#include <string.h>

#include "esp_event.h"
#include "esp_log.h"
#include "esp_wifi.h"
#include "esp_wifi_default.h"
#include "esp_netif.h"
#include "esp_http_client.h"
#include "esp_sleep.h"

#include "freertos/FreeRTOS.h"
#include "freertos/event_groups.h"

#include "epd7in3e.h"
#include "status_screen.h"

#include "frame_client.h"

static const char *TAG = "frame_client";

#define STA_CONNECTED_BIT BIT0
#define STA_FAILED_BIT BIT1

static EventGroupHandle_t s_sta_event_group;

/* wifi_sta_config_t's ssid/password fields are fixed-size byte arrays, not
 * necessarily null-terminated (a full 32-char SSID fills the field exactly).
 * snprintf() flags that as a possible truncation at -Werror, so copy by
 * hand instead. */
static void copy_wifi_field(uint8_t *dst, size_t dst_size, const char *src)
{
    size_t len = strnlen(src, dst_size);
    memcpy(dst, src, len);
    if (len < dst_size) {
        dst[len] = '\0';
    }
}

static void sta_event_handler(void *arg, esp_event_base_t event_base,
                               int32_t event_id, void *event_data)
{
    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
        esp_wifi_connect();
    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        ESP_LOGW(TAG, "Disconnected from home WiFi");
        xEventGroupSetBits(s_sta_event_group, STA_FAILED_BIT);
    } else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        ip_event_got_ip_t *event = (ip_event_got_ip_t *)event_data;
        ESP_LOGI(TAG, "Got IP: " IPSTR, IP2STR(&event->ip_info.ip));
        xEventGroupSetBits(s_sta_event_group, STA_CONNECTED_BIT);
    }
}

esp_err_t frame_wifi_connect_sta(const frame_config_t *cfg)
{
    s_sta_event_group = xEventGroupCreate();

    esp_netif_t *sta_netif = esp_netif_create_default_wifi_sta();

    wifi_init_config_t init_cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&init_cfg));

    esp_event_handler_instance_t wifi_handler;
    esp_event_handler_instance_t ip_handler;
    ESP_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &sta_event_handler, NULL, &wifi_handler));
    ESP_ERROR_CHECK(esp_event_handler_instance_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &sta_event_handler, NULL, &ip_handler));

    wifi_config_t wifi_config = {0};
    copy_wifi_field(wifi_config.sta.ssid, sizeof(wifi_config.sta.ssid), cfg->sta_ssid);
    copy_wifi_field(wifi_config.sta.password, sizeof(wifi_config.sta.password), cfg->sta_password);

    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_STA));
    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_STA, &wifi_config));
    ESP_ERROR_CHECK(esp_wifi_start());

    esp_err_t result = ESP_FAIL;
    for (int attempt = 1; attempt <= CONFIG_FRAME_STA_CONNECT_MAX_RETRIES; attempt++) {
        ESP_LOGI(TAG, "Connecting to '%s' (attempt %d/%d)", cfg->sta_ssid, attempt,
                 CONFIG_FRAME_STA_CONNECT_MAX_RETRIES);

        xEventGroupClearBits(s_sta_event_group, STA_CONNECTED_BIT | STA_FAILED_BIT);
        esp_wifi_connect();

        EventBits_t bits = xEventGroupWaitBits(s_sta_event_group, STA_CONNECTED_BIT | STA_FAILED_BIT,
                                                pdTRUE, pdFALSE,
                                                pdMS_TO_TICKS(CONFIG_FRAME_STA_CONNECT_TIMEOUT_MS));

        if (bits & STA_CONNECTED_BIT) {
            result = ESP_OK;
            break;
        }
        ESP_LOGW(TAG, "Attempt %d/%d failed", attempt, CONFIG_FRAME_STA_CONNECT_MAX_RETRIES);
    }

    esp_event_handler_instance_unregister(WIFI_EVENT, ESP_EVENT_ANY_ID, wifi_handler);
    esp_event_handler_instance_unregister(IP_EVENT, IP_EVENT_STA_GOT_IP, ip_handler);
    vEventGroupDelete(s_sta_event_group);
    s_sta_event_group = NULL;

    if (result != ESP_OK) {
        /* Fully tear the WiFi driver back down on failure -- the caller
         * falls back to provisioning, which calls esp_wifi_init() again
         * for AP mode. Leaving the driver merely stopped (rather than
         * deinitialized) made that second esp_wifi_init() call fail with
         * ESP_ERR_INVALID_STATE and abort, confirmed on hardware. */
        esp_wifi_stop();
        esp_wifi_deinit();
        esp_netif_destroy_default_wifi(sta_netif);
    }

    return result;
}

/* Probes cfg->toolsserver with a plain HTTP HEAD -- any HTTP response
 * (even a 404, since there's no server yet to define real routes) means
 * the socket-level connection succeeded, which is all this is checking. */
static bool check_server_reachable(const char *toolsserver)
{
    char url[160];
    snprintf(url, sizeof(url), "http://%s/", toolsserver);

    esp_http_client_config_t config = {
        .url = url,
        .method = HTTP_METHOD_HEAD,
        .timeout_ms = CONFIG_FRAME_SERVER_CHECK_TIMEOUT_MS,
    };
    esp_http_client_handle_t client = esp_http_client_init(&config);
    esp_err_t err = esp_http_client_perform(client);
    esp_http_client_cleanup(client);

    if (err != ESP_OK) {
        ESP_LOGW(TAG, "Server '%s' not reachable: %s", toolsserver, esp_err_to_name(err));
    }
    return err == ESP_OK;
}

typedef struct {
    esp_http_client_handle_t client;
} http_read_ctx_t;

/* Pulls the next chunk straight out of the in-progress HTTP response --
 * epd_display_stream() calls this to feed the panel without ever holding
 * the full ~192KB frame in RAM. */
static size_t http_read_fn(uint8_t *chunk, size_t chunk_size, void *ctx_)
{
    http_read_ctx_t *ctx = (http_read_ctx_t *)ctx_;
    int n = esp_http_client_read(ctx->client, (char *)chunk, (int)chunk_size);
    return n > 0 ? (size_t)n : 0;
}

/* GETs /frame/image and streams the response directly into the panel. */
static esp_err_t fetch_and_display(const frame_config_t *cfg)
{
    char url[160];
    snprintf(url, sizeof(url), "http://%s/frame/image", cfg->toolsserver);

    esp_http_client_config_t config = {
        .url = url,
        .method = HTTP_METHOD_GET,
        .timeout_ms = CONFIG_FRAME_FETCH_TIMEOUT_MS,
    };
    esp_http_client_handle_t client = esp_http_client_init(&config);

    esp_err_t err = esp_http_client_open(client, 0);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "Failed to open '%s': %s", url, esp_err_to_name(err));
        esp_http_client_cleanup(client);
        return err;
    }

    int content_length = esp_http_client_fetch_headers(client);
    int status = esp_http_client_get_status_code(client);
    if (status != 200) {
        ESP_LOGE(TAG, "'%s' returned HTTP %d", url, status);
        esp_http_client_close(client);
        esp_http_client_cleanup(client);
        return ESP_FAIL;
    }
    ESP_LOGI(TAG, "Fetching frame (%d bytes) from '%s'", content_length, url);

    http_read_ctx_t ctx = { .client = client };
    err = epd_display_stream(http_read_fn, &ctx);

    esp_http_client_close(client);
    esp_http_client_cleanup(client);

    return err;
}

void frame_client_run(const frame_config_t *cfg)
{
    esp_err_t epd_err = epd_init();
    bool have_display = (epd_err == ESP_OK);
    if (!have_display) {
        ESP_LOGW(TAG, "EPD init failed (%s), continuing without display", esp_err_to_name(epd_err));
    }

    uint32_t sleep_seconds = CONFIG_FRAME_SLEEP_INTERVAL_S;
    bool server_reachable = check_server_reachable(cfg->toolsserver);

    if (!server_reachable) {
        /* Nothing's been drawn yet this cycle, so this is the only
         * refresh -- cheap diagnostics without compounding flashing. */
        ESP_LOGW(TAG, "Tools server not reachable, retrying sooner");
        sleep_seconds = CONFIG_FRAME_RETRY_INTERVAL_S;
        if (have_display) {
            status_screen_show(cfg->sta_ssid, STATUS_OK, cfg->toolsserver, STATUS_FAILED);
        }
    } else if (have_display) {
        esp_err_t fetch_err = fetch_and_display(cfg);
        if (fetch_err != ESP_OK) {
            /* The panel may have already partially refreshed with a
             * truncated frame by this point -- log and retry sooner
             * rather than drawing a second status screen on top of it. */
            ESP_LOGW(TAG, "Fetch/display failed (%s), retrying sooner", esp_err_to_name(fetch_err));
            sleep_seconds = CONFIG_FRAME_RETRY_INTERVAL_S;
        }
    }

    if (have_display) {
        epd_sleep();
    }

    ESP_LOGI(TAG, "Deep sleeping for %u seconds", (unsigned)sleep_seconds);
    esp_sleep_enable_timer_wakeup((uint64_t)sleep_seconds * 1000000ULL);
    esp_deep_sleep_start();
}