use std::time::SystemTime;
use std::fs::{File, OpenOptions};
use std::os::unix::fs::OpenOptionsExt;
use std::os::unix::io::AsRawFd;
use std::path::Path;

use anyhow::{bail, format_err, Error};
use endian_trait::Endian;
use nix::fcntl::{fcntl, FcntlArg, OFlag};

use proxmox::{
    sys::error::SysResult,
    tools::io::ReadExt,
};

use crate::{
    api2::types::{
        MamAttribute,
    },
    tape::{
        BlockRead,
        BlockReadStatus,
        BlockWrite,
        file_formats::{
            BlockedWriter,
            BlockedReader,
        },
        drive::{
            TapeAlertFlags,
            Lp17VolumeStatistics,
            read_mam_attributes,
            read_tape_alert_flags,
            read_volume_statistics,
            set_encryption,
        },
    },
    tools::sgutils2::{
        SgRaw,
        SenseInfo,
        ScsiError,
        InquiryInfo,
        scsi_inquiry,
    },
};

#[repr(C, packed)]
#[derive(Endian, Debug, Copy, Clone)]
pub struct ReadPositionLongPage {
    flags: u8,
    reserved: [u8;3],
    partition_number: u32,
    pub logical_object_number: u64,
    pub logical_file_id: u64,
    obsolete: [u8;8],
}

pub struct SgTape {
    file: File,
}

impl SgTape {

    const SCSI_TAPE_DEFAULT_TIMEOUT: usize = 60*2; // 2 minutes

    /// Create a new instance
    ///
    /// Uses scsi_inquiry to check the device type.
    pub fn new(mut file: File) -> Result<Self, Error> {

        let info = scsi_inquiry(&mut file)?;

        if info.peripheral_type != 1 {
            bail!("not a tape device (peripheral_type = {})", info.peripheral_type);
        }
        Ok(Self { file })
    }

    pub fn open<P: AsRef<Path>>(path: P) -> Result<SgTape, Error> {
        // do not wait for media, use O_NONBLOCK
        let file = OpenOptions::new()
            .read(true)
            .write(true)
            .custom_flags(libc::O_NONBLOCK)
            .open(path)?;

        // then clear O_NONBLOCK
        let flags = fcntl(file.as_raw_fd(), FcntlArg::F_GETFL)
            .into_io_result()?;

        let mut flags = OFlag::from_bits_truncate(flags);
        flags.remove(OFlag::O_NONBLOCK);

        fcntl(file.as_raw_fd(), FcntlArg::F_SETFL(flags))
            .into_io_result()?;

        Self::new(file)
    }

    pub fn inquiry(&mut self) -> Result<InquiryInfo, Error> {
        scsi_inquiry(&mut self.file)
    }

    /// Erase medium.
    ///
    /// EOD is written at the current position, which marks it as end
    /// of data. After the command is successfully completed, the
    /// drive is positioned immediately before End Of Data (not End Of
    /// Tape).
    pub fn erase_media(&mut self, fast: bool) -> Result<(), Error> {
        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.push(0x19);
        if fast {
            cmd.push(0); // LONG=0
        } else {
            cmd.push(1); // LONG=1
        }
        cmd.extend(&[0, 0, 0, 0]);

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("erase failed - {}", err))?;

        Ok(())
    }

    /// Format media, single partition
    pub fn format_media(&mut self, fast: bool) -> Result<(), Error> {

        self.rewind()?;

        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.extend(&[0x04, 0, 0, 0, 0, 0]);

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("erase failed - {}", err))?;

        if !fast {
            self.erase_media(false)?; // overwrite everything
        }

        Ok(())
    }

    pub fn rewind(&mut self) -> Result<(), Error> {

        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.extend(&[0x01, 0, 0, 0, 0, 0]); // REWIND

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("rewind failed - {}", err))?;

        Ok(())
    }

    pub fn position(&mut self) -> Result<ReadPositionLongPage, Error> {

        let expected_size = std::mem::size_of::<ReadPositionLongPage>();

        let mut sg_raw = SgRaw::new(&mut self.file, 32)?;
        sg_raw.set_timeout(30); // use short timeout
        let mut cmd = Vec::new();
        cmd.extend(&[0x34, 0x06, 0, 0, 0, 0, 0, 0, 0, 0]); // READ POSITION LONG FORM

        let data = sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("read position failed - {}", err))?;

        let page = proxmox::try_block!({
            if data.len() != expected_size {
                bail!("got unexpected data len ({} != {}", data.len(), expected_size);
            }

            let mut reader = &data[..];

            let page: ReadPositionLongPage = unsafe { reader.read_be_value()? };

            Ok(page)
        }).map_err(|err: Error| format_err!("decode position page failed - {}", err))?;

        if page.partition_number != 0 {
            bail!("detecthed partitioned tape - not supported");
        }

        println!("DATA: {:?}", page);

        Ok(page)
    }

    pub fn current_file_number(&mut self) -> Result<u64, Error> {
        let position = self.position()?;
        Ok(position.logical_file_id)
    }

    pub fn locate(&mut self) ->  Result<(), Error> {
        // fixme: impl LOCATE
        unimplemented!();
    }

    pub fn move_to_eom(&mut self) ->  Result<(), Error> {
        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.extend(&[0x11, 0x03, 0, 0, 0, 0]); // SPACE(6) move to EOD

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("move to EOD failed - {}", err))?;

        Ok(())
    }

    pub fn space_filemarks(&mut self, count: isize) ->  Result<(), Error> {
        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();

        // Use short command if possible (supported by all drives)
        if (count <= 0x7fffff) && (count > -0x7fffff) {
            cmd.extend(&[0x11, 0x01]); // SPACE(6) with filemarks
            cmd.push(((count >> 16) & 0xff) as u8);
            cmd.push(((count >> 8) & 0xff) as u8);
            cmd.push((count & 0xff) as u8);
            cmd.push(0); //control byte
        } else {

            cmd.extend(&[0x91, 0x01, 0, 0]); // SPACE(16) with filemarks
            let count: i64 = count as i64;
            cmd.extend(&count.to_be_bytes());
            cmd.extend(&[0, 0, 0, 0]);
        }

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("space filemarks failed - {}", err))?;

        Ok(())
    }

    pub fn eject(&mut self) ->  Result<(), Error> {
        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.extend(&[0x1B, 0, 0, 0, 0, 0]); // LODA/UNLOAD HOLD=0, LOAD=0

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("eject failed - {}", err))?;

        Ok(())
    }

    pub fn load(&mut self) ->  Result<(), Error> {
        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.extend(&[0x1B, 0, 0, 0, 0b0000_0001, 0]); // LODA/UNLOAD HOLD=0, LOAD=1

        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("load media failed - {}", err))?;

        Ok(())
    }

    pub fn write_filemarks(
        &mut self,
        count: usize,
        immediate: bool,
    ) ->  Result<(), std::io::Error> {

        if count > 255 {
            proxmox::io_bail!("write_filemarks failed: got strange count '{}'", count);
        }

        let mut sg_raw = SgRaw::new(&mut self.file, 16)
            .map_err(|err| proxmox::io_format_err!("write_filemarks failed (alloc) - {}", err))?;

        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.push(0x10);
        if immediate {
            cmd.push(1); // IMMED=1
        } else {
            cmd.push(0); // IMMED=0
        }
        cmd.extend(&[0, 0, count as u8]); // COUNT
        cmd.push(0); // control byte

        sg_raw.do_command(&cmd)
            .map_err(|err| proxmox::io_format_err!("write filemark failed - {}", err))?;

        Ok(())
    }

    // Flush tape buffers (WEOF with count 0 => flush)
    pub fn sync(&mut self) -> Result<(), std::io::Error> {
        self.write_filemarks(0, false)?;
        Ok(())
    }

    pub fn test_unit_ready(&mut self) -> Result<bool, Error> {

        let mut sg_raw = SgRaw::new(&mut self.file, 16)?;
        sg_raw.set_timeout(30); // use short timeout
        let mut cmd = Vec::new();
        cmd.extend(&[0x00, 0, 0, 0, 0, 0]); // TEST UNIT READY

        // fixme: check sense
        sg_raw.do_command(&cmd)
            .map_err(|err| format_err!("unit not ready - {}", err))?;

        Ok(true)

    }

    pub fn wait_until_ready(&mut self) -> Result<(), Error> {

        let start = SystemTime::now();
        let max_wait = std::time::Duration::new(Self::SCSI_TAPE_DEFAULT_TIMEOUT as u64, 0);

        loop {
            match self.test_unit_ready() {
                Ok(true) => return Ok(()),
                _ => {
                    std::thread::sleep(std::time::Duration::new(1, 0));
                    if start.elapsed()? > max_wait {
                        bail!("wait_until_ready failed - got timeout");
                    }
                }
            }
        }
    }

    /// Read Tape Alert Flags
    pub fn tape_alert_flags(&mut self) -> Result<TapeAlertFlags, Error> {
        read_tape_alert_flags(&mut self.file)
    }

    /// Read Cartridge Memory (MAM Attributes)
    pub fn cartridge_memory(&mut self) -> Result<Vec<MamAttribute>, Error> {
        read_mam_attributes(&mut self.file)
    }

    /// Read Volume Statistics
    pub fn volume_statistics(&mut self) -> Result<Lp17VolumeStatistics, Error> {
        return read_volume_statistics(&mut self.file);
    }

    pub fn set_encryption(
        &mut self,
        key: Option<[u8; 32]>,
    ) -> Result<(), Error> {
        set_encryption(&mut self.file, key)
    }

    // Note: use alloc_page_aligned_buffer to alloc data transfer buffer
    //
    // Returns true if the drive reached the Logical End Of Media (early warning)
    fn write_block(&mut self, data: &[u8]) -> Result<bool, std::io::Error> {

        let transfer_len = data.len();

        if transfer_len > 0xFFFFFF {
           proxmox::io_bail!("write failed - data too large");
        }

        let mut sg_raw = SgRaw::new(&mut self.file, 0)
            .unwrap(); // cannot fail with size 0

        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.push(0x0A);  // WRITE
        cmd.push(0x00); // VARIABLE SIZED BLOCKS
        cmd.push(((transfer_len >> 16) & 0xff) as u8);
        cmd.push(((transfer_len >> 8) & 0xff) as u8);
        cmd.push((transfer_len & 0xff) as u8);
        cmd.push(0); // control byte

        //println!("WRITE {:?}", cmd);
        //println!("WRITE {:?}", data);

        sg_raw.do_out_command(&cmd, data)
            .map_err(|err| proxmox::io_format_err!("write failed - {}", err))?;

        // fixme: LEOM?

        Ok(false)
    }

    fn read_block(&mut self, buffer: &mut [u8]) -> Result<BlockReadStatus, std::io::Error> {
        let transfer_len = buffer.len();

        if transfer_len > 0xFFFFFF {
            proxmox::io_bail!("read failed - buffer too large");
        }

        let mut sg_raw = SgRaw::new(&mut self.file, 0)
            .unwrap(); // cannot fail with size 0

        sg_raw.set_timeout(Self::SCSI_TAPE_DEFAULT_TIMEOUT);
        let mut cmd = Vec::new();
        cmd.push(0x08); // READ
        cmd.push(0x02); // VARIABLE SIZED BLOCKS, SILI=1
        //cmd.push(0x00); // VARIABLE SIZED BLOCKS, SILI=0
        cmd.push(((transfer_len >> 16) & 0xff) as u8);
        cmd.push(((transfer_len >> 8) & 0xff) as u8);
        cmd.push((transfer_len & 0xff) as u8);
        cmd.push(0); // control byte

        let data = match sg_raw.do_in_command(&cmd, buffer) {
            Ok(data) => data,
            Err(ScsiError::Sense(SenseInfo { sense_key: 0, asc: 0, ascq: 1 })) => {
                return Ok(BlockReadStatus::EndOfFile);
            }
            Err(ScsiError::Sense(SenseInfo { sense_key: 8, asc: 0, ascq: 5 })) => {
                return Ok(BlockReadStatus::EndOfStream);
            }
            Err(err) => {
                println!("READ ERR {:?}", err);
                proxmox::io_bail!("read failed - {}", err);
            }
        };

        if data.len() != transfer_len {
            proxmox::io_bail!("read failed - unexpected block len ({} != {})", data.len(), buffer.len())
        }

        Ok(BlockReadStatus::Ok(transfer_len))
    }

    pub fn open_writer(&mut self) -> BlockedWriter<SgTapeWriter> {
        let writer = SgTapeWriter::new(self);
        BlockedWriter::new(writer)
    }

    pub fn open_reader(&mut self) -> Result<Option<BlockedReader<SgTapeReader>>, std::io::Error> {
        let reader = SgTapeReader::new(self);
        match BlockedReader::open(reader)? {
            Some(reader) => Ok(Some(reader)),
            None => Ok(None),
        }
    }
}

pub struct SgTapeReader<'a> {
    sg_tape: &'a mut SgTape,
}

impl <'a> SgTapeReader<'a> {

    pub fn new(sg_tape: &'a mut SgTape) -> Self {
        Self { sg_tape }
    }
}

impl <'a> BlockRead for SgTapeReader<'a> {

    fn read_block(&mut self, buffer: &mut [u8]) -> Result<BlockReadStatus, std::io::Error> {
        self.sg_tape.read_block(buffer)
    }
}

pub struct SgTapeWriter<'a> {
    sg_tape: &'a mut SgTape,
    _leom_sent: bool,
}

impl <'a> SgTapeWriter<'a> {

    pub fn new(sg_tape: &'a mut SgTape) -> Self {
        Self { sg_tape, _leom_sent: false }
    }
}

impl <'a> BlockWrite for SgTapeWriter<'a> {

    fn write_block(&mut self, buffer: &[u8]) -> Result<bool, std::io::Error> {
        self.sg_tape.write_block(buffer)
    }

    fn write_filemark(&mut self) -> Result<(), std::io::Error> {
        self.sg_tape.write_filemarks(1, true)
    }
}