iperf_ctrl_t *)arg);
    free(((iperf_ctrl_t *)arg)->buffer);
    vTaskDelete(NULL);
}

void iperf_start(iperf_cfg_t *cfg) {
    if (s_iperf_task_handle) return;
    s_iperf_ctrl.cfg = *cfg;
    if (s_iperf_ctrl.cfg.send_len == 0) s_iperf_ctrl.cfg.send_len = 1470;
    if (s_iperf_ctrl.cfg.pacing_period_us == 0) s_iperf_ctrl.cfg.pacing_period_us = 10000;
    if (s_iperf_ctrl.cfg.burst_count == 0) s_iperf_ctrl.cfg.burst_count = 1;

    iperf_read_nvs_config(&s_iperf_ctrl.cfg);
    s_iperf_ctrl.finish = false;
    s_iperf_ctrl.buffer_len = s_iperf_ctrl.cfg.send_len + 128;
    s_iperf_ctrl.buffer = calloc(1, s_iperf_ctrl.buffer_len);

    s_iperf_event_group = xEventGroupCreate();
    xTaskCreate(iperf_task, "iperf", 4096, &s_iperf_ctrl, 5, &s_iperf_task_handle);
}

void iperf_stop(void) {
    if (s_iperf_task_handle) {
        s_iperf_ctrl.finish = true;
        if (s_iperf_event_group) xEventGroupSetBits(s_iperf_event_group, IPERF_STOP_REQ_BIT);
    }
}