extern crate rand;
extern crate regex;

use self::rand::{thread_rng, Rng};
use self::regex::Regex;
use crate::common::util::*;
use rand::SeedableRng;
#[cfg(not(windows))]
use std::env;
use std::io::Write;
use std::path::Path;
use std::{
    fs::{read_dir, File},
    io::BufWriter,
};

fn random_chars(n: usize) -> String {
    thread_rng()
        .sample_iter(&rand::distributions::Alphanumeric)
        .take(n)
        .collect::<String>()
}

struct Glob {
    directory: AtPath,
    regex: Regex,
}

impl Glob {
    fn new(at: &AtPath, directory: &str, regex: &str) -> Glob {
        Glob {
            directory: AtPath::new(Path::new(&at.plus_as_string(directory))),
            regex: Regex::new(regex).unwrap(),
        }
    }

    fn count(&self) -> usize {
        self.collect().len()
    }

    /// Get all files in `self.directory` that match `self.regex`
    fn collect(&self) -> Vec<String> {
        read_dir(Path::new(&self.directory.subdir))
            .unwrap()
            .filter_map(|entry| {
                let path = entry.unwrap().path();
                let name = self
                    .directory
                    .minus_as_string(path.as_path().to_str().unwrap_or(""));
                if self.regex.is_match(&name) {
                    Some(name)
                } else {
                    None
                }
            })
            .collect()
    }

    /// Accumulate bytes of all files in `self.collect()`
    fn collate(&self) -> Vec<u8> {
        let mut files = self.collect();
        files.sort();
        let mut data: Vec<u8> = vec![];
        for name in &files {
            data.extend(self.directory.read_bytes(name));
        }
        data
    }
}

/// File handle that user can add random bytes (line-formatted or not) to
struct RandomFile {
    inner: File,
}

impl RandomFile {
    /// Size of each line that's being generated
    const LINESIZE: usize = 32;

    /// `create()` file handle located at `at` / `name`
    fn new(at: &AtPath, name: &str) -> RandomFile {
        RandomFile {
            inner: File::create(&at.plus(name)).unwrap(),
        }
    }

    fn add_bytes(&mut self, bytes: usize) {
        // Note that just writing random characters isn't enough to cover all
        // cases. We need truly random bytes.
        let mut writer = BufWriter::new(&self.inner);

        // Seed the rng so as to avoid spurious test failures.
        let mut rng = rand::rngs::StdRng::seed_from_u64(123);
        let mut buffer = [0; 1024];
        let mut remaining_size = bytes;

        while remaining_size > 0 {
            let to_write = std::cmp::min(remaining_size, buffer.len());
            let buf = &mut buffer[..to_write];
            rng.fill(buf);
            writer.write_all(buf).unwrap();

            remaining_size -= to_write;
        }
    }

    /// Add n lines each of size `RandomFile::LINESIZE`
    fn add_lines(&mut self, lines: usize) {
        let mut n = lines;
        while n > 0 {
            writeln!(self.inner, "{}", random_chars(RandomFile::LINESIZE)).unwrap();
            n -= 1;
        }
    }
}

#[test]
fn test_split_default() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "split_default";
    RandomFile::new(&at, name).add_lines(2000);
    ucmd.args(&[name]).succeeds();

    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
    assert_eq!(glob.count(), 2);
    assert_eq!(glob.collate(), at.read_bytes(name));
}

#[test]
fn test_split_numeric_prefixed_chunks_by_bytes() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "split_num_prefixed_chunks_by_bytes";
    RandomFile::new(&at, name).add_bytes(10000);
    ucmd.args(&[
        "-d", // --numeric-suffixes
        "-b", // --bytes
        "1000", name, "a",
    ])
    .succeeds();

    let glob = Glob::new(&at, ".", r"a\d\d$");
    assert_eq!(glob.count(), 10);
    for filename in glob.collect() {
        assert_eq!(glob.directory.metadata(&filename).len(), 1000);
    }
    assert_eq!(glob.collate(), at.read_bytes(name));
}

#[test]
fn test_split_str_prefixed_chunks_by_bytes() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "split_str_prefixed_chunks_by_bytes";
    RandomFile::new(&at, name).add_bytes(10000);
    // Important that this is less than 1024 since that's our internal buffer
    // size. Good to test that we don't overshoot.
    ucmd.args(&["-b", "1000", name, "b"]).succeeds();

    let glob = Glob::new(&at, ".", r"b[[:alpha:]][[:alpha:]]$");
    assert_eq!(glob.count(), 10);
    for filename in glob.collect() {
        assert_eq!(glob.directory.metadata(&filename).len(), 1000);
    }
    assert_eq!(glob.collate(), at.read_bytes(name));
}

// This is designed to test what happens when the desired part size is not a
// multiple of the buffer size and we hopefully don't overshoot the desired part
// size.
#[test]
fn test_split_bytes_prime_part_size() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "test_split_bytes_prime_part_size";
    RandomFile::new(&at, name).add_bytes(10000);
    // 1753 is prime and greater than the buffer size, 1024.
    ucmd.args(&["-b", "1753", name, "b"]).succeeds();

    let glob = Glob::new(&at, ".", r"b[[:alpha:]][[:alpha:]]$");
    assert_eq!(glob.count(), 6);
    let mut fns = glob.collect();
    // glob.collect() is not guaranteed to return in sorted order, so we sort.
    fns.sort();
    #[allow(clippy::needless_range_loop)]
    for i in 0..5 {
        assert_eq!(glob.directory.metadata(&fns[i]).len(), 1753);
    }
    assert_eq!(glob.directory.metadata(&fns[5]).len(), 1235);
    assert_eq!(glob.collate(), at.read_bytes(name));
}

#[test]
fn test_split_num_prefixed_chunks_by_lines() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "split_num_prefixed_chunks_by_lines";
    RandomFile::new(&at, name).add_lines(10000);
    ucmd.args(&["-d", "-l", "1000", name, "c"]).succeeds();

    let glob = Glob::new(&at, ".", r"c\d\d$");
    assert_eq!(glob.count(), 10);
    assert_eq!(glob.collate(), at.read_bytes(name));
}

#[test]
fn test_split_str_prefixed_chunks_by_lines() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "split_str_prefixed_chunks_by_lines";
    RandomFile::new(&at, name).add_lines(10000);
    ucmd.args(&["-l", "1000", name, "d"]).succeeds();

    let glob = Glob::new(&at, ".", r"d[[:alpha:]][[:alpha:]]$");
    assert_eq!(glob.count(), 10);
    assert_eq!(glob.collate(), at.read_bytes(name));
}

#[test]
fn test_split_additional_suffix() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "split_additional_suffix";
    RandomFile::new(&at, name).add_lines(2000);
    ucmd.args(&["--additional-suffix", ".txt", name]).succeeds();

    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]].txt$");
    assert_eq!(glob.count(), 2);
    assert_eq!(glob.collate(), at.read_bytes(name));
}

// note: the test_filter* tests below are unix-only
// windows support has been waived for now because of the difficulty of getting
// the `cmd` call right
// see https://github.com/rust-lang/rust/issues/29494

#[test]
#[cfg(unix)]
fn test_filter() {
    // like `test_split_default()` but run a command before writing
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "filtered";
    let n_lines = 3;
    RandomFile::new(&at, name).add_lines(n_lines);

    // change all characters to 'i'
    ucmd.args(&["--filter=sed s/./i/g > $FILE", name])
        .succeeds();

    // assert all characters are 'i' / no character is not 'i'
    // (assert that command succeeded)
    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
    assert!(
        glob.collate().iter().find(|&&c| {
            // is not i
            c != (b'i')
            // is not newline
            && c != (b'\n')
        }) == None
    );
}

#[test]
#[cfg(unix)]
fn test_filter_with_env_var_set() {
    // This test will ensure that if $FILE env var was set before running --filter, it'll stay that
    // way
    // implemented like `test_split_default()` but run a command before writing
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "filtered";
    let n_lines = 3;
    RandomFile::new(&at, name).add_lines(n_lines);

    let env_var_value = "some-value";
    env::set_var("FILE", &env_var_value);
    ucmd.args(&[format!("--filter={}", "cat > $FILE").as_str(), name])
        .succeeds();

    let glob = Glob::new(&at, ".", r"x[[:alpha:]][[:alpha:]]$");
    assert_eq!(glob.collate(), at.read_bytes(name));
    assert!(env::var("FILE").unwrap_or_else(|_| "var was unset".to_owned()) == env_var_value);
}

#[test]
#[cfg(unix)]
fn test_filter_command_fails() {
    let (at, mut ucmd) = at_and_ucmd!();
    let name = "filter-will-fail";
    RandomFile::new(&at, name).add_lines(4);

    ucmd.args(&["--filter=/a/path/that/totally/does/not/exist", name])
        .fails();
}