melrōse musical expression player

package core import ( "fmt" "strconv" "strings" ) var allowedTabnoteNames = "EADGeadg=" type tabnoteSTM struct { fraction float32 dotted bool name string fret int velocity string } func newTabNoteSTM() *tabnoteSTM { s := new(tabnoteSTM) s.reset() return s } func (s *tabnoteSTM) reset() { s.dotted = false s.fraction = 0.25 s.name = "" s.fret = 0 s.velocity = "" } func (s *tabnoteSTM) accept(lit string) error { if len(lit) == 0 { return nil } if strings.HasSuffix(lit, ".") { // without dot if err := s.accept(lit[0 : len(lit)-1]); err != nil { return err } lit = "." // proceed } if len(s.name) == 0 { if strings.ContainsAny(lit, allowedTabnoteNames) { if len(lit) != 1 { return fmt.Errorf("invalid note name, must be one character, got:%s", lit) } s.name = strings.ToUpper(lit) return nil } // fraction or dotted if lit == "." { if s.dotted { return fmt.Errorf("note duration already known, got:%s", lit) } s.dotted = true return nil } var f float32 switch lit { case "16": f = 0.0625 case "8": f = 0.125 case "4": f = 0.25 case "2": f = 0.5 case "1": f = 1 default: return fmt.Errorf("invalid note fraction or illegal note name, got:%s", lit) } if s.fraction != 0.25 { return fmt.Errorf("note fraction already known, got:%s", lit) } s.fraction = f return nil } else { // name is set if strings.ContainsAny(lit, allowedNoteNames) { return fmt.Errorf("note name already known, got:%s", lit) } // velocity if strings.ContainsAny(lit, "-o+") { s.velocity += lit return nil } // fret if i, err := strconv.Atoi(lit); err != nil { return fmt.Errorf("invalid note fret, unexpected:%s", lit) } else { s.fret = i } } return nil } func (s *tabnoteSTM) currentNote() (TabNote, error) { vel := Normal if len(s.velocity) > 0 { vel = ParseVelocity(s.velocity) if vel == -1 { return TabNote{}, fmt.Errorf("invalid note dynamic, unexpected:%s", s.velocity) } } return TabNote{ Name: s.name, Fret: s.fret, Velocity: vel, fraction: s.fraction, Dotted: s.dotted, }, nil } func (s *tabnoteSTM) note() (TabNote, error) { c, err := s.currentNote() if err != nil { return TabNote{}, err } return c, nil }