package main

import (
	"fmt"
	"os"
	"path"
	"runtime"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/TrueCloudLab/frostfs-http-gw/resolver"
	"github.com/spf13/pflag"
	"github.com/spf13/viper"
	"github.com/valyala/fasthttp"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)

const (
	defaultRebalanceTimer = 60 * time.Second
	defaultRequestTimeout = 15 * time.Second
	defaultConnectTimeout = 10 * time.Second
	defaultStreamTimeout  = 10 * time.Second

	defaultShutdownTimeout = 15 * time.Second

	defaultPoolErrorThreshold uint32 = 100

	cfgServer      = "server"
	cfgTLSEnabled  = "tls.enabled"
	cfgTLSCertFile = "tls.cert_file"
	cfgTLSKeyFile  = "tls.key_file"

	// Web.
	cfgWebReadBufferSize     = "web.read_buffer_size"
	cfgWebWriteBufferSize    = "web.write_buffer_size"
	cfgWebReadTimeout        = "web.read_timeout"
	cfgWebWriteTimeout       = "web.write_timeout"
	cfgWebStreamRequestBody  = "web.stream_request_body"
	cfgWebMaxRequestBodySize = "web.max_request_body_size"

	// Metrics / Profiler.
	cfgPrometheusEnabled = "prometheus.enabled"
	cfgPrometheusAddress = "prometheus.address"
	cfgPprofEnabled      = "pprof.enabled"
	cfgPprofAddress      = "pprof.address"

	// Pool config.
	cfgConTimeout         = "connect_timeout"
	cfgStreamTimeout      = "stream_timeout"
	cfgReqTimeout         = "request_timeout"
	cfgRebalance          = "rebalance_timer"
	cfgPoolErrorThreshold = "pool_error_threshold"

	// Logger.
	cfgLoggerLevel = "logger.level"

	// Wallet.
	cfgWalletPassphrase = "wallet.passphrase"
	cfgWalletPath       = "wallet.path"
	cfgWalletAddress    = "wallet.address"

	// Uploader Header.
	cfgUploaderHeaderEnableDefaultTimestamp = "upload_header.use_default_timestamp"

	// Peers.
	cfgPeers = "peers"

	// NeoGo.
	cfgRPCEndpoint = "rpc_endpoint"

	// Resolving.
	cfgResolveOrder = "resolve_order"

	// Zip compression.
	cfgZipCompression = "zip.compression"

	// Command line args.
	cmdHelp          = "help"
	cmdVersion       = "version"
	cmdPprof         = "pprof"
	cmdMetrics       = "metrics"
	cmdWallet        = "wallet"
	cmdAddress       = "address"
	cmdConfig        = "config"
	cmdConfigDir     = "config-dir"
	cmdListenAddress = "listen_address"
)

var ignore = map[string]struct{}{
	cfgPeers:   {},
	cmdHelp:    {},
	cmdVersion: {},
}

func settings() *viper.Viper {
	v := viper.New()
	v.AutomaticEnv()
	v.SetEnvPrefix(Prefix)
	v.AllowEmptyEnv(true)
	v.SetConfigType("yaml")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))

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

	flags.Bool(cmdPprof, false, "enable pprof")
	flags.Bool(cmdMetrics, false, "enable prometheus")

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

	flags.StringP(cmdWallet, "w", "", `path to the wallet`)
	flags.String(cmdAddress, "", `address of wallet account`)
	flags.StringArray(cmdConfig, nil, "config paths")
	flags.String(cmdConfigDir, "", "config dir path")
	flags.Duration(cfgConTimeout, defaultConnectTimeout, "gRPC connect timeout")
	flags.Duration(cfgStreamTimeout, defaultStreamTimeout, "gRPC individual message timeout")
	flags.Duration(cfgReqTimeout, defaultRequestTimeout, "gRPC request timeout")
	flags.Duration(cfgRebalance, defaultRebalanceTimer, "gRPC connection rebalance timer")

	flags.String(cmdListenAddress, "0.0.0.0:8080", "addresses to listen")
	flags.String(cfgTLSCertFile, "", "TLS certificate path")
	flags.String(cfgTLSKeyFile, "", "TLS key path")
	peers := flags.StringArrayP(cfgPeers, "p", nil, "FrostFS nodes")

	resolveMethods := flags.StringSlice(cfgResolveOrder, []string{resolver.NNSResolver, resolver.DNSResolver}, "set container name resolve order")

	// set defaults:

	// logger:
	v.SetDefault(cfgLoggerLevel, "debug")

	// pool:
	v.SetDefault(cfgPoolErrorThreshold, defaultPoolErrorThreshold)

	// web-server:
	v.SetDefault(cfgWebReadBufferSize, 4096)
	v.SetDefault(cfgWebWriteBufferSize, 4096)
	v.SetDefault(cfgWebReadTimeout, time.Minute*10)
	v.SetDefault(cfgWebWriteTimeout, time.Minute*5)
	v.SetDefault(cfgWebStreamRequestBody, true)
	v.SetDefault(cfgWebMaxRequestBodySize, fasthttp.DefaultMaxRequestBodySize)

	// upload header
	v.SetDefault(cfgUploaderHeaderEnableDefaultTimestamp, false)

	// zip:
	v.SetDefault(cfgZipCompression, false)

	// metrics
	v.SetDefault(cfgPprofAddress, "localhost:8083")
	v.SetDefault(cfgPrometheusAddress, "localhost:8084")

	// Binding flags
	if err := v.BindPFlag(cfgPprofEnabled, flags.Lookup(cmdPprof)); err != nil {
		panic(err)
	}
	if err := v.BindPFlag(cfgPrometheusEnabled, flags.Lookup(cmdMetrics)); err != nil {
		panic(err)
	}

	if err := v.BindPFlag(cfgWalletPath, flags.Lookup(cmdWallet)); err != nil {
		panic(err)
	}

	if err := v.BindPFlag(cfgWalletAddress, flags.Lookup(cmdAddress)); err != nil {
		panic(err)
	}

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

	if err := v.BindPFlag(cfgServer+".0.address", flags.Lookup(cmdListenAddress)); err != nil {
		panic(err)
	}
	if err := v.BindPFlag(cfgServer+".0."+cfgTLSKeyFile, flags.Lookup(cfgTLSKeyFile)); err != nil {
		panic(err)
	}
	if err := v.BindPFlag(cfgServer+".0."+cfgTLSCertFile, flags.Lookup(cfgTLSCertFile)); err != nil {
		panic(err)
	}

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

	if v.IsSet(cfgServer+".0."+cfgTLSKeyFile) && v.IsSet(cfgServer+".0."+cfgTLSCertFile) {
		v.Set(cfgServer+".0."+cfgTLSEnabled, true)
	}

	if resolveMethods != nil {
		v.SetDefault(cfgResolveOrder, *resolveMethods)
	}

	switch {
	case help != nil && *help:
		fmt.Printf("FrostFS HTTP Gateway %s\n", 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
			}

			defaultValue := v.GetString(keys[i])
			if len(defaultValue) == 0 {
				continue
			}

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

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

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

		os.Exit(0)
	case version != nil && *version:
		fmt.Printf("FrostFS HTTP Gateway\nVersion: %s\nGoVersion: %s\n", Version, runtime.Version())
		os.Exit(0)
	}

	if err := readInConfig(v); 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)
			v.SetDefault(cfgPeers+"."+strconv.Itoa(i)+".priority", 1)
		}
	}

	return v
}

func readInConfig(v *viper.Viper) error {
	if v.IsSet(cmdConfig) {
		if err := readConfig(v); err != nil {
			return err
		}
	}

	if v.IsSet(cmdConfigDir) {
		if err := readConfigDir(v); err != nil {
			return err
		}
	}

	return nil
}

func readConfigDir(v *viper.Viper) error {
	cfgSubConfigDir := v.GetString(cmdConfigDir)
	entries, err := os.ReadDir(cfgSubConfigDir)
	if err != nil {
		return err
	}

	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}
		ext := path.Ext(entry.Name())
		if ext != ".yaml" && ext != ".yml" {
			continue
		}

		if err = mergeConfig(v, path.Join(cfgSubConfigDir, entry.Name())); err != nil {
			return err
		}
	}

	return nil
}

func readConfig(v *viper.Viper) error {
	for _, fileName := range v.GetStringSlice(cmdConfig) {
		if err := mergeConfig(v, fileName); err != nil {
			return err
		}
	}
	return nil
}

func mergeConfig(v *viper.Viper, fileName string) error {
	cfgFile, err := os.Open(fileName)
	if err != nil {
		return err
	}

	defer func() {
		if errClose := cfgFile.Close(); errClose != nil {
			panic(errClose)
		}
	}()

	if err = v.MergeConfig(cfgFile); err != nil {
		return err
	}

	return nil
}

// newLogger constructs a zap.Logger instance for current application.
// Panics on failure.
//
// Logger is built from zap's production logging configuration with:
//   - parameterized level (debug by default)
//   - console encoding
//   - ISO8601 time encoding
//
// Logger records a stack trace for all messages at or above fatal level.
//
// See also zapcore.Level, zap.NewProductionConfig, zap.AddStacktrace.
func newLogger(v *viper.Viper) (*zap.Logger, zap.AtomicLevel) {
	lvl, err := getLogLevel(v)
	if err != nil {
		panic(err)
	}

	c := zap.NewProductionConfig()
	c.Level = zap.NewAtomicLevelAt(lvl)
	c.Encoding = "console"
	c.EncoderConfig.EncodeTime = zapcore.ISO8601TimeEncoder

	l, err := c.Build(
		zap.AddStacktrace(zap.NewAtomicLevelAt(zap.FatalLevel)),
	)
	if err != nil {
		panic(fmt.Sprintf("build zap logger instance: %v", err))
	}

	return l, c.Level
}

func getLogLevel(v *viper.Viper) (zapcore.Level, error) {
	var lvl zapcore.Level
	lvlStr := v.GetString(cfgLoggerLevel)
	err := lvl.UnmarshalText([]byte(lvlStr))
	if err != nil {
		return lvl, fmt.Errorf("incorrect logger level configuration %s (%v), "+
			"value should be one of %v", lvlStr, err, [...]zapcore.Level{
			zapcore.DebugLevel,
			zapcore.InfoLevel,
			zapcore.WarnLevel,
			zapcore.ErrorLevel,
			zapcore.DPanicLevel,
			zapcore.PanicLevel,
			zapcore.FatalLevel,
		})
	}
	return lvl, nil
}

func fetchServers(v *viper.Viper) []ServerInfo {
	var servers []ServerInfo

	for i := 0; ; i++ {
		key := cfgServer + "." + strconv.Itoa(i) + "."

		var serverInfo ServerInfo
		serverInfo.Address = v.GetString(key + "address")
		serverInfo.TLS.Enabled = v.GetBool(key + cfgTLSEnabled)
		serverInfo.TLS.KeyFile = v.GetString(key + cfgTLSKeyFile)
		serverInfo.TLS.CertFile = v.GetString(key + cfgTLSCertFile)

		if serverInfo.Address == "" {
			break
		}

		servers = append(servers, serverInfo)
	}

	return servers
}