moltin/gomo

package core

import (
    "encoding/json"
    "strings"
)

// Relationship is the shorthand relationship object
type Relationship struct {
    Type string `json:"type"`
    ID   string `json:"id"`
}

// RelationshipContainer contains one-to-one or on-to-many relationships.
// One-to-one relationships should have exactly one Relationship and
// OneToOne set to true.
type RelationshipContainer struct {
    Relationships []Relationship
    OneToOne      bool
}

// Relationships represents a relaionships object
type Relationships map[string]RelationshipContainer

// MarshalJSON marshals Relationships into JSON
func (r Relationships) MarshalJSON() ([]byte, error) {
    out := make(map[string]interface{})
    for key, rel := range r {
        if rel.OneToOne {
            if len(rel.Relationships) == 0 {
                continue
            }
            out[key] = struct {
                Data Relationship `json:"data"`
            }{
                Data: rel.Relationships[0],
            }
        } else {
            out[key] = struct {
                Data []Relationship `json:"data"`
            }{
                Data: rel.Relationships,
            }
        }
    }
    return json.Marshal(out)
}

func isJSONArray(j []byte) bool {
    s := string(j)
    return strings.HasPrefix(s, "[")
}

// UnmarshalJSON unmarshals Relationships from JSON
func (r *Relationships) UnmarshalJSON(b []byte) error {
    var rels map[string]struct {
        Data json.RawMessage `json:"data"`
    }
    err := json.Unmarshal(b, &rels)
    if err != nil {
        return err
    }
    for key, data := range rels {
        var rc RelationshipContainer
        if isJSONArray(data.Data) {
            var relationships []Relationship
            err = json.Unmarshal(data.Data, &relationships)
            if err != nil {
                return err
            }
            rc.Relationships = relationships
            rc.OneToOne = false
        } else {
            var relationship Relationship
            err := json.Unmarshal(data.Data, &relationship)
            if err != nil {
                return err
            }
            rc.Relationships = []Relationship{relationship}
            rc.OneToOne = true
        }
        if *r == nil {
            *r = make(Relationships)
        }
        (*r)[key] = rc
    }
    return nil
}