extern crate clap;
extern crate cookie;
extern crate dotenv;
extern crate json;
#[macro_use]
extern crate lazy_static;
extern crate reqwest;
extern crate zip;

mod catalog;
mod presentation;

use std::env;
use std::collections::HashMap;
use std::io::{self, Read};
use std::path::Path;
use std::sync::Mutex;

use clap::{App, Arg};
use reqwest::{Client, ClientBuilder, Response, RedirectPolicy, RequestBuilder};
use reqwest::header::{Cookie, SetCookie};

use catalog::*;
use presentation::Presentation;

// TODO: Old "Publish To Go" packages get sweeped from the server and you have to request a new one;
//       Implement this
// TODO: sometimes you need to access the video listing at least once using moodle; emulate this

const MAX_RETRIES: u8 = 10;

lazy_static! {
    static ref CLIENT: Client = ClientBuilder::new()
        .expect("Failed to create ClientBuilder!")
        // The login site redirects to itself if no redirect parameter is given
        .redirect(RedirectPolicy::none())
        .build()
        .expect("Failed to create Client!");

    static ref USERNAME: Mutex<String> = Mutex::new(String::new());
    static ref PASSWORD: Mutex<String> = Mutex::new(String::new());
    static ref AUTH: Mutex<String> = Mutex::new(String::new());
}

#[derive(Debug)]
enum DownloadError {
    IoError(io::Error),
    AuthorizationTimeout,
}

fn main() {
    let matches = App::new("TumMediasiteDownloader")
        .author("Boris-Chengbiao Zhou <bobo1239@web.de>")
        .about(
            "Downloads \'catalogs\' from the TUM's Mediasite lecture archive.",
        )
        .arg(
            Arg::with_name("CATALOG_NAME")
                .help(
                    "name of the catalog e.g. from the URL:\n\
                   https://streams.tum.de/Mediasite/Catalog/catalogs/era-2016 -> era-2016\n\
                   special cases (WS16/17; login included): DS, EIDI, ERA, ...",
                )
                .required(true)
                .index(1),
        )
        .arg(
            Arg::with_name("OUTPUT_DIRECTORY")
                .help("where to output the downloaded files")
                .required(true)
                .index(2),
        )
        .arg(
            Arg::with_name("username")
                .short("u")
                .help(
                    "username for login; can be omitted if the user from .env should be used",
                )
                .requires("password")
                .takes_value(true),
        )
        .arg(
            Arg::with_name("password")
                .short("p")
                .help(
                    "password for login; can be omitted if the user from .env should be used",
                )
                .requires("username")
                .takes_value(true),
        )
        .get_matches();

    let catalog_name = matches.value_of("CATALOG_NAME").unwrap();
    let login = if let Some(username) = matches.value_of("username") {
        let password = matches.value_of("password").unwrap();
        Some((username, password))
    } else {
        None
    };

    let catalog_def = resolve_alias(catalog_name).unwrap_or((catalog_name, login));

    let out_dir = Path::new(matches.value_of("OUTPUT_DIRECTORY").unwrap());
    if out_dir.exists() {
        assert!(out_dir.is_dir());
    } else {
        ::std::fs::create_dir_all(out_dir).expect("Failed to create output directory!");
    }

    let (catalog_name, (username, password)) = if let Some((user, pass)) = catalog_def.1 {
        (catalog_def.0, (user.to_string(), pass.to_string()))
    } else {
        (catalog_def.0, get_default_login())
    };

    println!("Preparing to download catalog \"{}\"!", catalog_name);

    USERNAME.lock().unwrap().push_str(&username);
    PASSWORD.lock().unwrap().push_str(&password);
    get_auth();

    download_catalog(catalog_name, out_dir);
}

fn get_default_login() -> (String, String) {
    if dotenv::dotenv().is_err() {
        println!("No .env found!");
    }

    let username = env::var("TUM_USERNAME").expect("Missing TUM_USERNAME environment variable!");
    let password = env::var("TUM_PASSWORD").expect("Missing TUM_PASSWORD environment variable!");
    (username, password)
}

fn get_auth() {
    println!("Logging in!");

    let username = USERNAME.lock().unwrap();
    let password = PASSWORD.lock().unwrap();

    let mut form_data = HashMap::new();
    form_data.insert("UserName", &*username);
    form_data.insert("Password", &*password);

    let res = try_to_get_valid_response(
        |client| {
            let mut request_builder = client.post("https://streams.tum.de/Mediasite/Login").unwrap();
            request_builder.form(
                &form_data,
            ).expect("Failed to serialize form_data!");
            request_builder
        },
        |res| res.headers().get::<SetCookie>().is_some(),
    ).expect(
        "Didn't receive a valid response trying to login! Maybe wrong login data?",
    );
    // FIXME: We're somehow only getting "302 Object moved" instead of the actual response
    //        => We can't determine if the login was successful
    //        (we still get a MediasiteAuth cookie that is useless)
    // let body = read_response_body(&mut res);
    // if body.contains("Unknown username or bad password.") {
    //     panic!("Unknown username or bad password!");
    // }

    let set_cookie: &SetCookie = res.headers().get().unwrap();
    let cookie =
        cookie::Cookie::parse(set_cookie.0[0].to_string()).expect("Failed to parse SetCookie");
    assert_eq!(cookie.name(), "MediasiteAuth");

    let mut auth = AUTH.lock().unwrap();
    auth.clear();
    auth.push_str(cookie.value());
}

fn download_catalog(catalog_name: &str, out_dir: &Path) {
    let catalog_id = get_catalog_id(catalog_name);
    let json = get_json(&catalog_id);
    let presentations = json_to_presentations(&json);
    println!(
        "Starting to download {} presentations!",
        presentations.len()
    );

    for (i, presentation) in presentations.iter().enumerate() {
        println!(
            "\nDownloading {}/{}: {}",
            i + 1,
            presentations.len(),
            presentation.name()
        );
        for _ in 0..MAX_RETRIES {
            match presentation.download(out_dir) {
                Ok(()) => break,
                Err(DownloadError::IoError(e)) => {
                    println!("Error during download: {:?}", e);
                    println!("Retrying!");
                }
                Err(DownloadError::AuthorizationTimeout) => {
                    println!("Authorization is not valid anymore. Refreshing!");
                    get_auth();
                }
            }
        }
    }
}

fn get_catalog_id(name: &str) -> String {
    println!("Fetching catalog id!");

    let url = format!("https://streams.tum.de/Mediasite/Catalog/catalogs/{}", name);
    let mut res = try_to_get_response(|client| {
        let mut request_builder = client.get(&url).unwrap();
        request_builder.header(construct_cookie());
        request_builder
    });
    let body = read_response_body(&mut res);

    let prefix = "CatalogId: '";
    let idx = body.find(prefix).expect(
        "Failed to find CatalogId on the catalog page! Perhaps you got the wrong catalog \
                 name or an invalid login? Maybe you need to open the page in a browser once...",
    );
    let pre_len = prefix.len();
    // Assuming all catalog ids follow this pattern!
    let len = "a6fca0c1-0be4-4e66-83b7-bcdc4eb5e95e".len();

    body[(idx + pre_len)..(idx + pre_len + len)].to_string()
}

fn json_to_presentations(json_str: &str) -> Vec<Presentation> {
    let mut vec = Vec::new();
    let mut json = json::parse(json_str).expect("Failed parsing the json!");
    let mut count = 0;
    for presentation in json["PresentationDetailsList"].members_mut() {
        vec.push(Presentation::from(&*presentation));
        count += 1;
    }
    assert_eq!(count, json["TotalItems"]); // Maybe there are multiple pages
    vec
}

fn get_json(catalog_id: &str) -> String {
    println!("Fetching catalog!");

    let mut data = HashMap::new();
    data.insert("CatalogId", catalog_id);
    data.insert("CurrentFolderId", catalog_id);
    data.insert("ItemsPerPage", "500");

    let mut res = try_to_get_response(|client| {
        let mut request_builder = client
            .post(
                "https://streams.tum.de/Mediasite/Catalog/Data/GetPresentationsForFolder",
            ).unwrap();
        request_builder.header(construct_cookie())
                       .json(&data).expect("Failed to serialize json!");
        request_builder
    });
    read_response_body(&mut res)
}

fn construct_cookie() -> Cookie {
    let mut cookie = Cookie::new();
    cookie.append("MediasiteAuth", (*AUTH.lock().unwrap()).to_string());
    cookie
}

fn try_to_get_response<F>(f: F) -> Response
where
    F: Fn(&Client) -> RequestBuilder,
{
    try_to_get_valid_response(f, |_| true).unwrap()
}

fn try_to_get_valid_response<F1, F2>(f1: F1, f2: F2) -> Result<Response, reqwest::Result<Response>>
where
    F1: Fn(&Client) -> RequestBuilder,
    F2: Fn(&Response) -> bool,
{
    let mut last_response = None;
    for retries in 0..MAX_RETRIES {
        if retries > 0 {
            println!("Retrying request!");
        }
        let response_res = f1(&*CLIENT).send();
        if let Ok(response) = response_res {
            if f2(&response) {
                return Ok(response);
            } else {
                last_response = Some(Ok(response));
            }
        } else {
            last_response = Some(response_res);
        }
    }
    println!(
        "Failed to get valid response! (tried {} times)",
        MAX_RETRIES
    );
    Err(last_response.unwrap())
}

fn read_response_body(response: &mut Response) -> String {
    let mut string = String::new();
    response.read_to_string(&mut string).expect(
        "Failed to read body",
    );
    string
}