composite

/*
 * Author: Rodrigo E. Principe
 * License: Apache 2.0
 * email: fitoprincipe82@gmail.com

Composite Methods
*/

var tools = require('users/fitoprincipe/geetools:tools')

var euclidean_distance = function(i, i2) {
  var bandsi = i.bandNames()
  var bandsi2 = i2.bandNames()
  
  var proxy = tools.image.fromList(bandsi, 0)
  i = proxy.where(i.gt(0), i)
  i2 = proxy.where(i2.gt(0), i2)
  
  var a = i.subtract(i2)
  var b = a.pow(2)
  var c = b.reduce('sum')
  var d = c.sqrt()
  
  return d.rename('distance')
}

var sum_distance = function(i, rest) {
  var accum = ee.Image(0).rename('sumdist')
  return ee.Image(rest.iterate(function(im, ini) {
    ini = ee.Image(ini)
    im = ee.Image(im)
    var dist = ee.Image(euclidean_distance(i, im)).rename('sumdist')
    return ini.add(dist)
  }, accum))
}

var medoid = function(collection, bands) {
  
  //collection = collection.map(function(im){return im.unmask()})
  
  var first_image = ee.Image(collection.first())
  var ibands = first_image.bandNames()
  
  bands = bands || ibands
  //collection = collection.select(bands)
  
  var enumerated = tools.imageCollection.enumerateProperty(collection)
  var collist = enumerated.toList(enumerated.size())
  
  var imlist = ee.List(collist.map(function(im){
    im = ee.Image(im)
    var n = ee.Number(im.get('enumeration'))
    var filtered = tools.list.removeIndex(collist, n)
                        .map(function(im){
                          im = ee.Image(im)
                          return im.select(bands)
                        })
    var dist = sum_distance(
      im.select(bands), 
      filtered
    ).multiply(-1)
    return im.addBands(dist)
  }))
  
  var medcol = ee.ImageCollection.fromImages(imlist)
  return medcol.qualityMosaic('sumdist')
}

exports.medoid = medoid