use crate::disk::inode::InodeMode;
use crate::utils::{from_systime, time_now, to_fileattr, to_filetype};
use crate::utils::permissions::get_groups;
use crate::{AyaFS, TTL};
use fuser::{Filesystem, KernelConfig, ReplyAttr, ReplyData, ReplyDirectory, ReplyEmpty,
            ReplyEntry, ReplyLseek, ReplyOpen, Request, TimeOrNow,
};
use libc::{c_int, EACCES, EEXIST, ENAMETOOLONG, ENOENT, ENOSPC, ENOSYS, ENOTDIR, EPERM, R_OK, S_ISGID, S_ISUID, S_IXGRP, S_IXOTH, S_IXUSR, W_OK};
use log::debug;
use std::ffi::OsStr;
use std::time::SystemTime;
use fuser::TimeOrNow::{Now, SpecificTime};
use crate::utils::permissions::{check_access, clear_suid_sgid};

impl AyaFS {

}

impl Filesystem for AyaFS {
    fn init(&mut self, _req: &Request<'_>, _config: &mut KernelConfig) -> Result<(), c_int> {
        debug!("`init()");
        Ok(())
    }

    fn destroy(&mut self) {
        debug!("destroy()");
        // TODO 写回
    }

    fn lookup(&mut self, req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEntry) {
        if name.len() > 255 {
            reply.error(ENAMETOOLONG);
            return;
        }

        let parent = parent as usize;
        if let Some(parent_inode) = self.get_inode(parent) {
            if check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                R_OK
            ) {
                let parent_inode = parent_inode.clone();
                match self.lookup_name(&parent_inode, name) {
                    Ok((inode_index, _, inode)) => {
                        let attr = to_fileattr(inode_index as usize, &inode);
                        reply.entry(&TTL, &attr, 0);
                    },
                    Err(err_code) => reply.error(err_code)
                };
            } else {
                reply.error(EACCES);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn getattr(&mut self, _req: &Request<'_>, ino: u64, reply: ReplyAttr) {
        debug!("Filesystem::getattr(ino: {})", ino);
        if let Some(inode) = self.get_inode(ino as usize) {
            reply.attr(&TTL, &to_fileattr(ino as usize, inode));
        } else {
            reply.error(ENOENT);
        }
    }

    fn setattr(
        &mut self,
        req: &Request<'_>,
        ino: u64,
        mode: Option<u32>,
        uid: Option<u32>,
        gid: Option<u32>,
        size: Option<u64>, // TODO 当 setattr 被 ftruncate invoke 时会设置 size
        atime: Option<TimeOrNow>,
        mtime: Option<TimeOrNow>,
        _ctime: Option<SystemTime>,
        fh: Option<u64>, // TODO 当 setattr 被 ftruncate invoke 时会提供 fh
        _crtime: Option<SystemTime>, // 忽略
        _chgtime: Option<SystemTime>, // 忽略
        _bkuptime: Option<SystemTime>, // 忽略
        _flags: Option<u32>, // 忽略
        reply: ReplyAttr,
    ) {
        if let Some(inode) = self.get_inode_mut(ino as usize) {
            // chmod
            if let Some(mode) = mode {
                debug!("chmod on inode {:#x?} mode {:o}", ino, mode);
                if req.uid() != 0 && req.uid() != inode.uid {
                    reply.error(EPERM);
                    return;
                } // uid == 0 (root) or uid == inode.uid (user itself)

                if req.uid() != 0 && req.gid() != inode.gid && !get_groups(req.pid()).contains(&inode.gid) {
                    inode.mode = InodeMode((mode & !S_ISGID) as u16);
                } else {
                    inode.mode = InodeMode(mode as u16);
                }

                inode.ctime = time_now();
                reply.attr(&TTL, &to_fileattr(ino as usize, inode));
                return;
            }

            // chown
            if uid.is_some() || gid.is_some() {
                debug!("chown on inode {:#x?} uid {:?} gid {:?}", ino, uid, gid);
                if let Some(uid) = uid {
                    // 虽然只有 root 可以 chown 但是 user chown 自己也是不报错的
                    if req.uid() != 0 && !(uid == inode.uid && uid == req.uid()) {
                        reply.error(EPERM);
                        return;
                    }
                }
                if let Some(gid) = gid {
                    // 只有 root 和 file owner 才可以 chgrp
                    if req.uid() != 0 && req.uid() != inode.uid {
                        reply.error(EPERM);
                        return;
                    }
                    // root 可以任意 chgrp, 非 root 只能修改到用户自己所在的组里
                    if req.gid() != 0 && !get_groups(req.pid()).contains(&gid) {
                        reply.error(EPERM);
                        return;
                    }
                }

                // 可执行文件要清除 suid & sgid
                if inode.mode.0 & (S_IXUSR | S_IXGRP | S_IXOTH) as u16 != 0 {
                    inode.mode = clear_suid_sgid(inode.mode);
                }

                // chown 要清除 suid
                if let Some(uid) = uid {
                    inode.uid = uid;
                    inode.mode.0 &= !S_ISUID as u16;
                }

                if let Some(gid) = gid {
                    inode.gid = gid;
                    if req.uid() != 0 {
                        inode.mode.0 &= !S_ISGID as u16;
                    }
                }
                inode.ctime = time_now();
                reply.attr(&TTL, &to_fileattr(ino as usize, inode));
                return;
            }

            // ftruncate
            if let Some(size) = size {
                debug!("ftruncate on inode {:#x?} size {:?}", ino, size);
                if let Some(file_handle) = fh {
                    // 有 file handle 的
                    todo!()
                } else {
                    // 没有 file handle 基于 inode 的
                    todo!()
                }
            }

            // time 相关
            if atime.is_some() || mtime.is_some() {
                let current_time = time_now();
                if let Some(atime) = atime {
                    debug!("utimensat on inode {:#x?}, atime {:?}", ino, atime);
                    // root 和 user 可以随意修改 atime, 其他用户只能 touch (即 atime == Now)
                    if req.uid() != 0 && req.uid() != inode.uid && atime != Now {
                        reply.error(EPERM);
                        return;
                    }

                    if req.uid() != 0 && req.uid() != inode.uid && check_access(
                        req.uid(),
                        req.gid(),
                        inode.uid,
                        inode.gid,
                        inode.mode,
                        R_OK, // atime 来说是 read TODO 对吗
                    ) {
                        reply.error(EACCES);
                        return;
                    }

                    inode.atime = match atime {
                        SpecificTime(time) => from_systime(time),
                        Now => current_time,
                    };
                    inode.ctime = current_time;
                }
                if let Some(mtime) = mtime {
                    debug!("utimensat on inode {:#x?}, mtime {:?}", ino, mtime);
                    // root 和 user 可以随意修改 mtime, 其他用户只能 mtime == Now
                    if req.uid() != 0 && req.uid() != inode.uid && mtime != Now {
                        reply.error(EPERM);
                        return;
                    }

                    if req.uid() != 0 && req.uid() != inode.uid && check_access(
                        req.uid(),
                        req.gid(),
                        inode.uid,
                        inode.gid,
                        inode.mode,
                        W_OK, // mtime 来说是 write
                    ) {
                        reply.error(EACCES);
                        return;
                    }

                    inode.mtime = match mtime {
                        SpecificTime(time) => from_systime(time),
                        Now => current_time,
                    };
                    inode.ctime = current_time;
                }
            }
            reply.attr(&TTL, &to_fileattr(ino as usize, inode));
            return;
        } else {
            reply.error(ENOENT);
        }
    }

    fn readlink(&mut self, _req: &Request<'_>, ino: u64, reply: ReplyData) {
        debug!("[Not Implemented] readlink(ino: {})", ino);
        reply.error(ENOSYS);
    }

    fn mknod(
        &mut self,
        req: &Request<'_>,
        parent: u64,
        name: &OsStr,
        mode: u32,
        _umask: u32, // umask 是用不到的
        _rdev: u32,  // the device number (only valid if created file is a device)
        reply: ReplyEntry,
    ) {
        debug!(
            "Filesystem::mknod(parent: {}, name: {:?}, mode: {}, umask: {})",
            parent, name, mode, _umask
        );

        if let Some(parent_inode) = self.get_inode(parent as usize) {
            if check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                W_OK
            ) {
                if parent_inode.is_dir() {
                    let parent_inode = parent_inode.clone();
                    // 如果已经存在, 返回 already exists
                    if self.lookup_name(&parent_inode, name).is_ok() {
                        reply.error(EEXIST);
                        return;
                    }
                    // 文件名长度超过 255, 返回 filename too long
                    if name.len() > 255 {
                        reply.error(ENAMETOOLONG);
                        return;
                    }

                    let mode = mode as u16;
                    if let Some((inode_index, inode)) = self.create_file(
                        mode,
                        req.uid(),
                        req.gid(),
                        0,
                    ) {
                        let file_attr = to_fileattr(inode_index, inode);
                        // TODO 把 inode 挂到 parent 下
                        self.update_inode(parent as usize, parent_inode);
                        // 前面 clone 了, 这里写回
                        reply.entry(&TTL, &file_attr, 0);
                    } else {
                        // create_inode 失败 -> no enough space
                        reply.error(ENOSPC);
                    }
                } else {
                    // parent 不是 IFDIR -> Not a directory
                    reply.error(ENOTDIR);
                }
            } else {
                reply.error(EACCES);
            }
        } else {
            // parent 不存在 -> No such file or directory
            reply.error(ENOENT);
        }
    }

    fn mkdir(
        &mut self,
        req: &Request<'_>,
        parent: u64,
        name: &OsStr,
        mode: u32,
        _umask: u32, // umask 应该也是用不到的
        reply: ReplyEntry,
    ) {
        if let Some(parent_inode) = self.get_inode(parent as usize) {
            if check_access(
                req.uid(),
                req.gid(),
                parent_inode.uid,
                parent_inode.gid,
                parent_inode.mode,
                W_OK
            ) {
                if parent_inode.is_dir() {
                    let parent_inode = parent_inode.clone();
                    // 如果已经存在, 返回 already exists
                    if self.lookup_name(&parent_inode, name).is_ok() {
                        reply.error(EEXIST);
                        return;
                    }
                    // 文件名长度超过 255, 返回 filename too long
                    if name.len() > 255 {
                        reply.error(ENAMETOOLONG);
                        return;
                    }

                    let mode = mode as u16;
                    if let Some((inode_index, inode)) = self.create_directory(
                        mode,
                        req.uid(),
                        req.gid(),
                        0,
                    ) {
                        let file_attr = to_fileattr(inode_index, inode);
                        // TODO 把 inode 挂到 parent 下
                        self.update_inode(parent as usize, parent_inode);
                        // 前面 clone 了, 这里写回
                        reply.entry(&TTL, &file_attr, 0);
                    } else {
                        // create_inode 失败 -> no enough space
                        reply.error(ENOSPC);
                    }
                } else {
                    // parent 不是 IFDIR -> Not a directory
                    reply.error(ENOTDIR);
                }
            } else {
                reply.error(EACCES);
            }
        } else {
            // parent 不存在 -> No such file or directory
            reply.error(ENOENT);
        }
    }

    fn unlink(&mut self, _req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEmpty) {
        debug!("unlink(parent: {:#x?}, name: {:?})", parent, name,);
        if let Some(inode) = self.get_inode_mut(parent as usize) {
            if inode.is_file() {
                // TODO 找到这个 inode 并且删掉
                reply.ok();
            } else {
                reply.error(ENOENT);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn rmdir(&mut self, _req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEmpty) {
        debug!("rmdir(parent: {:#x?}, name: {:?}", parent, name,);
        if let Some(inode) = self.get_inode_mut(parent as usize) {
            if inode.is_file() {
                // TODO 找到这个 inode 并且删掉
                reply.ok();
            } else {
                reply.error(ENOTDIR);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn read(
        &mut self,
        _req: &Request<'_>,
        ino: u64,
        _fh: u64,
        offset: i64,
        _size: u32,
        _flags: i32,
        _lock_owner: Option<u64>,
        reply: ReplyData,
    ) {
        todo!()
    }

    fn opendir(&mut self, _req: &Request<'_>, ino: u64, flags: i32, reply: ReplyOpen) {
        debug!("OPENDIR ino {:#x} flags {}", ino, flags);
        reply.opened(1, 0);
    }

    fn readdir(
        &mut self,
        req: &Request<'_>,
        ino: u64,
        _fh: u64, // 如果 invoke 它的 opendir 里有指定 fh, 那么这里会收到 fh 参数
        offset: i64,
        mut reply: ReplyDirectory,
    ) {
        if let Some(inode) = self.get_inode(ino as usize) {
            if inode.is_dir() {
                if check_access(
                    req.uid(),
                    req.gid(),
                    inode.uid,
                    inode.gid,
                    inode.mode,
                    R_OK,
                ) {
                    let inode = inode.clone();
                    let mut entry_index = offset as u32;

                    while let Some(dir_entry) = self.get_direntry(&inode, entry_index) {
                        debug!("reading inode {:#x} index {}", ino, entry_index);
                        if entry_index >= inode.size {
                            break;
                        }
                        // 最开头应该添加 `.` 和 `..`, 但这件事应该在 mkdir 的时候就在 inode 里加好
                        // reply.add 返回 true 说明 buffer 已满, 停止累加
                        if reply.add(
                            dir_entry.inode as u64,
                            entry_index as i64,
                            to_filetype(dir_entry.file_type).expect("file type should not be 0x0!"),
                            dir_entry.name(),
                        ) {
                            break;
                        }
                        entry_index += 1;
                    }
                    reply.ok();
                } else {
                    reply.error(EACCES);
                }
            } else {
                reply.error(ENOTDIR);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn access(&mut self, req: &Request<'_>, ino: u64, mask: i32, reply: ReplyEmpty) {
        // mask:
        // - 要么是 libc::F_OK (aka 0), 检查文件是否存在
        // - 要么是 libc::R_OK,libc::W_OK,libc::X_OK (aka 4/2/1) 构成的 bitmask, 检查是否有对应权限
        debug!("Filesystem::getattr(ino: {}, mask: {})", ino, mask);

        if let Some(inode) = self.get_inode(ino as usize) {
            if mask == libc::F_OK // 只要检查是否存在
                || check_access(req.uid(), req.gid(), inode.uid, inode.gid, inode.mode, mask)
            // 需要检查 rwx 权限
            {
                reply.ok();
            } else {
                reply.error(EACCES);
            }
        } else {
            reply.error(ENOENT);
        }
    }

    fn lseek(
        &mut self,
        _req: &Request<'_>,
        ino: u64,
        fh: u64,
        offset: i64,
        whence: i32,
        reply: ReplyLseek,
    ) {
        reply.error(ENOSYS);
    }
}