/*
 * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <hello@stalw.art>
 *
 * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
 */

use crate::Principal;
use crate::PrincipalData;
use argon2::Argon2;
use compact_str::ToCompactString;
use mail_builder::encoders::base64::base64_encode;
use mail_parser::decoders::base64::base64_decode;
use password_hash::PasswordHash;
use pbkdf2::Pbkdf2;
use pwhash::{bcrypt, bsdi_crypt, md5_crypt, sha1_crypt, sha256_crypt, sha512_crypt, unix_crypt};
use scrypt::Scrypt;
use sha1::Digest;
use sha1::Sha1;
use sha2::Sha256;
use sha2::Sha512;
use tokio::sync::oneshot;
use totp_rs::TOTP;

impl Principal {
    pub async fn verify_secret(
        &self,
        code: &str,
        only_app_pass: bool,
        is_ordered: bool,
    ) -> trc::Result<bool> {
        let mut seen_password = false;
        let mut password = None;
        let mut otp_auth = None;

        for item in &self.data {
            match item {
                PrincipalData::OtpAuth(secret) => {
                    if !only_app_pass {
                        otp_auth = Some(secret);
                    }
                    seen_password = true;
                }
                PrincipalData::Password(secret) => {
                    if !only_app_pass {
                        password = Some(secret);
                    }
                    seen_password = true;
                }
                PrincipalData::AppPassword(secret) => {
                    // App passwords do not require TOTP
                    if let Some((_, app_secret)) =
                        secret.strip_prefix("$app$").and_then(|s| s.split_once('$'))
                        && verify_secret_hash(app_secret, code).await?
                    {
                        return Ok(true);
                    }

                    seen_password = true;
                }
                _ => {
                    if seen_password && is_ordered {
                        // Password-related secrets are expected to be at the beginning of the list
                        break;
                    }
                }
            }
        }

        // Validate TOTP
        match (otp_auth, password) {
            (Some(otp_auth), Some(password)) => {
                if let Some((code, totp_token)) = code.rsplit_once('$').filter(|(c, t)| {
                    !c.is_empty()
                        && (6..=8).contains(&t.len())
                        && t.as_bytes().iter().all(|b| b.is_ascii_digit())
                }) {
                    let result = verify_secret_hash(password, code).await?
                        && TOTP::from_url(otp_auth)
                            .map_err(|err| {
                                trc::AuthEvent::Error
                                    .reason(err)
                                    .details(otp_auth.to_compact_string())
                            })?
                            .check_current(totp_token)
                            .unwrap_or(false);
                    Ok(result)
                } else if verify_secret_hash(password, code).await? {
                    // Only let the client know if the TOTP code is missing
                    // if the password is correct

                    Err(trc::AuthEvent::MissingTotp.into_err())
                } else {
                    Ok(false)
                }
            }
            (None, Some(password)) => verify_secret_hash(password, code).await,
            _ => Ok(false),
        }
    }
}

async fn verify_hash_prefix(hashed_secret: &str, secret: &str) -> trc::Result<bool> {
    if hashed_secret.starts_with("$argon2")
        || hashed_secret.starts_with("$pbkdf2")
        || hashed_secret.starts_with("$scrypt")
    {
        let (tx, rx) = oneshot::channel();
        let secret = secret.to_string();
        let hashed_secret = hashed_secret.to_string();

        tokio::task::spawn_blocking(move || match PasswordHash::new(&hashed_secret) {
            Ok(hash) => {
                tx.send(Ok(hash
                    .verify_password(&[&Argon2::default(), &Pbkdf2, &Scrypt], &secret)
                    .is_ok()))
                    .ok();
            }
            Err(err) => {
                tx.send(Err(trc::AuthEvent::Error
                    .reason(err)
                    .details(hashed_secret)))
                    .ok();
            }
        });

        match rx.await {
            Ok(result) => result,
            Err(err) => Err(trc::EventType::Server(trc::ServerEvent::ThreadError)
                .caused_by(trc::location!())
                .reason(err)),
        }
    } else if hashed_secret.starts_with("$2") {
        // Blowfish crypt
        Ok(bcrypt::verify(secret, hashed_secret))
    } else if hashed_secret.starts_with("$6$") {
        // SHA-512 crypt
        Ok(sha512_crypt::verify(secret, hashed_secret))
    } else if hashed_secret.starts_with("$5$") {
        // SHA-256 crypt
        Ok(sha256_crypt::verify(secret, hashed_secret))
    } else if hashed_secret.starts_with("$sha1") {
        // SHA-1 crypt
        Ok(sha1_crypt::verify(secret, hashed_secret))
    } else if hashed_secret.starts_with("$1") {
        // MD5 based hash
        Ok(md5_crypt::verify(secret, hashed_secret))
    } else {
        Err(trc::AuthEvent::Error
            .into_err()
            .details(hashed_secret.to_string()))
    }
}

pub async fn verify_secret_hash(hashed_secret: &str, secret: &str) -> trc::Result<bool> {
    if hashed_secret.starts_with('$') {
        verify_hash_prefix(hashed_secret, secret).await
    } else if hashed_secret.starts_with('_') {
        // Enhanced DES-based hash
        Ok(bsdi_crypt::verify(secret, hashed_secret))
    } else if let Some(hashed_secret) = hashed_secret.strip_prefix('{') {
        if let Some((algo, hashed_secret)) = hashed_secret.split_once('}') {
            match algo {
                "ARGON2" | "ARGON2I" | "ARGON2ID" | "PBKDF2" => {
                    verify_hash_prefix(hashed_secret, secret).await
                }
                "SHA" => {
                    // SHA-1
                    let mut hasher = Sha1::new();
                    hasher.update(secret.as_bytes());
                    Ok(
                        String::from_utf8(
                            base64_encode(&hasher.finalize()[..]).unwrap_or_default(),
                        )
                        .unwrap()
                            == hashed_secret,
                    )
                }
                "SSHA" => {
                    // Salted SHA-1
                    let decoded = base64_decode(hashed_secret.as_bytes()).unwrap_or_default();
                    let hash = decoded.get(..20).unwrap_or_default();
                    let salt = decoded.get(20..).unwrap_or_default();
                    let mut hasher = Sha1::new();
                    hasher.update(secret.as_bytes());
                    hasher.update(salt);
                    Ok(&hasher.finalize()[..] == hash)
                }
                "SHA256" => {
                    // Verify hash
                    let mut hasher = Sha256::new();
                    hasher.update(secret.as_bytes());
                    Ok(
                        String::from_utf8(
                            base64_encode(&hasher.finalize()[..]).unwrap_or_default(),
                        )
                        .unwrap()
                            == hashed_secret,
                    )
                }
                "SSHA256" => {
                    // Salted SHA-256
                    let decoded = base64_decode(hashed_secret.as_bytes()).unwrap_or_default();
                    let hash = decoded.get(..32).unwrap_or_default();
                    let salt = decoded.get(32..).unwrap_or_default();
                    let mut hasher = Sha256::new();
                    hasher.update(secret.as_bytes());
                    hasher.update(salt);
                    Ok(&hasher.finalize()[..] == hash)
                }
                "SHA512" => {
                    // SHA-512
                    let mut hasher = Sha512::new();
                    hasher.update(secret.as_bytes());
                    Ok(
                        String::from_utf8(
                            base64_encode(&hasher.finalize()[..]).unwrap_or_default(),
                        )
                        .unwrap()
                            == hashed_secret,
                    )
                }
                "SSHA512" => {
                    // Salted SHA-512
                    let decoded = base64_decode(hashed_secret.as_bytes()).unwrap_or_default();
                    let hash = decoded.get(..64).unwrap_or_default();
                    let salt = decoded.get(64..).unwrap_or_default();
                    let mut hasher = Sha512::new();
                    hasher.update(secret.as_bytes());
                    hasher.update(salt);
                    Ok(&hasher.finalize()[..] == hash)
                }
                "MD5" => {
                    // MD5
                    let digest = md5::compute(secret.as_bytes());
                    Ok(
                        String::from_utf8(base64_encode(&digest[..]).unwrap_or_default()).unwrap()
                            == hashed_secret,
                    )
                }
                "CRYPT" | "crypt" => {
                    if hashed_secret.starts_with('$') {
                        verify_hash_prefix(hashed_secret, secret).await
                    } else {
                        // Unix crypt
                        Ok(unix_crypt::verify(secret, hashed_secret))
                    }
                }
                "PLAIN" | "plain" | "CLEAR" | "clear" => Ok(hashed_secret == secret),
                _ => Err(trc::AuthEvent::Error
                    .ctx(trc::Key::Reason, "Unsupported algorithm")
                    .details(hashed_secret.to_string())),
            }
        } else {
            Err(trc::AuthEvent::Error
                .into_err()
                .details(hashed_secret.to_string()))
        }
    } else if !hashed_secret.is_empty() {
        Ok(hashed_secret == secret)
    } else {
        Ok(false)
    }
}