use lmdb::{DatabaseFlags, Environment, Transaction, WriteFlags};
use std::collections::{HashMap};
use rkyv::Infallible;

use std::sync::Arc;
use anyhow::Context;

use rkyv::{Archived, Deserialize};
use rkyv::ser::Serializer;
use rkyv::ser::serializers::AllocSerializer;
use crate::db;
use crate::db::{AlignedAdapter, ArchivedValue, DB, RawDB};

#[derive(
    Clone,
    PartialEq,
    Eq,
    Debug,
    rkyv::Archive,
    rkyv::Serialize,
    rkyv::Deserialize,
    serde::Serialize,
    serde::Deserialize,
)]
pub struct User {
    pub id: String,
    pub userdata: UserData,
}

impl User {
    pub fn check_password(&self, pwd: &[u8]) -> anyhow::Result<bool> {
        if let Some(ref encoded) = self.userdata.passwd {
            argon2::verify_encoded(encoded, pwd)
                .context("Stored password is an invalid string")
        } else {
            Ok(false)
        }
    }
}

#[derive(
Clone,
PartialEq,
Eq,
Debug,
rkyv::Archive,
rkyv::Serialize,
rkyv::Deserialize,
serde::Serialize,
serde::Deserialize,
)]
/// Data on an user to base decisions on
///
/// This of course includes authorization data, i.e. that users set roles
pub struct UserData {
    /// A Person has N ≥ 0 roles.
    /// Persons are only ever given roles, not permissions directly
    pub roles: Vec<String>,

    #[serde(skip_serializing_if = "Option::is_none")]
    #[serde(default)]
    pub passwd: Option<String>,

    /// Additional data storage
    #[serde(flatten, skip_serializing_if = "HashMap::is_empty")]
    kv: HashMap<String, String>,
}

impl UserData {
    pub fn new(roles: Vec<String>) -> Self {
        Self { roles, kv: HashMap::new(), passwd: None }
    }
    pub fn new_with_kv(roles: Vec<String>, kv: HashMap<String, String>) -> Self {
        Self { roles, kv, passwd: None }
    }
}

#[derive(Clone, Debug)]
pub struct UserDB {
    env: Arc<Environment>,
    db: DB<AlignedAdapter<User>>,
}

impl UserDB {
    pub unsafe fn new(env: Arc<Environment>, db: RawDB) -> Self {
        let db = DB::new(db);
        Self { env, db }
    }

    pub unsafe fn open(env: Arc<Environment>) -> Result<Self, db::Error> {
        let db = RawDB::open(&env, Some("user"))?;
        Ok(Self::new(env, db))
    }

    pub unsafe fn create(env: Arc<Environment>) -> Result<Self, db::Error> {
        let flags = DatabaseFlags::empty();
        let db = RawDB::create(&env, Some("user"), flags)?;
        Ok(Self::new(env, db))
    }

    pub fn get(&self, uid: &str) -> Result<Option<ArchivedValue<User>>, db::Error> {
        let txn = self.env.begin_ro_txn()?;
        self.db.get(&txn, &uid.as_bytes())
    }

    pub fn put(&self, uid: &str, user: &User) -> Result<(), db::Error> {
        let mut serializer = AllocSerializer::<1024>::default();
        serializer.serialize_value(user).expect("rkyv error");
        let v = serializer.into_serializer().into_inner();
        let value = ArchivedValue::new(v);

        let mut txn = self.env.begin_rw_txn()?;
        let flags = WriteFlags::empty();
        self.db.put(&mut txn, &uid.as_bytes(), &value, flags)?;
        txn.commit()?;
        Ok(())
    }

    pub fn get_all(&self) -> Result<Vec<(String, User)>, db::Error> {
        let txn = self.env.begin_ro_txn()?;
        let mut iter = self.db.get_all(&txn)?;
        let mut out = Vec::new();
        for (uid, user) in iter {
            let uid = unsafe { std::str::from_utf8_unchecked(uid).to_string() };
            let user: User = Deserialize::<User, _>::deserialize(user.as_ref(), &mut Infallible).unwrap();
            out.push((uid, user));
        }

        Ok(out)
    }
}