package service

import (
	"errors"
	"strings"

	"browser.local/platform/domain"
	"browser.local/platform/repo"
	"browser.local/platform/validator"
)

type AIProviderClient interface {
	Invoke(provider domain.AIProvider, request domain.AIInvocationRequest) (domain.AIProviderInvocationResult, error)
}

type MockAIProviderClient struct{}

func (MockAIProviderClient) Invoke(provider domain.AIProvider, request domain.AIInvocationRequest) (domain.AIProviderInvocationResult, error) {
	model := request.Model
	if model == "" {
		model = provider.DefaultModel
	}
	if model == "" && len(provider.Models) > 0 {
		model = provider.Models[0]
	}
	recommendation := "Mock AI recommendation for " + request.Purpose + ": review the proposed change before dispatch."
	result := domain.AIProviderInvocationResult{
		Recommendation: recommendation,
		Usage: domain.AIInvocationUsage{
			ProviderID:   provider.ID,
			Model:        model,
			InputTokens:  boundedTokenEstimate(request.Prompt + request.CurrentConfig),
			OutputTokens: boundedTokenEstimate(recommendation),
			Mocked:       true,
		},
	}
	if request.Purpose == "config.suggest" || request.Purpose == "config.generate" {
		result.SuggestedConfig = buildSuggestedConfig(request.CurrentConfig, request.Prompt)
	}
	return result, nil
}

func (svc *CoreService) InvokeAIForSession(sessionID string, request domain.AIInvocationRequest) (domain.AIInvocationResponse, error) {
	request = domain.CopyAIInvocationRequest(request)
	if err := validator.ValidateAIInvocationRequest(request); err != nil {
		return domain.AIInvocationResponse{}, err
	}
	if _, err := svc.GetCurrentUser(sessionID); err != nil {
		return domain.AIInvocationResponse{}, err
	}
	if request.ServerInstanceID != "" {
		instance, err := svc.GetServerInstanceForSession(sessionID, request.ServerInstanceID)
		if err != nil {
			return domain.AIInvocationResponse{}, err
		}
		if request.PluginID != "" && instance.PluginID != request.PluginID {
			return safeAIDenial(request, "plugin scope does not match server instance"), nil
		}
	}
	if request.PluginID != "" {
		plugin, err := svc.store.GamePlugins().Get(request.PluginID)
		if err != nil {
			return domain.AIInvocationResponse{}, err
		}
		authorization, err := validator.AuthorizePluginBridgeAction(plugin, domain.PluginBridgeAuthorizeRequest{
			PluginID:         request.PluginID,
			RouteKey:         request.RouteKey,
			ServerInstanceID: request.ServerInstanceID,
			Action:           domain.PluginBridgeActionAIInvoke,
			AIPurpose:        request.Purpose,
		})
		if err != nil {
			return domain.AIInvocationResponse{}, err
		}
		if !authorization.Allowed {
			return safeAIDenial(request, authorization.Reason), nil
		}
	}
	provider, err := svc.selectAIProvider(request.ProviderID)
	if err != nil {
		return domain.AIInvocationResponse{}, err
	}
	result, err := svc.aiProviderClient.Invoke(provider, request)
	if err != nil {
		return domain.CopyAIInvocationResponse(domain.AIInvocationResponse{
			RequestID:  request.RequestID,
			Purpose:    request.Purpose,
			ProviderID: provider.ID,
			Model:      safeModel(request.Model, provider),
			Status:     "error",
			Usage:      domain.AIInvocationUsage{ProviderID: provider.ID, Model: safeModel(request.Model, provider), Mocked: true},
			Error:      &domain.AIInvocationSafeError{Code: "provider_failed", Message: safeBridgeReason(err.Error())},
		}), nil
	}
	response := domain.AIInvocationResponse{
		RequestID:      request.RequestID,
		Purpose:        request.Purpose,
		ProviderID:     provider.ID,
		Model:          result.Usage.Model,
		Status:         "ok",
		Recommendation: result.Recommendation,
		Usage:          result.Usage,
	}
	if result.SuggestedConfig != "" {
		response.ConfigRecommendation = &domain.AIConfigRecommendation{Key: "server.properties", SuggestedConfig: result.SuggestedConfig, DiffSummary: "review required before config write dispatch"}
	}
	if err := validator.ValidateAIInvocationResponse(response); err != nil {
		return domain.AIInvocationResponse{}, err
	}
	return domain.CopyAIInvocationResponse(response), nil
}

func (svc *CoreService) selectAIProvider(id string) (domain.AIProvider, error) {
	if id != "" {
		provider, err := svc.store.AIProviders().Get(id)
		if err != nil {
			return domain.AIProvider{}, err
		}
		if provider.Status != domain.AIProviderStatusActive {
			return domain.AIProvider{}, ErrForbidden
		}
		return provider, nil
	}
	providers, err := svc.store.AIProviders().List(domain.AIProviderFilter{Status: domain.AIProviderStatusActive})
	if err != nil {
		return domain.AIProvider{}, err
	}
	if len(providers) == 0 {
		return domain.AIProvider{}, repo.ErrNotFound
	}
	return providers[0], nil
}

func safeAIDenial(request domain.AIInvocationRequest, reason string) domain.AIInvocationResponse {
	return domain.CopyAIInvocationResponse(domain.AIInvocationResponse{
		RequestID: request.RequestID,
		Purpose:   request.Purpose,
		Status:    "denied",
		Error:     &domain.AIInvocationSafeError{Code: "permission_denied", Message: safeBridgeReason(reason)},
	})
}

func safeModel(model string, provider domain.AIProvider) string {
	if strings.TrimSpace(model) != "" {
		return model
	}
	if provider.DefaultModel != "" {
		return provider.DefaultModel
	}
	if len(provider.Models) > 0 {
		return provider.Models[0]
	}
	return "mock-model"
}

func buildSuggestedConfig(currentConfig string, prompt string) string {
	base := strings.TrimRight(currentConfig, "\n")
	if base == "" {
		base = "# generated server config"
	}
	if strings.Contains(strings.ToLower(prompt), "pvp") && !strings.Contains(base, "pvp=") {
		base += "\npvp=false"
	}
	return base + "\n# ai.recommendation=review-required\n"
}

func boundedTokenEstimate(value string) int {
	count := len([]rune(value)) / 4
	if count < 1 {
		return 1
	}
	if count > 4096 {
		return 4096
	}
	return count
}

type failingAIProviderClient struct{ err error }

func (client failingAIProviderClient) Invoke(domain.AIProvider, domain.AIInvocationRequest) (domain.AIProviderInvocationResult, error) {
	if client.err == nil {
		return domain.AIProviderInvocationResult{}, errors.New("provider failed")
	}
	return domain.AIProviderInvocationResult{}, client.err
}