package geoip

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/telemt/telemt-api/internal/config"
)

// FromConfig ensures MMDB files exist (optional download) and opens readers. Returns nil if geoip disabled.
func FromConfig(cfg *config.GeoIPConfig, httpClient *http.Client, log *slog.Logger) (*Service, error) {
	if cfg == nil || !cfg.Enabled {
		return nil, nil
	}
	cityPath := strings.TrimSpace(cfg.DatabasePath)
	asnPath := strings.TrimSpace(cfg.AsnDatabasePath)
	if cityPath == "" && asnPath == "" {
		return nil, errors.New("geoip.enabled requires at least one of geoip.database_path or geoip.asn_database_path")
	}

	if httpClient == nil {
		httpClient = http.DefaultClient
	}

	if cityPath != "" {
		if _, err := os.Stat(cityPath); err != nil {
			if !os.IsNotExist(err) {
				return nil, err
			}
			if cfg.DownloadURL == "" {
				return nil, fmt.Errorf("geoip city database %q missing and geoip.download_url is empty", cityPath)
			}
			if log != nil {
				log.Info("geoip downloading city database", "url", cfg.DownloadURL, "path", cityPath)
			}
			ctx, cancel := context.WithTimeout(context.Background(), 15*time.Minute)
			defer cancel()
			if err := DownloadMMDB(ctx, httpClient, cfg.DownloadURL, cityPath); err != nil {
				return nil, err
			}
		}
	}

	if asnPath != "" {
		if _, err := os.Stat(asnPath); err != nil {
			if !os.IsNotExist(err) {
				return nil, err
			}
			if cfg.AsnDownloadURL == "" {
				return nil, fmt.Errorf("geoip asn database %q missing and geoip.asn_download_url is empty", asnPath)
			}
			if log != nil {
				log.Info("geoip downloading asn database", "url", cfg.AsnDownloadURL, "path", asnPath)
			}
			ctx, cancel := context.WithTimeout(context.Background(), 15*time.Minute)
			defer cancel()
			if err := DownloadMMDB(ctx, httpClient, cfg.AsnDownloadURL, asnPath); err != nil {
				return nil, err
			}
		}
	}

	return OpenDatabases(cityPath, asnPath)
}