#![crate_name = "uu_seq"]

// TODO: Make -w flag work with decimals
// TODO: Support -f flag

extern crate getopts;

#[macro_use]
extern crate uucore;

use std::cmp;
use std::io::{stdout, Write};

static NAME: &str = "seq";
static VERSION: &str = env!("CARGO_PKG_VERSION");

#[derive(Clone)]
struct SeqOptions {
    separator: String,
    terminator: Option<String>,
    widths: bool,
}

fn parse_float(mut s: &str) -> Result<f64, String> {
    if s.starts_with('+') {
        s = &s[1..];
    }
    match s.parse() {
        Ok(n) => Ok(n),
        Err(e) => Err(format!(
            "seq: invalid floating point argument `{}`: {}",
            s, e
        )),
    }
}

fn escape_sequences(s: &str) -> String {
    s.replace("\\n", "\n").replace("\\t", "\t")
}

fn parse_options(args: Vec<String>, options: &mut SeqOptions) -> Result<Vec<String>, i32> {
    let mut seq_args = vec![];
    let mut iter = args.into_iter().skip(1);
    loop {
        match iter.next() {
            Some(arg) => match &arg[..] {
                "--help" | "-h" => {
                    print_help();
                    return Err(0);
                }
                "--version" | "-V" => {
                    print_version();
                    return Err(0);
                }
                "-s" | "--separator" => match iter.next() {
                    Some(sep) => options.separator = sep,
                    None => {
                        show_error!("expected a separator after {}", arg);
                        return Err(1);
                    }
                },
                "-t" | "--terminator" => match iter.next() {
                    Some(term) => options.terminator = Some(term),
                    None => {
                        show_error!("expected a terminator after '{}'", arg);
                        return Err(1);
                    }
                },
                "-w" | "--widths" => options.widths = true,
                "--" => {
                    seq_args.extend(iter);
                    break;
                }
                _ => {
                    if arg.len() > 1 && arg.starts_with('-') {
                        let argptr: *const String = &arg; // escape from the borrow checker
                        let mut chiter = unsafe { &(*argptr)[..] }.chars().skip(1);
                        let mut ch = ' ';
                        while match chiter.next() {
                            Some(m) => {
                                ch = m;
                                true
                            }
                            None => false,
                        } {
                            match ch {
                                'h' => {
                                    print_help();
                                    return Err(0);
                                }
                                'V' => {
                                    print_version();
                                    return Err(0);
                                }
                                's' => match iter.next() {
                                    Some(sep) => {
                                        options.separator = sep;
                                        let next = chiter.next();
                                        if next.is_some() {
                                            show_error!(
                                                "unexpected character ('{}')",
                                                next.unwrap()
                                            );
                                            return Err(1);
                                        }
                                    }
                                    None => {
                                        show_error!("expected a separator after {}", arg);
                                        return Err(1);
                                    }
                                },
                                't' => match iter.next() {
                                    Some(term) => {
                                        options.terminator = Some(term);
                                        let next = chiter.next();
                                        if next.is_some() {
                                            show_error!(
                                                "unexpected character ('{}')",
                                                next.unwrap()
                                            );
                                            return Err(1);
                                        }
                                    }
                                    None => {
                                        show_error!("expected a terminator after {}", arg);
                                        return Err(1);
                                    }
                                },
                                'w' => options.widths = true,
                                _ => {
                                    seq_args.push(arg);
                                    break;
                                }
                            }
                        }
                    } else {
                        seq_args.push(arg);
                    }
                }
            },
            None => break,
        }
    }
    Ok(seq_args)
}

fn print_help() {
    let mut opts = getopts::Options::new();

    opts.optopt(
        "s",
        "separator",
        "Separator character (defaults to \\n)",
        "",
    );
    opts.optopt(
        "t",
        "terminator",
        "Terminator character (defaults to separator)",
        "",
    );
    opts.optflag(
        "w",
        "widths",
        "Equalize widths of all numbers by padding with zeros",
    );
    opts.optflag("h", "help", "print this help text and exit");
    opts.optflag("V", "version", "print version and exit");

    println!("{} {}\n", NAME, VERSION);
    println!(
        "Usage:\n  {} [-w] [-s string] [-t string] [first [step]] last\n",
        NAME
    );
    println!("{}", opts.usage("Print sequences of numbers"));
}

fn print_version() {
    println!("{} {}", NAME, VERSION);
}

pub fn uumain(args: Vec<String>) -> i32 {
    let mut options = SeqOptions {
        separator: "\n".to_owned(),
        terminator: None,
        widths: false,
    };
    let free = match parse_options(args, &mut options) {
        Ok(m) => m,
        Err(f) => return f,
    };
    if free.len() < 1 || free.len() > 3 {
        crash!(
            1,
            "too {} operands.\nTry '{} --help' for more information.",
            if free.len() < 1 { "few" } else { "many" },
            NAME
        );
    }
    let mut largest_dec = 0;
    let mut padding = 0;
    let first = if free.len() > 1 {
        let slice = &free[0][..];
        let len = slice.len();
        let dec = slice.find('.').unwrap_or(len);
        largest_dec = len - dec;
        padding = dec;
        match parse_float(slice) {
            Ok(n) => n,
            Err(s) => {
                show_error!("{}", s);
                return 1;
            }
        }
    } else {
        1.0
    };
    let step = if free.len() > 2 {
        let slice = &free[1][..];
        let len = slice.len();
        let dec = slice.find('.').unwrap_or(len);
        largest_dec = cmp::max(largest_dec, len - dec);
        padding = cmp::max(padding, dec);
        match parse_float(slice) {
            Ok(n) => n,
            Err(s) => {
                show_error!("{}", s);
                return 1;
            }
        }
    } else {
        1.0
    };
    let last = {
        let slice = &free[free.len() - 1][..];
        padding = cmp::max(padding, slice.find('.').unwrap_or_else(|| slice.len()));
        match parse_float(slice) {
            Ok(n) => n,
            Err(s) => {
                show_error!("{}", s);
                return 1;
            }
        }
    };
    if largest_dec > 0 {
        largest_dec -= 1;
    }
    let separator = escape_sequences(&options.separator[..]);
    let terminator = match options.terminator {
        Some(term) => escape_sequences(&term[..]),
        None => separator.clone(),
    };
    print_seq(
        first,
        step,
        last,
        largest_dec,
        separator,
        terminator,
        options.widths,
        padding,
    );

    0
}

fn done_printing(next: f64, step: f64, last: f64) -> bool {
    if step >= 0f64 {
        next > last
    } else {
        next < last
    }
}

fn print_seq(
    first: f64,
    step: f64,
    last: f64,
    largest_dec: usize,
    separator: String,
    terminator: String,
    pad: bool,
    padding: usize,
) {
    let mut i = 0isize;
    let mut value = first + i as f64 * step;
    while !done_printing(value, step, last) {
        let istr = format!("{:.*}", largest_dec, value);
        let ilen = istr.len();
        let before_dec = istr.find('.').unwrap_or(ilen);
        if pad && before_dec < padding {
            for _ in 0..(padding - before_dec) {
                print!("0");
            }
        }
        print!("{}", istr);
        i += 1;
        value = first + i as f64 * step;
        if !done_printing(value, step, last) {
            print!("{}", separator);
        }
    }
    if (first >= last && step < 0f64) || (first <= last && step > 0f64) {
        print!("{}", terminator);
    }
    crash_if_err!(1, stdout().flush());
}