\!/ KyuuKazami \!/

#!/bin/sh

# Set the shebang of installed python scripts to the system default python version.
# Determines the system default version by dereferencing /usr/bin/python.
# Only modifies shebangs that aren't already versioned, so that we don't break
#   scripts that were automatically versioned by setuptools, etc.

# Track the number of problems found with unversioned shebangs.
ERRORS_FOUND=0

fail() {
    echo "${0##*/} ERROR: $*"
    exit 1
}

# If using normal root, avoid changing anything.
if [ -z "$RPM_BUILD_ROOT" ] || [ "$RPM_BUILD_ROOT" = "/" ]; then
    exit 0
fi

# If we don't have a python interpreter, avoid changing anything.
python_symlink=${1:-/usr/bin/python}
if [ ! -x "${python_symlink}" ]; then
    exit 0
fi

# If we don't have the symlink's target, something is wrong.
default_python="$(readlink -ne ${python_symlink})"
if [ ! -x "${default_python}" ]; then
    fail "Target of /usr/bin/python does not exist or is not executable"
fi

default_python_version="$(echo "${default_python}" | grep -Eo '[0-9.]+$')"
if [ -z "${default_python_version}" ]; then
    fail "Unable to determine default python version from ${default_python}"
fi

# Remove dots from versions for consistent comparison.
compare_default_python_version="$(echo "${default_python_version}" | tr -d '.')"

# Find files with an unversioned python shebang in the first line.
for pythonfile in $(
    find "${RPM_BUILD_ROOT}" -type f \
        -exec awk '/^#![[:space:]]*\/(usr\/)?(local\/)?bin\/(env )?python($|[[:space:]])/ {print FILENAME} {nextfile}' \
        '{}' +
); do
    target_path="${pythonfile#${RPM_BUILD_ROOT}}"

    # For each found file, we see if we can tell its intended python version
    # by looking at the filename (foo-X.X) or path (/foo/pythonX.X/bar).
    path_python_version="$(echo "${target_path}" | grep -Eo '[0-9.]+$')"
    if [ -z "${path_python_version}" ]; then
        path_python_version="$(echo "${target_path}" | grep -Po '(?<=/python)[0-9.]+' | sort -u)"
    fi

    # Make sure we didn't get multiple version results from the path.
    versions_found="$(echo -e "${path_python_version}" | wc -l)"
    if [ "${versions_found}" -gt 1 ]; then
        ERRORS_FOUND="$(( ${ERRORS_FOUND} + 1 ))"
        echo "Found multiple version strings (${versions_found}: $(echo "${path_python_version}" | xargs))" \
             "in path ${target_path} with unversioned shebang." \
             "Version the python shebang in your spec file to avoid this."
        continue
    elif [ -n "${path_python_version}" ]; then
        # Remove dots from versions for consistent comparison.
        compare_path_python_version="$(echo "${path_python_version}" | tr -d '.')"

        # If we determined a python version from the path, and it doesn't match our
        # system python version, and the shebang was unversioned, then we fail
        # so the package can be fixed.
        if [ "${compare_path_python_version}" != "${compare_default_python_version}" ]; then
            ERRORS_FOUND="$(( ${ERRORS_FOUND} + 1 ))"
            echo "Unexpected version ${path_python_version} (wanted ${default_python_version})" \
                 "in path ${target_path} with unversioned shebang." \
                 "Version the python shebang in your spec file to avoid this."
            continue
        fi
    fi

    # Make sure we change the file, since the find/awk
    # should have only let in files we want to change.
    shebang_line_before="$(head -n1 ${pythonfile})"

    echo "${0##*/}: Rewriting shebang in \$RPM_BUILD_ROOT${target_path} to use ${default_python##*/}"
    sed -i -r -e \
        '1s,^#![[:space:]]*/(usr/)?(local/)?bin/(env )?python($|[[:space:]]),#!'${default_python}'\4,' \
        "${pythonfile}"

    shebang_line_after="$(head -n1 ${pythonfile})"
    if [ "${shebang_line_before}" = "${shebang_line_after}" ]; then
        ERRORS_FOUND="$(( ${ERRORS_FOUND} + 1 ))"
        echo "Expected to modify shebang but could not: ${pythonfile}"
        continue
    fi
done

if [ "${ERRORS_FOUND}" -ne 0 ]; then
    fail "Found ${ERRORS_FOUND} errors related to unversioned shebangs"
fi