package control

import (
	"crypto/sha256"
	"crypto/subtle"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/sirupsen/logrus"

	"gpt-load/internal/platform/config"
	app_errors "gpt-load/internal/platform/errors"
	"gpt-load/internal/platform/i18n"
	"gpt-load/internal/platform/response"
	"gpt-load/internal/platform/utils"
)

type Server struct {
	authDigest        [sha256.Size]byte
	service           *Service
	systemInfo        systemInfoResponse
	authFailures      *authFailureLimiter
	compareDigest     func([]byte, []byte) int
	logger            *logrus.Logger
	authFailureEvents *utils.RateLimitedEventCounter
	startedAt         time.Time
	now               func() time.Time
}

const maxControlJSONBodyBytes int64 = 32 << 20

func NewServer(cfg *config.Config, service *Service) *Server {
	now := time.Now
	return &Server{
		authDigest:    sha256.Sum256([]byte(cfg.AuthKey)),
		service:       service,
		systemInfo:    newSystemInfoResponse(cfg),
		authFailures:  newAuthFailureLimiter(),
		compareDigest: subtle.ConstantTimeCompare,
		logger:        logrus.StandardLogger(),
		startedAt:     now().UTC(),
		now:           now,
		authFailureEvents: utils.NewRateLimitedEventCounter(
			time.Minute,
			time.Now,
		),
	}
}

func (s *Server) handleGetSettings(c *gin.Context) {
	result, err := s.service.GetSettings(c.Request.Context())
	if err != nil {
		writeServiceError(c, "get_settings", err)
		return
	}
	representation, err := newSettingsWireRepresentation(
		i18n.Message(c, "common.success"),
		result.DTO(),
	)
	if err != nil {
		writeServiceError(c, "get_settings", err)
		return
	}
	writeSettingsRepresentation(c, representation)
}

func (s *Server) handleUpdateSettings(c *gin.Context) {
	expectedETag, ok := requiredSettingsIfMatch(c)
	if !ok {
		return
	}
	var request SettingsUpdateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "update_settings", mapControlJSONError(err))
		return
	}
	result, err := s.service.UpdateSettingsIfMatch(
		c.Request.Context(),
		request,
		expectedETag,
		i18n.Message(c, "common.success"),
	)
	if err != nil {
		writeServiceError(c, "update_settings", err)
		return
	}
	writeSettingsRepresentation(c, result)
}

func (s *Server) handleGetGroupSummary(c *gin.Context) {
	id, ok := groupID(c, "get_group_summary")
	if !ok {
		return
	}
	result, err := s.service.GetGroupSummary(c.Request.Context(), id)
	if err != nil {
		writeServiceError(c, "get_group_summary", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleGetGroupSettings(c *gin.Context) {
	id, ok := groupID(c, "get_group_settings")
	if !ok {
		return
	}
	result, err := s.service.GetGroupSettings(c.Request.Context(), id)
	if err != nil {
		writeServiceError(c, "get_group_settings", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleCreateGroup(c *gin.Context) {
	idempotencyKey, ok := requiredIdempotencyKey(c, "create_group")
	if !ok {
		return
	}
	var request GroupCreateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "create_group", mapControlJSONError(err))
		return
	}
	result, err := s.service.CreateGroupIdempotent(
		c.Request.Context(),
		idempotencyKey,
		request,
	)
	if err != nil {
		writeServiceError(c, "create_group", err)
		return
	}
	setMutationResourceLocator(
		c,
		fmt.Sprintf("group:%d", result.GroupID),
	)
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleUpdateGroupSettings(c *gin.Context) {
	id, ok := groupID(c, "update_group_settings")
	if !ok {
		return
	}
	var request GroupSettingsUpdateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "update_group_settings", mapControlJSONError(err))
		return
	}
	result, err := s.service.UpdateGroupSettings(c.Request.Context(), id, request)
	if err != nil {
		writeServiceError(c, "update_group_settings", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleUpdateGroupModels(c *gin.Context) {
	id, ok := groupID(c, "update_group_models")
	if !ok {
		return
	}
	var request GroupModelsUpdateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "update_group_models", mapControlJSONError(err))
		return
	}
	result, err := s.service.UpdateGroupModels(c.Request.Context(), id, request)
	if err != nil {
		writeServiceError(c, "update_group_models", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleGetGroupModels(c *gin.Context) {
	id, ok := groupID(c, "get_group_models")
	if !ok {
		return
	}
	result, err := s.service.GetGroupModels(c.Request.Context(), id)
	if err != nil {
		writeServiceError(c, "get_group_models", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleDeleteGroup(c *gin.Context) {
	id, ok := groupID(c, "delete_group")
	if !ok {
		return
	}
	if err := s.service.DeleteGroup(c.Request.Context(), id); err != nil {
		writeServiceError(c, "delete_group", err)
		return
	}
	response.SuccessI18n(c, "common.success", nil)
}

func (s *Server) handleListGroupCredentials(c *gin.Context) {
	id, ok := groupID(c, "list_group_credentials")
	if !ok {
		return
	}
	query, apiErr := parseCredentialCollectionQuery(c.Request.URL.RawQuery)
	if apiErr != nil {
		writeServiceError(c, "list_group_credentials", apiErr)
		return
	}
	result, err := s.service.ListGroupCredentials(c.Request.Context(), id, query)
	if err != nil {
		writeServiceError(c, "list_group_credentials", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleRevealGroupCredential(c *gin.Context) {
	groupID, ok := groupID(c, "reveal_group_credential")
	if !ok {
		return
	}
	credentialID, ok := credentialID(c, "reveal_group_credential")
	if !ok {
		return
	}
	if err := bindOptionalEmptyJSONObject(c); err != nil {
		writeServiceError(c, "reveal_group_credential", mapControlJSONError(err))
		return
	}
	result, err := s.service.RevealGroupCredential(c.Request.Context(), groupID, credentialID)
	if err != nil {
		writeServiceError(c, "reveal_group_credential", err)
		return
	}
	setSecretResponseHeaders(c)
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleUpdateGroupCredential(c *gin.Context) {
	groupID, ok := groupID(c, "update_group_credential")
	if !ok {
		return
	}
	credentialID, ok := credentialID(c, "update_group_credential")
	if !ok {
		return
	}
	var request CredentialUpdateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "update_group_credential", mapControlJSONError(err))
		return
	}
	result, err := s.service.UpdateGroupCredential(c.Request.Context(), groupID, credentialID, request)
	if err != nil {
		writeServiceError(c, "update_group_credential", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleDeleteGroupCredential(c *gin.Context) {
	groupID, ok := groupID(c, "delete_group_credential")
	if !ok {
		return
	}
	credentialID, ok := credentialID(c, "delete_group_credential")
	if !ok {
		return
	}
	if err := bindOptionalEmptyJSONObject(c); err != nil {
		writeServiceError(c, "delete_group_credential", mapControlJSONError(err))
		return
	}
	if err := s.service.DeleteGroupCredential(c.Request.Context(), groupID, credentialID); err != nil {
		writeServiceError(c, "delete_group_credential", err)
		return
	}
	response.SuccessI18n(c, "common.success", nil)
}

func (s *Server) handleRestoreGroupCredential(c *gin.Context) {
	groupID, ok := groupID(c, "restore_group_credential")
	if !ok {
		return
	}
	credentialID, ok := credentialID(c, "restore_group_credential")
	if !ok {
		return
	}
	if err := bindOptionalEmptyJSONObject(c); err != nil {
		writeServiceError(c, "restore_group_credential", mapControlJSONError(err))
		return
	}
	result, err := s.service.RestoreGroupCredential(c.Request.Context(), groupID, credentialID)
	if err != nil {
		writeServiceError(c, "restore_group_credential", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleBatchGroupCredentials(c *gin.Context) {
	groupID, ok := groupID(c, "batch_group_credentials")
	if !ok {
		return
	}
	var request CredentialBatchRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "batch_group_credentials", mapControlJSONError(err))
		return
	}
	result, err := s.service.BatchGroupCredentials(c.Request.Context(), groupID, request)
	if err != nil {
		writeServiceError(c, "batch_group_credentials", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleImportGroupCredentials(c *gin.Context) {
	id, ok := groupID(c, "import_group_credentials")
	if !ok {
		return
	}
	idempotencyKey, ok := requiredIdempotencyKey(c, "import_group_credentials")
	if !ok {
		return
	}
	var request CredentialImportRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "import_group_credentials", mapControlJSONError(err))
		return
	}
	result, err := s.service.ImportGroupCredentialsIdempotent(
		c.Request.Context(), idempotencyKey, id, request,
	)
	if err != nil {
		writeServiceError(c, "import_group_credentials", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleDiscoverGroupModels(c *gin.Context) {
	id, ok := groupID(c, "discover_group_models")
	if !ok {
		return
	}
	if err := bindOptionalEmptyJSONObject(c); err != nil {
		writeServiceError(c, "discover_group_models", mapControlJSONError(err))
		return
	}
	result, err := s.service.DiscoverGroupModels(c.Request.Context(), id)
	if err != nil {
		writeServiceError(c, "discover_group_models", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleDiscoverModels(c *gin.Context) {
	var request ModelDiscoveryRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeDiscoveryError(c, mapControlJSONError(err))
		return
	}
	result, err := s.service.DiscoverModels(c.Request.Context(), request)
	if err != nil {
		writeDiscoveryError(c, err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleCreateAccessKey(c *gin.Context) {
	idempotencyKey, ok := requiredIdempotencyKey(c, "create_access_key")
	if !ok {
		return
	}
	var request AccessKeyCreateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "create_access_key", mapControlJSONError(err))
		return
	}
	result, err := s.service.CreateAccessKeyIdempotent(
		c.Request.Context(),
		idempotencyKey,
		request,
	)
	if err != nil {
		writeServiceError(c, "create_access_key", err)
		return
	}
	setMutationResourceLocator(
		c,
		fmt.Sprintf("access-key:%d", result.ID),
	)
	setSecretResponseHeaders(c)
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleListAccessKeyOptions(c *gin.Context) {
	result, err := s.service.ListAccessKeyOptions(c.Request.Context())
	if err != nil {
		writeServiceError(c, "list_access_key_options", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleRevealAccessKey(c *gin.Context) {
	id, ok := accessKeyID(c)
	if !ok {
		return
	}
	result, err := s.service.RevealAccessKey(c.Request.Context(), id)
	if err != nil {
		writeServiceError(c, "reveal_access_key", err)
		return
	}
	setSecretResponseHeaders(c)
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleUpdateAccessKey(c *gin.Context) {
	id, ok := accessKeyID(c)
	if !ok {
		return
	}
	var request AccessKeyUpdateRequest
	if err := bindStrictJSON(c, &request); err != nil {
		writeServiceError(c, "update_access_key", mapControlJSONError(err))
		return
	}
	result, err := s.service.UpdateAccessKey(c.Request.Context(), id, request)
	if err != nil {
		writeServiceError(c, "update_access_key", err)
		return
	}
	response.SuccessI18n(c, "common.success", result)
}

func (s *Server) handleDeleteAccessKey(c *gin.Context) {
	id, ok := accessKeyID(c)
	if !ok {
		return
	}
	if err := s.service.DeleteAccessKey(c.Request.Context(), id); err != nil {
		writeServiceError(c, "delete_access_key", err)
		return
	}
	response.SuccessI18n(c, "common.success", nil)
}

func bindStrictJSON(c *gin.Context, target any) error {
	if c.Request.ContentLength > maxControlJSONBodyBytes {
		return &http.MaxBytesError{Limit: maxControlJSONBodyBytes}
	}
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, maxControlJSONBodyBytes)
	raw, err := io.ReadAll(c.Request.Body)
	if err != nil {
		return err
	}
	return decodeStrictControlJSONObject(raw, target)
}

func bindOptionalEmptyJSONObject(c *gin.Context) error {
	decoder, err := newControlJSONDecoder(c)
	if err != nil {
		return err
	}
	var object map[string]json.RawMessage
	if err := decoder.Decode(&object); err != nil {
		if errors.Is(err, io.EOF) {
			return nil
		}
		return err
	}
	if object == nil || len(object) != 0 {
		return fmt.Errorf("request body must be an empty JSON object")
	}
	var extra json.RawMessage
	if err := decoder.Decode(&extra); !errors.Is(err, io.EOF) {
		if err == nil {
			return fmt.Errorf("decode JSON request: multiple values")
		}
		return err
	}
	return nil
}

func newControlJSONDecoder(c *gin.Context) (*json.Decoder, error) {
	if c.Request.ContentLength > maxControlJSONBodyBytes {
		return nil, &http.MaxBytesError{Limit: maxControlJSONBodyBytes}
	}
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, maxControlJSONBodyBytes)
	return json.NewDecoder(c.Request.Body), nil
}

func mapControlJSONError(err error) *app_errors.APIError {
	if errors.Is(err, app_errors.ErrValidation) {
		return app_errors.ErrValidation
	}
	var maxBytesError *http.MaxBytesError
	if errors.As(err, &maxBytesError) {
		return app_errors.ErrRequestTooLarge
	}
	return app_errors.ErrInvalidJSON
}

func requiredIdempotencyKey(
	c *gin.Context,
	operation string,
) (string, bool) {
	values := c.Request.Header.Values("Idempotency-Key")
	if len(values) == 0 || len(values) == 1 && values[0] == "" {
		writeServiceError(c, operation, app_errors.ErrIdempotencyKeyRequired)
		return "", false
	}
	if len(values) != 1 || validateIdempotencyKey(values[0]) != nil {
		writeServiceError(c, operation, app_errors.ErrInvalidIdempotencyKey)
		return "", false
	}
	return values[0], true
}

func requiredSettingsIfMatch(c *gin.Context) (string, bool) {
	values := c.Request.Header.Values("If-Match")
	if len(values) == 0 || len(values) == 1 && values[0] == "" {
		writeServiceError(c, "update_settings", app_errors.ErrSettingsPreconditionRequired)
		return "", false
	}
	if len(values) != 1 {
		writeServiceError(c, "update_settings", app_errors.ErrBadRequest)
		return "", false
	}
	token, valid := parseSettingsHeaderETag(values[0])
	if !valid {
		writeServiceError(c, "update_settings", app_errors.ErrBadRequest)
		return "", false
	}
	return token, true
}

func writeSettingsRepresentation(
	c *gin.Context,
	representation settingsWireRepresentation,
) {
	c.Header("ETag", representation.HeaderETag)
	c.Header("Content-Language", i18n.GetLanguageFromContext(c))
	c.Header("Vary", "Accept-Language")
	c.Data(http.StatusOK, "application/json; charset=utf-8", representation.Body)
}

func setSecretResponseHeaders(c *gin.Context) {
	c.Header("Cache-Control", "no-store")
	c.Header("Pragma", "no-cache")
}

func accessKeyID(c *gin.Context) (uint, bool) {
	parsed, err := strconv.ParseUint(c.Param("id"), 10, strconv.IntSize)
	if err != nil || parsed == 0 {
		writeServiceError(c, "access_key_id", app_errors.ErrBadRequest)
		return 0, false
	}
	return uint(parsed), true
}

func groupID(c *gin.Context, operation string) (uint, bool) {
	parsed, err := strconv.ParseUint(c.Param("group_id"), 10, strconv.IntSize)
	if err != nil || parsed == 0 {
		writeServiceError(c, operation, app_errors.ErrBadRequest)
		return 0, false
	}
	return uint(parsed), true
}

func credentialID(c *gin.Context, operation string) (uint, bool) {
	parsed, err := strconv.ParseUint(c.Param("credential_id"), 10, strconv.IntSize)
	if err != nil || parsed == 0 {
		writeServiceError(c, operation, app_errors.ErrBadRequest)
		return 0, false
	}
	return uint(parsed), true
}

func writeServiceError(c *gin.Context, operation string, err error) {
	writeServiceErrorResponse(c, operation, err)
}

func writeDiscoveryError(c *gin.Context, err error) {
	writeServiceErrorResponse(c, "discover_models", err)
}

func writeServiceErrorResponse(
	c *gin.Context,
	operation string,
	err error,
) {
	var apiErr *app_errors.APIError
	if errors.As(err, &apiErr) {
		setMutationErrorCode(c, apiErr.Code)
		if apiErr.HTTPStatus >= http.StatusInternalServerError {
			logServiceError(operation, err, apiErr.Code)
		}
		response.ErrorI18nFromAPIError(
			c,
			apiErr,
			serviceErrorMessageID(operation, err, apiErr),
		)
		return
	}

	setMutationErrorCode(c, app_errors.ErrInternalServer.Code)
	logServiceError(operation, err, app_errors.ErrInternalServer.Code)
	response.ErrorI18nFromAPIError(c, app_errors.ErrInternalServer, "internal_error")
}

func serviceErrorMessageID(
	operation string,
	err error,
	apiErr *app_errors.APIError,
) string {
	switch apiErr.Code {
	case app_errors.ErrIdempotencyKeyRequired.Code:
		return "idempotency.required"
	case app_errors.ErrInvalidIdempotencyKey.Code:
		return "idempotency.invalid"
	case app_errors.ErrIdempotencyKeyReused.Code:
		return "idempotency.reused"
	case app_errors.ErrIdempotencyResultExpired.Code:
		return "idempotency.expired"
	case app_errors.ErrControlOperationIncomplete.Code:
		return "control.operation_incomplete"
	case app_errors.ErrControlRecoveryPending.Code:
		return "control.recovery_pending"
	case app_errors.ErrSettingsPreconditionRequired.Code:
		return "settings.precondition_required"
	case app_errors.ErrSettingsVersionConflict.Code:
		return "settings.version_conflict"
	case app_errors.ErrModelPriceUnpricedConfirmationRequired.Code:
		return "model_price.unpriced_confirmation_required"
	case app_errors.ErrModelPriceReferenced.Code:
		return "model_price.referenced"
	case app_errors.ErrModelPriceAutomaticDeleteForbidden.Code:
		return "model_price.automatic_delete_forbidden"
	case app_errors.ErrRequestTooLarge.Code:
		return "request_too_large"
	case app_errors.ErrBadRequest.Code, app_errors.ErrInvalidJSON.Code, app_errors.ErrValidation.Code:
		return "bad_request"
	case app_errors.ErrResourceNotFound.Code:
		switch operation {
		case "update_model_price", "reset_model_price", "delete_model_price":
			return "model_price.not_found"
		}
		var resourceErr *controlResourceNotFoundError
		if errors.As(err, &resourceErr) {
			if resourceErr.resource == "group" {
				return "group.not_found"
			}
			return "credential.not_found"
		}
		switch operation {
		case "list_groups", "get_group_summary", "get_group_settings", "get_group_models",
			"update_group_settings", "delete_group",
			"update_group_models", "import_group_credentials",
			"discover_group_models", "list_group_credentials":
			return "group.not_found"
		default:
			return "credential.not_found"
		}
	case app_errors.ErrNoActiveCredential.Code:
		return "group.no_active_credential"
	case app_errors.ErrDuplicateResource.Code:
		if operation == "create_group" || operation == "update_group_settings" {
			return "group.name_exists"
		}
		return "bad_request"
	case app_errors.ErrGroupInUse.Code:
		return "group.in_use"
	case app_errors.ErrChannelTargetConflict.Code:
		return "group.channel_target_conflict"
	case app_errors.ErrModelNameConflict.Code:
		return "group.model_name_conflict"
	case app_errors.ErrBadGateway.Code:
		return "bad_gateway"
	default:
		return "internal_error"
	}
}

func logServiceError(operation string, err error, code string) {
	fields := logrus.Fields{
		"operation":  operation,
		"error_code": code,
		"error_type": fmt.Sprintf("%T", err),
	}
	var operationErr *controlOperationError
	if errors.As(err, &operationErr) {
		if operationErr.stage != "" {
			fields["stage"] = operationErr.stage
		}
		if operationErr.mismatchKind != "" {
			fields["mismatch_kind"] = operationErr.mismatchKind
		}
		if operationErr.groupID != 0 {
			fields["group_id"] = operationErr.groupID
		}
		if operationErr.credentialID != 0 {
			fields["credential_id"] = operationErr.credentialID
		}
	}
	utils.LogPlaneBestEffort(
		logrus.StandardLogger(),
		logrus.ErrorLevel,
		utils.LogPlaneControl,
		fields,
		"Operation failed",
	)
}