// MIT License, Copyright (c) 2020 Marvin Borner
// EXT2 based filesystem

#include <assert.h>
#include <def.h>
#include <fs.h>
#include <ide.h>
#include <mem.h>
#include <print.h>
#include <str.h>

void *buffer_read(u32 block)
{
	return ide_read(malloc(BLOCK_SIZE), block);
}

struct superblock *get_superblock(void)
{
	struct superblock *sb = buffer_read(EXT2_SUPER);
	if (sb->magic != EXT2_MAGIC)
		return NULL;
	return sb;
}

struct bgd *get_bgd(void)
{
	return buffer_read(EXT2_SUPER + 1);
}

struct inode *get_inode(u32 i)
{
	struct superblock *s = get_superblock();
	assert(s);
	struct bgd *b = get_bgd();
	assert(b);

	u32 block_group = (i - 1) / s->inodes_per_group;
	u32 index = (i - 1) % s->inodes_per_group;
	u32 block = (index * INODE_SIZE) / BLOCK_SIZE;
	b += block_group;

	u32 *data = buffer_read(b->inode_table + block);
	struct inode *in =
		(struct inode *)((u32)data + (index % (BLOCK_SIZE / INODE_SIZE)) * INODE_SIZE);
	return in;
}

u32 read_indirect(u32 indirect, u32 block_num)
{
	char *data = buffer_read(indirect);
	return *(u32 *)((u32)data + block_num * sizeof(u32));
}

void *read_inode(struct inode *in)
{
	assert(in);
	if (!in)
		return NULL;

	u32 num_blocks = in->blocks / (BLOCK_SIZE / SECTOR_SIZE);

	assert(num_blocks != 0);
	if (!num_blocks)
		return NULL;

	/* u32 sz = BLOCK_SIZE * num_blocks; */
	u32 sz = in->size;
	void *buf = malloc(sz);
	printf("Loading %dKiB\n", sz >> 10);
	assert(buf != NULL);

	u32 indirect = 0;
	u32 blocknum = 0;
	char *data = 0;
	// TODO: Support triply indirect pointers
	// TODO: This can be heavily optimized by saving the indirect block lists
	for (u32 i = 0; i < num_blocks; i++) {
		if (i < 12) {
			blocknum = in->block[i];
			data = buffer_read(blocknum);
			memcpy((u32 *)((u32)buf + i * BLOCK_SIZE), data, BLOCK_SIZE);
		} else if (i < BLOCK_COUNT + 12) {
			indirect = in->block[12];
			blocknum = read_indirect(indirect, i - 12);
			data = buffer_read(blocknum);
			memcpy((u32 *)((u32)buf + i * BLOCK_SIZE), data, BLOCK_SIZE);
		} else {
			indirect = in->block[13];
			blocknum = read_indirect(indirect, (i - (BLOCK_COUNT + 12)) / BLOCK_COUNT);
			blocknum = read_indirect(blocknum, (i - (BLOCK_COUNT + 12)) % BLOCK_COUNT);
			data = buffer_read(blocknum);
			memcpy((u32 *)((u32)buf + i * BLOCK_SIZE), data, BLOCK_SIZE);
		}
		/* printf("Loaded %d of %d\n", i + 1, num_blocks); */
	}

	return buf;
}

u32 find_inode(const char *name, u32 dir_inode)
{
	if (!dir_inode)
		return (unsigned)-1;

	struct inode *i = get_inode(dir_inode);

	char *buf = malloc(BLOCK_SIZE * i->blocks / 2);
	memset(buf, 0, BLOCK_SIZE * i->blocks / 2);

	for (u32 q = 0; q < i->blocks / 2; q++) {
		char *data = buffer_read(i->block[q]);
		memcpy((u32 *)((u32)buf + q * BLOCK_SIZE), data, BLOCK_SIZE);
	}

	struct dirent *d = (struct dirent *)buf;

	u32 sum = 0;
	do {
		// Calculate the 4byte aligned size of each entry
		sum += d->total_len;
		if (strlen(name) == d->name_len &&
		    strncmp((void *)d->name, name, d->name_len) == 0) {
			free(buf);
			return d->inode_num;
		}
		d = (struct dirent *)((u32)d + d->total_len);

	} while (sum < (1024 * i->blocks / 2));
	free(buf);
	return (unsigned)-1;
}

struct inode *find_inode_by_path(char *path)
{
	if (path[0] != '/')
		return 0;

	path++;
	u32 current_inode = EXT2_ROOT;

	int i = 0;
	while (1) {
		for (i = 0; path[i] != '/' && path[i] != '\0'; i++)
			;

		if (path[i] == '\0')
			break;

		path[i] = '\0';
		current_inode = find_inode(path, current_inode);
		path[i] = '/';

		if (current_inode == 0)
			return 0;

		path += i + 1;
	}

	u32 inode = find_inode(path, current_inode);
	if ((signed)inode <= 0)
		return 0;

	return get_inode(inode);
}

void *file_read(char *path)
{
	struct inode *in = find_inode_by_path(path);
	if (in)
		return read_inode(in);
	else
		return NULL;
}

u32 file_stat(char *path)
{
	struct inode *in = find_inode_by_path(path);
	if (!in)
		return 0;

	return in->size;
}