package handlers

import (
	"encoding/json"
	"net/http"
	"strings"
)

// AIAccountingHandler hanterar AI-driven bokföringsförslag
type AIAccountingHandler struct{}

func NewAIAccountingHandler() *AIAccountingHandler {
	return &AIAccountingHandler{}
}

// AISuggestion representerar ett AI-förslag
type AISuggestion struct {
	ID          string  `json:"id"`
	Description string  `json:"description"`
	SuggestedAccount string `json:"suggested_account"`
	AccountName string  `json:"account_name"`
	Confidence  float64 `json:"confidence"`
	Debit       float64 `json:"debit"`
	Credit      float64 `json:"credit"`
	Reason      string  `json:"reason"`
}

// GetSuggestions returnerar AI-förslag för en transaktion
func (h *AIAccountingHandler) GetSuggestions(w http.ResponseWriter, r *http.Request) {
	var req struct {
		Description string  `json:"description"`
		Amount      float64 `json:"amount"`
		Counterparty string `json:"counterparty"`
	}

	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]interface{}{
			"ok":    false,
			"error": err.Error(),
		})
		return
	}

	suggestions := h.analyzeTransaction(req.Description, req.Amount, req.Counterparty)

	writeJSON(w, http.StatusOK, map[string]interface{}{
		"ok":          true,
		"suggestions": suggestions,
		"input":       req,
	})
}

// analyzeTransaction analyserar en transaktion och ger förslag
func (h *AIAccountingHandler) analyzeTransaction(description string, amount float64, counterparty string) []AISuggestion {
	desc := strings.ToLower(description)
	counter := strings.ToLower(counterparty)
	var suggestions []AISuggestion

	// Regelbaserad AI (kan bytas mot ML-modell)
	switch {
	case containsAny(desc, []string{"faktura", "inbetalning", "betalning"}) && amount > 0:
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-001",
			Description:      description,
			SuggestedAccount: "1510",
			AccountName:      "Kundfordringar",
			Confidence:       0.92,
			Debit:            amount,
			Credit:           0,
			Reason:           "Positivt belopp med fakturareferens = kundfordran",
		})
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-002",
			Description:      description,
			SuggestedAccount: "3010",
			AccountName:      "Försäljning tjänster",
			Confidence:       0.88,
			Debit:            0,
			Credit:           amount,
			Reason:           "Motkonto till kundfordran = försäljning",
		})

	case containsAny(desc, []string{"lön", "salary", "löneutbetalning"}):
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-003",
			Description:      description,
			SuggestedAccount: "7210",
			AccountName:      "Löner",
			Confidence:       0.95,
			Debit:            amount,
			Credit:           0,
			Reason:           "Löneutbetalning = lönekonto",
		})
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-004",
			Description:      description,
			SuggestedAccount: "1930",
			AccountName:      "Företagskonto",
			Confidence:       0.95,
			Debit:            0,
			Credit:           amount,
			Reason:           "Lön betalas från företagskonto",
		})

	case containsAny(desc, []string{"aws", "hosting", "server", "cloud"}):
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-005",
			Description:      description,
			SuggestedAccount: "6540",
			AccountName:      "IT-kostnader",
			Confidence:       0.89,
			Debit:            amount,
			Credit:           0,
			Reason:           "AWS/hosting = IT-kostnader",
		})

	case containsAny(desc, []string{"zoomer", "quixzoom", "fältarbetare"}):
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-006",
			Description:      description,
			SuggestedAccount: "7690",
			AccountName:      "Övriga personalkostnader",
			Confidence:       0.87,
			Debit:            amount,
			Credit:           0,
			Reason:           "Zoomer-utbetalning = personalkostnad",
		})

	case containsAny(desc, []string{"försäkring", "insurance"}):
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-007",
			Description:      description,
			SuggestedAccount: "6310",
			AccountName:      "Försäkringspremier",
			Confidence:       0.91,
			Debit:            amount,
			Credit:           0,
			Reason:           "Försäkringsbetalning = försäkringspremie",
		})

	case containsAny(counter, []string{"skatteverket", "skatt"}):
		suggestions = append(suggestions, AISuggestion{
			ID:               "ai-008",
			Description:      description,
			SuggestedAccount: "2012",
			AccountName:      "Skatter",
			Confidence:       0.94,
			Debit:            amount,
			Credit:           0,
			Reason:           "Skatteverket = skattebetalning",
		})

	default:
		// Generiskt förslag baserat på belopp
		if amount > 0 {
			suggestions = append(suggestions, AISuggestion{
				ID:               "ai-099",
				Description:      description,
				SuggestedAccount: "1930",
				AccountName:      "Företagskonto",
				Confidence:       0.45,
				Debit:            0,
				Credit:           amount,
				Reason:           "Kunde inte identifiera — granska manuellt",
			})
		} else {
			suggestions = append(suggestions, AISuggestion{
				ID:               "ai-099",
				Description:      description,
				SuggestedAccount: "6991",
				AccountName:      "Övriga externa kostnader",
				Confidence:       0.45,
				Debit:            -amount,
				Credit:           0,
				Reason:           "Kunde inte identifiera — granska manuellt",
			})
		}
	}

	return suggestions
}

func containsAny(s string, substrs []string) bool {
	for _, substr := range substrs {
		if strings.Contains(s, substr) {
			return true
		}
	}
	return false
}