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//! Experimental Compute@Edge features.
use crate::{abi, Error};

/// Parse a user agent string.
pub fn uap_parse(
    user_agent: &str,
) -> Result<(String, Option<String>, Option<String>, Option<String>), Error> {
    let user_agent: &[u8] = user_agent.as_ref();
    let max_length = 255;
    let mut family = Vec::with_capacity(max_length);
    let mut major = Vec::with_capacity(max_length);
    let mut minor = Vec::with_capacity(max_length);
    let mut patch = Vec::with_capacity(max_length);
    let mut family_nwritten = 0;
    let mut major_nwritten = 0;
    let mut minor_nwritten = 0;
    let mut patch_nwritten = 0;

    let status = unsafe {
        abi::fastly_uap::parse(
            user_agent.as_ptr(),
            user_agent.len(),
            family.as_mut_ptr(),
            family.capacity(),
            &mut family_nwritten,
            major.as_mut_ptr(),
            major.capacity(),
            &mut major_nwritten,
            minor.as_mut_ptr(),
            minor.capacity(),
            &mut minor_nwritten,
            patch.as_mut_ptr(),
            patch.capacity(),
            &mut patch_nwritten,
        )
    };
    if status.is_err() {
        return Err(Error::msg("fastly_uap::parse failed"));
    }
    assert!(
        family_nwritten <= family.capacity(),
        "fastly_uap::parse wrote too many bytes for family"
    );
    unsafe {
        family.set_len(family_nwritten);
    }
    assert!(
        major_nwritten <= major.capacity(),
        "fastly_uap::parse wrote too many bytes for major"
    );
    unsafe {
        major.set_len(major_nwritten);
    }
    assert!(
        minor_nwritten <= minor.capacity(),
        "fastly_uap::parse wrote too many bytes for minor"
    );
    unsafe {
        minor.set_len(minor_nwritten);
    }
    assert!(
        patch_nwritten <= patch.capacity(),
        "fastly_uap::parse wrote too many bytes for patch"
    );
    unsafe {
        patch.set_len(patch_nwritten);
    }
    Ok((
        String::from_utf8_lossy(&family).to_string(),
        Some(String::from_utf8_lossy(&major).to_string()),
        Some(String::from_utf8_lossy(&minor).to_string()),
        Some(String::from_utf8_lossy(&patch).to_string()),
    ))
}