/*
 * Copyright (c) 2018 Jiri Svoboda
 * Copyright (c) 2012 Frantisek Princ
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup libext4
 * @{
 */
/**
 * @file  balloc.c
 * @brief Physical block allocator.
 */

#include <errno.h>
#include <stdbool.h>
#include <stdint.h>
#include "ext4/balloc.h"
#include "ext4/bitmap.h"
#include "ext4/block_group.h"
#include "ext4/filesystem.h"
#include "ext4/inode.h"
#include "ext4/superblock.h"
#include "ext4/types.h"

/** Free block.
 *
 * @param inode_ref  Inode, where the block is allocated
 * @param block_addr Absolute block address to free
 *
 * @return Error code
 *
 */
errno_t ext4_balloc_free_block(ext4_inode_ref_t *inode_ref, uint32_t block_addr)
{
	ext4_filesystem_t *fs = inode_ref->fs;
	ext4_superblock_t *sb = fs->superblock;

	/* Compute indexes */
	uint32_t block_group = ext4_filesystem_blockaddr2group(sb, block_addr);
	uint32_t index_in_group =
	    ext4_filesystem_blockaddr2_index_in_group(sb, block_addr);

	/* Load block group reference */
	ext4_block_group_ref_t *bg_ref;
	errno_t rc = ext4_filesystem_get_block_group_ref(fs, block_group, &bg_ref);
	if (rc != EOK)
		return rc;

	/* Load block with bitmap */
	uint32_t bitmap_block_addr =
	    ext4_block_group_get_block_bitmap(bg_ref->block_group, sb);
	block_t *bitmap_block;
	rc = block_get(&bitmap_block, fs->device, bitmap_block_addr, 0);
	if (rc != EOK) {
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	/* Modify bitmap */
	ext4_bitmap_free_bit(bitmap_block->data, index_in_group);
	bitmap_block->dirty = true;

	/* Release block with bitmap */
	rc = block_put(bitmap_block);
	if (rc != EOK) {
		/* Error in saving bitmap */
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	uint32_t block_size = ext4_superblock_get_block_size(sb);

	/* Update superblock free blocks count */
	uint32_t sb_free_blocks =
	    ext4_superblock_get_free_blocks_count(sb);
	sb_free_blocks++;
	ext4_superblock_set_free_blocks_count(sb, sb_free_blocks);

	/* Update inode blocks count */
	uint64_t ino_blocks =
	    ext4_inode_get_blocks_count(sb, inode_ref->inode);
	ino_blocks -= block_size / EXT4_INODE_BLOCK_SIZE;
	ext4_inode_set_blocks_count(sb, inode_ref->inode, ino_blocks);
	inode_ref->dirty = true;

	/* Update block group free blocks count */
	uint32_t free_blocks =
	    ext4_block_group_get_free_blocks_count(bg_ref->block_group, sb);
	free_blocks++;
	ext4_block_group_set_free_blocks_count(bg_ref->block_group,
	    sb, free_blocks);
	bg_ref->dirty = true;

	/* Release block group reference */
	return ext4_filesystem_put_block_group_ref(bg_ref);
}

static errno_t ext4_balloc_free_blocks_internal(ext4_inode_ref_t *inode_ref,
    uint32_t first, uint32_t count)
{
	ext4_filesystem_t *fs = inode_ref->fs;
	ext4_superblock_t *sb = fs->superblock;

	/* Compute indexes */
	uint32_t block_group_first = ext4_filesystem_blockaddr2group(sb,
	    first);
	uint32_t block_group_last = ext4_filesystem_blockaddr2group(sb,
	    first + count - 1);

	assert(block_group_first == block_group_last);

	/* Load block group reference */
	ext4_block_group_ref_t *bg_ref;
	errno_t rc = ext4_filesystem_get_block_group_ref(fs, block_group_first, &bg_ref);
	if (rc != EOK)
		return rc;

	uint32_t index_in_group_first =
	    ext4_filesystem_blockaddr2_index_in_group(sb, first);

	/* Load block with bitmap */
	uint32_t bitmap_block_addr =
	    ext4_block_group_get_block_bitmap(bg_ref->block_group, sb);

	block_t *bitmap_block;
	rc = block_get(&bitmap_block, fs->device, bitmap_block_addr, 0);
	if (rc != EOK) {
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	/* Modify bitmap */
	ext4_bitmap_free_bits(bitmap_block->data, index_in_group_first, count);
	bitmap_block->dirty = true;

	/* Release block with bitmap */
	rc = block_put(bitmap_block);
	if (rc != EOK) {
		/* Error in saving bitmap */
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	uint32_t block_size = ext4_superblock_get_block_size(sb);

	/* Update superblock free blocks count */
	uint32_t sb_free_blocks =
	    ext4_superblock_get_free_blocks_count(sb);
	sb_free_blocks += count;
	ext4_superblock_set_free_blocks_count(sb, sb_free_blocks);

	/* Update inode blocks count */
	uint64_t ino_blocks =
	    ext4_inode_get_blocks_count(sb, inode_ref->inode);
	ino_blocks -= count * (block_size / EXT4_INODE_BLOCK_SIZE);
	ext4_inode_set_blocks_count(sb, inode_ref->inode, ino_blocks);
	inode_ref->dirty = true;

	/* Update block group free blocks count */
	uint32_t free_blocks =
	    ext4_block_group_get_free_blocks_count(bg_ref->block_group, sb);
	free_blocks += count;
	ext4_block_group_set_free_blocks_count(bg_ref->block_group,
	    sb, free_blocks);
	bg_ref->dirty = true;

	/* Release block group reference */
	return ext4_filesystem_put_block_group_ref(bg_ref);
}

/** Free continuous set of blocks.
 *
 * @param inode_ref Inode, where the blocks are allocated
 * @param first     First block to release
 * @param count     Number of blocks to release
 *
 */
errno_t ext4_balloc_free_blocks(ext4_inode_ref_t *inode_ref,
    uint32_t first, uint32_t count)
{
	errno_t r;
	uint32_t gid;
	uint64_t limit;
	ext4_filesystem_t *fs = inode_ref->fs;
	ext4_superblock_t *sb = fs->superblock;

	while (count) {
		gid = ext4_filesystem_blockaddr2group(sb, first);
		limit = ext4_filesystem_index_in_group2blockaddr(sb, 0,
		    gid + 1);

		if ((first + count) >= limit) {
			/*
			 * This extent spans over 2 or more block groups,
			 * we'll break it into smaller parts.
			 */
			uint32_t s = limit - first;

			r = ext4_balloc_free_blocks_internal(inode_ref,
			    first, s);
			if (r != EOK)
				return r;

			first = limit;
			count -= s;
		} else {
			return ext4_balloc_free_blocks_internal(inode_ref,
			    first, count);
		}
	}

	return EOK;
}

/** Compute first block for data in block group.
 *
 * @param sb   Pointer to superblock
 * @param bg   Pointer to block group
 * @param bgid Index of block group
 *
 * @return Absolute block index of first block
 *
 */
uint32_t ext4_balloc_get_first_data_block_in_group(ext4_superblock_t *sb,
    ext4_block_group_ref_t *bg_ref)
{
	uint32_t r;
	uint64_t itable = ext4_block_group_get_inode_table_first_block(
	    bg_ref->block_group, sb);
	uint32_t itable_sz = ext4_filesystem_bg_get_itable_size(sb,
	    bg_ref->index);

	if (!ext4_superblock_has_feature_incompatible(sb,
	    EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
		/*
		 * If we are not using FLEX_BG, the first data block
		 * is always after the inode table.
		 */
		return itable + itable_sz;
	}

	uint32_t flex_group_size = ext4_superblock_get_flex_group_size(sb);
	if ((bg_ref->index % flex_group_size) == 0) {
		/* This is the base group */
		uint32_t i;

		r = itable + itable_sz;

		uint32_t total_groups = ext4_superblock_get_block_group_count(sb);
		for (i = bg_ref->index + 1;
		    i < min(total_groups, bg_ref->index + flex_group_size); ++i) {
			r += ext4_filesystem_bg_get_itable_size(sb, i);
		}

		return r;
	}

	uint64_t base_addr = ext4_filesystem_index_in_group2blockaddr(sb, 0,
	    bg_ref->index);
	uint32_t reserved = ext4_filesystem_bg_get_backup_blocks(bg_ref);

	return base_addr + reserved;
}

/** Compute 'goal' for allocation algorithm.
 *
 * @param inode_ref Reference to inode, to allocate block for
 *
 * @return Goal block number
 *
 */
static errno_t ext4_balloc_find_goal(ext4_inode_ref_t *inode_ref, uint32_t *goal)
{
	*goal = 0;
	ext4_superblock_t *sb = inode_ref->fs->superblock;

	uint64_t inode_size = ext4_inode_get_size(sb, inode_ref->inode);
	uint32_t block_size = ext4_superblock_get_block_size(sb);
	uint32_t inode_block_count = inode_size / block_size;

	if (inode_size % block_size != 0)
		inode_block_count++;

	/* If inode has some blocks, get last block address + 1 */
	if (inode_block_count > 0) {
		errno_t rc = ext4_filesystem_get_inode_data_block_index(inode_ref,
		    inode_block_count - 1, goal);
		if (rc != EOK)
			return rc;

		if (goal != 0) {
			(*goal)++;
			return EOK;
		}
		/* If goal == 0, sparse file -> continue */
	}

	/* Identify block group of inode */
	uint32_t inodes_per_group = ext4_superblock_get_inodes_per_group(sb);
	uint32_t block_group = (inode_ref->index - 1) / inodes_per_group;

	/* Load block group reference */
	ext4_block_group_ref_t *bg_ref;
	errno_t rc = ext4_filesystem_get_block_group_ref(inode_ref->fs,
	    block_group, &bg_ref);
	if (rc != EOK)
		return rc;

	*goal = ext4_balloc_get_first_data_block_in_group(sb, bg_ref);

	return ext4_filesystem_put_block_group_ref(bg_ref);
}

/** Data block allocation algorithm.
 *
 * @param inode_ref Inode to allocate block for
 * @param fblock    Allocated block address
 *
 * @return Error code
 *
 */
errno_t ext4_balloc_alloc_block(ext4_inode_ref_t *inode_ref, uint32_t *fblock)
{
	uint32_t allocated_block = 0;

	uint32_t bitmap_block_addr;
	block_t *bitmap_block;
	uint32_t rel_block_idx = 0;
	uint32_t free_blocks;
	uint32_t goal;
	uint32_t block_size;

	/* Find GOAL */
	errno_t rc = ext4_balloc_find_goal(inode_ref, &goal);
	if (rc != EOK)
		return rc;

	ext4_superblock_t *sb = inode_ref->fs->superblock;

	/* Load block group number for goal and relative index */
	uint32_t block_group = ext4_filesystem_blockaddr2group(sb, goal);
	uint32_t index_in_group =
	    ext4_filesystem_blockaddr2_index_in_group(sb, goal);

	/* Load block group reference */
	ext4_block_group_ref_t *bg_ref;
	rc = ext4_filesystem_get_block_group_ref(inode_ref->fs,
	    block_group, &bg_ref);
	if (rc != EOK)
		return rc;

	free_blocks =
	    ext4_block_group_get_free_blocks_count(bg_ref->block_group, sb);
	if (free_blocks == 0) {
		/* This group has no free blocks */
		goto goal_failed;
	}

	/* Compute indexes */
	uint32_t first_in_group =
	    ext4_balloc_get_first_data_block_in_group(sb, bg_ref);

	uint32_t first_in_group_index =
	    ext4_filesystem_blockaddr2_index_in_group(sb, first_in_group);

	if (index_in_group < first_in_group_index)
		index_in_group = first_in_group_index;

	/* Load block with bitmap */
	bitmap_block_addr =
	    ext4_block_group_get_block_bitmap(bg_ref->block_group, sb);

	rc = block_get(&bitmap_block, inode_ref->fs->device,
	    bitmap_block_addr, BLOCK_FLAGS_NONE);
	if (rc != EOK) {
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	/* Check if goal is free */
	if (ext4_bitmap_is_free_bit(bitmap_block->data, index_in_group)) {
		ext4_bitmap_set_bit(bitmap_block->data, index_in_group);
		bitmap_block->dirty = true;
		rc = block_put(bitmap_block);
		if (rc != EOK) {
			ext4_filesystem_put_block_group_ref(bg_ref);
			return rc;
		}

		allocated_block =
		    ext4_filesystem_index_in_group2blockaddr(sb, index_in_group,
		    block_group);

		goto success;
	}

	uint32_t blocks_in_group =
	    ext4_superblock_get_blocks_in_group(sb, block_group);

	uint32_t end_idx = (index_in_group + 63) & ~63;
	if (end_idx > blocks_in_group)
		end_idx = blocks_in_group;

	/* Try to find free block near to goal */
	for (uint32_t tmp_idx = index_in_group + 1; tmp_idx < end_idx;
	    ++tmp_idx) {
		if (ext4_bitmap_is_free_bit(bitmap_block->data, tmp_idx)) {
			ext4_bitmap_set_bit(bitmap_block->data, tmp_idx);
			bitmap_block->dirty = true;
			rc = block_put(bitmap_block);
			if (rc != EOK)
				return rc;

			allocated_block =
			    ext4_filesystem_index_in_group2blockaddr(sb, tmp_idx,
			    block_group);

			goto success;
		}
	}

	/* Find free BYTE in bitmap */
	rc = ext4_bitmap_find_free_byte_and_set_bit(bitmap_block->data,
	    index_in_group, &rel_block_idx, blocks_in_group);
	if (rc == EOK) {
		bitmap_block->dirty = true;
		rc = block_put(bitmap_block);
		if (rc != EOK)
			return rc;

		allocated_block =
		    ext4_filesystem_index_in_group2blockaddr(sb, rel_block_idx,
		    block_group);

		goto success;
	}

	/* Find free bit in bitmap */
	rc = ext4_bitmap_find_free_bit_and_set(bitmap_block->data,
	    index_in_group, &rel_block_idx, blocks_in_group);
	if (rc == EOK) {
		bitmap_block->dirty = true;
		rc = block_put(bitmap_block);
		if (rc != EOK)
			return rc;

		allocated_block =
		    ext4_filesystem_index_in_group2blockaddr(sb, rel_block_idx,
		    block_group);

		goto success;
	}

	/* No free block found yet */
	rc = block_put(bitmap_block);
	if (rc != EOK) {
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

goal_failed:

	rc = ext4_filesystem_put_block_group_ref(bg_ref);
	if (rc != EOK)
		return rc;

	/* Try other block groups */
	uint32_t block_group_count = ext4_superblock_get_block_group_count(sb);

	uint32_t bgid = (block_group + 1) % block_group_count;
	uint32_t count = block_group_count;

	while (count > 0) {
		rc = ext4_filesystem_get_block_group_ref(inode_ref->fs, bgid,
		    &bg_ref);
		if (rc != EOK)
			return rc;

		free_blocks =
		    ext4_block_group_get_free_blocks_count(bg_ref->block_group, sb);
		if (free_blocks == 0) {
			/* This group has no free blocks */
			goto next_group;
		}

		/* Load block with bitmap */
		bitmap_block_addr =
		    ext4_block_group_get_block_bitmap(bg_ref->block_group, sb);

		rc = block_get(&bitmap_block, inode_ref->fs->device,
		    bitmap_block_addr, 0);
		if (rc != EOK) {
			ext4_filesystem_put_block_group_ref(bg_ref);
			return rc;
		}

		/* Compute indexes */
		first_in_group =
		    ext4_balloc_get_first_data_block_in_group(sb, bg_ref);
		index_in_group =
		    ext4_filesystem_blockaddr2_index_in_group(sb, first_in_group);
		blocks_in_group = ext4_superblock_get_blocks_in_group(sb, bgid);

		first_in_group_index =
		    ext4_filesystem_blockaddr2_index_in_group(sb, first_in_group);

		if (index_in_group < first_in_group_index)
			index_in_group = first_in_group_index;

		/* Try to find free byte in bitmap */
		rc = ext4_bitmap_find_free_byte_and_set_bit(bitmap_block->data,
		    index_in_group, &rel_block_idx, blocks_in_group);
		if (rc == EOK) {
			bitmap_block->dirty = true;
			rc = block_put(bitmap_block);
			if (rc != EOK) {
				ext4_filesystem_put_block_group_ref(bg_ref);
				return rc;
			}

			allocated_block =
			    ext4_filesystem_index_in_group2blockaddr(sb, rel_block_idx,
			    bgid);

			goto success;
		}

		/* Try to find free bit in bitmap */
		rc = ext4_bitmap_find_free_bit_and_set(bitmap_block->data,
		    index_in_group, &rel_block_idx, blocks_in_group);
		if (rc == EOK) {
			bitmap_block->dirty = true;
			rc = block_put(bitmap_block);
			if (rc != EOK) {
				ext4_filesystem_put_block_group_ref(bg_ref);
				return rc;
			}

			allocated_block =
			    ext4_filesystem_index_in_group2blockaddr(sb, rel_block_idx,
			    bgid);

			goto success;
		}

		rc = block_put(bitmap_block);
		if (rc != EOK) {
			ext4_filesystem_put_block_group_ref(bg_ref);
			return rc;
		}

	next_group:
		rc = ext4_filesystem_put_block_group_ref(bg_ref);
		if (rc != EOK)
			return rc;

		/* Goto next group */
		bgid = (bgid + 1) % block_group_count;
		count--;
	}

	return ENOSPC;

success:
	block_size = ext4_superblock_get_block_size(sb);

	/* Update superblock free blocks count */
	uint32_t sb_free_blocks = ext4_superblock_get_free_blocks_count(sb);
	sb_free_blocks--;
	ext4_superblock_set_free_blocks_count(sb, sb_free_blocks);

	/* Update inode blocks (different block size!) count */
	uint64_t ino_blocks =
	    ext4_inode_get_blocks_count(sb, inode_ref->inode);
	ino_blocks += block_size / EXT4_INODE_BLOCK_SIZE;
	ext4_inode_set_blocks_count(sb, inode_ref->inode, ino_blocks);
	inode_ref->dirty = true;

	/* Update block group free blocks count */
	uint32_t bg_free_blocks =
	    ext4_block_group_get_free_blocks_count(bg_ref->block_group, sb);
	bg_free_blocks--;
	ext4_block_group_set_free_blocks_count(bg_ref->block_group, sb,
	    bg_free_blocks);
	bg_ref->dirty = true;

	rc = ext4_filesystem_put_block_group_ref(bg_ref);

	*fblock = allocated_block;
	return rc;
}

/** Try to allocate concrete block.
 *
 * @param inode_ref Inode to allocate block for
 * @param fblock    Block address to allocate
 * @param free      Output value - if target block is free
 *
 * @return Error code
 *
 */
errno_t ext4_balloc_try_alloc_block(ext4_inode_ref_t *inode_ref, uint32_t fblock,
    bool *free)
{
	errno_t rc;

	ext4_filesystem_t *fs = inode_ref->fs;
	ext4_superblock_t *sb = fs->superblock;

	/* Compute indexes */
	uint32_t block_group = ext4_filesystem_blockaddr2group(sb, fblock);
	uint32_t index_in_group =
	    ext4_filesystem_blockaddr2_index_in_group(sb, fblock);

	/* Load block group reference */
	ext4_block_group_ref_t *bg_ref;
	rc = ext4_filesystem_get_block_group_ref(fs, block_group, &bg_ref);
	if (rc != EOK)
		return rc;

	/* Load block with bitmap */
	uint32_t bitmap_block_addr =
	    ext4_block_group_get_block_bitmap(bg_ref->block_group, sb);
	block_t *bitmap_block;
	rc = block_get(&bitmap_block, fs->device, bitmap_block_addr, 0);
	if (rc != EOK) {
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	/* Check if block is free */
	*free = ext4_bitmap_is_free_bit(bitmap_block->data, index_in_group);

	/* Allocate block if possible */
	if (*free) {
		ext4_bitmap_set_bit(bitmap_block->data, index_in_group);
		bitmap_block->dirty = true;
	}

	/* Release block with bitmap */
	rc = block_put(bitmap_block);
	if (rc != EOK) {
		/* Error in saving bitmap */
		ext4_filesystem_put_block_group_ref(bg_ref);
		return rc;
	}

	/* If block is not free, return */
	if (!(*free))
		goto terminate;

	uint32_t block_size = ext4_superblock_get_block_size(sb);

	/* Update superblock free blocks count */
	uint32_t sb_free_blocks = ext4_superblock_get_free_blocks_count(sb);
	sb_free_blocks--;
	ext4_superblock_set_free_blocks_count(sb, sb_free_blocks);

	/* Update inode blocks count */
	uint64_t ino_blocks =
	    ext4_inode_get_blocks_count(sb, inode_ref->inode);
	ino_blocks += block_size / EXT4_INODE_BLOCK_SIZE;
	ext4_inode_set_blocks_count(sb, inode_ref->inode, ino_blocks);
	inode_ref->dirty = true;

	/* Update block group free blocks count */
	uint32_t free_blocks =
	    ext4_block_group_get_free_blocks_count(bg_ref->block_group, sb);
	free_blocks--;
	ext4_block_group_set_free_blocks_count(bg_ref->block_group,
	    sb, free_blocks);
	bg_ref->dirty = true;

terminate:
	return ext4_filesystem_put_block_group_ref(bg_ref);
}

/**
 * @}
 */