package teachingassets

import (
	"errors"
	"fmt"
	"strings"
	"sync/atomic"
	"time"

	"tutor/internal/ontology"
	"tutor/internal/workflows"
)

type Service struct {
	store         Store
	ontology      *ontology.Service
	imageModelKey string
	ids           atomic.Uint64
}

func NewService(store Store, ontology *ontology.Service, imageModelKey string) *Service {
	return &Service{
		store:         store,
		ontology:      ontology,
		imageModelKey: imageModelKey,
	}
}

func (s *Service) GeneratePrompt(input GenerateInput) (PromptCandidate, error) {
	if strings.TrimSpace(input.ConceptID) == "" {
		return PromptCandidate{}, errors.New("concept_id is required")
	}
	assetType := input.AssetType
	if assetType == "" {
		assetType = workflows.AssetDiagram
	}

	concept, err := s.findConcept(input.ConceptID)
	if err != nil {
		return PromptCandidate{}, err
	}
	if len(concept.Evidence) == 0 {
		return PromptCandidate{}, errors.New("concept has no source evidence")
	}

	prompt := PromptCandidate{
		ID:                          s.nextID("asset-prompt"),
		Concept:                     concept.Concept,
		AssetType:                   assetType,
		Prompt:                      buildPrompt(concept.Concept, assetType),
		SourceEvidence:              append([]workflows.EvidenceRef(nil), concept.Evidence...),
		ModelKey:                    s.imageModelKey,
		RequiresModelIDVerification: true,
		ReviewState:                 ReviewCandidate,
		CreatedAt:                   time.Now().UTC(),
	}
	return s.store.SavePrompt(prompt)
}

func (s *Service) Snapshot() Snapshot {
	return s.store.Snapshot()
}

func (s *Service) findConcept(id string) (ontology.ConceptCandidate, error) {
	if s.ontology == nil {
		return ontology.ConceptCandidate{}, errors.New("ontology not configured")
	}
	snapshot := s.ontology.Snapshot()
	for _, concept := range snapshot.Concepts {
		if concept.Concept.ID == id {
			return concept, nil
		}
	}
	return ontology.ConceptCandidate{}, errors.New("concept not found")
}

func buildPrompt(concept workflows.ConceptRef, assetType workflows.AssetType) string {
	switch assetType {
	case workflows.AssetLessonSlice:
		return "Create a concise slide-like lesson slice explaining " + concept.Label +
			" for a backend developer interview, with one example and one pitfall."
	case workflows.AssetWorksheet:
		return "Create a worksheet for practicing " + concept.Label +
			" with short prompts, answer space, and a rubric."
	case workflows.AssetInterviewCard:
		return "Create an interview explanation card for " + concept.Label +
			" with definition, production tradeoff, and follow-up question."
	default:
		return "Create a clear technical diagram explaining " + concept.Label +
			" for a backend developer interview, grounded in the provided source evidence."
	}
}

func (s *Service) nextID(prefix string) string {
	return fmt.Sprintf("%s-%d", prefix, s.ids.Add(1))
}