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//! A version of a record
//!
//! A set of version can be flattened to represent the latest set
//! of changes of a record
use super::Payload;
use std::collections::BTreeMap;
/// An operation that was applied to a version
///
/// An operation is either an insert or a delete.
/// It also carries a string key and a payload value inside
/// a tuple. These are then summed together as a vector.
///
/// This means that if data contradicts itself in the same
/// version the later edit (call) will override the previous
#[derive(Debug, Serialize, Deserialize, Clone)]
pub enum Operation {
Insert(String, Payload),
Delete(String),
}
use self::Operation::{Insert, Delete};
/// Represents a series of operations done in sequence
/// that are applied to a record to preserve history of state
#[derive(Debug, Serialize, Deserialize)]
pub struct Version {
version: u64,
ops: Vec<Operation>,
}
impl Version {
/// Create a simple new version
pub fn new(ver: u64) -> Version {
return Version {
version: ver,
ops: Vec::new(),
};
}
/// Take a version full of operations and flatten it to a single
/// binary search tree that can be included into an embedded record
///
/// Non-mutable on the version itself
pub fn flatten(&self) -> BTreeMap<String, Payload> {
let mut map = BTreeMap::new();
/* For all operations, process them in order */
for op in &self.ops {
/* Match the operation */
match op {
&Insert(ref key, ref payload) => {
/* Match the return to log errors */
match map.insert(key.clone(), payload.clone()) {
None => {}
_ => println!("Overriding value {}", key),
}
}
&Delete(ref key) => {
/* Match the return to log errors */
match map.remove(key) {
None => println!("Failed to apply deletion: key doesn't exists!"),
_ => {}
}
}
}
}
/* Return the map */
return map;
}
/// A utility function which merges two versions onto &self
///
/// - If a key is present in `other`, `self.key` is overwritten
/// - If a key is missing in `other`, `self.key` is deleted
///
pub fn merge(&mut self, other: &Version) {
}
}
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