// Filename: internal/service/resource_service.go

package service

import (
	"context"
	"errors"
	apperrors "gemini-balancer/internal/errors"
	"gemini-balancer/internal/models"
	"gemini-balancer/internal/repository"
	"gemini-balancer/internal/settings"
	"sort"
	"sync"
	"time"

	"github.com/sirupsen/logrus"
)

var (
	ErrNoResourceAvailable = errors.New("no available resource found for the request")
)

type RequestResources struct {
	KeyGroup         *models.KeyGroup
	APIKey           *models.APIKey
	UpstreamEndpoint *models.UpstreamEndpoint
	ProxyConfig      *models.ProxyConfig
	RequestConfig    *models.RequestConfig
}

type ResourceService struct {
	settingsManager *settings.SettingsManager
	groupManager    *GroupManager
	keyRepo         repository.KeyRepository
	apiKeyService   *APIKeyService
	logger          *logrus.Entry
	initOnce        sync.Once
}

func NewResourceService(
	sm *settings.SettingsManager,
	gm *GroupManager,
	kr repository.KeyRepository,
	aks *APIKeyService,
	logger *logrus.Logger,
) *ResourceService {
	rs := &ResourceService{
		settingsManager: sm,
		groupManager:    gm,
		keyRepo:         kr,
		apiKeyService:   aks,
		logger:          logger.WithField("component", "ResourceService📦️"),
	}

	rs.initOnce.Do(func() {
		go rs.preWarmCache(logger)
	})
	return rs
}

func (s *ResourceService) GetResourceFromBasePool(ctx context.Context, authToken *models.AuthToken, modelName string) (*RequestResources, error) {
	log := s.logger.WithFields(logrus.Fields{"token_id": authToken.ID, "model_name": modelName, "mode": "BasePool"})
	log.Debug("Entering BasePool resource acquisition.")

	candidateGroups := s.filterAndSortCandidateGroups(modelName, authToken.AllowedGroups)
	if len(candidateGroups) == 0 {
		log.Warn("No candidate groups found for BasePool construction.")
		return nil, apperrors.ErrNoKeysAvailable
	}

	basePool := &repository.BasePool{
		CandidateGroups: candidateGroups,
		PollingStrategy: s.settingsManager.GetSettings().PollingStrategy,
	}

	apiKey, selectedGroup, err := s.keyRepo.SelectOneActiveKeyFromBasePool(ctx, basePool)
	if err != nil {
		log.WithError(err).Warn("Failed to select a key from the BasePool.")
		return nil, apperrors.ErrNoKeysAvailable
	}

	resources, err := s.assembleRequestResources(selectedGroup, apiKey)
	if err != nil {
		log.WithError(err).Error("Failed to assemble resources after selecting key from BasePool.")
		return nil, err
	}
	resources.RequestConfig = &models.RequestConfig{}
	log.Infof("Successfully selected KeyID %d from GroupID %d for the BasePool.", apiKey.ID, selectedGroup.ID)
	return resources, nil
}

func (s *ResourceService) GetResourceFromGroup(ctx context.Context, authToken *models.AuthToken, groupName string) (*RequestResources, error) {
	log := s.logger.WithFields(logrus.Fields{"token_id": authToken.ID, "group_name": groupName, "mode": "PreciseRoute"})
	log.Debug("Entering PreciseRoute resource acquisition.")

	targetGroup, ok := s.groupManager.GetGroupByName(groupName)

	if !ok {
		return nil, apperrors.NewAPIError(apperrors.ErrGroupNotFound, "The specified group does not exist.")
	}
	if !s.isTokenAllowedForGroup(authToken, targetGroup.ID) {
		return nil, apperrors.NewAPIError(apperrors.ErrPermissionDenied, "Token does not have permission to access this group.")
	}

	apiKey, _, err := s.keyRepo.SelectOneActiveKey(ctx, targetGroup)
	if err != nil {
		log.WithError(err).Warn("Failed to select a key from the precisely targeted group.")
		return nil, apperrors.ErrNoKeysAvailable
	}

	resources, err := s.assembleRequestResources(targetGroup, apiKey)
	if err != nil {
		log.WithError(err).Error("Failed to assemble resources for precise route.")
		return nil, err
	}
	resources.RequestConfig = targetGroup.RequestConfig

	log.Infof("Successfully selected KeyID %d by precise routing to GroupID %d.", apiKey.ID, targetGroup.ID)
	return resources, nil
}

func (s *ResourceService) GetAllowedModelsForToken(authToken *models.AuthToken) []string {
	allGroups := s.groupManager.GetAllGroups()
	if len(allGroups) == 0 {
		return []string{}
	}
	allowedModelsSet := make(map[string]struct{})
	if authToken.IsAdmin {
		for _, group := range allGroups {
			for _, modelMapping := range group.AllowedModels {
				allowedModelsSet[modelMapping.ModelName] = struct{}{}
			}
		}
	} else {
		allowedGroupIDs := make(map[uint]bool)
		for _, ag := range authToken.AllowedGroups {
			allowedGroupIDs[ag.ID] = true
		}
		for _, group := range allGroups {
			if _, ok := allowedGroupIDs[group.ID]; ok {
				for _, modelMapping := range group.AllowedModels {
					allowedModelsSet[modelMapping.ModelName] = struct{}{}
				}
			}
		}
	}
	result := make([]string, 0, len(allowedModelsSet))
	for modelName := range allowedModelsSet {
		result = append(result, modelName)
	}
	sort.Strings(result)
	return result
}

func (s *ResourceService) assembleRequestResources(group *models.KeyGroup, apiKey *models.APIKey) (*RequestResources, error) {
	selectedUpstream := s.selectUpstreamForGroup(group)
	if selectedUpstream == nil {
		return nil, apperrors.NewAPIError(apperrors.ErrConfigurationError, "Selected group has no valid upstream and no global default is set.")
	}
	var proxyConfig *models.ProxyConfig
	return &RequestResources{
		KeyGroup:         group,
		APIKey:           apiKey,
		UpstreamEndpoint: selectedUpstream,
		ProxyConfig:      proxyConfig,
	}, nil
}

func (s *ResourceService) selectUpstreamForGroup(group *models.KeyGroup) *models.UpstreamEndpoint {
	if len(group.AllowedUpstreams) > 0 {
		return group.AllowedUpstreams[0]
	}
	globalSettings := s.settingsManager.GetSettings()
	if globalSettings.DefaultUpstreamURL != "" {
		return &models.UpstreamEndpoint{URL: globalSettings.DefaultUpstreamURL, Status: "active"}
	}
	return nil
}

func (s *ResourceService) preWarmCache(logger *logrus.Logger) error {
	time.Sleep(2 * time.Second)
	s.logger.Info("Performing initial key cache pre-warming...")
	if err := s.keyRepo.LoadAllKeysToStore(context.Background()); err != nil {
		logger.WithError(err).Error("Failed to perform initial key cache pre-warming.")
		return err
	}
	s.logger.Info("Initial key cache pre-warming completed successfully.")
	return nil
}

func (s *ResourceService) GetResourcesForRequest(modelName string, allowedGroups []*models.KeyGroup) (*RequestResources, error) {
	return nil, errors.New("GetResourcesForRequest is deprecated; use GetResourceFromBasePool or GetResourceFromGroup")
}

func (s *ResourceService) filterAndSortCandidateGroups(modelName string, allowedGroupsFromToken []*models.KeyGroup) []*models.KeyGroup {
	allGroupsFromCache := s.groupManager.GetAllGroups()
	var candidateGroups []*models.KeyGroup
	allowedGroupIDs := make(map[uint]bool)
	isTokenRestricted := len(allowedGroupsFromToken) > 0
	if isTokenRestricted {
		for _, ag := range allowedGroupsFromToken {
			allowedGroupIDs[ag.ID] = true
		}
	}
	for _, group := range allGroupsFromCache {
		if isTokenRestricted && !allowedGroupIDs[group.ID] {
			continue
		}
		isModelAllowed := false
		if len(group.AllowedModels) == 0 {
			isModelAllowed = true
		} else {
			for _, m := range group.AllowedModels {
				if m.ModelName == modelName {
					isModelAllowed = true
					break
				}
			}
		}
		if isModelAllowed {
			candidateGroups = append(candidateGroups, group)
		}
	}
	sort.SliceStable(candidateGroups, func(i, j int) bool {
		return candidateGroups[i].Order < candidateGroups[j].Order
	})
	return candidateGroups
}

func (s *ResourceService) isTokenAllowedForGroup(authToken *models.AuthToken, groupID uint) bool {
	if authToken.IsAdmin {
		return true
	}
	for _, allowedGroup := range authToken.AllowedGroups {
		if allowedGroup.ID == groupID {
			return true
		}
	}
	return false
}

func (s *ResourceService) ReportRequestResult(resources *RequestResources, success bool, apiErr *apperrors.APIError) {
	if resources == nil || resources.KeyGroup == nil || resources.APIKey == nil {
		return
	}
	s.apiKeyService.HandleRequestResult(resources.KeyGroup, resources.APIKey, success, apiErr)
}