package main

import (
	"crypto/md5" //nolint:gosec // not used for security
	"encoding/base64"
	"flag"
	"fmt"
	"log"
	"os"
	"runtime"
	"strings"

	"github.com/peterbourgon/ff/v3"

	"edge-infra.dev/pkg/lib/cli/sh"
)

var (
	storageURL    = "https://storage.googleapis.com"
	ciBucket      = "edge-bzl-cache"
	credsPath     string
	enableCache   bool
	uploadResults bool
	bucket        string
	shell         *sh.Shell
	flags         *flag.FlagSet
)

func init() {
	shell = sh.New()
	flags = flag.NewFlagSet("bzl-cache-rc-gen", flag.ExitOnError)

	flags.StringVar(
		&bucket,
		"bucket",
		ciBucket,
		"bucket name to use for cache",
	)

	flags.StringVar(
		&credsPath,
		"google-creds-path",
		"",
		"path to google creds file, if not using google default credentials",
	)

	flags.BoolVar(
		&enableCache,
		"enable-cache",
		false,
		"whether or not cache usage should be applied to every Bazel command by default",
	)

	flags.BoolVar(
		&uploadResults,
		"upload-results",
		false,
		"whether or not results should be uploaded to the cache (R/W) or not (RO)",
	)

	if err := ff.Parse(flags, os.Args[1:], ff.WithEnvVarNoPrefix()); err != nil {
		log.Fatal("failed to parse config")
	}
}

func main() {
	bazelrc := ""

	// if no creds path is provided, use default credentials
	if credsPath == "" {
		bazelrc += "build:cache --google_default_credentials\n"
	} else {
		bazelrc += fmt.Sprintf("build:cache --google_credentials=%s\n", credsPath)
	}

	if uploadResults {
		bazelrc += "build:cache --remote_upload_local_results=true\n"
	}

	// determine full remote cache URL by hasing the environment we are
	// creating the bazelrc file for
	host := fmt.Sprintf("%s/%s", storageURL, bucket)
	// add unique workstation hash to end
	host = fmt.Sprintf("%s/%s", host, hashEnvironment())
	bazelrc += fmt.Sprintf("build:cache --remote_cache=%s\n", host)

	if enableCache {
		bazelrc += "build --config=cache\n"
	}

	fmt.Println(bazelrc)
}

func hashEnvironment() string {
	// $CC and Bazel interactions
	// https://github.com/kubernetes/test-infra/blob/master/images/bootstrap/create_bazel_cache_rcs.sh#L46
	// > if $CC is set bazel will use this to detect c/c++ toolchains, otherwise gcc
	// > https://blog.bazel.build/2016/03/31/autoconfiguration.html
	cc := os.Getenv("CC")
	if cc == "" {
		out, err := shell.Run("gcc -dumpversion")
		if err != nil {
			log.Fatal("failed to determine gcc version", out, err)
		}
		cc = strings.TrimSpace(out)
	}

	// some bazel rules still indirectly depend on host python
	// dont bother checking for python like we do for gcc because
	// it should be installed every
	python, err := shell.Run("python3 --version")
	if err == nil {
		python = strings.TrimSpace(python)
	} else {
		python = "none"
	}

	// add operationg system to hash to split osx + linux
	//nolint:gosec // not used for security
	md5Hash := md5.Sum([]byte(fmt.Sprintf("%s,%s,%s", cc, python, runtime.GOOS)))
	return base64.StdEncoding.EncodeToString(md5Hash[:])
}