package config

import (
	"errors"
	"fmt"
	"os"
	"strconv"
	"strings"
)

type Config struct {
	Env                   string
	ServerPort            string
	DatabaseURL           string
	DragonflyURL          string
	StorageRoot           string
	AuthInternalBaseURL   string
	PublicURL             string
	UserRateLimitPerMin   int
	APIKeyRateLimitPerMin int

	JWTIssuer     string
	JWTAudience   string
	JWTSecret     string
	JWTTTLSeconds int

	MailFrom     string
	ResendAPIKey string
	SMTPHost     string
	SMTPPort     int
	SMTPUser     string
	SMTPPassword string
	SMTPSecure   bool
}

func Load() (Config, error) {
	cfg := Config{
		Env:                   getenv("NODE_ENV", "development"),
		ServerPort:            getenv("BACKEND_PORT", "8080"),
		DatabaseURL:           os.Getenv("DATABASE_URL"),
		DragonflyURL:          getenv("DRAGONFLY_URL", "redis://localhost:6379/0"),
		StorageRoot:           getenv("BACKEND_STORAGE_ROOT", "./tmp/storage"),
		AuthInternalBaseURL:   getenv("AUTH_INTERNAL_BASE_URL", "http://auth:3001"),
		PublicURL:             getenv("VITE_APP_URL", "http://localhost"),
		UserRateLimitPerMin:   240,
		APIKeyRateLimitPerMin: 600,
		JWTIssuer:             getenv("JWT_ISSUER", "primora-auth"),
		JWTAudience:           getenv("JWT_AUDIENCE", "primora-api"),
		JWTSecret:             os.Getenv("JWT_SECRET"),
		MailFrom:              getenv("MAIL_FROM", "Primora <no-reply@primora.local>"),
		ResendAPIKey:          os.Getenv("RESEND_API_KEY"),
		SMTPHost:              getenv("SMTP_HOST", "localhost"),
		SMTPUser:              os.Getenv("SMTP_USER"),
		SMTPPassword:          os.Getenv("SMTP_PASSWORD"),
	}

	smtpPort, err := strconv.Atoi(getenv("SMTP_PORT", "1025"))
	if err != nil {
		return Config{}, fmt.Errorf("parse SMTP_PORT: %w", err)
	}
	cfg.SMTPPort = smtpPort

	jwtTTLSeconds, err := strconv.Atoi(getenv("JWT_TTL_SECONDS", "900"))
	if err != nil {
		return Config{}, fmt.Errorf("parse JWT_TTL_SECONDS: %w", err)
	}
	cfg.JWTTTLSeconds = jwtTTLSeconds

	userRateLimitPerMin, err := parseNonNegativeIntEnv("USER_RATE_LIMIT_PER_MINUTE", cfg.UserRateLimitPerMin)
	if err != nil {
		return Config{}, err
	}
	cfg.UserRateLimitPerMin = userRateLimitPerMin

	apiKeyRateLimitPerMin, err := parseNonNegativeIntEnv("API_KEY_RATE_LIMIT_PER_MINUTE", cfg.APIKeyRateLimitPerMin)
	if err != nil {
		return Config{}, err
	}
	cfg.APIKeyRateLimitPerMin = apiKeyRateLimitPerMin

	smtpSecure, err := strconv.ParseBool(getenv("SMTP_SECURE", "false"))
	if err != nil {
		return Config{}, fmt.Errorf("parse SMTP_SECURE: %w", err)
	}
	cfg.SMTPSecure = smtpSecure

	var missing []string
	if cfg.DatabaseURL == "" {
		missing = append(missing, "DATABASE_URL")
	}
	if cfg.JWTSecret == "" {
		missing = append(missing, "JWT_SECRET")
	}
	if cfg.StorageRoot == "" {
		missing = append(missing, "BACKEND_STORAGE_ROOT")
	}
	if cfg.AuthInternalBaseURL == "" {
		missing = append(missing, "AUTH_INTERNAL_BASE_URL")
	}
	if cfg.ResendAPIKey == "" && cfg.SMTPHost == "" {
		missing = append(missing, "RESEND_API_KEY or SMTP_HOST")
	}
	if len(missing) > 0 {
		return Config{}, errors.New("missing required environment values: " + strings.Join(missing, ", "))
	}

	return cfg, nil
}

func getenv(key, fallback string) string {
	value := os.Getenv(key)
	if value == "" {
		return fallback
	}
	return value
}

func parseNonNegativeIntEnv(key string, fallback int) (int, error) {
	raw := os.Getenv(key)
	if raw == "" {
		return fallback, nil
	}
	value, err := strconv.Atoi(raw)
	if err != nil {
		return 0, fmt.Errorf("parse %s: %w", key, err)
	}
	if value < 0 {
		return 0, fmt.Errorf("%s must be >= 0", key)
	}
	return value, nil
}