use std::{
    collections::HashMap,
    path::PathBuf,
    sync::Arc,
    time::{Duration, SystemTime, UNIX_EPOCH},
};

use argon2::{
    password_hash::{rand_core::OsRng, Encoding, PasswordHashString, SaltString},
    Argon2, PasswordHash, PasswordHasher,
};
use nanoid::nanoid;
use serde::{de::Unexpected, Deserialize, Serialize};
use serde_json::{Map, Value};
use tap::{Pipe, Tap};
use tokio::sync::{RwLock, RwLockReadGuard};

#[derive(Clone)]
pub struct Store(Arc<RwLock<StoreInner>>);

impl Store {
    pub async fn load(path: PathBuf) -> eyre::Result<Self> {
        let mut inner = StoreInner::new(path.clone());
        if path.try_exists()? {
            let mut map: Map<String, Value> =
                { std::fs::File::open(&path)?.pipe(serde_json::from_reader)? };
            let accounts: Vec<Account> =
                serde_json::from_value(map.remove("accounts").unwrap_or_default())?;
            let apps: Vec<App> = serde_json::from_value(map.remove("apps").unwrap_or_default())?;
            for mut account in accounts {
                account.tokens = account
                    .tokens
                    .into_iter()
                    .filter(|token| token.expires > SystemTime::now())
                    .collect();
                for token in &account.tokens {
                    inner.token_map.insert(
                        token.value.clone(),
                        (account.name.clone(), token.expires.clone()),
                    );
                }
                inner.accounts.insert(account.name.clone(), account);
            }
            for app in apps {
                inner.apps.insert(app.name.clone(), app);
            }
            inner.invites = serde_json::from_value(map.remove("invites").unwrap_or_default())?;
            inner.invites = inner
                .invites
                .into_iter()
                .filter(|invite| invite.expires > SystemTime::now())
                .collect();
        } else {
            Self::save(&mut inner).await?;
        }
        Ok(Store(Arc::new(RwLock::new(inner))))
    }

    async fn save(inner: &mut StoreInner) -> std::io::Result<()> {
        let mut map: Map<String, Value> = Map::new();
        map.insert(
            "accounts".into(),
            serde_json::to_value(inner.accounts.values().collect::<Vec<_>>()).unwrap(),
        );
        map.insert(
            "apps".into(),
            serde_json::to_value(inner.apps.values().collect::<Vec<_>>()).unwrap(),
        );
        map.insert(
            "invites".into(),
            serde_json::to_value(&inner.invites).unwrap(),
        );
        let data = serde_json::to_vec_pretty(&map).unwrap();
        let mut temp = inner.path.clone();
        temp.set_file_name(
            temp.file_name()
                .unwrap_or_default()
                .to_os_string()
                .tap_mut(|name| name.push(".tmp")),
        );
        tokio::fs::write(&temp, data).await?;
        tokio::fs::rename(temp, &inner.path).await?;
        Ok(())
    }

    pub async fn get_account(&self, name: &str) -> Option<RwLockReadGuard<'_, Account>> {
        let guard = self.0.read().await;
        RwLockReadGuard::try_map(guard, |guard| guard.accounts.get(name)).ok()
    }

    pub async fn create_account(&self, name: &str, password: &str) -> std::io::Result<bool> {
        let hash = Argon2::default()
            .hash_password(password.as_bytes(), &SaltString::generate(&mut OsRng))
            .unwrap()
            .pipe(|hash| hash.serialize())
            .pipe(OwnedPasswordHash::from);
        let mut guard = self.0.write().await;
        if guard.accounts.get(name).is_some() {
            return Ok(false);
        }
        guard.accounts.insert(
            name.to_string(),
            Account {
                name: name.to_string(),
                password: hash,
                tokens: Default::default(),
                scopes: Default::default(),
            },
        );
        Self::save(&mut guard).await?;
        Ok(true)
    }

    pub async fn delete_account(&self, name: &str) -> std::io::Result<()> {
        let mut guard = self.0.write().await;
        if let Some(account) = guard.accounts.remove(name) {
            for token in account.tokens {
                guard.token_map.remove(&token.value);
            }
            Self::save(&mut guard).await
        } else {
            Ok(())
        }
    }

    pub async fn update_account(
        &self,
        name: &str,
        with: impl FnOnce(&mut Account),
    ) -> std::io::Result<bool> {
        let mut guard = self.0.write().await;
        if let Some(account) = guard.accounts.get_mut(name) {
            with(account);
            Self::save(&mut guard).await.map(|_| true)
        } else {
            Ok(false)
        }
    }

    pub async fn list_accounts(&self) -> Vec<String> {
        self.0
            .read()
            .await
            .accounts
            .values()
            .map(|account| account.name.clone())
            .collect()
    }

    pub async fn create_token(&self, name: &str) -> std::io::Result<Option<String>> {
        let mut guard = self.0.write().await;
        let token = nanoid!(32);
        if let Some(account) = guard.accounts.get_mut(name) {
            let expires = SystemTime::now() + Duration::from_secs(60 * 60 * 24 * 30);
            account.tokens.push(ExpiringValue {
                value: token.clone(),
                expires: expires.clone(),
            });
            guard
                .token_map
                .insert(token.clone(), (name.to_string(), expires));
            Self::save(&mut guard).await?;
            Ok(Some(token))
        } else {
            Ok(None)
        }
    }

    pub async fn check_token(&self, token: &str) -> Option<(String, SystemTime)> {
        let guard = self.0.read().await;
        let Some((name, expires)) = guard.token_map.get(token) else {
            return None;
        };
        if *expires < SystemTime::now() {
            return None;
        }
        Some((name.clone(), expires.clone()))
    }

    pub async fn create_invite(&self) -> std::io::Result<String> {
        let mut guard = self.0.write().await;
        let invite = nanoid!(32);
        let expires = SystemTime::now() + Duration::from_secs(60 * 60 * 24 * 14);
        guard.invites.push(ExpiringValue {
            value: invite.clone(),
            expires,
        });
        Self::save(&mut guard).await?;
        Ok(invite)
    }

    pub async fn check_invite(&self, invite: &str) -> bool {
        let guard = self.0.read().await;
        let now = SystemTime::now();
        guard
            .invites
            .iter()
            .any(|check| check.expires > now && check.value == invite)
    }

    pub async fn use_invite(&self, invite: &str) -> std::io::Result<bool> {
        let mut guard = self.0.write().await;
        let now = SystemTime::now();
        if let Some((index, _)) = guard
            .invites
            .iter()
            .enumerate()
            .find(|(_, check)| check.expires > now && check.value == invite)
        {
            guard.invites.swap_remove(index);
            Self::save(&mut guard).await?;
            Ok(true)
        } else {
            Ok(false)
        }
    }
}

pub struct StoreInner {
    path: PathBuf,
    accounts: HashMap<String, Account>,
    apps: HashMap<String, App>,
    invites: Vec<ExpiringValue>,
    token_map: HashMap<String, (String, SystemTime)>,
}

impl StoreInner {
    fn new(at: PathBuf) -> Self {
        Self {
            path: at,
            accounts: Default::default(),
            apps: Default::default(),
            invites: Default::default(),
            token_map: Default::default(),
        }
    }
}

#[derive(serde::Serialize, serde::Deserialize)]
pub struct Account {
    pub name: String,
    pub password: OwnedPasswordHash,
    pub tokens: Vec<ExpiringValue>,
    pub scopes: Vec<String>,
}

#[ouroboros::self_referencing]
pub struct OwnedPasswordHash {
    owned: PasswordHashString,
    #[borrows(owned)]
    #[not_covariant]
    parsed: PasswordHash<'this>,
}

impl OwnedPasswordHash {
    pub fn from(inner: PasswordHashString) -> Self {
        OwnedPasswordHash::new(inner, |inner| inner.password_hash())
    }

    pub fn parsed(&self) -> PasswordHash {
        self.with_parsed(|x| x.clone())
    }
}

impl Serialize for OwnedPasswordHash {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        self.with_owned(|owned| owned.as_str().serialize(serializer))
    }
}

impl<'de> Deserialize<'de> for OwnedPasswordHash {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        Ok(String::deserialize(deserializer)?
            .pipe(|hash| {
                PasswordHashString::parse(&hash, Encoding::B64).map_err(|_| {
                    <D::Error as serde::de::Error>::invalid_value(
                        Unexpected::Str(&hash),
                        &"valid password hash",
                    )
                })
            })?
            .pipe(OwnedPasswordHash::from))
    }
}

pub struct ExpiringValue {
    pub value: String,
    pub expires: SystemTime,
}

impl Serialize for ExpiringValue {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        <(&str, u64)>::serialize(
            &(
                &self.value,
                (self.expires.duration_since(SystemTime::UNIX_EPOCH))
                    .unwrap()
                    .as_secs(),
            ),
            serializer,
        )
    }
}

impl<'de> Deserialize<'de> for ExpiringValue {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        <(String, u64)>::deserialize(deserializer).map(|(token, unix)| ExpiringValue {
            value: token,
            expires: UNIX_EPOCH + Duration::from_secs(unix),
        })
    }
}

#[derive(serde::Serialize, serde::Deserialize)]
pub struct App {
    name: String,
    secret: String,
}