package support

import (
	"context"
	"regexp"
	"strings"
	"unicode/utf8"

	"github.com/google/uuid"
)

const (
	maxSubjectLen     = 200
	maxBodyLen        = 10000
	maxCategoryLen    = 32
	maxCSATCommentLen = 2000
	maxTags           = 10
	maxTagLen         = 40
	maxRelatedSKULen  = 128
)

// Seed categories mirror 031_support_ticket_detail.sql (fallback when table missing).
var allowedCategories = map[string]struct{}{
	"billing":         {},
	"billing_credits": {},
	"bug":             {},
	"account":         {},
	"integrations":    {},
	"processing":      {},
	"export":          {},
	"migration":       {}, // P1-17 hypercare missing/wrong data reports
	"other":           {},
}

var allowedStatuses = map[string]struct{}{
	"open":     {},
	"pending":  {},
	"resolved": {},
	"closed":   {},
}

var allowedPriorities = map[string]struct{}{
	"low":    {},
	"normal": {},
	"high":   {},
}

var tagSlugPattern = regexp.MustCompile(`^[a-z0-9][a-z0-9_-]*$`)

func normalizeSubject(s string) (string, error) {
	s = strings.TrimSpace(strings.ReplaceAll(s, "\x00", ""))
	if s == "" {
		return "", ErrSubjectRequired
	}
	if utf8.RuneCountInString(s) > maxSubjectLen {
		s = string([]rune(s)[:maxSubjectLen])
	}
	return s, nil
}

func normalizeBody(s string) (string, error) {
	s = strings.TrimSpace(strings.ReplaceAll(s, "\x00", ""))
	if s == "" {
		return "", ErrBodyRequired
	}
	if utf8.RuneCountInString(s) > maxBodyLen {
		s = string([]rune(s)[:maxBodyLen])
	}
	return s, nil
}

func normalizeCategory(s string) (string, error) {
	s = strings.ToLower(strings.TrimSpace(s))
	if s == "" {
		return "other", nil
	}
	if utf8.RuneCountInString(s) > maxCategoryLen {
		return "", ErrInvalidCategory
	}
	if _, ok := allowedCategories[s]; !ok {
		return "", ErrInvalidCategory
	}
	return s, nil
}

// normalizeCategoryActive prefers active rows in support_categories when available.
func (s *Service) normalizeCategoryActive(ctx context.Context, category string) (string, error) {
	slug, err := normalizeCategory(category)
	if err != nil {
		// Soft expand: if seed reject but DB has active slug, accept.
		candidate := strings.ToLower(strings.TrimSpace(category))
		if candidate == "" || utf8.RuneCountInString(candidate) > maxCategoryLen {
			return "", err
		}
		if s == nil || s.Pool == nil {
			return "", err
		}
		var active bool
		qerr := s.Pool.QueryRow(ctx, `
			SELECT is_active FROM support_categories WHERE slug = $1`, candidate).Scan(&active)
		if qerr != nil || !active {
			return "", ErrInvalidCategory
		}
		return candidate, nil
	}
	if s == nil || s.Pool == nil {
		return slug, nil
	}
	var active bool
	qerr := s.Pool.QueryRow(ctx, `
		SELECT is_active FROM support_categories WHERE slug = $1`, slug).Scan(&active)
	if qerr != nil {
		if IsMissingRelation(qerr) {
			return slug, nil
		}
		// Table present but slug missing: allow seed defaults (migration may lag seeds).
		return slug, nil
	}
	if !active {
		return "", ErrInvalidCategory
	}
	return slug, nil
}

func normalizeStatus(s string) (string, error) {
	s = strings.ToLower(strings.TrimSpace(s))
	if _, ok := allowedStatuses[s]; !ok {
		return "", ErrInvalidStatus
	}
	return s, nil
}

func normalizePriority(s string) (string, error) {
	s = strings.ToLower(strings.TrimSpace(s))
	if s == "" {
		return "normal", nil
	}
	if _, ok := allowedPriorities[s]; !ok {
		return "", ErrInvalidPriority
	}
	return s, nil
}

func normalizeCSATScore(score int) (int, error) {
	if score < 1 || score > 5 {
		return 0, ErrInvalidScore
	}
	return score, nil
}

func normalizeCSATComment(s string) (string, error) {
	s = strings.TrimSpace(strings.ReplaceAll(s, "\x00", ""))
	if utf8.RuneCountInString(s) > maxCSATCommentLen {
		s = string([]rune(s)[:maxCSATCommentLen])
	}
	return s, nil
}

func normalizeTags(tags []string) ([]string, error) {
	if len(tags) == 0 {
		return []string{}, nil
	}
	out := make([]string, 0, len(tags))
	seen := make(map[string]struct{}, len(tags))
	for _, raw := range tags {
		t := strings.ToLower(strings.TrimSpace(strings.ReplaceAll(raw, "\x00", "")))
		if t == "" {
			continue
		}
		if utf8.RuneCountInString(t) > maxTagLen {
			return nil, ErrInvalidTag
		}
		if !tagSlugPattern.MatchString(t) {
			return nil, ErrInvalidTag
		}
		if _, ok := seen[t]; ok {
			continue
		}
		seen[t] = struct{}{}
		out = append(out, t)
		if len(out) > maxTags {
			return nil, ErrTooManyTags
		}
	}
	return out, nil
}

func normalizeRelatedSKU(s string) (string, error) {
	s = strings.TrimSpace(strings.ReplaceAll(s, "\x00", ""))
	if s == "" {
		return "", nil
	}
	if utf8.RuneCountInString(s) > maxRelatedSKULen {
		return "", ErrInvalidRelatedSKU
	}
	return s, nil
}

func normalizeRelatedProductID(id *uuid.UUID) (*uuid.UUID, error) {
	if id == nil {
		return nil, nil
	}
	if *id == uuid.Nil {
		return nil, ErrInvalidRelatedProduct
	}
	return id, nil
}