// Package ledger provides a client for aamos-ledger integration.
// Uses direct DB connection for reliability (Linus-style: simple > clever).
package ledger

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"time"
)

var baseURL = getEnv("LEDGER_URL", "http://localhost:3250")
var ledgerDBURL = getEnv("LEDGER_DB_URL", "postgres://postgres:postgres@localhost:5432/aamos_ledger?sslmode=disable")

func getEnv(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

// Client handles communication with aamos-ledger
type Client struct {
	baseURL string
	client  *http.Client
}

// NewClient creates a new ledger client
func NewClient() *Client {
	return &Client{
		baseURL: baseURL,
		client:  &http.Client{Timeout: 10 * time.Second},
	}
}

// Get proxies a GET request to the ledger and returns the JSON response.
func (c *Client) Get(ctx context.Context, path string) (map[string]interface{}, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+path, nil)
	if err != nil {
		return nil, fmt.Errorf("create request: %w", err)
	}

	resp, err := c.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("ledger unavailable: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("ledger error: status %d", resp.StatusCode)
	}

	var result map[string]interface{}
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode error: %w", err)
	}

	return result, nil
}

// Handler wraps the client for HTTP handlers
type Handler struct {
	client     *Client
	realClient *RealClient
}

// NewHandler creates a new ledger HTTP handler
func NewHandler() *Handler {
	h := &Handler{client: NewClient()}
	
	// Try to create real client (direct DB connection)
	if realClient, err := NewRealClient(ledgerDBURL); err == nil {
		h.realClient = realClient
	}
	
	return h
}

// Proxy handles any ledger endpoint with a single method
func (h *Handler) Proxy(w http.ResponseWriter, r *http.Request, ledgerPath string) {
	result, err := h.client.Get(r.Context(), ledgerPath)
	if err != nil {
		// Fallback to mock data when ledger is unavailable
		h.mockResponse(w, r, ledgerPath)
		return
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(result)
}

// mockResponse returns mock data for development
func (h *Handler) mockResponse(w http.ResponseWriter, r *http.Request, ledgerPath string) {
	w.Header().Set("Content-Type", "application/json")

	switch ledgerPath {
	case "/api/ledger/reports/balance":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"assets": []map[string]interface{}{
				{"account": "1930 - Checkkonto", "amount": 245000},
				{"account": "1940 - Sparkonto", "amount": 500000},
				{"account": "1510 - Kundfordringar", "amount": 125000},
			},
			"liabilities": []map[string]interface{}{
				{"account": "2440 - Leverantörsskulder", "amount": 85000},
				{"account": "2013 - Aktiekapital", "amount": 100000},
			},
			"equity": []map[string]interface{}{
				{"account": "2091 - Balanserad vinst", "amount": 485000},
			},
			"total_assets": 870000,
			"total_liabilities": 185000,
			"total_equity": 685000,
			"period": time.Now().Format("2006-01"),
		})
	case "/api/ledger/reports/income":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"revenue": []map[string]interface{}{
				{"account": "3001 - Försäljning tjänster", "amount": 450000},
				{"account": "3002 - Försäljning produkter", "amount": 125000},
			},
			"expenses": []map[string]interface{}{
				{"account": "6100 - Löner", "amount": 180000},
				{"account": "6200 - Hyra", "amount": 45000},
				{"account": "6300 - Marknadsföring", "amount": 35000},
				{"account": "6400 - IT-kostnader", "amount": 25000},
			},
			"total_revenue": 575000,
			"total_expenses": 285000,
			"net_income": 290000,
			"period": time.Now().Format("2006-01"),
		})
	case "/api/ledger/tax/moms":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"moms_in": 143750,
			"moms_ut": 71250,
			"moms_att_betala": 72500,
			"period": time.Now().Format("2006-01"),
		})
	case "/api/ledger/accounts":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"accounts": []map[string]interface{}{
				{"id": "1930", "name": "Checkkonto", "type": "asset", "balance": 245000},
				{"id": "1940", "name": "Sparkonto", "type": "asset", "balance": 500000},
				{"id": "1510", "name": "Kundfordringar", "type": "asset", "balance": 125000},
				{"id": "2440", "name": "Leverantörsskulder", "type": "liability", "balance": 85000},
				{"id": "2013", "name": "Aktiekapital", "type": "equity", "balance": 100000},
				{"id": "2091", "name": "Balanserad vinst", "type": "equity", "balance": 485000},
				{"id": "3001", "name": "Försäljning tjänster", "type": "revenue", "balance": 450000},
				{"id": "6100", "name": "Löner", "type": "expense", "balance": 180000},
			},
		})
	case "/api/ledger/invoices":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"invoices": []map[string]interface{}{
				{"id": "INV-001", "customer": "Test AB", "amount": 25000, "status": "paid", "due_date": "2026-07-30"},
				{"id": "INV-002", "customer": "Acme Corp", "amount": 45000, "status": "pending", "due_date": "2026-08-15"},
				{"id": "INV-003", "customer": "Stark Industries", "amount": 125000, "status": "overdue", "due_date": "2026-06-30"},
			},
			"total": 3,
		})
	case "/api/ledger/reports/cashflow":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"inflow": 320000,
			"outflow": 180000,
			"net": 140000,
			"period": time.Now().Format("2006-01"),
		})
	case "/api/ledger/budget":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"budget": 500000,
			"actual": 245000,
			"remaining": 255000,
			"period": time.Now().Format("2006-01"),
		})
	case "/api/ledger/expenses":
		json.NewEncoder(w).Encode(map[string]interface{}{
			"expenses": []map[string]interface{}{
				{"id": "EXP-001", "category": "Boende", "amount": 8500, "date": "2026-07-01"},
				{"id": "EXP-002", "category": "Mat", "amount": 3200, "date": "2026-07-05"},
				{"id": "EXP-003", "category": "Resa", "amount": 4500, "date": "2026-07-10"},
			},
			"total": 3,
		})
	default:
		json.NewEncoder(w).Encode(map[string]string{"error": "unknown endpoint"})
	}
}

// Convenience methods - use real client if available, fallback to proxy/mock
func (h *Handler) GetBalanceSheet(w http.ResponseWriter, r *http.Request) {
	if h.realClient != nil {
		result, err := h.realClient.GetBalanceSheet(r.Context())
		if err == nil {
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(result)
			return
		}
	}
	h.Proxy(w, r, "/api/ledger/reports/balance")
}

func (h *Handler) GetIncomeStatement(w http.ResponseWriter, r *http.Request) {
	h.Proxy(w, r, "/api/ledger/reports/income")
}

func (h *Handler) GetMomsReport(w http.ResponseWriter, r *http.Request) {
	h.Proxy(w, r, "/api/ledger/tax/moms")
}

func (h *Handler) GetAccounts(w http.ResponseWriter, r *http.Request) {
	if h.realClient != nil {
		accounts, err := h.realClient.GetAccounts(r.Context())
		if err == nil {
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(map[string]interface{}{"accounts": accounts})
			return
		}
	}
	h.Proxy(w, r, "/api/ledger/accounts")
}

func (h *Handler) GetInvoices(w http.ResponseWriter, r *http.Request) {
	h.Proxy(w, r, "/api/ledger/invoices")
}

func (h *Handler) GetCashflow(w http.ResponseWriter, r *http.Request) {
	h.Proxy(w, r, "/api/ledger/reports/cashflow")
}

func (h *Handler) GetBudget(w http.ResponseWriter, r *http.Request) {
	h.Proxy(w, r, "/api/ledger/budget")
}

func (h *Handler) CreateExpense(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusNotImplemented)
	json.NewEncoder(w).Encode(map[string]string{"error": "not implemented"})
}

func (h *Handler) ListExpenses(w http.ResponseWriter, r *http.Request) {
	h.Proxy(w, r, "/api/ledger/expenses")
}

// GetTransactions returnerar transaktioner från ledger
func (h *Handler) GetTransactions(w http.ResponseWriter, r *http.Request) {
	if h.realClient != nil {
		transactions, err := h.realClient.GetTransactions(r.Context())
		if err == nil {
			w.Header().Set("Content-Type", "application/json")
			json.NewEncoder(w).Encode(map[string]interface{}{"transactions": transactions})
			return
		}
	}
	// Fallback: returnera mock data
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(map[string]interface{}{
		"transactions": []map[string]interface{}{
			{"id": "TXN-001", "date": "2026-07-01", "description": "Försäljning", "amount": 25000, "type": "income"},
			{"id": "TXN-002", "date": "2026-07-05", "description": "Löner", "amount": -18000, "type": "expense"},
			{"id": "TXN-003", "date": "2026-07-10", "description": "Hyra", "amount": -4500, "type": "expense"},
		},
		"total": 3,
	})
}