#!/usr/bin/env bash

# Copyright 2024 The Kubernetes Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# This script checks the coding style for the Go language files using
# golangci-lint. Which checks are enabled depends on command line flags. The
# default is a minimal set of checks that all existing code passes without
# issues.

usage () {
  cat <<EOF >&2
Usage: $0 [-r <revision>] [directory ...]"
   -t <revision>: Report changes in code up to and including this revision.
                  Default is the current working tree instead of a revision.
   -r <revision>: Report change in code added since this revision. Default is
                  the common base of origin/master and HEAD.
   [directory]:   Check one or more specific directory instead of everything.
EOF
  exit 1
}

set -o errexit
set -o nounset
set -o pipefail

KUBE_ROOT=$(dirname "${BASH_SOURCE[0]}")/..
source "${KUBE_ROOT}/hack/lib/init.sh"

base=
target=
while getopts "r:t:" o; do
    case "${o}" in
        r)
            base="${OPTARG}"
            if [ ! "$base" ]; then
                echo "ERROR: -${o} needs a non-empty parameter" >&2
                echo >&2
                usage
            fi
            ;;
       t)
            target="${OPTARG}"
            if [ ! "$target" ]; then
                echo "ERROR: -${o} needs a non-empty parameter" >&2
                echo >&2
                usage
            fi
            ;;
        *)
            usage
            ;;
    esac
done
shift $((OPTIND - 1))

# Check specific directory or everything.
targets=("$@")
if [ ${#targets[@]} -eq 0 ]; then
    # This lists all entries in the go.work file as absolute directory paths.
    kube::util::read-array targets < <(go list -f '{{.Dir}}' -m)
fi

# Sanitize paths:
# - We need relative paths because we will invoke apidiff in
#   different work trees.
# - Must start with a dot.
for (( i=0; i<${#targets[@]}; i++ )); do
    d="${targets[i]}"
    d=$(realpath -s --relative-to="$(pwd)" "${d}")
    if [ "${d}" != "." ]; then
        # sub-directories have to have a leading dot.
        d="./${d}"
    fi
    targets[i]="${d}"
done

# Must be a something that git can resolve to a commit.
# "git rev-parse --verify" checks that and prints a detailed
# error.
if [ -n "${target}" ]; then
    target="$(git rev-parse --verify "${target}")"
fi

# Determine defaults.
if [ -z "${base}" ]; then
    if ! base="$(git merge-base origin/master "${target:-HEAD}")"; then
        echo >&2 "Could not determine default base revision. -r must be used explicitly."
        exit 1
    fi
fi
base="$(git rev-parse --verify "${base}")"

# Give some information about what's happening. Failures from "git describe" are ignored
# silently, that's optional information.
describe () {
    local rev="$1"
    local descr
    echo -n "$rev"
    if descr=$(git describe --tags "${rev}" 2>/dev/null); then
        echo -n " (= ${descr})"
    fi
    echo
}
echo "Checking $(if [ -n "${target}" ]; then describe "${target}"; else echo "current working tree"; fi) for API changes since $(describe "${base}")."

kube::golang::setup_env
kube::util::ensure-temp-dir

# Install apidiff and make sure it's found.
export GOBIN="${KUBE_TEMP}"
PATH="${GOBIN}:${PATH}"
echo "Installing apidiff into ${GOBIN}."
go install golang.org/x/exp/cmd/apidiff@latest

cd "${KUBE_ROOT}"

# output_name targets a target directory and prints the base name of
# an output file for that target.
output_name () {
    what="$1"

    echo "${what}" | sed -e 's/[^a-zA-Z0-9_-]/_/g' -e 's/$/.out/'
}

# run invokes apidiff once per target and stores the output
# file(s) in the given directory.
run () {
    out="$1"
    mkdir -p "$out"
    for d in "${targets[@]}"; do
        apidiff -m -w "${out}/$(output_name "${d}")" "${d}"
    done
}

# runWorktree checks out a specific revision, then invokes run there.
runWorktree () {
    local out="$1"
    local worktree="$2"
    local rev="$3"

    # Create a copy of the repo with the specific revision checked out.
    git worktree add -f -d "${worktree}" "${rev}"
    # Clean up the copy on exit.
    kube::util::trap_add "git worktree remove -f ${worktree}" EXIT

    # Ready for apidiff.
    (
        cd "${worktree}"
        run "${out}"
    )
}

# Dump old and new api state.
if [ -z "${target}" ]; then
    run "${KUBE_TEMP}/after"
else
    runWorktree "${KUBE_TEMP}/after" "${KUBE_TEMP}/target" "${target}"
fi
runWorktree "${KUBE_TEMP}/before" "${KUBE_TEMP}/base" "${base}"

# Now produce a report. All changes get reported because exporting some API
# unnecessarily might also be good to know, but the final exit code will only
# be non-zero if there are incompatible changes.
#
# The report is Markdown-formatted and can be copied into a PR comment verbatim.
res=0
echo
compare () {
    what="$1"
    before="$2"
    after="$3"
    changes=$(apidiff -m "${before}" "${after}" 2>&1 | grep -v -e "^Ignoring internal package") || true
    echo "## ${what}"
    if [ -z "$changes" ]; then
        echo "no changes"
    else
        echo "$changes"
        echo
    fi
    incompatible=$(apidiff -incompatible -m "${before}" "${after}" 2>&1) || true
    if [ -n "$incompatible" ]; then
        res=1
    fi
}

for d in "${targets[@]}"; do
    compare "${d}" "${KUBE_TEMP}/before/$(output_name "${d}")" "${KUBE_TEMP}/after/$(output_name "${d}")"
done

exit "$res"