jsonapi/request.go

package jsonapi

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"reflect"
	"strconv"
	"strings"
	"time"
)

// Convert an io into a struct instance using jsonapi tags on struct fields.
// Method supports single request payloads only, at the moment. Bulk creates and updates
// are not supported yet.
//
// Will Unmarshal embedded and sideloaded payloads.  The latter is only possible if the
// object graph is complete.  That is, in the "relationships" data there are type and id,
// keys that correspond to records in the "included" array.
//
// For example you could pass it, in, req.Body and, model, a BlogPost
// struct instance to populate in an http handler,
//
//		func CreateBlog(w http.ResponseWriter, r *http.Request) {
//			blog := new(Blog)
//
//			if err := jsonapi.UnmarshalPayload(r.Body, blog); err != nil {
//				http.Error(w, err.Error(), 500)
//				return
//			}
//
//			// ...do stuff with your blog...
//
//			w.WriteHeader(201)
//			w.Header().Set("Content-Type", "application/vnd.api+json")
//
//			if err := jsonapi.MarshalOnePayload(w, blog); err != nil {
//				http.Error(w, err.Error(), 500)
//			}
//		}
//
//
// Visit https://github.com/shwoodard/jsonapi#create for more info.
//
// model interface{} should be a pointer to a struct.
func UnmarshalPayload(in io.Reader, model interface{}) error {
	payload := new(OnePayload)

	if err := json.NewDecoder(in).Decode(payload); err != nil {
		return err
	}

	if payload.Included != nil {
		includedMap := make(map[string]*Node)
		for _, included := range payload.Included {
			key := fmt.Sprintf("%s,%s", included.Type, included.Id)
			includedMap[key] = included
		}

		return unmarshalNode(payload.Data, reflect.ValueOf(model), &includedMap)
	} else {
		return unmarshalNode(payload.Data, reflect.ValueOf(model), nil)
	}

}

func unmarshalNode(data *Node, model reflect.Value, included *map[string]*Node) error {
	modelValue := model.Elem()
	modelType := model.Type().Elem()

	var er error

	var i = 0
	modelType.FieldByNameFunc(func(name string) bool {
		if er != nil {
			return false
		}

		fieldValue := modelValue.Field(i)
		fieldType := modelType.Field(i)

		i += 1

		tag := fieldType.Tag.Get("jsonapi")

		args := strings.Split(tag, ",")

		if len(args) != 2 {
			er = errors.New(fmt.Sprintf("jsonapi tag, on %s, had two few arguments", fieldType.Name))
			return false
		}

		if len(args) >= 1 && args[0] != "" {
			annotation := args[0]

			if annotation == "primary" {
				if data.Id == "" {
					return false
				}

				if data.Type != args[1] {
					er = errors.New("Trying to Unmarshal a type that does not match")
					return false
				}

				if fieldValue.Kind() == reflect.String {
					fieldValue.Set(reflect.ValueOf(data.Id))
				} else if fieldValue.Kind() == reflect.Int {
					id, err := strconv.Atoi(data.Id)
					if err != nil {
						er = err
						return false
					}
					fieldValue.SetInt(int64(id))
				} else {
					er = errors.New("Unsuppored data type for primary key, not int or string")
					return false
				}
			} else if annotation == "attr" {
				attributes := data.Attributes
				if attributes == nil {
					return false
				}

				val := attributes[args[1]]

				// next if the attribute was not included in the request
				if val == nil {
					return false
				}

				v := reflect.ValueOf(val)

				if fieldValue.Type() == reflect.TypeOf(time.Time{}) {

					var at int64

					if v.Kind() == reflect.Float64 {
						at = int64(v.Interface().(float64))
					} else if v.Kind() == reflect.Int {
						at = v.Int()
					} else {
						er = errors.New("Only numbers can be parsed as dates, unix timestamps")
						return false
					}

					t := time.Unix(at, 0)

					fieldValue.Set(reflect.ValueOf(t))

					return false
				}

				if fieldValue.Kind() == reflect.Int && v.Kind() == reflect.Float64 {
					fieldValue.Set(reflect.ValueOf(int(v.Interface().(float64))))
				} else {
					fieldValue.Set(reflect.ValueOf(val))
				}
			} else if annotation == "relation" {
				isSlice := fieldValue.Type().Kind() == reflect.Slice

				if data.Relationships == nil || data.Relationships[args[1]] == nil {
					return false
				}

				relationship := reflect.ValueOf(data.Relationships[args[1]]).Interface().(map[string]interface{})

				if isSlice {
					data := relationship["data"].([]interface{})
					models := reflect.New(fieldValue.Type()).Elem()

					for _, r := range data {
						m := reflect.New(fieldValue.Type().Elem().Elem())

						if err := unmarshalMap(r, m, included); err != nil {
							er = err
							return false
						}

						models = reflect.Append(models, m)
					}

					fieldValue.Set(models)
				} else {
					m := reflect.New(fieldValue.Type().Elem())
					if err := unmarshalMap(relationship["data"], m, included); err != nil {
						er = err
						return false
					}

					fieldValue.Set(m)
				}

			} else {
				er = errors.New(fmt.Sprintf("Unsupported jsonapi tag annotation, %s", annotation))
			}
		}

		return false
	})

	if er != nil {
		return er
	}

	return nil
}

func unmarshalMap(nodeData interface{}, model reflect.Value, included *map[string]*Node) error {
	h := nodeData.(map[string]interface{})
	node := fetchNode(h, included)

	if err := unmarshalNode(node, model, included); err != nil {
		return err
	}

	return nil
}

func fetchNode(m map[string]interface{}, included *map[string]*Node) *Node {
	var attributes map[string]interface{}
	var relationships map[string]interface{}

	if included != nil {
		key := fmt.Sprintf("%s,%s", m["type"].(string), m["id"].(string))
		node := (*included)[key]

		if node != nil {
			attributes = node.Attributes
			relationships = node.Relationships
		}
	}

	return mapToNode(m, attributes, relationships)
}

func mapToNode(m map[string]interface{}, attributes map[string]interface{}, relationships map[string]interface{}) *Node {
	node := &Node{Type: m["type"].(string)}

	if m["id"] != nil {
		node.Id = m["id"].(string)
	}

	if m["attributes"] == nil {
		node.Attributes = attributes
	} else {
		node.Attributes = m["attributes"].(map[string]interface{})
	}

	if m["relationships"] == nil {
		node.Relationships = relationships
	} else {
		node.Relationships = m["relationships"].(map[string]interface{})
	}

	return node
}