use std::fs::read_link;

pub(crate) fn get_timezone_inner() -> Result<String, crate::GetTimezoneError> {

    // see https://www.cyberciti.biz/faq/openbsd-time-zone-howto/

    // This is a backport of the Linux implementation.

    // NetBSDs is less than thorough how the softlink should be set up.

    const PREFIXES: &[&str] = &[

        "/usr/share/zoneinfo/",   // absolute path

        "../usr/share/zoneinfo/", // relative path

    ];

    let mut s = read_link("/etc/localtime")?

        .into_os_string()

        .into_string()

        .map_err(|_| crate::GetTimezoneError::FailedParsingString)?;

    for &prefix in PREFIXES {

        if s.starts_with(prefix) {

            // Trim to the correct length without allocating.

            s.replace_range(..prefix.len(), "");

            return Ok(s);

        }

    }

    Err(crate::GetTimezoneError::FailedParsingString)

}