bemusic/bemuse

import _ from 'lodash'

export class NoteArea {
  constructor(notes, barLines) {
    this._notes = _.sortBy(notes, position)
    this._barLines = _(barLines).map('position').sortBy().value()
  }

  getVisibleNotes(lower, upper, headroom) {
    const out = []
    const notes = this._notes
    if (!headroom) headroom = 0
    for (let i = 0; i < notes.length; i++) {
      const note = notes[i]
      const visible = note.end
        ? !(note.position > upper || note.end.position < lower - headroom)
        : !(note.position > upper || note.position < lower - headroom)
      if (visible) {
        const entity = { note: note }
        if (!note.end) {
          entity.y = y(lower, upper, note.position)
        } else {
          const head = y(lower, upper, note.position)
          const tail = y(lower, upper, note.end.position)
          entity.y = Math.min(head, tail)
          entity.height = Math.abs(head - tail)
        }
        out.push(entity)
      }
    }
    return out
  }

  getVisibleBarLines(lower, upper, headroom) {
    if (!headroom) headroom = 0
    return this._barLines
      .filter((pos) => lower - headroom <= pos && pos <= upper)
      .map((pos) => ({ id: pos, y: y(lower, upper, pos) }))
  }
}

export default NoteArea

function y(lower, upper, pos) {
  return 1 - (pos - lower) / (upper - lower)
}

function position(event) {
  return event.position
}