package graphql

import (
	"context"
	"net/http"
	"strconv"
	"tercul/internal/app"
	"tercul/internal/app/author"
	"tercul/internal/domain"

	"github.com/graph-gophers/dataloader/v7"
)

type ctxKey string

const (
	loadersKey = ctxKey("dataloaders")
)

type Dataloaders struct {
	AuthorLoader *dataloader.Loader[string, *domain.Author]
}

func newAuthorLoader(authorQueries *author.AuthorQueries) *dataloader.Loader[string, *domain.Author] {
	return dataloader.NewBatchedLoader(func(ctx context.Context, keys []string) []*dataloader.Result[*domain.Author] {
		ids := make([]uint, len(keys))
		for i, key := range keys {
			id, err := strconv.ParseUint(key, 10, 32)
			if err != nil {
				// handle error
			}
			ids[i] = uint(id)
		}

		authors, err := authorQueries.GetAuthorsByIDs(ctx, ids)
		if err != nil {
			// handle error
		}

		authorMap := make(map[string]*domain.Author)
		for _, author := range authors {
			authorMap[strconv.FormatUint(uint64(author.ID), 10)] = &author
		}

		results := make([]*dataloader.Result[*domain.Author], len(keys))
		for i, key := range keys {
			results[i] = &dataloader.Result[*domain.Author]{Data: authorMap[key]}
		}

		return results
	})
}

func Middleware(app *app.Application, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		loaders := Dataloaders{
			AuthorLoader: newAuthorLoader(app.AuthorQueries),
		}
		ctx := context.WithValue(r.Context(), loadersKey, loaders)
		r = r.WithContext(ctx)
		next.ServeHTTP(w, r)
	})
}

func For(ctx context.Context) Dataloaders {
	return ctx.Value(loadersKey).(Dataloaders)
}