#include "tar.h"

#include "queue.h"

#include <fs/dentry.h>
#include <fs/file.h>
#include <fs/inode.h>
#include <fs/superblock.h>
#include <mango/handle.h>
#include <mango/log.h>
#include <mango/vm.h>
#include <stdio.h>
#include <string.h>
#include <xpc/buffer.h>

struct tar_superblock {
	struct fs_superblock sb_base;
	struct tar_bin_header *sb_data;
};

struct tar_entry {
	struct fs_dentry e_dentry;
	struct fs_inode e_inode;
	void *e_data;
	struct queue_entry e_entry;
	struct queue e_children;
};

size_t getsize(const char *in)
{
	size_t size = 0;
	size_t j;
	size_t count = 1;

	for (j = 11; j > 0; j--, count *= 8) {
		size += ((in[j - 1] - '0') * count);
	}

	return size;
}

int tar_init(struct tar *tar, uintptr_t base)
{
	memset(tar, 0x0, sizeof *tar);
	tar->tar_entries = (struct tar_bin_header *)base;
	return 0;
}

int tar_open(struct tar *tar, const char *path, struct tar_file *out)
{
	while (*path == '/') {
		path++;
	}

	if (*path == '\0') {
		return -1;
	}

	struct tar_bin_header *bin_header = tar->tar_entries;
	struct tar_header header;
	for (size_t i = 0;; i++) {
		tar_header_decode(bin_header, &header);
		if (bin_header->filename[0] == 0) {
			break;
		}

		char *s = (char *)bin_header;
		s += sizeof *bin_header;

		if (!strcmp(bin_header->filename, path)) {
			out->f_header = header;
			out->f_data = s;
			return 0;
		}

		s += header.size;
		s += ((sizeof *bin_header)
		      - ((uintptr_t)s % (sizeof *bin_header)));

		bin_header = (struct tar_bin_header *)s;
	}

	return -1;
}

int tar_file_create_vm_object(const struct tar_file *file, kern_handle_t *out)
{
	const void *data = file->f_data;
	size_t len = file->f_header.size;
	kern_handle_t vmo = KERN_HANDLE_INVALID;

	kern_status_t status = vm_object_create(
		NULL,
		0,
		file->f_header.size,
		VM_PROT_READ | VM_PROT_EXEC | VM_PROT_USER,
		&vmo);
	if (status != KERN_OK) {
		return -1;
	}

	size_t nr_written = 0;
	status = vm_object_write(vmo, data, 0, len, &nr_written);
	if (status != KERN_OK || nr_written != len) {
		kern_handle_close(vmo);
		return -1;
	}

	*out = vmo;
	return 0;
}

int tar_header_decode(const struct tar_bin_header *in, struct tar_header *out)
{
	memcpy(out->filename, in->filename, sizeof out->filename);
	out->size = getsize(in->size);
	return 0;
}

static struct tar_entry *entry_from_dentry(struct fs_dentry *dent)
{
	return QUEUE_CONTAINER(struct tar_entry, e_dentry, dent);
}

static struct tar_entry *entry_from_inode(struct fs_inode *inode)
{
	return QUEUE_CONTAINER(struct tar_entry, e_inode, inode);
}

static struct tar_entry *entry_get_child(
	struct tar_entry *entry,
	const char *name)
{
	struct queue_entry *cur = queue_first(&entry->e_children);
	while (cur) {
		struct tar_entry *child
			= QUEUE_CONTAINER(struct tar_entry, e_entry, cur);

		if (!strcmp(child->e_dentry.d_name, name)) {
			return child;
		}

		cur = queue_next(cur);
	}

	return NULL;
}

static const struct fs_dentry_ops dentry_ops = {};

static enum fs_status dir_lookup(
	struct fs_inode *inode,
	const char *name,
	struct fs_dentry **out)
{
	struct tar_entry *entry = entry_from_inode(inode);
	struct tar_entry *child = entry_get_child(entry, name);
	if (!child) {
		return FS_ERR_NO_ENTRY;
	}

	*out = &child->e_dentry;
	return FS_SUCCESS;
}

static enum fs_status file_read(
	struct fs_file *f,
	xpc_buffer_t *buf,
	size_t count,
	off_t *seek)
{
	off_t offset = *seek;
	struct tar_entry *entry = entry_from_inode(fs_file_get_inode(f));
	if (!entry) {
		return FS_ERR_BAD_STATE;
	}

	if (offset >= entry->e_inode.i_size) {
		count = 0;
	} else if (offset + count > entry->e_inode.i_size) {
		count = entry->e_inode.i_size - offset;
	}

	if (count == 0) {
		return FS_SUCCESS;
	}

	char *src = (char *)entry->e_data + offset;
	size_t w;
	xpc_buffer_write(buf, src, count, &w);

	offset += count;
	*seek = offset;

	return FS_SUCCESS;
}

static const struct fs_file_ops file_ops = {
	.f_read = file_read,
};

static const struct fs_inode_ops file_inode_ops = {
	.i_lookup = NULL,
};

static const struct fs_inode_ops dir_inode_ops = {
	.i_lookup = dir_lookup,
};

static struct tar_entry *create_dir_entry(
	struct fs_context *ctx,
	struct tar_superblock *sb,
	const char *name)
{
	struct tar_entry *entry = fs_context_alloc(ctx, sizeof *entry);
	if (!entry) {
		return NULL;
	}

	memset(entry, 0x0, sizeof *entry);

	entry->e_inode.i_sb = &sb->sb_base;
	entry->e_inode.i_mode = FS_INODE_DIR;
	entry->e_inode.i_ops = &dir_inode_ops;

	entry->e_dentry.d_sb = &sb->sb_base;
	entry->e_dentry.d_ops = &dentry_ops;
	entry->e_dentry.d_inode = &entry->e_inode;

	size_t name_len = strlen(name);
	entry->e_dentry.d_name = fs_context_alloc(ctx, name_len + 1);
	if (!entry->e_dentry.d_name) {
		fs_context_free(ctx, entry);
		return NULL;
	}

	memcpy(entry->e_dentry.d_name, name, name_len + 1);

	return entry;
}

static struct tar_entry *create_file_entry(
	struct fs_context *ctx,
	struct tar_superblock *sb,
	struct tar_header *header,
	void *data,
	const char *name)
{
	struct tar_entry *entry = fs_context_alloc(ctx, sizeof *entry);
	if (!entry) {
		return NULL;
	}

	memset(entry, 0x0, sizeof *entry);

	entry->e_inode.i_sb = &sb->sb_base;
	entry->e_inode.i_mode = FS_INODE_REG;
	entry->e_inode.i_ops = &file_inode_ops;
	entry->e_inode.i_fops = &file_ops;
	entry->e_inode.i_size = header->size;

	entry->e_dentry.d_sb = &sb->sb_base;
	entry->e_dentry.d_ops = &dentry_ops;
	entry->e_dentry.d_inode = &entry->e_inode;

	entry->e_data = data;

	size_t name_len = strlen(name);
	entry->e_dentry.d_name = fs_context_alloc(ctx, name_len + 1);
	if (!entry->e_dentry.d_name) {
		fs_context_free(ctx, entry);
		return NULL;
	}

	memcpy(entry->e_dentry.d_name, name, name_len + 1);

	return entry;
}

static size_t get_first_path_component(const char *in, char *out, size_t max)
{
	size_t i = 0;
	while (i < max - 1) {
		if (in[i] == '\0' || in[i] == '/') {
			break;
		}

		out[i] = in[i];
		i++;
	}

	out[i] = '\0';
	return i;
}

static enum fs_status add_entry_to_tree(
	struct fs_context *ctx,
	struct tar_superblock *sb,
	struct tar_header *entry,
	void *data)
{
	struct tar_entry *cur = entry_from_dentry(sb->sb_base.s_root);
	const char *path = entry->filename;

	char tok[256];

	while (*path != '\0') {
		while (*path == '/') {
			path++;
		}

		size_t tok_len
			= get_first_path_component(path, tok, sizeof tok);

		if (!tok_len) {
			break;
		}

		struct tar_entry *next = entry_get_child(cur, tok);
		bool is_file = *(path + tok_len) == '\0';
		if (next) {
			goto next;
		}

		if (is_file) {
			next = create_file_entry(ctx, sb, entry, data, tok);
		} else {
			next = create_dir_entry(ctx, sb, tok);
		}

		if (!next) {
			return FS_ERR_NO_MEMORY;
		}

		queue_push_back(&cur->e_children, &next->e_entry);
		next->e_dentry.d_parent = &cur->e_dentry;

	next:
		cur = next;
		path += tok_len;
	}

	return FS_SUCCESS;
}

static enum fs_status build_dentry_tree(
	struct fs_context *ctx,
	struct tar_superblock *sb)
{

	struct tar_entry *root = create_dir_entry(ctx, sb, "/");
	if (!root) {
		return FS_ERR_NO_MEMORY;
	}

	sb->sb_base.s_root = &root->e_dentry;
	struct tar_bin_header *bin_header = sb->sb_data;
	struct tar_header header;
	enum fs_status status = FS_SUCCESS;

	for (size_t i = 0;; i++) {
		tar_header_decode(bin_header, &header);
		if (bin_header->filename[0] == 0) {
			break;
		}

		char *s = (char *)bin_header;
		s += sizeof *bin_header;

		bool add = true;

		if (!strcmp(header.filename, "././@PaxHeader")) {
			add = false;
		}

		if (add) {
			status = add_entry_to_tree(ctx, sb, &header, s);
		}

		if (status != FS_SUCCESS) {
			break;
		}

		s += header.size;
		s += ((sizeof *bin_header)
		      - ((uintptr_t)s % (sizeof *bin_header)));

		bin_header = (struct tar_bin_header *)s;
	}

	return FS_SUCCESS;
}

enum fs_status tar_mount(
	struct fs_context *ctx,
	void *arg,
	enum fs_mount_flags flags,
	struct fs_superblock **out)
{
	struct tar_superblock *sb = fs_context_alloc(ctx, sizeof *sb);
	if (!sb) {
		return FS_ERR_NO_MEMORY;
	}

	sb->sb_data = arg;

	enum fs_status status = build_dentry_tree(ctx, sb);
	if (status != FS_SUCCESS) {
		fs_context_free(ctx, sb);
		return status;
	}

	*out = (struct fs_superblock *)sb;
	return FS_SUCCESS;
}