/*
** Copyright (c) 2002-2021, Erik de Castro Lopo <erikd@mega-nerd.com>
** All rights reserved.
**
** This code is released under 2-clause BSD license. Please see the
** file at : https://github.com/libsndfile/libsamplerate/blob/master/COPYING
*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

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

#include "common.h"

static SRC_ERROR linear_vari_process (SRC_STATE *state, SRC_DATA *data) ;
static void linear_reset (SRC_STATE *state) ;
static SRC_STATE *linear_copy (SRC_STATE *state) ;
static void linear_close (SRC_STATE *state) ;

/*========================================================================================
*/

#define LINEAR_MAGIC_MARKER MAKE_MAGIC ('l', 'i', 'n', 'e', 'a', 'r')

#define SRC_DEBUG   0

typedef struct
{   int     linear_magic_marker ;
    bool    dirty ;
    long    in_count, in_used ;
    long    out_count, out_gen ;
    float   *last_value ;
} LINEAR_DATA ;

static SRC_STATE_VT linear_state_vt =
{
    linear_vari_process,
    linear_vari_process,
    linear_reset,
    linear_copy,
    linear_close
} ;

/*----------------------------------------------------------------------------------------
*/

static SRC_ERROR
linear_vari_process (SRC_STATE *state, SRC_DATA *data)
{   LINEAR_DATA *priv ;
    double      src_ratio, input_index, rem ;
    int         ch ;

    if (data->input_frames <= 0)
        return SRC_ERR_NO_ERROR ;

    if (state->private_data == NULL)
        return SRC_ERR_NO_PRIVATE ;

    priv = (LINEAR_DATA*) state->private_data ;

    if (!priv->dirty)
    {   /* If we have just been reset, set the last_value data. */
        for (ch = 0 ; ch < state->channels ; ch++)
            priv->last_value [ch] = data->data_in [ch] ;
        priv->dirty = true ;
        } ;

    priv->in_count = data->input_frames * state->channels ;
    priv->out_count = data->output_frames * state->channels ;
    priv->in_used = priv->out_gen = 0 ;

    src_ratio = state->last_ratio ;

    if (is_bad_src_ratio (src_ratio))
        return SRC_ERR_BAD_INTERNAL_STATE ;

    input_index = state->last_position ;

    /* Calculate samples before first sample in input array. */
    while (input_index < 1.0 && priv->out_gen < priv->out_count)
    {
        if (priv->in_used + state->channels * (1.0 + input_index) >= priv->in_count)
            break ;

        if (priv->out_count > 0 && fabs (state->last_ratio - data->src_ratio) > SRC_MIN_RATIO_DIFF)
            src_ratio = state->last_ratio + priv->out_gen * (data->src_ratio - state->last_ratio) / priv->out_count ;

        for (ch = 0 ; ch < state->channels ; ch++)
        {   data->data_out [priv->out_gen] = (float) (priv->last_value [ch] + input_index *
                                        ((double) data->data_in [ch] - priv->last_value [ch])) ;
            priv->out_gen ++ ;
            } ;

        /* Figure out the next index. */
        input_index += 1.0 / src_ratio ;
        } ;

    rem = fmod_one (input_index) ;
    priv->in_used += state->channels * psf_lrint (input_index - rem) ;
    input_index = rem ;

    /* Main processing loop. */
    while (priv->out_gen < priv->out_count && priv->in_used + state->channels * input_index < priv->in_count)
    {
        if (priv->out_count > 0 && fabs (state->last_ratio - data->src_ratio) > SRC_MIN_RATIO_DIFF)
            src_ratio = state->last_ratio + priv->out_gen * (data->src_ratio - state->last_ratio) / priv->out_count ;

#if SRC_DEBUG
        if (priv->in_used < state->channels && input_index < 1.0)
        {   printf ("Whoops!!!!   in_used : %ld     channels : %d     input_index : %f\n", priv->in_used, state->channels, input_index) ;
            exit (1) ;
            } ;
#endif

        for (ch = 0 ; ch < state->channels ; ch++)
        {   data->data_out [priv->out_gen] = (float) (data->data_in [priv->in_used - state->channels + ch] + input_index *
                        ((double) data->data_in [priv->in_used + ch] - data->data_in [priv->in_used - state->channels + ch])) ;
            priv->out_gen ++ ;
            } ;

        /* Figure out the next index. */
        input_index += 1.0 / src_ratio ;
        rem = fmod_one (input_index) ;

        priv->in_used += state->channels * psf_lrint (input_index - rem) ;
        input_index = rem ;
        } ;

    if (priv->in_used > priv->in_count)
    {   input_index += (priv->in_used - priv->in_count) / state->channels ;
        priv->in_used = priv->in_count ;
        } ;

    state->last_position = input_index ;

    if (priv->in_used > 0)
        for (ch = 0 ; ch < state->channels ; ch++)
            priv->last_value [ch] = data->data_in [priv->in_used - state->channels + ch] ;

    /* Save current ratio rather then target ratio. */
    state->last_ratio = src_ratio ;

    data->input_frames_used = priv->in_used / state->channels ;
    data->output_frames_gen = priv->out_gen / state->channels ;

    return SRC_ERR_NO_ERROR ;
} /* linear_vari_process */

/*------------------------------------------------------------------------------
*/

LIBSAMPLERATE_DLL_PRIVATE const char*
linear_get_name (int src_enum)
{
    if (src_enum == SRC_LINEAR)
        return "Linear Interpolator" ;

    return NULL ;
} /* linear_get_name */

LIBSAMPLERATE_DLL_PRIVATE const char*
linear_get_description (int src_enum)
{
    if (src_enum == SRC_LINEAR)
        return "Linear interpolator, very fast, poor quality." ;

    return NULL ;
} /* linear_get_descrition */

static LINEAR_DATA *
linear_data_new (int channels)
{
    assert (channels > 0) ;

    LINEAR_DATA *priv = (LINEAR_DATA *) calloc (1, sizeof (LINEAR_DATA)) ;
    if (priv)
    {
        priv->linear_magic_marker = LINEAR_MAGIC_MARKER ;
        priv->last_value = (float *) calloc (channels, sizeof (float)) ;
        if (!priv->last_value)
        {
            free (priv) ;
            priv = NULL ;
        }
    }

    return priv ;
}

LIBSAMPLERATE_DLL_PRIVATE SRC_STATE *
linear_state_new (int channels, SRC_ERROR *error)
{
    assert (channels > 0) ;
    assert (error != NULL) ;

    SRC_STATE *state = (SRC_STATE *) calloc (1, sizeof (SRC_STATE)) ;
    if (!state)
    {
        *error = SRC_ERR_MALLOC_FAILED ;
        return NULL ;
    }

    state->channels = channels ;
    state->mode = SRC_MODE_PROCESS ;

    state->private_data = linear_data_new (state->channels) ;
    if (!state->private_data)
    {
        free (state) ;
        *error = SRC_ERR_MALLOC_FAILED ;
        return NULL ;
    }

    state->vt = &linear_state_vt ;

    linear_reset (state) ;

    *error = SRC_ERR_NO_ERROR ;

    return state ;
}

/*===================================================================================
*/

static void
linear_reset (SRC_STATE *state)
{   LINEAR_DATA *priv = NULL ;

    priv = (LINEAR_DATA*) state->private_data ;
    if (priv == NULL)
        return ;

    priv->dirty = false ;
    memset (priv->last_value, 0, sizeof (priv->last_value [0]) * state->channels) ;

    return ;
} /* linear_reset */

SRC_STATE *
linear_copy (SRC_STATE *state)
{
    assert (state != NULL) ;

    if (state->private_data == NULL)
        return NULL ;

    SRC_STATE *to = (SRC_STATE *) calloc (1, sizeof (SRC_STATE)) ;
    if (!to)
        return NULL ;
    memcpy (to, state, sizeof (SRC_STATE)) ;

    LINEAR_DATA* from_priv = (LINEAR_DATA*) state->private_data ;
    LINEAR_DATA *to_priv = (LINEAR_DATA *) calloc (1, sizeof (LINEAR_DATA)) ;
    if (!to_priv)
    {
        free (to) ;
        return NULL ;
    }

    memcpy (to_priv, from_priv, sizeof (LINEAR_DATA)) ;
    to_priv->last_value = (float *) malloc (sizeof (float) * state->channels) ;
    if (!to_priv->last_value)
    {
        free (to) ;
        free (to_priv) ;
        return NULL ;
    }
    memcpy (to_priv->last_value, from_priv->last_value, sizeof (float) * state->channels) ;

    to->private_data = to_priv ;

    return to ;
} /* linear_copy */

static void
linear_close (SRC_STATE *state)
{
    if (state)
    {
        LINEAR_DATA *linear = (LINEAR_DATA *) state->private_data ;
        if (linear)
        {
            if (linear->last_value)
            {
                free (linear->last_value) ;
                linear->last_value = NULL ;
            }
            free (linear) ;
            linear = NULL ;
        }
        free (state) ;
        state = NULL ;
    }
} /* linear_close */
