// Functions that operate on arrays

#include <ctype.h>
#include <err.h>
#include <gc.h>
#include <gc/cord.h>
#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/param.h>

#include "array.h"
#include "functions.h"
#include "halfsiphash.h"
#include "types.h"
#include "util.h"

static inline size_t get_item_size(const TypeInfo *info)
{
    return info->ArrayInfo.item->size;
}

// Replace the array's .data pointer with a new pointer to a copy of the
// data that is compacted and has a stride of exactly `item_size`
public void Array$compact(array_t *arr, const TypeInfo *type)
{
    void *copy = NULL;
    int64_t item_size = get_item_size(type);
    if (arr->length > 0) {
        copy = arr->atomic ? GC_MALLOC_ATOMIC(arr->length * item_size) : GC_MALLOC(arr->length * item_size);
        if ((int64_t)arr->stride == item_size) {
            memcpy(copy, arr->data, arr->length * item_size);
        } else {
            for (int64_t i = 0; i < arr->length; i++)
                memcpy(copy + i*item_size, arr->data + arr->stride*i, item_size);
        }
    }
    *arr = (array_t){
        .data=copy,
        .length=arr->length,
        .stride=item_size,
        .atomic=arr->atomic,
    };
}

public void Array$insert(array_t *arr, const void *item, int64_t index, const TypeInfo *type)
{
    if (index <= 0) index = arr->length + index + 1;

    if (index < 1) index = 1;
    else if (index > (int64_t)arr->length + 1) index = (int64_t)arr->length + 1;

    int64_t item_size = get_item_size(type);
    if (!arr->data) {
        arr->free = 4;
        arr->data = arr->atomic ? GC_MALLOC_ATOMIC(arr->free * item_size) : GC_MALLOC(arr->free * item_size);
        arr->stride = item_size;
    } else if (arr->free < 1 || arr->data_refcount || (int64_t)arr->stride != item_size) {
        arr->free = MAX(15, MIN(1, arr->length/4));
        void *copy = arr->atomic ? GC_MALLOC_ATOMIC((arr->length + arr->free) * item_size) : GC_MALLOC((arr->length + arr->free) * item_size);
        for (int64_t i = 0; i < index-1; i++)
            memcpy(copy + i*item_size, arr->data + arr->stride*i, item_size);
        for (int64_t i = index-1; i < (int64_t)arr->length; i++)
            memcpy(copy + (i+1)*item_size, arr->data + arr->stride*i, item_size);
        arr->data = copy;
        arr->data_refcount = 0;
        arr->stride = item_size;
    } else {
        if (index != arr->length+1)
            memmove((void*)arr->data + index*item_size, arr->data + (index-1)*item_size, (arr->length - index)*item_size);
    }
    assert(arr->free > 0);
    --arr->free;
    ++arr->length;
    memcpy((void*)arr->data + (index-1)*item_size, item, item_size);
}

public void Array$insert_all(array_t *arr, array_t to_insert, int64_t index, const TypeInfo *type)
{
    if (index < 1) index = arr->length + index + 1;

    if (index < 1) index = 1;
    else if (index > (int64_t)arr->length + 1) index = (int64_t)arr->length + 1;

    int64_t item_size = get_item_size(type);
    if (!arr->data) {
        arr->free = to_insert.length;
        arr->data = arr->atomic ? GC_MALLOC_ATOMIC(item_size*arr->free) : GC_MALLOC(item_size*arr->free);
    } else if ((int64_t)arr->free < (int64_t)to_insert.length || arr->data_refcount || (int64_t)arr->stride != item_size) {
        arr->free = to_insert.length;
        void *copy = arr->atomic ? GC_MALLOC_ATOMIC((arr->length + arr->free) * item_size) : GC_MALLOC((arr->length + arr->free) * item_size);
        for (int64_t i = 0; i < index-1; i++)
            memcpy(copy + i*item_size, arr->data + arr->stride*i, item_size);
        for (int64_t i = index-1; i < (int64_t)arr->length; i++)
            memcpy(copy + (i+to_insert.length)*item_size, arr->data + arr->stride*i, item_size);
        arr->data = copy;
        arr->data_refcount = 0;
    } else {
        if (index != arr->length+1)
            memmove((void*)arr->data + index*item_size, arr->data + (index-1)*item_size, (arr->length - index + to_insert.length-1)*item_size);
    }
    arr->free -= to_insert.length;
    arr->length += to_insert.length;
    for (int64_t i = 0; i < to_insert.length; i++)
        memcpy((void*)arr->data + (index-1 + i)*item_size, to_insert.data + i*to_insert.stride, item_size);
}

public void Array$remove(array_t *arr, int64_t index, int64_t count, const TypeInfo *type)
{
    if (index < 1) index = arr->length + index + 1;

    if (index < 1 || index > (int64_t)arr->length || count < 1) return;

    if (count > arr->length - index + 1)
        count = (arr->length - index) + 1;

    // TODO: optimize arr.remove(1) by just updating the .data and .length values

    int64_t item_size = get_item_size(type);
    if (index + count > arr->length) {
        if (arr->free >= 0)
            arr->free += count;
    } else if (arr->data_refcount || (int64_t)arr->stride != item_size) {
        void *copy = arr->atomic ? GC_MALLOC_ATOMIC((arr->length-1) * item_size) : GC_MALLOC((arr->length-1) * item_size);
        for (int64_t src = 1, dest = 1; src <= (int64_t)arr->length; src++) {
            if (src < index || src >= index + count) {
                memcpy(copy + (dest - 1)*item_size, arr->data + arr->stride*(src - 1), item_size);
                ++dest;
            }
        }
        arr->data = copy;
        arr->free = 0;
        arr->data_refcount = 0;
    } else {
        memmove((void*)arr->data + (index-1)*item_size, arr->data + (index-1 + count)*item_size, (arr->length - index + count - 1)*item_size);
        arr->free += count;
    }
    arr->length -= count;
}

public void Array$sort(array_t *arr, closure_t comparison, const TypeInfo *type)
{
    const TypeInfo *item_type = type->ArrayInfo.item;
    int64_t item_size = item_type->size;
    if (item_type->align > 1 && item_size % item_type->align)
        item_size += item_type->align - (item_size % item_type->align); // padding

    if (arr->data_refcount || (int64_t)arr->stride != item_size)
        Array$compact(arr, type);

    qsort_r(arr->data, arr->length, item_size, comparison.fn, comparison.userdata);
}

public array_t Array$sorted(array_t arr, closure_t comparison, const TypeInfo *type)
{
    arr.data_refcount = 3;
    Array$sort(&arr, comparison, type);
    return arr;
}

public void Array$shuffle(array_t *arr, const TypeInfo *type)
{
    int64_t item_size = get_item_size(type);
    if (arr->data_refcount || (int64_t)arr->stride != item_size)
        Array$compact(arr, type);

    char tmp[item_size];
    for (int64_t i = arr->length-1; i > 1; i--) {
        int32_t j = arc4random_uniform(i+1);
        memcpy(tmp, arr->data + i*item_size, item_size);
        memcpy((void*)arr->data + i*item_size, arr->data + j*item_size, item_size);
        memcpy((void*)arr->data + j*item_size, tmp, item_size);
    }
}

public void *Array$random(array_t arr)
{
    if (arr.length == 0)
        return NULL; // fail("Cannot get a random item from an empty array!");
    uint32_t index = arc4random_uniform(arr.length);
    return arr.data + arr.stride*index;
}

public array_t Array$sample(array_t arr, int64_t n, array_t weights, const TypeInfo *type)
{
    if (arr.length == 0 || n <= 0)
        return (array_t){};

    int64_t item_size = get_item_size(type);
    array_t selected = {
        .data=arr.atomic ? GC_MALLOC_ATOMIC(n * item_size) : GC_MALLOC(n * item_size),
        .length=n,
        .stride=item_size, .atomic=arr.atomic};

    double total = 0.0;
    for (int64_t i = 0; i < weights.length && i < arr.length; i++) {
        double weight = *(double*)(weights.data + weights.stride*i);
        if (isinf(weight))
            fail("Infinite weight!");
        else if (isnan(weight))
            fail("NaN weight!");
        else if (weight < 0.0)
            fail("Negative weight!");
        else
            total += weight;
    }

    if (isinf(total))
        fail("Sample weights have overflowed to infinity");

    if (total == 0.0) {
        for (int64_t i = 0; i < n; i++) {
            uint32_t index = arc4random_uniform(arr.length);
            memcpy(selected.data + i*item_size, arr.data + arr.stride*index, item_size);
        }
    } else {
        double inverse_average = (double)arr.length / total;

        struct {
            int64_t alias;
            double odds;
        } aliases[arr.length] = {};

        for (int64_t i = 0; i < arr.length; i++) {
            double weight = i >= weights.length ? 0.0 : *(double*)(weights.data + weights.stride*i);
            aliases[i].odds = weight * inverse_average;
            aliases[i].alias = -1;
        }

        int64_t small = 0;
        for (int64_t big = 0; big < arr.length; big++) {
            while (aliases[big].odds >= 1.0) {
                while (small < arr.length && (aliases[small].odds >= 1.0 || aliases[small].alias != -1))
                    ++small;

                if (small >= arr.length) {
                    aliases[big].odds = 1.0;
                    aliases[big].alias = big;
                    break;
                }

                aliases[small].alias = big;
                aliases[big].odds = (aliases[small].odds + aliases[big].odds) - 1.0;
            }
            if (big < small) small = big;
        }

        for (int64_t i = small; i < arr.length; i++)
            if (aliases[i].alias == -1)
                aliases[i].alias = i;

        for (int64_t i = 0; i < n; i++) {
            double r = drand48() * arr.length;
            int64_t index = (int64_t)r;
            if ((r - (double)index) > aliases[index].odds)
                index = aliases[index].alias;
            memcpy(selected.data + i*selected.stride, arr.data + index*arr.stride, item_size);
        }
    }
    return selected;
}

public array_t Array$slice(array_t *array, int64_t first, int64_t length, int64_t stride, const TypeInfo *type)
{
    if (stride > MAX_STRIDE || stride < MIN_STRIDE)
        fail("Stride is too big: %ld", stride);

    if (stride == 0 || length <= 0) {
        // Zero stride
        return (array_t){.atomic=array->atomic};
    } else if (stride < 0) {
        if (first == INT64_MIN) first = array->length;
        if (first > array->length) {
            // Range starting after array
            int64_t residual = first % -stride;
            first = array->length - (array->length % -stride) + residual;
        }
        if (first > array->length) first += stride;
        if (first < 1) {
            // Range outside array
            return (array_t){.atomic=array->atomic};
        }
    } else {
        if (first == INT64_MIN) first = 1;
        if (first < 1) {
            // Range starting before array
            first = first % stride;
        }
        while (first < 1) first += stride;
        if (first > array->length) {
            // Range outside array
            return (array_t){.atomic=array->atomic};
        }
    }

    if (length > array->length/labs(stride) + 1) length = array->length/labs(stride) + 1;
    if (length < 0) length = -length;

    // Saturating add:
    array->data_refcount |= (array->data_refcount << 1) | 1;

    int64_t item_size = get_item_size(type);
    return (array_t){
        .atomic=array->atomic,
        .data=array->data + item_size*(first-1),
        .length=length,
        .stride=(array->stride * stride),
        .data_refcount=array->data_refcount,
    };
}

public array_t Array$reversed(array_t array)
{
    array_t reversed = array;
    reversed.stride = -array.stride;
    reversed.data = array.data + (array.length-1)*array.stride;
    return reversed;
}

public array_t Array$concat(array_t x, array_t y, const TypeInfo *type)
{
    int64_t item_size = get_item_size(type);
    void *data = x.atomic ? GC_MALLOC_ATOMIC(item_size*(x.length + y.length)) : GC_MALLOC(item_size*(x.length + y.length));
    if (x.stride == item_size) {
        memcpy(data, x.data, item_size*x.length);
    } else {
        for (int64_t i = 0; i < x.length; i++)
            memcpy(data + i*item_size, x.data + i*item_size, item_size);
    }

    if (y.stride == item_size) {
        memcpy(data + item_size*x.length, y.data, item_size*y.length);
    } else {
        for (int64_t i = 0; i < x.length; i++)
            memcpy(data + (x.length + i)*item_size, y.data + i*item_size, item_size);
    }

    return (array_t){
        .data=data,
        .length=x.length + y.length,
        .stride=item_size,
        .atomic=x.atomic,
    };
}

public bool Array$contains(array_t array, void *item, const TypeInfo *type)
{
    const TypeInfo *item_type = type->ArrayInfo.item;
    for (int64_t i = 0; i < array.length; i++)
        if (generic_equal(array.data + i*array.stride, item, item_type))
            return true;
    return false;
}

public void Array$clear(array_t *array)
{
    *array = (array_t){.data=0, .length=0};
}

public int32_t Array$compare(const array_t *x, const array_t *y, const TypeInfo *type)
{
    // Early out for arrays with the same data, e.g. two copies of the same array:
    if (x->data == y->data && x->stride == y->stride)
        return (x->length > y->length) - (x->length < y->length);

    const TypeInfo *item = type->ArrayInfo.item;
    if (item->tag == PointerInfo || (item->tag == CustomInfo && item->CustomInfo.compare == NULL)) { // data comparison
        int64_t item_size = item->size;
        if (x->stride == (int32_t)item_size && y->stride == (int32_t)item_size) {
            int32_t cmp = (int32_t)memcmp(x->data, y->data, MIN(x->length, y->length)*item_size);
            if (cmp != 0) return cmp;
        } else {
            for (int32_t i = 0, len = MIN(x->length, y->length); i < len; i++) {
                int32_t cmp = (int32_t)memcmp(x->data+ x->stride*i, y->data + y->stride*i, item_size);
                if (cmp != 0) return cmp;
            }
        }
    } else {
        for (int32_t i = 0, len = MIN(x->length, y->length); i < len; i++) {
            int32_t cmp = generic_compare(x->data + x->stride*i, y->data + y->stride*i, item);
            if (cmp != 0) return cmp;
        }
    }
    return (x->length > y->length) - (x->length < y->length);
}

public bool Array$equal(const array_t *x, const array_t *y, const TypeInfo *type)
{
    return (Array$compare(x, y, type) == 0);
}

public CORD Array$as_text(const array_t *arr, bool colorize, const TypeInfo *type)
{
    if (!arr)
        return CORD_all("[", generic_as_text(NULL, false, type->ArrayInfo.item), "]");

    const TypeInfo *item_type = type->ArrayInfo.item;
    CORD c = "[";
    for (int64_t i = 0; i < arr->length; i++) {
        if (i > 0)
            c = CORD_cat(c, ", ");
        CORD item_cord = generic_as_text(arr->data + i*arr->stride, colorize, item_type);
        c = CORD_cat(c, item_cord);
    }
    c = CORD_cat(c, "]");
    return c;
}

public uint32_t Array$hash(const array_t *arr, const TypeInfo *type)
{
    // Array hash is calculated as a rolling, compacting hash of the length of the array, followed by
    // the hashes of its items (or the items themselves if they're small plain data)
    // In other words, it reads in a chunk of items or item hashes, then when it fills up the chunk,
    // hashes it down to a single item to start the next chunk. This repeats until the end, when it
    // hashes the last chunk down to a uint32_t.
    const TypeInfo *item = type->ArrayInfo.item;
    if (item->tag == PointerInfo || (item->tag == CustomInfo && item->CustomInfo.hash == NULL)) { // Raw data hash
        int64_t item_size = item->size;
        uint8_t hash_batch[4 + 8*item_size];
        memset(hash_batch, 0, sizeof(hash_batch));
        uint8_t *p = hash_batch, *end = hash_batch + sizeof(hash_batch);
        int64_t length = arr->length;
        *p = (uint32_t)length;
        p += sizeof(uint32_t);
        for (int64_t i = 0; i < arr->length; i++) {
            if (p >= end) {
                uint32_t chunk_hash;
                halfsiphash(&hash_batch, sizeof(hash_batch), TOMO_HASH_VECTOR, (uint8_t*)&chunk_hash, sizeof(chunk_hash));
                p = hash_batch;
                *(uint32_t*)p = chunk_hash;
                p += sizeof(uint32_t);
            }
            memcpy((p += item_size), arr->data + i*arr->stride, item_size);
        }
        uint32_t hash;
        halfsiphash(&hash_batch, ((int64_t)p) - ((int64_t)hash_batch), TOMO_HASH_VECTOR, (uint8_t*)&hash, sizeof(hash));
        return hash;
    } else {
        uint32_t hash_batch[16] = {(uint32_t)arr->length};
        uint32_t *p = &hash_batch[1], *end = hash_batch + sizeof(hash_batch)/sizeof(hash_batch[0]);
        for (int64_t i = 0; i < arr->length; i++) {
            if (p >= end) {
                uint64_t chunk_hash;
                halfsiphash(&hash_batch, sizeof(hash_batch), TOMO_HASH_VECTOR, (uint8_t*)&chunk_hash, sizeof(chunk_hash));
                p = hash_batch;
                *(p++) = chunk_hash;
            }
            *(p++) = generic_hash(arr->data + i*arr->stride, item);
        }
        uint32_t hash;
        halfsiphash(&hash_batch, ((int64_t)p) - ((int64_t)hash_batch), TOMO_HASH_VECTOR, (uint8_t*)&hash, sizeof(hash));
        return hash;
    }
}

static void siftdown(array_t *heap, int64_t startpos, int64_t pos, closure_t comparison, const TypeInfo *type)
{
    assert(pos > 0 && pos < heap->length);
    int64_t item_size = get_item_size(type);
    char newitem[item_size];
    memcpy(newitem, heap->data + heap->stride*pos, item_size);
    while (pos > startpos) {
        int64_t parentpos = (pos - 1) >> 1;
        typedef int32_t (*cmp_fn_t)(void*, void*, void*);
        int32_t cmp = ((cmp_fn_t)comparison.fn)(newitem, heap->data + heap->stride*parentpos, comparison.userdata);
        if (cmp >= 0)
            break;

        memcpy(heap->data + heap->stride*pos, heap->data + heap->stride*parentpos, item_size);
        pos = parentpos;
    }
    memcpy(heap->data + heap->stride*pos, newitem, item_size);
}

static void siftup(array_t *heap, int64_t pos, closure_t comparison, const TypeInfo *type)
{
    int64_t endpos = heap->length;
    int64_t startpos = pos;
    assert(pos < endpos);

    int64_t item_size = get_item_size(type);
    char old_top[item_size];
    memcpy(old_top, heap->data + heap->stride*pos, item_size);
    // Bubble up the smallest leaf node
    int64_t limit = endpos >> 1;
    while (pos < limit) {
        int64_t childpos = 2*pos + 1; // Smaller of the two child nodes
        if (childpos + 1 < endpos) {
            typedef int32_t (*cmp_fn_t)(void*, void*, void*);
            int32_t cmp = ((cmp_fn_t)comparison.fn)(
                heap->data + heap->stride*childpos,
                heap->data + heap->stride*(childpos + 1),
                comparison.userdata);
            childpos += (cmp >= 0);
        }

        // Move the child node up:
        memcpy(heap->data + heap->stride*pos, heap->data + heap->stride*childpos, item_size);
        pos = childpos;
    }
    memcpy(heap->data + heap->stride*pos, old_top, item_size);
    // Shift the node's parents down:
    siftdown(heap, startpos, pos, comparison, type);
}

public void Array$heap_push(array_t *heap, const void *item, closure_t comparison, const TypeInfo *type)
{
    Array$insert(heap, item, 0, type);

    if (heap->length > 1) {
        if (heap->data_refcount > 0)
            Array$compact(heap, type);
        siftdown(heap, 0, heap->length-1, comparison, type);
    }
}

public void Array$heap_pop(array_t *heap, void *out, closure_t comparison, const TypeInfo *type)
{
    if (heap->length == 0)
        fail("Attempt to pop from an empty array");

    int64_t item_size = get_item_size(type);
    memcpy(out, heap->data, item_size);
    if (heap->length == 1) {
        *heap = (array_t){};
    } else if (heap->length == 2) {
        heap->data += heap->stride;
        --heap->length;
    } else {
        if (heap->data_refcount > 0)
            Array$compact(heap, type);
        memcpy(heap->data, heap->data + heap->stride*(heap->length-1), item_size);
        --heap->length;
        siftup(heap, 0, comparison, type);
    }
}

public void Array$heapify(array_t *heap, closure_t comparison, const TypeInfo *type)
{
    if (heap->data_refcount > 0)
        Array$compact(heap, type);

    ARRAY_INCREF(*heap);
    int64_t i, n = heap->length;
    for (i = (n >> 1) - 1 ; i >= 0 ; i--)
        siftup(heap, i, comparison, type);
    ARRAY_DECREF(*heap);
}

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