pagination.rs

use std::str::FromStr;

//  Copyright (C) 2020 Éloïs SANCHEZ.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

use crate::*;

const MAX_PAGE_SIZE: u32 = 10_000;

#[derive(Clone, Copy, async_graphql::Enum, Eq, PartialEq)]
pub(crate) enum Order {
    /// Ascending order
    Asc,
    /// Decreasing order
    Desc,
}
impl Default for Order {
    fn default() -> Self {
        Order::Asc
    }
}

#[derive(async_graphql::InputObject)]
pub(crate) struct Pagination {
    /// Identifier of the 1st desired element (of the last one in descending order)
    cursor: Option<String>,
    ord: Order,
    page_size: u32,
}

impl Default for Pagination {
    fn default() -> Self {
        Pagination {
            cursor: None,
            ord: Order::default(),
            page_size: 10,
        }
    }
}

impl Pagination {
    pub(crate) fn convert_to_page_info<
        E: 'static + std::error::Error + Send + Sync,
        T: FromStr<Err = E>,
    >(
        self,
        is_whitelisted: bool,
    ) -> anyhow::Result<duniter_gva_dbs_reader::PageInfo<T>> {
        let page_size = if is_whitelisted || (self.page_size > 0 && self.page_size <= MAX_PAGE_SIZE)
        {
            NonZeroUsize::new(self.page_size as usize)
        } else {
            return Err(anyhow::Error::msg("pageSize must be between 1 and 10000."));
        };
        Ok(duniter_gva_dbs_reader::PageInfo::new(
            self.cursor.map(|c| T::from_str(&c)).transpose()?,
            self.ord == Order::Asc,
            page_size,
        ))
    }
}