use sea_orm::{
    error::DbErr, prelude::*, sea_query::SimpleExpr, FromQueryResult, ItemsAndPagesNumber, Order,
    QueryOrder,
};
use serde::{Deserialize, Serialize};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PaginatedResponse<M> {
    pub count: u64,
    pub num_pages: u64,
    pub list: Vec<M>,
}

pub async fn paginate<E, M, C>(
    db: &DatabaseConnection,
    page: Option<u64>,
    size: Option<u64>,
    column: Option<C>,
    order: Option<Order>,
) -> Result<PaginatedResponse<M>, DbErr>
where
    E: EntityTrait,
    M: Send + Sync + FromQueryResult,
    C: ColumnTrait,
{
    let s = size.unwrap_or(20).min(50);
    let selector;
    if let (Some(col), Some(ord)) = (column, order) {
        selector = E::find().order_by(col, ord);
    } else {
        selector = E::find();
    }

    let pages = selector.into_model().paginate(db, s);
    let ItemsAndPagesNumber {
        number_of_items: count,
        number_of_pages: num_pages,
    } = pages.num_items_and_pages().await?;

    let p = page.unwrap_or(0).min(num_pages);

    let list = pages.fetch_page(p).await?;

    let res = PaginatedResponse {
        count,
        num_pages,
        list,
    };

    Ok(res)
}

/// Use for 1-1 relationships, retrieves the entity and the single related record
pub async fn paginate_also_related<E, R, T, K, C>(
    db: &DatabaseConnection,
    page: Option<u64>,
    size: Option<u64>,
    column: Option<C>,
    order: Option<Order>,
    filters: Option<Vec<SimpleExpr>>,
) -> Result<PaginatedResponse<(T, Option<K>)>, DbErr>
where
    E: EntityTrait + Related<R>,
    R: EntityTrait,
    T: Sync + Send + FromQueryResult,
    K: Sync + Send + FromQueryResult,
    C: ColumnTrait,
{
    let s = size.unwrap_or(20).min(50);

    let mut selector;
    if let (Some(col), Some(ord)) = (column, order) {
        selector = E::find()
            .find_also_related::<R>(R::default())
            .order_by(col, ord)
    } else {
        selector = E::find().find_also_related::<R>(R::default());
    }

    if let Some(fils) = filters {
        for fil in fils {
            selector = selector.filter(fil);
        }
    }

    let pages = selector.into_model().paginate(db, s);
    let ItemsAndPagesNumber {
        number_of_items: count,
        number_of_pages: num_pages,
    } = pages.num_items_and_pages().await?;

    let p = page.unwrap_or(0).min(num_pages);

    let list = pages.fetch_page(p).await?;

    let res = PaginatedResponse {
        count,
        num_pages,
        list,
    };

    Ok(res)
}