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#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

/* NLSF stabilizer:                                         */

/*                                                          */

/* - Moves NLSFs further apart if they are too close        */

/* - Moves NLSFs away from borders if they are too close    */

/* - High effort to achieve a modification with minimum     */

/*     Euclidean distance to input vector                   */

/* - Output are sorted NLSF coefficients                    */

/*                                                          */

#include "SigProc_FIX.h"

/* Constant Definitions */

#define MAX_LOOPS        20

/* NLSF stabilizer, for a single input data vector */

void silk_NLSF_stabilize(

          opus_int16            *NLSF_Q15,          /* I/O   Unstable/stabilized normalized LSF vector in Q15 [L]       */

    const opus_int16            *NDeltaMin_Q15,     /* I     Min distance vector, NDeltaMin_Q15[L] must be >= 1 [L+1]   */

    const opus_int              L                   /* I     Number of NLSF parameters in the input vector              */

)

{

    opus_int   i, I=0, k, loops;

    opus_int16 center_freq_Q15;

    opus_int32 diff_Q15, min_diff_Q15, min_center_Q15, max_center_Q15;

    /* This is necessary to ensure an output within range of a opus_int16 */

    silk_assert( NDeltaMin_Q15[L] >= 1 );

    for( loops = 0; loops < MAX_LOOPS; loops++ ) {

        /**************************/

        /* Find smallest distance */

        /**************************/

        /* First element */

        min_diff_Q15 = NLSF_Q15[0] - NDeltaMin_Q15[0];

        I = 0;

        /* Middle elements */

        for( i = 1; i <= L-1; i++ ) {

            diff_Q15 = NLSF_Q15[i] - ( NLSF_Q15[i-1] + NDeltaMin_Q15[i] );

            if( diff_Q15 < min_diff_Q15 ) {

                min_diff_Q15 = diff_Q15;

                I = i;

            }

        }

        /* Last element */

        diff_Q15 = ( 1 << 15 ) - ( NLSF_Q15[L-1] + NDeltaMin_Q15[L] );

        if( diff_Q15 < min_diff_Q15 ) {

            min_diff_Q15 = diff_Q15;

            I = L;

        }

        /***************************************************/

        /* Now check if the smallest distance non-negative */

        /***************************************************/

        if( min_diff_Q15 >= 0 ) {

            return;

        }

        if( I == 0 ) {

            /* Move away from lower limit */

            NLSF_Q15[0] = NDeltaMin_Q15[0];

        } else if( I == L) {

            /* Move away from higher limit */

            NLSF_Q15[L-1] = ( 1 << 15 ) - NDeltaMin_Q15[L];

        } else {

            /* Find the lower extreme for the location of the current center frequency */

            min_center_Q15 = 0;

            for( k = 0; k < I; k++ ) {

                min_center_Q15 += NDeltaMin_Q15[k];

            }

            min_center_Q15 += silk_RSHIFT( NDeltaMin_Q15[I], 1 );

            /* Find the upper extreme for the location of the current center frequency */

            max_center_Q15 = 1 << 15;

            for( k = L; k > I; k-- ) {

                max_center_Q15 -= NDeltaMin_Q15[k];

            }

            max_center_Q15 -= silk_RSHIFT( NDeltaMin_Q15[I], 1 );

            /* Move apart, sorted by value, keeping the same center frequency */

            center_freq_Q15 = (opus_int16)silk_LIMIT_32( silk_RSHIFT_ROUND( (opus_int32)NLSF_Q15[I-1] + (opus_int32)NLSF_Q15[I], 1 ),

                min_center_Q15, max_center_Q15 );

            NLSF_Q15[I-1] = center_freq_Q15 - silk_RSHIFT( NDeltaMin_Q15[I], 1 );

            NLSF_Q15[I] = NLSF_Q15[I-1] + NDeltaMin_Q15[I];

        }

    }

    /* Safe and simple fall back method, which is less ideal than the above */

    if( loops == MAX_LOOPS )

    {

        /* Insertion sort (fast for already almost sorted arrays):   */

        /* Best case:  O(n)   for an already sorted array            */

        /* Worst case: O(n^2) for an inversely sorted array          */

        silk_insertion_sort_increasing_all_values_int16( &NLSF_Q15[0], L );

        /* First NLSF should be no less than NDeltaMin[0] */

        NLSF_Q15[0] = silk_max_int( NLSF_Q15[0], NDeltaMin_Q15[0] );

        /* Keep delta_min distance between the NLSFs */

        for( i = 1; i < L; i++ )

            NLSF_Q15[i] = silk_max_int( NLSF_Q15[i], silk_ADD_SAT16( NLSF_Q15[i-1], NDeltaMin_Q15[i] ) );

        /* Last NLSF should be no higher than 1 - NDeltaMin[L] */

        NLSF_Q15[L-1] = silk_min_int( NLSF_Q15[L-1], (1<<15) - NDeltaMin_Q15[L] );

        /* Keep NDeltaMin distance between the NLSFs */

        for( i = L-2; i >= 0; i-- )

            NLSF_Q15[i] = silk_min_int( NLSF_Q15[i], NLSF_Q15[i+1] - NDeltaMin_Q15[i+1] );

    }

}