use axum::{extract::{Query, State}, http::{HeaderMap, HeaderValue, StatusCode}, response::{Html, IntoResponse}, Extension, Form};
use chrono::{SecondsFormat, Utc};
use fully_pub::fully_pub;
use log::{debug, error, info};
use minijinja::context;
use serde::{Deserialize, Serialize};
use url::Url;
use uuid::Uuid;

use kernel::models::{authorization::Authorization, config::AppAuthorizeFlow};
use utils::get_random_alphanumerical;
use crate::{
    renderer::TemplateRenderer, services::oauth2::{parse_scope, verify_redirect_uri}, token_claims::UserTokenClaims, AppState
};

#[derive(Debug, Serialize, Deserialize)]
#[fully_pub]
/// query params described in [RFC6749 section 4.1.1](https://datatracker.ietf.org/doc/html/rfc6749#section-4.1.1)
struct AuthorizationParams {
    response_type: String,
    client_id: String,
    scope: String,
    redirect_uri: String,
    /// An opaque value used by the client to maintain state between the request and callback
    state: String,
    nonce: Option<String>
}

fn redirect_to_client(
    authorization_code: &str,
    authorization_params: &AuthorizationParams
) -> impl IntoResponse {
    let target_url = format!("{}?code={}&state={}",
        authorization_params.redirect_uri,
        authorization_code,
        authorization_params.state
    );
    debug!("Redirecting to {}", target_url);

    let mut headers = HeaderMap::new();
    headers.insert("Location", HeaderValue::from_str(&target_url).unwrap());
    (
        StatusCode::FOUND,
        headers,
        Html("Redirecting to client…")
    ).into_response()
}

/// The authorization endpoint is used to interact with the resource owner and obtain an authorization grant.
/// https://datatracker.ietf.org/doc/html/rfc6749#section-3.1
pub async fn authorize_form(
    State(app_state): State<AppState>,
    Extension(token_claims): Extension<UserTokenClaims>,
    Extension(renderer): Extension<TemplateRenderer>,
    query_params: Query<AuthorizationParams>
) -> impl IntoResponse {
    let Query(authorization_params) = query_params;
    dbg!(&authorization_params);

    // 1. Verify the app details
    let app = match app_state.config.applications
        .iter()
        .find(|a| a.client_id == authorization_params.client_id) {
        Some(app) => app,
        None => {
            return (
                StatusCode::BAD_REQUEST,
                Html("Invalid client_id query params, app not found.")
            ).into_response();
        }
    };

    // 1.1. Verify that the app redirect_uri is authorized
    if !verify_redirect_uri(app, &authorization_params.redirect_uri) {
        return (
            StatusCode::BAD_REQUEST,
            Html("Unauthorized redirect_uri.")
        ).into_response();
    }
    // 1.3. Parse and validate redirect_uri.
    // Note: for now, we only support HTTP(s) redirect URLs.
    let parsed_redirect_uri: Url = match Url::parse(&authorization_params.redirect_uri) {
        Ok(url) => url,
        Err(_) => {
            return (
                StatusCode::BAD_REQUEST,
                Html("Invalid redirect URL. Could not parse as HTTP(S) URL.")
            ).into_response();
        }
    };
    // 1.4. Parse and validate scopes
    let scopes = match parse_scope(&authorization_params.scope) {
        Ok(v) => v,
        Err(_err) => {
            return (
                StatusCode::BAD_REQUEST,
                Html("Invalid scopes. Scopes must be space-delimited and snake_case.")
            ).into_response();
        }
    };

    // 2. Check if the app is already authorized
    let authorizations_res = sqlx::query_as::<_, Authorization>(
        "SELECT * FROM authorizations WHERE user_id = $1 AND client_id = $2 AND scopes = $3"
    )
        .bind(&token_claims.sub)
        .bind(&authorization_params.client_id)
        .bind(sqlx::types::Json(&scopes))
        .fetch_one(&app_state.db.0)
        .await;

    match authorizations_res {
        Ok(existing_authorization) => {
            info!("Reusing existing authorization: {}", &existing_authorization.id);

            // Create new auth code
            let authorization_code = get_random_alphanumerical(32);
            // Update last used timestamp for this authorization
            let _result = sqlx::query("UPDATE authorizations SET code = $2, nonce = $3, last_used_at = $4 WHERE id = $1")
                .bind(existing_authorization.id)
                .bind(authorization_code.clone())
                .bind(authorization_params.nonce.clone())
                .bind(Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true))
                .execute(&app_state.db.0)
                .await.unwrap();

            // Authorization already given, just redirect to the app
            return redirect_to_client(
                &authorization_code,
                &authorization_params
            ).into_response()
        },
        Err(sqlx::Error::RowNotFound) => {
            debug!("Authorization not found.");
        },
        Err(err) => {
            error!("Cannot get existing authorization. {}", err);
            return (
                StatusCode::INTERNAL_SERVER_ERROR,
                Html("Internal server error: Failed to verify conditions.")
            ).into_response();
        }
    }

    // 3. Check for implicit/explicit flow
    if app.authorize_flow == AppAuthorizeFlow::Implicit {
        debug!("Performing Implicit authorization flow.");
        // Authorization already given, just redirect to the app
        return perform_authorize(
            State(app_state),
            Extension(token_claims),
            Form(authorization_params)
        ).await.into_response()
    }

    // 4. Show form that POST to authorize
    debug!("Performing explicit authorization flow.");
    renderer
        .render(
            "pages/authorize",
            context!(
                app => app,
                authorization_params => authorization_params,
                redirect_uri_host => parsed_redirect_uri.host_str()
            )
        )
        .into_response()
}


pub async fn perform_authorize(
    State(app_state): State<AppState>,
    Extension(token_claims): Extension<UserTokenClaims>,
    Form(authorize_form): Form<AuthorizationParams>
) -> impl IntoResponse {
    dbg!(&authorize_form);
    // 1. Get the app details
    let app = match app_state.config.applications
        .iter()
        .find(|a| a.client_id == authorize_form.client_id) {
        Some(app) => app,
        None => {
            return (
                StatusCode::BAD_REQUEST,
                Html("Invalid client_id, app not found.")
            ).into_response();
        }
    };
    // 1.2. Parse and validate scope to use in DB
    let scopes = match parse_scope(&authorize_form.scope) {
        Ok(v) => v,
        Err(_err) => {
            return (
                StatusCode::BAD_REQUEST,
                Html("Invalid scopes.")
            ).into_response();
        }
    };
    // 2. Create an authorization code
    let authorization_code = get_random_alphanumerical(32);

    let authorization = Authorization {
        id: Uuid::new_v4().to_string(),
        user_id: token_claims.sub,
        client_id: app.client_id.clone(),
        scopes: sqlx::types::Json(scopes),
        code: authorization_code.clone(),
        nonce: authorize_form.nonce.clone(),
        last_used_at: Some(Utc::now()),
        created_at: Utc::now(),
    };

    // 3. Save authorization in DB with state
    let res = sqlx::query("
        INSERT INTO authorizations
            (id, user_id, client_id, scopes, code, nonce, last_used_at, created_at)
            VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
        ")
        .bind(authorization.id.clone())
        .bind(authorization.user_id)
        .bind(authorization.client_id)
        .bind(authorization.scopes)
        .bind(authorization.code)
        .bind(authorization.nonce)
        .bind(authorization.last_used_at.map(|x| x.to_rfc3339_opts(SecondsFormat::Millis, true)))
        .bind(authorization.created_at.to_rfc3339_opts(SecondsFormat::Millis, true))
        .execute(&app_state.db.0)
        .await;
    if let Err(err) = res {
        error!("Failed to save authorization in DB. {}", err);
        return (StatusCode::INTERNAL_SERVER_ERROR, Html("Internal server error: Failed to process authorization form.")).into_response();
    }
    info!("Created authorization {}", &authorization.id);

    // 4. Redirect to the app with the authorization code and state
    redirect_to_client(&authorization_code, &authorize_form).into_response()
}