Adding the beginning components of a parser and some tests.

.gitignore

@@ -0,0 +1,4 @@
+target/
+project/target/
+project/project/
+modules/core/target/

.pre-commit-config.yaml

@@ -5,8 +5,11 @@ repos:
     hooks:
       - id: end-of-file-fixer
       - id: trailing-whitespace
+      - id: check-yaml
       - id: fix-byte-order-marker
       - id: mixed-line-ending
-        args: ['--fix=lf']
-        description: Enforces using only 'LF' line endings.
-      - id: trailing-whitespace
+        args: [--fix=lf]
+  - repo: https://git.garrity.co/garrity-software/gs-pre-commit-scala
+    rev: v0.1.3
+    hooks:
+      - id: scalafmt

.scalafmt.conf

@@ -0,0 +1,71 @@
+// See: https://github.com/scalameta/scalafmt/tags for the latest tags.
+version = 3.7.11
+runner.dialect = scala3
+maxColumn = 80
+
+rewrite {
+    rules = [RedundantBraces, RedundantParens, Imports, SortModifiers]
+    imports.expand = true
+    imports.sort = scalastyle
+    redundantBraces.ifElseExpressions = true
+    redundantBraces.stringInterpolation = true
+}
+
+indent {
+    main = 2
+    callSite = 2
+    defnSite = 2
+    extendSite = 4
+    withSiteRelativeToExtends = 2
+    commaSiteRelativeToExtends = 2
+}
+
+align {
+    preset = more
+    openParenCallSite = false
+    openParenDefnSite = false
+}
+
+newlines {
+    implicitParamListModifierForce = [before,after]
+    topLevelStatementBlankLines = [
+        {
+            blanks = 1
+        }
+    ]
+    afterCurlyLambdaParams = squash
+}
+
+danglingParentheses {
+    defnSite = true
+    callSite = true
+    ctrlSite = true
+    exclude = []
+}
+
+verticalMultiline {
+    atDefnSite = true
+    arityThreshold = 2
+    newlineAfterOpenParen = true
+}
+
+comments {
+    wrap = standalone
+}
+
+docstrings {
+    style = "SpaceAsterisk"
+    oneline = unfold
+    wrap = yes
+    forceBlankLineBefore = true
+}
+
+project {
+  excludePaths = [
+    "glob:**target/**",
+    "glob:**.metals/**",
+    "glob:**.bloop/**",
+    "glob:**.bsp/**",
+    "glob:**metals.sbt"
+  ]
+}

LICENSE

@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
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README.md

@@ -3,11 +3,16 @@
 This repository is currently a research project. The project is to explore ideas
 in programming language design by specifying _Ava_.
 
-To start reading, please use the [Table of Contents](./table-of-contents.md)
-
 ## What is Ava?
 
 Ava is a programming language research project that is in the design and
 specification phase. There is no grammar, parser, compiler, or way to use any
 Ava code. Ava is a way to get ideas out of my head, challenged, and further
 explored.
+
+## Notes
+
+These notes are not guaranteed to be up to date and represent a large amount of
+brainstorming and trying/discarding of ideas.
+
+Please start with the [Table of Contents](./notes/table-of-contents.md)

build.sbt

@@ -0,0 +1,34 @@
+val scala3: String = "3.3.1"
+
+ThisBuild / scalaVersion  := scala3
+ThisBuild / versionScheme := Some("semver-spec")
+ThisBuild / gsProjectName := "ava"
+
+val sharedSettings = Seq(
+  scalaVersion := scala3,
+  version      := semVerSelected.value
+)
+
+lazy val testSettings = Seq(
+  libraryDependencies ++= Seq(
+    "org.scalameta" %% "munit" % "1.0.0-M11" % Test
+  )
+)
+
+lazy val ava = project
+  .in(file("."))
+  .aggregate(parser)
+  .settings(sharedSettings)
+  .settings(name := s"${gsProjectName.value}-v${semVerMajor.value}")
+
+lazy val parser = project
+  .in(file("modules/parser"))
+  .settings(sharedSettings)
+  .settings(testSettings)
+  .settings(name := s"${gsProjectName.value}-parser-v${semVerMajor.value}")
+  .settings(
+    libraryDependencies ++= Seq(
+      "co.fs2" %% "fs2-core" % "3.9.4",
+      "co.fs2" %% "fs2-io"   % "3.9.4"
+    )
+  )

modules/parser/src/main/scala/ava/parser/CharacterReader.scala

@@ -0,0 +1,128 @@
+package ava.parser
+
+import java.io.BufferedReader
+
+/** Used to consume characters from the input stream.
+  *
+  * @param input
+  *   Input stream capable of reading _characters_ rather than bytes. This
+  *   stream is owned by the character reader.
+  */
+class CharacterReader(
+  private val input: BufferedReader
+):
+  // Internal constants.
+  private val Capacity: Int         = 4096
+  private val LookBackCapacity: Int = 16
+
+  // Internal buffers.
+  private val lastChars: Ring[Char] = Ring[Char](LookBackCapacity, 0)
+  private val buffer: Array[Char]   = Array.fill(Capacity)(0)
+
+  // Internal mutable state.
+  private var length: Int          = 0
+  private var index: Int           = 0
+  private var eof: Boolean         = false
+  private var peekedAhead: Boolean = false
+  private var lookAhead: Char      = 0
+
+  /** Close the underlying stream.
+    */
+  def close(): Unit = input.close()
+
+  /** Set EOF and close the underlying stream.
+    */
+  private def setEof(): Unit =
+    eof = true
+    close()
+
+  /** Used when the buffer has been fully consumed. Reads as many characters as
+    * possible and resets internal state. Detects EOF and sets state
+    * accordingly.
+    */
+  private def fillBuffer(): Unit =
+    // TODO: Short circuit on EOF!
+    var numberOfCharacters = 0
+    if peekedAhead then
+      buffer(0) = lookAhead
+      numberOfCharacters = input.read(buffer, 1, Capacity - 1)
+    else numberOfCharacters = input.read(buffer, 0, Capacity)
+
+    // Record the number of characters ACTUALLY consumed by the stream.
+    // This is our working buffer size.
+    length = numberOfCharacters
+
+    // If no characters could be read, we're done.
+    // EDGE CASE: If we peeked ahead to the last character, we still technically
+    // have a valid buffer of length 1.
+    val _ =
+      if numberOfCharacters <= 0 && peekedAhead then
+        // Edge case: buffer of size 1.
+        length = 1
+      else if length <= 0 then
+        // EOF case: no characters remain.
+        length = 0
+        setEof()
+        input.close()
+      else
+        // Normal case: we read some number of characters.
+        length = numberOfCharacters + (if peekedAhead then 1 else 0)
+
+    // Reset the peeked state -- we already consumed it.
+    peekedAhead = false
+
+    // Reset the index position to start iterating through the buffer again.
+    index = 0
+
+  /** Observe, but do not consume, the next character in the stream. Note that
+    * if the buffer is fully consumed, this function must read the underlying
+    * stream but will _not_ refresh the buffer until the next character is
+    * consumed.
+    *
+    * @return
+    *   The next character value, or None if the stream is EOF.
+    */
+  def peek(): Option[Char] =
+    if eof then None
+    else if index == length then
+      // Special case -- try to read one.
+      peekedAhead = true
+      lookAhead = input.read().toChar
+      if lookAhead < 0 then
+        eof = true
+        None
+      else Some(lookAhead)
+    else Some(buffer(index))
+
+  def consume(): Option[Char] =
+    if eof then None
+    else if peekedAhead then
+      fillBuffer()
+      lastChars.push(lookAhead)
+      Some(lookAhead)
+    else if index == length then
+      fillBuffer()
+      if eof then None
+      else
+        val pos = index
+        index = index + 1
+        lastChars.push(buffer(pos))
+        Some(buffer(pos))
+    else
+      val pos = index
+      index = index + 1
+      lastChars.push(buffer(pos))
+      Some(buffer(pos))
+
+  /** @return
+    *   True if all data in the _buffer_ has been consumed, false otherwise.
+    */
+  def isBufferExhausted(): Boolean =
+    index >= length
+
+  /** @return
+    *   True if the stream is EOF, false otherwise. An EOF stream does NOT imply
+    *   that the buffer is exhausted.
+    */
+  def isEof(): Boolean =
+    eof

modules/parser/src/main/scala/ava/parser/Ring.scala

@@ -0,0 +1,101 @@
+package ava.parser
+
+import scala.reflect.ClassTag
+
+/** Basic ring buffer implementation.
+  *
+  * @param capacity
+  *   Buffer capacity.
+  * @param unit
+  *   The unit value -- used to populate the initial buffer.
+  */
+final class Ring[A: ClassTag] private (
+  val capacity: Int,
+  val unit: A
+):
+  private var currentSize: Int = 0
+  private var oldestIndex: Int = -1
+  private var newestIndex: Int = -1
+  private val data: Array[A]   = Array.fill(capacity)(unit)
+
+  /** Push new data into this buffer. If the buffer is at capacity, replace the
+    * oldest item in the buffer.
+    *
+    * @param value
+    *   The value to push into the buffer.
+    */
+  def push(value: A): Unit =
+    if currentSize <= 0 then
+      // Only used the first time data is pushed to the ring.
+      data(0) = value
+      oldestIndex = 0
+      newestIndex = 0
+      currentSize = 1
+    else if currentSize < capacity then
+      // Used when filling up the ring.
+      data(currentSize) = value
+      newestIndex = currentSize
+      currentSize = currentSize + 1
+    else
+      // We have met the capacity and need to start rolling through the oldest
+      // entries, one at a time
+      data(oldestIndex) = value
+      newestIndex = oldestIndex
+      oldestIndex = calculateNextOldest(oldestIndex)
+
+  /** Get the value of the newest item in the buffer. Does not care whether the
+    * buffer has been populated.
+    *
+    * @return
+    *   The newest value in the buffer.
+    */
+  def newest(): A =
+    if newestIndex < 0 then
+      throw new IllegalStateException(
+        "This ring has not been initialized with any data."
+      )
+    else data(newestIndex)
+
+  /** Extract a copy of this ring, ordered from newest to oldest.
+    *
+    * @return
+    *   Ordered copy of this ring from newest to oldest.
+    */
+  def newestToOldest(): Array[A] =
+    val output      = new Array[A](currentSize)
+    var outputIndex = 0
+    var ringPointer = newestIndex
+    while outputIndex < currentSize do
+      output(outputIndex) = data(ringPointer)
+      outputIndex = outputIndex + 1
+      ringPointer = calculateNextNewest(ringPointer)
+    output
+
+  /** Get the current size of the buffer.
+    *
+    * @return
+    *   The current size of the buffer.
+    */
+  def size(): Int = currentSize
+
+  private def calculateNextOldest(from: Int): Int =
+    if from < (currentSize - 1) then from + 1
+    else 0
+
+  private def calculateNextNewest(from: Int): Int =
+    if from > 0 then from - 1
+    else currentSize - 1
+
+object Ring:
+
+  def apply[A: ClassTag](
+    capacity: Int,
+    unit: A
+  ): Ring[A] =
+    if capacity > 0 then new Ring[A](capacity, unit)
+    else
+      throw new IllegalArgumentException(
+        "Rings may only be constructed with capacity > 0"
+      )
+
+end Ring

modules/parser/src/test/scala/ava/parser/RingTests.scala

@@ -0,0 +1,69 @@
+package ava.parser
+
+class RingTests extends munit.FunSuite:
+
+  test("should fail to instantiate with <= 0 capacity") {
+    interceptMessage[IllegalArgumentException](
+      "Rings may only be constructed with capacity > 0"
+    ) {
+      val _ = Ring[Int](-1, 0)
+    }
+    interceptMessage[IllegalArgumentException](
+      "Rings may only be constructed with capacity > 0"
+    ) {
+      val _ = Ring[Int](0, 0)
+    }
+  }
+
+  test("should return the buffer size independent of capacity") {
+    val capacity: Int = 4
+    val ring          = Ring[Int](capacity, 0)
+    assertEquals(ring.size(), 0)
+    assertEquals(ring.capacity, capacity)
+    assertEquals(ring.unit, 0)
+    var item = 1
+    while item <= capacity do
+      ring.push(item)
+      assertEquals(ring.size(), item)
+      item = item + 1
+  }
+
+  test("should fail to retrieve the newest element if not initialized") {
+    interceptMessage[IllegalStateException](
+      "This ring has not been initialized with any data."
+    ) {
+      val ring = Ring[Int](1, 0)
+      val _    = ring.newest()
+    }
+  }
+
+  test("should return the newest element of the ring") {
+    val capacity: Int = 4
+    val unit: Int     = 0
+    val ring          = Ring[Int](capacity, unit)
+    var item          = 1
+    while item <= capacity do
+      ring.push(item)
+      assertEquals(ring.newest(), item)
+      item = item + 1
+  }
+
+  test("should respect ordering across cycles") {
+    val capacity: Int = 4
+    val unit: Int     = 0
+    val ring          = Ring[Int](capacity, unit)
+    var item          = 1
+    while item <= capacity do
+      ring.push(item)
+      item = item + 1
+
+    assertEquals(ring.size(), capacity)
+    val expected = Array[Int](5, 4, 3, 2)
+    item = 1
+    while item <= capacity + 1 do
+      ring.push(item)
+      item = item + 1
+      assertEquals(ring.size(), capacity)
+    val extract = ring.newestToOldest()
+    assert(extract.sameElements(expected))
+  }

project/build.properties

@@ -0,0 +1 @@
+sbt.version=1.9.8

project/plugins.sbt

@@ -0,0 +1,10 @@
+credentials += Credentials(Path.userHome / ".sbt" / ".credentials")
+
+externalResolvers := Seq(
+  "Garrity Software Mirror" at "https://maven.garrity.co/releases",
+  "Garrity Software Releases" at "https://maven.garrity.co/gs"
+)
+
+addSbtPlugin("org.scoverage" % "sbt-scoverage"        % "2.0.8")
+addSbtPlugin("gs"            % "sbt-garrity-software" % "0.2.0")
+addSbtPlugin("gs"            % "sbt-gs-semver"        % "0.2.0")