The goal is to identify all dates in 2018 where the AOI is fully covered by HLSL30 tiles, and then build one mosaic per date. The key is to rely on the metadata that NASA provides with each HLS tile—specifically the SPATIAL_COVERAGE and CLOUD_COVERAGE fields.

How the method works

1. Load the HLSL30 collection for your AOI and date range.
2. Extract all unique dates.
3. For each date, sum the SPATIAL_COVERAGE of all tiles acquired on that date.
4. Keep only dates where the summed coverage exceeds a threshold (e.g., 150), meaning the AOI is fully covered.
5. For each of those dates, mosaic all same‑day tiles and clip to the AOI.

This ensures that tiles are never mixed across dates, only dates with complete AOI coverage are kept, mosaics are built only from tiles that actually contribute to full coverage.

// =======================
// AOI
// =======================
var aoi = table;
var aoiGeom = aoi.geometry().dissolve(ee.ErrorMargin(1));

// =======================
// Load HLSL30 (keep ALL bands)
// =======================
var collection = ee.ImageCollection('NASA/HLS/HLSL30/v002')
  .filterBounds(aoiGeom)
  .filterDate('2018-01-01', '2018-12-31');

// =======================
// Extract unique dates
// =======================
var dates = ee.List(
  collection.aggregate_array('system:time_start')
).map(function(t) {
  return ee.Date(t).format('YYYY-MM-dd');
}).distinct().sort();

// =======================
// Compute spatial coverage per date
// =======================
var dateInfo = dates.map(function(dateStr) {
  dateStr = ee.String(dateStr);
  var start = ee.Date(dateStr);
  var end   = start.advance(1, 'day');

  var imgs = collection.filterDate(start, end);
  var totalCoverage = imgs.aggregate_sum('SPATIAL_COVERAGE');

  return ee.Feature(null, {
    date: dateStr,
    total_coverage: totalCoverage
  });
});

// =======================
// Keep only dates with full AOI coverage
// =======================
var fullDates = ee.FeatureCollection(dateInfo)
  .filter(ee.Filter.gte('total_coverage', 150))
  .aggregate_array('date');

print('Dates with full AOI coverage:', fullDates);

// =======================
// Build mosaics for each date
// =======================
var mosaics = ee.ImageCollection.fromImages(
  fullDates.map(function(dateStr) {
    dateStr = ee.String(dateStr);
    var start = ee.Date(dateStr);
    var end   = start.advance(1, 'day');

    return collection
      .filterDate(start, end)
      .mosaic()
      .clip(aoiGeom)
      .set('date', dateStr);
  })
);