//! Tools and utilities
//!
//! This is a collection of small and useful tools.
use failure::*;
use nix::unistd;
use nix::sys::stat;

use lazy_static::lazy_static;

use std::fs::{File, OpenOptions};
use std::io::Write;
use std::path::Path;
use std::io::Read;
use std::io::ErrorKind;
use std::time::Duration;

use std::os::unix::io::RawFd;
use std::os::unix::io::AsRawFd;

use serde_json::Value;

pub mod timer;
pub mod wrapped_reader_stream;
#[macro_use]
pub mod common_regex;
pub mod ticket;
pub mod borrow;
pub mod fs;

/// Macro to write error-handling blocks (like perl eval {})
///
/// #### Example:
/// ```
/// # #[macro_use] extern crate proxmox_backup;
/// # use failure::*;
/// # let some_condition = false;
/// let result = try_block!({
///     if (some_condition) {
///         bail!("some error");
///     }
///     Ok(())
/// })
/// .map_err(|e| format_err!("my try block returned an error - {}", e));
/// ```

#[macro_export]
macro_rules! try_block {
    { $($token:tt)* } => {{ (|| -> Result<_,_> { $($token)* })() }}
}


/// The `BufferedReader` trait provides a single function
/// `buffered_read`. It returns a reference to an internal buffer. The
/// purpose of this traid is to avoid unnecessary data copies.
pub trait BufferedReader {
    /// This functions tries to fill the internal buffers, then
    /// returns a reference to the available data. It returns an empty
    /// buffer if `offset` points to the end of the file.
    fn buffered_read(&mut self, offset: u64) -> Result<&[u8], Error>;
}

/// Directly map a type into a binary buffer. This is mostly useful
/// for reading structured data from a byte stream (file). You need to
/// make sure that the buffer location does not change, so please
/// avoid vec resize while you use such map.
///
/// This function panics if the buffer is not large enough.
pub fn map_struct<T>(buffer: &[u8]) -> Result<&T, Error> {
    if buffer.len() < ::std::mem::size_of::<T>() {
        bail!("unable to map struct - buffer too small");
    }
    Ok(unsafe { & * (buffer.as_ptr() as *const T) })
}

/// Directly map a type into a mutable binary buffer. This is mostly
/// useful for writing structured data into a byte stream (file). You
/// need to make sure that the buffer location does not change, so
/// please avoid vec resize while you use such map.
///
/// This function panics if the buffer is not large enough.
pub fn map_struct_mut<T>(buffer: &mut [u8]) -> Result<&mut T, Error> {
    if buffer.len() < ::std::mem::size_of::<T>() {
        bail!("unable to map struct - buffer too small");
    }
    Ok(unsafe { &mut * (buffer.as_ptr() as *mut T) })
}

pub fn file_read_firstline<P: AsRef<Path>>(path: P) -> Result<String, std::io::Error> {

    let path = path.as_ref();

    let file = std::fs::File::open(path)?;

    use std::io::{BufRead, BufReader};

    let mut reader = BufReader::new(file);

    let mut line = String::new();

    let _ = reader.read_line(&mut line)?;

    Ok(line)
}

pub fn file_get_contents<P: AsRef<Path>>(path: P) -> Result<Vec<u8>, std::io::Error> {
    std::fs::read(path)
}

/// Atomically write a file. We first create a temporary file, which
/// is then renamed.
pub fn file_set_contents<P: AsRef<Path>>(
    path: P,
    data: &[u8],
    perm: Option<stat::Mode>,
) -> Result<(), Error> {

    let path = path.as_ref();

    // Note: we use mkstemp heŕe, because this worka with different
    // processes, threads, and even tokio tasks.
    let mut template = path.to_owned();
    template.set_extension("tmp_XXXXXX");
    let (fd, tmp_path) = match unistd::mkstemp(&template) {
        Ok((fd, path)) => (fd, path),
        Err(err) => bail!("mkstemp {:?} failed: {}", template, err),
    };

    let tmp_path = tmp_path.as_path();

    let mode : stat::Mode = perm.unwrap_or(stat::Mode::from(
        stat::Mode::S_IRUSR | stat::Mode::S_IWUSR |
        stat::Mode::S_IRGRP | stat::Mode::S_IROTH
    ));

    if let Err(err) = stat::fchmod(fd, mode) {
        let _ = unistd::unlink(tmp_path);
        bail!("fchmod {:?} failed: {}", tmp_path, err);
    }

    use std::os::unix::io::FromRawFd;
    let mut file = unsafe { File::from_raw_fd(fd) };

    if let Err(err) = file.write_all(data) {
        let _ = unistd::unlink(tmp_path);
        bail!("write failed: {}", err);
    }

    if let Err(err) = std::fs::rename(tmp_path, path) {
        let _ = unistd::unlink(tmp_path);
        bail!("Atomic rename failed for file {:?} - {}", path, err);
    }

    Ok(())
}

/// Create a file lock using fntl. This function allows you to specify
/// a timeout if you want to avoid infinite blocking.
pub fn lock_file<F: AsRawFd>(
    file: &mut F,
    exclusive: bool,
    timeout: Option<Duration>,
    ) -> Result<(), Error>
{
    let lockarg =
        if exclusive {
            nix::fcntl::FlockArg::LockExclusive
        } else {
            nix::fcntl::FlockArg::LockShared
        };

    let timeout = match timeout {
        None => {
            nix::fcntl::flock(file.as_raw_fd(), lockarg)?;
            return Ok(());
        }
        Some(t) => t,
    };

    // unblock the timeout signal temporarily
    let _sigblock_guard = timer::unblock_timeout_signal();

    // setup a timeout timer
    let mut timer = timer::Timer::create(
        timer::Clock::Realtime,
        timer::TimerEvent::ThisThreadSignal(timer::SIGTIMEOUT))?;

    timer.arm(timer::TimerSpec::new()
        .value(Some(timeout))
        .interval(Some(Duration::from_millis(10))))?;

    nix::fcntl::flock(file.as_raw_fd(), lockarg)?;
    Ok(())
}

/// Open or create a lock file (append mode). Then try to
/// aquire a lock using `lock_file()`.
pub fn open_file_locked<P: AsRef<Path>>(path: P, timeout: Duration)
    -> Result<File, Error>
{
    let path = path.as_ref();
    let mut file =
        match OpenOptions::new()
            .create(true)
            .append(true)
            .open(path)
        {
            Ok(file) => file,
            Err(err) => bail!("Unable to open lock {:?} - {}",
                              path, err),
        };
    match lock_file(&mut file, true, Some(timeout)) {
        Ok(_) => Ok(file),
        Err(err) => bail!("Unable to aquire lock {:?} - {}",
                          path, err),
    }
}

/// Split a file into equal sized chunks. The last chunk may be
/// smaller. Note: We cannot implement an `Iterator`, because iterators
/// cannot return a borrowed buffer ref (we want zero-copy)
pub fn file_chunker<C, R>(
    mut file: R,
    chunk_size: usize,
    mut chunk_cb: C
) -> Result<(), Error>
    where C: FnMut(usize, &[u8]) -> Result<bool, Error>,
          R: Read,
{

    const READ_BUFFER_SIZE: usize = 4*1024*1024; // 4M

    if chunk_size > READ_BUFFER_SIZE { bail!("chunk size too large!"); }

    let mut buf = vec![0u8; READ_BUFFER_SIZE];

    let mut pos = 0;
    let mut file_pos = 0;
    loop {
        let mut eof = false;
        let mut tmp = &mut buf[..];
       // try to read large portions, at least chunk_size
        while pos < chunk_size {
            match file.read(tmp) {
                Ok(0) => { eof = true; break; },
                Ok(n) => {
                    pos += n;
                    if pos > chunk_size { break; }
                    tmp = &mut tmp[n..];
                }
                Err(ref e) if e.kind() == ErrorKind::Interrupted => { /* try again */ }
                Err(e) => bail!("read chunk failed - {}", e.to_string()),
            }
        }
        let mut start = 0;
        while start + chunk_size <= pos {
            if !(chunk_cb)(file_pos, &buf[start..start+chunk_size])? { break; }
            file_pos += chunk_size;
            start += chunk_size;
        }
        if eof {
            if start < pos {
                (chunk_cb)(file_pos, &buf[start..pos])?;
                //file_pos += pos - start;
            }
            break;
        } else {
            let rest = pos - start;
            if rest > 0 {
                let ptr = buf.as_mut_ptr();
                unsafe { std::ptr::copy_nonoverlapping(ptr.add(start), ptr, rest); }
                pos = rest;
            } else {
                pos = 0;
            }
        }
    }

    Ok(())
}

// Returns the Unix uid/gid for the sepcified system user.
pub fn getpwnam_ugid(username: &str) -> Result<(libc::uid_t,libc::gid_t), Error> {
    let info = unsafe { libc::getpwnam(std::ffi::CString::new(username).unwrap().as_ptr()) };
    if info == std::ptr::null_mut() {
        bail!("getwpnam '{}' failed", username);
    }

    let info = unsafe { *info };

    Ok((info.pw_uid, info.pw_gid))
}

// Returns the hosts node name (UTS node name)
pub fn nodename() -> &'static str {

    lazy_static!{
        static ref NODENAME: String = {

            nix::sys::utsname::uname()
                .nodename()
                .split('.')
                .next()
                .unwrap()
                .to_owned()
        };
    }

    &NODENAME
}

pub fn required_string_param<'a>(param: &'a Value, name: &str) -> Result<&'a str, Error> {
    match param[name].as_str()   {
        Some(s) => Ok(s),
        None => bail!("missing parameter '{}'", name),
    }
}

pub fn required_integer_param<'a>(param: &'a Value, name: &str) -> Result<i64, Error> {
    match param[name].as_i64()   {
        Some(s) => Ok(s),
        None => bail!("missing parameter '{}'", name),
    }
}

pub fn complete_file_name(arg: &str) -> Vec<String> {

    let mut result = vec![];

    use nix::fcntl::OFlag;
    use nix::sys::stat::Mode;
    use nix::fcntl::AtFlags;

    let mut dirname = std::path::PathBuf::from(arg);

    let is_dir = match nix::sys::stat::fstatat(libc::AT_FDCWD, &dirname, AtFlags::empty()) {
        Ok(stat) => (stat.st_mode & libc::S_IFMT) == libc::S_IFDIR,
        Err(_) => false,
    };

    if !is_dir {
        if let Some(parent) = dirname.parent() {
            dirname = parent.to_owned();
        }
    }

    let mut dir = match nix::dir::Dir::openat(libc::AT_FDCWD, &dirname, OFlag::O_DIRECTORY, Mode::empty()) {
        Ok(d) => d,
        Err(_) => return result,
    };

    for item in dir.iter() {
        if let Ok(entry) = item {
            if let Ok(name) = entry.file_name().to_str() {
                if name == "." || name == ".." { continue; }
                let mut newpath = dirname.clone();
                newpath.push(name);

                if let Ok(stat) = nix::sys::stat::fstatat(libc::AT_FDCWD, &newpath, AtFlags::empty()) {
                    if (stat.st_mode & libc::S_IFMT) == libc::S_IFDIR {
                        newpath.push("");
                        if let Some(newpath) = newpath.to_str() {
                            result.push(newpath.to_owned());
                        }
                        continue;
                     }
                }
                if let Some(newpath) = newpath.to_str() {
                    result.push(newpath.to_owned());
                }

             }
        }
    }

    result
}

/// Scan directory for matching file names.
///
/// Scan through all directory entries and call `callback()` function
/// if the entry name matches the regular expression. This function
/// used unix `openat()`, so you can pass absolute or relative file
/// names. This function simply skips non-UTF8 encoded names.
pub fn scandir<P, F>(
    dirfd: RawFd,
    path: &P,
    regex: &regex::Regex,
    mut callback: F
) -> Result<(), Error>
    where F: FnMut(RawFd, &str, nix::dir::Type) -> Result<(), Error>,
          P: ?Sized + nix::NixPath,
{
    for entry in self::fs::scan_subdir(dirfd, path, regex)? {
        let entry = entry?;
        let file_type = match entry.file_type() {
            Some(file_type) => file_type,
            None => bail!("unable to detect file type"),
        };

        callback(entry.parent_fd(), unsafe { entry.file_name_utf8_unchecked() }, file_type)?;
    }
    Ok(())
}

pub fn get_hardware_address() -> Result<String, Error> {

    static FILENAME: &str = "/etc/ssh/ssh_host_rsa_key.pub";

    let contents = file_get_contents(FILENAME)?;
    let digest = md5::compute(contents);

    Ok(format!("{:0x}", digest))
}

pub fn digest_to_hex(digest: &[u8]) -> String {

    const HEX_CHARS: &'static [u8; 16] = b"0123456789abcdef";

    let mut buf = Vec::<u8>::with_capacity(digest.len()*2);

    for i in 0..digest.len() {
        buf.push(HEX_CHARS[(digest[i] >> 4) as usize]);
        buf.push(HEX_CHARS[(digest[i] & 0xf) as usize]);
    }

    unsafe { String::from_utf8_unchecked(buf) }
}

pub fn assert_if_modified(digest1: &str, digest2: &str) -> Result<(), Error> {
    if digest1 != digest2 {
	bail!("detected modified configuration - file changed by other user? Try again.");
    }
    Ok(())
}

/// Extract authentication cookie from cookie header.
/// We assume cookie_name is already url encoded.
pub fn extract_auth_cookie(cookie: &str, cookie_name: &str) -> Option<String> {

    for pair in cookie.split(';') {

        let (name, value) = match pair.find('=') {
            Some(i) => (pair[..i].trim(), pair[(i + 1)..].trim()),
            None => return None, // Cookie format error
        };

        if name == cookie_name {
            use url::percent_encoding::percent_decode;
            if let Ok(value) = percent_decode(value.as_bytes()).decode_utf8() {
                return Some(value.into());
            } else {
                return None; // Cookie format error
            }
        }
    }

    None
}