use anyhow::anyhow;
use base64::Engine;
use rsa::{pkcs8::DecodePublicKey, signature::Verifier};
use sha2::Sha256;

pub async fn validate_license_key(license_key: String) -> anyhow::Result<String> {
    let mut splitted_lk = license_key.split(".");
    if splitted_lk.clone().count() != 3 {
        return Err(anyhow!(
            "license_key can be splitted with 2 . (<client id>.<expiry>.<signature>)"
        ));
    }

    let id = splitted_lk.next().unwrap();
    let expiry = splitted_lk.next().unwrap();
    let signature_b64 = splitted_lk.next().unwrap();

    const PUBLIC_KEY: &str = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDgVShzcLSPiOi+8ET8fggob1kmi47/cE12JaidPkwfGnScZItghkqtiLsct0U4kJhlp5gO89DYTBmIKadvxwY7kMsLlZzmi2emVH7c27cByGASY8QmWDNdG4Ggy/NDflGGBdAtN6gHawZAg4zHv3qpbPQGHH1/6sXIohcXhOnouwIDAQAB";
    let pub_key = rsa::RsaPublicKey::from_public_key_der(
        &base64::engine::general_purpose::STANDARD.decode(PUBLIC_KEY)?,
    )?;
    let signature = base64::engine::general_purpose::STANDARD.decode(signature_b64)?;
    rsa::pss::VerifyingKey::<Sha256>::new(pub_key)
        .verify(
            &format!("{id}{expiry}").as_bytes(),
            &rsa::pss::Signature::from(signature),
        )
        .map_err(|_| anyhow::anyhow!("Invalid license key".to_string()))?;

    let expiry_nb = expiry.parse::<u64>()?;
    if expiry_nb < chrono::Utc::now().timestamp() as u64 {
        tracing::error!(
            "License key expired: {} < {}",
            expiry_nb,
            chrono::Utc::now().timestamp() as u64
        );
        return Err(anyhow!("License key expired".to_string()));
    };

    Ok(id.to_string())
}