/* SPDX-License-Identifier: LGPL-3.0-or-later */
/*
 * fs_reader.c
 *
 * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
 */
#define SQFS_BUILDING_DLL
#include "internal.h"

static int inode_copy(const sqfs_inode_generic_t *inode,
		      sqfs_inode_generic_t **out)
{
	*out = alloc_flex(sizeof(*inode), 1, inode->payload_bytes_used);
	if (*out == NULL)
		return SQFS_ERROR_ALLOC;

	memcpy(*out, inode, sizeof(*inode) + inode->payload_bytes_used);
	return 0;
}

static int dcache_key_compare(const void *ctx, const void *l, const void *r)
{
	sqfs_u32 lhs = *((const sqfs_u32 *)l), rhs = *((const sqfs_u32 *)r);
	(void)ctx;

	return lhs < rhs ? -1 : (lhs > rhs ? 1 : 0);
}

static int dcache_add(sqfs_dir_reader_t *rd,
		      const sqfs_inode_generic_t *inode, sqfs_u64 ref)
{
	sqfs_u32 inum = inode->base.inode_number;

	if (!(rd->flags & SQFS_DIR_READER_DOT_ENTRIES))
		return 0;

	if (inode->base.type != SQFS_INODE_DIR &&
	    inode->base.type != SQFS_INODE_EXT_DIR) {
		return 0;
	}

	if (rbtree_lookup(&rd->dcache, &inum) != NULL)
		return 0;

	return rbtree_insert(&rd->dcache, &inum, &ref);
}

static int dcache_find(sqfs_dir_reader_t *rd, sqfs_u32 inode, sqfs_u64 *ref)
{
	rbtree_node_t *node;

	if (!(rd->flags & SQFS_DIR_READER_DOT_ENTRIES))
		return SQFS_ERROR_NO_ENTRY;

	node = rbtree_lookup(&rd->dcache, &inode);
	if (node == NULL)
		return SQFS_ERROR_NO_ENTRY;

	*ref = *((sqfs_u64 *)rbtree_node_value(node));
	return 0;
}

static void dir_reader_destroy(sqfs_object_t *obj)
{
	sqfs_dir_reader_t *rd = (sqfs_dir_reader_t *)obj;

	if (rd->flags & SQFS_DIR_READER_DOT_ENTRIES)
		rbtree_cleanup(&rd->dcache);

	sqfs_drop(rd->meta_inode);
	sqfs_drop(rd->meta_dir);
	free(rd);
}

static sqfs_object_t *dir_reader_copy(const sqfs_object_t *obj)
{
	const sqfs_dir_reader_t *rd = (const sqfs_dir_reader_t *)obj;
	sqfs_dir_reader_t *copy  = malloc(sizeof(*copy));

	if (copy == NULL)
		return NULL;

	memcpy(copy, rd, sizeof(*copy));

	if (rd->flags & SQFS_DIR_READER_DOT_ENTRIES) {
		if (rbtree_copy(&rd->dcache, &copy->dcache))
			goto fail_cache;
	}

	copy->meta_inode = sqfs_copy(rd->meta_inode);
	if (copy->meta_inode == NULL)
		goto fail_mino;

	copy->meta_dir = sqfs_copy(rd->meta_dir);
	if (copy->meta_dir == NULL)
		goto fail_mdir;

	return (sqfs_object_t *)copy;
fail_mdir:
	sqfs_drop(copy->meta_inode);
fail_mino:
	if (copy->flags & SQFS_DIR_READER_DOT_ENTRIES)
		rbtree_cleanup(&copy->dcache);
fail_cache:
	free(copy);
	return NULL;
}

sqfs_dir_reader_t *sqfs_dir_reader_create(const sqfs_super_t *super,
					  sqfs_compressor_t *cmp,
					  sqfs_file_t *file,
					  sqfs_u32 flags)
{
	sqfs_dir_reader_t *rd;
	sqfs_u64 start, limit;
	int ret;

	if (flags & ~SQFS_DIR_READER_ALL_FLAGS)
		return NULL;

	rd = calloc(1, sizeof(*rd));
	if (rd == NULL)
		return NULL;

	sqfs_object_init(rd, dir_reader_destroy, dir_reader_copy);

	if (flags & SQFS_DIR_READER_DOT_ENTRIES) {
		ret = rbtree_init(&rd->dcache, sizeof(sqfs_u32),
				  sizeof(sqfs_u64), dcache_key_compare);

		if (ret != 0)
			goto fail_dcache;
	}

	start = super->inode_table_start;
	limit = super->directory_table_start;

	rd->meta_inode = sqfs_meta_reader_create(file, cmp, start, limit);
	if (rd->meta_inode == NULL)
		goto fail_mino;

	start = super->directory_table_start;
	limit = super->id_table_start;

	if (super->fragment_table_start < limit)
		limit = super->fragment_table_start;

	if (super->export_table_start < limit)
		limit = super->export_table_start;

	rd->meta_dir = sqfs_meta_reader_create(file, cmp, start, limit);
	if (rd->meta_dir == NULL)
		goto fail_mdir;

	rd->super = *super;
	rd->flags = flags;
	rd->state = DIR_STATE_NONE;
	return rd;
fail_mdir:
	sqfs_drop(rd->meta_inode);
fail_mino:
	if (flags & SQFS_DIR_READER_DOT_ENTRIES)
		rbtree_cleanup(&rd->dcache);
fail_dcache:
	free(rd);
	return NULL;
}

int sqfs_dir_reader_open_dir(sqfs_dir_reader_t *rd,
			     const sqfs_inode_generic_t *inode,
			     sqfs_u32 flags)
{
	sqfs_u32 parent;
	int ret;

	if (flags & (~SQFS_DIR_OPEN_ALL_FLAGS))
		return SQFS_ERROR_UNSUPPORTED;

	ret = sqfs_readdir_state_init(&rd->it, &rd->super, inode);
	if (ret)
		return ret;

	if ((rd->flags & SQFS_DIR_READER_DOT_ENTRIES) &&
	    !(flags & SQFS_DIR_OPEN_NO_DOT_ENTRIES)) {
		if (inode->base.type == SQFS_INODE_EXT_DIR) {
			parent = inode->data.dir_ext.parent_inode;
		} else {
			parent = inode->data.dir.parent_inode;
		}

		if (dcache_find(rd, inode->base.inode_number, &rd->cur_ref))
			return SQFS_ERROR_NO_ENTRY;

		if (rd->cur_ref == rd->super.root_inode_ref) {
			rd->parent_ref = rd->cur_ref;
		} else if (dcache_find(rd, parent, &rd->parent_ref)) {
			return SQFS_ERROR_NO_ENTRY;
		}

		rd->state = DIR_STATE_OPENED;
	} else {
		rd->state = DIR_STATE_ENTRIES;
	}

	rd->start_state = rd->state;
	return 0;
}

static int mk_dummy_entry(const char *str, sqfs_dir_node_t **out)
{
	size_t len = strlen(str);
	sqfs_dir_node_t *ent;

	ent = calloc(1, sizeof(sqfs_dir_node_t) + len + 1);
	if (ent == NULL)
		return SQFS_ERROR_ALLOC;

	ent->type = SQFS_INODE_DIR;
	ent->size = len - 1;

	strcpy((char *)ent->name, str);

	*out = ent;
	return 0;
}

int sqfs_dir_reader_read(sqfs_dir_reader_t *rd, sqfs_dir_node_t **out)
{
	int err;

	switch (rd->state) {
	case DIR_STATE_OPENED:
		err = mk_dummy_entry(".", out);
		if (err == 0) {
			rd->state = DIR_STATE_DOT;
			rd->ent_ref = rd->cur_ref;
		}
		return err;
	case DIR_STATE_DOT:
		err = mk_dummy_entry("..", out);
		if (err == 0) {
			rd->state = DIR_STATE_ENTRIES;
			rd->ent_ref = rd->parent_ref;
		}
		return err;
	case DIR_STATE_ENTRIES:
		break;
	default:
		return SQFS_ERROR_SEQUENCE;
	}

	return sqfs_meta_reader_readdir(rd->meta_dir, &rd->it,
					out, NULL, &rd->ent_ref);
}

int sqfs_dir_reader_rewind(sqfs_dir_reader_t *rd)
{
	if (rd->state == DIR_STATE_NONE)
		return SQFS_ERROR_SEQUENCE;

	sqfs_readdir_state_reset(&rd->it);
	rd->state = rd->start_state;
	return 0;
}

int sqfs_dir_reader_find(sqfs_dir_reader_t *rd, const char *name)
{
	sqfs_dir_node_t *ent;
	int ret;

	ret = sqfs_dir_reader_rewind(rd);
	if (ret != 0)
		return ret;

	do {
		ret = sqfs_dir_reader_read(rd, &ent);
		if (ret < 0)
			return ret;
		if (ret > 0)
			return SQFS_ERROR_NO_ENTRY;

		ret = strcmp((const char *)ent->name, name);
		free(ent);
	} while (ret < 0);

	return ret == 0 ? 0 : SQFS_ERROR_NO_ENTRY;
}

int sqfs_dir_reader_get_inode(sqfs_dir_reader_t *rd,
			      sqfs_inode_generic_t **inode)
{
	int ret;

	ret = sqfs_meta_reader_read_inode(rd->meta_inode, &rd->super,
					  rd->ent_ref >> 16,
					  rd->ent_ref & 0x0FFFF, inode);
	if (ret != 0)
		return ret;

	return dcache_add(rd, *inode, rd->ent_ref);
}

int sqfs_dir_reader_get_root_inode(sqfs_dir_reader_t *rd,
				   sqfs_inode_generic_t **inode)
{
	sqfs_u64 block_start = rd->super.root_inode_ref >> 16;
	sqfs_u16 offset = rd->super.root_inode_ref & 0xFFFF;
	int ret;

	ret = sqfs_meta_reader_read_inode(rd->meta_inode, &rd->super,
					  block_start, offset, inode);
	if (ret != 0)
		return ret;

	return dcache_add(rd, *inode, rd->super.root_inode_ref);
}

int sqfs_dir_reader_find_by_path(sqfs_dir_reader_t *rd,
				 const sqfs_inode_generic_t *start,
				 const char *path, sqfs_inode_generic_t **out)
{
	sqfs_inode_generic_t *inode;
	const char *ptr;
	int ret = 0;
	char *name;

	if (start == NULL) {
		ret = sqfs_dir_reader_get_root_inode(rd, &inode);
	} else {
		ret = inode_copy(start, &inode);
	}

	if (ret)
		return ret;

	for (; *path != '\0'; path = ptr) {
		if (*path == '/') {
			for (ptr = path; *ptr == '/'; ++ptr)
				;
			continue;
		}

		ret = sqfs_dir_reader_open_dir(rd, inode, 0);
		free(inode);
		if (ret)
			return ret;

		ptr = strchrnul(path, '/');

		name = strndup(path, ptr - path);
		if (name == NULL)
			return SQFS_ERROR_ALLOC;

		ret = sqfs_dir_reader_find(rd, name);
		free(name);
		if (ret)
			return ret;

		ret = sqfs_dir_reader_get_inode(rd, &inode);
		if (ret)
			return ret;
	}

	*out = inode;
	return 0;
}