function calculateRating (ratings) {
  const numberOfRatings = ratings.length
  const sumOfRatings = ratings.reduce(
    (accumulator, rating) => accumulator + rating.value,
    0
  )
  return numberOfRatings ? sumOfRatings / numberOfRatings : '-'
}
const TrainingArchive = props => (
  
    Training Archive
    
      {props.trainings.map(training => (
        
      ))}
    
 
)
const TrainingHint = props => (
  
    {props.training.date}
    {props.training.title}
   
)
const Training = props => (
  
    {props.title}
    
    
      Content
      
        {props.content
          .sort(block => block.sequence)
          .map(block => (
            
          ))}
      
)
const Youtube = props => {
  const { link, rest } = props
  const [crap, src] = props.link.match(/\?v=(.*)/)
  return (
    
  )
}
const Spotify = props => {
  const { link, rest } = props
  const [crap, src] = props.link.match(/track\/(.*)/)
  return (
    
  )
}
const Media = props => {
  if (props.link.includes('youtube.com')) {
    return 
  } else if (props.link.includes('spotify.com')) {
    return 
  } else {
    returnLink not recognized.
  }
}
const Block = props => (
  
    {props.title}
    
      Duration: 
      {props.duration}
    
    
      Variation: 
      {props.variation}
    
    
      Description: 
      {props.description}
    
    
      Format: 
      
        {props.format.name}{' '}
        
          [?]
        
      
    
    
      Tracks
      
        {props.tracks.map(track => (
          
        ))}
      
Exercises
      
        {props.exercises.map(exercise => (
          
        ))}
      
)
const Track = props => {
  return (
        Track {props.id}: {props.title} ({props.artist})
      
      
    
  )
}
const Exercise = props => {
  return (
    
      
        Exercise {props.id}: {props.name}
      
    
  )
}
class TrainingCreateForm extends React.Component {
  render () {
    return (
      
    )
  }
}
export { TrainingArchive }
export default Training