/*
 ** Copyright (C) 2021 KunoiSayami
 **
 ** This file is part of cgit-simple-authentication and is released under
 ** the AGPL v3 License: https://www.gnu.org/licenses/agpl-3.0.txt
 **
 ** This program 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
 ** 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 <https://www.gnu.org/licenses/>.
 */

mod database;
mod datastructures;

use anyhow::Result;
use std::io::{stdin, Read};
use std::env;
use clap::{Arg, App, SubCommand, ArgMatches};
use rand::Rng;
use serde::{Serialize};
use handlebars::Handlebars;
use sqlx::Connection;
use crate::datastructures::{Config, FormData};
use redis::AsyncCommands;
use std::result::Result::Ok;

const COOKIE_LENGTH: usize = 45;


fn get_current_timestamp() -> u64 {
    let start = std::time::SystemTime::now();
    let since_the_epoch = start
        .duration_since(std::time::UNIX_EPOCH)
        .expect("Time went backwards");
    since_the_epoch.as_secs()
}

fn rand_str(len: usize) -> String {
    const CHARSET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
                        abcdefghijklmnopqrstuvwxyz\
                        0123456789";
    let mut rng = rand::thread_rng();

    let password: String = (0..len)
        .map(|_| {
            let idx = rng.gen_range(0, CHARSET.len());
            CHARSET[idx] as char
        })
        .collect();

    password
}

fn rand_int() -> i32 {
    let mut rng = rand::thread_rng();
    rng.gen()
}


#[derive(Serialize)]
struct Meta<'a> {
    action: &'a str,
    redirect: &'a str,
}


// Processing the `authenticate-basic` called by cgit.
fn cmd_authenticate_basic(
    _matches: &ArgMatches,
    _cfg: Config,
) -> Result<()> {
    unimplemented!()
}

// Processing the `authenticate-cookie` called by cgit.
async fn cmd_authenticate_cookie(
    matches: &ArgMatches<'_>,
    cfg: Config,
) -> Result<bool> {
    let cookies =  matches.value_of("http-cookie").unwrap_or("");

    if cookies.is_empty() {
        return Ok(false)
    }

    let redis_conn = redis::Client::open("redis://127.0.0.1/")?;
    let mut conn = redis_conn.get_async_connection().await?;


    for cookie in cookies.split(';').map(|x| x.trim()) {
        let (key, value) = cookie.split_once('=').unwrap();
        if key.eq("cgit_auth") {
            let value = base64::decode(value).unwrap_or_default();
            let value = std::str::from_utf8(&value).unwrap_or("");

            if !value.contains(';') {
                break
            }

            let (key, value) = value.split_once(';').unwrap();//.unwrap_or(("0_0", "0"));

            let (timestamp, _) = key.split_once("_").unwrap_or(("0", ""));

            if get_current_timestamp() - timestamp.parse::<u64>().unwrap_or(0) > cfg.cookie_ttl {
                break
            }

            if let Ok(r) = conn.get::<_, String>(format!("cgit_auth_{}", key)).await {
                if r == value {
                    return Ok(true)
                }
            }
            break
        }
    }

    Ok(false)
}


async fn cmd_init(cfg: Config) -> Result<()> {
    log::trace!("{}", cfg.get_database_location());
    let loc = std::path::Path::new(cfg.get_database_location());
    if ! loc.exists() {
        std::fs::File::create(loc)?;
    }

    let mut conn = sqlx::SqliteConnection::connect(cfg.get_database_location()).await?;

    let rows = sqlx::query(r#"SELECT name FROM sqlite_master WHERE type='table' AND name=?"#)
        .bind("auth_meta")
        .fetch_all(&mut conn)
        .await?;

    if rows.is_empty() {
        sqlx::query(database::current::CREATE_TABLES)
            .execute(&mut conn)
            .await?;
        log::info!("Initialize the database successfully");
    }


    Ok(())
}

async fn verify_login(cfg: &Config, data: &FormData) -> Result<bool> {
    let database_file_name = std::path::Path::new(datastructures::CACHE_DIR)
        .join(std::path::Path::new(cfg.get_database_location()).file_name().unwrap());
    std::fs::copy(cfg.get_database_location(), database_file_name.clone())?;
    let mut conn = sqlx::SqliteConnection::connect(database_file_name.to_str().unwrap()).await?;
    let password_sha = data.get_password_sha256()?;
    log::debug!("password: {}", password_sha);
    let ret = sqlx::query(r#"SELECT 1 FROM "accounts" WHERE "user" = ? AND "password" = ? "#)
        .bind(data.get_user())
        .bind(password_sha)
        .fetch_all(&mut conn)
        .await?;
    Ok(!ret.is_empty())
}


// Processing the `authenticate-post` called by cgit.
async fn cmd_authenticate_post(
    matches: &ArgMatches<'_>,
    cfg: Config,
) -> Result<()> {
    // Read stdin from upstream.
    let mut buffer = String::new();
    stdin().read_to_string(&mut buffer)?;
    log::debug!("{}", buffer);
    let data = datastructures::FormData::from(buffer);
    // Parsing user posted form.

    let ret = verify_login(&cfg, &data).await;

    if let Err(ref e) = ret {
        log::error!("{:?}", e)
    }

    if ret.unwrap() {
        let key = format!("{}_{}", get_current_timestamp(), rand_int());
        let value = rand_str(COOKIE_LENGTH);

        let redis_conn = redis::Client::open("redis://127.0.0.1/")?;
        let mut conn = redis_conn.get_async_connection().await?;
        conn.set_ex::<_, _, String>(format!("cgit_auth_{}", key), &value, cfg.cookie_ttl as usize).await?;

        let cookie_value = base64::encode(format!("{};{}", key, value));

        let is_secure = matches
            .value_of("https")
            .map_or(false, | x | matches!(x, "yes" | "on" | "1"));
        let domain = matches.value_of("http-host").unwrap_or("*");
        let location = matches
            .value_of("current-url")
            .unwrap_or("/")
            .split('?')
            .next()
            .unwrap();
        let cookie_suffix = if is_secure { "; secure" } else { "" };
        println!("Status: 302 Found");
        println!("Cache-Control: no-cache, no-store");
        println!("Location: {}", location);
        println!(
            "Set-Cookie: cgit_auth={}; Domain={}; Max-Age={}; HttpOnly{}",
            cookie_value, domain, cfg.cookie_ttl, cookie_suffix
        );
    } else {
        println!("Status: 403 Forbidden");
        println!("Cache-Control: no-cache, no-store");
    }
    println!();


    Ok(())
}


// Processing the `body` called by cgit.
async fn cmd_body(matches: &ArgMatches<'_>, _cfg: Config) {
    let source = include_str!("authentication_page.html");
    let handlebars = Handlebars::new();
    let meta = Meta {
        action: matches.value_of("login-url").unwrap_or(""),
        redirect: matches.value_of("current-url").unwrap_or(""),
    };
    handlebars
        .render_template_to_write(source, &meta, std::io::stdout())
        .unwrap();
}


async fn cmd_add_user(matches: &ArgMatches<'_>, cfg: Config) -> Result<()>{
    let user = matches.value_of("user").unwrap_or("");
    let passwd = matches.value_of("password").unwrap_or("").to_string();
    if user.is_empty() || passwd.is_empty() {
        return Err(anyhow::Error::msg("Invalid user or password"))
    }
    let mut conn = sqlx::SqliteConnection::connect(cfg.get_database_location()).await?;

    let items = sqlx::query(r#"SELECT 1 FROM "accounts" WHERE "user" = ? "#)
        .bind(user)
        .fetch_all(&mut conn)
        .await?;

    if ! items.is_empty() {
        return Err(anyhow::Error::msg("User already exists!"))
    }

    sqlx::query(r#"INSERT INTO "accounts" ("user", "password") VALUES (?, ?) "#)
        .bind(user)
        .bind(FormData::get_string_sha256_value(&passwd)?)
        .execute(&mut conn)
        .await?;
    println!("Insert {} to database", user);
    Ok(())
}

async fn async_main(arg_matches: ArgMatches<'_>, cfg: Config) -> Result<i32>{
    match arg_matches.subcommand() {
        ("authenticate-cookie", Some(matches)) => {
            if let Ok(should_pass) = cmd_authenticate_cookie(matches, cfg).await {
                if should_pass {
                    return Ok(1)
                }
            }
        }
        ("authenticate-post", Some(matches)) => {
            cmd_authenticate_post(matches, cfg).await?;
        }
        ("body", Some(matches)) => {
            cmd_body(matches, cfg).await;
        }
        ("init", Some(_matches)) => {
            cmd_init(cfg).await?;
        }
        ("adduser", Some(matches)) => {
            cmd_add_user(matches, cfg).await?;
        }
        _ => {}
    }
    log::debug!("exit");
    Ok(0)
}

fn main() -> Result<()>{

    simple_logging::log_to_file("/tmp/auth.log", log::LevelFilter::Debug)?;

    log::debug!("{}", env::args().collect::<Vec<String>>()
        .join(" "));

    // Sub-arguments for each command, see cgi defines.
    let sub_args = &[
        Arg::with_name("http-cookie").required(true),
        Arg::with_name("request-method").required(true),
        Arg::with_name("query-string").required(true),
        Arg::with_name("http-referer").required(true),
        Arg::with_name("path-info").required(true),
        Arg::with_name("http-host").required(true),
        Arg::with_name("https").required(true),
        Arg::with_name("repo").required(true),
        Arg::with_name("page").required(true),
        Arg::with_name("current-url").required(true),
        Arg::with_name("login-url").required(true),
    ];

    let matches = App::new("Simple Authentication Filter for cgit")
        .version(env!("CARGO_PKG_VERSION"))
        .subcommand(
            SubCommand::with_name("authenticate-cookie")
                .about("Processing authenticated cookie")
                .args(sub_args),
        )
        .subcommand(
            SubCommand::with_name("authenticate-post")
                .about("Processing posted username and password")
                .args(sub_args),
        )
        .subcommand(
            SubCommand::with_name("body")
                .about("Return the login form")
                .args(sub_args),
        )
        .subcommand(SubCommand::with_name("init").about("Init sqlite database"))
        .subcommand(
            SubCommand::with_name("adduser")
                .about("Add user to database")
                .arg(Arg::with_name("user").required(true))
                .arg(Arg::with_name("password").required(true)),

        )
        .get_matches();

    // Load filter configurations
    let cfg = Config::new();

    let ret = tokio::runtime::Builder::new_current_thread()
        .enable_all()
        .build()
        .unwrap()
        .block_on(async_main(matches, cfg))?;
    if ret == 1 {
        std::process::exit(1);
    }

    Ok(())
}