package campaigns

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"net/mail"
	"regexp"
	"strings"
	"unicode"

	"github.com/descrybe/descrybe-v2/apps/api/internal/security"
)

const (
	MaxPromptLen    = security.MaxCampaignPromptRunes
	MaxSubjectLen   = 200
	MaxHTMLBodyLen  = security.MaxEmailHTMLRunes
	unsubscribeMark = "data-descrybe-unsubscribe"
)

var emailLoose = regexp.MustCompile(`(?i)^[a-z0-9._%+\-]+@[a-z0-9.\-]+\.[a-z]{2,}$`)

// NormalizeEmail lowercases and trims; returns ErrInvalidEmail when invalid.
func NormalizeEmail(raw string) (string, error) {
	raw = strings.TrimSpace(strings.ToLower(raw))
	if raw == "" || len(raw) > 254 {
		return "", ErrInvalidEmail
	}
	addr, err := mail.ParseAddress(raw)
	if err != nil {
		return "", ErrInvalidEmail
	}
	e := strings.TrimSpace(strings.ToLower(addr.Address))
	if !emailLoose.MatchString(e) {
		return "", ErrInvalidEmail
	}
	return e, nil
}

func EmailHash(email string) string {
	sum := sha256.Sum256([]byte(strings.ToLower(strings.TrimSpace(email))))
	return hex.EncodeToString(sum[:])
}

func NewToken() (string, error) {
	b := make([]byte, 24)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return hex.EncodeToString(b), nil
}

func ValidatePrompt(prompt string) error {
	if security.CapPromptLength(prompt, MaxPromptLen) {
		return ErrPromptTooLong
	}
	return nil
}

// SanitizePrompt bounds and soft-filters campaign prompts before AI / storage.
func SanitizePrompt(prompt string) string {
	return security.SanitizePrompt(prompt, MaxPromptLen)
}

// SanitizeHTMLBody strips dangerous markup from generated/stored campaign HTML.
func SanitizeHTMLBody(html string) string {
	return security.SanitizeEmailHTML(html)
}

func HasUnsubscribeFooter(html string) bool {
	lower := strings.ToLower(html)
	if strings.Contains(lower, unsubscribeMark) {
		return true
	}
	if strings.Contains(lower, "unsubscribe") && (strings.Contains(lower, "href=") || strings.Contains(lower, "/unsubscribe")) {
		return true
	}
	return false
}

func EnsureUnsubscribeFooter(html, plain, unsubscribeURL string) (string, string) {
	if HasUnsubscribeFooter(html) {
		if plain == "" {
			plain = stripTags(html)
		}
		return html, plain
	}
	footerHTML := `<hr style="border:none;border-top:1px solid #ddd;margin:24px 0"/>` +
		`<p style="font-size:12px;color:#666" ` + unsubscribeMark + `="1">` +
		`You are receiving this because you opted in to marketing emails. ` +
		`<a href="` + unsubscribeURL + `">Unsubscribe</a>.</p>`
	footerPlain := "\n\n---\nUnsubscribe: " + unsubscribeURL + "\n"
	if strings.TrimSpace(html) == "" {
		html = "<div></div>"
	}
	html = html + footerHTML
	if plain == "" {
		plain = stripTags(html)
	} else {
		plain = plain + footerPlain
	}
	return html, plain
}

func stripTags(s string) string {
	var b strings.Builder
	inTag := false
	for _, r := range s {
		switch {
		case r == '<':
			inTag = true
		case r == '>':
			inTag = false
		case !inTag:
			if unicode.IsSpace(r) {
				if b.Len() > 0 && b.String()[b.Len()-1] != ' ' {
					b.WriteByte(' ')
				}
			} else {
				b.WriteRune(r)
			}
		}
	}
	return strings.TrimSpace(b.String())
}