use std::str;
use crate::crypto_utils;

/// Possible errors during a hash creation.
#[derive(PartialEq, Debug)]
pub enum HasherError {
    /// Algorithm not recognizable.
    UnknownAlgorithm,
    /// Hash string is corrupted.
    BadHash,
    /// Hash string is empty.
    EmptyHash,
    /// Number of iterations is not a positive integer.
    InvalidIterations,
    /// Argon2 salt should be Base64 encoded.
    InvalidArgon2Salt,
}

/// Hasher abstraction, providing methods to encode and verify hashes.
pub trait Hasher {
    /// Verifies a password against an encoded hash.
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError>;
    /// Generates an encoded hash for a given password and salt.
    fn encode(&self, password: &str, salt: &str, iterations: u32) -> String;
}

// List of Hashers:

/// Hasher that uses the PBKDF2 key-derivation function with the SHA256 hashing algorithm.
#[cfg(feature="with_pbkdf2")]
pub struct PBKDF2Hasher;

#[cfg(feature="with_pbkdf2")]
impl Hasher for PBKDF2Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let mut encoded_part = encoded.split('$').skip(1);
        let iterations = encoded_part.next().ok_or(HasherError::BadHash)?
            .parse::<u32>().map_err(|_| HasherError::InvalidIterations)?;
        let salt = encoded_part.next().ok_or(HasherError::BadHash)?;
        let hash = encoded_part.next().ok_or(HasherError::BadHash)?;
        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_pbkdf2_sha256(password, salt, iterations)))
    }

    fn encode(&self, password: &str, salt: &str, iterations: u32) -> String {
        let hash = crypto_utils::hash_pbkdf2_sha256(password, salt, iterations);
        format!("{}${}${}${}", "pbkdf2_sha256", iterations, salt, hash)
    }
}

/// Hasher that uses the PBKDF2 key-derivation function with the SHA1 hashing algorithm.
#[cfg(feature="with_pbkdf2")]
pub struct PBKDF2SHA1Hasher;

#[cfg(feature="with_pbkdf2")]
impl Hasher for PBKDF2SHA1Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let mut encoded_part = encoded.split('$').skip(1);
        let iterations = encoded_part.next().ok_or(HasherError::BadHash)?
            .parse::<u32>().map_err(|_| HasherError::InvalidIterations)?;
        let salt = encoded_part.next().ok_or(HasherError::BadHash)?;
        let hash = encoded_part.next().ok_or(HasherError::BadHash)?;
        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_pbkdf2_sha1(password, salt, iterations)))
    }

    fn encode(&self, password: &str, salt: &str, iterations: u32) -> String {
        let hash = crypto_utils::hash_pbkdf2_sha1(password, salt, iterations);
        format!("{}${}${}${}", "pbkdf2_sha1", iterations, salt, hash)
    }
}

/// Hasher that uses the Argon2 function (new in Django 1.10).
#[cfg(feature="with_argon2")]
pub struct Argon2Hasher;

#[cfg(feature="with_argon2")]
const OLD_ARGON2_VERSION: u32 = 0x10;
#[cfg(feature="with_argon2")]
const NEW_ARGON2_VERSION: u32 = 0x13;

#[cfg(feature="with_argon2")]
impl Hasher for Argon2Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let encoded_part: Vec<&str> = encoded.split('$').collect();
        let version = match encoded_part.len() {
            6 => NEW_ARGON2_VERSION,
            5 => OLD_ARGON2_VERSION,
            _ => return Err(HasherError::BadHash),
        };
        let segment_shift = 6 - encoded_part.len();
        let settings = encoded_part[3 - segment_shift];
        let salt = encoded_part[4 - segment_shift];
        let string_hash = encoded_part[5 - segment_shift].replace('+', "-");
        let hash = string_hash.as_str();
        let settings_part: Vec<&str> = settings.split(',').collect();
        let memory_cost: u32 = settings_part[0].split('=').collect::<Vec<&str>>()[1].parse::<u32>().unwrap();
        let time_cost: u32 = settings_part[1].split('=').collect::<Vec<&str>>()[1].parse::<u32>().unwrap();
        let parallelism: u32 = settings_part[2].split('=').collect::<Vec<&str>>()[1].parse::<u32>().unwrap();

        // Django's implementation expects a Base64-encoded salt, if it is not, return an error:
        match base64::decode_config(salt, base64::URL_SAFE_NO_PAD) {
            Ok(_) => {},
            Err(_) => return Err(HasherError::InvalidArgon2Salt)
        };

        // Argon2 has a flexible hash length:
        let hash_length = match base64::decode_config(hash, base64::URL_SAFE_NO_PAD) {
            Ok(value) => value.len() as u32,
            Err(_) => return Ok(false)
        };

        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_argon2(password, salt, time_cost, memory_cost, parallelism, version, hash_length)))
    }

    fn encode(&self, password: &str, salt: &str, _: u32) -> String {
        // "Profile 1": Settings used in Django 1.10: This may change in the
        // future, if so, use the "iterations" parameter as a profile input,
        // and match against it:
        let memory_cost: u32 = 512;  // "kib" in Argon2's lingo.
        let time_cost: u32 = 2;  // "passes" in Argon2's lingo.
        let parallelism: u32 = 2;  // "lanes" in Argon2's lingo.
        let version: u32 = NEW_ARGON2_VERSION;
        let hash_length: u32 = 16;
        let hash = crypto_utils::hash_argon2(password, salt, time_cost, memory_cost, parallelism, version, hash_length);
        format!("argon2$argon2i$v=19$m={},t={},p={}${}${}", memory_cost, time_cost, parallelism, salt, hash)
    }

}

/// Hasher that uses the bcrypt key-derivation function with the password padded with SHA256.
#[cfg(feature="with_bcrypt")]
pub struct BCryptSHA256Hasher;

#[cfg(feature="with_bcrypt")]
impl Hasher for BCryptSHA256Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let bcrypt_encoded_part: Vec<&str> = encoded.splitn(2, '$').collect();
        let hash = bcrypt_encoded_part[1];
        let hashed_password = crypto_utils::hash_sha256(password);
        match bcrypt::verify(&hashed_password, hash) {
            Ok(valid) => Ok(valid),
            Err(_) => Ok(false)
        }
    }

    fn encode(&self, password: &str, _: &str, iterations: u32) -> String {
        let hashed_password = crypto_utils::hash_sha256(password);
        let hash = bcrypt::hash(&hashed_password, iterations).unwrap();
        format!("{}${}", "bcrypt_sha256", hash)
    }
}

/// Hasher that uses the bcrypt key-derivation function without password padding.
#[cfg(feature="with_bcrypt")]
pub struct BCryptHasher;

#[cfg(feature="with_bcrypt")]
impl Hasher for BCryptHasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let bcrypt_encoded_part: Vec<&str> = encoded.splitn(2, '$').collect();
        let hash = bcrypt_encoded_part[1];
        match bcrypt::verify(password, hash) {
            Ok(valid) => Ok(valid),
            Err(_) => Ok(false)
        }
    }

    fn encode(&self, password: &str, _: &str, iterations: u32) -> String {
        let hash = bcrypt::hash(password, iterations).unwrap();
        format!("{}${}", "bcrypt", hash)
    }
}

/// Hasher that uses the SHA1 hashing function over the salted password.
#[cfg(feature="with_legacy")]
pub struct SHA1Hasher;

#[cfg(feature="with_legacy")]
impl Hasher for SHA1Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let mut encoded_part = encoded.split('$').skip(1);
        let salt = encoded_part.next().ok_or(HasherError::BadHash)?;
        let hash = encoded_part.next().ok_or(HasherError::BadHash)?;
        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_sha1(password, salt)))
    }

    fn encode(&self, password: &str, salt: &str, _: u32) -> String {
        let hash = crypto_utils::hash_sha1(password, salt);
        format!("{}${}${}", "sha1", salt, hash)
    }
}

/// Hasher that uses the MD5 hashing function over the salted password.
#[cfg(feature="with_legacy")]
pub struct MD5Hasher;

#[cfg(feature="with_legacy")]
impl Hasher for MD5Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let mut encoded_part = encoded.split('$').skip(1);
        let salt = encoded_part.next().ok_or(HasherError::BadHash)?;
        let hash = encoded_part.next().ok_or(HasherError::BadHash)?;
        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_md5(password, salt)))
    }

    fn encode(&self, password: &str, salt: &str, _: u32) -> String {
        let hash = crypto_utils::hash_md5(password, salt);
        format!("{}${}${}", "md5", salt, hash)
    }
}

/// Hasher that uses the SHA1 hashing function with no salting.
#[cfg(feature="with_legacy")]
pub struct UnsaltedSHA1Hasher;

#[cfg(feature="with_legacy")]
impl Hasher for UnsaltedSHA1Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let mut encoded_part = encoded.split('$').skip(2);
        let hash = encoded_part.next().ok_or(HasherError::BadHash)?;
        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_sha1(password, "")))
    }

    fn encode(&self, password: &str, _: &str, _: u32) -> String {
        let hash = crypto_utils::hash_sha1(password, "");
        format!("{}$${}", "sha1", hash)
    }
}

/// Hasher that uses the MD5 hashing function with no salting.
#[cfg(feature="with_legacy")]
pub struct UnsaltedMD5Hasher;

#[cfg(feature="with_legacy")]
impl Hasher for UnsaltedMD5Hasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        Ok(crypto_utils::safe_eq(encoded, crypto_utils::hash_md5(password, "")))
    }

    fn encode(&self, password: &str, _: &str, _: u32) -> String {
        crypto_utils::hash_md5(password, "").to_string()
    }
}

/// Hasher that uses the UNIX's crypt(3) hash function.
#[cfg(feature="with_legacy")]
pub struct CryptHasher;

#[cfg(feature="with_legacy")]
impl Hasher for CryptHasher {
    fn verify(&self, password: &str, encoded: &str) -> Result<bool, HasherError> {
        let mut encoded_part = encoded.split('$').skip(2);
        let hash = encoded_part.next().ok_or(HasherError::BadHash)?;
        Ok(crypto_utils::safe_eq(hash, crypto_utils::hash_unix_crypt(password, hash)))
    }

    fn encode(&self, password: &str, salt: &str, _: u32) -> String {
        let hash = crypto_utils::hash_unix_crypt(password, salt);
        format!("{}$${}", "crypt", hash)
    }
}