use std::{
    env,
    error::Error,
    net::SocketAddr,
    path::{Path, PathBuf},
};

use axum::{
    Router,
    routing::{get, post},
};
use tower_http::services::{ServeDir, ServeFile};

use crate::{api, storage::Storage};

const DEFAULT_BIND_ADDR: &str = "127.0.0.1:3000";
const STATIC_DIR_ENV: &str = "UPL_STATIC_DIR";
const DATA_DIR_ENV: &str = "UPL_DATA_DIR";
const BIND_ENV: &str = "UPL_BIND";

#[derive(Clone, Debug)]
pub struct AppConfig {
    pub bind_addr: SocketAddr,
    pub static_dir: PathBuf,
    pub data_dir: PathBuf,
}

#[derive(Clone, Debug)]
pub struct AppState {
    pub storage: Storage,
}

impl AppConfig {
    /// Loads bind and static directory settings from environment variables.
    ///
    /// # Errors
    ///
    /// Returns an error when `UPL_BIND` is set but is not a valid socket address.
    pub fn from_env() -> Result<Self, Box<dyn Error>> {
        let bind_addr = env::var(BIND_ENV)
            .unwrap_or_else(|_| DEFAULT_BIND_ADDR.to_owned())
            .parse()?;
        let static_dir = env::var_os(STATIC_DIR_ENV).map_or_else(default_static_dir, PathBuf::from);
        let data_dir = env::var_os(DATA_DIR_ENV).map_or_else(default_data_dir, PathBuf::from);

        Ok(Self {
            bind_addr,
            static_dir,
            data_dir,
        })
    }

    #[must_use]
    pub fn new(
        bind_addr: SocketAddr,
        static_dir: impl Into<PathBuf>,
        data_dir: impl Into<PathBuf>,
    ) -> Self {
        Self {
            bind_addr,
            static_dir: static_dir.into(),
            data_dir: data_dir.into(),
        }
    }
}

pub fn build_router(config: &AppConfig) -> Router {
    let state = AppState {
        storage: Storage::new(&config.data_dir),
    };

    Router::new()
        .route("/healthz", get(healthz))
        .route("/api/uploads", post(api::create_upload))
        .fallback_service(static_service(&config.static_dir))
        .with_state(state)
}

async fn healthz() -> &'static str {
    "ok"
}

fn static_service(static_dir: &Path) -> ServeDir<ServeFile> {
    ServeDir::new(static_dir).fallback(ServeFile::new(static_dir.join("index.html")))
}

fn default_static_dir() -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("static")
}

fn default_data_dir() -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("data")
}