implement binaural beat generation engine and CLI application.

Author: zachgrayio

.bazelignore

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+build --strategy=Scalac=worker
+build --worker_sandboxing

.bazelrc

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+2.0.0

.bazelversion

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+_run/*
+
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+
+# Docker project generated files to ignore
+#  if you want to ignore files created by your editor/tools,
+#  please consider a global .gitignore https://help.github.com/articles/ignoring-files
+.vagrant*
+bin
+docker/docker
+.*.swp
+a.out
+*.orig
+build_src
+.flymake*
+.idea
+.DS_Store
+docs/_build
+docs/_static
+docs/_templates
+.gopath/
+.dotcloud
+*.test
+bundles/
+.hg/
+.git/
+vendor/pkg/
+pyenv
+Vagrantfile
+**/Payload
+
+# Ignore backup files.
+*~
+# Ignore Vim swap files.
+.*.swp
+# Ignore files generated by IDEs.
+**/.classpath
+**/.factorypath
+# ignoring these breaks shared runconfigs so everyone will need to manually configure their run commands and flags. Have fun!
+**/.idea/
+**/.ijwb/
+**/.project
+**/.settings
+**/.vscode/
+**/bazel.iml
+# Ignore all bazel-* symlinks. There is no full list since this can change
+# based on the name of the directory bazel is cloned into.
+**/bazel-*
+# Ignore outputs generated during Bazel bootstrapping.
+**/output/
+# Ignore jekyll build output.
+production
+.sass-cache
+# User-specific .bazelrc
+user.bazelrc

.gitignore

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+

BUILD

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+# Binaural Beats Generator
+
+A binaural beat is an [auditory illusion](https://en.wikipedia.org/wiki/Auditory_illusion)  [perceived](https://en.wikipedia.org/wiki/Perception) when two different pure-tone [sine waves](https://en.wikipedia.org/wiki/Sine_wave), both with [frequencies](https://en.wikipedia.org/wiki/Frequency) lower than 1500 Hz, with less than a 40 Hz difference between them, are presented to a [listener](https://en.wikipedia.org/wiki/Hearing) dichotically (one through each [ear](https://en.wikipedia.org/wiki/Ear)).
+
+This command line program generates binaural beats.
+
+## Build & Run from Source:
+
+```bash
+bazel run //cli:app -- alpha
+```
+
+## Usage:
+
+```
+Usage: binaural [delta|theta|alpha|beta|gamma] [options]
+
+Command: delta
+Delta pattern preset; Binaural beats in the delta pattern operate at a frequency of 0.5–4 Hz with links to a dreamless sleep.
+Command: theta
+Theta pattern preset; Practitioners set binaural beats in the theta pattern to a frequency of 4–7 Hz. Theta patterns contribute to improved meditation, creativity, and sleep in the rapid eye movement (REM) phase.
+Command: alpha
+Alpha pattern preset; Binaural beats in the alpha pattern are at a frequency of 7–13 Hz and may encourage relaxation.
+Command: beta
+Beta pattern preset; Binaural beats in the beta pattern are at a frequency of 13–30 Hz. This frequency range may help promote concentration and alertness. However, it can also increase anxiety at the higher end of the range.
+Command: gamma
+Gamma pattern preset; This frequency pattern accounts for a range of 30–50 Hz. The study authors suggest that frequencies promote maintenance of arousal while a person is awake.
+  -p, --pitch <value>           the frequency in Hz - an integer property
+  -b, --binaural_pitch <value>  the binaural tone's frequency - a decimal property
+  -d, --duration <value>        the duration for which to play the binaural audio - an integer property
+```
+
+## More About Binaural Beats:
+(via Wikipedia)
+
+A binaural beat is an [auditory illusion](https://en.wikipedia.org/wiki/Auditory_illusion)  [perceived](https://en.wikipedia.org/wiki/Perception) when two different pure-tone [sine waves](https://en.wikipedia.org/wiki/Sine_wave), both with [frequencies](https://en.wikipedia.org/wiki/Frequency) lower than 1500 Hz, with less than a 40 Hz difference between them, are presented to a [listener](https://en.wikipedia.org/wiki/Hearing) dichotically (one through each [ear](https://en.wikipedia.org/wiki/Ear)).
+
+For example, if a 530 Hz pure [tone](https://en.wikipedia.org/wiki/Pitch_(music)) is presented to a subject's right ear, while a 520 Hz pure tone is presented to the subject's left ear, the listener will perceive the [auditory illusion](https://en.wikipedia.org/wiki/Auditory_illusion) of a third tone, in addition to the two pure-tones presented to each ear. The third sound is called a binaural beat, and in this example would have a perceived pitch correlating to a frequency of 10 Hz, that being the difference between the 530 Hz and 520 Hz pure tones presented to each ear.[[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)]
+
+Binaural-beat perception originates in the [inferior colliculus](https://en.wikipedia.org/wiki/Inferior_colliculus) of the [midbrain](https://en.wikipedia.org/wiki/Midbrain) and the [superior olivary complex](https://en.wikipedia.org/wiki/Superior_olivary_complex) of the [brainstem](https://en.wikipedia.org/wiki/Brainstem), where [auditory signals](https://en.wikipedia.org/wiki/Audio_signal_processing) from each [ear](https://en.wikipedia.org/wiki/Ear) are integrated and precipitate [electrical impulses](https://en.wikipedia.org/wiki/Action_potential) along [neural pathways](https://en.wikipedia.org/wiki/Neural_pathway) through the [reticular formation](https://en.wikipedia.org/wiki/Reticular_formation) up the midbrain to the [thalamus](https://en.wikipedia.org/wiki/Thalamus), [auditory cortex](https://en.wikipedia.org/wiki/Auditory_cortex), and other cortical regions.[[6]](https://en.wikipedia.org/wiki/Beat_(acoustics)#cite_note-oster-6)
+
+Some potential benefits of binaural beats therapy may include: reduced [stress](https://en.wikipedia.org/wiki/Psychological_stress), reduced [anxiety](https://en.wikipedia.org/wiki/Anxiety), increased focus, increased concentration, increased motivation, increased confidence, and deeper [meditation](https://en.wikipedia.org/wiki/Meditation).[[7]](https://en.wikipedia.org/wiki/Beat_(acoustics)#cite_note-MedicalNewsToday-7)

README.md

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+rules_scala_version="bd0c388125e12f4f173648fc4474f73160a5c628" # update this as needed
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+
+http_archive(
+    name = "bazel_skylib",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.0.2/bazel-skylib-1.0.2.tar.gz",
+        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.0.2/bazel-skylib-1.0.2.tar.gz",
+    ],
+    sha256 = "97e70364e9249702246c0e9444bccdc4b847bed1eb03c5a3ece4f83dfe6abc44",
+)
+load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
+bazel_skylib_workspace()
+
+http_archive(
+    name = "io_bazel_rules_scala",
+    strip_prefix = "rules_scala-%s" % rules_scala_version,
+    type = "zip",
+    url = "https://github.com/bazelbuild/rules_scala/archive/%s.zip" % rules_scala_version,
+)
+
+load("@io_bazel_rules_scala//scala:toolchains.bzl", "scala_register_toolchains")
+scala_register_toolchains()
+
+load("@io_bazel_rules_scala//scala:scala.bzl", "scala_repositories")
+scala_repositories()
+
+protobuf_version="09745575a923640154bcf307fba8aedff47f240a"
+protobuf_version_sha256="416212e14481cff8fd4849b1c1c1200a7f34808a54377e22d7447efdf54ad758"
+
+http_archive(
+    name = "com_google_protobuf",
+    url = "https://github.com/protocolbuffers/protobuf/archive/%s.tar.gz" % protobuf_version,
+    strip_prefix = "protobuf-%s" % protobuf_version,
+    sha256 = protobuf_version_sha256,
+)
+
+RULES_JVM_EXTERNAL_TAG = "3.0"
+RULES_JVM_EXTERNAL_SHA = "62133c125bf4109dfd9d2af64830208356ce4ef8b165a6ef15bbff7460b35c3a"
+
+http_archive(
+    name = "rules_jvm_external",
+    strip_prefix = "rules_jvm_external-%s" % RULES_JVM_EXTERNAL_TAG,
+    sha256 = RULES_JVM_EXTERNAL_SHA,
+    url = "https://github.com/bazelbuild/rules_jvm_external/archive/%s.zip" % RULES_JVM_EXTERNAL_TAG,
+)
+
+load("@rules_jvm_external//:defs.bzl", "maven_install")
+
+maven_install(
+    name = "maven",
+    artifacts = [
+        "com.github.scopt:scopt_2.11:4.0.0-RC2",
+        "junit:junit:4.12",
+        "com.novocode:junit-interface:0.11",
+        "org.scalaz:scalaz-core_2.11:7.2.7",
+        "org.scalatest:scalatest_2.11:2.2.4",
+        "org.apache.thrift:libthrift:0.9.3",
+        "org.eclipse.jetty:jetty-servlet:9.4.0.M0",
+        "org.eclipse.jetty:jetty-servlets:9.4.0.M0",
+        "org.openjdk.jmh:jmh-core:1.12",
+        "com.github.yannrichet:JMathPlot:1.0.1",
+        "org.auroboros:signal-z_2.11:0.1.0",
+        "org.clojars.sidec:jsyn:16.7.3",
+        "org.apache.commons:commons-math3:3.6",
+        "ch.qos.logback:logback-classic:1.1.7"
+    ],
+    repositories = [
+        "https://jcenter.bintray.com/",
+        "https://maven.google.com",
+        "https://repo1.maven.org/maven2",
+    ],
+    maven_install_json = "//:maven_install.json",
+)
+
+load("@maven//:defs.bzl", "pinned_maven_install")
+pinned_maven_install()
+
+git_repository(
+    name = "zachgrayio_scalaudio",
+    commit = "6d7dfabd71392a6b15ff3eea8b86945b12ad20f5",
+    remote = "http://github.com/zachgrayio/scalaudio.git",
+    shallow_since = "1578573315 +1100"
+)

WORKSPACE

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+load(
+    "@io_bazel_rules_scala//scala:scala.bzl",
+    "scala_binary",
+)
+
+scala_binary(
+    name = "app",
+    srcs = glob(["src/main/**/*.scala"]),
+    main_class = "io.zachgray.binauralBeats.cli.BinauralApp",
+    deps = [
+        "//engine:engine",
+        "@maven//:com_github_scopt_scopt_2_11",
+    ],
+    visibility = ["//visibility:public"]
+)

cli/BUILD

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+package io.zachgray.binauralBeats.cli
+
+import io.zachgray.binauralBeats.engine.{BinauralBeatsConfiguration, BinauralEngine}
+import scopt.OParser
+
+object BinauralApp extends App {
+  /**
+   * Main function - the entrypoint for the CLI application.
+   *
+   * Invokes the Binaural Engine with configuration values passed via command line flags.
+   * @param args
+   */
+  override def main(args: Array[String]): Unit = {
+    parseBinauralBeatsConfiguration(args) match {
+      case Some(config) => BinauralEngine.play(config)
+      case _ =>
+    }
+  }
+
+  /**
+   * Parses command line options and returns binaural beats configuration.
+   *
+   * @param args
+   * @return BinauralBeatConfiguration
+   */
+  private def parseBinauralBeatsConfiguration(args: Array[String]): Option[BinauralBeatsConfiguration] = {
+    val builder = OParser.builder[BinauralBeatsConfiguration]
+    val optionsParser: OParser[Unit, BinauralBeatsConfiguration] = {
+      import builder._
+      OParser.sequence(
+        programName("binaural"),
+
+        // presets
+
+        cmd("delta")
+          .action((_, c) => c.copy(binauralPitch = 3))
+          .text("Delta pattern preset; Binaural beats in the delta pattern operate at a frequency of 0.5–4 Hz with links to a dreamless sleep."),
+
+        cmd("theta")
+          .action((_, c) => c.copy(binauralPitch = 5.5))
+          .text("Theta pattern preset; Practitioners set binaural beats in the theta pattern to a frequency of 4–7 Hz. " +
+            "Theta patterns contribute to improved meditation, creativity, and sleep in the rapid eye movement (REM) phase."),
+
+        cmd("alpha")
+          .action((_, c) => c.copy(binauralPitch = 10))
+          .text("Alpha pattern preset; Binaural beats in the alpha pattern are at a frequency of 7–13 Hz and may encourage relaxation."),
+
+        cmd("beta")
+          .action((_, c) => c.copy(binauralPitch = 20))
+          .text("Beta pattern preset; Binaural beats in the beta pattern are at a frequency of 13–30 Hz. This frequency range " +
+            "may help promote concentration and alertness. However, it can also increase anxiety at the higher end of the range."),
+
+        cmd("gamma")
+          .action((_, c) => c.copy(binauralPitch = 40))
+          .text("Gamma pattern preset; This frequency pattern accounts for a range of 30–50 Hz. The study authors suggest that " +
+            "frequencies promote maintenance of arousal while a person is awake."),
+
+        // full customization
+
+        opt[Double]('p', "pitch")
+          .action((x, c) => c.copy(pitch = x))
+          .text("the frequency in Hz - an integer property"),
+
+        opt[Double]('b', "binaural_pitch")
+          .action((x, c) => c.copy(binauralPitch = x))
+          .text("the binaural tone's frequency - a decimal property"),
+
+        opt[Int]('d', "duration")
+          .action((x, c) => c.copy(duration = x))
+          .text("the duration for which to play the binaural audio - an integer property")
+      )
+    }
+    OParser.parse(optionsParser, args, BinauralBeatsConfiguration())
+  }
+}

cli/src/main/scala/io/zachgray/binauralBeats/cli/BinauralApp.scala

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+load(
+    "@io_bazel_rules_scala//scala:scala.bzl",
+    "scala_library",
+)
+
+scala_library(
+    name = "engine",
+    srcs = glob(["src/main/**/*.scala"]),
+    deps = [
+        "@zachgrayio_scalaudio//scalaudio-amp:scalaudio-amp",
+    ],
+    exports = [
+        "@zachgrayio_scalaudio//scalaudio-amp:scalaudio-amp",
+    ],
+    visibility = ["//visibility:public"]
+)

engine/BUILD

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+package io.zachgray.binauralBeats.engine
+
+case class BinauralBeatsConfiguration(pitch: Double = 300, binauralPitch: Double = 10, duration: Int = 30)