#!/bin/bash
set -e

echo '=== DOWNLOAD MISSING SRTM FILES (E041-E046, N54-N56) ==='
echo "Start: $(date)"

SRTM_DIR='/home/slin/enduro-trails/data/srtm'
cd $SRTM_DIR

# Missing tiles for the gap between Vladimir (E040) and Cheboksary (E047)
# Latitudes N54-N56 (main coverage area)
TILES="N54E041 N54E046 N55E041 N55E042 N55E043 N55E044 N55E045 N55E046 N56E041 N56E042 N56E043 N56E044 N56E045 N56E046"

# Also fill N53 gap
TILES="$TILES N53E046 N53E047"

# SRTM v4.1 from CGIAR (free, no auth needed)
# URL pattern: https://srtm.csi.cgiar.org/wp-content/uploads/files/srtm_5x5/TIFF/
# Alternative: NASA EarthData (needs auth) or viewfinderpanoramas.org

# Use viewfinderpanoramas.org - direct HGT downloads
BASE_URL="https://viewfinderpanoramas.org/dem3"

count=0
for tile in $TILES; do
  if [ -f "${tile}.hgt" ]; then
    echo "SKIP: ${tile}.hgt already exists"
    continue
  fi
  
  # Extract lat letter (N/S) and first 2 digits for directory
  lat_letter=${tile:0:1}
  lat_num=${tile:1:2}
  
  # viewfinderpanoramas uses zip files grouped by latitude band
  # Try direct NASA SRTM mirror instead
  # https://e4ftl01.cr.usgs.gov/MEASURES/SRTMGL1.003/2000.02.11/
  # Needs .SRTMGL1.hgt.zip format - requires auth
  
  # Use OpenTopography or direct SRTM mirror
  # Simplest: use elevation-tiles from AWS (no auth)
  echo "Downloading ${tile}..."
  
  # Try USGS SRTM mirror (no auth for SRTM3/1-arc-second)
  wget -q "https://firmware.ardupilot.org/SRTM/ap_srtm3/${tile}.hgt.zip" -O "/tmp/${tile}.hgt.zip" 2>/dev/null
  if [ $? -eq 0 ] && [ -s "/tmp/${tile}.hgt.zip" ]; then
    unzip -o -q "/tmp/${tile}.hgt.zip" -d $SRTM_DIR/
    rm -f "/tmp/${tile}.hgt.zip"
    echo "  OK: ${tile}.hgt ($(du -h ${tile}.hgt | cut -f1))"
    count=$((count + 1))
  else
    echo "  FAIL: ${tile} not available from ardupilot mirror"
    # Try alternative
    wget -q "http://viewfinderpanoramas.org/dem3/${lat_letter}${lat_num}/${tile}.hgt.zip" -O "/tmp/${tile}.hgt.zip" 2>/dev/null
    if [ $? -eq 0 ] && [ -s "/tmp/${tile}.hgt.zip" ]; then
      unzip -o -q "/tmp/${tile}.hgt.zip" -d $SRTM_DIR/
      rm -f "/tmp/${tile}.hgt.zip"
      echo "  OK (viewfinder): ${tile}.hgt"
      count=$((count + 1))
    else
      echo "  FAIL: ${tile} not found"
    fi
  fi
done

echo ""
echo "Downloaded: $count new files"
echo "Total HGT files: $(ls $SRTM_DIR/*.hgt | wc -l)"
echo "End: $(date)"