package old_tcp_tailscale // Copyright (c) Tailscale Inc & AUTHORS

import (
	"bufio"
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"sync"
	"time"

	"context"
)

// Logf is the basic Tailscale logger type: a printf-like func.
// Like log.Printf, the format need not end in a newline.
// Logf functions must be safe for concurrent use.
type Logf func(format string, args ...any)

// A Context is a context.Context that should contain a custom log function, obtainable from FromContext.
// If no log function is present, FromContext will return log.Printf.
// To construct a Context, use Add
//
// Deprecated: Do not use.
type Context context.Context

// jenc is a json.Encode + bytes.Buffer pair wired up to be reused in a pool.
type jenc struct {
	buf bytes.Buffer
	enc *json.Encoder
}

var jencPool = &sync.Pool{New: func() any {
	je := new(jenc)
	je.enc = json.NewEncoder(&je.buf)
	return je
}}

// JSON marshals v as JSON and writes it to logf formatted with the annotation to make logtail
// treat it as a structured log.
//
// The recType is the record type and becomes the key of the wrapper
// JSON object that is logged. That is, if recType is "foo" and v is
// 123, the value logged is {"foo":123}.
//
// Do not use recType "logtail", "v", "text", or "metrics", with any case.
// Those are reserved for the logging system.
//
// The level can be from 0 to 9. Levels from 1 to 9 are included in
// the logged JSON object, like {"foo":123,"v":2}.
func (logf Logf) JSON(level int, recType string, v any) {
	je := jencPool.Get().(*jenc)
	defer jencPool.Put(je)
	je.buf.Reset()
	je.buf.WriteByte('{')
	je.enc.Encode(recType)
	je.buf.Truncate(je.buf.Len() - 1) // remove newline from prior Encode
	je.buf.WriteByte(':')
	if err := je.enc.Encode(v); err != nil {
		logf("[unexpected]: failed to encode structured JSON log record of type %q / %T: %v", recType, v, err)
		return
	}
	je.buf.Truncate(je.buf.Len() - 1) // remove newline from prior Encode
	je.buf.WriteByte('}')
	// Magic prefix recognized by logtail:
	logf("[v\x00JSON]%d%s", level%10, je.buf.Bytes())

}

// WithPrefix wraps f, prefixing each format with the provided prefix.
func WithPrefix(f Logf, prefix string) Logf {
	return func(format string, args ...any) {
		f(prefix+format, args...)
	}
}

// FuncWriter returns an io.Writer that writes to f.
func FuncWriter(f Logf) io.Writer {
	return funcWriter{f}
}

// StdLogger returns a standard library logger from a Logf.
func StdLogger(f Logf) *log.Logger {
	return log.New(FuncWriter(f), "", 0)
}

type funcWriter struct{ f Logf }

func (w funcWriter) Write(p []byte) (int, error) {
	w.f("%s", p)
	return len(p), nil
}

// Discard is a Logf that throws away the logs given to it.
func Discard(string, ...any) {}

// LogOnChange logs a given line only if line != lastLine, or if maxInterval has passed
// since the last time this identical line was logged.
func LogOnChange(logf Logf, maxInterval time.Duration, timeNow func() time.Time) Logf {
	var (
		mu          sync.Mutex
		sLastLogged string
		tLastLogged = timeNow()
	)

	return func(format string, args ...any) {
		s := fmt.Sprintf(format, args...)

		mu.Lock()
		if s == sLastLogged && timeNow().Sub(tLastLogged) < maxInterval {
			mu.Unlock()
			return
		}
		sLastLogged = s
		tLastLogged = timeNow()
		mu.Unlock()

		// Re-stringify it (instead of using "%s", s) so something like "%s"
		// doesn't end up getting rate-limited. (And can't use 's' as the pattern,
		// as it might contain formatting directives.)
		logf(format, args...)
	}
}

// ArgWriter is a fmt.Formatter that can be passed to any Logf func to
// efficiently write to a %v argument without allocations.
type ArgWriter func(*bufio.Writer)

func (fn ArgWriter) Format(f fmt.State, _ rune) {
	bw := argBufioPool.Get().(*bufio.Writer)
	bw.Reset(f)
	fn(bw)
	bw.Flush()
	argBufioPool.Put(bw)
}

var argBufioPool = &sync.Pool{New: func() any { return bufio.NewWriterSize(io.Discard, 1024) }}

// Filtered returns a Logf that silently swallows some log lines.
// Each inbound format and args is evaluated and printed to a string s.
// The original format and args are passed to logf if and only if allow(s) returns true.
func Filtered(logf Logf, allow func(s string) bool) Logf {
	return func(format string, args ...any) {
		msg := fmt.Sprintf(format, args...)
		if !allow(msg) {
			return
		}
		logf(format, args...)
	}
}

// LogfCloser wraps logf to create a logger that can be closed.
// Calling close makes all future calls to newLogf into no-ops.
func LogfCloser(logf Logf) (newLogf Logf, close func()) {
	var (
		mu     sync.Mutex
		closed bool
	)
	close = func() {
		mu.Lock()
		defer mu.Unlock()
		closed = true
	}
	newLogf = func(msg string, args ...any) {
		mu.Lock()
		if closed {
			mu.Unlock()
			return
		}
		mu.Unlock()
		logf(msg, args...)
	}
	return newLogf, close
}

// AsJSON returns a formatter that formats v as JSON. The value is suitable to
// passing to a regular %v printf argument. (%s is not required)
//
// If json.Marshal returns an error, the output is "%%!JSON-ERROR:" followed by
// the error string.
func AsJSON(v any) fmt.Formatter {
	return asJSONResult{v}
}

type asJSONResult struct{ v any }

func (a asJSONResult) Format(s fmt.State, verb rune) {
	v, err := json.Marshal(a.v)
	if err != nil {
		fmt.Fprintf(s, "%%!JSON-ERROR:%v", err)
		return
	}
	s.Write(v)
}

// TBLogger is the testing.TB subset needed by TestLogger.
type TBLogger interface {
	Helper()
	Logf(format string, args ...any)
}

// TestLogger returns a logger that logs to tb.Logf
// with a prefix to make it easier to distinguish spam
// from explicit test failures.
func TestLogger(tb TBLogger) Logf {
	return func(format string, args ...any) {
		tb.Helper()
		tb.Logf("    ... "+format, args...)
	}
}
