context.go

package analytics

import (
	"encoding/json"
	"net"
	"reflect"
)

// Context provides the representation of the `context` object as defined in
// https://segment.com/docs/spec/common/#context
type Context struct {
	App       AppInfo      `json:"app,omitempty"`
	Campaign  CampaignInfo `json:"campaign,omitempty"`
	Device    DeviceInfo   `json:"device,omitempty"`
	Library   LibraryInfo  `json:"library,omitempty"`
	Location  LocationInfo `json:"location,omitempty"`
	Network   NetworkInfo  `json:"network,omitempty"`
	OS        OSInfo       `json:"os,omitempty"`
	Page      PageInfo     `json:"page,omitempty"`
	Referrer  ReferrerInfo `json:"referrer,omitempty"`
	Screen    ScreenInfo   `json:"screen,omitempty"`
	IP        net.IP       `json:"ip,omitempty"`
	Locale    string       `json:"locale,omitempty"`
	Timezone  string       `json:"timezone,omitempty"`
	UserAgent string       `json:"userAgent,omitempty"`
	Traits    Traits       `json:"traits,omitempty"`

	// This map is used to allow extensions to the context specifications that
	// may not be documented or could be introduced in the future.
	// The fields of this map are inlined in the serialized context object,
	// there is no actual "extra" field in the JSON representation.
	Extra map[string]interface{} `json:"-"`
}

// AppInfo provides the representation of the `context.app` object as defined
// in https://segment.com/docs/spec/common/#context
type AppInfo struct {
	Name      string `json:"name,omitempty"`
	Version   string `json:"version,omitempty"`
	Build     string `json:"build,omitempty"`
	Namespace string `json:"namespace,omitempty"`
}

// CampaignInfo provides the representation of the `context.campaign` object as
// defined in https://segment.com/docs/spec/common/#context
type CampaignInfo struct {
	Name    string `json:"name,omitempty"`
	Source  string `json:"source,omitempty"`
	Medium  string `json:"medium,omitempty"`
	Term    string `json:"term,omitempty"`
	Content string `json:"content,omitempty"`
}

// DeviceInfo provides the representation of the `context.device` object as
// defined in https://segment.com/docs/spec/common/#context
type DeviceInfo struct {
	Id            string `json:"id,omitempty"`
	Manufacturer  string `json:"manufacturer,omitempty"`
	Model         string `json:"model,omitempty"`
	Name          string `json:"name,omitempty"`
	Type          string `json:"type,omitempty"`
	Version       string `json:"version,omitempty"`
	AdvertisingID string `json:"advertisingId,omitempty"`
}

// LibraryInfo provides the representation of the `context.library` object as
// defined in https://segment.com/docs/spec/common/#context
type LibraryInfo struct {
	Name    string `json:"name,omitempty"`
	Version string `json:"version,omitempty"`
}

// LocationInfo provides the representation of the `context.location` object as
// defined in https://segment.com/docs/spec/common/#context
type LocationInfo struct {
	City      string  `json:"city,omitempty"`
	Country   string  `json:"country,omitempty"`
	Region    string  `json:"region,omitempty"`
	Latitude  float64 `json:"latitude,omitempty"`
	Longitude float64 `json:"longitude,omitempty"`
	Speed     float64 `json:"speed,omitempty"`
}

// NetworkInfo provides the representation of the `context.network` object as
// defined in https://segment.com/docs/spec/common/#context
type NetworkInfo struct {
	Bluetooth bool   `json:"bluetooth,omitempty"`
	Cellular  bool   `json:"cellular,omitempty"`
	WIFI      bool   `json:"wifi,omitempty"`
	Carrier   string `json:"carrier,omitempty"`
}

// OSInfo provides the representation of the `context.os` object as defined
// in https://segment.com/docs/spec/common/#context
type OSInfo struct {
	Name    string `json:"name,omitempty"`
	Version string `json:"version,omitempty"`
}

// PageInfo provides the representation of the `context.page` object as
// defined in https://segment.com/docs/spec/common/#context
type PageInfo struct {
	Hash     string `json:"hash,omitempty"`
	Path     string `json:"path,omitempty"`
	Referrer string `json:"referrer,omitempty"`
	Search   string `json:"search,omitempty"`
	Title    string `json:"title,omitempty"`
	URL      string `json:"url,omitempty"`
}

// ReferrerInfo provides the representation of the `context.referrer` object as
// defined in https://segment.com/docs/spec/common/#context
type ReferrerInfo struct {
	Type string `json:"type,omitempty"`
	Name string `json:"name,omitempty"`
	URL  string `json:"url,omitempty"`
	Link string `json:"link,omitempty"`
}

// ScreenInfo provides the representation of the `context.screen` object as
// defined in https://segment.com/docs/spec/common/#context
type ScreenInfo struct {
	Density int `json:"density,omitempty"`
	Width   int `json:"width,omitempty"`
	Height  int `json:"height,omitempty"`
}

// MarshalJSON satisfies the `json.Marshaler` interface. We have to flatten out
// the `Extra` field but the standard json package doesn't support it yet.
// Implementing this interface allows us to override the default marshaling of
// the context object and to the inlining ourselves.
//
// Related discussion: https://github.com/golang/go/issues/6213
func (ctx Context) MarshalJSON() ([]byte, error) {
	v := reflect.ValueOf(ctx)
	n := v.NumField()
	m := make(map[string]interface{}, n+len(ctx.Extra))

	// Copy the `Extra` map into the map representation of the context, it is
	// important to do this operation before going through the actual struct
	// fields so the latter take precendence and override duplicated values
	// that would be set in the extensions.
	for name, value := range ctx.Extra {
		m[name] = value
	}

	return json.Marshal(structToMap(v, m))
}