#!/bin/sh -eu

# Use /bin/sh rather than /bin/bash for portability. See discussion here:
# https://groups.google.com/forum/?nomobile=true#!topic/bazel-dev/4Ql_7eDcLC0
# We do lose the ability to set -o pipefail.

# TODO(#7843): integration tests for failure to find python / wrong version
# found / error while trying to print version

GENERAL_FAILURE_MESSAGE="Error: The default python toolchain \
(@bazel_tools//tools/python:autodetecting_toolchain) was unable to locate a \
suitable Python interpreter on the target platform at execution time. Please \
register an appropriate Python toolchain. See the documentation for \
py_runtime_pair here:
https://github.com/bazelbuild/bazel/blob/master/tools/python/toolchain.bzl."

# Try the "python%VERSION%" command name first, then fall back on "python".
PYTHON_BIN=`which python%VERSION% || echo ""`
USED_FALLBACK=0
if [ -z "${PYTHON_BIN:-}" ]; then
    PYTHON_BIN=`which python || echo ""`
    USED_FALLBACK=1
fi
if [ -z "${PYTHON_BIN:-}" ]; then
    echo "$GENERAL_FAILURE_MESSAGE"
    echo "Failure reason: Cannot locate 'python%VERSION%' or 'python' on the \
target platform's PATH, which is:
$PATH"
    exit 1
fi

# Verify that we grabbed an interpreter with the right version.
VERSION_STR=`"$PYTHON_BIN" -V 2>&1`
if ! echo "$VERSION_STR" | grep -q " %VERSION%\." ; then
    echo "$GENERAL_FAILURE_MESSAGE"
    echo "Failure reason: According to '$PYTHON_BIN -V', version is \
'$VERSION_STR', but we need version %VERSION%"
    exit 1
fi

exec "$PYTHON_BIN" "$@"