package serverimp

import (
	"context"
	"errors"
	"io"
	"net"
	"net/http"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/tech/sendico/gateway/mntx/internal/appversion"
	mntxservice "github.com/tech/sendico/gateway/mntx/internal/service/gateway"
	"github.com/tech/sendico/gateway/mntx/internal/service/monetix"
	"github.com/tech/sendico/pkg/api/routers"
	"github.com/tech/sendico/pkg/merrors"
	msg "github.com/tech/sendico/pkg/messaging"
	"github.com/tech/sendico/pkg/mlogger"
	gatewayv1 "github.com/tech/sendico/pkg/proto/common/gateway/v1"
	"github.com/tech/sendico/pkg/server/grpcapp"
	"go.uber.org/zap"
	"gopkg.in/yaml.v3"
)

type Imp struct {
	logger mlogger.Logger
	file   string
	debug  bool

	config  *config
	app     *grpcapp.App[struct{}]
	http    *http.Server
	service *mntxservice.Service
}

type config struct {
	*grpcapp.Config `yaml:",inline"`
	Monetix         monetixConfig `yaml:"monetix"`
	Gateway         gatewayConfig `yaml:"gateway"`
	HTTP            httpConfig    `yaml:"http"`
}

type monetixConfig struct {
	BaseURL                string   `yaml:"base_url"`
	BaseURLEnv             string   `yaml:"base_url_env"`
	ProjectID              int64    `yaml:"project_id"`
	ProjectIDEnv           string   `yaml:"project_id_env"`
	SecretKey              string   `yaml:"secret_key"`
	SecretKeyEnv           string   `yaml:"secret_key_env"`
	AllowedCurrencies      []string `yaml:"allowed_currencies"`
	RequireCustomerAddress bool     `yaml:"require_customer_address"`
	RequestTimeoutSeconds  int      `yaml:"request_timeout_seconds"`
	StatusSuccess          string   `yaml:"status_success"`
	StatusProcessing       string   `yaml:"status_processing"`
}

type gatewayConfig struct {
	ID         string       `yaml:"id"`
	Network    string       `yaml:"network"`
	Currencies []string     `yaml:"currencies"`
	IsEnabled  *bool        `yaml:"is_enabled"`
	Limits     limitsConfig `yaml:"limits"`
}

type limitsConfig struct {
	MinAmount      string                       `yaml:"min_amount"`
	MaxAmount      string                       `yaml:"max_amount"`
	PerTxMaxFee    string                       `yaml:"per_tx_max_fee"`
	PerTxMinAmount string                       `yaml:"per_tx_min_amount"`
	PerTxMaxAmount string                       `yaml:"per_tx_max_amount"`
	VolumeLimit    map[string]string            `yaml:"volume_limit"`
	VelocityLimit  map[string]int               `yaml:"velocity_limit"`
	CurrencyLimits map[string]limitsOverrideCfg `yaml:"currency_limits"`
}

type limitsOverrideCfg struct {
	MaxVolume string `yaml:"max_volume"`
	MinAmount string `yaml:"min_amount"`
	MaxAmount string `yaml:"max_amount"`
	MaxFee    string `yaml:"max_fee"`
	MaxOps    int    `yaml:"max_ops"`
}

type httpConfig struct {
	Callback callbackConfig `yaml:"callback"`
}

type callbackConfig struct {
	Address      string   `yaml:"address"`
	Path         string   `yaml:"path"`
	AllowedCIDRs []string `yaml:"allowed_cidrs"`
	MaxBodyBytes int64    `yaml:"max_body_bytes"`
}

// Create initialises the Monetix gateway server implementation.
func Create(logger mlogger.Logger, file string, debug bool) (*Imp, error) {
	return &Imp{
		logger: logger.Named("server"),
		file:   file,
		debug:  debug,
	}, nil
}

func (i *Imp) Shutdown() {
	if i.app == nil {
		return
	}

	timeout := 15 * time.Second
	if i.config != nil && i.config.Runtime != nil {
		timeout = i.config.Runtime.ShutdownTimeout()
	}

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	if i.service != nil {
		i.service.Shutdown()
	}
	if i.http != nil {
		_ = i.http.Shutdown(ctx)
		i.http = nil
	}

	i.app.Shutdown(ctx)
}

func (i *Imp) Start() error {
	i.logger.Info("Starting Monetix gateway", zap.String("config_file", i.file), zap.Bool("debug", i.debug))

	cfg, err := i.loadConfig()
	if err != nil {
		return err
	}
	i.config = cfg

	i.logger.Info("Configuration loaded",
		zap.String("grpc_address", cfg.GRPC.Address),
		zap.String("metrics_address", cfg.Metrics.Address),
	)

	monetixCfg, err := i.resolveMonetixConfig(cfg.Monetix)
	if err != nil {
		i.logger.Error("Failed to resolve Monetix configuration", zap.Error(err))
		return err
	}

	callbackCfg, err := i.resolveCallbackConfig(cfg.HTTP.Callback)
	if err != nil {
		i.logger.Error("Failed to resolve callback configuration", zap.Error(err))
		return err
	}

	i.logger.Info("Monetix configuration resolved",
		zap.Bool("base_url_set", strings.TrimSpace(monetixCfg.BaseURL) != ""),
		zap.Int64("project_id", monetixCfg.ProjectID),
		zap.Bool("secret_key_set", strings.TrimSpace(monetixCfg.SecretKey) != ""),
		zap.Int("allowed_currencies", len(monetixCfg.AllowedCurrencies)),
		zap.Bool("require_customer_address", monetixCfg.RequireCustomerAddress),
		zap.Duration("request_timeout", monetixCfg.RequestTimeout),
		zap.String("status_success", monetixCfg.SuccessStatus()),
		zap.String("status_processing", monetixCfg.ProcessingStatus()),
	)

	gatewayDescriptor := resolveGatewayDescriptor(cfg.Gateway, monetixCfg)
	if gatewayDescriptor != nil {
		i.logger.Info("Gateway descriptor resolved",
			zap.String("id", gatewayDescriptor.GetId()),
			zap.String("rail", gatewayDescriptor.GetRail().String()),
			zap.String("network", gatewayDescriptor.GetNetwork()),
			zap.Int("currencies", len(gatewayDescriptor.GetCurrencies())),
			zap.Bool("enabled", gatewayDescriptor.GetIsEnabled()),
		)
	}

	i.logger.Info("Callback configuration resolved",
		zap.String("address", callbackCfg.Address),
		zap.String("path", callbackCfg.Path),
		zap.Int("allowed_cidrs", len(callbackCfg.AllowedCIDRs)),
		zap.Int64("max_body_bytes", callbackCfg.MaxBodyBytes),
	)

	serviceFactory := func(logger mlogger.Logger, _ struct{}, producer msg.Producer) (grpcapp.Service, error) {
		invokeURI := ""
		if cfg.GRPC != nil {
			invokeURI = cfg.GRPC.DiscoveryInvokeURI()
		}
		svc := mntxservice.NewService(logger,
			mntxservice.WithDiscoveryInvokeURI(invokeURI),
			mntxservice.WithProducer(producer),
			mntxservice.WithMonetixConfig(monetixCfg),
			mntxservice.WithGatewayDescriptor(gatewayDescriptor),
			mntxservice.WithHTTPClient(&http.Client{Timeout: monetixCfg.Timeout()}),
		)
		i.service = svc

		if err := i.startHTTPCallbackServer(svc, callbackCfg); err != nil {
			return nil, err
		}

		return svc, nil
	}

	app, err := grpcapp.NewApp(i.logger, "monetix", cfg.Config, i.debug, nil, serviceFactory)
	if err != nil {
		return err
	}
	i.app = app

	return i.app.Start()
}

func (i *Imp) loadConfig() (*config, error) {
	data, err := os.ReadFile(i.file)
	if err != nil {
		i.logger.Error("Could not read configuration file", zap.String("config_file", i.file), zap.Error(err))
		return nil, err
	}

	cfg := &config{
		Config: &grpcapp.Config{},
	}
	if err := yaml.Unmarshal(data, cfg); err != nil {
		i.logger.Error("Failed to parse configuration", zap.Error(err))
		return nil, err
	}

	if cfg.Runtime == nil {
		cfg.Runtime = &grpcapp.RuntimeConfig{ShutdownTimeoutSeconds: 15}
	}

	if cfg.GRPC == nil {
		cfg.GRPC = &routers.GRPCConfig{
			Network:          "tcp",
			Address:          ":50075",
			EnableReflection: true,
			EnableHealth:     true,
		}
	}

	if cfg.Metrics == nil {
		cfg.Metrics = &grpcapp.MetricsConfig{Address: ":9405"}
	}

	return cfg, nil
}

func (i *Imp) resolveMonetixConfig(cfg monetixConfig) (monetix.Config, error) {
	baseURL := strings.TrimSpace(cfg.BaseURL)
	if env := strings.TrimSpace(cfg.BaseURLEnv); env != "" {
		if val := strings.TrimSpace(os.Getenv(env)); val != "" {
			baseURL = val
		}
	}

	projectID := cfg.ProjectID
	if projectID == 0 && strings.TrimSpace(cfg.ProjectIDEnv) != "" {
		raw := strings.TrimSpace(os.Getenv(cfg.ProjectIDEnv))
		if raw != "" {
			if id, err := strconv.ParseInt(raw, 10, 64); err == nil {
				projectID = id
			} else {
				return monetix.Config{}, merrors.InvalidArgument("invalid project id in env "+cfg.ProjectIDEnv, "monetix.project_id")
			}
		}
	}

	secret := strings.TrimSpace(cfg.SecretKey)
	if env := strings.TrimSpace(cfg.SecretKeyEnv); env != "" {
		if val := strings.TrimSpace(os.Getenv(env)); val != "" {
			secret = val
		}
	}

	timeout := time.Duration(cfg.RequestTimeoutSeconds) * time.Second
	if timeout <= 0 {
		timeout = 15 * time.Second
	}

	statusSuccess := strings.TrimSpace(cfg.StatusSuccess)
	statusProcessing := strings.TrimSpace(cfg.StatusProcessing)

	return monetix.Config{
		BaseURL:                baseURL,
		ProjectID:              projectID,
		SecretKey:              secret,
		AllowedCurrencies:      cfg.AllowedCurrencies,
		RequireCustomerAddress: cfg.RequireCustomerAddress,
		RequestTimeout:         timeout,
		StatusSuccess:          statusSuccess,
		StatusProcessing:       statusProcessing,
	}, nil
}

func resolveGatewayDescriptor(cfg gatewayConfig, monetixCfg monetix.Config) *gatewayv1.GatewayInstanceDescriptor {
	id := strings.TrimSpace(cfg.ID)
	if id == "" {
		id = "monetix"
	}

	network := strings.ToUpper(strings.TrimSpace(cfg.Network))
	currencies := normalizeCurrencies(cfg.Currencies)
	if len(currencies) == 0 {
		currencies = normalizeCurrencies(monetixCfg.AllowedCurrencies)
	}

	enabled := true
	if cfg.IsEnabled != nil {
		enabled = *cfg.IsEnabled
	}

	limits := buildGatewayLimits(cfg.Limits)
	if limits == nil {
		limits = &gatewayv1.Limits{MinAmount: "0"}
	}

	version := strings.TrimSpace(appversion.Version)

	return &gatewayv1.GatewayInstanceDescriptor{
		Id:         id,
		Rail:       gatewayv1.Rail_RAIL_CARD_PAYOUT,
		Network:    network,
		Currencies: currencies,
		Capabilities: &gatewayv1.RailCapabilities{
			CanPayOut:              true,
			CanPayIn:               false,
			CanReadBalance:         false,
			CanSendFee:             false,
			RequiresObserveConfirm: true,
		},
		Limits:    limits,
		Version:   version,
		IsEnabled: enabled,
	}
}

func normalizeCurrencies(values []string) []string {
	if len(values) == 0 {
		return nil
	}
	seen := map[string]bool{}
	result := make([]string, 0, len(values))
	for _, value := range values {
		clean := strings.ToUpper(strings.TrimSpace(value))
		if clean == "" || seen[clean] {
			continue
		}
		seen[clean] = true
		result = append(result, clean)
	}
	return result
}

func buildGatewayLimits(cfg limitsConfig) *gatewayv1.Limits {
	hasValue := strings.TrimSpace(cfg.MinAmount) != "" ||
		strings.TrimSpace(cfg.MaxAmount) != "" ||
		strings.TrimSpace(cfg.PerTxMaxFee) != "" ||
		strings.TrimSpace(cfg.PerTxMinAmount) != "" ||
		strings.TrimSpace(cfg.PerTxMaxAmount) != "" ||
		len(cfg.VolumeLimit) > 0 ||
		len(cfg.VelocityLimit) > 0 ||
		len(cfg.CurrencyLimits) > 0
	if !hasValue {
		return nil
	}

	limits := &gatewayv1.Limits{
		MinAmount:      strings.TrimSpace(cfg.MinAmount),
		MaxAmount:      strings.TrimSpace(cfg.MaxAmount),
		PerTxMaxFee:    strings.TrimSpace(cfg.PerTxMaxFee),
		PerTxMinAmount: strings.TrimSpace(cfg.PerTxMinAmount),
		PerTxMaxAmount: strings.TrimSpace(cfg.PerTxMaxAmount),
	}

	if len(cfg.VolumeLimit) > 0 {
		limits.VolumeLimit = map[string]string{}
		for key, value := range cfg.VolumeLimit {
			bucket := strings.TrimSpace(key)
			amount := strings.TrimSpace(value)
			if bucket == "" || amount == "" {
				continue
			}
			limits.VolumeLimit[bucket] = amount
		}
	}

	if len(cfg.VelocityLimit) > 0 {
		limits.VelocityLimit = map[string]int32{}
		for key, value := range cfg.VelocityLimit {
			bucket := strings.TrimSpace(key)
			if bucket == "" {
				continue
			}
			limits.VelocityLimit[bucket] = int32(value)
		}
	}

	if len(cfg.CurrencyLimits) > 0 {
		limits.CurrencyLimits = map[string]*gatewayv1.LimitsOverride{}
		for key, override := range cfg.CurrencyLimits {
			currency := strings.ToUpper(strings.TrimSpace(key))
			if currency == "" {
				continue
			}
			limits.CurrencyLimits[currency] = &gatewayv1.LimitsOverride{
				MaxVolume: strings.TrimSpace(override.MaxVolume),
				MinAmount: strings.TrimSpace(override.MinAmount),
				MaxAmount: strings.TrimSpace(override.MaxAmount),
				MaxFee:    strings.TrimSpace(override.MaxFee),
				MaxOps:    int32(override.MaxOps),
			}
		}
	}

	return limits
}

type callbackRuntimeConfig struct {
	Address      string
	Path         string
	AllowedCIDRs []*net.IPNet
	MaxBodyBytes int64
}

func (i *Imp) resolveCallbackConfig(cfg callbackConfig) (callbackRuntimeConfig, error) {
	addr := strings.TrimSpace(cfg.Address)
	if addr == "" {
		addr = ":8084"
	}
	path := strings.TrimSpace(cfg.Path)
	if path == "" {
		path = "/monetix/callback"
	}
	maxBody := cfg.MaxBodyBytes
	if maxBody <= 0 {
		maxBody = 1 << 20 // 1MB
	}

	var cidrs []*net.IPNet
	for _, raw := range cfg.AllowedCIDRs {
		clean := strings.TrimSpace(raw)
		if clean == "" {
			continue
		}
		_, block, err := net.ParseCIDR(clean)
		if err != nil {
			i.logger.Warn("Invalid callback allowlist CIDR skipped", zap.String("cidr", clean), zap.Error(err))
			continue
		}
		cidrs = append(cidrs, block)
	}

	return callbackRuntimeConfig{
		Address:      addr,
		Path:         path,
		AllowedCIDRs: cidrs,
		MaxBodyBytes: maxBody,
	}, nil
}

func (i *Imp) startHTTPCallbackServer(svc *mntxservice.Service, cfg callbackRuntimeConfig) error {
	if svc == nil {
		return merrors.InvalidArgument("nil service provided for callback server")
	}
	if strings.TrimSpace(cfg.Address) == "" {
		i.logger.Info("Monetix callback server disabled: address is empty")
		return nil
	}

	router := chi.NewRouter()
	router.Post(cfg.Path, func(w http.ResponseWriter, r *http.Request) {
		log := i.logger.Named("callback_http")
		log.Debug("Callback request received",
			zap.String("remote_addr", strings.TrimSpace(r.RemoteAddr)),
			zap.String("path", r.URL.Path),
			zap.String("method", r.Method),
		)

		if len(cfg.AllowedCIDRs) > 0 && !clientAllowed(r, cfg.AllowedCIDRs) {
			ip := clientIPFromRequest(r)
			remoteIP := ""
			if ip != nil {
				remoteIP = ip.String()
			}
			log.Warn("Callback rejected by CIDR allowlist", zap.String("remote_ip", remoteIP))
			http.Error(w, "forbidden", http.StatusForbidden)
			return
		}
		body, err := io.ReadAll(io.LimitReader(r.Body, cfg.MaxBodyBytes))
		if err != nil {
			log.Warn("Callback body read failed", zap.Error(err))
			http.Error(w, "failed to read body", http.StatusBadRequest)
			return
		}
		status, err := svc.ProcessMonetixCallback(r.Context(), body)
		if err != nil {
			log.Warn("Callback processing failed", zap.Error(err), zap.Int("status", status))
			http.Error(w, err.Error(), status)
			return
		}
		log.Debug("Callback processed", zap.Int("status", status))
		w.WriteHeader(status)
	})

	server := &http.Server{
		Addr:    cfg.Address,
		Handler: router,
	}

	ln, err := net.Listen("tcp", cfg.Address)
	if err != nil {
		return err
	}

	i.http = server

	go func() {
		if err := server.Serve(ln); err != nil && !errors.Is(err, http.ErrServerClosed) {
			i.logger.Warn("Monetix callback server stopped with error", zap.Error(err))
		}
	}()

	i.logger.Info("Monetix callback server listening", zap.String("address", cfg.Address), zap.String("path", cfg.Path))
	return nil
}

func clientAllowed(r *http.Request, cidrs []*net.IPNet) bool {
	if len(cidrs) == 0 {
		return true
	}

	host := clientIPFromRequest(r)
	if host == nil {
		return false
	}
	for _, block := range cidrs {
		if block.Contains(host) {
			return true
		}
	}
	return false
}

func clientIPFromRequest(r *http.Request) net.IP {
	if r == nil {
		return nil
	}
	if xfwd := strings.TrimSpace(r.Header.Get("X-Forwarded-For")); xfwd != "" {
		parts := strings.Split(xfwd, ",")
		if len(parts) > 0 {
			if ip := net.ParseIP(strings.TrimSpace(parts[0])); ip != nil {
				return ip
			}
		}
	}
	host, _, err := net.SplitHostPort(r.RemoteAddr)
	if err != nil {
		return nil
	}
	return net.ParseIP(host)
}