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/*! \internal \file
 * \brief
 * Implements internal selection method for comparison expressions.
 *
 * \author Teemu Murtola <teemu.murtola@gmail.com>
 * \ingroup module_selection
 */
#include "gmxpre.h"

#include <cmath>
#include <cstdio>

#include "gromacs/math/utilities.h"
#include "gromacs/selection/indexutil.h"
#include "gromacs/selection/selparam.h"
#include "gromacs/selection/selvalue.h"
#include "gromacs/utility/arraysize.h"
#include "gromacs/utility/basedefinitions.h"
#include "gromacs/utility/exceptions.h"
#include "gromacs/utility/real.h"
#include "gromacs/utility/smalloc.h"

#include "keywords.h"
#include "selmethod.h"

struct gmx_mtop_t;

/** Defines the comparison operator for comparison expressions. */
typedef enum
{
    CMP_INVALID, /**< Indicates an error */
    CMP_LESS,    /**< '<' */
    CMP_LEQ,     /**< '<=' */
    CMP_GTR,     /**< '>' */
    CMP_GEQ,     /**< '>=' */
    CMP_EQUAL,   /**< '==' */
    CMP_NEQ      /**< '!=' */
} e_comparison_t;

/** The operand has a single value. */
#define CMP_SINGLEVAL 1
/** The operand value is dynamic. */
#define CMP_DYNAMICVAL 2
/** The value is real. */
#define CMP_REALVAL 4
/** The integer array is allocated. */
#define CMP_ALLOCINT 16
/** The real array is allocated. */
#define CMP_ALLOCREAL 32

/*! \internal \brief
 * Data structure for comparison expression operand values.
 */
typedef struct
{
    /** Flags that describe the type of the operand. */
    int flags;
    /** (Array of) integer value(s). */
    int* i;
    /** (Array of) real value(s). */
    real* r;
} t_compare_value;

/*! \internal \brief
 * Data structure for comparison expression evaluation.
 */
typedef struct
{
    /** Comparison operator as a string. */
    char* cmpop;
    /** Comparison operator type. */
    e_comparison_t cmpt;
    /** Left value. */
    t_compare_value left;
    /** Right value. */
    t_compare_value right;
} t_methoddata_compare;

/*! \brief
 * Allocates data for comparison expression evaluation.
 *
 * \param[in]     npar  Not used (should be 5).
 * \param[in,out] param Method parameters (should point to a copy of
 *   \ref smparams_compare).
 * \returns       Pointer to the allocated data (\c t_methoddata_compare).
 *
 * Allocates memory for a \c t_methoddata_compare structure.
 */
static void* init_data_compare(int npar, gmx_ana_selparam_t* param);
/*! \brief
 * Initializes data for comparison expression evaluation.
 *
 * \param[in] top   Not used.
 * \param[in] npar  Not used (should be 5).
 * \param[in] param Method parameters (should point to \ref smparams_compare).
 * \param[in] data  Should point to a \c t_methoddata_compare.
 */
static void init_compare(const gmx_mtop_t* top, int npar, gmx_ana_selparam_t* param, void* data);
/** Frees the memory allocated for comparison expression evaluation. */
static void free_data_compare(void* data);
/*! \brief
 * Evaluates comparison expressions.
 *
 * \param[in]  context  Not used.
 * \param[in]  g        Evaluation index group.
 * \param[out] out      Output data structure (\p out->u.g is used).
 * \param[in]  data     Should point to a \c t_methoddata_compare.
 */
static void evaluate_compare(const gmx::SelMethodEvalContext& context,
                             gmx_ana_index_t*                 g,
                             gmx_ana_selvalue_t*              out,
                             void*                            data);

/** Parameters for comparison expression evaluation. */
static gmx_ana_selparam_t smparams_compare[] = {
    { "int1", { INT_VALUE, -1, { nullptr } }, nullptr, SPAR_OPTIONAL | SPAR_DYNAMIC | SPAR_ATOMVAL },
    { "real1", { REAL_VALUE, -1, { nullptr } }, nullptr, SPAR_OPTIONAL | SPAR_DYNAMIC | SPAR_ATOMVAL },
    { "op", { STR_VALUE, 1, { nullptr } }, nullptr, 0 },
    { "int2", { INT_VALUE, -1, { nullptr } }, nullptr, SPAR_OPTIONAL | SPAR_DYNAMIC | SPAR_ATOMVAL },
    { "real2", { REAL_VALUE, -1, { nullptr } }, nullptr, SPAR_OPTIONAL | SPAR_DYNAMIC | SPAR_ATOMVAL },
};

/** \internal Selection method data for comparison expression evaluation. */
gmx_ana_selmethod_t sm_compare = {
    "cmp",
    GROUP_VALUE,
    SMETH_SINGLEVAL,
    asize(smparams_compare),
    smparams_compare,
    &init_data_compare,
    nullptr,
    &init_compare,
    nullptr,
    &free_data_compare,
    nullptr,
    &evaluate_compare,
    nullptr,
    { nullptr, nullptr, 0, nullptr },
};

/*! \brief
 * Returns a \c e_comparison_t value corresponding to an operator.
 *
 * \param[in] str  String to process.
 * \returns   The comparison type corresponding to the first one or two
 *   characters of \p str.
 *
 * \p str can contain any number of characters; only the first two
 * are used.
 * If the beginning of \p str does not match any of the recognized types,
 * \ref CMP_INVALID is returned.
 */
static e_comparison_t comparison_type(const char* str)
{
    switch (str[0])
    {
        case '<': return (str[1] == '=') ? CMP_LEQ : CMP_LESS;
        case '>': return (str[1] == '=') ? CMP_GEQ : CMP_GTR;
        case '=': return (str[1] == '=') ? CMP_EQUAL : CMP_INVALID;
        case '!': return (str[1] == '=') ? CMP_NEQ : CMP_INVALID;
    }
    return CMP_INVALID;
}

/*! \brief
 * Returns a string corresponding to a \c e_comparison_t value.
 *
 * \param[in] cmpt  Comparison type to convert.
 * \returns   Pointer to a string that corresponds to \p cmpt.
 *
 * The return value points to a string constant and should not be \p free'd.
 *
 * The function returns NULL if \p cmpt is not one of the valid values.
 */
static const char* comparison_type_str(e_comparison_t cmpt)
{
    const char* p = nullptr;
    switch (cmpt)
    {
        case CMP_INVALID: p = "INVALID"; break;
        case CMP_LESS: p = "<"; break;
        case CMP_LEQ: p = "<="; break;
        case CMP_GTR: p = ">"; break;
        case CMP_GEQ: p = ">="; break;
        case CMP_EQUAL: p = "=="; break;
        case CMP_NEQ:
            p = "!=";
            break;
            // No default clause so we intentionally get compiler errors
            // if new selection choices are added later.
    }
    return p;
}

/*!
 * \param[in] fp    File to receive the output.
 * \param[in] data  Should point to a \c t_methoddata_compare.
 */
void _gmx_selelem_print_compare_info(FILE* fp, void* data)
{
    t_methoddata_compare* d = static_cast<t_methoddata_compare*>(data);

    fprintf(fp, " \"");
    /* Print the left value */
    if ((d->left.flags & CMP_SINGLEVAL) && !(d->left.flags & CMP_DYNAMICVAL))
    {
        if (d->left.flags & CMP_REALVAL)
        {
            fprintf(fp, "%f ", d->left.r[0]);
        }
        else
        {
            fprintf(fp, "%d ", d->left.i[0]);
        }
    }
    /* Print the operator */
    if (d->cmpt != CMP_INVALID)
    {
        fprintf(fp, "%s", comparison_type_str(d->cmpt));
    }
    else
    {
        fprintf(fp, "%s", d->cmpop);
    }
    /* Print the right value */
    if ((d->right.flags & CMP_SINGLEVAL) && !(d->right.flags & CMP_DYNAMICVAL))
    {
        if (d->right.flags & CMP_REALVAL)
        {
            fprintf(fp, " %f", d->right.r[0]);
        }
        else
        {
            fprintf(fp, " %d", d->right.i[0]);
        }
    }
    fprintf(fp, "\"");
}

static void* init_data_compare(int /* npar */, gmx_ana_selparam_t* param)
{
    t_methoddata_compare* data;

    snew(data, 1);
    param[2].val.u.s = &data->cmpop;
    return data;
}

/*! \brief
 * Reverses a comparison operator.
 *
 * \param[in] type  Comparison operator to reverse.
 * \returns   The correct comparison operator that equals \p type when the
 *   left and right sides are interchanged.
 */
static e_comparison_t reverse_comparison_type(e_comparison_t type)
{
    switch (type)
    {
        case CMP_LESS: return CMP_GTR;
        case CMP_LEQ: return CMP_GEQ;
        case CMP_GTR: return CMP_LESS;
        case CMP_GEQ: return CMP_LEQ;
        default: break;
    }
    return type;
}

/*! \brief
 * Initializes the value storage for comparison expression.
 *
 * \param[out] val   Value structure to initialize.
 * \param[in]  param Parameters to use for initialization.
 * \returns    The number of values provided for the value, 0 on error.
 */
static int init_comparison_value(t_compare_value* val, gmx_ana_selparam_t param[2])
{
    int n;

    val->flags = 0;
    if (param[0].flags & SPAR_SET)
    {
        val->flags |= (param[0].flags & SPAR_DYNAMIC) ? CMP_DYNAMICVAL : 0;
        val->flags |= !(param[0].flags & SPAR_ATOMVAL) ? CMP_SINGLEVAL : 0;
        n      = param[0].val.nr;
        val->i = param[0].val.u.i;
    }
    else if (param[1].flags & SPAR_SET)
    {
        val->flags |= (param[1].flags & SPAR_DYNAMIC) ? CMP_DYNAMICVAL : 0;
        val->flags |= !(param[1].flags & SPAR_ATOMVAL) ? CMP_SINGLEVAL : 0;
        val->flags |= CMP_REALVAL;
        n      = param[1].val.nr;
        val->r = param[1].val.u.r;
    }
    else
    {
        n      = 0;
        val->i = nullptr;
        val->r = nullptr;
    }
    return n;
}

/*! \brief
 * Converts an integer value to floating point.
 *
 * \param[in]     n   Number of values in the \p val->u array.
 * \param[in,out] val Value to convert.
 */
static void convert_int_real(int n, t_compare_value* val)
{
    int   i;
    real* rv;

    snew(rv, n);
    for (i = 0; i < n; ++i)
    {
        rv[i] = static_cast<real>(val->i[i]);
    }
    /* Free the previous value if one is present. */
    sfree(val->r);
    val->r = rv;
    val->flags |= CMP_REALVAL | CMP_ALLOCREAL;
}

/*! \brief
 * Converts a floating point value to integer.
 *
 * \param[in]     n      Number of values in the \p val->u array.
 * \param[in,out] val    Value to convert.
 * \param[in]     cmpt   Comparison operator type.
 * \param[in]     bRight true if \p val appears on the right hand size of
 *   \p cmpt.
 *
 * The values are rounded such that the same comparison operator can be used.
 */
static void convert_real_int(int n, t_compare_value* val, e_comparison_t cmpt, bool bRight)
{
    int  i;
    int* iv;

    if (!bRight)
    {
        cmpt = reverse_comparison_type(cmpt);
    }
    snew(iv, n);
    /* Round according to the comparison type */
    for (i = 0; i < n; ++i)
    {
        switch (cmpt)
        {
            case CMP_LESS:
            case CMP_GEQ: iv[i] = static_cast<int>(std::ceil(val->r[i])); break;
            case CMP_GTR:
            case CMP_LEQ: iv[i] = static_cast<int>(std::floor(val->r[i])); break;
            case CMP_EQUAL:
            case CMP_NEQ:
                sfree(iv);
                /* TODO: Implement, although it isn't typically very useful.
                 * Implementation is only a matter of proper initialization,
                 * the evaluation function can already handle this case with
                 * proper preparations. */
                GMX_THROW(
                        gmx::NotImplementedError("Equality comparison between dynamic integer and "
                                                 "static real expressions not implemented"));
            case CMP_INVALID: /* Should not be reached */
                sfree(iv);
                GMX_THROW(gmx::InternalError("Invalid comparison type"));
        }
    }
    /* Free the previous value if one is present. */
    sfree(val->i);
    val->i = iv;
    val->flags &= ~CMP_REALVAL;
    val->flags |= CMP_ALLOCINT;
}

static void init_compare(const gmx_mtop_t* /* top */, int /* npar */, gmx_ana_selparam_t* param, void* data)
{
    t_methoddata_compare* d = static_cast<t_methoddata_compare*>(data);
    int                   n1, n2;

    /* Store the values */
    n1 = init_comparison_value(&d->left, &param[0]);
    n2 = init_comparison_value(&d->right, &param[3]);
    /* Store the comparison type */
    d->cmpt = comparison_type(d->cmpop);
    if (d->cmpt == CMP_INVALID)
    {
        GMX_THROW(gmx::InternalError("Invalid comparison type"));
    }
    /* Convert the values to the same type */
    /* TODO: Currently, there are no dynamic integer-valued selection methods,
     * which means that only the branches with convert_int_real() will ever be
     * taken. It should be considered whether it is necessary to support these
     * other cases at all.
     */
    if ((d->left.flags & CMP_REALVAL) && !(d->right.flags & CMP_REALVAL))
    {
        if (d->left.flags & d->right.flags & CMP_DYNAMICVAL)
        {
            /* Nothing can be done */
        }
        else if (!(d->right.flags & CMP_DYNAMICVAL))
        {
            convert_int_real(n2, &d->right);
        }
        else /* d->left is static */
        {
            convert_real_int(n1, &d->left, d->cmpt, false);
        }
    }
    else if (!(d->left.flags & CMP_REALVAL) && (d->right.flags & CMP_REALVAL))
    {
        if (d->left.flags & d->right.flags & CMP_DYNAMICVAL)
        {
            /* Reverse the sides to place the integer on the right */
            int flags;
            d->left.r      = d->right.r;
            d->right.r     = nullptr;
            d->right.i     = d->left.i;
            d->left.i      = nullptr;
            flags          = d->left.flags;
            d->left.flags  = d->right.flags;
            d->right.flags = flags;
            d->cmpt        = reverse_comparison_type(d->cmpt);
        }
        else if (!(d->left.flags & CMP_DYNAMICVAL))
        {
            convert_int_real(n1, &d->left);
        }
        else /* d->right is static */
        {
            convert_real_int(n2, &d->right, d->cmpt, true);
        }
    }
}

/*!
 * \param data Data to free (should point to a \c t_methoddata_compare).
 *
 * Frees the memory allocated for \c t_methoddata_compare.
 */
static void free_data_compare(void* data)
{
    t_methoddata_compare* d = static_cast<t_methoddata_compare*>(data);

    sfree(d->cmpop);
    if (d->left.flags & CMP_ALLOCINT)
    {
        sfree(d->left.i);
    }
    if (d->left.flags & CMP_ALLOCREAL)
    {
        sfree(d->left.r);
    }
    if (d->right.flags & CMP_ALLOCINT)
    {
        sfree(d->right.i);
    }
    if (d->right.flags & CMP_ALLOCREAL)
    {
        sfree(d->right.r);
    }
    sfree(d);
}

/*! \brief
 * Implementation for evaluate_compare() for integer values.
 *
 * \param[in]  g     Evaluation index group.
 * \param[out] out   Output data structure (\p out->u.g is used).
 * \param[in]  data  Should point to a \c t_methoddata_compare.
 */
static void evaluate_compare_int(gmx_ana_index_t* g, gmx_ana_selvalue_t* out, void* data)
{
    t_methoddata_compare* d = static_cast<t_methoddata_compare*>(data);
    int                   i, i1, i2, ig;
    int                   a, b;
    bool                  bAccept;

    for (i = i1 = i2 = ig = 0; i < g->isize; ++i)
    {
        a       = d->left.i[i1];
        b       = d->right.i[i2];
        bAccept = false;
        switch (d->cmpt)
        {
            case CMP_INVALID: break;
            case CMP_LESS: bAccept = a < b; break;
            case CMP_LEQ: bAccept = a <= b; break;
            case CMP_GTR: bAccept = a > b; break;
            case CMP_GEQ: bAccept = a >= b; break;
            case CMP_EQUAL: bAccept = a == b; break;
            case CMP_NEQ: bAccept = a != b; break;
        }
        if (bAccept)
        {
            out->u.g->index[ig++] = g->index[i];
        }
        if (!(d->left.flags & CMP_SINGLEVAL))
        {
            ++i1;
        }
        if (!(d->right.flags & CMP_SINGLEVAL))
        {
            ++i2;
        }
    }
    out->u.g->isize = ig;
}

/*! \brief
 * Implementation for evaluate_compare() if either value is non-integer.
 *
 * \param[in]  g     Evaluation index group.
 * \param[out] out   Output data structure (\p out->u.g is used).
 * \param[in]  data  Should point to a \c t_methoddata_compare.
 *
 * Left value is assumed to be real-valued; right value can be either.
 * This is ensured by the initialization method.
 */
static void evaluate_compare_real(gmx_ana_index_t* g, gmx_ana_selvalue_t* out, void* data)
{
    t_methoddata_compare* d = static_cast<t_methoddata_compare*>(data);
    int                   i, i1, i2, ig;
    real                  a, b;
    bool                  bAccept;

    for (i = i1 = i2 = ig = 0; i < g->isize; ++i)
    {
        a       = d->left.r[i1];
        b       = (d->right.flags & CMP_REALVAL) ? d->right.r[i2] : d->right.i[i2];
        bAccept = false;
        switch (d->cmpt)
        {
            case CMP_INVALID: break;
            case CMP_LESS: bAccept = a < b; break;
            case CMP_LEQ: bAccept = a <= b; break;
            case CMP_GTR: bAccept = a > b; break;
            case CMP_GEQ: bAccept = a >= b; break;
            case CMP_EQUAL: bAccept = gmx_within_tol(a, b, GMX_REAL_EPS); break;
            case CMP_NEQ: bAccept = !gmx_within_tol(a, b, GMX_REAL_EPS); break;
        }
        if (bAccept)
        {
            out->u.g->index[ig++] = g->index[i];
        }
        if (!(d->left.flags & CMP_SINGLEVAL))
        {
            ++i1;
        }
        if (!(d->right.flags & CMP_SINGLEVAL))
        {
            ++i2;
        }
    }
    out->u.g->isize = ig;
}

static void evaluate_compare(const gmx::SelMethodEvalContext& /*context*/,
                             gmx_ana_index_t*    g,
                             gmx_ana_selvalue_t* out,
                             void*               data)
{
    t_methoddata_compare* d = static_cast<t_methoddata_compare*>(data);

    if (!((d->left.flags | d->right.flags) & CMP_REALVAL))
    {
        evaluate_compare_int(g, out, data);
    }
    else
    {
        evaluate_compare_real(g, out, data);
    }
}
