#!/bin/bash
set -e

echo '=== TRI (Terrain Ruggedness) GENERATION ==='
echo "Start: $(date)"

TMP='/tmp/tri_gen'
SRTM_DIR='/home/slin/enduro-trails/data/srtm'
TERRAIN_DIR='/home/slin/enduro-trails/data/terrain'
TRI_DIR="${TERRAIN_DIR}/tri"

rm -rf $TMP
mkdir -p $TMP $TRI_DIR

echo ''
echo '=== Step 1: Build VRT ==='
find $SRTM_DIR -name '*.hgt' > $TMP/file_list.txt
gdalbuildvrt -vrtnodata -32768 -overwrite -input_file_list $TMP/file_list.txt $TMP/srtm_all.vrt 2>&1
echo "VRT built ($(wc -l < $TMP/file_list.txt) files)"

echo ''
echo '=== Step 2: Generate TRI (Terrain Ruggedness Index) ==='
gdaldem TRI \
  $TMP/srtm_all.vrt \
  $TMP/tri_raw.tif \
  -of GTiff \
  -co COMPRESS=LZW \
  -co BIGTIFF=YES \
  -compute_edges 2>&1

echo 'TRI stats:'
gdalinfo -stats $TMP/tri_raw.tif 2>&1 | grep STATISTICS

echo ''
echo '=== Step 3: Color-relief (transparent where flat, yellow-red where rugged) ==='
# TRI values: 0=flat, 10=gentle, 30=moderate, 60+=steep
cat > $TMP/tri_color.txt << 'EOF'
nv    0    0    0    0
0     0    0    0    0
5     0    0    0    0
10    255  255  100  80
20    255  200  50   140
30    255  140  0    180
45    255  80   0    210
60    230  30   0    230
80    200  0    50   240
100   180  0   100   250
EOF

gdaldem color-relief \
  $TMP/tri_raw.tif \
  $TMP/tri_color.txt \
  $TMP/tri_colored.tif \
  -alpha \
  -of GTiff \
  -co COMPRESS=LZW \
  -co BIGTIFF=YES 2>&1

echo 'Colored TRI stats:'
gdalinfo -stats $TMP/tri_colored.tif 2>&1 | grep STATISTICS_MAX

echo ''
echo '=== Step 4: Generate tiles (zoom 5-12) ==='
gdal2tiles.py \
  --zoom=5-12 \
  --processes=4 \
  --tilesize=256 \
  --webviewer=none \
  $TMP/tri_colored.tif \
  ${TRI_DIR}/ 2>&1

echo ''
echo '=== Step 5: Stats ==='
for z in 5 6 7 8 9 10 11 12; do
  total=$(find ${TRI_DIR}/$z/ -name '*.png' 2>/dev/null | wc -l)
  nonempty=$(find ${TRI_DIR}/$z/ -name '*.png' -size +400c 2>/dev/null | wc -l)
  echo "  zoom $z: $total total, $nonempty non-empty"
done

echo ''
echo 'Total:'
find ${TRI_DIR} -name '*.png' | wc -l
du -sh ${TRI_DIR}

echo ''
echo '=== DONE ==='
echo "End: $(date)"