#!/bin/bash
#
# sync-newer-images — For each top-level image or video in SRC, copy it to
# DEST if it doesn't already exist anywhere under DEST.
# Works on Linux and macOS (bash 3.2+ compatible).

usage() {
    cat <<'EOF'
Usage: sync-newer-images [options] <destination> <source>

For each top-level image or video in source, copy it into destination if no
file with the same name exists anywhere under destination.

Options:
  -u, --update  If a matching file already exists under destination,
                copy over it only if the content differs (uses cmp).
  -h, --help    Show this help message and exit
EOF
    exit 0
}

update_mode=0

while [ $# -gt 0 ]; do
    case "$1" in
        -h|--help) usage ;;
        -u|--update) update_mode=1; shift ;;
        *) break ;;
    esac
done

if [ $# -lt 2 ]; then
    echo "Error: destination and source are required" >&2
    echo "Usage: sync-newer-images [options] <destination> <source>" >&2
    exit 1
fi

DEST="$1"
SRC="$2"

if [ ! -d "$DEST" ]; then
    echo "Error: destination '$DEST' is not a directory" >&2
    exit 1
fi

if [ ! -d "$SRC" ]; then
    echo "Error: source '$SRC' is not a directory" >&2
    exit 1
fi

# Build deduplicated, newline-separated list of all basenames under DEST.
basenames=$(find "$DEST" -type f 2>/dev/null | sed 's|.*/||' | sort -u)

copied=0

for srcfile in "$SRC"/*; do
    [ -f "$srcfile" ] || continue

    ext="${srcfile##*.}"
    case "$(echo "$ext" | tr '[:upper:]' '[:lower:]')" in
        jpg|jpeg|png|gif|heic|webp|bmp|tiff|tif) ;;
        mov|mp4|m4v|avi|mkv|3gp) ;;
        *) continue ;;
    esac

    filename="${srcfile##*/}"

    if ! printf '%s\n' "$basenames" | grep -qxF "$filename"; then
        cp -v "$srcfile" "$DEST/"
        copied=$((copied + 1))
    elif [ "$update_mode" -eq 1 ]; then
        destfile=$(find "$DEST" -type f -name "$filename" 2>/dev/null | head -1)
        if [ -n "$destfile" ] && ! cmp -s "$srcfile" "$destfile"; then
            cp -v "$srcfile" "$destfile"
            copied=$((copied + 1))
        fi
    fi
done

echo "Copied ${copied} image(s)/video(s) from ${SRC} into ${DEST}"