// Package cmd provides utilities that underlie the specific commands.
package cmd

import (
	"context"
	"encoding/json"
	"errors"
	"expvar"
	"fmt"
	"io"
	"log"
	"log/syslog"
	"net/http"
	"net/http/pprof"
	"os"
	"os/signal"
	"runtime"
	"runtime/debug"
	"strings"
	"syscall"
	"time"

	"github.com/go-logr/stdr"
	"github.com/go-sql-driver/mysql"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/collectors"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/redis/go-redis/v9"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/resource"
	"go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
	"google.golang.org/grpc/grpclog"

	"github.com/letsencrypt/boulder/core"
	blog "github.com/letsencrypt/boulder/log"
	"github.com/letsencrypt/boulder/strictyaml"
	"github.com/letsencrypt/validator/v10"
)

// Because we don't know when this init will be called with respect to
// flag.Parse() and other flag definitions, we can't rely on the regular
// flag mechanism. But this one is fine.
func init() {
	for _, v := range os.Args {
		if v == "--version" || v == "-version" {
			fmt.Println(VersionString())
			os.Exit(0)
		}
	}
}

// mysqlLogger implements the mysql.Logger interface.
type mysqlLogger struct {
	blog.Logger
}

func (m mysqlLogger) Print(v ...interface{}) {
	m.AuditErrf("[mysql] %s", fmt.Sprint(v...))
}

// grpcLogger implements the grpclog.LoggerV2 interface.
type grpcLogger struct {
	blog.Logger
}

// Ensure that fatal logs exit, because we use neither the gRPC default logger
// nor the stdlib default logger, both of which would call os.Exit(1) for us.
func (log grpcLogger) Fatal(args ...interface{}) {
	log.Error(args...)
	os.Exit(1)
}
func (log grpcLogger) Fatalf(format string, args ...interface{}) {
	log.Errorf(format, args...)
	os.Exit(1)
}
func (log grpcLogger) Fatalln(args ...interface{}) {
	log.Errorln(args...)
	os.Exit(1)
}

// Treat all gRPC error logs as potential audit events.
func (log grpcLogger) Error(args ...interface{}) {
	log.Logger.AuditErr(fmt.Sprint(args...))
}
func (log grpcLogger) Errorf(format string, args ...interface{}) {
	log.Logger.AuditErrf(format, args...)
}
func (log grpcLogger) Errorln(args ...interface{}) {
	log.Logger.AuditErr(fmt.Sprintln(args...))
}

// Pass through most Warnings, but filter out a few noisy ones.
func (log grpcLogger) Warning(args ...interface{}) {
	log.Logger.Warning(fmt.Sprint(args...))
}
func (log grpcLogger) Warningf(format string, args ...interface{}) {
	log.Logger.Warningf(format, args...)
}
func (log grpcLogger) Warningln(args ...interface{}) {
	msg := fmt.Sprintln(args...)
	// See https://github.com/letsencrypt/boulder/issues/4628
	if strings.Contains(msg, `ccResolverWrapper: error parsing service config: no JSON service config provided`) {
		return
	}
	// See https://github.com/letsencrypt/boulder/issues/4379
	if strings.Contains(msg, `Server.processUnaryRPC failed to write status: connection error: desc = "transport is closing"`) {
		return
	}
	// Since we've already formatted the message, just pass through to .Warning()
	log.Logger.Warning(msg)
}

// Don't log any INFO-level gRPC stuff. In practice this is all noise, like
// failed TXT lookups for service discovery (we only use A records).
func (log grpcLogger) Info(args ...interface{})                 {}
func (log grpcLogger) Infof(format string, args ...interface{}) {}
func (log grpcLogger) Infoln(args ...interface{})               {}

// V returns true if the verbosity level l is less than the verbosity we want to
// log at.
func (log grpcLogger) V(l int) bool {
	// We always return false. This causes gRPC to not log some things which are
	// only logged conditionally if the logLevel is set below a certain value.
	// TODO: Use the wrapped log.Logger.stdoutLevel and log.Logger.syslogLevel
	// to determine a correct return value here.
	return false
}

// promLogger implements the promhttp.Logger interface.
type promLogger struct {
	blog.Logger
}

func (log promLogger) Println(args ...interface{}) {
	log.AuditErr(fmt.Sprint(args...))
}

type redisLogger struct {
	blog.Logger
}

func (rl redisLogger) Printf(ctx context.Context, format string, v ...interface{}) {
	rl.Infof(format, v...)
}

// logWriter implements the io.Writer interface.
type logWriter struct {
	blog.Logger
}

func (lw logWriter) Write(p []byte) (n int, err error) {
	// Lines received by logWriter will always have a trailing newline.
	lw.Logger.Info(strings.Trim(string(p), "\n"))
	return
}

// logOutput implements the log.Logger interface's Output method for use with logr
type logOutput struct {
	blog.Logger
}

func (l logOutput) Output(calldepth int, logline string) error {
	l.Logger.Info(logline)
	return nil
}

// StatsAndLogging sets up an AuditLogger, Prometheus Registerer, and
// OpenTelemetry tracing.  It returns the Registerer and AuditLogger, along
// with a graceful shutdown function to be deferred.
//
// It spawns off an HTTP server on the provided port to report the stats and
// provide pprof profiling handlers.
//
// The constructed AuditLogger as the default logger, and configures the mysql
// and grpc packages to use our logger. This must be called before any gRPC code
// is called, because gRPC's SetLogger doesn't use any locking.
//
// This function does not return an error, and will panic on problems.
func StatsAndLogging(logConf SyslogConfig, otConf OpenTelemetryConfig, addr string) (prometheus.Registerer, blog.Logger, func(context.Context)) {
	logger := NewLogger(logConf)

	shutdown := NewOpenTelemetry(otConf, logger)

	return newStatsRegistry(addr, logger), logger, shutdown
}

// NewLogger creates a logger object with the provided settings, sets it as
// the global logger, and returns it.
//
// It also sets the logging systems for various packages we use to go through
// the created logger, and sets up a periodic log event for the current timestamp.
func NewLogger(logConf SyslogConfig) blog.Logger {
	var logger blog.Logger
	if logConf.SyslogLevel >= 0 {
		syslogger, err := syslog.Dial(
			"",
			"",
			syslog.LOG_INFO, // default, not actually used
			core.Command())
		FailOnError(err, "Could not connect to Syslog")
		syslogLevel := int(syslog.LOG_INFO)
		if logConf.SyslogLevel != 0 {
			syslogLevel = logConf.SyslogLevel
		}
		logger, err = blog.New(syslogger, logConf.StdoutLevel, syslogLevel)
		FailOnError(err, "Could not connect to Syslog")
	} else {
		logger = blog.StdoutLogger(logConf.StdoutLevel)
	}

	_ = blog.Set(logger)
	_ = mysql.SetLogger(mysqlLogger{logger})
	grpclog.SetLoggerV2(grpcLogger{logger})
	log.SetOutput(logWriter{logger})
	redis.SetLogger(redisLogger{logger})

	// Periodically log the current timestamp, to ensure syslog timestamps match
	// Boulder's conception of time.
	go func() {
		for {
			time.Sleep(time.Minute)
			logger.Info(fmt.Sprintf("time=%s", time.Now().Format(time.RFC3339Nano)))
		}
	}()
	return logger
}

func newVersionCollector() prometheus.Collector {
	buildTime := core.Unspecified
	if core.GetBuildTime() != core.Unspecified {
		// core.BuildTime is set by our Makefile using the shell command 'date
		// -u' which outputs in a consistent format across all POSIX systems.
		bt, err := time.Parse(time.UnixDate, core.BuildTime)
		if err != nil {
			// Should never happen unless the Makefile is changed.
			buildTime = "Unparsable"
		} else {
			buildTime = bt.Format(time.RFC3339)
		}
	}
	return prometheus.NewGaugeFunc(
		prometheus.GaugeOpts{
			Name: "version",
			Help: fmt.Sprintf(
				"A metric with a constant value of '1' labeled by the short commit-id (buildId), build timestamp in RFC3339 format (buildTime), and Go release tag like 'go1.3' (goVersion) from which %s was built.",
				core.Command(),
			),
			ConstLabels: prometheus.Labels{
				"buildId":   core.GetBuildID(),
				"buildTime": buildTime,
				"goVersion": runtime.Version(),
			},
		},
		func() float64 { return 1 },
	)
}

func newStatsRegistry(addr string, logger blog.Logger) prometheus.Registerer {
	registry := prometheus.NewRegistry()
	registry.MustRegister(collectors.NewGoCollector())
	registry.MustRegister(collectors.NewProcessCollector(
		collectors.ProcessCollectorOpts{}))
	registry.MustRegister(newVersionCollector())

	mux := http.NewServeMux()
	// Register the available pprof handlers. These are all registered on
	// DefaultServeMux just by importing pprof, but since we eschew
	// DefaultServeMux, we need to explicitly register them on our own mux.
	mux.Handle("/debug/pprof/", http.HandlerFunc(pprof.Index))
	mux.Handle("/debug/pprof/profile", http.HandlerFunc(pprof.Profile))
	mux.Handle("/debug/pprof/symbol", http.HandlerFunc(pprof.Symbol))
	mux.Handle("/debug/pprof/trace", http.HandlerFunc(pprof.Trace))
	// These handlers are defined in runtime/pprof instead of net/http/pprof, and
	// have to be accessed through net/http/pprof's Handler func.
	mux.Handle("/debug/pprof/goroutine", pprof.Handler("goroutine"))
	mux.Handle("/debug/pprof/block", pprof.Handler("block"))
	mux.Handle("/debug/pprof/heap", pprof.Handler("heap"))
	mux.Handle("/debug/pprof/mutex", pprof.Handler("mutex"))
	mux.Handle("/debug/pprof/threadcreate", pprof.Handler("threadcreate"))

	mux.Handle("/debug/vars", expvar.Handler())
	mux.Handle("/metrics", promhttp.HandlerFor(registry, promhttp.HandlerOpts{
		ErrorLog: promLogger{logger},
	}))

	server := http.Server{
		Addr:        addr,
		Handler:     mux,
		ReadTimeout: time.Minute,
	}
	go func() {
		err := server.ListenAndServe()
		if err != nil {
			logger.Errf("unable to boot debug server on %s: %v", addr, err)
			os.Exit(1)
		}
	}()
	return registry
}

// NewOpenTelemetry sets up our OpenTelemetry tracing
// It returns a graceful shutdown function to be deferred.
func NewOpenTelemetry(config OpenTelemetryConfig, logger blog.Logger) func(ctx context.Context) {
	otel.SetLogger(stdr.New(logOutput{logger}))
	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) { logger.Errf("OpenTelemetry error: %v", err) }))

	r, err := resource.Merge(
		resource.Default(),
		resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceNameKey.String(core.Command()),
			semconv.ServiceVersionKey.String(core.GetBuildID()),
		),
	)
	if err != nil {
		FailOnError(err, "Could not create OpenTelemetry resource")
	}

	opts := []trace.TracerProviderOption{
		trace.WithResource(r),
		// Use a ParentBased sampler to respect the sample decisions on incoming
		// traces, and TraceIDRatioBased to randomly sample new traces.
		trace.WithSampler(trace.ParentBased(trace.TraceIDRatioBased(config.SampleRatio))),
	}

	if config.Endpoint != "" {
		exporter, err := otlptracegrpc.New(
			context.Background(),
			otlptracegrpc.WithInsecure(),
			otlptracegrpc.WithEndpoint(config.Endpoint))
		if err != nil {
			FailOnError(err, "Could not create OpenTelemetry OTLP exporter")
		}

		opts = append(opts, trace.WithBatcher(exporter))
	}

	tracerProvider := trace.NewTracerProvider(opts...)
	otel.SetTracerProvider(tracerProvider)
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))

	return func(ctx context.Context) {
		err := tracerProvider.Shutdown(ctx)
		if err != nil {
			logger.Errf("Error while shutting down OpenTelemetry: %v", err)
		}
	}
}

// AuditPanic catches and logs panics, then exits with exit code 1.
// This method should be called in a defer statement as early as possible.
func AuditPanic() {
	err := recover()
	// No panic, no problem
	if err == nil {
		return
	}
	// Get the global logger if it's initialized, or create a default one if not.
	// We could wind up creating a default logger if we panic so early in a process'
	// lifetime that we haven't yet parsed the config and created a logger.
	log := blog.Get()
	// For the special type `failure`, audit log the message and exit quietly
	fail, ok := err.(failure)
	if ok {
		log.AuditErr(fail.msg)
	} else {
		// For all other values passed to `panic`, log them and a stack trace
		log.AuditErrf("Panic caused by err: %s", err)

		log.AuditErrf("Stack Trace (Current goroutine) %s", debug.Stack())
	}
	// Because this function is deferred as early as possible, there's no further defers to run after this one
	// So it is safe to os.Exit to set the exit code and exit without losing any defers we haven't executed.
	os.Exit(1)
}

// failure is a sentinel type that `Fail` passes to `panic` so `AuditPanic` can exit
// quietly and print the msg.
type failure struct {
	msg string
}

func (f failure) String() string {
	return f.msg
}

// Fail raises a panic with a special type that causes `AuditPanic` to audit log the provided message
// and then exit nonzero (without printing a stack trace).
func Fail(msg string) {
	panic(failure{msg})
}

// FailOnError calls Fail if the provided error is non-nil.
// This is useful for one-line error handling in top-level executables,
// but should generally be avoided in libraries. The message argument is optional.
func FailOnError(err error, msg string) {
	if err == nil {
		return
	}
	if msg == "" {
		Fail(err.Error())
	} else {
		Fail(fmt.Sprintf("%s: %s", msg, err))
	}
}

func decodeJSONStrict(in io.Reader, out interface{}) error {
	decoder := json.NewDecoder(in)
	decoder.DisallowUnknownFields()

	return decoder.Decode(out)
}

// ReadConfigFile takes a file path as an argument and attempts to
// unmarshal the content of the file into a struct containing a
// configuration of a boulder component. Any config keys in the JSON
// file which do not correspond to expected keys in the config struct
// will result in errors.
func ReadConfigFile(filename string, out interface{}) error {
	file, err := os.Open(filename)
	if err != nil {
		return err
	}
	defer file.Close()

	return decodeJSONStrict(file, out)
}

// ValidateJSONConfig takes a *ConfigValidator and an io.Reader containing a
// JSON representation of a config. The JSON data is unmarshaled into the
// *ConfigValidator's inner Config and then validated according to the
// 'validate' tags for on each field. Callers can use cmd.LookupConfigValidator
// to get a *ConfigValidator for a given Boulder component. This is exported for
// use in SRE CI tooling.
func ValidateJSONConfig(cv *ConfigValidator, in io.Reader) error {
	if cv == nil {
		return errors.New("config validator cannot be nil")
	}

	// Initialize the validator and load any custom tags.
	validate := validator.New()
	for tag, v := range cv.Validators {
		err := validate.RegisterValidation(tag, v)
		if err != nil {
			return err
		}
	}

	err := decodeJSONStrict(in, cv.Config)
	if err != nil {
		return err
	}
	err = validate.Struct(cv.Config)
	if err != nil {
		errs, ok := err.(validator.ValidationErrors)
		if !ok {
			// This should never happen.
			return err
		}
		if len(errs) > 0 {
			allErrs := []string{}
			for _, e := range errs {
				allErrs = append(allErrs, e.Error())
			}
			return errors.New(strings.Join(allErrs, ", "))
		}
	}
	return nil
}

// ValidateYAMLConfig takes a *ConfigValidator and an io.Reader containing a
// YAML representation of a config. The YAML data is unmarshaled into the
// *ConfigValidator's inner Config and then validated according to the
// 'validate' tags for on each field. Callers can use cmd.LookupConfigValidator
// to get a *ConfigValidator for a given Boulder component. This is exported for
// use in SRE CI tooling.
func ValidateYAMLConfig(cv *ConfigValidator, in io.Reader) error {
	if cv == nil {
		return errors.New("config validator cannot be nil")
	}

	// Initialize the validator and load any custom tags.
	validate := validator.New()
	for tag, v := range cv.Validators {
		err := validate.RegisterValidation(tag, v)
		if err != nil {
			return err
		}
	}

	inBytes, err := io.ReadAll(in)
	if err != nil {
		return err
	}
	err = strictyaml.Unmarshal(inBytes, cv.Config)
	if err != nil {
		return err
	}
	err = validate.Struct(cv.Config)
	if err != nil {
		errs, ok := err.(validator.ValidationErrors)
		if !ok {
			// This should never happen.
			return err
		}
		if len(errs) > 0 {
			allErrs := []string{}
			for _, e := range errs {
				allErrs = append(allErrs, e.Error())
			}
			return errors.New(strings.Join(allErrs, ", "))
		}
	}
	return nil
}

// VersionString produces a friendly Application version string.
func VersionString() string {
	return fmt.Sprintf("Versions: %s=(%s %s) Golang=(%s) BuildHost=(%s)", core.Command(), core.GetBuildID(), core.GetBuildTime(), runtime.Version(), core.GetBuildHost())
}

// CatchSignals blocks until a SIGTERM, SIGINT, or SIGHUP is received, then
// executes the given callback. The callback should not block, it should simply
// signal other goroutines (particularly the main goroutine) to clean themselves
// up and exit. This function is intended to be called in its own goroutine,
// while the main goroutine waits for an indication that the other goroutines
// have exited cleanly.
func CatchSignals(callback func()) {
	WaitForSignal()
	callback()
}

// WaitForSignal blocks until a SIGTERM, SIGINT, or SIGHUP is received. It then
// returns, allowing execution to resume, generally allowing a main() function
// to return and trigger and deferred cleanup functions. This function is
// intended to be called directly from the main goroutine, while a gRPC or HTTP
// server runs in a background goroutine.
func WaitForSignal() {
	sigChan := make(chan os.Signal, 1)
	signal.Notify(sigChan, syscall.SIGTERM)
	signal.Notify(sigChan, syscall.SIGINT)
	signal.Notify(sigChan, syscall.SIGHUP)
	<-sigChan
}