#!/bin/zsh

function usage() {
  NAME=$(basename "$0")
  echo "Usage: ${NAME} <source-icon> <output-directory>"
}

IN_FILE="$1"
OUT_DIR="$2"

if [[ ! -r "$IN_FILE" ]]; then
  echo "Missing source icon, or file not found: $IN_FILE"
  usage
  exit 1
fi
if [[ ! -d "$OUT_DIR" ]]; then
  echo "Missing output directory, or directory not found: $OUT_DIR"
  usage
  exit 2
fi

FILENAME=$(basename "$IN_FILE")

echo "* Generating App Store marketing icon at 1024x1024 px"
APPSTORE_FILE="${OUT_DIR}/${FILENAME%.png}_marketing_1024.png"
echo "> convert '${IN_FILE}' -scale 1024x1024 '${APPSTORE_FILE}'"
gm convert "$IN_FILE" -scale 1024x1024 "$APPSTORE_FILE"

for SIZE in 20 29 40 60; do
  PREFIX="${FILENAME%.png}_iPhone_$SIZE"
  echo "* Generating iPhone icons at $SIZE points with filename prefix $PREFIX"
  S=$((2 * SIZE))
  gm convert "$IN_FILE" -scale ${S}x${S} "$OUT_DIR/$PREFIX@2x.png"
  S=$((3 * SIZE))
  gm convert "$IN_FILE" -scale ${S}x${S} "$OUT_DIR/$PREFIX@3x.png"
done

for SIZE in 20 29 40 76 83.5; do
  PREFIX="${FILENAME%.png}_iPad_$SIZE"
  echo "* Generating iPad icons at $SIZE points with filename prefix $PREFIX"
  S=$SIZE
  gm convert "$IN_FILE" -scale ${S}x${S} "$OUT_DIR/$PREFIX.png"
  S=$((2 * SIZE))
  gm convert "$IN_FILE" -scale ${S}x${S} "$OUT_DIR/$PREFIX@2x.png"
done

for SIZE in 16 32 128 256 512; do
  PREFIX="${FILENAME%.png}_Mac_$SIZE"
  echo "* Generating Mac icons at $SIZE points with filename prefix $PREFIX"
  gm convert "$IN_FILE" -scale ${SIZE}x${SIZE} "$OUT_DIR/$PREFIX.png"
  S=$((2 * SIZE))
  gm convert "$IN_FILE" -scale ${S}x${S} "$OUT_DIR/$PREFIX@2x.png"
done