dstate

Store changing state data as commits that can be rolled back

dstate is used to save state data history in a LevelUP database as commit objects. Each commit is stored as a delta of the state, so you can efficiently store many commits.

Usage

npm install dstate

var DState = require('dstate')

// db is a levelup instance
var ds = new DState(db)

// commit some states
ds.commit({ foo: 'bar', baz: [ 0, 1, 2 ] })
ds.commit({ foo: 'bar2', baz: [ 1, 2, 3 ] })
ds.commit({ foo: 'bar3', baz: [ 2, 3, 4 ], lol: true })

// get current state
ds.getState((err, state) => { ... })

// roll back to first commit
ds.rollback(0)

// remove the first 2 commits
ds.prune(1)

---

new DState(db)

Creates a DState which stores data in db.

db should be a LevelUp instance. The db should not be shared (if necessary, use level-sublevel to create a sub-section of your db).

---

state.commit(state, [opts], [callback])

Creates a commit that changes the state to state.

opts may contain:

• tx Level Transaction (default: null) - If provided, the database operations for this commit will be made via tx (so consistency can be ensured with other db operations).

callback is called with callback(err, index) where index is a number representing the index of the commit that was made.

---

state.rollback(index, [opts], [callback])

Reverts the state to what is was in the commit with index index.

index should be a number, where 0 is the first commit, etc. It must be less than the index of the most recent commit.

opts may contain:

• tx Level Transaction (default: null) - If provided, the database operations for this commit will be made via tx (so consistency can be ensured with other db operations).

---

state.getState(callback)

Calls callback(err, state) with the current state. If no state has been committed yet, state will be null.

---

state.getIndex(callback)

Calls callback(err, index) with the latest commit index (a number, incrementing on each commit). If no state has been committed yet, index will be null.

---

state.prune(index, [opts], [callback])

Removes all the commits up to index index (inclusive). The state will not be able to be rolled back to the pruned commits.

index should be a number, where 0 is the first commit, etc. It must be less than the index of the most recent commit.

opts may contain:

• tx Level Transaction (default: null) - If provided, the database operations for this commit will be made via tx (so consistency can be ensured with other db operations).