use std::{collections::HashMap, sync::Arc};
use serde::Deserialize;
use tokio::sync::Mutex;
use tokio::sync::oneshot::{channel, Sender, Receiver};
use uuid::Uuid;

use crate::OAUTH_CLIENT_NAME;
#[derive(Clone)]
pub struct OAuthController (Arc<Mutex<OAuthInternal>>);

type ServerDomain = String;
type AccountIdentifier = String;
type StateCode = Uuid;

struct OAuthInternal {
    servers: HashMap<ServerDomain, Server>,
    open_callbacks: HashMap<StateCode, Callback>
}

#[derive(Clone)]
struct Server {
    client_name: String,
    client_id: String,
    client_secret: String,
    accounts: Vec<Account>,
}

struct Callback {
    server: ServerDomain,
    pkce_verifier: String,
    pkce_challenge: String,
    code_channel: (Option<Sender<String>>, Option<Receiver<String>>),
}

#[derive(Clone)]
struct Account {
    username: String,
    auth_session: AuthSession,
}

#[derive(Clone)]
pub struct AuthSession {
    pub api_token: String,
    refresh_token: Option<String>,
}

pub struct AddServerResult {
    pub auth_url: String,
    pub auth_state: StateCode,
}

impl OAuthController {
    pub fn new() -> Self {
        Self(Arc::new(Mutex::new(OAuthInternal {
            servers: HashMap::new(),
            open_callbacks: HashMap::new(),
        })))
    }

    pub async fn add_server(&self, instance_domain: &str) -> Result<AddServerResult, String> {
        let registration_endpoint = format!("https://{instance_domain}/api/v1/apps");
        let http_client = reqwest::Client::builder().user_agent("Foxfleet v0.0.1").build().expect("Could not construct client");

        #[derive(Deserialize)]
        struct RegistrationResponse {
            id: String,
            name: String,
            client_id: String,
            client_secret: String,
        }

        let registration_response : RegistrationResponse = http_client.post(registration_endpoint)
            .json(&HashMap::from([
                ("client_name", OAUTH_CLIENT_NAME),
                ("redirect_uris", "dev.tempest.foxfleet://oauth-response"),
                ("scopes", "read write"),
            ])).send().await.expect("Could not send client registration")
            .json().await.expect("Could not parse client registration response");

        let server = Server {
            client_name: registration_response.name,
            client_id: registration_response.client_id.clone(),
            client_secret: registration_response.client_secret,
            accounts: Vec::new(),
        };

        {self.0.lock().await.servers.insert(instance_domain.to_string(), server)};

        let (sender, receiver) = channel::<String>();

        // TODO: PKCE params for real
        let auth_state = Uuid::new_v4();
        let auth_callback = Callback {
            server: instance_domain.to_string(),
            pkce_verifier: String::new(),
            pkce_challenge: String::new(),
            code_channel: (Some(sender), Some(receiver)),
        };

        let client_id = registration_response.client_id;

        {self.0.lock().await.open_callbacks.insert(auth_state.clone(), auth_callback)};

        let auth_url = format!("https://{instance_domain}/oauth/authorize?client_id={client_id}&redirect_uri=dev.tempest.foxfleet://oauth-response&response_type=code&scope=read+write&state={auth_state}");

        return Ok(AddServerResult {
            auth_url,
            auth_state,
        })
    }

    pub fn resolve_code(&self, state: StateCode, auth_code: String) {
        let runtime = tokio::runtime::Handle::current();
        let inner_self = self.0.clone();
        let state = state.clone();

        runtime.spawn(async move {
            if let Some(sender) = inner_self.lock().await.open_callbacks.get_mut(&state).map(|callback| callback.code_channel.0.take() ).flatten() {
                let _ = sender.send(auth_code);
            };
        });
    }

    pub async fn finish_signin(&self, state: StateCode) -> Result<(String, String), String> {
        let auth_code = self.await_auth_code(&state).await?;
        let auth_session = self.exchange_api_token(&state, &auth_code).await?;
        let username = self.resolve_account(&state, &auth_session).await?;

        let account = Account {
            username: username.clone(),
            auth_session
        };

        let mut inner_state = self.0.lock().await;

        if let Some(callback) = inner_state.open_callbacks.remove(&state) {
            if let Some (server) = inner_state.servers.get_mut(&callback.server) {
                server.accounts.push(account);
                return Ok((callback.server.clone(), username))
            } else {
                Err("Unknown server URL".to_string())
            }
        } else {
            Err("Unknown state".to_string())
        }
    }

    async fn await_auth_code(&self, state: &StateCode) -> Result<String, String> {
        let maybe_receiver = {self.0.lock().await.open_callbacks.get_mut(&state).map(|callback| callback.code_channel.1.take() ).flatten()};
        if let Some(receiver) = maybe_receiver {
            if let Ok(auth_code) = receiver.await {
                Ok(auth_code)
            } else {
                Err("Error receiving code from channel".to_string())
            }
        } else {
            Err("Channel already awaited".to_string())
        }
    }

    // TODO: Send PKCE stuff
    async fn exchange_api_token(&self, state: &StateCode, auth_code: &String) -> Result<AuthSession, String> {
        let maybe_server = {
            let inner_state = self.0.lock().await;
            if let Some(server_domain) = inner_state.open_callbacks.get(&state).map(|callback| callback.server.clone()) {
                if let Some(server) = inner_state.servers.get(&server_domain) {
                    Some((server_domain, server.clone()))
                } else {
                    None
                }
            } else {
                None
            }
        };

        if maybe_server.is_none() {
            return Err("Unknown auth state".to_string());
        }

        let (server_domain, server) = maybe_server.unwrap();

        #[derive(Deserialize)]
        struct TokenResponse {
            access_token: String,
            created_at: u32,
            scope: String,
            token_type: String,
        }

        let http_client = reqwest::Client::builder().user_agent("Foxfleet v0.0.1").build().expect("Could not construct client");
        let token_endpoint = format!("https://{server_domain}/oauth/token");
        let token_response : TokenResponse = http_client.post(token_endpoint)
            .json(&HashMap::from([
                ("redirect_uri", "dev.tempest.foxfleet://oauth-response"),
                ("client_id", server.client_id.as_str()),
                ("client_secret", server.client_secret.as_str()),
                ("grant_type", "authorization_code"),
                ("code", auth_code.as_str()),
            ])).send().await.expect("Could not get API token")
            .json().await.expect("Could not parse client registration response");

        Ok(AuthSession {
            api_token: token_response.access_token,
            refresh_token: None,
        })
    }

    async fn resolve_account(&self, state: &StateCode, auth_session: &AuthSession) -> Result<String, String> {
        let instance_url = { self.0.lock().await.open_callbacks.get(&state).map(|callback| callback.server.clone()) };

        if let Some(instance_url) = instance_url {
            #[derive(Deserialize)]
            struct VerifyResponse {
                acct: String,
            }

            let http_client = reqwest::Client::builder().user_agent("Foxfleet v0.0.1").build().expect("Could not construct client");
            let verify_response : VerifyResponse = http_client.get(format!("https://{instance_url}/api/v1/accounts/verify_credentials"))
                .bearer_auth(auth_session.api_token.clone())
                .send().await.expect("Could not look up account information")
                .json().await.expect("Could not parse account information");

            Ok(verify_response.acct)
        } else {
            Err("No instance URL".to_string())
        }
    }

    pub async fn get_api_token(&self, server_domain: String, username: String) -> Result<String, String> {
        let api_token_maybe = { self.0.lock().await.servers.get(&server_domain).map(|server| {
            server.accounts.iter().find(|account| account.username == username).map(|account| account.auth_session.api_token.clone())
        }).flatten()};

        match api_token_maybe {
            Some(api_token) => Ok(api_token),
            None => Err("Could not look up {server_domain} / {username}".to_string()),
        }
    }
}