mod comment;
pub use comment::*;

mod database;
pub use database::Database;

mod error;
pub use error::Error;

use actix_cors::Cors;
use actix_web::{get, post, web, App, HttpRequest, HttpResponse, HttpServer};
use clap::Parser;
use sanitize_html::{errors::SanitizeError, rules::predefined::DEFAULT, sanitize_str};
use scraper::{Html, Selector};
use serde::Deserialize;
use std::sync::Mutex;
use std::{collections::HashMap, sync::MutexGuard};
use validator::Validate;

struct AppState {
    databases: HashMap<String, Mutex<Database>>,
    arguments: Arguments,
}

impl AppState {
    fn get_db<'a>(&'a self, origin: Option<String>) -> Result<MutexGuard<'a, Database>, Error> {
        let origin = match origin {
            Some(origin) => origin,
            None => return Err(Error::InvalidOrigin),
        };
        match self.databases.get(&origin) {
            Some(database) => Ok(match database.lock() {
                Ok(database) => database,
                Err(_) => return Err(Error::DatabaseAccessError),
            }),
            None => return Err(Error::InvalidOrigin),
        }
    }
}

fn get_request_origin(request: &HttpRequest) -> Option<String> {
    match request.head().headers().get("Origin") {
        Some(origin) => match origin.to_str() {
            Ok(origin) => Some(origin.to_owned()),
            Err(_) => None,
        },
        None => None,
    }
}

#[derive(Default, Parser)]
#[clap(author, version, about)]
struct Arguments {
    #[clap(
        short,
        long,
        default_value = "8080",
        help = "Set port where HTTP requests will be received"
    )]
    port: u16,
    #[clap(
        required = true,
        min_values = 1,
        help = "Set sites where comments will be posted"
    )]
    sites: Vec<String>,
    #[clap(
        short,
        long,
        help = "Run in testing mode, with in-memory database(s) and permissive CORS policy"
    )]
    testing: bool,
    #[clap(short, long, help = "Require name for comment submissions")]
    name_required: bool,
    #[clap(short, long, help = "Require email for comment submissions")]
    email_required: bool,
}

async fn _get_comments(
    data: web::Data<AppState>,
    request: HttpRequest,
    content_id: web::Path<String>,
) -> Result<Vec<Comment>, Error> {
    let origin = get_request_origin(&request);
    match web::block(move || {
        Ok(
            match match data.get_db(origin) {
                Ok(database) => database,
                Err(err) => return Err(err),
            }
            .get_comments(&content_id)
            {
                Ok(comments) => comments,
                Err(_) => return Err(Error::DatabaseInternalError),
            },
        )
    })
    .await
    {
        Ok(result) => result,
        Err(_) => Err(Error::DatabaseAccessError),
    }
}

#[get("/{content_id}")]
async fn get_comments(
    data: web::Data<AppState>,
    request: HttpRequest,
    content_id: web::Path<String>,
) -> HttpResponse {
    match _get_comments(data, request, content_id).await {
        Ok(comments) => HttpResponse::Ok().json(comments),
        Err(err) => err.to_http_response(),
    }
}

#[derive(Deserialize)]
struct PostCommentsRequest {
    url: String,
    comment: Comment,
}

async fn _post_comment(
    data: web::Data<AppState>,
    request: HttpRequest,
    bytes: web::Bytes,
) -> Result<(), Error> {
    match String::from_utf8(bytes.to_vec()) {
        Ok(text) => {
            let PostCommentsRequest { url, comment } =
                match serde_json::from_str::<PostCommentsRequest>(&text) {
                    Ok(mut req) => {
                        let mut sanitize_req = || -> Result<(), SanitizeError> {
                            req.comment.text =
                                sanitize_str(&DEFAULT, &req.comment.text)?.replace("&gt;", ">"); // required for markdown quotes
                            if let Some(ref mut author) = req.comment.author {
                                *author = sanitize_str(&DEFAULT, &author)?;
                            }
                            Ok(())
                        };
                        if let Err(_) = sanitize_req() {
                            return Err(Error::SanitizationError);
                        }
                        req
                    }
                    Err(_) => {
                        return Err(Error::InvalidBody);
                    }
                };
            if comment.validate().is_err() {
                return Err(Error::InvalidFields);
            }
            if comment.author.is_none() && data.arguments.name_required {
                return Err(Error::NameRequired);
            }
            if comment.email.is_none() && data.arguments.email_required {
                return Err(Error::EmailRequired);
            }
            let origin = match get_request_origin(&request) {
                Some(origin) => origin,
                None => return Err(Error::InvalidOrigin),
            };
            // Check to see if provided URL is in scope.
            // This is to prevent malicious requests that try to get server to fetch external websites.
            // (requires loop because "labels on blocks are unstable")
            // https://github.com/rust-lang/rust/issues/48594
            'outer: loop {
                for site_root in data.databases.keys() {
                    if site_root.starts_with(&origin) && url.starts_with(site_root) {
                        break 'outer;
                    }
                }
                return Err(Error::InvalidUrl);
            }
            match get_page_data(&url).await {
                Ok(page_data_option) => match page_data_option {
                    Some(page_data) => {
                        if page_data.content_id != comment.content_id {
                            return Err(Error::InvalidContentId);
                        }
                    }
                    None => return Err(Error::InvalidUrl), // e.g. 404
                },
                Err(_) => {
                    return Err(Error::PageFetchError);
                }
            };
            match web::block(move || {
                let database = match data.get_db(Some(origin)) {
                    Ok(database) => database,
                    Err(err) => return Err(err),
                };
                if let Some(parent) = comment.parent {
                    'outer2: loop {
                        match database.get_comments(&comment.content_id) {
                            Ok(comments) => {
                                for other_comment in comments.iter() {
                                    if other_comment.id.unwrap() == parent {
                                        if other_comment.parent.is_none() {
                                            break 'outer2;
                                        }
                                        break;
                                    }
                                }
                            }
                            Err(_) => {
                                return Err(Error::DatabaseInternalError);
                            }
                        };
                        return Err(Error::InvalidParent);
                    }
                }
                if let Err(_) = database.create_comment(&comment) {
                    return Err(Error::DatabaseInternalError);
                }
                Ok(())
            })
            .await
            {
                Ok(result) => result,
                Err(_) => Err(Error::DatabaseAccessError),
            }
        }
        Err(_) => Err(Error::InvalidBody),
    }
}

#[post("/")]
async fn post_comment(
    data: web::Data<AppState>,
    request: HttpRequest,
    bytes: web::Bytes,
) -> HttpResponse {
    match _post_comment(data, request, bytes).await {
        Ok(_) => HttpResponse::Ok().finish(),
        Err(err) => err.to_http_response(),
    }
}

// Contains all page details stored in meta tags.
// Currently, only content_id, but this is wrapped in this struct
// to make adding other meta tags, such as locked comments, in the future
struct PageData {
    content_id: String,
}

async fn get_page_data(url: &str) -> Result<Option<PageData>, reqwest::Error> {
    let response = reqwest::get(url).await?;
    if !response.status().is_success() {
        return Ok(None);
    }
    let content = response.text_with_charset("utf-8").await?;
    let document = Html::parse_document(&content);
    let get_meta = |name: &str| -> Option<String> {
        let selector = Selector::parse(&format!("meta[name=\"{}\"]", name)).unwrap();
        match document.select(&selector).next() {
            Some(element) => match element.value().attr("content") {
                Some(value) => Some(value.to_owned()),
                None => return None,
            },
            None => return None,
        }
    };
    return Ok(Some(PageData {
        content_id: match get_meta("soudan-content-id") {
            Some(id) => id,
            None => return Ok(None),
        },
    }));
}

#[actix_web::main]
async fn main() -> Result<(), std::io::Error> {
    let arguments = Arguments::parse();
    let mut databases = HashMap::new();
    for domain in arguments.sites.iter() {
        databases.insert(
            domain.to_owned(),
            Mutex::new(Database::new(arguments.testing, domain).unwrap()),
        );
    }
    let port = arguments.port;
    let state = web::Data::new(AppState {
        databases,
        arguments,
    });
    HttpServer::new(move || {
        App::new()
            .service(get_comments)
            .service(post_comment)
            .app_data(state.clone())
            // Issue with CORS on POST requests,
            // keeping permissive for now
            .wrap(
                Cors::permissive(), /* if arguments.testing {
                                        Cors::permissive()
                                    } else {
                                        let mut cors = Cors::default()
                                           .allowed_methods(vec!["GET", "POST"]);
                                        for domain in arguments.sites.iter() {
                                            cors = cors.allowed_origin(domain);
                                        }
                                        cors
                                    } */
            )
    })
    .bind(("127.0.0.1", port))?
    .run()
    .await
}