// Copyright (C) 2018  Vincent Ambo <mail@tazj.in>
//
// This file is part of Converse.
//
// Converse is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public
// License along with this program. If not, see
// <http://www.gnu.org/licenses/>.

//! This module contains the implementation of converse's actix-web
//! HTTP handlers.
//!
//! Most handlers have an associated rendering function using one of
//! the tera templates stored in the `/templates` directory in the
//! project root.

use actix::prelude::*;
use actix_web::*;
use actix_web::http::Method;
use actix_web::middleware::identity::RequestIdentity;
use actix_web::middleware::{Started, Middleware};
use actix_web;
use db::*;
use errors::ConverseError;
use futures::Future;
use mime_guess::guess_mime_type;
use models::*;
use oidc::*;
use render::*;

type ConverseResponse = Box<Future<Item=HttpResponse, Error=ConverseError>>;

const HTML: &'static str = "text/html";
const ANONYMOUS: i32 = 1;
const NEW_THREAD_LENGTH_ERR: &'static str = "Title and body can not be empty!";

/// Represents the state carried by the web server actors.
pub struct AppState {
    /// Address of the database actor
    pub db: Addr<Syn, DbExecutor>,

    /// Address of the OIDC actor
    pub oidc: Addr<Syn, OidcExecutor>,

    /// Address of the rendering actor
    pub renderer: Addr<Syn, Renderer>,
}

pub fn forum_index(state: State<AppState>) -> ConverseResponse {
    state.db.send(ListThreads)
        .flatten()
        .and_then(move |res| state.renderer.send(IndexPage {
            threads: res
        }).from_err())
        .flatten()
        .map(|res| HttpResponse::Ok().content_type(HTML).body(res))
        .responder()
}

/// Returns the ID of the currently logged in user. If there is no ID
/// present, the ID of the anonymous user will be returned.
pub fn get_user_id(req: &HttpRequest<AppState>) -> i32 {
    if let Some(id) = req.identity() {
        // If this .expect() call is triggered, someone is likely
        // attempting to mess with their cookies. These requests can
        // be allowed to fail without further ado.
        id.parse().expect("Session cookie contained invalid data!")
    } else {
        ANONYMOUS
    }
}

/// This handler retrieves and displays a single forum thread.
pub fn forum_thread(state: State<AppState>,
                    req: HttpRequest<AppState>,
                    thread_id: Path<i32>) -> ConverseResponse {
    let id = thread_id.into_inner();
    let user = get_user_id(&req);

    state.db.send(GetThread(id))
        .flatten()
        .and_then(move |res| state.renderer.send(ThreadPage {
            current_user: user,
            thread: res.0,
            posts: res.1,
        }).from_err())
        .flatten()
        .map(|res| HttpResponse::Ok().content_type(HTML).body(res))
        .responder()
}

/// This handler presents the user with the "New Thread" form.
pub fn new_thread(state: State<AppState>) -> ConverseResponse {
    state.renderer.send(NewThreadPage::default()).flatten()
        .map(|res| HttpResponse::Ok().content_type(HTML).body(res))
        .responder()
}

#[derive(Deserialize)]
pub struct NewThreadForm {
    pub title: String,
    pub post: String,
}

/// This handler receives a "New thread"-form and redirects the user
/// to the new thread after creation.
pub fn submit_thread(state: State<AppState>,
                     input: Form<NewThreadForm>,
                     req: HttpRequest<AppState>) -> ConverseResponse {
    // Trim whitespace out of inputs:
    let input = NewThreadForm {
        title: input.title.trim().into(),
        post: input.post.trim().into(),
    };

    // Perform simple validation and abort here if it fails:
    if input.title.is_empty() || input.post.is_empty() {
        return state.renderer
            .send(NewThreadPage {
                alerts: vec![NEW_THREAD_LENGTH_ERR],
                title: Some(input.title),
                post: Some(input.post),
            })
            .flatten()
            .map(|res| HttpResponse::Ok().content_type(HTML).body(res))
            .responder();
    }

    let user_id = get_user_id(&req);

    let new_thread = NewThread {
        user_id,
        title: input.title,
    };

    let msg = CreateThread {
        new_thread,
        post: input.post,
    };

    state.db.send(msg)
        .from_err()
        .and_then(move |res| {
            let thread = res?;
            info!("Created new thread \"{}\" with ID {}", thread.title, thread.id);
            Ok(HttpResponse::SeeOther()
               .header("Location", format!("/thread/{}", thread.id))
               .finish())
        })
        .responder()
}

#[derive(Deserialize)]
pub struct NewPostForm {
    pub thread_id: i32,
    pub post: String,
}

/// This handler receives a "Reply"-form and redirects the user to the
/// new post after creation.
pub fn reply_thread(state: State<AppState>,
                    input: Form<NewPostForm>,
                    req: HttpRequest<AppState>) -> ConverseResponse {
    let user_id = get_user_id(&req);

    let new_post = NewPost {
        user_id,
        thread_id: input.thread_id,
        body: input.post.trim().into(),
    };

    state.db.send(CreatePost(new_post))
        .flatten()
        .from_err()
        .and_then(move |post| {
            info!("Posted reply {} to thread {}", post.id, post.thread_id);
            Ok(HttpResponse::SeeOther()
               .header("Location", format!("/thread/{}#post-{}", post.thread_id, post.id))
               .finish())
        })
        .responder()
}

/// This handler presents the user with the form to edit a post. If
/// the user attempts to edit a post that they do not have access to,
/// they are currently ungracefully redirected back to the post
/// itself.
pub fn edit_form(state: State<AppState>,
                 req: HttpRequest<AppState>,
                 query: Path<GetPost>) -> ConverseResponse {
    let user_id = get_user_id(&req);

    state.db.send(query.into_inner())
        .flatten()
        .from_err()
        .and_then(move |post| {
            if user_id != 1 && post.user_id == user_id {
                return Ok(post);
            }

            Err(ConverseError::PostEditForbidden {
                user: user_id,
                id: post.id,
            })
        })
        .and_then(move |post| {
            let edit_msg = EditPostPage {
                id: post.id,
                post: post.body,
            };

            state.renderer.send(edit_msg).from_err()
        })
        .flatten()
        .map(|page| HttpResponse::Ok().content_type(HTML).body(page))
        .responder()
}

/// This handler "executes" an edit to a post if the current user owns
/// the edited post.
pub fn edit_post(state: State<AppState>,
                 req: HttpRequest<AppState>,
                 update: Form<UpdatePost>) -> ConverseResponse {
    let user_id = get_user_id(&req);

    state.db.send(GetPost { id: update.post_id })
        .flatten()
        .from_err()
        .and_then(move |post| {
            if user_id != 1 && post.user_id == user_id {
                 Ok(())
            } else {
                Err(ConverseError::PostEditForbidden {
                    user: user_id,
                    id: post.id,
                })
            }
        })
        .and_then(move |_| state.db.send(update.0).from_err())
        .flatten()
        .map(|updated| HttpResponse::SeeOther()
             .header("Location", format!("/thread/{}#post-{}",
                                         updated.thread_id, updated.id))
             .finish())
        .responder()
}

/// This handler executes a full-text search on the forum database and
/// displays the results to the user.
pub fn search_forum(state: State<AppState>,
                    query: Query<SearchPosts>) -> ConverseResponse {
    let query_string = query.query.clone();
    state.db.send(query.into_inner())
        .flatten()
        .and_then(move |results| state.renderer.send(SearchResultPage {
            results,
            query: query_string,
        }).from_err())
        .flatten()
        .map(|res| HttpResponse::Ok().content_type(HTML).body(res))
        .responder()
}

/// This handler initiates an OIDC login.
pub fn login(state: State<AppState>) -> ConverseResponse {
    state.oidc.send(GetLoginUrl)
        .from_err()
        .and_then(|url| Ok(HttpResponse::TemporaryRedirect()
                           .header("Location", url)
                           .finish()))
        .responder()
}

/// This handler handles an OIDC callback (i.e. completed login).
///
/// Upon receiving the callback, a token is retrieved from the OIDC
/// provider and a user lookup is performed. If a user with a matching
/// email-address is found in the database, it is logged in -
/// otherwise a new user is created.
pub fn callback(state: State<AppState>,
                data: Form<CodeResponse>,
                mut req: HttpRequest<AppState>) -> ConverseResponse {
    state.oidc.send(RetrieveToken(data.0)).flatten()
        .map(|author| LookupOrCreateUser {
            email: author.email,
            name: author.name,
        })
        .and_then(move |msg| state.db.send(msg).from_err()).flatten()
        .and_then(move |user| {
            info!("Completed login for user {} ({})", user.email, user.id);
            req.remember(user.id.to_string());
            Ok(HttpResponse::SeeOther()
               .header("Location", "/")
               .finish())})
        .responder()
}

/// This is an extension trait to enable easy serving of embedded
/// static content.
///
/// It is intended to be called with `include_bytes!()` when setting
/// up the actix-web application.
pub trait EmbeddedFile {
    fn static_file(self, path: &'static str, content: &'static [u8]) -> Self;
}

impl EmbeddedFile for App<AppState> {
    fn static_file(self, path: &'static str, content: &'static [u8]) -> Self {
        self.route(path, Method::GET, move |_: HttpRequest<_>| {
            let mime = format!("{}", guess_mime_type(path));
            HttpResponse::Ok()
                .content_type(mime.as_str())
                .body(content)
        })
    }
}

/// Middleware used to enforce logins unceremoniously.
pub struct RequireLogin;

impl <S> Middleware<S> for RequireLogin {
    fn start(&self, req: &mut HttpRequest<S>) -> actix_web::Result<Started> {
        let logged_in = req.identity().is_some();
        let is_oidc_req = req.path().starts_with("/oidc");

        if !is_oidc_req && !logged_in {
            Ok(Started::Response(
                HttpResponse::SeeOther()
                    .header("Location", "/oidc/login")
                    .finish()
            ))
        } else {
            Ok(Started::Done)
        }
    }
}