//! Password hashing with argon2id.

use argon2::Argon2;
use argon2::password_hash::phc::PasswordHash;
use argon2::password_hash::{PasswordHasher, PasswordVerifier};

use crate::error::{Error, Result};

/// Hashes `pw` with argon2id (default parameters) and a random salt. Returns a PHC string.
pub fn hash_password(pw: &str) -> Result<String> {
    // The trait method draws a fresh salt from the OS RNG.
    Argon2::default()
        .hash_password(pw.as_bytes())
        .map(|h| h.to_string())
        .map_err(|e| Error::Crypto(format!("argon2: {e}")))
}

/// Returns true only if `pw` matches the PHC string `hash`. Any error yields false.
pub fn verify_password(pw: &str, hash: &str) -> bool {
    let Ok(parsed) = PasswordHash::new(hash) else {
        return false;
    };
    Argon2::default()
        .verify_password(pw.as_bytes(), &parsed)
        .is_ok()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn hash_then_verify() {
        let hash = hash_password("correct horse").unwrap();
        assert!(hash.starts_with("$argon2id$"));
        assert!(verify_password("correct horse", &hash));
        assert!(!verify_password("wrong", &hash));
    }

    #[test]
    fn salts_differ_between_hashes() {
        let a = hash_password("pw").unwrap();
        let b = hash_password("pw").unwrap();
        assert_ne!(a, b);
    }

    #[test]
    fn verify_is_false_on_malformed_hash() {
        assert!(!verify_password("pw", "not a phc string"));
        assert!(!verify_password("pw", ""));
    }
}