#include "aes67_cfg.h"

#include <math.h>
#include <stdio.h>
#include <string.h>

#include "aes67_web.h"
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/semphr.h"
#include "lwip/inet.h"
#include "nvs.h"
#include "nvs_flash.h"

#define MAX_GROUPS      12
#define MAX_BODY        8192
#define NVS_NAMESPACE   "cfg"

static const char *TAG = "cfg";

typedef struct {
    char name[16];          // also the NVS key (max 15 chars)
    cJSON *defaults;
    cJSON *values;
    cfg_validate_cb_t validate;
    cfg_apply_cb_t apply;
} cfg_group_t;

static cfg_group_t s_groups[MAX_GROUPS];
static int s_group_n;
static cJSON *s_overrides;  // {group: {...}} from cfg_override_defaults
static SemaphoreHandle_t s_lock;
static bool s_nvs_ok;

static void cfg_init_once(void)
{
    if (s_lock) {
        return;
    }
    s_lock = xSemaphoreCreateMutex();
    s_overrides = cJSON_CreateObject();
    esp_err_t err = nvs_flash_init();
    if (err == ESP_ERR_NVS_NO_FREE_PAGES || err == ESP_ERR_NVS_NEW_VERSION_FOUND) {
        ESP_LOGW(TAG, "NVS needs erase (%s), config reset to defaults", esp_err_to_name(err));
        nvs_flash_erase();
        err = nvs_flash_init();
    }
    s_nvs_ok = err == ESP_OK;
    if (!s_nvs_ok) {
        ESP_LOGE(TAG, "NVS init failed: %s; config will not persist", esp_err_to_name(err));
    }
}

static cfg_group_t *find(const char *name)
{
    for (int i = 0; i < s_group_n; i++) {
        if (strcmp(s_groups[i].name, name) == 0) {
            return &s_groups[i];
        }
    }
    return NULL;
}

// Same JSON kind for our purposes: number, string or bool.
static bool same_type(const cJSON *a, const cJSON *b)
{
    if (cJSON_IsBool(a)) {
        return cJSON_IsBool(b);
    }
    return (a->type & 0xFF) == (b->type & 0xFF);
}

static const char *type_name(const cJSON *v)
{
    return cJSON_IsBool(v) ? "boolean" : cJSON_IsNumber(v) ? "number" : cJSON_IsString(v) ? "string" : "value";
}

// Copy known keys of src over dst (keys must exist in defs with the same type).
// With err set, a type mismatch is an error; otherwise it is skipped with a warning.
static bool merge_known(cJSON *dst, const cJSON *defs, const cJSON *src, const char *group,
                        char *err, size_t err_len)
{
    const cJSON *v;
    cJSON_ArrayForEach(v, src) {
        const cJSON *d = cJSON_GetObjectItemCaseSensitive(defs, v->string);
        if (!d) {
            ESP_LOGW(TAG, "%s.%s: unknown key, ignored", group, v->string);
            continue;
        }
        if (!same_type(d, v)) {
            if (err) {
                snprintf(err, err_len, "%s.%s: expected %s", group, v->string, type_name(d));
                return false;
            }
            ESP_LOGW(TAG, "%s.%s: stored type differs from default, ignored", group, v->string);
            continue;
        }
        cJSON_ReplaceItemInObjectCaseSensitive(dst, v->string, cJSON_Duplicate(v, true));
    }
    return true;
}

static void load_stored(cfg_group_t *g)
{
    if (!s_nvs_ok) {
        return;
    }
    nvs_handle_t h;
    if (nvs_open(NVS_NAMESPACE, NVS_READONLY, &h) != ESP_OK) {
        return;  // nothing stored yet
    }
    size_t len = 0;
    if (nvs_get_str(h, g->name, NULL, &len) == ESP_OK && len > 0) {
        char *buf = malloc(len);
        if (buf && nvs_get_str(h, g->name, buf, &len) == ESP_OK) {
            cJSON *stored = cJSON_Parse(buf);
            if (cJSON_IsObject(stored)) {
                merge_known(g->values, g->defaults, stored, g->name, NULL, 0);
                ESP_LOGI(TAG, "%s: loaded %d stored value(s)", g->name, cJSON_GetArraySize(stored));
            } else {
                ESP_LOGW(TAG, "%s: stored config unreadable, using defaults", g->name);
            }
            cJSON_Delete(stored);
        }
        free(buf);
    }
    nvs_close(h);
}

// Store only the keys that differ from the defaults, so new firmware defaults still apply
// to settings the user never changed.
static esp_err_t store(nvs_handle_t h, const cfg_group_t *g)
{
    cJSON *diff = cJSON_CreateObject();
    const cJSON *v;
    cJSON_ArrayForEach(v, g->values) {
        const cJSON *d = cJSON_GetObjectItemCaseSensitive(g->defaults, v->string);
        if (!d || !cJSON_Compare(d, v, true)) {
            cJSON_AddItemToObject(diff, v->string, cJSON_Duplicate(v, true));
        }
    }
    esp_err_t err;
    if (cJSON_GetArraySize(diff) == 0) {
        err = nvs_erase_key(h, g->name);
        if (err == ESP_ERR_NVS_NOT_FOUND) {
            err = ESP_OK;
        }
    } else {
        char *s = cJSON_PrintUnformatted(diff);
        err = s ? nvs_set_str(h, g->name, s) : ESP_ERR_NO_MEM;
        cJSON_free(s);
    }
    cJSON_Delete(diff);
    return err;
}

esp_err_t cfg_override_defaults(const char *group, const char *json)
{
    cfg_init_once();
    cJSON *o = cJSON_Parse(json);
    if (!cJSON_IsObject(o)) {
        cJSON_Delete(o);
        ESP_LOGE(TAG, "%s: bad override JSON", group);
        return ESP_ERR_INVALID_ARG;
    }
    xSemaphoreTake(s_lock, portMAX_DELAY);
    cJSON *prev = cJSON_GetObjectItemCaseSensitive(s_overrides, group);
    if (prev) {
        const cJSON *v;
        cJSON_ArrayForEach(v, o) {
            cJSON_DeleteItemFromObjectCaseSensitive(prev, v->string);
            cJSON_AddItemToObject(prev, v->string, cJSON_Duplicate(v, true));
        }
        cJSON_Delete(o);
    } else {
        cJSON_AddItemToObject(s_overrides, group, o);
    }
    bool late = find(group) != NULL;
    xSemaphoreGive(s_lock);
    if (late) {
        ESP_LOGE(TAG, "%s: override after register has no effect", group);
        return ESP_ERR_INVALID_STATE;
    }
    return ESP_OK;
}

esp_err_t cfg_register(const char *group, const char *defaults_json,
                       cfg_validate_cb_t validate, cfg_apply_cb_t apply)
{
    cfg_init_once();
    if (strlen(group) >= sizeof(s_groups[0].name)) {
        return ESP_ERR_INVALID_ARG;
    }
    cJSON *defs = cJSON_Parse(defaults_json);
    if (!cJSON_IsObject(defs)) {
        cJSON_Delete(defs);
        ESP_LOGE(TAG, "%s: bad defaults JSON", group);
        return ESP_ERR_INVALID_ARG;
    }

    xSemaphoreTake(s_lock, portMAX_DELAY);
    if (find(group) || s_group_n >= MAX_GROUPS) {
        xSemaphoreGive(s_lock);
        cJSON_Delete(defs);
        ESP_LOGE(TAG, "%s: already registered or registry full", group);
        return ESP_ERR_INVALID_STATE;
    }
    const cJSON *ov = cJSON_GetObjectItemCaseSensitive(s_overrides, group);
    if (ov) {
        merge_known(defs, defs, ov, group, NULL, 0);
    }
    cfg_group_t *g = &s_groups[s_group_n++];
    strcpy(g->name, group);
    g->defaults = defs;
    g->values = cJSON_Duplicate(defs, true);
    g->validate = validate;
    g->apply = apply;
    load_stored(g);
    xSemaphoreGive(s_lock);
    return ESP_OK;
}

cJSON *cfg_get(const char *group)
{
    if (!s_lock) {
        return NULL;
    }
    xSemaphoreTake(s_lock, portMAX_DELAY);
    cfg_group_t *g = find(group);
    cJSON *copy = g ? cJSON_Duplicate(g->values, true) : NULL;
    xSemaphoreGive(s_lock);
    return copy;
}

esp_err_t cfg_set_number(const char *group, const char *key, double value, bool apply)
{
    if (!s_lock) {
        return ESP_ERR_INVALID_STATE;
    }
    xSemaphoreTake(s_lock, portMAX_DELAY);
    cfg_group_t *g = find(group);
    cJSON *cur = g ? cJSON_GetObjectItemCaseSensitive(g->values, key) : NULL;
    esp_err_t err = ESP_OK;
    if (!cur || !cJSON_IsNumber(cur)) {
        err = ESP_ERR_NOT_FOUND;
    } else {
        cJSON_SetNumberValue(cur, value);
        nvs_handle_t h;
        if (s_nvs_ok && (err = nvs_open(NVS_NAMESPACE, NVS_READWRITE, &h)) == ESP_OK) {
            err = store(h, g);
            if (err == ESP_OK) {
                err = nvs_commit(h);
            }
            nvs_close(h);
        }
    }
    cJSON *copy = err == ESP_OK && apply && g->apply ? cJSON_Duplicate(g->values, true) : NULL;
    xSemaphoreGive(s_lock);
    if (copy) {
        g->apply(copy);
        cJSON_Delete(copy);
    }
    return err;
}

/* ----- HTTP ----- */

static esp_err_t config_get(httpd_req_t *req)
{
    cJSON *all = cJSON_CreateObject();
    xSemaphoreTake(s_lock, portMAX_DELAY);
    for (int i = 0; i < s_group_n; i++) {
        cJSON_AddItemToObject(all, s_groups[i].name, cJSON_Duplicate(s_groups[i].values, true));
    }
    xSemaphoreGive(s_lock);
    esp_err_t err = web_send_json(req, all);
    cJSON_Delete(all);
    return err;
}

static esp_err_t bad_request(httpd_req_t *req, const char *msg)
{
    ESP_LOGW(TAG, "POST /api/config rejected: %s", msg);
    return httpd_resp_send_err(req, HTTPD_400_BAD_REQUEST, msg);
}

static esp_err_t config_post(httpd_req_t *req)
{
    if (req->content_len == 0 || req->content_len > MAX_BODY) {
        return bad_request(req, "body missing or too large");
    }
    char *body = malloc(req->content_len + 1);
    if (!body) {
        return httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "out of memory");
    }
    size_t got = 0;
    while (got < req->content_len) {
        int r = httpd_req_recv(req, body + got, req->content_len - got);
        if (r == HTTPD_SOCK_ERR_TIMEOUT) {
            continue;
        }
        if (r <= 0) {
            free(body);
            return ESP_FAIL;
        }
        got += r;
    }
    body[got] = 0;
    cJSON *in = cJSON_Parse(body);
    free(body);
    if (!cJSON_IsObject(in)) {
        cJSON_Delete(in);
        return bad_request(req, "body is not a JSON object");
    }

    char err[128] = "";
    cJSON *cand[MAX_GROUPS] = { 0 };
    bool ok = true;

    xSemaphoreTake(s_lock, portMAX_DELAY);
    // Build and validate every candidate group before storing anything.
    for (int i = 0; ok && i < s_group_n; i++) {
        cfg_group_t *g = &s_groups[i];
        const cJSON *src = cJSON_GetObjectItemCaseSensitive(in, g->name);
        if (!src) {
            continue;
        }
        if (!cJSON_IsObject(src)) {
            snprintf(err, sizeof(err), "%s: expected object", g->name);
            ok = false;
            break;
        }
        cand[i] = cJSON_Duplicate(g->values, true);
        ok = merge_known(cand[i], g->defaults, src, g->name, err, sizeof(err));
        if (ok && g->validate) {
            char verr[96] = "";
            ok = g->validate(cand[i], verr, sizeof(verr));
            if (!ok) {
                snprintf(err, sizeof(err), "%s.%s", g->name, verr);
            }
        }
    }
    const cJSON *v;
    cJSON_ArrayForEach(v, in) {
        if (!find(v->string)) {
            ESP_LOGW(TAG, "%s: unknown group, ignored", v->string);
        }
    }

    esp_err_t serr = ESP_OK;
    int changed = 0;
    if (ok && s_nvs_ok) {
        nvs_handle_t h;
        serr = nvs_open(NVS_NAMESPACE, NVS_READWRITE, &h);
        for (int i = 0; serr == ESP_OK && i < s_group_n; i++) {
            if (cand[i] && !cJSON_Compare(cand[i], s_groups[i].values, true)) {
                cJSON *old = s_groups[i].values;
                s_groups[i].values = cand[i];
                serr = store(h, &s_groups[i]);
                if (serr != ESP_OK) {
                    s_groups[i].values = old;
                    break;
                }
                cand[i] = old;  // freed below
                changed |= 1 << i;
            }
        }
        if (serr == ESP_OK) {
            serr = nvs_commit(h);
        }
        nvs_close(h);
    }
    for (int i = 0; i < s_group_n; i++) {
        cJSON_Delete(cand[i]);
    }

    // Apply after the lock is released; callbacks may call cfg_get().
    cJSON *applied[MAX_GROUPS] = { 0 };
    for (int i = 0; i < s_group_n; i++) {
        if ((changed & (1 << i)) && s_groups[i].apply) {
            applied[i] = cJSON_Duplicate(s_groups[i].values, true);
        }
    }
    int group_n = s_group_n;
    xSemaphoreGive(s_lock);
    cJSON_Delete(in);

    if (!ok) {
        return bad_request(req, err);
    }
    if (!s_nvs_ok || serr != ESP_OK) {
        ESP_LOGE(TAG, "store failed: %s", s_nvs_ok ? esp_err_to_name(serr) : "NVS unavailable");
        return httpd_resp_send_err(req, HTTPD_500_INTERNAL_SERVER_ERROR, "could not store config");
    }
    for (int i = 0; i < group_n; i++) {
        if (changed & (1 << i)) {
            ESP_LOGI(TAG, "%s: saved", s_groups[i].name);
        }
        if (applied[i]) {
            s_groups[i].apply(applied[i]);
            cJSON_Delete(applied[i]);
        }
    }
    return config_get(req);
}

esp_err_t cfg_web_register(void)
{
    static const httpd_uri_t uris[] = {
        { .uri = "/api/config", .method = HTTP_GET,  .handler = config_get },
        { .uri = "/api/config", .method = HTTP_POST, .handler = config_post },
    };
    cfg_init_once();
    for (int i = 0; i < 2; i++) {
        esp_err_t err = web_register_uri(&uris[i]);
        if (err != ESP_OK) {
            return err;
        }
    }
    return ESP_OK;
}

/* ----- Validation helpers ----- */

static const cJSON *item(const cJSON *g, const char *key)
{
    return cJSON_GetObjectItemCaseSensitive(g, key);
}

bool cfg_check_num(const cJSON *g, const char *key, double min, double max, char *err, size_t n)
{
    const cJSON *v = item(g, key);
    if (!cJSON_IsNumber(v) || v->valuedouble < min || v->valuedouble > max) {
        snprintf(err, n, "%s: must be %g..%g", key, min, max);
        return false;
    }
    return true;
}

bool cfg_check_int(const cJSON *g, const char *key, double min, double max, char *err, size_t n)
{
    if (!cfg_check_num(g, key, min, max, err, n)) {
        return false;
    }
    double d = item(g, key)->valuedouble;
    if (d != floor(d)) {
        snprintf(err, n, "%s: must be a whole number", key);
        return false;
    }
    return true;
}

bool cfg_check_num_in(const cJSON *g, const char *key, const double *vals, int count, char *err, size_t n)
{
    const cJSON *v = item(g, key);
    for (int i = 0; cJSON_IsNumber(v) && i < count; i++) {
        if (v->valuedouble == vals[i]) {
            return true;
        }
    }
    int off = snprintf(err, n, "%s: must be one of", key);
    for (int i = 0; i < count && off > 0 && off < (int)n; i++) {
        off += snprintf(err + off, n - off, " %g", vals[i]);
    }
    return false;
}

bool cfg_check_enum(const cJSON *g, const char *key, const char *const *opts, char *err, size_t n)
{
    const cJSON *v = item(g, key);
    for (int i = 0; cJSON_IsString(v) && opts[i]; i++) {
        if (strcmp(v->valuestring, opts[i]) == 0) {
            return true;
        }
    }
    int off = snprintf(err, n, "%s: must be one of", key);
    for (int i = 0; opts[i] && off > 0 && off < (int)n; i++) {
        off += snprintf(err + off, n - off, " %s", opts[i]);
    }
    return false;
}

bool cfg_check_str(const cJSON *g, const char *key, size_t min_len, size_t max_len, char *err, size_t n)
{
    const cJSON *v = item(g, key);
    size_t len = cJSON_IsString(v) ? strlen(v->valuestring) : 0;
    if (!cJSON_IsString(v) || len < min_len || len > max_len) {
        snprintf(err, n, "%s: length must be %u..%u", key, (unsigned)min_len, (unsigned)max_len);
        return false;
    }
    return true;
}

bool cfg_check_ipv4(const cJSON *g, const char *key, bool allow_empty, char *err, size_t n)
{
    const cJSON *v = item(g, key);
    struct in_addr a;
    if (cJSON_IsString(v) && ((allow_empty && !v->valuestring[0]) || inet_aton(v->valuestring, &a))) {
        return true;
    }
    snprintf(err, n, "%s: not a valid IPv4 address", key);
    return false;
}