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).