use anyhow::{bail, Error};
use serde_json::Value;

/// Helper to store data, accessible by integer ID
///
/// Lookup data by ID is very fast, so this can be used to
/// generate integer handles to pass them to "C" code.
pub struct Registry<T> {
    info_list: Vec<T>,
    file_list: Vec<Value>,
}

impl<T> Registry<T> {

    /// Create a new instance
    pub fn new() -> Self {
        Self {
            info_list: Vec::new(),
            file_list: Vec::new(),
        }
    }

    /// Register data, returns associated ID
    pub fn register(&mut self, info: T) -> Result<u8, Error> {
        let dev_id = self.info_list.len();
        if dev_id > 255 {
            bail!("register failed - too many images/archives (limit is 255)");
        }
        self.info_list.push(info);
        Ok(dev_id as u8)
    }

    /// Lookup previously registered data by ID
    pub fn lookup(&mut self, id: u8) -> Result<&mut T, Error> {
        if id as usize >= self.info_list.len() {
            bail!("lookup failed for id = {}", id);
        }
        Ok(&mut self.info_list[id as usize])
    }

    /// Store info in a list
    ///
    /// We use this to store data for the backup manifest.
    pub fn add_file_info(&mut self, info: Value) {
        self.file_list.push(info);
    }

    /// Returns the list produced with add_file_info()
    pub fn file_list(&self) -> &[Value] {
        &self.file_list
    }
}