// Copyright (c) 2019 Target Brands, Inc.
// Copyright 2018-2020 Cargill Incorporated
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

pub const DEFAULT_LIMIT: usize = 100;
pub const DEFAULT_OFFSET: usize = 0;

#[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
pub struct Paging {
    pub current: String,
    pub offset: usize,
    pub limit: usize,
    pub total: usize,
    pub first: String,
    pub prev: String,
    pub next: String,
    pub last: String,
}

pub fn get_response_paging_info(
    limit: Option<usize>,
    offset: Option<usize>,
    link: &str,
    query_count: usize,
) -> Paging {
    let limit = limit.unwrap_or(DEFAULT_LIMIT);
    let offset = offset.unwrap_or(DEFAULT_OFFSET);

    let base_link = {
        // if the link does not already contain ? add it to the end
        if !link.contains('?') {
            format!("{}?limit={}&", link, limit)
        } else {
            format!("{}limit={}&", link, limit)
        }
    };

    let current_link = format!("{}offset={}", base_link, offset);

    let first_link = format!("{}offset=0", base_link);

    let previous_offset = if offset > limit { offset - limit } else { 0 };

    let previous_link = format!("{}offset={}", base_link, previous_offset);

    let last_offset = if query_count > 0 {
        ((query_count - 1) / limit) * limit
    } else {
        0
    };
    let last_link = format!("{}offset={}", base_link, last_offset);

    let next_offset = if offset + limit > last_offset {
        last_offset
    } else {
        offset + limit
    };

    let next_link = format!("{}offset={}", base_link, next_offset);

    Paging {
        current: current_link,
        offset,
        limit,
        total: query_count,
        first: first_link,
        prev: previous_link,
        next: next_link,
        last: last_link,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    const TEST_LINK: &str = "/api/test?";

    #[test]
    fn test_default_paging_response() {
        // Create paging response from default limit, default offset, a total of 1000
        let test_paging_response = get_response_paging_info(None, None, TEST_LINK, 1000);
        let generated_paging_response =
            create_test_paging_response(DEFAULT_OFFSET, DEFAULT_LIMIT, 100, 0, 900);
        assert_eq!(test_paging_response, generated_paging_response);
    }

    #[test]
    fn test_50offset_paging_response() {
        // Create paging response from default limit, offset of 50, and a total of 1000
        let test_paging_response = get_response_paging_info(None, Some(50), TEST_LINK, 1000);
        let generated_paging_response = create_test_paging_response(50, DEFAULT_LIMIT, 150, 0, 900);
        assert_eq!(test_paging_response, generated_paging_response);
    }

    #[test]
    fn test_550offset_paging_response() {
        // Create paging response from default limit, offset value of 150, and a total of 1000
        let test_paging_response = get_response_paging_info(None, Some(550), TEST_LINK, 1000);
        let generated_paging_response =
            create_test_paging_response(550, DEFAULT_LIMIT, 650, 450, 900);
        assert_eq!(test_paging_response, generated_paging_response);
    }

    #[test]
    fn test_950offset_paging_response() {
        // Create paging response from default limit, offset value of 950, and a total of 1000
        let test_paging_response = get_response_paging_info(None, Some(950), TEST_LINK, 1000);
        let generated_paging_response =
            create_test_paging_response(950, DEFAULT_LIMIT, 900, 850, 900);
        assert_eq!(test_paging_response, generated_paging_response);
    }

    #[test]
    fn test_50limit_paging_response() {
        // Create paging response from default limit, offset of 50, and a total of 1000
        let test_paging_response = get_response_paging_info(Some(50), None, TEST_LINK, 1000);
        let generated_paging_response = create_test_paging_response(DEFAULT_OFFSET, 50, 50, 0, 950);
        assert_eq!(test_paging_response, generated_paging_response);
    }

    #[test]
    fn test_50limit_150offset_paging_response() {
        // Create paging response from limit of 50, offset of 150, and total of 1000
        let test_paging_response = get_response_paging_info(Some(50), Some(150), TEST_LINK, 1000);
        let generated_paging_response = create_test_paging_response(150, 50, 200, 100, 950);
        assert_eq!(test_paging_response, generated_paging_response);
    }

    fn create_test_paging_response(
        offset: usize,
        limit: usize,
        next_offset: usize,
        previous_offset: usize,
        last_offset: usize,
    ) -> Paging {
        // Creates a generated paging response from the limit and offset values passed into the function
        let base_link = format!("{}limit={}&", TEST_LINK, limit);
        let current_link = format!("{}offset={}", base_link, offset);
        let first_link = format!("{}offset=0", base_link);
        let next_link = format!("{}offset={}", base_link, next_offset);
        let previous_link = format!("{}offset={}", base_link, previous_offset);
        let last_link = format!("{}offset={}", base_link, last_offset);

        Paging {
            current: current_link,
            offset,
            limit,
            total: 1000,
            first: first_link,
            prev: previous_link,
            next: next_link,
            last: last_link,
        }
    }
}