Support parsing for m3u and m3u8 files

README.md

@@ -32,6 +32,7 @@ and [dimensions,](https://github.com/sstephenson/dimensions) borrowing from them
 * DOCX, PPTX, XLSX
 * OGG
 * MPEG, MPG
+* M3U
 
 ...with [more](https://github.com/WeTransfer/format_parser/issues?q=is%3Aissue+is%3Aopen+label%3Aformats) on the way!
 
@@ -194,6 +195,9 @@ Unless specified otherwise in this section the fixture files are MIT licensed an
   manipulated using the [https://github.com/recurser/exif-orientation-examples](exif-orientation-examples)
   script.
 
+### M3U
+- The M3U fixture files were created by one of the project maintainers
+
 ### .key
 - The `keynote_recognized_as_jpeg.key` file was created by the project maintainers
 

lib/format_parser.rb

@@ -19,6 +19,7 @@ module FormatParser
   require_relative 'io_constraint'
   require_relative 'care'
   require_relative 'active_storage/blob_analyzer'
+  require_relative 'text'
 
   # Define Measurometer in the internal namespace as well
   # so that we stay compatible for the applications that use it

lib/parsers/m3u_parser.rb

@@ -0,0 +1,21 @@
+class FormatParser::M3UParser
+  include FormatParser::IOUtils
+
+  HEADER = '#EXTM3U'
+
+  def likely_match?(filename)
+    filename =~ /\.m3u8?$/i
+  end
+
+  def call(io)
+    io = FormatParser::IOConstraint.new(io)
+
+    header = safe_read(io, 7)
+    return unless HEADER.eql?(header)
+
+    FormatParser::Text.new(
+      format: :m3u
+    )
+  end
+  FormatParser.register_parser new, natures: :text, formats: :m3u
+end

lib/text.rb

@@ -0,0 +1,18 @@
+module FormatParser
+  class Text
+    include FormatParser::AttributesJSON
+
+    NATURE = :text
+
+    attr_accessor :format
+
+    # Only permits assignments via defined accessors
+    def initialize(**attributes)
+      attributes.map { |(k, v)| public_send("#{k}=", v) }
+    end
+
+    def nature
+      NATURE
+    end
+  end
+end

spec/fixtures/M3U/plain_text.m3u

@@ -0,0 +1,2 @@
+C:\My Music\Artist\Year\1.Test.mp3
+C:\My Music\Artist\Year\10.Test.mp3

spec/fixtures/M3U/sample.m3u

@@ -0,0 +1,5 @@
+#EXTM3U
+#EXTINF:170,Artist - 1
+C:\My Music\Artist\Year\1.Test.mp3
+#EXTINF:3,Artist - 10
+C:\My Music\Artist\Year\10.Test.mp3

spec/fixtures/M3U/sample.m3u8

@@ -0,0 +1,5 @@
+#EXTM3U
+#EXTINF:170,Artist - 1
+C:\My Music\Artist\Year\1.Test.mp3
+#EXTINF:3,Artist - 10
+C:\My Music\Artist\Year\10.Test.mp3

spec/parsers/m3u_parser_spec.rb

@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe FormatParser::M3UParser do
+  let(:parsed_m3u) do
+    subject.call(
+      File.open(
+        Pathname.new(fixtures_dir).join('M3U').join(m3u_file),
+        'rb'
+      )
+    )
+  end
+
+  describe 'an m3u file with missing header' do
+    let(:m3u_file) { 'plain_text.m3u' }
+
+    it 'does not parse the file successfully' do
+      expect(parsed_m3u).to be_nil
+    end
+  end
+
+  describe 'an m3u file with valid header' do
+    let(:m3u_file) { 'sample.m3u' }
+
+    it 'parses the file successfully' do
+      expect(parsed_m3u).not_to be_nil
+      expect(parsed_m3u.nature).to eq(:text)
+      expect(parsed_m3u.format).to eq(:m3u)
+    end
+  end
+
+  describe 'an m3u8 file with valid header' do
+    let(:m3u_file) { 'sample.m3u8' }
+
+    it 'parses the file successfully' do
+      expect(parsed_m3u).not_to be_nil
+      expect(parsed_m3u.nature).to eq(:text)
+      expect(parsed_m3u.format).to eq(:m3u)
+    end
+  end
+end