power chords and chord parser added

Author: er-davo

chords.go

@@ -1,5 +1,28 @@
 package guitar
 
+import (
+	"strconv"
+	"strings"
+)
+
+func ParseChord(chordTab string) []NotePositioner {
+	notes := strings.Split(chordTab, " ")
+	chord := []NotePositioner{}
+
+	for i, note := range notes {
+		num, err := strconv.Atoi(note)
+		if err != nil {
+			if note != "-" {
+				return []NotePositioner{}
+			}
+			continue
+		}
+		chord = append(chord, Note{Fret: num, String: i})
+	}
+
+	return chord
+}
+
 const (
 	// A
 	//   e|0
@@ -295,6 +318,95 @@ const (
 	//   A|0
 	//   E|3
 	Gmaj7
+
+	// C5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|5
+	//   A|3
+	//   E|-
+	PowerC5
+	// D5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|7
+	//   A|5
+	//   E|-
+	PowerD5
+	// Db5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|6
+	//   A|4
+	//   E|-
+	PowerDb5
+	// Eb5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|3
+	//   A|1
+	//   E|-
+	PowerEb5
+	// E5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|-
+	//   A|2
+	//   E|0
+	PowerE5
+	// F5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|-
+	//   A|3
+	//   E|1
+	PowerF5
+	// Gb5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|-
+	//   A|4
+	//   E|2
+	PowerGb5
+	// G5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|-
+	//   A|5
+	//   E|3
+	PowerG5
+	// A5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|-
+	//   A|7
+	//   E|5
+	PowerA5
+	// Bb5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|3
+	//   A|1
+	//   E|-
+	PowerBb5
+	// B5
+	//   e|-
+	//   B|-
+	//   G|-
+	//   D|4
+	//   A|2
+	//   E|-
+	PowerB5
 )
 
 func GetChord(chordNum int) []NotePositioner {
@@ -601,6 +713,61 @@ func GetChord(chordNum int) []NotePositioner {
 			Note{Fret: 0, String: 4},
 			Note{Fret: 3, String: 5},
 		}
+	case PowerC5:
+		return []NotePositioner{
+			Note{Fret: 5, String: 3},
+			Note{Fret: 3, String: 4},
+		}
+	case PowerD5:
+		return []NotePositioner{
+			Note{Fret: 7, String: 3},
+			Note{Fret: 5, String: 4},
+		}
+	case PowerDb5:
+		return []NotePositioner{
+			Note{Fret: 6, String: 3},
+			Note{Fret: 4, String: 4},
+		}
+	case PowerEb5:
+		return []NotePositioner{
+			Note{Fret: 3, String: 3},
+			Note{Fret: 1, String: 4},
+		}
+	case PowerE5:
+		return []NotePositioner{
+			Note{Fret: 2, String: 4},
+			Note{Fret: 0, String: 5},
+		}
+	case PowerF5:
+		return []NotePositioner{
+			Note{Fret: 3, String: 4},
+			Note{Fret: 1, String: 5},
+		}
+	case PowerGb5:
+		return []NotePositioner{
+			Note{Fret: 4, String: 4},
+			Note{Fret: 2, String: 5},
+		}
+	case PowerG5:
+		return []NotePositioner{
+			Note{Fret: 5, String: 4},
+			Note{Fret: 3, String: 5},
+		}
+	case PowerA5:
+		return []NotePositioner{
+			Note{Fret: 7, String: 4},
+			Note{Fret: 5, String: 5},
+		}
+	case PowerBb5:
+		return []NotePositioner{
+			Note{Fret: 3, String: 3},
+			Note{Fret: 1, String: 4},
+		}
+	case PowerB5:
+		return []NotePositioner{
+			Note{Fret: 4, String: 3},
+			Note{Fret: 2, String: 4},
+		}
 	default:
 		return []NotePositioner{}
 	}

chords_test.go

@@ -0,0 +1,73 @@
+package guitar
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseChord(t *testing.T) {
+	testCases := []struct {
+		name        string
+		chordTab    string
+		expected    []NotePositioner
+		expectError bool
+	}{
+		{
+			name:     "Standard A chord",
+			chordTab: "0 2 2 2 0 -",
+			expected: []NotePositioner{
+				Note{Fret: 0, String: 0},
+				Note{Fret: 2, String: 1},
+				Note{Fret: 2, String: 2},
+				Note{Fret: 2, String: 3},
+				Note{Fret: 0, String: 4},
+			},
+		},
+		{
+			name:     "Power chord E5",
+			chordTab: "- - - 2 0 -",
+			expected: []NotePositioner{
+				Note{Fret: 2, String: 3},
+				Note{Fret: 0, String: 4},
+			},
+		},
+		{
+			name:     "Chord with skipped strings (mixed)",
+			chordTab: "3 - 0 1 - 3",
+			expected: []NotePositioner{
+				Note{Fret: 3, String: 0},
+				Note{Fret: 0, String: 2},
+				Note{Fret: 1, String: 3},
+				Note{Fret: 3, String: 5},
+			},
+		},
+		{
+			name:        "Invalid character (letters)",
+			chordTab:    "a b c 1 2 3",
+			expectError: true,
+		},
+		{
+			name:        "Empty input",
+			chordTab:    "",
+			expectError: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			result := ParseChord(tc.chordTab)
+
+			if tc.expectError {
+				assert.Empty(t, result, "Expected error but got notes")
+				return
+			}
+
+			assert.Equal(t, len(tc.expected), len(result), "Number of parsed notes mismatch")
+			for i, note := range tc.expected {
+				assert.Equal(t, note.FretPosition(), result[i].FretPosition(), "Fret mismatch")
+				assert.Equal(t, note.StringPosition(), result[i].StringPosition(), "String mismatch")
+			}
+		})
+	}
+}