squash

Author: sonnyp

README.md

@@ -127,8 +127,7 @@ Because `buildPatchFromRevert + apply` offers more flexibility over `revert` it
 * use [pack/unpack](#patch-size) with the result of `buildPatchFromRevert` making it ideal for storage or transport
 * reverse a revert (and so on...) with `{reversible: true}`
 * [diff](#diff) between reverts
-* merge multiple reverts into one
-* rebase reverts
+* concat, squash, rebase multiple reverts
 
 [↑](#json8-patch)
 

index.js

@@ -31,3 +31,4 @@ module.exports.unpack = require('./lib/unpack')
 
 // Utilities
 module.exports.concat = require('./lib/concat')
+module.exports.squash = require('./lib/squash')

lib/squash.js

@@ -0,0 +1,56 @@
+'use strict'
+
+function wasModified(patch, path) {
+  for (var i = 0; i < patch.length; i++) {
+    var op = patch[i]
+    if (op.path !== path) continue
+    if (op.op === 'add' || op.op === 'replace' || op.op === 'remove' || op.op === 'move' || op.op === 'copy') return true
+  }
+  return false
+}
+
+module.exports = function squash(patch) {
+  var squashed = []
+
+  var push = true
+
+  patch.forEach(function(op) {
+    // if current op overrides previous operations, remove them
+    if (['add', 'replace', 'remove', 'move', 'copy'].indexOf(op.op) !== -1) {
+      squashed.forEach(function(prev, idx) {
+        if (prev.op === 'test') return
+        if (prev.path === op.path) { // same path - FIXME children/parents ?
+          if (wasModified(squashed, op.path)) {
+            squashed[idx] = undefined
+          }
+
+          // the path was created in the patch, the remove operation shouldn't be included
+          // example
+          //  {"path": "/foo", "op": "add", "value": "foo"},
+          //  {"path": "/foo", "op": "remove"}
+          if (op.op === 'remove') {
+            push = false
+          }
+          // the path was created in the patch, replace op requires the target to exist
+          // example
+          // {"path": "/foo", "op": "add", "value": "foo"},
+          // {"path": "/foo", "op": "replace", "value": "bar"}
+          else if (op.op === 'replace') {
+            // push = false
+            op = {"path": op.path, "op": "add", "value": op.value}
+          }
+        }
+      })
+    }
+
+    if (push) {
+      squashed.push(op)
+    }
+  })
+
+  var foo = []
+  squashed.forEach(function(op) {
+    if (op !== undefined) foo.push(op)
+  })
+  return foo
+}