use nom8::branch::alt;
use nom8::character::digit1 as digit;
use nom8::combinator::opt;
use nom8::prelude::*;
use nom8::sequence::delimited;
use nom8::IResult;

use std::str;
use std::str::FromStr;

fn unsigned_float(i: &[u8]) -> IResult<&[u8], f32> {
  let float_bytes = alt((
    delimited(digit, ".", opt(digit)),
    delimited(opt(digit), ".", digit),
  ))
  .recognize();
  let float_str = float_bytes.map_res(str::from_utf8);
  float_str.map_res(FromStr::from_str).parse(i)
}

fn float(i: &[u8]) -> IResult<&[u8], f32> {
  (opt(alt(("+", "-"))), unsigned_float)
    .map(|(sign, value)| {
      sign
        .and_then(|s| if s[0] == b'-' { Some(-1f32) } else { None })
        .unwrap_or(1f32)
        * value
    })
    .parse(i)
}

#[test]
fn unsigned_float_test() {
  assert_eq!(unsigned_float(&b"123.456;"[..]), Ok((&b";"[..], 123.456)));
  assert_eq!(unsigned_float(&b"0.123;"[..]), Ok((&b";"[..], 0.123)));
  assert_eq!(unsigned_float(&b"123.0;"[..]), Ok((&b";"[..], 123.0)));
  assert_eq!(unsigned_float(&b"123.;"[..]), Ok((&b";"[..], 123.0)));
  assert_eq!(unsigned_float(&b".123;"[..]), Ok((&b";"[..], 0.123)));
}

#[test]
fn float_test() {
  assert_eq!(float(&b"123.456;"[..]), Ok((&b";"[..], 123.456)));
  assert_eq!(float(&b"+123.456;"[..]), Ok((&b";"[..], 123.456)));
  assert_eq!(float(&b"-123.456;"[..]), Ok((&b";"[..], -123.456)));
}