package httputil

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"

	"github.com/go-playground/validator/v10"
)

func WriteJSON(w http.ResponseWriter, status int, data any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(data)
}

func DecodeJSON[T any](w http.ResponseWriter, r *http.Request) (T, error) {
	var v T
	r.Body = http.MaxBytesReader(w, r.Body, 1<<20)

	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()

	if err := dec.Decode(&v); err != nil {
		return v, err
	}
	return v, nil
}

func WriteValidationErrors(w http.ResponseWriter, err error) {
	var ve validator.ValidationErrors
	if !errors.As(err, &ve) {
		WriteJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid request"})
		return
	}

	problems := make(map[string]string, len(ve))
	for _, fe := range ve {
		problems[fe.Field()] = messageForTag(fe)
	}
	WriteJSON(w, http.StatusBadRequest, map[string]any{"errors": problems})
}

func messageForTag(fe validator.FieldError) string {
	switch fe.Tag() {
	case "required":
		return "is required"
	case "email":
		return "must be a valid email address"
	case "min":
		return fmt.Sprintf("must be at least %s characters", fe.Param())
	case "max":
		return fmt.Sprintf("must be at most %s characters", fe.Param())
	case "gte":
		return fmt.Sprintf("must be %s or greater", fe.Param())
	case "lte":
		return fmt.Sprintf("must be %s or less", fe.Param())
	default:
		return "is invalid"
	}
}