pub(crate) mod crypter;
pub(crate) mod from;

use self::crypter::{Crypter, CrypterError};
use crate::{
    AddressType, Credential, CredentialType, IdentityId, SecdError, API_TOKEN_SIZE_BYTES,
    CREDENTIAL_PUBLIC_PART_BYTES, SESSION_DURATION, SESSION_SIZE_BYTES,
};
use base64::{engine::general_purpose, Engine as _};
use sha2::{Digest, Sha256};
use std::str::from_utf8;
use time::OffsetDateTime;
use uuid::Uuid;

pub(crate) fn hash(i: &[u8]) -> Vec<u8> {
    let mut hasher = Sha256::new();
    hasher.update(i);
    hasher.finalize().to_vec()
}

pub trait ErrorContext<T, E: std::error::Error> {
    fn ctx(self, err: &str) -> Result<T, E>;
}

impl<T, E: std::error::Error> ErrorContext<T, E> for Result<T, E> {
    fn ctx(self, err: &str) -> Result<T, E> {
        self.map_err(|e| {
            log::error!("{} [{}]", err, e.to_string());
            e
        })
    }
}

impl AddressType {
    pub fn get_value(&self) -> Option<String> {
        match &self {
            AddressType::Email { email_address } => email_address.as_ref().map(|a| a.to_string()),
            AddressType::Sms { phone_number } => phone_number.as_ref().cloned(),
        }
    }
}

impl CredentialType {
    pub fn new_api_token() -> Result<Self, SecdError> {
        let public = general_purpose::URL_SAFE_NO_PAD.encode(
            (0..CREDENTIAL_PUBLIC_PART_BYTES)
                .map(|_| rand::random::<u8>())
                .collect::<Vec<u8>>(),
        );

        let private = general_purpose::URL_SAFE_NO_PAD.encode(
            (0..API_TOKEN_SIZE_BYTES)
                .map(|_| rand::random::<u8>())
                .collect::<Vec<u8>>(),
        );

        Ok(CredentialType::ApiToken { public, private })
    }

    pub fn session_from_str(token: &str) -> Result<Self, SecdError> {
        let decoded = general_purpose::URL_SAFE_NO_PAD
            .decode(token)
            .map_err(|e| SecdError::DecodeError(e.to_string()))?;

        let key =
            general_purpose::URL_SAFE_NO_PAD.encode(&decoded[0..CREDENTIAL_PUBLIC_PART_BYTES]);
        let secret =
            general_purpose::URL_SAFE_NO_PAD.encode(&decoded[CREDENTIAL_PUBLIC_PART_BYTES..]);

        Ok(CredentialType::Session { key, secret })
    }

    pub fn api_token_from_str(token: &str) -> Result<Self, SecdError> {
        let decoded = general_purpose::URL_SAFE_NO_PAD
            .decode(token)
            .map_err(|e| SecdError::DecodeError(e.to_string()))?;

        let public = general_purpose::URL_SAFE_NO_PAD.encode(
            &decoded
                .get(0..CREDENTIAL_PUBLIC_PART_BYTES)
                .ok_or(SecdError::CredentialIsNotApiToken)
                .ctx("insufficent number of bytes to find credential's public part")?,
        );
        let private = general_purpose::URL_SAFE_NO_PAD.encode(
            &decoded
                .get(CREDENTIAL_PUBLIC_PART_BYTES..)
                .ok_or(SecdError::CredentialIsNotApiToken)
                .ctx("insufficent number of bytes to find credential's secret part")?,
        );

        Ok(CredentialType::ApiToken { public, private })
    }

    pub fn session_token(&self) -> Result<String, SecdError> {
        match self {
            CredentialType::Session { key, secret } => {
                let key_bytes = general_purpose::URL_SAFE_NO_PAD
                    .decode(key)
                    .map_err(|e| SecdError::DecodeError(e.to_string()))?;
                let secret_bytes = general_purpose::URL_SAFE_NO_PAD
                    .decode(secret)
                    .map_err(|e| SecdError::DecodeError(e.to_string()))?;

                let mut input = key_bytes;
                input.extend(secret_bytes);

                Ok(general_purpose::URL_SAFE_NO_PAD.encode(input))
            }
            _ => Err(SecdError::InvalidCredential),
        }
        .ctx("the credential type is not a session")
    }

    pub fn api_token(&self) -> Result<String, SecdError> {
        match self {
            CredentialType::ApiToken { public, private } => {
                let public_bytes = general_purpose::URL_SAFE_NO_PAD
                    .decode(public)
                    .map_err(|e| SecdError::DecodeError(e.to_string()))?;
                let private_bytes = general_purpose::URL_SAFE_NO_PAD
                    .decode(private)
                    .map_err(|e| SecdError::DecodeError(e.to_string()))?;

                let mut input = public_bytes;
                input.extend(private_bytes);

                Ok(general_purpose::URL_SAFE_NO_PAD.encode(input))
            }
            _ => Err(SecdError::InvalidCredential),
        }
        .ctx("the credential type is not an api token")
    }
}

impl Credential {
    pub fn new_session(identity_id: IdentityId) -> Result<Self, SecdError> {
        let key = (0..CREDENTIAL_PUBLIC_PART_BYTES)
            .map(|_| rand::random::<u8>())
            .collect::<Vec<u8>>();

        let secret = (0..SESSION_SIZE_BYTES)
            .map(|_| rand::random::<u8>())
            .collect::<Vec<u8>>();

        let now = OffsetDateTime::now_utc();
        Ok(Credential {
            id: Uuid::new_v4(),
            identity_id,
            t: CredentialType::Session {
                key: general_purpose::URL_SAFE_NO_PAD.encode(key),
                secret: general_purpose::URL_SAFE_NO_PAD.encode(secret),
            },
            created_at: now,
            revoked_at: Some(
                now.checked_add(time::Duration::new(SESSION_DURATION, 0))
                    .ok_or(SecdError::Todo)?,
            ),
            deleted_at: None,
        })
    }

    pub fn encrypt(&mut self, crypter: &Crypter) -> Result<(), SecdError> {
        match self.t {
            CredentialType::ApiToken {
                ref mut private, ..
            } => {
                *private = hex::encode(crypter.encrypt(private.as_bytes())?);
            }
            CredentialType::Passphrase { ref mut value, .. } => {
                *value = hex::encode(crypter.encrypt(value.as_bytes())?);
            }
            CredentialType::Session { ref mut secret, .. } => {
                *secret = hex::encode(crypter.encrypt(secret.as_bytes())?);
            }
        };
        Ok(())
    }
    pub fn decrypt(&mut self, crypter: &Crypter) -> Result<(), SecdError> {
        match self.t {
            CredentialType::ApiToken {
                ref mut private, ..
            } => {
                *private = from_utf8(
                    &crypter.decrypt(
                        &hex::decode(private.clone())
                            .map_err(|e| CrypterError::Decode(e.to_string()))?,
                    )?,
                )
                .map_err(|e| CrypterError::Decode(e.to_string()))?
                .to_string()
            }
            CredentialType::Passphrase { ref mut value, .. } => {
                *value = from_utf8(&crypter.decrypt(
                    &hex::decode(value.clone()).map_err(|e| CrypterError::Decode(e.to_string()))?,
                )?)
                .map_err(|e| CrypterError::Decode(e.to_string()))?
                .to_string()
            }
            CredentialType::Session { ref mut secret, .. } => {
                *secret = from_utf8(
                    &crypter.decrypt(
                        &hex::decode(secret.clone())
                            .map_err(|e| CrypterError::Decode(e.to_string()))?,
                    )?,
                )
                .map_err(|e| CrypterError::Decode(e.to_string()))?
                .to_string()
            }
        };
        Ok(())
    }

    pub fn hash(&mut self, crypter: &Crypter) -> Result<(), SecdError> {
        match self.t {
            CredentialType::ApiToken {
                ref mut private, ..
            } => {
                *private = crypter.weak_hash(private.as_bytes())?;
            }
            CredentialType::Passphrase { ref mut value, .. } => {
                *value = crypter.hash(value.as_bytes(), None)?;
            }
            CredentialType::Session { ref mut secret, .. } => {
                *secret = crypter.weak_hash(secret.as_bytes())?;
            }
        };
        Ok(())
    }

    pub fn hash_compare(
        &mut self,
        plaintext: &CredentialType,
        crypter: &Crypter,
    ) -> Result<(), SecdError> {
        match (&self.t, plaintext) {
            (
                CredentialType::ApiToken {
                    public: current_public,
                    private: current_private,
                },
                CredentialType::ApiToken {
                    public: plaintext_public,
                    private: plaintext_private,
                },
            ) => {
                let plaintext_hash = crypter.weak_hash(plaintext_private.as_bytes())?;
                if plaintext_public != current_public || &plaintext_hash != current_private {
                    return Err(SecdError::InvalidCredential);
                }
            }
            (
                CredentialType::Passphrase {
                    key: current_key,
                    value: current_value,
                },
                CredentialType::Passphrase {
                    key: plaintext_key,
                    value: plaintext_value,
                },
            ) => {
                let plaintext_hash =
                    crypter.hash(plaintext_value.as_bytes(), Some(current_value))?;
                if plaintext_key != current_key || &plaintext_hash != current_value {
                    return Err(SecdError::InvalidCredential);
                }
            }
            (
                CredentialType::Session {
                    key: current_key,
                    secret: current_secret,
                },
                CredentialType::Session {
                    key: plaintext_key,
                    secret: plaintext_secret,
                },
            ) => {
                let plaintext_hash = crypter.weak_hash(plaintext_secret.as_bytes())?;
                if plaintext_key != current_key || &plaintext_hash != current_secret {
                    return Err(SecdError::InvalidCredential);
                }
            }
            _ => panic!(
                "unreachable 78cfff7c-5493-42c5-add7-044241b3d713 [different credential types]"
            ),
        }

        Ok(())
    }
}

#[cfg(test)]
mod test {
    use uuid::Uuid;

    use super::*;

    #[test]
    fn test_credential_encrypt() {
        let c = Crypter::new("AMAZING_KEY".as_bytes());

        let plaintext_secret = "super_password".to_string();

        let mut credential = Credential {
            id: Uuid::new_v4(),
            identity_id: Uuid::new_v4(),
            t: CredentialType::Passphrase {
                key: "super_user".into(),
                value: plaintext_secret.clone(),
            },
            created_at: OffsetDateTime::now_utc(),
            revoked_at: None,
            deleted_at: None,
        };

        credential.encrypt(&c).unwrap();
        match &credential.t {
            CredentialType::Passphrase { key: _, value } => {
                assert_ne!(plaintext_secret.clone(), value.clone())
            }
            _ => {}
        };

        credential.decrypt(&c).unwrap();
        match &credential.t {
            CredentialType::Passphrase { key: _, value } => {
                assert_eq!(plaintext_secret.clone(), value.clone())
            }
            _ => {}
        };
    }
}