//! Various user types. Some types marked server-only to help prevent
//! leaking passwords to the frontend

use serde::{Deserialize, Serialize};

/// Standard informational user type, contains no password information
#[derive(Clone, Debug, Deserialize, Serialize)]
#[cfg_attr(feature = "server", derive(Queryable, Selectable, Identifiable))]
#[cfg_attr(feature = "server", diesel(table_name = crate::schema::users,
        check_for_backend(diesel::pg::Pg)))]
pub struct User {
    pub id: i32,
    pub username: String,
    pub created_at: chrono::DateTime<chrono::Local>,
}

/// Plaintext user credentials, used for login/signup form
#[derive(Deserialize, Serialize)]
pub struct UserCredentials {
    pub username: String,
    pub password: String,
}

cfg_if::cfg_if! {
if #[cfg(feature = "server")] {

use diesel::{
    deserialize::{FromSql, FromSqlRow},
    expression::AsExpression,
    prelude::*,
    serialize::ToSql,
    sql_types,
};
use pbkdf2::{
    PasswordHasher, PasswordVerifier, Pbkdf2, password_hash::Error::PasswordInvalid,
    phc::PasswordHash,
};

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

/// Newtype for a `String`-represented hashed password
#[derive(Clone, Debug, AsExpression, FromSqlRow)]
#[diesel(sql_type = sql_types::Text)]
pub struct HashedPassword(String);

impl HashedPassword {
    /// Check a password attempt against this hashed password
    ///
    /// # Returns
    ///
    /// `Ok(true)` for a correct password
    /// `Ok(false)` for an incorrect password
    /// `Err` for a hashing error
    pub fn check(&self, password_attempt: String) -> Result<bool> {
        let pw_hash = PasswordHash::new(&self.0)
            .map_err(|e| Error::message_here(format!("Error parsing `HashedPassword`: {e}")))?;

        match Pbkdf2::default().verify_password(password_attempt.as_bytes(), &pw_hash) {
            Ok(()) => Ok(true),
            Err(PasswordInvalid) => Ok(false),
            Err(e) => Err(Error::message_here(format!(
                "Error comparing password attempt against hash: {e}"
            ))),
        }
    }

    /// Returns the "session auth hash" for `axum-login`, just the hashed password as bytes
    pub fn auth_hash(&self) -> &[u8] {
        self.0.as_bytes()
    }
}

impl<DB> FromSql<diesel::sql_types::Text, DB> for HashedPassword
where
    DB: diesel::backend::Backend,
    String: FromSql<sql_types::Text, DB>,
{
    fn from_sql(bytes: DB::RawValue<'_>) -> diesel::deserialize::Result<Self> {
        Ok(Self(String::from_sql(bytes)?))
    }
}

impl<DB> ToSql<diesel::sql_types::Text, DB> for HashedPassword
where
    DB: diesel::backend::Backend,
    String: ToSql<sql_types::Text, DB>,
{
    fn to_sql<'b>(
        &'b self,
        out: &mut diesel::serialize::Output<'b, '_, DB>,
    ) -> diesel::serialize::Result {
        self.0.to_sql(out)
    }
}

/// User as it appears in the database, with hashed password
#[derive(Clone, Debug, Identifiable, Queryable, Selectable)]
#[diesel(table_name = crate::schema::users, check_for_backend(diesel::pg::Pg))]
pub struct DbUser {
    pub id: i32,
    pub username: String,
    pub hashed_password: HashedPassword,
    pub created_at: chrono::DateTime<chrono::Local>,
}

impl From<DbUser> for User {
    fn from(db_user: DbUser) -> Self {
        User {
            id: db_user.id,
            username: db_user.username,
            created_at: db_user.created_at,
        }
    }
}

/// User credentials with hashed password
#[derive(Clone, Debug, Insertable, Queryable, Selectable)]
#[diesel(table_name = crate::schema::users, check_for_backend(diesel::pg::Pg))]
pub struct HashedUserCredentials {
    username: String,
    hashed_password: HashedPassword,
}

impl From<DbUser> for HashedUserCredentials {
    fn from(db_user: DbUser) -> Self {
        HashedUserCredentials {
            username: db_user.username,
            hashed_password: db_user.hashed_password,
        }
    }
}

impl UserCredentials {
    /// Attempt to convert into `HashedUserCredentials` by hashing the password. Yields a PBKDF2
    /// error on failure.
    pub fn try_hash(self) -> Result<HashedUserCredentials, pbkdf2::password_hash::Error> {
        let hashed_password = Pbkdf2::default().hash_password(self.password.as_bytes())?;

        Ok(HashedUserCredentials {
            username: self.username,
            hashed_password: HashedPassword(hashed_password.to_string()),
        })
    }
}

}
}