package op

import (
	"context"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"time"

	"github.com/dexidp/dex/server"
	dexstorage "github.com/dexidp/dex/storage"
	"github.com/dexidp/dex/storage/memory"
	"github.com/mitchellh/mapstructure"
	"github.com/rs/zerolog/log"
	"github.com/spf13/viper"
	"gitlab.com/mobicoop/solidarity/services/mobility-accounts/handlers"
	maconnector "gitlab.com/mobicoop/solidarity/services/mobility-accounts/oidc-provider/connector"
	"gitlab.com/mobicoop/solidarity/services/mobility-accounts/storage"
)

// OIDCConfig holds the full OIDC provider configuration, decoded from viper.
type OIDCConfig struct {
	Enable     bool
	Port       string
	BaseURL    string `mapstructure:"base_url"`
	Namespaces map[string]OIDCNamespaceConfig
}

// OIDCNamespaceConfig holds per-namespace OIDC settings.
type OIDCNamespaceConfig struct {
	Namespace    string
	SecretKey    string            `mapstructure:"secret_key"`
	TemplatesDir string            `mapstructure:"templates_dir"`
	MatchClaims  map[string]string `mapstructure:"match_claims"`
	Clients      []OIDCClient
}

// OIDCClient represents a static OIDC client.
type OIDCClient struct {
	ID            string
	OIDC          bool
	Secret        string
	RedirectURIs  []string `mapstructure:"redirect_uris"`
	ResponseTypes []string `mapstructure:"response_types"`
	GrantTypes    []string `mapstructure:"grant_types"`
	Scopes        []string
	Audience      []string
	Public        bool
	//OIDC specific
	TokenEndpointAuthMethod string `mapstructure:"token_endpoint_auth_method"`
}

// NewDexServer creates an http.ServeMux that hosts one Dex OIDC server per namespace.
// Each namespace is mounted at /{namespaceName}/ and has its own storage, clients,
// and connector instance.
func NewDexServer(handler *handlers.MobilityAccountsHandler, stor storage.Storage, cfg *viper.Viper) (*http.ServeMux, error) {
	var oidcConfig OIDCConfig
	mapstructure.Decode(cfg.Get("services.oidc_provider").(map[string]any), &oidcConfig)

	baseURL := oidcConfig.BaseURL
	if baseURL == "" {
		protocol := "https"
		if cfg.GetBool("dev_env") {
			protocol = "http"
		}
		baseURL = fmt.Sprintf("%s://0.0.0.0:%s", protocol, cfg.GetString("services.oidc_provider.port"))
	}

	mux := http.NewServeMux()
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelInfo}))

	// Register our custom connector type in Dex's global registry
	server.ConnectorsConfig["mobilityaccounts"] = func() server.ConnectorConfig {
		return &maconnector.Config{
			Handler:   handler,
			Storage:   stor,
			Namespace: "", // will be set per-namespace below
		}
	}

	for nsName, nsCfg := range oidcConfig.Namespaces {
		dexServer, err := createNamespaceDexServer(handler, stor, nsCfg, nsName, baseURL, logger)
		if err != nil {
			return nil, fmt.Errorf("failed to create Dex server for namespace %q: %w", nsName, err)
		}

		prefix := "/" + nsName
		mux.Handle(prefix+"/", dexServer)
	}

	return mux, nil
}

// createNamespaceDexServer builds a single Dex server.Server for one namespace.
func createNamespaceDexServer(handler *handlers.MobilityAccountsHandler, stor storage.Storage, nsCfg OIDCNamespaceConfig, nsName, baseURL string, logger *slog.Logger) (*server.Server, error) {
	ctx := context.Background()

	// In-memory Dex storage
	dexStore := memory.New(logger)

	// Register static clients
	clients := buildDexClients(nsCfg.Clients)
	dexStore = dexstorage.WithStaticClients(dexStore, clients)

	// Register the connector — we override ConnectorsConfig factory for this namespace
	// so that Open() will get the right handler/storage/namespace.
	server.ConnectorsConfig["mobilityaccounts"] = func() server.ConnectorConfig {
		return &maconnector.Config{
			Handler:   handler,
			Storage:   stor,
			Namespace: nsCfg.Namespace,
		}
	}

	conn := dexstorage.Connector{
		ID:   "mobilityaccounts",
		Type: "mobilityaccounts",
		Name: "Mobility Accounts",
	}
	dexStore = dexstorage.WithStaticConnectors(dexStore, []dexstorage.Connector{conn})

	issuer := fmt.Sprintf("%s/%s", baseURL, nsName)

	// Determine web config
	webCfg := server.WebConfig{
		Issuer: nsName,
	}
	if nsCfg.TemplatesDir != "" {
		webCfg.Dir = nsCfg.TemplatesDir
	}

	// Dex v2.42 manages signing keys internally via storage.
	dexServer, err := server.NewServer(ctx, server.Config{
		Issuer:             issuer,
		Storage:            dexStore,
		SkipApprovalScreen: true,
		IDTokensValidFor:   30 * time.Hour,
		Web:                webCfg,
		Logger:             logger,
		Now:                time.Now,
	})
	if err != nil {
		return nil, fmt.Errorf("failed to create Dex server: %w", err)
	}

	return dexServer, nil
}

// buildDexClients converts the config OIDCClient list to Dex storage.Client list.
func buildDexClients(clients []OIDCClient) []dexstorage.Client {
	dexClients := make([]dexstorage.Client, 0, len(clients))
	for _, c := range clients {
		dexClients = append(dexClients, dexstorage.Client{
			ID:           c.ID,
			Secret:       c.Secret,
			RedirectURIs: c.RedirectURIs,
			Public:       c.Public,
			Name:         c.ID,
		})
	}
	return dexClients
}

// Run starts the OIDC provider HTTP server. Called from main.go as a goroutine.
func Run(done chan error, cfg *viper.Viper, handler handlers.MobilityAccountsHandler, stor storage.Storage) {
	address := "0.0.0.0:" + cfg.GetString("services.oidc_provider.port")
	log.Info().Str("address", address).Msg("Running Dex OIDC provider")

	mux, err := NewDexServer(&handler, stor, cfg)
	if err != nil {
		log.Error().Err(err).Msg("Failed to create Dex OIDC server")
		done <- err
		return
	}

	srv := &http.Server{
		Handler:      mux,
		Addr:         address,
		WriteTimeout: 15 * time.Second,
		ReadTimeout:  15 * time.Second,
	}

	err = srv.ListenAndServe()
	if err != nil {
		log.Error().Err(err).Msg("Dex OIDC server ended")
	}
	done <- err
}