//! Copyright (c) 2022-2026 GitDataAi All rights reserved.

use crate::pb::{PageInfo, Pagination};

/// Simple offset-based pagination over an in-memory slice.
/// The `page_token` is a decimal string encoding the start offset.
pub fn paginate<T: Clone>(items: &[T], pagination: Option<&Pagination>) -> (Vec<T>, PageInfo) {
    let page_size = pagination
        .map(|p| p.page_size as usize)
        .unwrap_or(items.len().max(1))
        .max(1);

    let start_offset = pagination
        .and_then(|p| {
            if p.page_token.is_empty() {
                None
            } else {
                p.page_token.parse::<usize>().ok()
            }
        })
        .unwrap_or(0)
        .min(items.len());

    let end = start_offset.saturating_add(page_size).min(items.len());
    let has_next = end < items.len();
    let next_page_token = if has_next {
        end.to_string()
    } else {
        String::new()
    };

    (
        items[start_offset..end].to_vec(),
        PageInfo {
            next_page_token,
            has_next_page: has_next,
            total_count: items.len() as u64,
        },
    )
}

/// Apply sort direction. Ascending = no-op (preserves order).
/// Descending reverses the slice.
pub fn apply_sort<T>(items: &mut [T], sort_direction: i32) {
    if sort_direction == crate::pb::SortDirection::Desc as i32 {
        items.reverse();
    }
}