//! Main logic

use crate::{models, prelude::*};
use async_trait::async_trait;
use async_tungstenite::tungstenite::Message;
use futures_util::{SinkExt, StreamExt};
use log::{debug, error};
use reqwest::{
    header::{self, HeaderMap, HeaderValue},
    Client, Method,
};
use serde::de::DeserializeOwned;
use serde_json::json;
use std::str::FromStr;

/// Authentication data, either a login_id and password
/// or a personal access token. Required for being able
/// to make calls to a Mattermost instance API.
///
/// For more information, see the
/// [Mattermost docs](https://api.mattermost.com/#tag/authentication).
#[derive(Debug)]
pub struct AuthenticationData {
    pub(crate) login_id: Option<String>,
    pub(crate) password: Option<String>,
    pub(crate) token: Option<String>,
}

impl AuthenticationData {
    /// Create a struct instance from a user's login_id and password.
    pub fn from_password(login_id: &str, password: &str) -> Self {
        Self {
            login_id: Some(login_id.to_owned()),
            password: Some(password.to_owned()),
            token: None,
        }
    }

    /// Create a struct instance from a user's personal access token.
    ///
    /// Personal access tokens must be enabled per instance by an admin.
    pub fn from_access_token(token: &str) -> Self {
        Self {
            login_id: None,
            password: None,
            token: Some(token.to_owned()),
        }
    }

    /// If the auth data is using a login_id and password.
    pub fn using_password(&self) -> bool {
        self.password.is_some()
    }

    /// If the auth data is using a personal access token.
    pub fn using_token(&self) -> bool {
        self.token.is_some()
    }
}

/// Handler trait for receving websocket messages.
#[async_trait]
pub trait WebsocketHandler: Send + Sync {
    /// Function to implement to receive websocket messages.
    async fn callback(&self, _message: Message) {}
}

/// Struct to interact with a Mattermost instance API.
#[derive(Debug)]
pub struct Mattermost {
    pub(crate) instance_url: String,
    pub(crate) authentication_data: AuthenticationData,
    pub(crate) client: Client,
    pub(crate) auth_token: Option<String>,
}

impl Mattermost {
    /// Create a new instance of the struct to interact with the instance API.
    ///
    /// The `instance_url` variable should be the root URL of your Mattermost
    /// instance.
    pub fn new(instance_url: &str, authentication_data: AuthenticationData) -> Self {
        let auth_token = authentication_data.token.clone();
        Self {
            instance_url: instance_url.to_owned(),
            authentication_data,
            client: Client::new(),
            auth_token,
        }
    }

    /// Get a session token from the stored login_id and password.
    /// Required when using login_id and password authentication,
    /// before making any calls to the instance API.
    ///
    /// Does nothing if the `AuthenticationData` this struct instance
    /// was created with used a personal access token.
    pub async fn store_session_token(&mut self) -> Result<(), ApiError> {
        if self.authentication_data.using_token() {
            debug!("Using personal access token; getting a session token is a no-op");
            return Ok(());
        }
        debug!("Getting a session token from login_id and password");
        let url = format!("{}/api/v4/users/login", self.instance_url);
        let resp = self
            .client
            .post(&url)
            .json(&json!({
                "login_id": self.authentication_data.login_id.as_ref().unwrap(),
                "password": self.authentication_data.password.as_ref().unwrap(),
            }))
            .send()
            .await?;
        let session_token = resp
            .headers()
            .get("Token")
            .ok_or_else(|| ApiError::CouldNotGetToken(resp.status().as_u16()))?;
        self.auth_token = Some(session_token.to_str()?.to_string());
        debug!("Session token retrieved and stored");
        Ok(())
    }

    /// Headers for interacting with the API.
    fn request_headers(&self) -> Result<HeaderMap, ApiError> {
        let mut map = HeaderMap::new();
        map.insert(header::ACCEPT, HeaderValue::from_static("application/json"));
        map.insert(
            header::CONTENT_TYPE,
            HeaderValue::from_static("application/json"),
        );
        map.insert(
            header::AUTHORIZATION,
            HeaderValue::from_str(&format!(
                "Bearer {}",
                self.auth_token.as_ref().ok_or(ApiError::MissingAuthToken)?
            ))?,
        );
        Ok(map)
    }

    /// Make a query to the Mattermost instance API.
    ///
    /// This method is "raw" in that the calling code must
    /// supply the method, query parameters, body, **and**
    /// a struct for the shape of the data returned (or
    /// `serde_json::Value` for "dynamic" data).
    ///
    /// Callers are encouraged to look for a specific endpoint
    /// function that is for the API endpoint that is desired,
    /// but this function is exposed to calling code so that
    /// this library can be more flexible.
    pub async fn query<T: DeserializeOwned>(
        &self,
        method: &str,
        endpoint: &str,
        query: Option<&[(&str, &str)]>,
        body: Option<&str>,
    ) -> Result<T, ApiError> {
        let url = format!("{}/api/v4/{}", self.instance_url, endpoint);
        debug!(
            "Making {} request to {} with query {:?}",
            method, url, query
        );
        let mut req_builder = self
            .client
            .request(Method::from_str(method)?, &url)
            .headers(self.request_headers()?)
            .query(query.unwrap_or_else(|| &[]));
        req_builder = match body {
            Some(b) => req_builder.body(b.to_owned()),
            None => req_builder,
        };
        let resp = self.client.execute(req_builder.build()?).await?;
        if !resp.status().is_success() {
            error!(
                "Got status {} when requesting data from {}",
                resp.status(),
                url
            );
            let status = resp.status().as_u16();
            // attempt to get the standard error information out and return that
            if let Ok(text) = resp.text().await {
                if let Ok(data) = serde_json::from_str::<MattermostError>(&text) {
                    return Err(ApiError::MattermostApiError(data));
                }
            }
            // fallback to generic HTTP status code error
            return Err(ApiError::StatusCodeError(status));
        }
        Ok(resp.json().await?)
    }

    /// Connect to the websocket API on the instance.
    ///
    /// This method loops, sending messages received from
    /// the websocket connection to the passed handler.
    ///
    /// This function handles the authentication handshake,
    /// but nothing else, yet.
    pub async fn connect_to_websocket<H: WebsocketHandler + 'static>(
        &mut self,
        handler: H,
    ) -> Result<(), ApiError> {
        let url = format!("{}/api/v4/websocket", self.instance_url).replace("https", "wss");
        let (mut stream, _response) = async_tungstenite::tokio::connect_async(url).await?;
        stream
            .send(Message::Text(serde_json::to_string(&json!({
              "seq": 1,
              "action": "authentication_challenge",
              "data": {
                "token": self.auth_token.as_ref().unwrap()
              }
            }))?))
            .await?;
        loop {
            if let Some(event) = stream.next().await {
                match event {
                    Ok(message) => match message {
                        Message::Text(_) => handler.callback(message).await,
                        Message::Binary(_) => debug!("Websocket binary message"),
                        Message::Ping(_) => debug!("Websocket ping message"),
                        Message::Pong(_) => debug!("Websocket pong message"),
                        Message::Close(_) => break,
                    },
                    Err(e) => {
                        error!("Error getting data from websocket: {}", e);
                    }
                }
            };
        }
        Ok(())
    }

    // ===========================================================================================
    //      API endpoints
    // ===========================================================================================

    /// Get a team's information.
    pub async fn get_team(&self, id: &str) -> Result<models::TeamInformation, ApiError> {
        self.query("GET", &format!("teams/{}", id), None, None)
            .await
    }

    /// Get information for a team by its name,
    pub async fn get_team_by_name(&self, name: &str) -> Result<models::TeamInformation, ApiError> {
        self.query("GET", &format!("teams/name/{}", name), None, None)
            .await
    }

    /// List teams that are open or, if the user has the "manage_system" permission, exist.
    pub async fn get_teams(&self) -> Result<Vec<models::TeamInformation>, ApiError> {
        self.query("GET", "teams", None, None).await
    }

    /// Get the number of unread messages and mentions for all member teams of the user.
    pub async fn get_team_unreads_for(
        &self,
        user_id: &str,
    ) -> Result<Vec<models::TeamsUnreadInformation>, ApiError> {
        self.query(
            "GET",
            &format!("users/{}/teams/unread", user_id),
            None,
            None,
        )
        .await
    }

    /// Get the number of unread messages and mentions for the specific team the user is in.
    ///
    /// Requires either the "read_channel" or "edit_other_users" permission.
    pub async fn get_team_unreads_for_in(
        &self,
        user_id: &str,
        team_id: &str,
    ) -> Result<models::TeamsUnreadInformation, ApiError> {
        self.query(
            "GET",
            &format!("users/{}/teams/{}/unread", user_id, team_id),
            None,
            None,
        )
        .await
    }

    /// Get all channels on the instance.
    ///
    /// Requires the "manage_system" permission.
    pub async fn get_all_channels(
        &self,
        not_associated_to_group: Option<&str>,
        page: Option<u64>,
        per_page: Option<u64>,
        exclude_default_channels: Option<bool>,
        exclude_policy_constrained: Option<bool>,
    ) -> Result<Vec<models::ChannelInformation>, ApiError> {
        let mut query: Vec<(&str, String)> = Vec::new();
        if let Some(v) = not_associated_to_group {
            query.push(("not_associated_to_group", v.to_owned()));
        }
        if let Some(v) = page {
            query.push(("page", v.to_string()));
        }
        if let Some(v) = per_page {
            query.push(("per_page", v.to_string()));
        }
        if let Some(v) = exclude_default_channels {
            query.push(("exclude_default_channels", v.to_string()));
        }
        if let Some(v) = exclude_policy_constrained {
            query.push(("exclude_policy_constrained", v.to_string()));
        }
        let query: Vec<(&str, &str)> = query.iter().map(|(a, b)| (*a, &**b)).collect();
        self.query("GET", "channels", Some(&query), None).await
    }

    /// Get a channel's information.
    ///
    /// Requires the "read_channel" permission for that channel.
    pub async fn get_channel(
        &self,
        channel_id: &str,
    ) -> Result<models::ChannelInformation, ApiError> {
        self.query("GET", &format!("channels/{}", channel_id), None, None)
            .await
    }

    /// Get public channels' information.
    ///
    /// Requires the "list_team_channels" permission.
    pub async fn get_public_channels(
        &self,
        team_id: &str,
    ) -> Result<Vec<models::ChannelInformation>, ApiError> {
        self.query("GET", &format!("teams/{}/channels", team_id), None, None)
            .await
    }
}