/*
 * (C) Copyright 2005- ECMWF.
 *
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
 *
 * In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
 * virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
 */

/**************************************
 *  Enrico Fucile
 **************************************/


#include "grib_api_internal.h"
#include <math.h>
#ifdef ECCODES_ON_WINDOWS
 #include <stdint.h>
#endif

/*
   This is used by make_class.pl

   START_CLASS_DEF
   CLASS      = accessor
   SUPER      = grib_accessor_class_double
   IMPLEMENTS = unpack_double;pack_double;is_missing
   IMPLEMENTS = init
   MEMBERS=const char*    scaleFactor
   MEMBERS=const char*    scaledValue
   END_CLASS_DEF

 */

/* START_CLASS_IMP */

/*

Don't edit anything between START_CLASS_IMP and END_CLASS_IMP
Instead edit values between START_CLASS_DEF and END_CLASS_DEF
or edit "accessor.class" and rerun ./make_class.pl

*/

static int is_missing(grib_accessor*);
static int pack_double(grib_accessor*, const double* val, size_t* len);
static int unpack_double(grib_accessor*, double* val, size_t* len);
static void init(grib_accessor*, const long, grib_arguments*);
static void init_class(grib_accessor_class*);

typedef struct grib_accessor_from_scale_factor_scaled_value
{
    grib_accessor att;
    /* Members defined in gen */
    /* Members defined in double */
    /* Members defined in from_scale_factor_scaled_value */
    const char* scaleFactor;
    const char* scaledValue;
} grib_accessor_from_scale_factor_scaled_value;

extern grib_accessor_class* grib_accessor_class_double;

static grib_accessor_class _grib_accessor_class_from_scale_factor_scaled_value = {
    &grib_accessor_class_double,                          /* super                     */
    "from_scale_factor_scaled_value",                     /* name                      */
    sizeof(grib_accessor_from_scale_factor_scaled_value), /* size                      */
    0,                                                    /* inited */
    &init_class,                                          /* init_class */
    &init,                                                /* init                      */
    0,                                                    /* post_init                      */
    0,                                                    /* free mem                       */
    0,                                                    /* describes himself         */
    0,                                                    /* get length of section     */
    0,                                                    /* get length of string      */
    0,                                                    /* get number of values      */
    0,                                                    /* get number of bytes      */
    0,                                                    /* get offset to bytes           */
    0,                                                    /* get native type               */
    0,                                                    /* get sub_section                */
    0,                                                    /* grib_pack procedures long      */
    &is_missing,                                          /* grib_pack procedures long      */
    0,                                                    /* grib_pack procedures long      */
    0,                                                    /* grib_unpack procedures long    */
    &pack_double,                                         /* grib_pack procedures double    */
    &unpack_double,                                       /* grib_unpack procedures double  */
    0,                                                    /* grib_pack procedures string    */
    0,                                                    /* grib_unpack procedures string  */
    0,                                                    /* grib_pack array procedures string    */
    0,                                                    /* grib_unpack array procedures string  */
    0,                                                    /* grib_pack procedures bytes     */
    0,                                                    /* grib_unpack procedures bytes   */
    0,                                                    /* pack_expression */
    0,                                                    /* notify_change   */
    0,                                                    /* update_size   */
    0,                                                    /* preferred_size   */
    0,                                                    /* resize   */
    0,                                                    /* nearest_smaller_value */
    0,                                                    /* next accessor    */
    0,                                                    /* compare vs. another accessor   */
    0,                                                    /* unpack only ith value          */
    0,                                                    /* unpack a subarray         */
    0,                                                    /* clear          */
    0,                                                    /* clone accessor          */
};


grib_accessor_class* grib_accessor_class_from_scale_factor_scaled_value = &_grib_accessor_class_from_scale_factor_scaled_value;


static void init_class(grib_accessor_class* c)
{
    c->dump                   = (*(c->super))->dump;
    c->next_offset            = (*(c->super))->next_offset;
    c->string_length          = (*(c->super))->string_length;
    c->value_count            = (*(c->super))->value_count;
    c->byte_count             = (*(c->super))->byte_count;
    c->byte_offset            = (*(c->super))->byte_offset;
    c->get_native_type        = (*(c->super))->get_native_type;
    c->sub_section            = (*(c->super))->sub_section;
    c->pack_missing           = (*(c->super))->pack_missing;
    c->pack_long              = (*(c->super))->pack_long;
    c->unpack_long            = (*(c->super))->unpack_long;
    c->pack_string            = (*(c->super))->pack_string;
    c->unpack_string          = (*(c->super))->unpack_string;
    c->pack_string_array      = (*(c->super))->pack_string_array;
    c->unpack_string_array    = (*(c->super))->unpack_string_array;
    c->pack_bytes             = (*(c->super))->pack_bytes;
    c->unpack_bytes           = (*(c->super))->unpack_bytes;
    c->pack_expression        = (*(c->super))->pack_expression;
    c->notify_change          = (*(c->super))->notify_change;
    c->update_size            = (*(c->super))->update_size;
    c->preferred_size         = (*(c->super))->preferred_size;
    c->resize                 = (*(c->super))->resize;
    c->nearest_smaller_value  = (*(c->super))->nearest_smaller_value;
    c->next                   = (*(c->super))->next;
    c->compare                = (*(c->super))->compare;
    c->unpack_double_element  = (*(c->super))->unpack_double_element;
    c->unpack_double_subarray = (*(c->super))->unpack_double_subarray;
    c->clear                  = (*(c->super))->clear;
    c->make_clone             = (*(c->super))->make_clone;
}

/* END_CLASS_IMP */

static void init(grib_accessor* a, const long l, grib_arguments* c)
{
    grib_accessor_from_scale_factor_scaled_value* self = (grib_accessor_from_scale_factor_scaled_value*)a;
    int n                                              = 0;
    grib_handle* hand                                  = grib_handle_of_accessor(a);

    self->scaleFactor = grib_arguments_get_name(hand, c, n++);
    self->scaledValue = grib_arguments_get_name(hand, c, n++);

    /* ECC-979: Allow user to encode */
    /* a->flags |= GRIB_ACCESSOR_FLAG_READ_ONLY; */
}

static float float_epsilon(void)
{
    float floatEps = 1.0;
    while (1 + floatEps / 2 != 1)
        floatEps /= 2;
    return floatEps;
}

static int is_approximately_equal(double a, double b, double epsilon)
{
    if (a == b)
        return 1;
    if (fabs(a - b) <= epsilon)
        return 1;
    return 0;
}

static double eval_value_factor(int64_t value, int64_t factor)
{
    return (double)value * pow(10.0, -factor);
}

static int pack_double(grib_accessor* a, const double* val, size_t* len)
{
    /* See ECC-979 */
    /* Evaluate self->scaleFactor and self->scaledValue from input double '*val' */
    grib_accessor_from_scale_factor_scaled_value* self = (grib_accessor_from_scale_factor_scaled_value*)a;
    grib_handle* hand                                  = grib_handle_of_accessor(a);
    int ret                                            = 0;
    int64_t factor = 0, prev_factor = 0;
    int64_t value = 0, prev_value = 0;
    double exact        = *val; /*the input*/
    const float epsilon = float_epsilon();
    int is_negative = 0;
    unsigned long maxval_value, maxval_factor; /*maximum allowable values*/
    grib_accessor *accessor_factor, *accessor_value;

    if (exact == 0) {
        if ((ret = grib_set_long_internal(hand, self->scaleFactor, 0)) != GRIB_SUCCESS)
            return ret;
        if ((ret = grib_set_long_internal(hand, self->scaledValue, 0)) != GRIB_SUCCESS)
            return ret;
        return GRIB_SUCCESS;
    }

    if (exact == GRIB_MISSING_DOUBLE) {
        if ((ret = grib_set_missing(hand, self->scaleFactor)) != GRIB_SUCCESS)
            return ret;
        if ((ret = grib_set_missing(hand, self->scaledValue)) != GRIB_SUCCESS)
            return ret;
        return GRIB_SUCCESS;
    }

    accessor_factor = grib_find_accessor(hand, self->scaleFactor);
    accessor_value  = grib_find_accessor(hand, self->scaledValue);
    if (!accessor_factor || !accessor_value) {
        grib_context_log(a->context, GRIB_LOG_ERROR, "Could not access keys %s and %s", self->scaleFactor, self->scaledValue);
        return GRIB_ENCODING_ERROR;
    }
    maxval_value  = (1UL << (accessor_value->length * 8)) - 2;  /* exclude missing */
    maxval_factor = (1UL << (accessor_factor->length * 8)) - 2; /* exclude missing */

    /* Loop until we find a close enough approximation. Keep the last good values */
    if (exact < 0) {
        is_negative = 1;
        exact *= -1;
    }
    factor = prev_factor = 0;
    value = prev_value = round(exact);
    while (!is_approximately_equal(exact, eval_value_factor(value, factor), epsilon) &&
           value < maxval_value &&
           factor < maxval_factor) {
        value = round(exact * pow(10., ++factor));
        if (value > maxval_value || factor > maxval_factor) {
            /* One or more maxima exceeded. So stop and use the previous values */
            value  = prev_value;
            factor = prev_factor;
            break;
        }
        prev_factor = factor;
        prev_value  = value;
    }

    if (is_negative) {
        value *= -1;
    }

    if ((ret = grib_set_long_internal(hand, self->scaleFactor, factor)) != GRIB_SUCCESS)
        return ret;
    if ((ret = grib_set_long_internal(hand, self->scaledValue, value)) != GRIB_SUCCESS)
        return ret;

    return GRIB_SUCCESS;
}

static int unpack_double(grib_accessor* a, double* val, size_t* len)
{
    grib_accessor_from_scale_factor_scaled_value* self = (grib_accessor_from_scale_factor_scaled_value*)a;
    int ret                                            = 0;
    long scaleFactor                                   = 0;
    long scaledValue                                   = 0;
    grib_handle* hand                                  = grib_handle_of_accessor(a);

    if ((ret = grib_get_long_internal(hand, self->scaleFactor, &scaleFactor)) != GRIB_SUCCESS)
        return ret;
    if ((ret = grib_get_long_internal(hand, self->scaledValue, &scaledValue)) != GRIB_SUCCESS)
        return ret;

    if (grib_is_missing(hand, self->scaledValue, &ret) && ret == GRIB_SUCCESS) {
        *val = GRIB_MISSING_DOUBLE;
        *len = 1;
        return GRIB_SUCCESS;
    } else {
        /* ECC-966: If scale factor is missing, print error and treat it as zero (as a fallback) */
        if (grib_is_missing(hand, self->scaleFactor, &ret) && ret == GRIB_SUCCESS) {
            grib_context_log(a->context, GRIB_LOG_ERROR,
                    "unpack_double for %s: %s is missing! Using zero instead", a->name, self->scaleFactor);
            scaleFactor = 0;
        }
    }

    *val = scaledValue;

    /* The formula is:
     *  real_value = scaled_value / pow(10, scale_factor)
     */
    while (scaleFactor < 0) {
        *val *= 10;
        scaleFactor++;
    }
    while (scaleFactor > 0) {
        *val /= 10;
        scaleFactor--;
    }

    if (ret == GRIB_SUCCESS)
        *len = 1;

    return ret;
}

static int is_missing(grib_accessor* a)
{
    grib_accessor_from_scale_factor_scaled_value* self = (grib_accessor_from_scale_factor_scaled_value*)a;
    int ret                                            = 0;
    long scaleFactor                                   = 0;
    long scaledValue                                   = 0;

    if ((ret = grib_get_long_internal(grib_handle_of_accessor(a), self->scaleFactor, &scaleFactor)) != GRIB_SUCCESS)
        return ret;

    if ((ret = grib_get_long_internal(grib_handle_of_accessor(a), self->scaledValue, &scaledValue)) != GRIB_SUCCESS)
        return ret;

    return ((scaleFactor == GRIB_MISSING_LONG) || (scaledValue == GRIB_MISSING_LONG));
}
