From 1e3af49d8f31236ba1a506f6d33d0323f94f1cad Mon Sep 17 00:00:00 2001
From: Ahmed Kamal <ahmed_kamal_abulinain@yahoo.com>
Date: Wed, 11 Oct 2023 01:39:04 +1100
Subject: [PATCH] feat: add `sliceAudio` method (#92)

---
 .gitignore     |  2 ++
 README.md      | 12 ++++++++++++
 package.json   |  4 ++--
 src/crunker.ts | 38 ++++++++++++++++++++++++++++++++++++++
 test/test.js   |  4 ++++
 5 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/.gitignore b/.gitignore
index b967f4a..59e47f1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,3 +13,5 @@ test/*.bundle.js
 !.yarn/releases
 !.yarn/sdks
 !.yarn/versions
+
+.idea
diff --git a/README.md b/README.md
index 65ab167..5a16223 100644
--- a/README.md
+++ b/README.md
@@ -118,6 +118,18 @@ Concatenate two or more audio buffers in the order specified.\
 Pad the audio with silence, at the beginning, the end, or any specified points through the audio.\
 **Returns:** a single `AudioBuffer` object.
 
+## crunker.sliceAudio(buffer, start, end, fadeIn, fadeOut);
+
+Slice the audio to the specified range, removing any content outside the range. Optionally add a fade-in at the start and a fade-out at the end to avoid audible clicks.
+
+- **buffer:** The audio buffer to be trimmed.
+- **start:** The starting second from where the audio should begin.
+- **end:** The ending second where the audio should be trimmed.
+- **fadeIn:** (Optional) Number of seconds for the fade-in effect at the beginning. Default is `0`.
+- **fadeOut:** (Optional) Number of seconds for the fade-out effect at the end. Default is `0`.
+
+**Returns:** a single `AudioBuffer` object.
+
 ## crunker.export(buffer, type);
 
 Export an audio buffers with MIME type option.\
diff --git a/package.json b/package.json
index 5b99cc4..d25fcbf 100644
--- a/package.json
+++ b/package.json
@@ -38,9 +38,9 @@
   "author": "Jack Edgson",
   "license": "MIT",
   "files": [
-    "LICENSE"
+    "LICENSE",
     "README.md",
-    "dist",
+    "dist"
   ],
   "bugs": {
     "url": "https://github.com/jaggad/crunker/issues"
diff --git a/src/crunker.ts b/src/crunker.ts
index a0f9209..1303dd7 100644
--- a/src/crunker.ts
+++ b/src/crunker.ts
@@ -181,6 +181,44 @@ export default class Crunker {
     return updatedBuffer;
   }
 
+  /**
+   * Slices an AudioBuffer from the specified start time to the end time, with optional fade in and out.
+   *
+   * @param buffer AudioBuffer to slice
+   * @param start Start time (in seconds)
+   * @param end End time (in seconds)
+   * @param fadeIn Fade in duration (in seconds, default is 0)
+   * @param fadeOut Fade out duration (in seconds, default is 0)
+   */
+  sliceAudio(buffer: AudioBuffer, start: number, end: number, fadeIn: number = 0, fadeOut: number = 0): AudioBuffer {
+    if (start >= end) throw new Error('Crunker: "start" time should be less than "end" time in sliceAudio method');
+
+    const length = Math.round((end - start) * this._sampleRate);
+    const offset = Math.round(start * this._sampleRate);
+    const newBuffer = this._context.createBuffer(buffer.numberOfChannels, length, this._sampleRate);
+
+    for (let channel = 0; channel < buffer.numberOfChannels; channel++) {
+      const inputData = buffer.getChannelData(channel);
+      const outputData = newBuffer.getChannelData(channel);
+
+      for (let i = 0; i < length; i++) {
+        outputData[i] = inputData[offset + i];
+
+        // Apply fade in
+        if (i < fadeIn * this._sampleRate) {
+          outputData[i] *= i / (fadeIn * this._sampleRate);
+        }
+
+        // Apply fade out
+        if (i > length - fadeOut * this._sampleRate) {
+          outputData[i] *= (length - i) / (fadeOut * this._sampleRate);
+        }
+      }
+    }
+
+    return newBuffer;
+  }
+
   /**
    * Plays the provided AudioBuffer in an AudioBufferSourceNode.
    */
diff --git a/test/test.js b/test/test.js
index 0a0a1b3..0a86787 100644
--- a/test/test.js
+++ b/test/test.js
@@ -49,6 +49,10 @@ describe('Crunker', () => {
     expect(audio.concatAudio(buffers).duration.toFixed(2)).to.equal('16.30');
   });
 
+  it('slices a buffer correctly', () => {
+    expect(audio.sliceAudio(buffers[0], 0, 1, 0.1, 0.1).duration.toFixed(2)).to.equal('1.00');
+  });
+
   it('exports an object', () => {
     const output = audio.export(buffers[0]);
     expect(output).to.not.equal(null);