package services

import (
	"context"
	"math"

	"github.com/fish/language/backend/internal/models"
	"github.com/fish/language/backend/internal/repository/queries"
)

const defaultPageSize = 20
const maxPageSize = 100

// WordService handles business logic for words.
type WordService struct {
	q *queries.Queries
}

// NewWordService creates a new WordService.
func NewWordService(q *queries.Queries) *WordService {
	return &WordService{q: q}
}

// List returns a paginated list of words with optional filters.
func (s *WordService) List(ctx context.Context, req models.ListWordsRequest) (models.ListWordsResponse, error) {
	page := req.Page
	if page < 1 {
		page = 1
	}
	pageSize := req.PageSize
	if pageSize < 1 {
		pageSize = defaultPageSize
	}
	if pageSize > maxPageSize {
		pageSize = maxPageSize
	}
	offset := (page - 1) * pageSize

	listParams := queries.ListWordsParams{
		Limit:      pageSize,
		Offset:     offset,
		CategoryID: 0,
		Keyword:    "",
	}
	countParams := queries.CountWordsParams{
		CategoryID: 0,
		Keyword:    "",
	}
	if req.CategoryID != nil && *req.CategoryID > 0 {
		listParams.CategoryID = *req.CategoryID
		countParams.CategoryID = *req.CategoryID
	}
	if req.Keyword != "" {
		listParams.Keyword = req.Keyword
		countParams.Keyword = req.Keyword
	}

	rows, err := s.q.ListWords(ctx, listParams)
	if err != nil {
		return models.ListWordsResponse{}, err
	}
	total, err := s.q.CountWords(ctx, countParams)
	if err != nil {
		return models.ListWordsResponse{}, err
	}

	words := make([]models.Word, len(rows))
	for i, r := range rows {
		words[i] = toWord(r)
	}

	totalPages := int32(math.Ceil(float64(total) / float64(pageSize)))
	return models.ListWordsResponse{
		Words:      words,
		Total:      total,
		Page:       page,
		PageSize:   pageSize,
		TotalPages: totalPages,
	}, nil
}

// Get returns a single word by id.
func (s *WordService) Get(ctx context.Context, id int32) (models.Word, error) {
	row, err := s.q.GetWord(ctx, id)
	if err != nil {
		return models.Word{}, err
	}
	return toWord(row), nil
}

// Create creates a new word.
func (s *WordService) Create(ctx context.Context, req models.CreateWordRequest) (models.Word, error) {
	row, err := s.q.CreateWord(ctx, queries.CreateWordParams{
		CategoryID:      req.CategoryID,
		Word:            req.Word,
		Translation:     req.Translation,
		Phonetic:        req.Phonetic,
		ExampleSentence: req.ExampleSentence,
		AudioUrl:        req.AudioURL,
		ImageUrl:        req.ImageURL,
		SortOrder:       req.SortOrder,
	})
	if err != nil {
		return models.Word{}, err
	}
	return toWord(row), nil
}

// Update updates an existing word.
func (s *WordService) Update(ctx context.Context, id int32, req models.UpdateWordRequest) (models.Word, error) {
	row, err := s.q.UpdateWord(ctx, queries.UpdateWordParams{
		ID:              id,
		CategoryID:      req.CategoryID,
		Word:            req.Word,
		Translation:     req.Translation,
		Phonetic:        req.Phonetic,
		ExampleSentence: req.ExampleSentence,
		AudioUrl:        req.AudioURL,
		ImageUrl:        req.ImageURL,
		SortOrder:       req.SortOrder,
	})
	if err != nil {
		return models.Word{}, err
	}
	return toWord(row), nil
}

// Delete removes a word by id.
func (s *WordService) Delete(ctx context.Context, id int32) error {
	return s.q.DeleteWord(ctx, id)
}

func toWord(w queries.Word) models.Word {
	return models.Word{
		ID:              w.ID,
		CategoryID:      w.CategoryID,
		Word:            w.Word,
		Translation:     w.Translation,
		Phonetic:        nullString(w.Phonetic),
		ExampleSentence: nullString(w.ExampleSentence),
		AudioURL:        nullString(w.AudioUrl),
		ImageURL:        nullString(w.ImageUrl),
		SortOrder:       w.SortOrder,
		CreatedAt:       w.CreatedAt,
		UpdatedAt:       w.UpdatedAt,
	}
}

func nullString(s *string) *string {
	if s == nil {
		return nil
	}
	v := *s
	return &v
}