tenebrous-dicebot/src/db.rs

135 lines
3.9 KiB
Rust
Raw Normal View History

use byteorder::LittleEndian;
use sled::{Db, IVec};
use std::collections::HashMap;
use thiserror::Error;
use zerocopy::byteorder::I32;
use zerocopy::{AsBytes, LayoutVerified};
/// User variables are stored as little-endian 32-bit integers in the
/// database. This type alias makes the database code more pleasant to
/// read.
type LittleEndianI32Layout<'a> = LayoutVerified<&'a [u8], I32<LittleEndian>>;
#[derive(Clone)]
pub struct Database {
db: Db,
}
//TODO better combining of key and value in certain errors (namely
//I32SchemaViolation).
#[derive(Error, Debug)]
pub enum DataError {
#[error("value does not exist for key: {0}")]
KeyDoesNotExist(String),
#[error("expected i32, but i32 schema was violated")]
I32SchemaViolation,
#[error("expected string, but utf8 schema was violated: {0}")]
Utf8chemaViolation(#[from] std::str::Utf8Error),
#[error("internal database error: {0}")]
InternalError(#[from] sled::Error),
}
fn to_key(room_id: &str, username: &str, variable_name: &str) -> Vec<u8> {
let mut key = vec![];
key.extend_from_slice(room_id.as_bytes());
key.extend_from_slice(username.as_bytes());
key.extend_from_slice(variable_name.as_bytes());
key
}
fn to_prefix(room_id: &str, username: &str) -> Vec<u8> {
let mut prefix = vec![];
prefix.extend_from_slice(room_id.as_bytes());
prefix.extend_from_slice(username.as_bytes());
prefix
}
fn convert(raw_value: &[u8]) -> Result<i32, DataError> {
let layout = LittleEndianI32Layout::new_unaligned(raw_value.as_ref());
if let Some(layout) = layout {
let value: I32<LittleEndian> = *layout;
Ok(value.get())
} else {
Err(DataError::I32SchemaViolation)
}
}
impl Database {
pub fn new(db: &Db) -> Database {
Database { db: db.clone() }
}
pub async fn get_user_variables(
&self,
room_id: &str,
username: &str,
) -> Result<HashMap<String, i32>, DataError> {
let prefix = to_prefix(&room_id, &username);
let prefix_len: usize = prefix.len();
let variables: Result<Vec<_>, DataError> = self
.db
.scan_prefix(prefix)
.map(|entry| match entry {
Ok((key, raw_value)) => {
//Strips room and username from key, leaving
//behind name.
let variable_name = std::str::from_utf8(&key[prefix_len..])?;
Ok((variable_name.to_owned(), convert(&raw_value)?))
}
Err(e) => Err(e.into()),
})
.collect();
//Convert to hash map. Can we do this in the first mapping
//step instead?
variables.map(|entries| entries.into_iter().collect())
}
pub async fn get_user_variable(
&self,
room_id: &str,
username: &str,
variable_name: &str,
) -> Result<i32, DataError> {
let key = to_key(room_id, username, variable_name);
if let Some(raw_value) = self.db.get(&key)? {
convert(&raw_value)
} else {
Err(DataError::KeyDoesNotExist(String::from_utf8(key).unwrap()))
}
}
pub async fn set_user_variable(
&self,
room_id: &str,
username: &str,
variable_name: &str,
value: i32,
) -> Result<(), DataError> {
let key = to_key(room_id, username, variable_name);
let db_value: I32<LittleEndian> = I32::new(value);
self.db.insert(&key, IVec::from(db_value.as_bytes()))?;
Ok(())
}
pub async fn delete_user_variable(
&self,
room_id: &str,
username: &str,
variable_name: &str,
) -> Result<(), DataError> {
let key = to_key(room_id, username, variable_name);
if let Some(_) = self.db.remove(&key)? {
Ok(())
} else {
Err(DataError::KeyDoesNotExist(String::from_utf8(key).unwrap()))
}
}
}