package config

import (
	"errors"
	"os"
)

// Config holds runtime configuration for the alert-bridge process.
type Config struct {
	HTTPPort          string // HTTP_PORT, default "8080"
	APIKey            string // API_KEY — required bearer token callers must present in Authorization: Bearer <key>
	DiscordWebhookURL string // DISCORD_WEBHOOK_URL — required, the target channel's Discord Incoming Webhook URL
	MentionUserID     string // MENTION_USER_ID — optional Discord user ID; when set, level=error alerts mention this user
	OTELEndpoint      string
	LogLevel          string
	LogFormat         string
}

// Load reads alert-bridge configuration from environment variables.
func Load() (*Config, error) {
	apiKey := os.Getenv("API_KEY")
	if apiKey == "" {
		return nil, errors.New("API_KEY is required but not set")
	}

	webhookURL := os.Getenv("DISCORD_WEBHOOK_URL")
	if webhookURL == "" {
		return nil, errors.New("DISCORD_WEBHOOK_URL is required but not set")
	}

	return &Config{
		HTTPPort:          getenvDefault("HTTP_PORT", "8080"),
		APIKey:            apiKey,
		DiscordWebhookURL: webhookURL,
		MentionUserID:     os.Getenv("MENTION_USER_ID"),
		OTELEndpoint:      os.Getenv("OTEL_ENDPOINT"),
		LogLevel:          getenvDefault("LOG_LEVEL", "info"),
		LogFormat:         getenvDefault("LOG_FORMAT", "json"),
	}, nil
}

// getenvDefault keeps config loading concise for optional variables with defaults.
func getenvDefault(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}