/*
 * Copyright (C) 2013 Martin Willi
 * Copyright (C) 2013 revosec AG
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 */

#include "array.h"

/**
 * Data is an allocated block, with potentially unused head and tail:
 *
 *   "esize" each (or sizeof(void*) if esize = 0)
 *  /-\ /-\ /-\ /-\ /-\ /-\
 *
 * +---------------+-------------------------------+---------------+
 * | h | e | a | d | e | l | e | m | e | n | t | s | t | a | i | l |
 * +---------------+-------------------------------+---------------+
 *
 * \--------------/ \-----------------------------/ \-------------/
 *      unused                    used                   unused
 *      "head"                   "count"                 "tail"
 *
 */
struct array_t {
	/** number of elements currently in array (not counting head/tail) */
	u_int32_t count;
	/** size of each element, 0 for a pointer based array */
	u_int16_t esize;
	/** allocated but unused elements at array front */
	u_int8_t head;
	/** allocated but unused elements at array end */
	u_int8_t tail;
	/** array elements */
	void *data;
};

/** maximum number of unused head/tail elements before cleanup */
#define ARRAY_MAX_UNUSED 32

/**
 * Get the actual size of a number of elements
 */
static size_t get_size(array_t *array, u_int32_t num)
{
	if (array->esize)
	{
		return array->esize * num;
	}
	return sizeof(void*) * num;
}

/**
 * Increase allocated but unused tail room to at least "room"
 */
static void make_tail_room(array_t *array, u_int8_t room)
{
	if (array->tail < room)
	{
		array->data = realloc(array->data,
						get_size(array, array->count + array->head + room));
		array->tail = room;
	}
}

/**
 * Increase allocated but unused head room to at least "room"
 */
static void make_head_room(array_t *array, u_int8_t room)
{
	if (array->head < room)
	{
		u_int8_t increase = room - array->head;

		array->data = realloc(array->data,
						get_size(array, array->count + array->tail + room));
		memmove(array->data + get_size(array, increase), array->data,
				get_size(array, array->count + array->tail + array->head));
		array->head = room;
	}
}

/**
 * Make space for an item at index using tail room
 */
static void insert_tail(array_t *array, int idx)
{
	make_tail_room(array, 1);
	/* move up all elements after idx by one */
	memmove(array->data + get_size(array, array->head + idx + 1),
			array->data + get_size(array, array->head + idx),
			get_size(array, array->count - idx));

	array->tail--;
	array->count++;
}

/**
 * Make space for an item at index using head room
 */
static void insert_head(array_t *array, int idx)
{
	make_head_room(array, 1);
	/* move down all elements before idx by one */
	memmove(array->data + get_size(array, array->head - 1),
			array->data + get_size(array, array->head),
			get_size(array, idx));

	array->head--;
	array->count++;
}

/**
 * Remove an item, increase tail
 */
static void remove_tail(array_t *array, int idx)
{
	/* move all items after idx one down */
	memmove(array->data + get_size(array, idx + array->head),
			array->data + get_size(array, idx + array->head + 1),
			get_size(array, array->count - idx));
	array->count--;
	array->tail++;
}

/**
 * Remove an item, increase head
 */
static void remove_head(array_t *array, int idx)
{
	/* move all items before idx one up */
	memmove(array->data + get_size(array, array->head + 1),
			array->data + get_size(array, array->head), get_size(array, idx));
	array->count--;
	array->head++;
}

array_t *array_create(u_int esize, u_int8_t reserve)
{
	array_t *array;

	INIT(array,
		.esize = esize,
		.tail = reserve,
	);
	if (array->tail)
	{
		array->data = malloc(array->tail * array->esize);
	}
	return array;
}

int array_count(array_t *array)
{
	if (array)
	{
		return array->count;
	}
	return 0;
}

void array_compress(array_t *array)
{
	if (array)
	{
		u_int32_t tail;

		tail = array->tail;
		if (array->head)
		{
			memmove(array->data, array->data + get_size(array, array->head),
					get_size(array, array->count + array->tail));
			tail += array->head;
			array->head = 0;
		}
		if (tail)
		{
			array->data = realloc(array->data, get_size(array, array->count));
			array->tail = 0;
		}
	}
}

typedef struct {
	/** public enumerator interface */
	enumerator_t public;
	/** enumerated array */
	array_t *array;
	/** current index +1, initialized at 0 */
	int idx;
} array_enumerator_t;

METHOD(enumerator_t, enumerate, bool,
	array_enumerator_t *this, void **out)
{
	void *pos;

	if (this->idx >= this->array->count)
	{
		return FALSE;
	}

	pos = this->array->data +
		  get_size(this->array, this->idx + this->array->head);
	if (this->array->esize)
	{
		/* for element based arrays we return a pointer to the element */
		*out = pos;
	}
	else
	{
		/* for pointer based arrays we return the pointer directly */
		*out = *(void**)pos;
	}
	this->idx++;
	return TRUE;
}

enumerator_t* array_create_enumerator(array_t *array)
{
	array_enumerator_t *enumerator;

	if (!array)
	{
		return enumerator_create_empty();
	}

	INIT(enumerator,
		.public = {
			.enumerate = (void*)_enumerate,
			.destroy = (void*)free,
		},
		.array = array,
	);
	return &enumerator->public;
}

void array_remove_at(array_t *array, enumerator_t *public)
{
	array_enumerator_t *enumerator = (array_enumerator_t*)public;

	if (enumerator->idx)
	{
		array_remove(array, --enumerator->idx, NULL);
	}
}

void array_insert_create(array_t **array, int idx, void *ptr)
{
	if (*array == NULL)
	{
		*array = array_create(0, 0);
	}
	array_insert(*array, idx, ptr);
}

void array_insert_enumerator(array_t *array, int idx, enumerator_t *enumerator)
{
	void *ptr;

	while (enumerator->enumerate(enumerator, &ptr))
	{
		array_insert(array, idx, ptr);
	}
	enumerator->destroy(enumerator);
}

void array_insert(array_t *array, int idx, void *data)
{
	if (idx < 0 || idx <= array_count(array))
	{
		void *pos;

		if (idx < 0)
		{
			idx = array_count(array);
		}

		if (array->head && !array->tail)
		{
			insert_head(array, idx);
		}
		else if (array->tail && !array->head)
		{
			insert_tail(array, idx);
		}
		else if (idx > array_count(array) / 2)
		{
			insert_tail(array, idx);
		}
		else
		{
			insert_head(array, idx);
		}

		pos = array->data + get_size(array, array->head + idx);
		if (array->esize)
		{
			memcpy(pos, data, get_size(array, 1));
		}
		else
		{
			/* pointer based array, copy pointer value */
			*(void**)pos = data;
		}
	}
}

bool array_remove(array_t *array, int idx, void *data)
{
	if (!array)
	{
		return FALSE;
	}
	if (idx >= 0 && idx >= array_count(array))
	{
		return FALSE;
	}
	if (idx < 0)
	{
		if (array_count(array) == 0)
		{
			return FALSE;
		}
		idx = array_count(array) - 1;
	}
	if (data)
	{
		memcpy(data, array->data + get_size(array, array->head + idx),
			   get_size(array, 1));
	}
	if (idx > array_count(array) / 2)
	{
		remove_tail(array, idx);
	}
	else
	{
		remove_head(array, idx);
	}
	if (array->head + array->tail > ARRAY_MAX_UNUSED)
	{
		array_compress(array);
	}
	return TRUE;
}

void array_invoke(array_t *array, array_callback_t cb, void *user)
{
	if (array)
	{
		void *obj;
		int i;

		for (i = array->head; i < array->count + array->head; i++)
		{
			obj = array->data + get_size(array, i);
			if (!array->esize)
			{
				/* dereference if we store store pointers */
				obj = *(void**)obj;
			}
			cb(obj, i - array->head, user);
		}
	}
}

void array_invoke_offset(array_t *array, size_t offset)
{
	if (array)
	{
		void (*method)(void *data);
		void *obj;
		int i;

		for (i = array->head; i < array->count + array->head; i++)
		{
			obj = array->data + get_size(array, i);
			if (!array->esize)
			{
				/* dereference if we store store pointers */
				obj = *(void**)obj;
			}
			method = *(void**)(obj + offset);
			method(obj);
		}
	}
}

void array_destroy(array_t *array)
{
	if (array)
	{
		free(array->data);
		free(array);
	}
}

void array_destroy_function(array_t *array, array_callback_t cb, void *user)
{
	array_invoke(array, cb, user);
	array_destroy(array);
}

void array_destroy_offset(array_t *array, size_t offset)
{
	array_invoke_offset(array, offset);
	array_destroy(array);
}