use anyhow::Result;
use fuse_backend_rs::abi::fuse_abi::{stat64, statvfs64, FsOptions, OpenOptions};
use fuse_backend_rs::api::filesystem::{Context, DirEntry, Entry, FileSystem, ZeroCopyWriter};
use std::collections::HashMap;
use std::ffi::CStr;
use std::fs::File;
use std::io::Read;
use std::os::unix::io::{AsRawFd, FromRawFd};
use std::sync::{Arc, RwLock};
use std::time::{Duration, SystemTime};

use super::cache::ThreadSafeCache;
use super::db::DbManager;

const TTL: Duration = Duration::from_secs(1);
const READ_CHUNK_SIZE: usize = 524288; // 512KB

pub struct MarkBaseFs {
    db: Arc<DbManager>,
    cache: Arc<ThreadSafeCache>,
    inode_map: RwLock<HashMap<u64, String>>,
    next_inode: RwLock<u64>,
}

impl MarkBaseFs {
    pub fn new(db_path: &str, tree_type: &str) -> Result<Self> {
        let db = DbManager::open(db_path, tree_type)?;
        let cache = ThreadSafeCache::new();

        Ok(Self {
            db: Arc::new(db),
            cache: Arc::new(cache),
            inode_map: RwLock::new(HashMap::new()),
            next_inode: RwLock::new(2),
        })
    }

    fn find_node_id_by_inode(&self, ino: u64) -> Option<String> {
        self.inode_map.read().unwrap().get(&ino).cloned()
    }

    fn get_or_create_inode(&self, node_id: &str) -> u64 {
        let map = self.inode_map.read().unwrap();
        for (ino, id) in &*map {
            if id == node_id {
                return *ino;
            }
        }
        drop(map);

        let mut next = self.next_inode.write().unwrap();
        let ino = *next;
        *next += 1;

        let mut map = self.inode_map.write().unwrap();
        map.insert(ino, node_id.to_string());
        ino
    }

    fn make_stat64(node_type: &str, file_size: u64) -> stat64 {
        let mut st = unsafe { std::mem::zeroed::<stat64>() };
        st.st_ino = 0;
        st.st_mode = if node_type == "folder" { 0o755 } else { 0o644 };
        st.st_nlink = if node_type == "folder" { 2 } else { 1 };
        st.st_uid = 501;
        st.st_gid = 20;
        st.st_size = file_size as i64;
        st.st_blocks = file_size.div_ceil(512) as i64;
        st.st_blksize = 4096;

        let now = SystemTime::now();
        st.st_atime = now
            .duration_since(SystemTime::UNIX_EPOCH)
            .unwrap()
            .as_secs() as i64;
        st.st_mtime = st.st_atime;
        st.st_ctime = st.st_atime;

        st
    }
}

impl FileSystem for MarkBaseFs {
    type Inode = u64;
    type Handle = u64;

    fn init(&self, capable: FsOptions) -> std::io::Result<FsOptions> {
        Ok(capable)
    }

    fn lookup(&self, _ctx: &Context, parent: Self::Inode, name: &CStr) -> std::io::Result<Entry> {
        let name_str = name.to_string_lossy();

        let node_id = if parent == 1 {
            self.db
                .find_node_id(&format!("/{}", name_str))
                .ok()
                .flatten()
        } else {
            let parent_id = self.find_node_id_by_inode(parent);
            match parent_id {
                Some(pid) => self
                    .db
                    .find_node_id_by_parent(&pid, &name_str)
                    .ok()
                    .flatten(),
                None => None,
            }
        };

        match node_id {
            Some(id) => {
                let info = self.db.get_node_info(&id);
                match info {
                    Ok(Some((node_type, file_size))) => {
                        let ino = self.get_or_create_inode(&id);
                        let attr = MarkBaseFs::make_stat64(&node_type, file_size);

                        Ok(Entry {
                            inode: ino,
                            generation: 0,
                            attr,
                            attr_flags: 0,
                            attr_timeout: TTL,
                            entry_timeout: TTL,
                        })
                    }
                    _ => Err(std::io::Error::from_raw_os_error(libc::ENOENT)),
                }
            }
            None => Err(std::io::Error::from_raw_os_error(libc::ENOENT)),
        }
    }

    fn forget(&self, _ctx: &Context, inode: Self::Inode, _count: u64) {
        let mut map = self.inode_map.write().unwrap();
        map.remove(&inode);
    }

    fn getattr(
        &self,
        _ctx: &Context,
        inode: Self::Inode,
        _handle: Option<Self::Handle>,
    ) -> std::io::Result<(stat64, Duration)> {
        if inode == 1 {
            let attr = MarkBaseFs::make_stat64("folder", 0);
            return Ok((attr, TTL));
        }

        let node_id = self.find_node_id_by_inode(inode);
        match node_id {
            Some(id) => {
                let info = self.db.get_node_info(&id);
                match info {
                    Ok(Some((node_type, file_size))) => {
                        let attr = MarkBaseFs::make_stat64(&node_type, file_size);
                        Ok((attr, TTL))
                    }
                    _ => Err(std::io::Error::from_raw_os_error(libc::ENOENT)),
                }
            }
            None => Err(std::io::Error::from_raw_os_error(libc::ENOENT)),
        }
    }

    fn open(
        &self,
        _ctx: &Context,
        inode: Self::Inode,
        _flags: u32,
        _fuse_flags: u32,
    ) -> std::io::Result<(Option<Self::Handle>, OpenOptions, Option<u32>)> {
        Ok((Some(inode), OpenOptions::empty(), None))
    }

    fn read(
        &self,
        _ctx: &Context,
        inode: Self::Inode,
        _handle: Self::Handle,
        w: &mut dyn ZeroCopyWriter,
        size: u32,
        offset: u64,
        _lock_owner: Option<u64>,
        _flags: u32,
    ) -> std::io::Result<usize> {
        let node_id = self.find_node_id_by_inode(inode);
        match node_id {
            Some(id) => {
                let file_path = self.db.get_file_path(&id);
                match file_path {
                    Ok(Some(fp)) => {
                        let file = File::open(&fp)?;
                        let fd = file.as_raw_fd();
                        let f = unsafe { File::from_raw_fd(fd) };
                        let mut f = std::mem::ManuallyDrop::new(f);

                        w.write_from(&mut *f, size as usize, offset)
                    }
                    _ => Err(std::io::Error::from_raw_os_error(libc::ENOENT)),
                }
            }
            None => Err(std::io::Error::from_raw_os_error(libc::ENOENT)),
        }
    }

    fn release(
        &self,
        _ctx: &Context,
        _inode: Self::Inode,
        _flags: u32,
        _handle: Self::Handle,
        _flush: bool,
        _flock_release: bool,
        _lock_owner: Option<u64>,
    ) -> std::io::Result<()> {
        Ok(())
    }

    fn opendir(
        &self,
        _ctx: &Context,
        inode: Self::Inode,
        _flags: u32,
    ) -> std::io::Result<(Option<Self::Handle>, OpenOptions)> {
        Ok((Some(inode), OpenOptions::empty()))
    }

    fn readdir(
        &self,
        _ctx: &Context,
        inode: Self::Inode,
        _handle: Self::Handle,
        _size: u32,
        offset: u64,
        add_entry: &mut dyn FnMut(DirEntry) -> std::io::Result<usize>,
    ) -> std::io::Result<()> {
        if offset == 0 {
            add_entry(DirEntry {
                name: b".\0",
                ino: inode,
                offset: 1,
                type_: libc::S_IFDIR as u32,
            })?;

            add_entry(DirEntry {
                name: b"..\0",
                ino: 1,
                offset: 2,
                type_: libc::S_IFDIR as u32,
            })?;
        }

        Ok(())
    }

    fn releasedir(
        &self,
        _ctx: &Context,
        _inode: Self::Inode,
        _flags: u32,
        _handle: Self::Handle,
    ) -> std::io::Result<()> {
        Ok(())
    }

    fn statfs(&self, _ctx: &Context, _inode: Self::Inode) -> std::io::Result<statvfs64> {
        let mut st = unsafe { std::mem::zeroed::<statvfs64>() };
        st.f_bsize = 4096;
        st.f_blocks = 1000000;
        st.f_bfree = 500000;
        st.f_bavail = 500000;
        st.f_files = 1000;
        st.f_ffree = 500;
        st.f_favail = 500;
        st.f_namemax = 255;
        Ok(st)
    }
}