91 lines
2.5 KiB
Rust
91 lines
2.5 KiB
Rust
use byteorder::LittleEndian;
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use sled::{Db, IVec};
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use thiserror::Error;
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use zerocopy::byteorder::I32;
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use zerocopy::{AsBytes, LayoutVerified};
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/// User variables are stored as little-endian 32-bit integers in the
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/// database. This type alias makes the database code more pleasant to
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/// read.
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type LittleEndianI32Layout<'a> = LayoutVerified<&'a [u8], I32<LittleEndian>>;
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#[derive(Clone)]
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pub struct Database {
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db: Db,
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}
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#[derive(Error, Debug)]
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pub enum DataError {
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#[error("value does not exist for key: {0}")]
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KeyDoesNotExist(String),
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#[error("key violates expected schema: {0}")]
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SchemaViolation(String),
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#[error("internal database error: {0}")]
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InternalError(#[from] sled::Error),
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}
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fn to_key(room_id: &str, username: &str, variable_name: &str) -> Vec<u8> {
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let mut key = vec![];
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key.extend_from_slice(room_id.as_bytes());
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key.extend_from_slice(username.as_bytes());
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key.extend_from_slice(variable_name.as_bytes());
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key
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}
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impl Database {
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pub fn new(db: &Db) -> Database {
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Database { db: db.clone() }
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}
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pub async fn get_user_variable(
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&self,
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room_id: &str,
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username: &str,
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variable_name: &str,
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) -> Result<i32, DataError> {
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let key = to_key(room_id, username, variable_name);
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if let Some(raw_value) = self.db.get(&key)? {
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let layout = LittleEndianI32Layout::new_unaligned(raw_value.as_ref());
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if let Some(layout) = layout {
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let value: I32<LittleEndian> = *layout;
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Ok(value.get())
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} else {
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Err(DataError::SchemaViolation(String::from_utf8(key).unwrap()))
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}
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} else {
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Err(DataError::KeyDoesNotExist(String::from_utf8(key).unwrap()))
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}
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}
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pub async fn set_user_variable(
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&self,
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room_id: &str,
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username: &str,
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variable_name: &str,
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value: i32,
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) -> Result<(), DataError> {
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let key = to_key(room_id, username, variable_name);
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let db_value: I32<LittleEndian> = I32::new(value);
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self.db.insert(&key, IVec::from(db_value.as_bytes()))?;
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Ok(())
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}
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pub async fn delete_user_variable(
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&self,
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room_id: &str,
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username: &str,
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variable_name: &str,
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) -> Result<(), DataError> {
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let key = to_key(room_id, username, variable_name);
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if let Some(_) = self.db.remove(&key)? {
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Ok(())
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} else {
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Err(DataError::KeyDoesNotExist(String::from_utf8(key).unwrap()))
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}
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}
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}
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