#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <math.h>
#include <errno.h>

#include <xas/spatial.h>

static inline float dist(xas_spatial_coord a, xas_spatial_coord b) {
    return powf(powf(b.x - a.x, 2.0f)
              + powf(b.y - a.y, 2.0f)
              + powf(b.z - a.z, 2.0f), 0.5f);
}

static int buffer_realloc(xas_spatial_scene *scene,
                          xas_spatial_buffer *buffer) {
    float seconds = scene->radius / scene->speed;

    size_t sample_rate = scene->format.sample_rate,
           stride      = scene->format.channels * scene->format.sample_size,
           count       = sample_rate * ceilf(seconds),
           total       = sizeof(xas_spatial_buffer) + stride * count;

    if ((buffer = realloc(buffer, total)) == NULL) {
        goto error_realloc_buffer;
    }

    memset(buffer + 1, '\0', stride * count);

    scene->buffer        = buffer;
    scene->buffer->index = 0;
    scene->buffer->size  = count;

    return 0;

error_realloc_buffer:
    return -1;
}

static inline size_t sample_delta(xas_spatial_scene *scene, float distance) {
    return floorf(distance / scene->speed / scene->format.sample_rate);
}

static inline int16_t sample_scale(int16_t value, float distance) {
    return (int16_t)roundf((float)value * (1.0f / powf(distance, 2.0)));
}

static void buffer_zero(xas_spatial_buffer *buffer, size_t count) {
    int16_t *dest = (int16_t *)(buffer + 1);
    size_t i = buffer->index;

    if (count > buffer->size) {
        count = buffer->size;
    }

    while (count--) {
        if (i == buffer->size) {
            i = 0;
        }

        dest[XAS_AUDIO_STEREO*i]   = 0;
        dest[XAS_AUDIO_STEREO*i+1] = 0;

        i++;
    }
}

static void buffer_copy(xas_spatial_buffer *buffer,
                        int16_t *dest,
                        size_t count) {
    int16_t *src = (int16_t *)(buffer + 1);

    size_t i = buffer->index,
           o;

    if (count > buffer->size) {
        count = buffer->size;
    }

    for (o=0; o<count; o++) {
        if (i == buffer->size) {
            i = 0;
        }

        dest[XAS_AUDIO_STEREO*o]   = src[XAS_AUDIO_STEREO*i];
        dest[XAS_AUDIO_STEREO*o+1] = src[XAS_AUDIO_STEREO*i+1];

        i++;
    }
}

ssize_t scene_fill(xas_spatial_scene *scene,
                   int16_t *output,
                   size_t count,
                   xas_audio_stream *source) {
    xas_spatial_buffer *buffer = scene->buffer;
    xas_spatial_object *obj    = scene->first;

    size_t index_old = buffer->index;

    int16_t *dest = (int16_t *)(scene->buffer + 1);

    buffer_zero(buffer, count);

    while (obj) {
        int16_t *src;

        float distance_l = dist(scene->speaker_l, obj->coord),
              distance_r = dist(scene->speaker_r, obj->coord);

        size_t delta_l,
               delta_r;

        ssize_t readlen,
                i;

        if (distance_l > scene->radius || distance_r > scene->radius) {
            goto next;
        }

        if ((readlen = xas_audio_stream_read(obj->source,
                                               (void **)&src,
                                               count)) < 0) {
            goto error_audio_stream_read;
        }

        if (readlen > (ssize_t)buffer->size) {
            readlen = buffer->size;
        }

        delta_l = sample_delta(scene, distance_l);
        delta_r = sample_delta(scene, distance_r);

        for (i=0; i<readlen; i++) {
            int16_t value_l = sample_scale(src[i], distance_l),
                    value_r = sample_scale(src[i], distance_r);

            size_t index_l,
                   index_r;

            if (buffer->index == buffer->size) {
                buffer->index = 0;
            }

            index_l = buffer->index + delta_l;
            index_r = buffer->index + delta_r;

            dest[XAS_AUDIO_STEREO*index_l]   += value_l;
            dest[XAS_AUDIO_STEREO*index_r+1] += value_r;

            buffer->index++;
        }

next:
        buffer->index = index_old;
        obj           = obj->next;
    }

    buffer_copy(buffer, output, count);

    buffer->index  = index_old + count;
    buffer->index %= buffer->size;

    return count;

error_audio_stream_read:
    return -1;
}

xas_spatial_scene *xas_spatial_scene_new(xas_audio_format format,
                                             xas_spatial_coord speaker_l,
                                             xas_spatial_coord speaker_r) {
    xas_spatial_scene *scene;

    if ((scene = malloc(sizeof(*scene))) == NULL) {
        goto error_malloc_scene;
    }

    memset(scene, '\0', sizeof(*scene));

    scene->format    = format;
    scene->speaker_l = speaker_l;
    scene->speaker_r = speaker_r;
    scene->radius    = XAS_SPATIAL_DEFAULT_RADIUS;
    scene->speed     = XAS_SPATIAL_DEFAULT_SPEED;

    if (buffer_realloc(scene, NULL) < 0) {
        goto error_buffer_realloc;
    }

    return scene;

error_buffer_realloc:
    free(scene);

error_malloc_scene:
    return NULL;
}

void xas_spatial_scene_destroy(xas_spatial_scene *scene) {
    xas_spatial_object *object = scene->first;

    while (object) {
        xas_spatial_object *next = object->next;

        free(object);

        object = next;
    }

    free(scene->buffer);
    free(scene);
}


void xas_spatial_scene_set_observer(xas_spatial_scene *scene,
                                      xas_spatial_coord coord,
                                      xas_spatial_rotation rotation,
                                      float width) {
    scene->observer.coord    = coord;
    scene->observer.rotation = rotation;
    scene->observer.width    = width;
}

void xas_spatial_scene_set_speaker_coords(xas_spatial_scene *scene,
                                            xas_spatial_coord speaker_l,
                                            xas_spatial_coord speaker_r) {
    scene->speaker_l = speaker_l;
    scene->speaker_r = speaker_r;
}

int xas_spatial_scene_set_speed(xas_spatial_scene *scene, float speed) {
    scene->speed = speed;

    return buffer_realloc(scene, scene->buffer);
}

int xas_spatial_scene_set_radius(xas_spatial_scene *scene, float radius) {
    scene->radius = radius;

    return buffer_realloc(scene, scene->buffer);
}

xas_spatial_object *xas_spatial_scene_add_object(xas_spatial_scene *scene,
                                                     xas_spatial_coord coord,
                                                     xas_audio_stream *source) {
    xas_spatial_object *object;

    if (source->format.channels != XAS_AUDIO_MONO) {
        errno = EINVAL;

        goto error_invalid_source;
    }

    if ((object = malloc(sizeof(*object))) == NULL) {
        goto error_malloc_object;
    }

    object->coord  = coord;
    object->source = source;
    object->next   = NULL;

    if (scene->first == NULL) {
        scene->first = object;
    }

    if (scene->last) {
        scene->last->next = object;
    }

    scene->last = object;

    return object;

error_malloc_object:
error_invalid_source:
    return NULL;
}

void xas_spatial_object_get_coord(xas_spatial_object *object,
                                    xas_spatial_coord *coord) {
    coord->x = object->coord.x;
    coord->y = object->coord.y;
    coord->z = object->coord.z;
}

void xas_spatial_object_set_coord(xas_spatial_object *object,
                                    xas_spatial_coord coord) {
    object->coord = coord;
}

xas_audio_stream *xas_spatial_scene_new_stream(xas_spatial_scene *scene,
                                                   size_t buffer_size) {
    return xas_audio_stream_new_source((xas_audio_fill)scene_fill,
                                         NULL,
                                         scene->format,
                                         buffer_size,
                                         scene);
}