Adding Prune command

ots-cli.js

@@ -44,6 +44,20 @@ const infoCommand = program
     info(file, options)
   })
 
+const pruneCommand = program
+  .command('prune [FILE_OTS]')
+  .alias('p')
+  .description('Prune timestamp.')
+  .action((file, options) => {
+    isExecuted = true
+    if (!file) {
+      console.log(pruneCommand.helpInformation())
+      return
+    }
+    options = parseCommon(options)
+    prune(file, options)
+  })
+
 const stampCommand = program
   .command('stamp [FILE...]')
   .alias('s')
@@ -185,6 +199,45 @@ function info (argsFileOts, options) {
   })
 }
 
+function prune (argsFileOts, options) {
+  const files = []
+  files.push(Utils.readFilePromise(argsFileOts, null))
+  Promise.all(files).then(values => {
+    const fileOts = values[0]
+
+    // Read ots file and check hash function
+    let detachedOts
+    try {
+      detachedOts = DetachedTimestampFile.deserialize(fileOts)
+    } catch (err) {
+      if (err instanceof Context.BadMagicError) {
+        throw new Error('Error! ' + argsFileOts + ' is not a timestamp file.')
+      } else if (err instanceof Context.DeserializationError) {
+        throw new Error('Invalid timestamp file ' + argsFileOts)
+      } else {
+        throw err
+      }
+    }
+    // Opentimestamps prune
+    OpenTimestamps.prune(detachedOts, options)
+      .then(function (results) {
+        // Backup the file and create the new receipt
+        fs.renameSync(argsFileOts, argsFileOts + '.bak')
+        fs.writeFile(argsFileOts, Buffer.from(detachedOts.serializeToBytes()), 'binary', err => { if (err) { console.log('Error in serialization') } })
+        console.log('Recepit Pruned')
+      }).catch(err => {
+        console.log('Is not possible to prune due to ' + err)
+      })
+  }).catch(err => {
+    if (err.code === 'ENOENT') {
+      console.error('File not found \'' + err.path + '\'')
+    } else {
+      console.error(err.message)
+    }
+    process.exit(1)
+  })
+}
+
 function stamp (argsFiles, options) {
   // check input params : file/hash
   const filePromises = []

src/calendar.js

@@ -20,6 +20,7 @@ const Message = require('bitcore-message')
 const Utils = require('./utils.js')
 const Context = require('./context.js')
 const Timestamp = require('./timestamp.js')
+const { URL } = require('url')
 
 /* Errors */
 const CommitmentNotFoundError = Error.extend('CommitmentNotFoundError')

src/open-timestamps.js

@@ -97,6 +97,71 @@ module.exports = {
     return JSON.stringify(json)
   },
 
+  /*
+  * Delete all the dead branches
+  */
+  pruneTree (timestamp) {
+    let prun = timestamp.attestations.length === 0
+    let changed = false
+
+    for (const element of timestamp.ops) {
+      var result = this.pruneTree(element[1])
+      var stampPrunable = result.prunable
+      var stampChanged = result.change
+      changed = changed || stampChanged || stampPrunable
+      if (stampPrunable) {
+        timestamp.ops.delete(element[0])
+      } else {
+        prun = false
+      }
+    }
+    return { prunable: prun, change: changed }
+  },
+
+  /*
+  * Delete all the leaves which didn't match the height passed
+  */
+  discard_attestation (timestamp, heightToKeep) {
+    timestamp.getAttestations().forEach(opStamp => {
+      if (!(opStamp instanceof Notary.BitcoinBlockHeaderAttestation && opStamp.height === heightToKeep)) {
+        timestamp.attestations.splice(timestamp.attestations.indexOf(opStamp), 1)
+      }
+    })
+    var iter = timestamp.ops.values()
+    let res = iter.next()
+    while (!res.done) {
+      this.discard_attestation(res.value)
+      res = iter.next()
+    }
+  },
+  /**
+   * Prune a timestamp dropping the redundant data included in the ots receipt, storing only the linear proof from the file hash to the best attestation.
+   * @exports OpenTimestamps/prune
+   * @param {DetachedTimestampFile[]} detaches - The array of detached file to stamp; input/output parameter.
+   * @param {Object} options - The option arguments. Not used yet
+  */
+  prune (detaches, options = {}) {
+    let prunable = false
+    let maxHead = 0
+
+    if (detaches.timestamp.getAttestations().length <= 1) {
+      return new Promise((resolve, reject) => { reject(new Error('Just one attestation founded')) })
+    }
+    detaches.timestamp.getAttestations().forEach(subStamp => {
+      if (subStamp instanceof Notary.BitcoinBlockHeaderAttestation) {
+        prunable = true
+        maxHead = (maxHead < subStamp.height) ? subStamp.height : maxHead
+      }
+    })
+    if (prunable) {
+      this.discard_attestation(detaches.timestamp, maxHead)
+      this.pruneTree(detaches.timestamp)
+      return new Promise((resolve, reject) => { resolve(detaches) })
+    } else {
+      return new Promise((resolve, reject) => { reject(new Error('There are no Bitcoin Attestation in the file')) })
+    }
+  },
+
   /**
    * Create timestamp with the aid of a remote calendar for one or multiple files.
    * @exports OpenTimestamps/stamp

test/calendar.js

@@ -1,6 +1,7 @@
 const test = require('tape')
 const Calendar = require('../src/calendar.js')
 const Utils = require('../src/utils.js')
+const { URL } = require('url')
 
 test('Calendar.privateSubmit()', assert => {
   const digest = Array.from(Utils.randBytes(32))