#![feature(libc)]
extern crate libc;

use std::any::Any;
use std::fs;
use std::io;
use std::io::Read;
use std::path::Path;
use std::process::{Command, Stdio};
use std::str::from_utf8_unchecked;

/// Shortcut to path->filename conversion.
///
/// Returns the unchanged `path` if there is a character encoding error or something.
pub fn filename<'a> (path: &'a str) -> &'a str {
  match Path::new (path) .file_name() {
    Some (filename) => match filename.to_str() {
      Some (fstr) => if fstr.ends_with (".rs") {&fstr[0 .. fstr.len() - 3]} else {fstr},
      None => path},
    None => path}}

mod gstuff {pub fn filename<'a> (path: &'a str) -> &'a str {super::filename (path)}}

// A trick to use the `try_s` macro from both the outside and inside of the crate.
//mod gstuff {pub fn filename<'a> (path: &'a str) -> &'a str {::filename (path)}}

/// Returns on error, converting the `Err` value to `String` and prepending the current location.
///
/// cf. http://www.reddit.com/r/rust/comments/29wwzw/error_handling_and_result_types/cipcm9a
#[macro_export] macro_rules! try_s {
  ($e: expr) => {match $e {Ok (ok) => ok, Err (err) => {return Err (format! ("{}:{}] {}", ::gstuff::filename (file!()), line!(), err));}}}}

// Like `try_s`, but takes a reference.
#[macro_export] macro_rules! try_sp {
  ($e: expr) => {match $e {&Ok (ref ok) => ok,
    &Err (ref err) => {return Err (format! ("{}:{}] {:?}", ::gstuff::filename (file!()), line!(), err));}}}}

/// Returns a `Err(String)`, prepending the current location (file name and line number) to the string.
///
/// Examples: `ERR! ("too bad")`; `ERR! ("{}", foo)`;
#[macro_export] macro_rules! ERR {
  ($format: expr, $($args: tt)+) => {Err (format! (concat! ("{}:{}] ", $format), ::gstuff::filename (file!()), line!(), $($args)+))};
  ($format: expr) => {Err (format! (concat! ("{}:{}] ", $format), ::gstuff::filename (file!()), line!()))}}

/// A helper to build a string on the stack.
///
/// Given an array it makes a writeable cursor available to the passed code block.
///
/// Returns a &str slice pointing at memory between the array start and the cursor.
///
/// Example:
///
///     use std::io::Write;
///     let mut foobar: [u8; 128] = unsafe {std::mem::uninitialized()};
///     let foobar = gstring! (foobar, {
///         write! (foobar, "foo") .expect ("!write");
///         write! (foobar, "bar") .expect ("!write");
///     });
///
/// Alternatives: https://crates.io/crates/stack.
#[macro_export] macro_rules! gstring {($array: ident, $code: block) => {{
  let end = {
    let mut $array = ::std::io::Cursor::new (&mut $array[..]);
    let $array = &mut $array;
    $code;
    $array.position() as usize};
  unsafe {::std::str::from_utf8_unchecked (&$array[0..end])}}}}

/// Takes a netstring from the front of the slice.
///
/// Returns the unpacked netstring and the remainder of the slice.
pub fn netstring (at: &[u8]) -> Result<(&[u8], &[u8]), String> {
  let length_end = match at.iter().position (|&ch| ch < b'0' || ch > b'9') {Some (l) if l > 0 => l, _ => return ERR! ("No len.")};
  match at.get (length_end) {Some (&ch) if ch == b':' => (), _ => return ERR! ("No colon.")};
  let length = unsafe {from_utf8_unchecked (&at[0 .. length_end])};
  let length: usize = try_s! (length.parse());
  let bulk_pos = 0 + length_end + 1;
  let bulk_end = bulk_pos + length;
  match at.get (bulk_end) {Some (&ch) if ch == b',' => (), _ => return ERR! ("No comma.")}
  Ok ((&at[bulk_pos .. bulk_end], &at[bulk_end + 1 ..]))}

/// Wraps `gethostname` to fetch the current hostname into a temporary buffer.
#[cfg(unix)]
pub fn with_hostname (visitor: &mut FnMut (&[u8])) -> Result<(), std::io::Error> {
  use libc::{size_t, gethostname};  // http://man7.org/linux/man-pages/man2/gethostname.2.html
  use std::ffi::CStr;
  use std::io;

  let mut buf = [0; 128];
  let rc = unsafe {gethostname (buf.as_mut_ptr(), (buf.len() - 1) as size_t)};
  if rc == 0 {
    let cs = unsafe {CStr::from_ptr (buf.as_ptr())};
    Ok (visitor (cs.to_bytes()))
  } else {
    Err (io::Error::last_os_error())}}

#[cfg(unix)] #[test] fn test_hostname() {
  let mut hostname = String::new();
  with_hostname (&mut |bytes| hostname = String::from_utf8_lossy (bytes) .into_owned()) .unwrap();}

/// Read contents of the file into a String.
///
/// Returns an empty string if the file is not present under the given path.
pub fn slurp (path: &AsRef<Path>) -> String {
  let mut file = match fs::File::open (path) {
    Ok (f) => f,
    Err (ref err) if err.kind() == io::ErrorKind::NotFound => return String::new(),
    Err (err) => panic! ("Can't open {:?}: {}", path.as_ref(), err)};
  let mut buf = String::new();
  file.read_to_string (&mut buf) .expect ("!read");
  buf}

/// Runs a command in a shell, returning stderr+stdout on success.
///
/// Sometimes we need something simpler than constructing a Command.
///
/// If the command failed then returns it's stderr
pub fn slurp_prog (command: &str) -> Result<String, String> {
  let output = match Command::new ("bash") .arg ("-c") .arg (command) .output() {
    Ok (output) => output,
    Err (ref err) if err.kind() == io::ErrorKind::NotFound => {  // "sh" was not found, try a different name.
      try_s! (Command::new ("sh") .arg ("-c") .arg (command) .output())},
    Err (err) => return ERR! ("{}", err)};

  let combined_output: String = if output.stderr.is_empty() {
    try_s! (String::from_utf8 (output.stdout))
  } else if output.stdout.is_empty() {
    try_s! (String::from_utf8 (output.stderr))
  } else {
    let mut buf = String::with_capacity (output.stderr.len() + output.stdout.len());
    buf.push_str (try_s! (std::str::from_utf8 (&output.stderr[..])));
    buf.push_str (try_s! (std::str::from_utf8 (&output.stdout[..])));
    buf};

  if output.status.success() {Ok (combined_output)} else {Err (combined_output)}}

#[test] fn test_slurp_prog() {
  let foo = match slurp_prog ("echo foo") {Ok (foo) => foo, Err (err) => panic! ("{}", err)};
  assert_eq! (foo.trim(), "foo");}

/// Run a command, printing it first. Stdout and stderr are forwarded through (`inherit`).
pub fn cmd (cmd: &str) -> Result<(), String> {
  println! ("$ {}", cmd);
  let status = try_s! (Command::new ("bash") .arg ("-c") .arg (cmd) .stdout (Stdio::inherit()) .stderr (Stdio::inherit()) .status());
  if !status.success() {Err (format! ("Command returned an error status: {}", status))} else {Ok(())}}

/// Useful with panic handlers.
pub fn any_to_str<'a> (message: &'a Box<Any + Send + 'static>) -> Option<&'a str> {
  if let Some (message) = message.downcast_ref::<&str>() {return Some (message)}
  if let Some (message) = message.downcast_ref::<String>() {return Some (&message[..])}
  return None}

// --- nom extensions ---

/// Implements the `/(?x) (.*?) (remainder)/` pattern:
/// looks for remainder first, then returns a tuple with the prefix and the remainder.
///
/// Discussion: https://www.reddit.com/r/rust/comments/4yokxd/crash_course_into_nom_kind_of_question/
#[macro_export]
macro_rules! take_until_parse_s (
  ($i: expr, $remainder: ident! ($($args:tt)*)) => ({
    let input = $i as &str;
    let mut ret = IResult::Error (nom::Err::Position (nom::ErrorKind::Custom (0), input));
    for (pos, _) in $i.char_indices() {
      match $remainder! (&input[pos..], $($args)*) {
        IResult::Done (i,o)    => {ret = IResult::Done (i, (&input[0..pos], o)); break},  // Found the remainder!
        IResult::Error(_)      => continue,  // Keep looking.
        IResult::Incomplete(_) => continue}}  // Keep looking.

    if !ret.is_done() {
      // Last chance. See if subparser accepts an empty string.
      if let IResult::Done (i,o) = $remainder! ("", $($args)*) {
        ret = IResult::Done (i, (input, o))}}  // Empty remainder was accepted.

    ret});

  ($i: expr, $f: expr) => (take_until_parse_s! ($i, call! ($f));););

/// Uses nom to find all matches of the given `$submac` parser and replace them with the `$submac` results.
///
/// For exaple, replacing "foo" with "bar" might look like this:
///
///     let bar_bar = parse_replace_s! ("foo bar", map! (tag_s! ("foo"), |_| "bar"));
#[macro_export]
macro_rules! parse_replace_s {
  ($i: expr, $submac: ident! ($($args:tt)*)) => ({
    let input = $i as &str;
    let mut output = String::with_capacity (input.len() * 2 + 32);
    let mut pos = input;
    while let IResult::Done (tail, (head, evaluation)) = take_until_parse_s! (pos, $submac! ($($args)*)) {
      output.push_str (head);
      output.push_str (&evaluation);
      pos = tail;}
    output.push_str (pos);
    output});

  ($i: expr, $f: expr) => (parse_replace! ($i, call! ($f)););}

/// `$starts` is an optional `Pattern` used to optimize the `$remainder` search.
///
/// For example, with jetscii: `take_until_find_parse_s! ("foo bar", ascii_chars! ('b'), tag_s! ("bar"))`.
#[macro_export]
macro_rules! take_until_find_parse_s (
  ($i: expr, $starts: expr, $remainder: ident! ($($args:tt)*)) => ({
    let input = $i as &str;
    let mut ret = IResult::Error (nom::Err::Position (nom::ErrorKind::Custom (0), input));
    for (pos, _) in $i.match_indices ($starts) {
      match $remainder! (&input[pos..], $($args)*) {
        IResult::Done (i,o)    => {ret = IResult::Done (i, (&input[0..pos], o)); break},  // Found the remainder!
        IResult::Error(_)      => continue,  // Keep looking.
        IResult::Incomplete(_) => continue}}  // Keep looking.
    ret});

  ($i: expr, $starts: expr, $f: expr) => (take_until_find_parse_s! ($i, $starts, call! ($f));););

/// Uses nom to find all matches of the given `$submac` parser and replace them with the parser's evaluations.
///
/// `$starts` is a `Pattern` that is used to speed up the search. It must match the beginning of any `$submac`-compatible substrings.
///
/// For exaple, replacing "foo" with "bar" might look like this:
///
///     let bar_bar = find_parse_replace_s! ("foo bar", ascii_chars! ('f'), map! (tag_s! ("foo"), |_| "bar"));
#[macro_export]
macro_rules! find_parse_replace_s {
  ($i: expr, $starts: expr, $submac: ident! ($($args:tt)*)) => ({
    let input = $i as &str;
    let mut output = String::with_capacity (input.len() * 2 + 32);
    let mut pos = input;
    while let IResult::Done (tail, (head, evaluation)) =
      take_until_find_parse_s! (pos, $starts, $submac! ($($args)*)) {
        output.push_str (head);
        output.push_str (&evaluation);
        pos = tail;}
    output.push_str (pos);
    output});

  ($i: expr, $starts: expr, $f: expr) => (find_parse_replace! ($i, $starts, call! ($f)););}