use crate::block_device::BLOCK_SIZE;
use crate::disk::inode::InodeMode;
use crate::utils::make_fileattr;
use crate::{utils, AyaFS, TTL};
use fuser::{
    FileAttr, FileType, Filesystem, KernelConfig, ReplyAttr, ReplyData, ReplyDirectory, ReplyEmpty,
    ReplyEntry, ReplyLseek, ReplyWrite, Request, TimeOrNow,
};
use libc::{c_int, ENAMETOOLONG, ENOENT, ENOSPC, ENOSYS, ENOTDIR};
use log::debug;
use std::ffi::OsStr;
use std::os::unix::ffi::OsStrExt;
use std::time::SystemTime;
use users::{get_current_gid, get_current_uid};

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

    fn destroy(&mut self) {
        debug!("Filesystem::destroy()");
    }

    fn lookup(&mut self, _req: &Request<'_>, parent: u64, name: &OsStr, reply: ReplyEntry) {
        let parent = parent as usize;
        if let Some(inode) = self.get_inode(parent) {
            // debug!("{:?}", inode);
        }
        // if self.inode_active(parent) {
        //     let (block, offset) = self.locate_inode(parent);
        //     let inode = self.get_inode(block, offset);
        //     debug!("{:?}", inode);
        // }
        reply.error(ENOENT);
    }

    fn forget(&mut self, _req: &Request<'_>, _ino: u64, _nlookup: u64) {
        debug!("Filesystem::forget()");
        todo!("This is a dumb implementation")
    }

    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) {
            let attr = FileAttr {
                ino,
                size: inode.size as u64,
                blocks: inode.n_blocks as u64,
                atime: utils::to_systime(inode.atime),
                mtime: utils::to_systime(inode.mtime),
                ctime: utils::to_systime(inode.ctime),
                crtime: utils::to_systime(inode.crtime),
                kind: inode.mode.into(),
                perm: inode.mode.perm(),
                nlink: inode.n_links as u32,
                uid: inode.uid,
                gid: inode.gid,
                rdev: 0,
                blksize: BLOCK_SIZE as u32,
                flags: inode.flags,
            };
            reply.attr(&TTL, &attr);
        } 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 为什么 setattr 还可以设置 size??
        atime: Option<TimeOrNow>,
        mtime: Option<TimeOrNow>,
        ctime: Option<SystemTime>,
        fh: Option<u64>,
        crtime: Option<SystemTime>,
        _chgtime: Option<SystemTime>,
        _bkuptime: Option<SystemTime>,
        flags: Option<u32>,
        reply: ReplyAttr,
    ) {
        if let Some(inode) = self.get_inode_mut(ino as usize) {
            let mode = mode
                .and_then(|mode_value| {
                    InodeMode::validate(mode_value as u16) // high 16 bit truncated
                })
                .unwrap_or(inode.mode);
            inode.mode = mode;
            // 如果传入的 InodeMode 是合法结果, 那么得到 Some(mode), 否则 None
            // 需要检查权限吗? 如果需要, 如何知道 invoke 这个 callback 的 UID/GID?

            let size = size.unwrap_or(inode.size as u64);
            inode.size = size as u32;
            // TODO 为什么可以设置 size 呢……

            let uid = uid.unwrap_or(inode.uid);
            let gid = gid.unwrap_or(inode.gid);
            inode.uid = uid;
            inode.gid = gid;

            let (atime, atime_inner) = atime
                .map(|atime| {
                    let system_time = match atime {
                        TimeOrNow::SpecificTime(system_time) => system_time,
                        TimeOrNow::Now => SystemTime::now(),
                    };
                    (system_time, utils::from_systime(system_time))
                })
                .unwrap_or((utils::to_systime(inode.atime), inode.atime));
            inode.atime = atime_inner;

            let (mtime, mtime_inner) = mtime
                .map(|mtime| {
                    let system_time = match mtime {
                        TimeOrNow::SpecificTime(system_time) => system_time,
                        TimeOrNow::Now => SystemTime::now(),
                    };
                    (system_time, utils::from_systime(system_time))
                })
                .unwrap_or((utils::to_systime(inode.mtime), inode.mtime));
            inode.mtime = mtime_inner;

            let (ctime, ctime_inner) = ctime
                .map(|ctime| (ctime, utils::from_systime(ctime)))
                .unwrap_or((utils::to_systime(inode.ctime), inode.ctime));
            inode.ctime = ctime_inner;

            let (crtime, crtime_inner) = crtime
                .map(|crtime| (crtime, utils::from_systime(crtime)))
                .unwrap_or((utils::to_systime(inode.crtime), inode.crtime));
            inode.crtime = crtime_inner;

            let flags = flags.unwrap_or(inode.flags);
            inode.flags = flags;

            let attr = FileAttr {
                ino,
                size,
                blocks: inode.n_blocks as u64,
                atime,
                mtime,
                ctime,
                crtime,
                kind: mode.into(),
                perm: mode.perm(),
                nlink: inode.n_links as u32,
                uid,
                gid,
                rdev: 0,
                blksize: BLOCK_SIZE as u32,
                flags,
            };
            reply.attr(&TTL, &attr);
        } else {
            reply.error(ENOSYS);
        }
    }

    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(inode) = self.get_inode(parent as usize) {
            if inode.is_dir() {
                let name = name.as_bytes();
                if name.len() <= 255 {
                    let permissions = (mode & 0o777) as u16;
                    if let Some(inode_index) = self.create_inode(
                        permissions,
                        InodeMode::IFREG,
                        get_current_uid(),
                        get_current_gid(),
                        0,
                    ) {
                        let inode = self.get_inode(inode_index).unwrap();
                        let file_attr = make_fileattr(inode_index, inode);
                        // TODO 把 inode 挂到 parent 下
                        reply.entry(&TTL, &file_attr, 0);
                    } else {
                        // create_inode 失败 -> no enough space
                        reply.error(ENOSPC);
                    }
                } else {
                    // name 长度超过 255 -> File name too long
                    reply.error(ENAMETOOLONG);
                }
            } else {
                // parent 不是 IFDIR -> Not a directory
                reply.error(ENOTDIR);
            }
        } 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(inode) = self.get_inode(parent as usize) {
            if inode.is_dir() {
                let name = name.as_bytes();
                if name.len() <= 255 {
                    let permissions = (mode & 0o777) as u16;
                    if let Some(inode_index) = self.create_inode(
                        permissions,
                        InodeMode::IFDIR,
                        get_current_uid(),
                        get_current_gid(),
                        0,
                    ) {
                        let inode = self.get_inode(inode_index).unwrap();
                        let file_attr = make_fileattr(inode_index, inode);
                        // TODO 把 inode 挂到 parent 下
                        reply.entry(&TTL, &file_attr, 0);
                    } else {
                        // create_inode 失败 -> no enough space
                        reply.error(ENOSPC);
                    }
                } else {
                    // name 长度超过 255 -> File name too long
                    reply.error(ENAMETOOLONG);
                }
            } else {
                // parent 不是 IFDIR -> Not a directory
                reply.error(ENOTDIR);
            }
        } 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) {
            // TODO 找到这个 inode 并且删掉
            reply.ok();
        } 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 readdir(
        &mut self,
        _req: &Request<'_>,
        ino: u64,
        _fh: u64,
        offset: i64,
        mut reply: ReplyDirectory,
    ) {
        if let Some(inode) = self.get_inode(ino as usize) {
        } else {
            reply.error(ENOENT);
        }

        // if ino != 1 {
        //     reply.error(ENOENT);
        //     return;
        // }
        //
        // let entries = vec![
        //     (1, FileType::Directory, "."),
        //     (1, FileType::Directory, ".."),
        //     (2, FileType::RegularFile, "hello.txt"),
        // ];
        //
        // for (i, entry) in entries.into_iter().enumerate().skip(offset as usize) {
        //     // i + 1 means the index of the next entry
        //     if reply.add(entry.0, (i + 1) as i64, entry.1, entry.2) {
        //         break;
        //     }
        // }
        // reply.ok();
    }

    fn access(&mut self, _req: &Request<'_>, ino: u64, mask: i32, reply: ReplyEmpty) {
        debug!("Filesystem::getattr(ino: {}, mask: {})", ino, mask);
        if let Some(inode) = self.get_inode(ino as usize) {
            reply.ok()
        } else {
            reply.error(ENOENT)
        }
    }

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