use super::copy_range_to_buf;
use super::copy_to_buf;
use crate::emu::Emu;
use crate::TEST_PROGRAM_ELF;
use gdbstub::target;
use gdbstub::target::ext::host_io::FsKind;
use gdbstub::target::ext::host_io::HostIoErrno;
use gdbstub::target::ext::host_io::HostIoError;
use gdbstub::target::ext::host_io::HostIoOpenFlags;
use gdbstub::target::ext::host_io::HostIoOpenMode;
use gdbstub::target::ext::host_io::HostIoResult;
use gdbstub::target::ext::host_io::HostIoStat;
use std::io::Read;
use std::io::Seek;
use std::io::Write;

const FD_RESERVED: u32 = 1;

impl target::ext::host_io::HostIo for Emu {
    #[inline(always)]
    fn support_open(&mut self) -> Option<target::ext::host_io::HostIoOpenOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_close(&mut self) -> Option<target::ext::host_io::HostIoCloseOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_pread(&mut self) -> Option<target::ext::host_io::HostIoPreadOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_pwrite(&mut self) -> Option<target::ext::host_io::HostIoPwriteOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_fstat(&mut self) -> Option<target::ext::host_io::HostIoFstatOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_unlink(&mut self) -> Option<target::ext::host_io::HostIoUnlinkOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_readlink(&mut self) -> Option<target::ext::host_io::HostIoReadlinkOps<'_, Self>> {
        Some(self)
    }

    #[inline(always)]
    fn support_setfs(&mut self) -> Option<target::ext::host_io::HostIoSetfsOps<'_, Self>> {
        Some(self)
    }
}

impl target::ext::host_io::HostIoOpen for Emu {
    fn open(
        &mut self,
        filename: &[u8],
        flags: HostIoOpenFlags,
        _mode: HostIoOpenMode,
    ) -> HostIoResult<u32, Self> {
        if filename.starts_with(b"/proc") {
            return Err(HostIoError::Errno(HostIoErrno::ENOENT));
        }

        // In this example, the test binary is compiled into the binary itself as the
        // `TEST_PROGRAM_ELF` array using `include_bytes!`. As such, we must "spoof" the
        // existence of a real file, which will actually be backed by the in-binary
        // `TEST_PROGRAM_ELF` array.
        if filename == b"/test.elf" {
            return Ok(0);
        }

        let path =
            std::str::from_utf8(filename).map_err(|_| HostIoError::Errno(HostIoErrno::ENOENT))?;

        let mut read = false;
        let mut write = false;
        if flags.contains(HostIoOpenFlags::O_RDWR) {
            read = true;
            write = true;
        } else if flags.contains(HostIoOpenFlags::O_WRONLY) {
            write = true;
        } else {
            read = true;
        }

        let file = std::fs::OpenOptions::new()
            .read(read)
            .write(write)
            .append(flags.contains(HostIoOpenFlags::O_APPEND))
            .create(flags.contains(HostIoOpenFlags::O_CREAT))
            .truncate(flags.contains(HostIoOpenFlags::O_TRUNC))
            .create_new(flags.contains(HostIoOpenFlags::O_EXCL))
            .open(path)?;

        let n = match self.files.iter_mut().enumerate().find(|(_, f)| f.is_none()) {
            Some((n, free_file)) => {
                *free_file = Some(file);
                n
            }
            None => {
                self.files.push(Some(file));
                self.files.len() - 1
            }
        };

        Ok(n as u32 + FD_RESERVED)
    }
}

impl target::ext::host_io::HostIoClose for Emu {
    fn close(&mut self, fd: u32) -> HostIoResult<(), Self> {
        if fd < FD_RESERVED {
            return Ok(());
        }

        let file = match self.files.get_mut((fd - FD_RESERVED) as usize) {
            Some(file) => file,
            _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
        };

        file.take().ok_or(HostIoError::Errno(HostIoErrno::EBADF))?;
        while let Some(None) = self.files.last() {
            self.files.pop();
        }
        Ok(())
    }
}

impl target::ext::host_io::HostIoPread for Emu {
    fn pread<'a>(
        &mut self,
        fd: u32,
        count: usize,
        offset: u64,
        buf: &mut [u8],
    ) -> HostIoResult<usize, Self> {
        if fd < FD_RESERVED {
            if fd == 0 {
                return Ok(copy_range_to_buf(TEST_PROGRAM_ELF, offset, count, buf));
            } else {
                return Err(HostIoError::Errno(HostIoErrno::EBADF));
            }
        }

        let file = match self.files.get_mut((fd - FD_RESERVED) as usize) {
            Some(Some(file)) => file,
            _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
        };

        file.seek(std::io::SeekFrom::Start(offset))?;
        let n = file.read(buf)?;
        Ok(n)
    }
}

impl target::ext::host_io::HostIoPwrite for Emu {
    fn pwrite(&mut self, fd: u32, offset: u32, data: &[u8]) -> HostIoResult<u32, Self> {
        if fd < FD_RESERVED {
            return Err(HostIoError::Errno(HostIoErrno::EACCES));
        }

        let file = match self.files.get_mut((fd - FD_RESERVED) as usize) {
            Some(Some(file)) => file,
            _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
        };

        file.seek(std::io::SeekFrom::Start(offset as u64))?;
        let n = file.write(data)?;
        Ok(n as u32)
    }
}

impl target::ext::host_io::HostIoFstat for Emu {
    fn fstat(&mut self, fd: u32) -> HostIoResult<HostIoStat, Self> {
        if fd < FD_RESERVED {
            if fd == 0 {
                return Ok(HostIoStat {
                    st_dev: 0,
                    st_ino: 0,
                    st_mode: HostIoOpenMode::empty(),
                    st_nlink: 0,
                    st_uid: 0,
                    st_gid: 0,
                    st_rdev: 0,
                    st_size: TEST_PROGRAM_ELF.len() as u64,
                    st_blksize: 0,
                    st_blocks: 0,
                    st_atime: 0,
                    st_mtime: 0,
                    st_ctime: 0,
                });
            } else {
                return Err(HostIoError::Errno(HostIoErrno::EBADF));
            }
        }
        let metadata = match self.files.get((fd - FD_RESERVED) as usize) {
            Some(Some(file)) => file.metadata()?,
            _ => return Err(HostIoError::Errno(HostIoErrno::EBADF)),
        };

        macro_rules! time_to_secs {
            ($time:expr) => {
                $time
                    .map_err(|_| HostIoError::Errno(HostIoErrno::EACCES))?
                    .duration_since(std::time::SystemTime::UNIX_EPOCH)
                    .map_err(|_| HostIoError::Errno(HostIoErrno::EACCES))?
                    .as_secs() as u32
            };
        }
        let atime = time_to_secs!(metadata.accessed());
        let mtime = time_to_secs!(metadata.modified());
        let ctime = time_to_secs!(metadata.created());

        Ok(HostIoStat {
            st_dev: 0,
            st_ino: 0,
            st_mode: HostIoOpenMode::empty(),
            st_nlink: 0,
            st_uid: 0,
            st_gid: 0,
            st_rdev: 0,
            st_size: metadata.len(),
            st_blksize: 0,
            st_blocks: 0,
            st_atime: atime,
            st_mtime: mtime,
            st_ctime: ctime,
        })
    }
}

impl target::ext::host_io::HostIoUnlink for Emu {
    fn unlink(&mut self, filename: &[u8]) -> HostIoResult<(), Self> {
        let path =
            std::str::from_utf8(filename).map_err(|_| HostIoError::Errno(HostIoErrno::ENOENT))?;
        std::fs::remove_file(path)?;
        Ok(())
    }
}

impl target::ext::host_io::HostIoReadlink for Emu {
    fn readlink<'a>(&mut self, filename: &[u8], buf: &mut [u8]) -> HostIoResult<usize, Self> {
        if filename == b"/proc/1/exe" {
            // Support `info proc exe` command
            let exe = b"/test.elf";
            return Ok(copy_to_buf(exe, buf));
        } else if filename == b"/proc/1/cwd" {
            // Support `info proc cwd` command
            let cwd = b"/";
            return Ok(copy_to_buf(cwd, buf));
        } else if filename.starts_with(b"/proc") {
            return Err(HostIoError::Errno(HostIoErrno::ENOENT));
        }

        let path =
            std::str::from_utf8(filename).map_err(|_| HostIoError::Errno(HostIoErrno::ENOENT))?;
        let link = std::fs::read_link(path)?;
        let data = link
            .to_str()
            .ok_or(HostIoError::Errno(HostIoErrno::ENOENT))?
            .as_bytes();
        if data.len() <= buf.len() {
            Ok(copy_to_buf(data, buf))
        } else {
            Err(HostIoError::Errno(HostIoErrno::ENAMETOOLONG))
        }
    }
}

impl target::ext::host_io::HostIoSetfs for Emu {
    fn setfs(&mut self, _fs: FsKind) -> HostIoResult<(), Self> {
        Ok(())
    }
}