package service

import (
	"context"
	"errors"
	"fmt"
	"regexp"
	"strings"

	"github.com/prabhupadasays/spsays-bff/internal/model"
	"github.com/prabhupadasays/spsays-bff/internal/repository"
)

const (
	maxCategoryLabel       = 60
	maxCategoryDescription = 200
)

var (
	ErrCategoryLabel       = fmt.Errorf("a category needs a name (up to %d characters)", maxCategoryLabel)
	ErrCategoryDescription = fmt.Errorf("the description can be up to %d characters", maxCategoryDescription)
	ErrCategoryLastActive  = errors.New("the feedback form needs at least one category")
)

var categoryNonSlug = regexp.MustCompile(`[^a-z0-9]+`)

// FeedbackCategoryService manages the /feedback form's categories.
type FeedbackCategoryService struct {
	repo *repository.FeedbackCategoryRepo
}

func NewFeedbackCategoryService(repo *repository.FeedbackCategoryRepo) *FeedbackCategoryService {
	return &FeedbackCategoryService{repo: repo}
}

// Active is what the /feedback form offers, in order.
func (s *FeedbackCategoryService) Active(ctx context.Context) ([]model.FeedbackCategory, error) {
	return s.repo.List(ctx, false)
}

// All is the admin's view: archived ones too, with usage counts.
func (s *FeedbackCategoryService) All(ctx context.Context) ([]model.FeedbackCategory, error) {
	return s.repo.List(ctx, true)
}

func cleanCategory(label, description string) (string, string, error) {
	label = strings.TrimSpace(label)
	description = strings.TrimSpace(description)
	if label == "" || len([]rune(label)) > maxCategoryLabel {
		return "", "", ErrCategoryLabel
	}
	if len([]rune(description)) > maxCategoryDescription {
		return "", "", ErrCategoryDescription
	}
	return label, description, nil
}

// Create adds a category to the end of the form. Its key is derived from
// the name ("Audio problem" → audio_problem) and fixed from then on, so it
// can be renamed freely later without touching past feedback.
func (s *FeedbackCategoryService) Create(ctx context.Context, label, description string) (*model.FeedbackCategory, error) {
	label, description, err := cleanCategory(label, description)
	if err != nil {
		return nil, err
	}
	base := strings.Trim(categoryNonSlug.ReplaceAllString(strings.ToLower(label), "_"), "_")
	if base == "" {
		base = "category"
	}
	if len(base) > 40 {
		base = strings.TrimRight(base[:40], "_")
	}
	key := base
	for i := 2; ; i++ {
		taken, err := s.repo.KeyTaken(ctx, key)
		if err != nil {
			return nil, err
		}
		if !taken {
			break
		}
		key = fmt.Sprintf("%s_%d", base, i)
	}
	return s.repo.Create(ctx, key, label, description)
}

// Update renames, rewords, archives or restores a category. The last active
// category can't be archived — the form would have nothing to offer.
func (s *FeedbackCategoryService) Update(ctx context.Context, key, label, description string, archived bool) error {
	label, description, err := cleanCategory(label, description)
	if err != nil {
		return err
	}
	if archived {
		if err := s.guardLastActive(ctx, key); err != nil {
			return err
		}
	}
	return s.repo.Update(ctx, key, label, description, archived)
}

// Delete removes a category nothing is filed under (otherwise: archive it).
func (s *FeedbackCategoryService) Delete(ctx context.Context, key string) error {
	if err := s.guardLastActive(ctx, key); err != nil {
		return err
	}
	return s.repo.Delete(ctx, key)
}

// Reorder sets the form's order.
func (s *FeedbackCategoryService) Reorder(ctx context.Context, keys []string) error {
	return s.repo.Reorder(ctx, keys)
}

func (s *FeedbackCategoryService) guardLastActive(ctx context.Context, key string) error {
	active, err := s.repo.List(ctx, false)
	if err != nil {
		return err
	}
	if len(active) == 1 && active[0].Key == key {
		return ErrCategoryLastActive
	}
	return nil
}