//! Top level connection object that hold a http client (either synchronous or
//! asynchronous), arango URL, and buffered accessible databases object.
//!
//! ## Establishing connections
//! There is three way to establish connections:
//! - jwt
//! - basic auth
//! - no authentication
//!
//! So are the `arangors` API:
//! Example:
//!
//! - With authentication
//!
//! ```rust
//! use arangors::Connection;
//!
//! # #[cfg_attr(any(feature="reqwest_async"), maybe_async::maybe_async, tokio::main)]
//! # #[cfg_attr(any(feature="surf_async"), maybe_async::maybe_async, async_std::main)]
//! # #[cfg_attr(feature = "blocking", maybe_async::must_be_sync)]
//! # async fn main() {
//! let conn = Connection::establish_jwt("http://localhost:8529", "username", "password")
//!     .await
//!     .unwrap();
//! let conn = Connection::establish_basic_auth("http://localhost:8529", "username", "password")
//!     .await
//!     .unwrap();
//! # }
//! ```
//!
//! - No authentication
//! ```rust, ignore
//! use arangors::Connection;
//! let conn = Connection::establish_without_auth("http://localhost:8529").await.unwrap();
//! ```

use std::{collections::HashMap, fmt::Debug, sync::Arc};

use base64::{engine::general_purpose, Engine as _};
use http::header::{HeaderMap, AUTHORIZATION, SERVER};
use log::{debug, trace};
use maybe_async::maybe_async;
use serde::{Deserialize, Serialize};
use serde_json::Value;
use uclient::ClientExt;
use url::Url;

use crate::{response::ArangoResult, ClientError};

use super::{database::Database, response::deserialize_response};

#[cfg(feature = "cluster")]
use self::options::{ClusterHealth, CreateDatabase, CreateDatabaseOptions};

use self::{
    auth::Auth,
    role::{Admin, Normal},
};

mod auth;
pub mod options;

pub mod role {
    #[derive(Debug)]
    pub struct Normal;

    #[derive(Debug)]
    pub struct Admin;
}

#[derive(Deserialize, Serialize, Debug)]
pub enum Permission {
    #[serde(rename = "none")]
    NoAccess,
    #[serde(rename = "ro")]
    ReadOnly,
    #[serde(rename = "rw")]
    ReadWrite,
}

#[derive(Debug, Deserialize)]
pub struct Version {
    pub server: String,
    pub version: String,
    pub license: String,
}

#[cfg(any(feature = "reqwest_async", feature = "reqwest_blocking"))]
pub type Connection = GenericConnection<uclient::reqwest::ReqwestClient>;

#[cfg(feature = "surf_async")]
pub type Connection = GenericConnection<uclient::surf::SurfClient>;

/// Connection is the top level API for this crate.
/// It contains a http client, information about authentication, arangodb url.
#[derive(Debug, Clone)]
pub struct GenericConnection<C: ClientExt, S = Normal> {
    session: Arc<C>,
    arango_url: Url,
    username: String,
    #[allow(dead_code)]
    state: S,
}

impl<S, C: ClientExt> GenericConnection<C, S> {
    /// Validate the server at given arango url
    ///
    /// Cast `ClientError` if
    /// - Invalid url
    /// - Connection failed
    /// - SERVER header in response header is not `ArangoDB` or empty
    #[maybe_async]
    pub async fn validate_server(arango_url: &str) -> Result<(), ClientError> {
        let client = C::new(None)?;
        let resp = client.get(arango_url.parse().unwrap(), "").await?;
        // have `Server` in header
        match resp.headers().get(SERVER) {
            Some(server) => {
                // value of `Server` is `ArangoDB`
                let server_value = server.to_str().unwrap();
                if server_value.eq_ignore_ascii_case("ArangoDB") {
                    trace!("Validate arangoDB server done.");
                    Ok(())
                } else {
                    Err(ClientError::InvalidServer(server_value.to_owned()))
                }
            }
            None => Err(ClientError::InvalidServer("Unknown".to_owned())),
        }
    }

    /// Get url for remote arangoDB server.
    pub fn url(&self) -> &Url {
        &self.arango_url
    }

    /// Get HTTP session.
    ///
    /// Users can use this method to get a authorized session to access
    /// arbitrary path on arangoDB Server.
    ///
    /// TODO This method should only be public in this crate when all features
    ///     are implemented.
    pub fn session(&self) -> Arc<C> {
        Arc::clone(&self.session)
    }

    /// Get database object with name.
    ///
    /// # Note
    /// this function would make a request to arango server.
    #[maybe_async]
    pub async fn db(&self, name: &str) -> Result<Database<C>, ClientError> {
        let db = Database::new(name, self.url(), self.session());
        db.info().await?;
        Ok(db)
    }

    /// Get a list of accessible database
    ///
    /// This function uses the API that is used to retrieve a list of
    /// all databases the current user can access.
    ///
    /// # Note
    /// this function would make a request to arango server.
    #[maybe_async]
    pub async fn accessible_databases(&self) -> Result<HashMap<String, Permission>, ClientError> {
        let url = self
            .arango_url
            .join(&format!("/_api/user/{}/database", &self.username))
            .unwrap();
        let resp = self.session.get(url, "").await?;
        let result: ArangoResult<HashMap<String, Permission>> = deserialize_response(resp.body())?;
        Ok(result.unwrap())
    }

    // Returns the role of a server in a cluster. The role is returned in the role
    // attribute of the result
    ///
    /// Possible return values for role are:
    /// SINGLE: the server is a standalone server without clustering
    /// COORDINATOR: the server is a Coordinator in a cluster
    /// PRIMARY: the server is a DB-Server in a cluster
    /// SECONDARY: this role is not used anymore
    /// AGENT: the server is an Agency node in a cluster
    /// UNDEFINED: in a cluster, UNDEFINED is returned if the server role cannot
    /// be determined.
    ///
    /// # Note
    /// this function would make a request to arango server.
    #[maybe_async]
    pub async fn server_role(&self) -> Result<String, ClientError> {
        let url = self.arango_url.join("/_admin/server/role").unwrap();
        let resp = self.session.get(url, "").await?;
        let result: HashMap<String, Value> = deserialize_response(resp.body())?;

        Ok(result.get("role").unwrap().as_str().unwrap().to_owned())
    }

    /// Returns the health of the cluster as assessed by the supervision
    /// (Agency)
    ///
    /// # Note
    /// this function would make a request to arango server.
    #[maybe_async]
    #[cfg(feature = "cluster")]
    pub async fn cluster_health(&self) -> Result<ClusterHealth, ClientError> {
        let url = self.arango_url.join("/_admin/cluster/health").unwrap();
        let resp = self.session.get(url, "").await?;
        let result: ClusterHealth = deserialize_response(resp.body())?;

        Ok(result)
    }
}

impl<C: ClientExt> GenericConnection<C, Normal> {
    /// Establish connection to ArangoDB sever with Auth.
    ///
    /// The connection is establish in the following steps:
    /// 1. validate if it is a arangoDB server at the given base url
    /// 1. set authentication in header
    /// 1. build a http client that holds authentication tokens
    /// 1. construct databases objects for later use
    ///
    /// The most secure way to connect to a arangoDB server is via JWT
    /// token authentication, along with TLS encryption.
    #[maybe_async]
    async fn establish<T: Into<String>>(
        arango_url: T,
        auth: Auth<'_>,
    ) -> Result<GenericConnection<C, Normal>, ClientError> {
        let url_str = arango_url.into();
        let arango_url = Url::parse(&url_str)
            .map_err(|_| ClientError::InvalidServer(format!("invalid url: {}", url_str)))?
            .join("/")
            .unwrap();

        Self::validate_server(&url_str).await?;

        let username: String;
        let authorization = match auth {
            Auth::Basic(cred) => {
                username = String::from(cred.username);

                let token = general_purpose::STANDARD_NO_PAD
                    .encode(format!("{}:{}", cred.username, cred.password));
                Some(format!("Basic {}", token))
            }
            Auth::Jwt(cred) => {
                username = String::from(cred.username);

                let token = Self::jwt_login(&arango_url, cred.username, cred.password).await?;
                Some(format!("Bearer {}", token))
            }
            Auth::None => {
                username = String::from("root");
                None
            }
        };

        let mut headers = HeaderMap::new();
        if let Some(value) = authorization {
            headers.insert(AUTHORIZATION, value.parse().unwrap());
        }

        debug!("Established");
        Ok(GenericConnection {
            arango_url,
            username,
            session: Arc::new(C::new(headers)?),
            state: Normal,
        })
    }

    /// Establish connection to ArangoDB sever without Authentication.
    ///
    /// The target server **MUST DISABLE** authentication for all requests,
    /// which should only used for **test purpose**.
    ///
    /// Disable authentication means all operations are performed by root user.
    ///
    /// Example:
    /// ```rust, ignore
    /// use arangors::Connection;
    ///
    /// let conn = Connection::establish_without_auth("http://localhost:8529").await.unwrap();
    /// ```
    #[maybe_async]
    pub async fn establish_without_auth<T: Into<String>>(
        arango_url: T,
    ) -> Result<GenericConnection<C, Normal>, ClientError> {
        trace!("Establish without auth");
        GenericConnection::establish(arango_url.into(), Auth::None).await
    }

    /// Establish connection to ArangoDB sever with basic auth.
    ///
    /// Example:
    /// ```rust
    /// use arangors::Connection;
    ///
    /// # #[cfg_attr(any(feature="reqwest_async"), maybe_async::maybe_async, tokio::main)]
    /// # #[cfg_attr(any(feature="surf_async"), maybe_async::maybe_async, async_std::main)]
    /// # #[cfg_attr(feature="blocking", maybe_async::must_be_sync)]
    /// # async fn main() {
    /// let conn = Connection::establish_basic_auth("http://localhost:8529", "username", "password")
    ///     .await
    ///     .unwrap();
    /// # }
    /// ```
    #[maybe_async]
    pub async fn establish_basic_auth(
        arango_url: &str,
        username: &str,
        password: &str,
    ) -> Result<GenericConnection<C, Normal>, ClientError> {
        trace!("Establish with basic auth");
        GenericConnection::establish(arango_url, Auth::basic(username, password)).await
    }

    /// Establish connection to ArangoDB sever with jwt authentication.
    ///
    /// Prefered way to interact with arangoDB server.
    ///
    /// JWT token expires after 1 month.
    ///
    /// Example:
    ///
    /// ```rust
    /// use arangors::Connection;
    ///
    /// # #[cfg_attr(any(feature="reqwest_async"), maybe_async::maybe_async, tokio::main)]
    /// # #[cfg_attr(any(feature="surf_async"), maybe_async::maybe_async, async_std::main)]
    /// # #[cfg_attr(feature = "blocking", maybe_async::must_be_sync)]
    /// # async fn main() {
    /// let conn = Connection::establish_jwt("http://localhost:8529", "username", "password")
    ///     .await
    ///     .unwrap();
    /// # }
    /// ```
    #[maybe_async]
    pub async fn establish_jwt(
        arango_url: &str,
        username: &str,
        password: &str,
    ) -> Result<GenericConnection<C, Normal>, ClientError> {
        trace!("Establish with jwt");
        GenericConnection::establish(arango_url, Auth::jwt(username, password)).await
    }

    #[maybe_async]
    async fn jwt_login<T: Into<String>>(
        arango_url: &Url,
        username: T,
        password: T,
    ) -> Result<String, ClientError> {
        #[derive(Deserialize)]
        struct Jwt {
            pub jwt: String,
        }
        let url = arango_url.join("/_open/auth").unwrap();

        let mut map = HashMap::new();
        map.insert("username", username.into());
        map.insert("password", password.into());

        let jwt: Jwt = deserialize_response(
            C::new(None)?
                .post(url, &serde_json::to_string(&map)?)
                .await?
                .body(),
        )?;
        Ok(jwt.jwt)
    }

    /// Create a database via HTTP request and add it into `self.databases`.
    ///
    /// If creation fails, an Error is cast. Otherwise, a bool is returned to
    /// indicate whether the database is correctly created.
    ///
    /// # Example
    /// ```rust
    /// use arangors::Connection;
    /// # #[cfg_attr(any(feature="reqwest_async"), maybe_async::maybe_async, tokio::main)]
    /// # #[cfg_attr(any(feature="surf_async"), maybe_async::maybe_async, async_std::main)]
    /// # #[cfg_attr(feature = "blocking", maybe_async::must_be_sync)]
    /// # async fn main() {
    /// let conn = Connection::establish_jwt("http://localhost:8529", "root", "KWNngteTps7XjrNv")
    ///     .await
    ///     .unwrap();
    /// let result = conn.create_database("new_db").await.unwrap();
    /// println!("{:?}", result);
    ///
    /// let result = conn.drop_database("new_db").await.unwrap();
    /// println!("{:?}", result);
    /// # }
    /// ```
    /// TODO tweak options on creating database
    ///
    /// # Note
    /// this function would make a request to arango server.
    #[maybe_async]
    pub async fn create_database(&self, name: &str) -> Result<Database<C>, ClientError> {
        let mut map = HashMap::new();
        map.insert("name", name);
        let url = self.arango_url.join("/_api/database").unwrap();

        let resp = self
            .session
            .post(url, &serde_json::to_string(&map)?)
            .await?;

        deserialize_response::<ArangoResult<bool>>(resp.body())?;
        self.db(name).await
    }

    #[maybe_async]
    #[cfg(feature = "cluster")]
    pub async fn create_database_with_options(
        &self,
        name: &str,
        options: CreateDatabaseOptions,
    ) -> Result<Database<C>, ClientError> {
        let url = self.arango_url.join("/_api/database").unwrap();
        let final_options = CreateDatabase::builder()
            .name(name)
            .options(options)
            .build();

        let resp = self
            .session
            .post(url, &serde_json::to_string(&final_options)?)
            .await?;

        deserialize_response::<ArangoResult<bool>>(resp.body())?;
        self.db(name).await
    }

    /// Drop database with name.
    ///
    /// # Note
    /// this function would make a request to arango server.
    #[maybe_async]
    pub async fn drop_database(&self, name: &str) -> Result<(), ClientError> {
        let url_path = format!("/_api/database/{}", name);
        let url = self.arango_url.join(&url_path).unwrap();

        let resp = self.session.delete(url, "").await?;
        deserialize_response::<ArangoResult<bool>>(resp.body())?;
        Ok(())
    }

    #[maybe_async]
    pub async fn into_admin(self) -> Result<GenericConnection<C, Admin>, ClientError> {
        let dbs = self.accessible_databases().await?;
        let db = dbs
            .get("_system")
            .ok_or(ClientError::InsufficientPermission {
                permission: Permission::NoAccess,
                operation: String::from("access to _system database"),
            })?;
        match db {
            Permission::ReadWrite => Ok(self.into()),
            _ => Err(ClientError::InsufficientPermission {
                permission: Permission::ReadOnly,
                operation: String::from("write to _system database"),
            }),
        }
    }
}

impl<C: ClientExt> GenericConnection<C, Admin> {
    pub fn into_normal(self) -> GenericConnection<C, Normal> {
        self.into()
    }
}

impl<C: ClientExt> From<GenericConnection<C, Normal>> for GenericConnection<C, Admin> {
    fn from(conn: GenericConnection<C, Normal>) -> GenericConnection<C, Admin> {
        GenericConnection {
            arango_url: conn.arango_url,
            session: conn.session,
            username: conn.username,
            state: Admin,
        }
    }
}

impl<C: ClientExt> From<GenericConnection<C, Admin>> for GenericConnection<C, Normal> {
    fn from(conn: GenericConnection<C, Admin>) -> GenericConnection<C, Normal> {
        GenericConnection {
            arango_url: conn.arango_url,
            session: conn.session,
            username: conn.username,
            state: Normal,
        }
    }
}