// Package config loads service configuration from environment variables.
package config

import (
	"errors"
	"fmt"
	"os"
	"time"
)

// Config holds all runtime configuration for the service.
type Config struct {
	APIKey        string
	StacksRoot    string
	Port          string
	LogLevel      string
	UpdateTimeout time.Duration
	OptInLabel    string
}

// Load reads configuration from environment variables, applies defaults,
// and validates required fields. Returns an error if validation fails so
// the service can fail-fast at startup.
func Load() (*Config, error) {
	cfg := &Config{
		APIKey:     os.Getenv("UPDATER_API_KEY"),
		StacksRoot: getenvDefault("STACKS_ROOT", "/home/shcizo/self-hosted"),
		Port:       getenvDefault("PORT", "8080"),
		LogLevel:   getenvDefault("LOG_LEVEL", "info"),
		OptInLabel: getenvDefault("OPT_IN_LABEL", "se.shcizo.auto-update"),
	}

	if cfg.APIKey == "" {
		return nil, errors.New("UPDATER_API_KEY is required")
	}

	timeoutStr := getenvDefault("UPDATE_TIMEOUT", "5m")
	d, err := time.ParseDuration(timeoutStr)
	if err != nil {
		return nil, fmt.Errorf("UPDATE_TIMEOUT %q is not a valid duration: %w", timeoutStr, err)
	}
	cfg.UpdateTimeout = d

	return cfg, nil
}

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