use futures_util::TryStreamExt;
use time::OffsetDateTime;
use sqlx::{postgres::PgPool, Row};
use std::cmp::max;
use std::path::{Path, PathBuf};
use time::ext::NumericalStdDuration;
use tokio::fs;
use tokio::sync::mpsc::Receiver;
use tokio::time::timeout;

pub(crate) async fn delete_old_files(mut receiver: Receiver<()>, db: PgPool, files_dir: PathBuf) {
    loop {
        wait_for_file_expiry(&mut receiver, &db).await;

        let now = OffsetDateTime::now_utc();
        let mut rows = sqlx::query("SELECT file_id FROM files WHERE files.valid_till < $1")
            .bind(now)
            .fetch(&db);
        while let Some(row) = rows.try_next().await.expect("could not load expired files") {
            let file_id: String = row.try_get("file_id").expect("we selected this column");
            delete_content(&file_id, &files_dir)
                .await
                .expect("could not delete file");
        }

        sqlx::query("DELETE FROM files WHERE valid_till < $1")
            .bind(now)
            .execute(&db)
            .await
            .expect("could not delete expired files from database");
    }
}

pub(crate) async fn delete_by_id(
    db: &PgPool,
    file_id: &str,
    files_dir: &Path,
) -> Result<(), sqlx::Error> {
    delete_content(file_id, files_dir).await?;
    sqlx::query("DELETE FROM files WHERE file_id = $1")
        .bind(file_id)
        .execute(db)
        .await?;
    Ok(())
}

async fn delete_content(file_id: &str, files_dir: &Path) -> Result<(), std::io::Error> {
    let path = files_dir.join(file_id);
    if fs::remove_file(&path).await.is_ok() {
        log::info!("delete file {}", file_id);
    }
    Ok(())
}

async fn wait_for_file_expiry(receiver: &mut Receiver<()>, db: &PgPool) {
    let valid_till: (Option<OffsetDateTime>,) =
        sqlx::query_as("SELECT MIN(valid_till) as min from files")
            .fetch_one(db)
            .await
            .expect("could not fetch expiring files from database");
    let next_timeout: std::time::Duration = match valid_till.0 {
        Some(valid_till) => (max(
            0,
            valid_till.unix_timestamp() - OffsetDateTime::now_utc().unix_timestamp(),
        ) as u64)
            .std_seconds(),
        None => 1_u64.std_days(),
    };
    let _ = timeout(next_timeout, receiver.recv()).await;
}