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timestamp)` The former form creates a new task. +It is invalid to create a task that already exists. + The latter form updates the given property of the given task. It is invalid to update a task that does not exist. The timestamp on updates serves as additional metadata and is used to resolve conflicts. diff --git a/src/errors.rs b/src/errors.rs new file mode 100644 index 000000000..08884376f --- /dev/null +++ b/src/errors.rs @@ -0,0 +1,7 @@ +use failure::Fail; + +#[derive(Debug, Fail, Eq, PartialEq, Clone)] +pub enum Error { + #[fail(display = "Task Database Error: {}", _0)] + DBError(String), +} diff --git a/src/lib.rs b/src/lib.rs new file mode 100644 index 000000000..e0be8b685 --- /dev/null +++ b/src/lib.rs @@ -0,0 +1,3 @@ +mod errors; +mod operation; +mod taskdb; diff --git a/src/main.rs b/src/main.rs deleted file mode 100644 index d4a28f0a7..000000000 --- a/src/main.rs +++ /dev/null @@ -1,7 +0,0 @@ -mod operation; - -// see https://raw.githubusercontent.com/Operational-Transformation/ot.js/master/dist/ot.js - -fn main() { - println!("Hello, world!"); -} diff --git a/src/taskdb.rs b/src/taskdb.rs new file mode 100644 index 000000000..02fd51da0 --- /dev/null +++ b/src/taskdb.rs @@ -0,0 +1,142 @@ +use crate::errors::Error; +use chrono::{DateTime, Utc}; +use serde_json::Value; +use std::collections::hash_map::Entry; +use std::collections::HashMap; +use uuid::Uuid; + +#[derive(PartialEq, Clone, Debug)] +enum Operation { + Create { + uuid: Uuid, + }, + Update { + uuid: Uuid, + property: String, + value: Value, + timestamp: DateTime, + }, +} + +struct DB { + // The current state, with all pending operations applied + tasks: HashMap>, + + // The version at which `operations` begins + base_version: u64, + + // Operations applied since `base_version`, in order. + // + // INVARIANT: Given a snapshot at `base_version`, applying these operations produces `tasks`. + operations: Vec, +} + +impl DB { + fn new() -> DB { + DB { + tasks: HashMap::new(), + base_version: 0, + operations: vec![], + } + } + + fn apply(&mut self, op: Operation) -> Result<(), Error> { + match op { + Operation::Create { uuid } => { + match self.tasks.entry(uuid) { + Entry::Occupied(_) => { + return Err(Error::DBError(format!("Task {} already exists", uuid))); + } + ent @ Entry::Vacant(_) => { + ent.or_insert(HashMap::new()); + } + }; + } + Operation::Update { + ref uuid, + ref property, + ref value, + timestamp: _, + } => { + match self.tasks.get_mut(uuid) { + Some(task) => { + task.insert(property.clone(), value.clone()); + } + None => { + return Err(Error::DBError(format!("Task {} does not exist", uuid))); + } + }; + } + }; + self.operations.push(op); + Ok(()) + } +} + +#[cfg(test)] +mod tests { + use super::*; + use uuid::Uuid; + + #[test] + fn test_apply_create() { + let mut db = DB::new(); + let uuid = Uuid::new_v4(); + let op = Operation::Create { uuid }; + db.apply(op.clone()).unwrap(); + + let mut exp = HashMap::new(); + exp.insert(uuid, HashMap::new()); + assert_eq!(db.tasks, exp); + assert_eq!(db.operations, vec![op]); + } + + #[test] + fn test_apply_create_exists() { + let mut db = DB::new(); + let uuid = Uuid::new_v4(); + db.apply(Operation::Create { uuid }).unwrap(); + assert_eq!( + db.apply(Operation::Create { uuid }), + Err(Error::DBError(format!("Task {} already exists", uuid))) + ); + } + + #[test] + fn test_apply_create_update() { + let mut db = DB::new(); + let uuid = Uuid::new_v4(); + let op1 = Operation::Create { uuid }; + db.apply(op1.clone()).unwrap(); + let op2 = Operation::Update { + uuid, + property: String::from("title"), + value: Value::from("\"my task\""), + timestamp: Utc::now(), + }; + db.apply(op2.clone()).unwrap(); + + let mut exp = HashMap::new(); + let mut task = HashMap::new(); + task.insert(String::from("title"), Value::from("\"my task\"")); + exp.insert(uuid, task); + assert_eq!(db.tasks, exp); + assert_eq!(db.operations, vec![op1, op2]); + } + + #[test] + fn test_apply_update_does_not_exist() { + let mut db = DB::new(); + let uuid = Uuid::new_v4(); + assert_eq!( + db.apply(Operation::Update { + uuid, + property: String::from("title"), + value: Value::from("\"my task\""), + timestamp: Utc::now(), + }), + Err(Error::DBError(format!("Task {} does not exist", uuid))) + ); + } + +}