var draw = (function(){

  var last_point = [0,0]
  
  function down (e, lex, point) {
    erasing = (e.which == "3" || e.ctrlKey)
    if (e.shiftKey) {
      line (lex, last_point, point, erasing)
    }
    else {
      stamp (canvas, brush, point[0], point[1], erasing)
    }
    last_point[0] = point[0]
    last_point[1] = point[1]
  }
  
  function move (e, lex, point) {
    line(lex, last_point, point, erasing)
    last_point[0] = point[0]
    last_point[1] = point[1]
  }
  
  function point (lex, x, y, erasing) {
    stamp (canvas, brush, x, y, erasing)
  }

  function line (lex, a, b, erasing) {
    var len = dist(a[0], a[1], b[0], b[1])
    var bw = 1
    var x, y, i;
    for (var i = 0; i <= len; i += bw) {
      x = lerp(i / len, a[0], b[0])
      y = lerp(i / len, a[1], b[1])
      stamp (canvas, brush, x, y, erasing)
    }
  }

  function stamp (canvas, brush, x, y, erasing) {
    hh = brush.w/2|0
    brush.forEach(function(lex, s, t){
      s = round( s + x-hh )
      t = round( t + y-hh )
      if (lex.opacity > 0 && s >= 0 && s < canvas.w && t >= 0 && t < canvas.h) {
        if (erasing) {
          canvas.aa[t][s].erase(lex)
        }
        else {
          canvas.aa[t][s].clone(lex)
        }
      }
    })
  }
  
  function fill (lex, x, y) {
		var q = [ [x,y] ]
		var target = canvas.aa[y][x].copy()
		var n, w = 0, e = 0, j = 0
		var kk = 0
		// gets into a weird infinite loop if we don't break here.. :\
		if (target.eq(lex)) { return }
		LOOP: while (q.length) {
			n = q.shift()
			if (canvas.aa[n[1]][n[0]].ne(target)) {
				continue LOOP
			}
			w = e = n[0]
			j = n[1]
			WEST: while (w > 0) {
				if (canvas.aa[j][w-1].eq(target)) {
					w = w-1
				}
				else {
					break WEST
				}
			}
			EAST: while (e < canvas.w-1) {
				if (canvas.aa[j][e+1].eq(target)) {
					e = e+1
				}
				else {
					break EAST
				}
			}
			for (var i = w; i <= e; i++) {
				canvas.aa[j][i].clone(lex)
				if (j > 0 && canvas.aa[j-1][i].eq(target)) {
					q.push([ i, j-1 ])
				}
				if (j < canvas.h-1 && canvas.aa[j+1][i].eq(target)) {
					q.push([ i, j+1 ])
				}
			}
		}
  }

  var draw = {}
  draw.down = down
  draw.move = move
  draw.stamp = stamp
  draw.line = line
  draw.point = point
  draw.fill = fill
  return draw

})()