package main

import (
	"fmt"
	"io"
	"os"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/nspcc-dev/neofs-s3-gw/internal/version"
	"github.com/nspcc-dev/neofs-sdk-go/pkg/pool"
	"github.com/spf13/pflag"
	"github.com/spf13/viper"
	"go.uber.org/zap"
)

const (
	devNull = empty(0)

	minimumTTLInMinutes = 5

	defaultTTL = minimumTTLInMinutes * time.Minute

	defaultRebalanceTimer  = 15 * time.Second
	defaultRequestTimeout  = 15 * time.Second
	defaultConnectTimeout  = 30 * time.Second
	defaultShutdownTimeout = 15 * time.Second

	defaultMaxClientsCount    = 100
	defaultMaxClientsDeadline = time.Second * 30
)

const ( // Settings.
	// Logger.
	cfgLoggerLevel              = "logger.level"
	cfgLoggerFormat             = "logger.format"
	cfgLoggerTraceLevel         = "logger.trace_level"
	cfgLoggerNoCaller           = "logger.no_caller"
	cfgLoggerNoDisclaimer       = "logger.no_disclaimer"
	cfgLoggerSamplingInitial    = "logger.sampling.initial"
	cfgLoggerSamplingThereafter = "logger.sampling.thereafter"

	// Wallet.
	cfgWallet           = "wallet"
	cfgAddress          = "address"
	cfgWalletPassphrase = "wallet.passphrase"

	// HTTPS/TLS.
	cfgTLSKeyFile  = "tls.key_file"
	cfgTLSCertFile = "tls.cert_file"

	// Timeouts.
	cfgConnectionTTL  = "con_ttl"
	cfgConnectTimeout = "connect_timeout"
	cfgRequestTimeout = "request_timeout"
	cfgRebalanceTimer = "rebalance_timer"

	// MaxClients.
	cfgMaxClientsCount    = "max_clients_count"
	cfgMaxClientsDeadline = "max_clients_deadline"

	// gRPC.
	cfgGRPCVerbose = "verbose"

	// Metrics / Profiler / Web.
	cfgEnableMetrics  = "metrics"
	cfgEnableProfiler = "pprof"
	cfgListenAddress  = "listen_address"
	cfgListenDomains  = "listen_domains"

	// Peers.
	cfgPeers = "peers"

	// Application.
	cfgApplicationName      = "app.name"
	cfgApplicationVersion   = "app.version"
	cfgApplicationBuildTime = "app.build_time"

	// Command line args.
	cmdHelp    = "help"
	cmdVersion = "version"

	// applicationName is gateway name.
	applicationName = "neofs-s3-gw"

	// envPrefix is environment variables prefix used for configuration.
	envPrefix = "S3_GW"
)

type empty int

var ignore = map[string]struct{}{
	cfgApplicationName:      {},
	cfgApplicationVersion:   {},
	cfgApplicationBuildTime: {},

	cfgPeers: {},

	cmdHelp:    {},
	cmdVersion: {},
}

func (empty) Read([]byte) (int, error) { return 0, io.EOF }

func fetchPeers(l *zap.Logger, v *viper.Viper) *pool.Builder {
	pb := new(pool.Builder)

	for i := 0; ; i++ {
		key := cfgPeers + "." + strconv.Itoa(i) + "."
		address := v.GetString(key + "address")
		weight := v.GetFloat64(key + "weight")

		if address == "" {
			l.Warn("skip, empty address")
			break
		}
		if weight <= 0 { // unspecified or wrong
			weight = 1
		}
		pb.AddNode(address, weight)

		l.Info("added connection peer",
			zap.String("address", address),
			zap.Float64("weight", weight))
	}

	return pb
}

func fetchDomains(v *viper.Viper) []string {
	cnt := v.GetInt(cfgListenDomains + ".count")
	res := make([]string, 0, cnt)
	for i := 0; ; i++ {
		domain := v.GetString(cfgListenDomains + "." + strconv.Itoa(i))
		if domain == "" {
			break
		}

		res = append(res, domain)
	}

	return res
}

func newSettings() *viper.Viper {
	v := viper.New()

	v.AutomaticEnv()
	v.SetEnvPrefix(envPrefix)
	v.SetConfigType("yaml")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))

	// flags setup:
	flags := pflag.NewFlagSet("commandline", pflag.ExitOnError)
	flags.SetOutput(os.Stdout)
	flags.SortFlags = false

	flags.Bool(cfgEnableProfiler, false, "enable pprof")
	flags.Bool(cfgEnableMetrics, false, "enable prometheus metrics")

	help := flags.BoolP(cmdHelp, "h", false, "show help")
	versionFlag := flags.BoolP(cmdVersion, "v", false, "show version")

	flags.StringP(cfgWallet, "w", "", `path to the wallet`)
	flags.String(cfgAddress, "", `address of wallet account`)

	flags.Bool(cfgGRPCVerbose, false, "set debug mode of gRPC connections")
	flags.Duration(cfgRequestTimeout, defaultRequestTimeout, "set gRPC request timeout")
	flags.Duration(cfgConnectTimeout, defaultConnectTimeout, "set gRPC connect timeout")
	flags.Duration(cfgRebalanceTimer, defaultRebalanceTimer, "set gRPC connection rebalance timer")

	flags.Int(cfgMaxClientsCount, defaultMaxClientsCount, "set max-clients count")
	flags.Duration(cfgMaxClientsDeadline, defaultMaxClientsDeadline, "set max-clients deadline")

	ttl := flags.DurationP(cfgConnectionTTL, "t", defaultTTL, "set gRPC connection time to live")

	flags.String(cfgListenAddress, "0.0.0.0:8080", "set address to listen")
	flags.String(cfgTLSCertFile, "", "TLS certificate file to use")
	flags.String(cfgTLSKeyFile, "", "TLS key file to use")

	peers := flags.StringArrayP(cfgPeers, "p", nil, "set NeoFS nodes")

	domains := flags.StringArrayP(cfgListenDomains, "d", nil, "set domains to be listened")

	// set prefers:
	v.Set(cfgApplicationName, applicationName)
	v.Set(cfgApplicationVersion, version.Version)

	// set defaults:

	// logger:
	v.SetDefault(cfgLoggerLevel, "debug")
	v.SetDefault(cfgLoggerFormat, "console")
	v.SetDefault(cfgLoggerTraceLevel, "panic")
	v.SetDefault(cfgLoggerNoCaller, false)
	v.SetDefault(cfgLoggerNoDisclaimer, true)
	v.SetDefault(cfgLoggerSamplingInitial, 1000)
	v.SetDefault(cfgLoggerSamplingThereafter, 1000)

	if err := v.BindPFlags(flags); err != nil {
		panic(err)
	}

	if err := v.ReadConfig(devNull); err != nil {
		panic(err)
	}

	if err := flags.Parse(os.Args); err != nil {
		panic(err)
	}

	if peers != nil && len(*peers) > 0 {
		for i := range *peers {
			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".address", (*peers)[i])
			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".weight", 1)
		}
	}

	if domains != nil && len(*domains) > 0 {
		for i := range *domains {
			v.SetDefault(cfgListenDomains+"."+strconv.Itoa(i), (*domains)[i])
		}

		v.SetDefault(cfgListenDomains+".count", len(*domains))
	}

	switch {
	case help != nil && *help:
		fmt.Printf("NeoFS S3 gateway %s\n", version.Version)
		flags.PrintDefaults()

		fmt.Println()
		fmt.Println("Default environments:")
		fmt.Println()
		keys := v.AllKeys()
		sort.Strings(keys)

		for i := range keys {
			if _, ok := ignore[keys[i]]; ok {
				continue
			}

			k := strings.Replace(keys[i], ".", "_", -1)
			fmt.Printf("%s_%s = %v\n", envPrefix, strings.ToUpper(k), v.Get(keys[i]))
		}

		fmt.Println()
		fmt.Println("Peers preset:")
		fmt.Println()

		fmt.Printf("%s_%s_[N]_ADDRESS = string\n", envPrefix, strings.ToUpper(cfgPeers))
		fmt.Printf("%s_%s_[N]_WEIGHT = 0..1 (float)\n", envPrefix, strings.ToUpper(cfgPeers))

		os.Exit(0)
	case versionFlag != nil && *versionFlag:
		fmt.Printf("NeoFS S3 gateway %s\n", version.Version)
		os.Exit(0)
	case ttl != nil && ttl.Minutes() < minimumTTLInMinutes:
		fmt.Printf("connection ttl should not be less than %s", defaultTTL)
	}

	return v
}