use std::collections::HashMap;
use std::sync::Mutex;
use std::time::SystemTime;

use async_trait::async_trait;
use nfsserve::nfs::*;
use nfsserve::vfs::{DirEntry, NFSFileSystem, ReadDirResult, VFSCapabilities};

use crate::nfs::markbase_fs::MarkBaseFS;

pub struct MarkBaseNFSBackend {
    fs: MarkBaseFS,
    id_map: Mutex<HashMap<u64, String>>,      // fileid -> node_id
    reverse_map: Mutex<HashMap<String, u64>>, // node_id -> fileid
    next_id: Mutex<u64>,
}

impl MarkBaseNFSBackend {
    pub fn new(user_id: String, db_path: std::path::PathBuf) -> anyhow::Result<Self> {
        let fs = MarkBaseFS::new(user_id, db_path)?;

        Ok(MarkBaseNFSBackend {
            fs,
            id_map: Mutex::new(HashMap::new()),
            reverse_map: Mutex::new(HashMap::new()),
            next_id: Mutex::new(2), // 1 is root
        })
    }

    fn allocate_id(&self, node_id: &str) -> u64 {
        let mut reverse_map = self.reverse_map.lock().unwrap();

        if let Some(id) = reverse_map.get(node_id) {
            return *id;
        }

        let mut next_id = self.next_id.lock().unwrap();
        let id = *next_id;
        *next_id += 1;

        reverse_map.insert(node_id.to_string(), id);
        self.id_map.lock().unwrap().insert(id, node_id.to_string());

        id
    }

    fn get_node_id(&self, fileid: u64) -> Option<String> {
        self.id_map.lock().unwrap().get(&fileid).cloned()
    }

    fn get_fileid_from_node(&self, node_id: &str) -> u64 {
        self.reverse_map
            .lock()
            .unwrap()
            .get(node_id)
            .copied()
            .unwrap_or_else(|| self.allocate_id(node_id))
    }
}

#[async_trait]
impl NFSFileSystem for MarkBaseNFSBackend {
    fn capabilities(&self) -> VFSCapabilities {
        VFSCapabilities::ReadOnly
    }

    fn root_dir(&self) -> fileid3 {
        1
    }

    async fn lookup(&self, dirid: fileid3, filename: &filename3) -> Result<fileid3, nfsstat3> {
        let dir_node_id = if dirid == 1 {
            "root".to_string()
        } else {
            self.get_node_id(dirid).ok_or(nfsstat3::NFS3ERR_STALE)?
        };

        let filename_str = String::from_utf8_lossy(filename).to_string();

        let conn = self
            .fs
            .conn
            .lock()
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?;

        let query = if dir_node_id == "root" {
            "SELECT node_id FROM file_nodes WHERE parent_id IS NULL AND label = ?1"
        } else {
            "SELECT node_id FROM file_nodes WHERE parent_id = ?1 AND label = ?2"
        };

        let node_id: String = if dir_node_id == "root" {
            conn.query_row(query, [&filename_str], |row| row.get(0))
                .map_err(|_| nfsstat3::NFS3ERR_NOENT)?
        } else {
            conn.query_row(query, [dir_node_id, filename_str], |row| row.get(0))
                .map_err(|_| nfsstat3::NFS3ERR_NOENT)?
        };

        Ok(self.get_fileid_from_node(&node_id))
    }

    async fn getattr(&self, id: fileid3) -> Result<fattr3, nfsstat3> {
        if id == 1 {
            return Ok(fattr3 {
                ftype: ftype3::NF3DIR,
                mode: 0o755,
                nlink: 1,
                uid: 0,
                gid: 0,
                size: 0,
                used: 0,
                rdev: specdata3 {
                    specdata1: 0,
                    specdata2: 0,
                },
                fsid: 0,
                fileid: 1,
                atime: nfstime3 {
                    seconds: 0,
                    nseconds: 0,
                },
                mtime: nfstime3 {
                    seconds: 0,
                    nseconds: 0,
                },
                ctime: nfstime3 {
                    seconds: 0,
                    nseconds: 0,
                },
            });
        }

        let node_id = self.get_node_id(id).ok_or(nfsstat3::NFS3ERR_STALE)?;

        let conn = self
            .fs
            .conn
            .lock()
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?;

        let (node_type, file_size): (String, i64) = conn
            .query_row(
                "SELECT node_type, file_size FROM file_nodes WHERE node_id = ?1",
                [&node_id],
                |row| Ok((row.get::<_, String>(0)?, row.get::<_, i64>(1)?)),
            )
            .map_err(|_| nfsstat3::NFS3ERR_NOENT)?;

        let type_ = if node_type == "folder" {
            ftype3::NF3DIR
        } else {
            ftype3::NF3REG
        };

        let now = SystemTime::now()
            .duration_since(SystemTime::UNIX_EPOCH)
            .unwrap()
            .as_secs();

        Ok(fattr3 {
            ftype: type_,
            mode: if node_type == "folder" { 0o755 } else { 0o644 },
            nlink: 1,
            uid: 0,
            gid: 0,
            size: file_size as u64,
            used: file_size as u64,
            rdev: specdata3 {
                specdata1: 0,
                specdata2: 0,
            },
            fsid: 0,
            fileid: id,
            atime: nfstime3 {
                seconds: now as u32,
                nseconds: 0,
            },
            mtime: nfstime3 {
                seconds: now as u32,
                nseconds: 0,
            },
            ctime: nfstime3 {
                seconds: now as u32,
                nseconds: 0,
            },
        })
    }

    async fn setattr(&self, _id: fileid3, _setattr: sattr3) -> Result<fattr3, nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn read(
        &self,
        id: fileid3,
        offset: u64,
        count: u32,
    ) -> Result<(Vec<u8>, bool), nfsstat3> {
        let node_id = self.get_node_id(id).ok_or(nfsstat3::NFS3ERR_STALE)?;

        let conn = self
            .fs
            .conn
            .lock()
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?;

        let aliases_json: String = conn
            .query_row(
                "SELECT aliases_json FROM file_nodes WHERE node_id = ?1",
                [&node_id],
                |row| row.get(0),
            )
            .map_err(|_| nfsstat3::NFS3ERR_NOENT)?;

        let aliases: serde_json::Value =
            serde_json::from_str(&aliases_json).map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?;

        let file_path = aliases["path"].as_str().ok_or(nfsstat3::NFS3ERR_NOENT)?;

        let file_data = std::fs::read(file_path).map_err(|_| nfsstat3::NFS3ERR_IO)?;

        let file_size = file_data.len() as u64;
        let start = offset.min(file_size) as usize;
        let end = (offset + count as u64).min(file_size) as usize;

        let data = file_data[start..end].to_vec();
        let eof = end >= file_size as usize;

        Ok((data, eof))
    }

    async fn write(&self, _id: fileid3, _offset: u64, _data: &[u8]) -> Result<fattr3, nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn create(
        &self,
        _dirid: fileid3,
        _filename: &filename3,
        _attr: sattr3,
    ) -> Result<(fileid3, fattr3), nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn create_exclusive(
        &self,
        _dirid: fileid3,
        _filename: &filename3,
    ) -> Result<fileid3, nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn mkdir(
        &self,
        _dirid: fileid3,
        _dirname: &filename3,
    ) -> Result<(fileid3, fattr3), nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn remove(&self, _dirid: fileid3, _filename: &filename3) -> Result<(), nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn rename(
        &self,
        _from_dirid: fileid3,
        _from_filename: &filename3,
        _to_dirid: fileid3,
        _to_filename: &filename3,
    ) -> Result<(), nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn readdir(
        &self,
        dirid: fileid3,
        start_after: fileid3,
        max_entries: usize,
    ) -> Result<ReadDirResult, nfsstat3> {
        let dir_node_id = if dirid == 1 {
            "root".to_string()
        } else {
            self.get_node_id(dirid).ok_or(nfsstat3::NFS3ERR_STALE)?
        };

        let conn = self
            .fs
            .conn
            .lock()
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?;

        let query = if dir_node_id == "root" {
            "SELECT node_id, label, node_type, file_size FROM file_nodes WHERE parent_id IS NULL"
        } else {
            "SELECT node_id, label, node_type, file_size FROM file_nodes WHERE parent_id = ?1"
        };

        let mut stmt = conn
            .prepare(query)
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?;

        let rows: Vec<(String, String, String, Option<i64>)> = if dir_node_id == "root" {
            stmt.query_map([], |row| {
                row.get::<_, String>(0).and_then(|node_id| {
                    row.get::<_, String>(1).and_then(|label| {
                        row.get::<_, String>(2).and_then(|node_type| {
                            row.get::<_, Option<i64>>(3)
                                .map(|file_size| (node_id, label, node_type, file_size))
                        })
                    })
                })
            })
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?
            .collect::<Result<Vec<_>, _>>()
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?
        } else {
            stmt.query_map([&dir_node_id.as_str()], |row| {
                row.get::<_, String>(0).and_then(|node_id| {
                    row.get::<_, String>(1).and_then(|label| {
                        row.get::<_, String>(2).and_then(|node_type| {
                            row.get::<_, Option<i64>>(3)
                                .map(|file_size| (node_id, label, node_type, file_size))
                        })
                    })
                })
            })
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?
            .collect::<Result<Vec<_>, _>>()
            .map_err(|_| nfsstat3::NFS3ERR_SERVERFAULT)?
        };

        let mut entries: Vec<DirEntry> = Vec::new();
        let mut started = start_after == 0;

        for row in rows {
            let (node_id, label, node_type, file_size_opt) = row;
            let file_size = file_size_opt.unwrap_or(0);
            let fileid = self.get_fileid_from_node(&node_id);

            if !started
                && fileid == start_after {
                    started = true;
                    continue;
                }

            if started && entries.len() < max_entries {
                let attr = fattr3 {
                    ftype: if node_type == "folder" {
                        ftype3::NF3DIR
                    } else {
                        ftype3::NF3REG
                    },
                    mode: if node_type == "folder" { 0o755 } else { 0o644 },
                    nlink: 1,
                    uid: 0,
                    gid: 0,
                    size: file_size as u64,
                    used: file_size as u64,
                    rdev: specdata3 {
                        specdata1: 0,
                        specdata2: 0,
                    },
                    fsid: 0,
                    fileid,
                    atime: nfstime3 {
                        seconds: 0,
                        nseconds: 0,
                    },
                    mtime: nfstime3 {
                        seconds: 0,
                        nseconds: 0,
                    },
                    ctime: nfstime3 {
                        seconds: 0,
                        nseconds: 0,
                    },
                };

                entries.push(DirEntry {
                    fileid,
                    name: nfsserve::nfs::nfsstring(label.into_bytes()),
                    attr,
                });
            }
        }

        Ok(ReadDirResult { entries, end: true })
    }

    async fn symlink(
        &self,
        _dirid: fileid3,
        _linkname: &filename3,
        _symlink: &nfspath3,
        _attr: &sattr3,
    ) -> Result<(fileid3, fattr3), nfsstat3> {
        Err(nfsstat3::NFS3ERR_ROFS)
    }

    async fn readlink(&self, _id: fileid3) -> Result<nfspath3, nfsstat3> {
        Err(nfsstat3::NFS3ERR_NOTSUPP)
    }
}