1 files changed, 80 insertions, 0 deletions
diff --git a/src/dotty/tools/dotc/repl/ammonite/FilterTools.scala b/src/dotty/tools/dotc/repl/ammonite/FilterTools.scala
new file mode 100644
index 000000000..c18b6a927
--- /dev/null
+++ b/src/dotty/tools/dotc/repl/ammonite/FilterTools.scala
@@ -0,0 +1,80 @@
+package dotty.tools
+package dotc
+package repl
+package ammonite.terminal
+
+/**
+ * A collection of helpers that to simpify the common case of building filters
+ */
+object FilterTools {
+  val ansiRegex = "\u001B\\[[;\\d]*."
+
+  def offsetIndex(buffer: Vector[Char], in: Int) = {
+    var splitIndex = 0
+    var length = 0
+
+    while(length < in) {
+      ansiRegex.r.findPrefixOf(buffer.drop(splitIndex)) match {
+        case None =>
+          splitIndex += 1
+          length += 1
+        case Some(s) =>
+          splitIndex += s.length
+      }
+    }
+    splitIndex
+  }
+
+  /**
+   * Shorthand to construct a filter in the common case where you're
+   * switching on the prefix of the input stream and want to run some
+   * transformation on the buffer/cursor
+   */
+  def Case(s: String)
+          (f: (Vector[Char], Int, TermInfo) => (Vector[Char], Int)) = new Filter {
+    val op = new PartialFunction[TermInfo, TermAction] {
+      def isDefinedAt(x: TermInfo) = {
+
+        def rec(i: Int, c: LazyList[Int]): Boolean = {
+          if (i >= s.length) true
+          else if (c.head == s(i)) rec(i + 1, c.tail)
+          else false
+        }
+        rec(0, x.ts.inputs)
+      }
+
+      def apply(v1: TermInfo) = {
+        val (buffer1, cursor1) = f(v1.ts.buffer, v1.ts.cursor, v1)
+        TermState(
+          v1.ts.inputs.dropPrefix(s.map(_.toInt)).get,
+          buffer1,
+          cursor1
+        )
+      }
+
+    }.lift
+    def identifier = "Case"
+  }
+
+  /** Shorthand for pattern matching on [[TermState]] */
+  val TS = TermState
+
+  def findChunks(b: Vector[Char], c: Int) = {
+    val chunks = Terminal.splitBuffer(b)
+    // The index of the first character in each chunk
+    val chunkStarts = chunks.inits.map(x => x.length + x.sum).toStream.reverse
+    // Index of the current chunk that contains the cursor
+    val chunkIndex = chunkStarts.indexWhere(_ > c) match {
+      case -1 => chunks.length-1
+      case x => x - 1
+    }
+    (chunks, chunkStarts, chunkIndex)
+  }
+
+  def firstRow(cursor: Int, buffer: Vector[Char], width: Int) =
+    cursor < width && (buffer.indexOf('\n') >= cursor || buffer.indexOf('\n') == -1)
+
+  def lastRow(cursor: Int, buffer: Vector[Char], width: Int) =
+    (buffer.length - cursor) < width &&
+      (buffer.lastIndexOf('\n') < cursor || buffer.lastIndexOf('\n') == -1)
+}