use std::sync::Arc;

use async_lock::RwLock;
use bank_core::{
    ApiError, NameOrUuid, TokenResponse,
    account::{Account, UserAccountInfo},
    chat::{Chat, ChatInfo, ChatMessage, SendMessage, StartChat},
    meta::{Bank, Motd},
    pagination::{Pagination, RequestPagination},
    transaction::{Direction, Transaction},
    user::{User, UserAccounts, UserBalance},
};
use reqwest::{Method, RequestBuilder, header::CONTENT_TYPE};
use serde::de::DeserializeOwned;
use serde_json::json;
use thiserror::Error;
use url::Url;
use uuid::Uuid;

pub struct HttpClient {
    url: Url,
    client: reqwest::Client,
}

#[derive(Debug, Error)]
pub enum ClientError {
    #[error("url: {_0}")]
    Url(#[from] url::ParseError),
    #[error("request: {_0}")]
    Reqwest(#[from] reqwest::Error),
    #[error("unexpected content type")]
    UnexpectedContentType,
    #[error("api: {_0:?}")]
    Api(ApiError<'static>),
    #[error("json: {_0:?}")]
    Json(serde_json::Error),
}

impl HttpClient {
    fn make_request(
        &self,
        method: reqwest::Method,
        url: impl MakeUrl,
    ) -> Result<RequestBuilder, url::ParseError> {
        let url = url.make_url(self.url.clone())?;
        Ok(self.client.request(method, url))
    }

    pub fn get(&self, url: impl MakeUrl) -> Result<RequestBuilder, url::ParseError> {
        self.make_request(Method::GET, url)
    }

    pub fn post(&self, url: impl MakeUrl) -> Result<RequestBuilder, url::ParseError> {
        self.make_request(Method::POST, url)
    }

    pub fn put(&self, url: impl MakeUrl) -> Result<RequestBuilder, url::ParseError> {
        self.make_request(Method::PUT, url)
    }

    async fn credentials_request(
        &self,
        path: &str,
        username: &str,
        password: &str,
    ) -> Result<TokenResponse, ClientError> {
        let response = self
            .client
            .post(path)
            .json(&json!({ "username": username, "password": password }))
            .send()
            .await?;
        let body = handle_response::<TokenResponse>(response).await?;
        Ok(body)
    }

    pub fn login(
        &self,
        username: &str,
        password: &str,
    ) -> impl Future<Output = Result<TokenResponse, ClientError>> {
        self.credentials_request("/api/login", username, password)
    }

    pub fn register(
        &self,
        username: &str,
        password: &str,
    ) -> impl Future<Output = Result<TokenResponse, ClientError>> {
        self.credentials_request("/api/register", username, password)
    }
}

pub struct ApiClient {
    client: HttpClient,
    token: RwLock<Arc<str>>,
}

impl ApiClient {
    async fn credentials_request(
        &self,
        fut: impl Future<Output = Result<TokenResponse, ClientError>>,
    ) -> Result<(), ClientError> {
        let mut token = self.token.write().await;
        let body = fut.await?;
        *token = body.token.into();
        Ok(())
    }

    pub fn login(
        &self,
        username: &str,
        password: &str,
    ) -> impl Future<Output = Result<(), ClientError>> {
        self.credentials_request(self.client.login(username, password))
    }

    pub fn register(
        &self,
        username: &str,
        password: &str,
    ) -> impl Future<Output = Result<(), ClientError>> {
        self.credentials_request(self.client.register(username, password))
    }

    async fn token(&self) -> Arc<str> {
        (*self.token.read().await).clone()
    }

    #[inline]
    pub const fn users(&self) -> UsersApi {
        UsersApi { api: self }
    }

    #[inline]
    pub const fn accounts(&self) -> AccountsApi {
        AccountsApi { api: self }
    }

    #[inline]
    pub const fn chats(&self) -> ChatsApi {
        ChatsApi { api: self }
    }
}

pub async fn handle_response<T: DeserializeOwned>(
    response: reqwest::Response,
) -> Result<T, ClientError> {
    let response = response.error_for_status()?;
    let content_type = response.headers().get(CONTENT_TYPE).expect("content-type");
    if content_type != "application/json" {
        return Err(ClientError::UnexpectedContentType);
    }
    let status = response.status();
    let bytes = response.bytes().await?;
    if status.is_success() {
        serde_json::from_slice::<T>(&bytes).map_err(ClientError::Json)
    } else {
        let mut error =
            serde_json::from_slice::<ApiError<'static>>(&bytes).map_err(ClientError::Json)?;
        error.status = status;
        Err(ClientError::Api(error))
    }
}

macro_rules! request {
    ($api:expr, $method:ident, $path:expr) => {{
        let api = &$api;
        api.client.$method($path)?.auth(api).await
    }};
}

pub struct MetaApi<'a> {
    api: &'a ApiClient,
}

impl MetaApi<'_> {
    pub async fn motd(&self) -> Result<Motd, ClientError> {
        let response = request!(self.api, get, "/api/meta/motd").send().await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn bank(&self) -> Result<Bank, ClientError> {
        let response = request!(self.api, get, "/api/meta/bank").send().await?;
        let body = handle_response(response).await?;
        Ok(body)
    }
}

pub struct UsersApi<'a> {
    api: &'a ApiClient,
}

impl UsersApi<'_> {
    pub async fn list(&self, limit: u64, offset: u64) -> Result<Pagination<User>, ClientError> {
        let response = request!(
            self.api,
            get,
            RequestUrl::simple(["api", "users"], limit, offset)
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn accounts(&self) -> Result<Vec<UserAccountInfo>, ClientError> {
        let response = request!(self.api, get, "/api/users/@me/accounts")
            .send()
            .await?;
        let body = handle_response::<UserAccounts>(response).await?;
        Ok(body.result)
    }

    pub async fn balance(&self) -> Result<u64, ClientError> {
        let response = request!(self.api, get, "/api/users/@me/balance")
            .send()
            .await?;
        let body = handle_response::<UserBalance>(response).await?;
        Ok(body.balance)
    }

    pub async fn transactions(
        &self,
        direction: Option<Direction>,
        limit: u64,
        offset: u64,
    ) -> Result<Pagination<Transaction>, ClientError> {
        let response = request!(
            self.api,
            get,
            RequestUrl {
                path: ["api", "users", "@me", "transactions"],
                pagination: RequestPagination { limit, offset },
                extra_query: direction.map(|dir| ("direction", dir))
            }
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }
}

pub struct AccountsApi<'a> {
    api: &'a ApiClient,
}

impl AccountsApi<'_> {
    pub async fn list(&self, limit: u64, offset: u64) -> Result<Pagination<Account>, ClientError> {
        let response = request!(
            self.api,
            get,
            RequestUrl::simple(["api", "accounts"], limit, offset)
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn transactions(
        &self,
        id: Uuid,
        direction: Option<Direction>,
        limit: u64,
        offset: u64,
    ) -> Result<Pagination<Transaction>, ClientError> {
        let response = request!(
            self.api,
            get,
            RequestUrl {
                path: ["api", "accounts", &id.to_string(), "transactions"],
                pagination: RequestPagination { limit, offset },
                extra_query: direction.map(|dir| ("direction", dir))
            }
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }
}

pub struct ChatsApi<'a> {
    api: &'a ApiClient,
}

impl ChatsApi<'_> {
    pub async fn list(&self, limit: u64, offset: u64) -> Result<Pagination<ChatInfo>, ClientError> {
        let response = request!(
            self.api,
            get,
            RequestUrl::simple(["api", "chats"], limit, offset)
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn start(&self, user: impl Into<NameOrUuid>) -> Result<Chat, ClientError> {
        let response = request!(self.api, get, "/api/chats")
            .json(&StartChat { user: user.into() })
            .send()
            .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn info(&self, id: Uuid) -> Result<ChatInfo, ClientError> {
        let response = request!(self.api, get, ["api", "chats", &id.to_string()])
            .send()
            .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn messages(
        &self,
        chat: Uuid,
        limit: u64,
        offset: u64,
    ) -> Result<Pagination<ChatMessage>, ClientError> {
        let response = request!(
            self.api,
            get,
            RequestUrl::simple(["api", "chats", &chat.to_string()], limit, offset)
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn send(
        &self,
        chat: Uuid,
        message: &SendMessage,
    ) -> Result<Pagination<ChatMessage>, ClientError> {
        let response = request!(
            self.api,
            get,
            ["api", "chats", &chat.to_string(), "messages"]
        )
        .json(message)
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }

    pub async fn mark_read(
        &self,
        chat: Uuid,
        message: Uuid,
    ) -> Result<Pagination<ChatMessage>, ClientError> {
        let response = request!(
            self.api,
            get,
            [
                "api",
                "chats",
                &chat.to_string(),
                "messages",
                &message.to_string(),
                "read"
            ]
        )
        .send()
        .await?;
        let body = handle_response(response).await?;
        Ok(body)
    }
}

trait RequestBuilderExt {
    async fn auth(self, api: &ApiClient) -> Self;
}

impl RequestBuilderExt for RequestBuilder {
    async fn auth(self, api: &ApiClient) -> Self {
        self.bearer_auth(api.token().await)
    }
}

pub trait MakeUrl {
    fn make_url(self, base: Url) -> Result<Url, url::ParseError>;
}

impl MakeUrl for &'_ str {
    fn make_url(self, base: Url) -> Result<Url, url::ParseError> {
        base.join(self)
    }
}

impl<'a> MakeUrl for &'a [&'a str] {
    fn make_url(self, mut base: Url) -> Result<Url, url::ParseError> {
        base.path_segments_mut().unwrap().extend(self);
        Ok(base)
    }
}
impl<'a, const N: usize> MakeUrl for [&'a str; N] {
    fn make_url(self, mut base: Url) -> Result<Url, url::ParseError> {
        base.path_segments_mut().unwrap().extend(self);
        Ok(base)
    }
}

impl<'a, P, S, Q, K, V> MakeUrl for (P, Q)
where
    Q: IntoIterator<Item = (K, V)>,
    P: IntoIterator<Item = S>,
    S: AsRef<str>,
    K: AsRef<str>,
    V: AsRef<str>,
{
    fn make_url(self, mut base: Url) -> Result<Url, url::ParseError> {
        base.path_segments_mut().unwrap().extend(self.0);
        base.query_pairs_mut().extend_pairs(self.1);
        Ok(base)
    }
}

pub struct RequestUrl<P, Q> {
    path: P,
    pagination: RequestPagination,
    extra_query: Q,
}

impl<'a, P: IntoIterator<Item = &'a str>> RequestUrl<P, ()> {
    pub fn simple(
        path: P,
        limit: u64,
        offset: u64,
    ) -> RequestUrl<P, std::iter::Empty<(String, String)>> {
        RequestUrl {
            path,
            pagination: RequestPagination { limit, offset },
            extra_query: std::iter::empty(),
        }
    }
}

macro_rules! num {
    ($num:expr) => {
        itoa::Buffer::new().format($num)
    };
}

impl<'a, P, Q, K, V> MakeUrl for RequestUrl<P, Q>
where
    P: IntoIterator<Item = &'a str>,
    Q: IntoIterator<Item = (K, V)>,
    K: AsRef<str>,
    V: AsRef<str>,
{
    fn make_url(self, mut base: Url) -> Result<Url, url::ParseError> {
        base.path_segments_mut().unwrap().extend(self.path);
        let mut query = base.query_pairs_mut();
        query.extend_pairs([
            ("limit", num!(self.pagination.limit)),
            ("offset", num!(self.pagination.offset)),
        ]);
        query.extend_pairs(self.extra_query);
        drop(query);
        Ok(base)
    }
}