//! User and access regulation module
//!
//! Access can be given for a vault or file (based on id)
//! as well as an entire Api endpoint. By default all
//! Rust APIs assume `{ Api, Admin }` access, for other
//! APIs crates (http, ...), a user with access rights
//! has to be specified.
//!
//! A user for an API endpoint is not the same as a user for
//! a vault. An API admin could have access to a vault where
//! they can only read a single file!
//!
//! `User` is also a serialisable struct which contains important
//! data to load and store them into a metadata store.

mod auth;
mod tokens;
pub use self::auth::pam_authenticate;
pub use self::tokens::Token;
pub use errors::AuthError;

use crypto::{encoding, hashing, random};
use std::collections::HashMap;
use {
    meta::MetaDomain,
    traits::{AutoEncoder, Base64AutoEncoder},
};

/// Specifies access to a resource
#[derive(Hash, Serialize, Deserialize, Clone, PartialEq, Eq)]
pub enum Access {
    /// Allows access to vault metadata & index files
    Vault(Role),
    /// Allows access to a record resource inside a vault
    Record(Role, String),
}

impl AutoEncoder for Access {}

/// Specifies the capabilities of a user
#[derive(Hash, Serialize, Deserialize, Clone, PartialEq, Eq)]
pub enum Role {
    Reader,
    Editor,
    Admin,
}

impl AutoEncoder for Role {}

/// A generic user representation
///
/// A user has an identify check built in that can verify a passphrase
/// but is ultimately only a metadata item for a API layer. Any layer is
/// free to disregard these access rights (as such, they should not be
/// considered security, only obscurity/ management control)
///
/// A company might not want allow non-admins to create new vaults or
/// users to delete records. This does not cryptographically stop anyone
/// from breaking into the company server, swapping the source code and
/// changing the rules!
///
/// An user can have multiple role-access pairs
#[derive(Serialize, Deserialize, Clone)]
pub struct User {
    name: String,
    pw_hash: String,
    rights: HashMap<Access, Role>,
    token: Option<String>,
}

impl User {
    /// Register a new user with a name and password
    pub fn register(name: &str, pw: &str) -> Self {
        Self {
            name: name.into(),
            pw_hash: encoding::base64_encode(&hashing::blake2(pw, name).to_vec()),
            rights: HashMap::new(),
            token: None,
        }
    }
    /// Verify a user password input
    pub fn verify(&self, pw: &str) -> bool {
        self.pw_hash == encoding::base64_encode(&hashing::blake2(pw, &self.name).to_vec())
    }
    /// Provides a hook to use second-factor authentication to authorise
    /// 
    /// This is meant to be used with an external Yubikey
    pub fn second_auth_verify(&mut self) -> bool {
        unimplemented!()
    }
    /// Generate a token unique to this user (or return the existing one)
    pub fn token(&mut self) -> String {
        if self.token.is_none() {
            self.token = Some(encoding::base64_encode(&random::bytes(256)));
        }

        self.token.as_ref().unwrap().clone()
    }
    /// Verify that a user is allowed access to a piece of data
    ///
    /// `None` means "no access of any kind"
    pub fn has_access(&self, item: Access) -> Option<Role> {
        self.rights.get(&item).map(|i| i.clone())
    }
    /// Modify access to an item for a role or create a new access entry
    pub fn give_access(&mut self, item: Access, role: Role) {
        self.rights.insert(item, role);
    }
}

impl AutoEncoder for User {}

/// A utility structure that manages users and can be derived
/// from/into a metadata object. By default this process uses
/// base64 encoding.
///
/// The workflow for this is to create a new `UserStore`, add
/// users and then use `meta_push_domain` and give it the
/// `UserStore::into()` which is then encoded automatically.
/// The reverse action works the same way
#[derive(Serialize, Deserialize)]
pub struct UserStore {
    /// A map between username – user item
    users: HashMap<String, User>,
    registry: HashMap<String, Vec<Access>>,
}

impl UserStore {
    /// Generate a sign-up token for a new user which needs to be
    /// provided in order for them to create an account.
    pub fn get_token(&mut self, access: Vec<Access>) -> String {
        let token = ::crypto::encoding::base64_encode(&::crypto::random::bytes(128));
        self.registry.insert(
            token.clone(),
            if access.is_empty() {
                vec![Access::Vault(Role::Reader)]
            } else {
                access
            },
        );

        token
    }

    pub fn get_user(&self, name: &str) -> Option<&User> {
        self.users.get(name)
    }

    pub fn get_all(&self) -> &HashMap<String, User> {
        &self.users
    }

    pub fn add(&mut self, user: User) -> Option<()> {
        self.users.insert(user.name.clone(), user);
        Some(())
    }
}

impl Default for UserStore {
    fn default() -> Self {
        Self {
            users: HashMap::new(),
            registry: HashMap::new(),
        }
    }
}

impl AutoEncoder for UserStore {}

/// Allow users to turn MetaDomains
/// that *are* userstores into a UserStore easily
///
/// Will most likely `panic!` if called on a non UserStore
impl From<(MetaDomain, MetaDomain)> for UserStore {
    fn from((users, registry): (MetaDomain, MetaDomain)) -> Self {
        Self {
            users: users
                .all()
                .iter()
                .map(|(k, v)| {
                    (
                        k.clone(),
                        match v {
                            ::Payload::Text(s) => User::decode(&String::from_base64(s)).unwrap(),
                            _ => unreachable!(),
                        },
                    )
                })
                .collect(),
            registry: registry
                .all()
                .iter()
                .map(|(k, v)| {
                    (
                        k.clone(),
                        match v {
                            ::Payload::List(regs) => regs
                                .iter()
                                .map(|reg| {
                                    Access::decode(&String::from_base64(match reg {
                                        ::Payload::Text(s) => s,
                                        _ => unreachable!(),
                                    })).unwrap()
                                })
                                .collect(),
                            _ => unreachable!(),
                        },
                    )
                })
                .collect(),
        }
    }
}

impl From<UserStore> for (MetaDomain, MetaDomain) {
    fn from(us: UserStore) -> Self {
        (
            MetaDomain::new("userstore").fill(
                us.users
                    .iter()
                    .map(|(name, user)| {
                        (
                            name.clone(),
                            ::Payload::Text(user.encode().unwrap().to_base64()),
                        )
                    })
                    .collect(),
            ),
            MetaDomain::new("registry").fill(
                us.registry
                    .iter()
                    .map(|(name, reg)| {
                        (
                            name.clone(),
                            ::Payload::List(
                                reg.iter()
                                    .map(|reg| ::Payload::Text(reg.encode().unwrap().to_base64()))
                                    .collect(),
                            ),
                        )
                    })
                    .collect(),
            ),
        )
    }
}