mod dcache;
mod fcache;
mod fh;
mod file;
mod ino;

use self::{dcache::Dcache, fcache::Fcache, fh::FileHandle, file::File, ino::Ino};
use crate::{
    common::{
        mime::{self, MimeType},
        slot_map::SlotMap,
    },
    server::{attrs::Attr, blobref::BlobRef, Server},
};
use fuser::TimeOrNow;
use libc::{EBADF, EEXIST, EFBIG, EINVAL, EIO, ENFILE, ENOENT, O_RDONLY, O_RDWR, O_WRONLY};
use log::{debug, error, warn};
use std::{
    cmp,
    ffi::{c_int, OsStr, OsString},
    io,
    time::{Duration, SystemTime},
};

const GENERATION: u64 = 0;
const CACHE_TTL: Duration = Duration::from_secs(1);

pub struct FileSystem {
    server: Server,
    ino: Ino,
    dcache: Dcache,
    fcache: Fcache,
    // TODO: bcache ino -> blobref
    handles: SlotMap<FileHandle>,
}

impl FileSystem {
    pub fn new(server: Server) -> Self {
        let ino = Ino::new();

        let mut fs = FileSystem {
            server,
            ino,
            dcache: Dcache::new(),
            fcache: Fcache::new(),
            handles: SlotMap::new(),
        };

        fs.setup_root();

        fs
    }

    pub fn mount(self, mountpoint: &str) -> io::Result<()> {
        // TODO: Ignore permissions
        let opts = &[
            fuser::MountOption::AllowOther,
            fuser::MountOption::AutoUnmount,
            fuser::MountOption::NoExec,
        ];

        fuser::mount2(self, mountpoint, opts)
    }

    fn setup_root(&mut self) {
        let root_ino = self.ino;
        let parent_ino = self.next_ino();

        self.dcache.add_dentry(root_ino, parent_ino);

        let mut root = File::new_directory(root_ino, ".");
        root.set_parent(parent_ino);

        self.fcache.insert(root_ino, root);
        self.fcache
            .insert(parent_ino, File::new_directory(parent_ino, ".."));
    }

    fn next_ino(&mut self) -> Ino {
        *self.ino.next()
    }

    fn empty_handle(&mut self) -> std::io::Result<Option<u64>> {
        Ok(self.handles.insert(FileHandle::empty()?).map(u64::from))
    }
    //
    fn release_handle(&mut self, fh: u64) {
        let fh = u32::try_from(fh).expect("Invalid file handle");
        self.handles.remove(fh);
    }
    //
    fn file_by_name(&self, parent: Ino, name: &OsStr) -> Option<&File> {
        let ino = self.dcache.get_ino(parent, name)?;
        self.fcache.get(*ino)
    }
    //
    //     fn get_blobref_by_name(&self, parent: u64, name: &OsStr) -> Option<BlobRef> {
    //         self.get_by_name(parent, name)
    //             .and_then(|f| f.blobref.clone())
    //     }

    fn get_blobref_by_ino(&self, ino: Ino) -> Option<BlobRef> {
        self.fcache.get(ino).and_then(|f| f.blobref.clone())
    }

    fn get_parent_blobref(&self, file: &File) -> Option<BlobRef> {
        file.parent().and_then(|ino| self.get_blobref_by_ino(ino))
    }

    fn get_parent_blobref_by_ino(&self, ino: Ino) -> Option<BlobRef> {
        self.fcache
            .get(ino)
            .and_then(|f| self.get_parent_blobref(f))
    }
    //
    //     fn remove_from_cache_by_name(&mut self, parent: u64, name: &OsStr) -> Option<u64> {
    //         let ino = self
    //             .dcache
    //             .get_mut(&parent)
    //             .and_then(|xs| xs.remove(name))?;
    //         self.dcache.remove(&ino);
    //         self.fcache.remove(&ino);
    //
    //         Some(ino)
    //     }
}

impl fuser::Filesystem for FileSystem {
    fn init(
        &mut self,
        _req: &fuser::Request<'_>,
        _config: &mut fuser::KernelConfig,
    ) -> Result<(), c_int> {
        Ok(())
    }

    fn lookup(
        &mut self,
        _req: &fuser::Request<'_>,
        parent: u64,
        name: &OsStr,
        reply: fuser::ReplyEntry,
    ) {
        debug!("lookup(parent: {:#x?}, name {:?})", parent, name);

        if let Some(file) = self.file_by_name(parent.into(), name) {
            reply.entry(&CACHE_TTL, &file.attr, 0);
        } else {
            warn!("lookup(parent: {parent:#x?}, name {name:?}): ENOENT");
            reply.error(ENOENT);
        }
    }

    fn getattr(&mut self, _req: &fuser::Request<'_>, ino: u64, reply: fuser::ReplyAttr) {
        debug!("getattr(ino: {:#x?})", ino);

        if let Some(file) = self.fcache.get(ino.into()) {
            reply.attr(&CACHE_TTL, &file.attr);
        } else {
            warn!("getattr(ino: {:#x?}): ENOENT", ino);
            reply.error(ENOENT);
        }
    }

    fn open(&mut self, _req: &fuser::Request<'_>, ino: u64, flags: i32, reply: fuser::ReplyOpen) {
        debug!("open(ino: {ino:#x?}, flags: {flags:b})");

        // For now, we only support read-only, write-only and read-write.
        if flags & 0xf & !(O_RDONLY | O_WRONLY | O_RDWR) != 0 {
            error!("open(ino: {ino:#x?}): EIO: Unsupported mode");
            reply.error(EIO);
            return;
        }

        // File should be cached first (via `readdir`).
        if self.fcache.get_mut(ino.into()).is_none() {
            error!("open(ino: {ino:#x?}): ENOENT");
            reply.error(ENOENT);
            return;
        };

        match self.empty_handle() {
            Ok(Some(fh)) => reply.opened(fh, u32::try_from(flags).expect("Invalid flags")),
            Ok(None) => {
                // No file handle available.
                error!("open(ino: {ino:#x?}): ENFILE");
                reply.error(ENFILE);
            }
            Err(e) => {
                error!("open(ino: {ino:#x?}): EIO: {e}");
                reply.error(EIO);
            }
        }
    }

    fn mkdir(
        &mut self,
        _req: &fuser::Request<'_>,
        parent: u64,
        name: &OsStr,
        mode: u32,
        umask: u32,
        reply: fuser::ReplyEntry,
    ) {
        debug!("mkdir(parent: {parent:#x?}, name: {name:?}, mode: {mode}, umask: {umask:#x?})");

        let parent_blobref = self.get_blobref_by_ino(parent.into());

        let Some(dentry) = self.dcache.get_mut(parent.into()) else {
            warn!("mkdir(parent: {parent:#x?}, name: {name:?}): ENOENT");
            reply.error(ENOENT);
            return;
        };

        self.ino.next();

        if dentry.try_insert(name.into(), self.ino).is_err() {
            self.ino.prev();

            warn!("mkdir(parent: {parent:#x?}, name: {name:?}): EEXIST");
            reply.error(EEXIST);
            return;
        }

        let mut file = File::new_directory(self.ino, name);
        file.set_parent(parent.into());

        let mut attrs = vec![Attr::Mime(MimeType::ApplicationXGroup)];
        if let Some(b) = parent_blobref {
            attrs.push(Attr::Group(b))
        };

        if let Some(name) = name.to_str() {
            attrs.push(Attr::Name(name.to_string()));
        } else {
            warn!("mkdir(parent: {parent:#x?}, name: {name:?}): EINVAL");
            reply.error(EINVAL);
            return;
        }

        let Ok(blobref) = self.server.put_with_attrs(&[] as &[u8], &attrs) else {
            dentry.remove(name);
            warn!("mkdir(parent: {parent:#x?}, name: {name:?}): EIO");
            reply.error(EIO);
            return;
        };

        file.blobref = Some(blobref);
        file.attr.mtime = SystemTime::now();

        reply.entry(&CACHE_TTL, &file.attr, 0);

        self.dcache.add_dentry(self.ino, parent.into());
        self.fcache.insert(self.ino, file);
    }

    fn readdir(
        &mut self,
        _req: &fuser::Request<'_>,
        ino: u64,
        fh: u64,
        offset: i64,
        mut reply: fuser::ReplyDirectory,
    ) {
        debug!("readdir(ino: {ino:#x?}, fh: {fh}, offset: {offset})");

        let offset = usize::try_from(offset).expect("Invalid offset");

        // Load dentry from the index
        // TODO: Move to opendir
        if let Err(e) = load_dentry(
            &self.server,
            &mut self.ino,
            ino.into(),
            &mut self.dcache,
            &mut self.fcache,
        ) {
            error!("readdir(ino: {ino:#x?}, fh: {fh}, offset: {offset}): {e:?}");
            reply.error(e);
            return;
        }

        let Some(dentry) = self.dcache.get(ino.into()) else {
            warn!("readdir(ino: {ino:#x?}, fh: {fh}, offset: {offset}): ENOENT");
            reply.error(ENOENT);
            return;
        };

        for (i, (name, ino)) in dentry.iter().skip(offset).enumerate() {
            let Some(file) = self.fcache.get(*ino) else {
                error!("readdir(ino: {ino:#x?}, fh: {fh}, offset: {offset}): EIO");
                reply.error(EIO);
                return;
            };

            let curr_offset = i64::try_from(offset + i + 1).expect("Too many files in dentry");
            let full = reply.add(file.attr.ino, curr_offset, file.attr.kind, name);
            if full {
                break;
            }
        }

        reply.ok();
    }

    fn create(
        &mut self,
        _req: &fuser::Request<'_>,
        parent: u64,
        name: &std::ffi::OsStr,
        mode: u32,
        umask: u32,
        flags: i32,
        reply: fuser::ReplyCreate,
    ) {
        debug!(
            "create(parent: {:#x?}, name: {:?}, mode: {}, umask: {:#x?}, flags: {:#x?})",
            parent, name, mode, umask, flags
        );

        let ino = self.next_ino();

        match self.dcache.try_insert_name(parent.into(), name.into(), ino) {
            Some(Ok(())) => {
                let mut file = File::new_regular_file(ino, name);
                file.set_parent(parent.into());
                file.attr.flags = u32::try_from(flags).unwrap_or(0);

                match self.empty_handle() {
                    Ok(Some(fh)) => {
                        reply.created(&CACHE_TTL, &file.attr, GENERATION, fh, file.attr.flags);
                        self.fcache.insert(ino, file);
                    }
                    Ok(None) => {
                        error!("create(ino: {ino:#x?}): ENFILE");
                        reply.error(ENFILE);
                    }
                    Err(e) => {
                        error!("create(ino: {ino:#x?}): EIO: {e}");
                        reply.error(EIO);
                    }
                }
            }
            Some(Err(())) => {
                warn!(
                        "create(parent: {:#x?}, name: {:?}, mode: {}, umask: {:#x?}, flags: {:#x?}): EEXIST",
                        parent, name, mode, umask, flags
                    );

                reply.error(EEXIST);
            }
            None => {
                warn!(
                        "create(parent: {:#x?}, name: {:?}, mode: {}, umask: {:#x?}, flags: {:#x?}): ENOENT",
                        parent, name, mode, umask, flags
                    );

                reply.error(ENOENT);
            }
        }
    }

    fn setattr(
        &mut self,
        _req: &fuser::Request<'_>,
        ino: u64,
        mode: Option<u32>,
        uid: Option<u32>,
        gid: Option<u32>,
        size: Option<u64>,
        atime: Option<fuser::TimeOrNow>,
        mtime: Option<fuser::TimeOrNow>,
        ctime: Option<std::time::SystemTime>,
        fh: Option<u64>,
        _crtime: Option<std::time::SystemTime>,
        _chgtime: Option<std::time::SystemTime>,
        _bkuptime: Option<std::time::SystemTime>,
        flags: Option<u32>,
        reply: fuser::ReplyAttr,
    ) {
        debug!(
            "setattr(ino: {:#x?}, mode: {:?}, uid: {:?}, \
                 gid: {:?}, size: {:?}, fh: {:?}, flags: {:?})",
            ino, mode, uid, gid, size, fh, flags
        );

        if let Some(file) = self.fcache.get_mut(ino.into()) {
            if let Some(TimeOrNow::SpecificTime(t)) = atime {
                file.attr.atime = t;
            }
            if let Some(TimeOrNow::SpecificTime(t)) = mtime {
                file.attr.mtime = t;
            }
            file.attr.ctime = ctime.unwrap_or(file.attr.ctime);
            file.attr.size = size.unwrap_or(file.attr.size);
            file.attr.flags = flags.unwrap_or(file.attr.flags);

            reply.attr(&CACHE_TTL, &file.attr);
        } else {
            warn!("setattr(ino: {ino:#x?}): ENOENT");
            reply.error(ENOENT);
        }
    }

    fn flush(
        &mut self,
        _req: &fuser::Request<'_>,
        ino: u64,
        fh: u64,
        lock_owner: u64,
        reply: fuser::ReplyEmpty,
    ) {
        debug!("flush(ino: {ino:#x?}, fh: {fh}, lock_owner: {lock_owner:?})");

        let parent_blobref = self.get_parent_blobref_by_ino(ino.into());

        let Some(file) = self.fcache.get_mut(ino.into()) else {
            warn!("flush(ino: {ino:#x?}): ENOENT");
            reply.error(ENOENT);
            return;
        };

        let fh = u32::try_from(fh).expect("Invalid file handle");
        let Some(handle) = self.handles.get_mut(fh) else {
            warn!("flush(ino: {ino:#x?}): EBADF");
            reply.error(EBADF);
            return;
        };

        if !handle.is_dirty() {
            // Nothing to write
            reply.ok();
            return;
        }

        file.attr.size = handle.buflen() as u64;
        file.attr.mtime = SystemTime::now();

        let mut attrs = vec![Attr::CreatedAt(file.attr.crtime.into())];
        if let Ok(name) = file.name().into_string() {
            if let Some(m) = mime::guess(&name) {
                attrs.push(Attr::Mime(m))
            };
            attrs.push(Attr::Name(name));
        }
        if let Some(b) = parent_blobref {
            attrs.push(Attr::Group(b))
        };

        // TODO: self.server.append if file has a blobref already
        //       -- or self.server.replace depending on whether we're
        //       appending or replacing.
        let Ok(blobref) = self
            .server
            .put_with_attrs(handle.buffer().as_slice(), &attrs)
        else {
            // NOTE: Should we clear the handle on error too?
            //       Unsure if we should be able to retry a flush?
            error!("flush(ino: {ino:#x?}): EIO");
            reply.error(EIO);
            return;
        };

        file.blobref = Some(blobref);
        handle.clear();
        reply.ok();
    }

    fn write(
        &mut self,
        _req: &fuser::Request<'_>,
        ino: u64,
        fh: u64,
        offset: i64,
        data: &[u8],
        write_flags: u32,
        flags: i32,
        lock_owner: Option<u64>,
        reply: fuser::ReplyWrite,
    ) {
        debug!(
                 "write(ino: {ino:#x?}, fh: {fh}, offset: {offset}, size: {}, write_flags: {write_flags:#x?}, flags: {flags:#x?}, lock_owner: {lock_owner:?})",
                 data.len(),
             );

        let size: u32 = data.len().try_into().unwrap_or(0);

        if size < 1 && !data.is_empty() {
            // The block is too big.
            error!(
                "write(ino: {ino:#x?}, offset: {offset}, size: {}): EFBIG",
                data.len()
            );
            reply.error(EFBIG);
            return;
        }

        let fh = u32::try_from(fh).expect("Invalid file handle");
        // TODO: Should auto-flush when necessary
        if let Some(ref mut handle) = self.handles.get_mut(fh) {
            let offset = usize::try_from(offset).expect("Invalid offset");
            // FIXME: Get written size from handle.write result
            if handle.write(data, offset).is_none() {
                error!(
                    "write(ino: {ino:#x?}, offset: {offset}, size: {}): EIO",
                    data.len()
                );
                reply.error(EIO);
                return;
            }

            reply.written(size);
        } else {
            warn!("write(ino: {ino:#x?}): EBADF");
            reply.error(EBADF);
        }
    }

    fn read(
        &mut self,
        _req: &fuser::Request<'_>,
        ino: u64,
        fh: u64,
        offset: i64,
        size: u32,
        flags: i32,
        lock_owner: Option<u64>,
        reply: fuser::ReplyData,
    ) {
        debug!(
            "read(ino: {:#x?}, fh: {}, offset: {}, size: {}, \
                 flags: {:#x?}, lock_owner: {:?})",
            ino, fh, offset, size, flags, lock_owner
        );

        let Some(file) = self.fcache.get(ino.into()) else {
            warn!("read(ino: {ino:#x?}): EBADF");
            reply.error(ENOENT);
            return;
        };

        let fh = u32::try_from(fh).expect("Invalid file handle");
        let Some(handle) = self.handles.get_mut(fh) else {
            warn!("read(ino: {ino:#x?}): EBADF");
            reply.error(EBADF);
            return;
        };

        // TODO: Check if offset > handle.buflen() or file.size()
        let offset = usize::try_from(offset).expect("Invalid offset");

        let Some(ref blobref) = file.blobref else {
            // We haven't flushed the handle yet, but we should still be able to read from it
            reply.data(&handle.read(offset, size as usize));
            return;
        };

        let Ok(bytes) = self.server.read(blobref, offset..(offset + size as usize)) else {
            warn!("read(ino: {ino:#x?}): EIO");
            reply.error(EIO);
            return;
        };

        reply.data(&bytes);
    }

    fn release(
        &mut self,
        _req: &fuser::Request<'_>,
        ino: u64,
        fh: u64,
        _flags: i32,
        _lock_owner: Option<u64>,
        _flush: bool, // TODO: flush if true
        reply: fuser::ReplyEmpty,
    ) {
        debug!("release(ino: {ino:#x?}, fh: {fh})");
        self.release_handle(fh);
        reply.ok();
    }
}

fn load_dentry(
    server: &Server,
    ino: &mut Ino,
    parent_ino: Ino,
    dcache: &mut Dcache,
    fcache: &mut Fcache,
) -> Result<(), c_int> {
    let dentry = dcache.get_mut(parent_ino).ok_or(ENOENT)?;
    if dentry.loaded {
        return Ok(());
    }

    let parent_blobref = fcache
        .get(parent_ino)
        .and_then(|f| f.blobref.clone())
        .map(Attr::Group);

    // TODO: Pass range to `load_dentry`
    let objects = server.list(0..10_000, parent_blobref).map_err(|_| EIO)?;

    let mut dir_inos = Vec::new();
    for object in objects {
        let ino = ino.next();

        let name: OsString = object
            .get_name()
            .unwrap_or(format!(".carton.x-nameless-{ino}"))
            .into();

        let file = if object.is_group() {
            let mut file = File::new_directory(*ino, name.clone());
            file.blobref = Some(object.blobref().clone());
            dir_inos.push(*ino);
            file
        } else {
            let mut file = File::new_regular_file(*ino, name.clone());
            file.blobref = Some(object.blobref().clone());
            file.attr.size = object.size() as u64;
            file
        };

        dentry.insert(name, *ino);
        fcache.insert(*ino, file);
    }
    dentry.loaded = true;

    for dir_ino in &dir_inos {
        dcache.add_dentry(*dir_ino, parent_ino);
    }

    Ok(())
}