use anyhow::{anyhow, Result};
use rand::{thread_rng, Rng};
use reqwest::{header::HeaderMap, Client};
use std::{path::Path, time::Duration};
use tokio::{fs::File, io::AsyncReadExt, io::AsyncWriteExt, time::interval};
use url::Url;

mod description;
mod name;

const USER_AGENT: &str = "warriors-cats";
const TOKEN_PATH: &str = "/oauth/token";
const STATUS_URL: &str = "/api/v1/statuses";

#[derive(serde::Deserialize)]
struct Config {
    timing: Timing,
    mastodon: Mastodon,
}

#[derive(serde::Deserialize)]
struct Mastodon {
    server: Url,
    client_id: String,
    client_secret: String,
    authorization_code: String,
}

#[derive(serde::Deserialize)]
struct Timing {
    duration: u32,
}

struct State {
    server: Url,
    client: Client,
    name: name::Config,
    description: description::Config,
}

#[derive(serde::Serialize)]
struct OauthParams {
    client_id: String,
    client_secret: String,
    code: String,
    redirect_uri: &'static str,
    grant_type: &'static str,
    scope: &'static str,
}

#[derive(serde::Deserialize, serde::Serialize)]
struct Token {
    access_token: String,
}

#[derive(serde::Serialize)]
struct Status {
    status: String,
    visibility: &'static str,
}

impl Mastodon {
    async fn authenticate(self) -> Result<Token> {
        let server = self.server;
        let mut oauth_url = server.clone();
        oauth_url.set_path(TOKEN_PATH);
        let client = Client::new();

        let res = client
            .post(oauth_url.as_str())
            .header("User-Agent", USER_AGENT)
            .form(&OauthParams {
                client_id: self.client_id,
                client_secret: self.client_secret,
                code: self.authorization_code,
                redirect_uri: "urn:ietf:wg:oauth:2.0:oob",
                grant_type: "authorization_code",
                scope: "read write",
            })
            .send()
            .await?;

        if !res.status().is_success() {
            return Err(anyhow!(
                "Failed to fetch access token:\n{}",
                res.text().await?
            ));
        }

        let token: Token = res.json().await?;
        Ok(token)
    }
}

async fn read_token(path: impl AsRef<Path>) -> Result<Token> {
    let mut file = File::open(path).await?;
    let mut contents = String::new();
    file.read_to_string(&mut contents).await?;

    let token: Token = toml::from_str(&contents)?;
    Ok(token)
}

async fn write_token(path: impl AsRef<Path>, token: &Token) -> Result<()> {
    let token_bytes = toml::to_string(token)?;
    let mut file = File::create(path).await?;
    file.write_all(token_bytes.as_bytes()).await?;
    Ok(())
}

impl Config {
    async fn open(path: impl AsRef<Path>) -> Result<Self> {
        let mut file = File::open(path).await?;
        let mut contents = String::new();
        file.read_to_string(&mut contents).await?;

        let config: Config = toml::from_str(&contents)?;
        Ok(config)
    }

    async fn into_state(
        self,
        token_path: impl AsRef<Path>,
        name: name::Config,
        description: description::Config,
    ) -> Result<State> {
        let Config {
            timing: _,
            mastodon,
        } = self;

        let server = mastodon.server.clone();

        let token = match read_token(token_path.as_ref()).await {
            Ok(token) => token,
            _ => {
                let token = mastodon.authenticate().await?;
                write_token(token_path.as_ref(), &token).await?;
                token
            }
        };

        let mut headers = HeaderMap::new();
        headers.insert(
            "Authorization",
            format!("Bearer {}", token.access_token).parse()?,
        );

        let client = Client::builder()
            .user_agent(USER_AGENT)
            .default_headers(headers)
            .build()?;

        Ok(State {
            server,
            client,
            name,
            description,
        })
    }
}

impl State {
    async fn post(&self, rng: &mut impl Rng) -> Result<()> {
        let mut url = self.server.clone();
        url.set_path(STATUS_URL);

        let res = self
            .client
            .post(url.as_str())
            .form(&Status {
                status: self.gen(rng),
                visibility: "unlisted",
            })
            .send()
            .await?;

        if !res.status().is_success() {
            return Err(anyhow!("Failed to post status:\n{}", res.text().await?));
        }

        Ok(())
    }

    fn gen(&self, rng: &mut impl Rng) -> String {
        let name = self.name.gen(rng);
        let description = self.description.gen(rng);

        format!("{} - {}", name, description)
    }
}

#[tokio::main]
async fn main() -> Result<()> {
    let config = Config::open("Config.toml").await?;
    let name = name::config("Name.json").await?;
    let description = description::config("Description.json").await?;

    let duration = Duration::from_secs(60) * config.timing.duration;
    let mut ticker = interval(duration);

    let state = config.into_state("Token.toml", name, description).await?;

    let mut rng = thread_rng();
    loop {
        ticker.tick().await;
        state.post(&mut rng).await?;
    }
}