// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause

// Package flakytest contains test helpers for marking a test as flaky.
//
// Marking a test with [Mark] is not required for cmd/testwrapper to retry
// failed tests; the wrapper retries any failure within a per-test time
// budget and reports a test as flaky if it ever passes on retry. Mark is
// useful for tracking a known-flaky test against a GitHub issue and for the
// TS_SKIP_FLAKY_TESTS skip behavior used to keep CI green when a flake is
// being investigated.
package flakytest

import (
	"fmt"
	"os"
	"path"
	"regexp"
	"strconv"
	"sync"
	"testing"

	"tailscale.com/util/mak"
)

// FlakyTestLogMessage is a sentinel value that is printed to stderr when a
// flaky test is marked. This is used by cmd/testwrapper to detect flaky tests
// and retry them.
const FlakyTestLogMessage = "flakytest: this is a known flaky test"

// FlakeAttemptEnv is an environment variable that is set by cmd/testwrapper
// when a flaky test is being (re)tried. It contains the attempt number,
// starting at 1.
const FlakeAttemptEnv = "TS_TESTWRAPPER_ATTEMPT"

var issueRegexp = regexp.MustCompile(`\Ahttps://github\.com/[a-zA-Z0-9_.-]+/[a-zA-Z0-9_.-]+/issues/\d+\z`)

var (
	rootFlakesMu sync.Mutex
	rootFlakes   map[string]bool
)

// Mark sets the current test as a flaky test, such that if it fails, it will
// be retried a few times on failure. issue must be a GitHub issue that tracks
// the status of the flaky test being marked, of the format:
//
//	https://github.com/tailscale/myRepo-H3re/issues/12345
func Mark(t testing.TB, issue string) {
	if !issueRegexp.MatchString(issue) {
		t.Fatalf("bad issue format: %q", issue)
	}
	if _, ok := os.LookupEnv(FlakeAttemptEnv); ok {
		// We're being run under cmd/testwrapper so send our sentinel message
		// to stderr. (We avoid doing this when the env is absent to avoid
		// spamming people running tests without the wrapper)
		fmt.Fprintf(os.Stderr, "%s: %s\n", FlakyTestLogMessage, issue)
	}
	t.Attr("flaky-test-issue-url", issue)

	// The Attr method above also emits human-readable output, so this t.Logf
	// is somewhat redundant, but we keep it for compatibility with
	// old test runs, so cmd/testwrapper doesn't need to be modified.
	// TODO(bradfitz): switch testwrapper to look for Action "attr"
	// instead:
	// "Action":"attr","Package":"tailscale.com/cmd/testwrapper/flakytest","Test":"TestMarked_Root","Key":"flaky-test-issue-url","Value":"https://github.com/tailscale/tailscale/issues/0"}
	// And then remove this Logf a month or so after that.
	t.Logf("flakytest: issue tracking this flaky test: %s", issue)

	if boolEnv("TS_SKIP_FLAKY_TESTS") {
		t.Skipf("skipping due to TS_SKIP_FLAKY_TESTS")
	}

	// Record the root test name as flakey.
	rootFlakesMu.Lock()
	defer rootFlakesMu.Unlock()
	mak.Set(&rootFlakes, t.Name(), true)
}

// Marked reports whether the current test or one of its parents was marked flaky.
func Marked(t testing.TB) bool {
	n := t.Name()
	for {
		if rootFlakes[n] {
			return true
		}
		n = path.Dir(n)
		if n == "." || n == "/" {
			break
		}
	}
	return false
}

func boolEnv(k string) bool {
	s := os.Getenv(k)
	if s == "" {
		return false
	}
	v, _ := strconv.ParseBool(s)
	return v
}
