package config

import (
	"os"
	"strconv"
	"strings"
	"time"
)

type Config struct {
	HTTPAddr        string
	DBDSN           string
	StoreBackend    string
	RunMigrations   bool
	SNMPEnabled     bool
	SNMPCommunity   string
	ResetDBSecret   string // NETTOPO_RESET_DB_SECRET — секрет для POST /api/admin/purge-scans
	// Пул соединений к PostgreSQL (см. database/sql). По умолчанию ограничен, иначе при большом скане легко исчерпать max_connections на сервере.
	DBMaxOpenConns    int
	DBMaxIdleConns    int
	DBConnMaxLifetime time.Duration
}

func FromEnv() Config {
	addr := os.Getenv("HTTP_ADDR")
	if addr == "" {
		addr = ":8080"
	}

	dbDSN := os.Getenv("DB_DSN")
	storeBackend := os.Getenv("STORE_BACKEND")
	if storeBackend == "" {
		if dbDSN != "" {
			storeBackend = "postgres"
		} else {
			storeBackend = "memory"
		}
	}

	runMigrations := true
	if os.Getenv("RUN_MIGRATIONS") == "false" {
		runMigrations = false
	}
	snmpEnabled := true
	if os.Getenv("SNMP_ENABLED") == "false" {
		snmpEnabled = false
	}
	snmpCommunity := os.Getenv("SNMP_COMMUNITY")
	if snmpCommunity == "" {
		snmpCommunity = "public"
	}

	maxOpen := intFromEnvMin("DB_MAX_OPEN_CONNS", 25, 1)
	maxIdle := intFromEnvMin("DB_MAX_IDLE_CONNS", 10, 0)
	if maxIdle > maxOpen {
		maxIdle = maxOpen
	}
	connLife := 30 * time.Minute
	if s := strings.TrimSpace(os.Getenv("DB_CONN_MAX_LIFETIME_SEC")); s != "" {
		if sec, err := strconv.Atoi(s); err == nil {
			if sec == 0 {
				connLife = 0 // без ограничения времени жизни соединения
			} else if sec > 0 {
				connLife = time.Duration(sec) * time.Second
			}
		}
	}

	return Config{
		HTTPAddr:          addr,
		DBDSN:             dbDSN,
		StoreBackend:      storeBackend,
		RunMigrations:     runMigrations,
		SNMPEnabled:       snmpEnabled,
		SNMPCommunity:     snmpCommunity,
		ResetDBSecret:     strings.TrimSpace(os.Getenv("NETTOPO_RESET_DB_SECRET")),
		DBMaxOpenConns:    maxOpen,
		DBMaxIdleConns:    maxIdle,
		DBConnMaxLifetime: connLife,
	}
}

func intFromEnvMin(key string, def, min int) int {
	s := strings.TrimSpace(os.Getenv(key))
	if s == "" {
		return def
	}
	n, err := strconv.Atoi(s)
	if err != nil || n < min {
		return def
	}
	return n
}