package email

import (
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"strings"
)

func newUnsubscribeToken() (string, error) {
	b := make([]byte, 32)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return base64.RawURLEncoding.EncodeToString(b), nil
}

func UnsubscribeURL(publicAPIURL, token string) string {
	base := strings.TrimRight(strings.TrimSpace(publicAPIURL), "/")
	if base == "" {
		base = "http://localhost:8080"
	}
	return fmt.Sprintf("%s/api/public/unsubscribe?token=%s", base, token)
}

func UnsubscribePageURL(webOrigin, token string) string {
	base := strings.TrimRight(strings.TrimSpace(webOrigin), "/")
	if base == "" {
		base = "http://localhost:5174"
	}
	return fmt.Sprintf("%s/unsubscribe?token=%s", base, token)
}

func listUnsubscribeHeaders(oneClickURL, mailtoFallback string) map[string]string {
	h := map[string]string{
		"List-Unsubscribe-Post": "List-Unsubscribe=One-Click",
	}
	parts := make([]string, 0, 2)
	if oneClickURL != "" {
		parts = append(parts, "<"+oneClickURL+">")
	}
	if mailtoFallback != "" {
		parts = append(parts, "<mailto:"+mailtoFallback+">")
	}
	if len(parts) > 0 {
		h["List-Unsubscribe"] = strings.Join(parts, ", ")
	}
	return h
}

func injectUnsubscribeFooter(html, text, pageURL string) (string, string) {
	link := strings.TrimSpace(pageURL)
	if link == "" {
		return html, text
	}
	footerHTML := fmt.Sprintf(
		`<hr style="border:none;border-top:1px solid #e5e7eb;margin:24px 0"/><p style="font-size:12px;color:#6b7280">You received this email because you opted in to marketing from this store. <a href="%s">Unsubscribe</a>.</p>`,
		link,
	)
	footerText := fmt.Sprintf("\n\n---\nUnsubscribe: %s\n", link)
	if strings.TrimSpace(html) != "" && !strings.Contains(strings.ToLower(html), "unsubscribe") {
		html = html + footerHTML
	}
	if strings.TrimSpace(text) != "" && !strings.Contains(strings.ToLower(text), "unsubscribe") {
		text = text + footerText
	} else if strings.TrimSpace(text) == "" && strings.TrimSpace(html) != "" {
		text = "Unsubscribe: " + link
	}
	return html, text
}