// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package tstest

import (
	"log"
	"os"
	"sync"
	"testing"

	"tailscale.com/types/logger"
)

type testLogWriter struct {
	t *testing.T
}

func (w *testLogWriter) Write(b []byte) (int, error) {
	w.t.Helper()
	w.t.Logf("%s", b)
	return len(b), nil
}

func FixLogs(t *testing.T) {
	log.SetFlags(log.Ltime | log.Lshortfile)
	log.SetOutput(&testLogWriter{t})
}

func UnfixLogs(t *testing.T) {
	defer log.SetOutput(os.Stderr)
}

type panicLogWriter struct{}

func (panicLogWriter) Write(b []byte) (int, error) {
	panic("please use tailscale.com/logger.Logf instead of the log package")
}

// PanicOnLog modifies the standard library log package's default output to
// an io.Writer that panics, to root out code that's not plumbing their logging
// through explicit tailscale.com/logger.Logf paths.
func PanicOnLog() {
	log.SetOutput(panicLogWriter{})
}

// NewLogLineTracker produces a LogLineTracker wrapping a given logf that tracks whether expectedFormatStrings were seen.
func NewLogLineTracker(logf logger.Logf, expectedFormatStrings []string) *LogLineTracker {
	ret := &LogLineTracker{
		logf:      logf,
		listenFor: expectedFormatStrings,
		seen:      make(map[string]bool),
	}
	for _, line := range expectedFormatStrings {
		ret.seen[line] = false
	}
	return ret
}

// LogLineTracker is a logger that tracks which log format patterns it's
// seen and can report which expected ones were not seen later.
type LogLineTracker struct {
	logf      logger.Logf
	listenFor []string

	mu   sync.Mutex
	seen map[string]bool // format string => false (if not yet seen but wanted) or true (once seen)
}

// Logf logs to its underlying logger and also tracks that the given format pattern has been seen.
func (lt *LogLineTracker) Logf(format string, args ...interface{}) {
	lt.mu.Lock()
	if v, ok := lt.seen[format]; ok && !v {
		lt.seen[format] = true
	}
	lt.mu.Unlock()
	lt.logf(format, args)
}

// Check returns which format strings haven't been logged yet.
func (lt *LogLineTracker) Check() []string {
	lt.mu.Lock()
	defer lt.mu.Unlock()
	var notSeen []string
	for _, format := range lt.listenFor {
		if !lt.seen[format] {
			notSeen = append(notSeen, format)
		}
	}
	return notSeen
}