// trifid-api, an open source reimplementation of the Defined Networking nebula management server.
//     Copyright (C) 2023 c0repwn3r
//
//     This program is free software: you can redistribute it and/or modify
//     it under the terms of the GNU 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 General Public License for more details.
//
//     You should have received a copy of the GNU General Public License
//     along with this program.  If not, see <https://www.gnu.org/licenses/>.

use base64::Engine;
use serde::{Deserialize, Serialize};
use std::error::Error;

#[derive(Serialize, Deserialize, Debug, Clone)]
pub struct Cursor {
    pub page: u64,
}

impl TryFrom<Cursor> for String {
    type Error = Box<dyn Error>;

    fn try_from(value: Cursor) -> Result<Self, Self::Error> {
        // Serialize it to json
        let json_str = serde_json::to_string(&value)?;
        // Then base64-encode the json
        let base64_str = base64::engine::general_purpose::STANDARD.encode(json_str);
        Ok(base64_str)
    }
}

impl TryFrom<String> for Cursor {
    type Error = Box<dyn Error>;

    fn try_from(value: String) -> Result<Self, Self::Error> {
        if value.is_empty() {
            // If empty, it's page 0
            return Ok(Cursor { page: 0 });
        }
        // Base64-decode the value
        let json_bytes = base64::engine::general_purpose::STANDARD.decode(value)?;
        // Convert it into a string
        let json_str = String::from_utf8(json_bytes)?;
        // Deserialize it from json
        let cursor = serde_json::from_str(&json_str)?;
        Ok(cursor)
    }
}