package auth

import (
	"context"
	"strings"

	"github.com/perfect-panel/server/internal/config"
	usermodel "github.com/perfect-panel/server/internal/model/user"
	"gorm.io/gorm"
)

// IsEmailDomainWhitelisted checks if the email's domain is in the comma-separated whitelist.
// Returns false if the email format is invalid.
func IsEmailDomainWhitelisted(email, whitelistCSV string) bool {
	if whitelistCSV == "" {
		return false
	}
	parts := strings.SplitN(email, "@", 2)
	if len(parts) != 2 {
		return false
	}
	domain := strings.ToLower(strings.TrimSpace(parts[1]))
	for _, d := range strings.Split(whitelistCSV, ",") {
		if strings.ToLower(strings.TrimSpace(d)) == domain {
			return true
		}
	}
	return false
}

func ShouldGrantTrialForEmail(register config.RegisterConfig, email string) bool {
	if !register.EnableTrial {
		return false
	}
	if !register.EnableTrialEmailWhitelist {
		return true
	}
	if register.TrialEmailDomainWhitelist == "" {
		return false
	}
	return IsEmailDomainWhitelisted(email, register.TrialEmailDomainWhitelist)
}

// NormalizeEmail returns a canonical form of the email for trial deduplication.
// Strips "+" aliases universally (user+tag@any.com → user@any.com).
// Removes dots from local part for Gmail-like providers (gmail.com, googlemail.com).
func NormalizeEmail(email string) string {
	email = strings.ToLower(strings.TrimSpace(email))
	parts := strings.SplitN(email, "@", 2)
	if len(parts) != 2 {
		return email
	}
	local, domain := parts[0], parts[1]

	// Strip + alias
	if idx := strings.IndexByte(local, '+'); idx != -1 {
		local = local[:idx]
	}

	// Remove dots for Gmail-like providers that ignore dots in local part
	if isGmailLikeDomain(domain) {
		local = strings.ReplaceAll(local, ".", "")
	}

	return local + "@" + domain
}

func isGmailLikeDomain(domain string) bool {
	switch domain {
	case "gmail.com", "googlemail.com":
		return true
	}
	return false
}

// NormalizedEmailHasTrial returns true if any user with the same normalized email
// already holds a trial subscription. Only performs the cross-user DB check when
// normalization actually changes the email (i.e., dots removed or + alias stripped).
func NormalizedEmailHasTrial(ctx context.Context, db *gorm.DB, email string, trialSubscribeId int64) bool {
	normalized := NormalizeEmail(email)
	if normalized == strings.ToLower(strings.TrimSpace(email)) {
		return false // normalization changed nothing, skip cross-user check
	}

	parts := strings.SplitN(normalized, "@", 2)
	if len(parts) != 2 {
		return false
	}
	domain := parts[1]

	var authMethods []usermodel.AuthMethods
	if err := db.WithContext(ctx).
		Model(&usermodel.AuthMethods{}).
		Select("user_id, auth_identifier").
		Where("auth_type = ? AND auth_identifier LIKE ?", "email", "%@"+domain).
		Find(&authMethods).Error; err != nil {
		return false
	}

	for _, am := range authMethods {
		if NormalizeEmail(am.AuthIdentifier) != normalized {
			continue
		}
		var count int64
		if err := db.WithContext(ctx).
			Model(&usermodel.Subscribe{}).
			Where("user_id = ? AND subscribe_id = ?", am.UserId, trialSubscribeId).
			Count(&count).Error; err != nil {
			continue
		}
		if count > 0 {
			return true
		}
	}
	return false
}