package dyzurbot

import (
	"context"
	"fmt"
	"os"
	"time"

	"github.com/joho/godotenv"
)

// Config holds the cache/sync settings, sourced from the environment/.env.
type Config struct {
	SpreadsheetID string
	SheetRange    string
	CachePath     string
	SyncInterval  time.Duration
}

// LoadConfig reads configuration from the environment (and .env if present),
// applying defaults for everything except the required spreadsheet ID.
func LoadConfig() (Config, error) {
	_ = godotenv.Load()

	cfg := Config{
		SpreadsheetID: os.Getenv("SPREADSHEET_ID"),
		SheetRange:    getenvDefault("SHEET_RANGE", "Dyżury!A1:F100"),
		CachePath:     getenvDefault("ROTA_CACHE_PATH", "rota.json"),
	}
	if cfg.SpreadsheetID == "" {
		return Config{}, fmt.Errorf("missing SPREADSHEET_ID in environment/.env")
	}

	raw := getenvDefault("SYNC_INTERVAL", "30m")
	interval, err := time.ParseDuration(raw)
	if err != nil {
		return Config{}, fmt.Errorf("invalid SYNC_INTERVAL %q: %w", raw, err)
	}
	if interval <= 0 {
		return Config{}, fmt.Errorf("SYNC_INTERVAL must be positive, got %v", interval)
	}
	cfg.SyncInterval = interval

	return cfg, nil
}

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

// Service ties the Store and Syncer together for the bot to consume.
type Service struct {
	Store    *Store
	Syncer   *Syncer
	interval time.Duration
}

// NewService builds the cache + syncer from config.
func NewService(cfg Config) *Service {
	store := NewStore(cfg.CachePath)
	syncer := NewSyncer(store, SheetFetcher(cfg.SpreadsheetID, cfg.SheetRange))
	return &Service{Store: store, Syncer: syncer, interval: cfg.SyncInterval}
}

// Start loads the cached rota, runs one best-effort sync in the background
// (a failure leaves the cached/empty data in place — offline-tolerant), then
// polls in the background until ctx is canceled.
func (s *Service) Start(ctx context.Context) error {
	if err := s.Store.Load(); err != nil {
		return err
	}
	go func() { _ = s.Syncer.Sync(ctx) }()
	go s.Syncer.Run(ctx, s.interval)
	return nil
}