package mux

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"reflect"
	"strconv"
	"strings"
)

func Bind[T any](r *http.Request, obj *T) error {
	contentType := r.Header.Get("Content-Type")
	switch {
	case strings.HasPrefix(contentType, "multipart/form-data"),
		strings.HasPrefix(contentType, "application/x-www-form-urlencoded"):
		if err := r.ParseForm(); err != nil {
			return err
		}
		return bindForm(r.Form, obj)
	case strings.HasPrefix(contentType, "application/json"):
		defer r.Body.Close()
		return json.NewDecoder(r.Body).Decode(obj)
	case r.Method == http.MethodGet:
		return bindForm(r.URL.Query(), obj)
	case r.Method == http.MethodPost:
		return fmt.Errorf("invalid content-type: %s", contentType)
	}

	return nil
}

func bindForm(values url.Values, obj any) error {
	val := reflect.ValueOf(obj)
	if val.Kind() == reflect.Ptr {
		val = val.Elem()
	}

	fields := val.NumField()

	for i := 0; i < fields; i++ {
		f := val.Field(i)
		if !f.IsValid() {
			continue
		}
		if !f.CanSet() {
			continue
		}
		t := val.Type().Field(i)
		k := t.Tag.Get("form")
		if k == "" {
			continue
		}
		if !values.Has(k) {
			continue
		}
		v := values.Get(k)

		switch f.Type().Kind() {
		case reflect.Bool:
			switch v {
			case "on", "true", "1":
				f.SetBool(true)
			default:
				f.SetBool(false)
			}
		case reflect.Int, reflect.Int64:
			if i, e := strconv.ParseInt(v, 0, 0); e == nil {
				f.SetInt(i)
			} else {
				return fmt.Errorf("could not set int value of %s: %s", k, e)
			}
		case reflect.Float64:
			if fl, e := strconv.ParseFloat(v, 64); e == nil {
				f.SetFloat(fl)
			} else {
				return fmt.Errorf("could not set float64 value of %s: %s", k, e)
			}
		case reflect.String:
			f.SetString(v)
		default:
			return fmt.Errorf("unsupported format %v for field %s", f.Type().Kind(), k)
		}
	}

	return nil
}