// MediaType implements the media type definition DSL. A media type definition describes the
// representation of a resource used in a response body.
//
// Media types are defined with a unique identifier as defined by RFC6838. The identifier also
// defines the default value for the Content-Type header of responses. The ContentType DSL allows
// overridding the default as shown in the example below.
//
// The media type definition includes a listing of all the potential attributes that can appear in
// the body. Views specify which of the attributes are actually rendered so that the same media type
// definition may represent multiple rendering of a given resource representation.
//
// All media types must define a view named "default". This view is used to render the media type in
// response bodies when no other view is specified.
//
// A media type definition may also define links to other media types. This is done by first
// defining an attribute for the linked-to media type and then referring to that attribute in the
// Links DSL. Views may then elect to render one or the other or both. Links are rendered using the
// special "link" view. Media types that are linked to must define that view. Here is an example
// showing all the possible media type sub-definitions:
//
// MediaType("application/vnd.goa.example.bottle", func() {
// Description("A bottle of wine")
// TypeName("BottleMedia") // Override default generated name
// ContentType("application/json") // Override default Content-Type header value
// Attributes(func() {
// Attribute("id", Integer, "ID of bottle")
// Attribute("href", String, "API href of bottle")
// Attribute("account", Account, "Owner account")
// Attribute("origin", Origin, "Details on wine origin")
// Links(func() {
// Link("account") // Defines link to Account media type
// Link("origin", "tiny") // Set view used to render link if not "link"
// })
// Required("id", "href")
// })
// View("default", func() {
// Attribute("id")
// Attribute("href")
// Attribute("links") // Renders links
// })
// View("extended", func() {
// Attribute("id")
// Attribute("href")
// Attribute("account") // Renders account inline
// Attribute("origin") // Renders origin inline
// Attribute("links") // Renders links
// })
// })
//
// This function returns the media type definition so it can be referred to throughout the apidsl.
func MediaType(identifier string, apidsl func()) *design.MediaTypeDefinition {
if design.Design.MediaTypes == nil {
design.Design.MediaTypes = make(map[string]*design.MediaTypeDefinition)
}
if !dslengine.IsTopLevelDefinition() {
dslengine.IncompatibleDSL()
return nil
}
// Validate Media Type
identifier, params, err := mime.ParseMediaType(identifier)
if err != nil {
dslengine.ReportError("invalid media type identifier %#v: %s",
identifier, err)
// We don't return so that other errors may be
// captured in this one run.
identifier = "text/plain"
}
canonicalID := design.CanonicalIdentifier(identifier)
// Validate that media type identifier doesn't clash
if _, ok := design.Design.MediaTypes[canonicalID]; ok {
dslengine.ReportError("media type %#v with canonical identifier %#v is defined twice", identifier, canonicalID)
return nil
}
identifier = mime.FormatMediaType(identifier, params)
lastPart := identifier
lastPartIndex := strings.LastIndex(identifier, "/")
if lastPartIndex > -1 {
lastPart = identifier[lastPartIndex+1:]
}
plusIndex := strings.Index(lastPart, "+")
if plusIndex > 0 {
lastPart = lastPart[:plusIndex]
}
lastPart = strings.TrimPrefix(lastPart, "vnd.")
elems := strings.Split(lastPart, ".")
for i, e := range elems {
elems[i] = strings.Title(e)
}
typeName := strings.Join(elems, "")
if typeName == "" {
mediaTypeCount++
typeName = fmt.Sprintf("MediaType%d", mediaTypeCount)
}
// Now save the type in the API media types map
mt := design.NewMediaTypeDefinition(typeName, identifier, apidsl)
design.Design.MediaTypes[canonicalID] = mt
return mt
}
// MediaType implements the media type definition apidsl. A media type definition describes the
// representation of a resource used in a response body. This includes listing all the *potential*
// resource attributes that can appear in the body. Views specify which of the attributes are
// actually rendered so that the same media type definition may represent multiple rendering of a
// given resource representation.
//
// All media types must define a view named "default". This view is used to render the media type in
// response bodies when no other view is specified.
//
// A media type definition may also define links to other media types. This is done by first
// defining an attribute for the linked-to media type and then referring to that attribute in the
// Links apidsl. Views may then elect to render one or the other or both. Links are rendered using the
// special "link" view. Media types that are linked to must define that view. Here is an example
// showing all the possible media type sub-definitions:
//
// MediaType("application/vnd.goa.example.bottle", func() {
// Description("A bottle of wine")
// TypeName("BottleMedia") // Optionally override the default generated name
// Attributes(func() {
// Attribute("id", Integer, "ID of bottle")
// Attribute("href", String, "API href of bottle")
// Attribute("account", Account, "Owner account")
// Attribute("origin", Origin, "Details on wine origin")
// Links(func() {
// Link("account") // Defines a link to the Account media type
// Link("origin", "tiny") // Overrides the default view used to render links
// })
// Required("id", "href")
// })
// View("default", func() {
// Attribute("id")
// Attribute("href")
// Attribute("links") // Default view renders links
// })
// View("extended", func() {
// Attribute("id")
// Attribute("href")
// Attribute("account") // Extended view renders account inline
// Attribute("origin") // Extended view renders origin inline
// Attribute("links") // Extended view also renders links
// })
// })
//
// This function returns the media type definition so it can be referred to throughout the apidsl.
func MediaType(identifier string, apidsl func()) *design.MediaTypeDefinition {
if design.Design.MediaTypes == nil {
design.Design.MediaTypes = make(map[string]*design.MediaTypeDefinition)
}
if !dslengine.IsTopLevelDefinition() {
dslengine.IncompatibleDSL()
return nil
}
// Validate Media Type
identifier, params, err := mime.ParseMediaType(identifier)
if err != nil {
dslengine.ReportError("invalid media type identifier %#v: %s",
identifier, err)
// We don't return so that other errors may be
// captured in this one run.
identifier = "text/plain"
}
canonicalID := design.CanonicalIdentifier(identifier)
// Validate that media type identifier doesn't clash
if _, ok := design.Design.MediaTypes[canonicalID]; ok {
dslengine.ReportError("media type %#v is defined twice", identifier)
return nil
}
parts := strings.Split(identifier, "+")
// Make sure it has the `+json` suffix (TBD update when goa supports other encodings)
if len(parts) > 1 {
parts = parts[1:]
found := false
for _, part := range parts {
if part == "json" {
found = true
break
}
}
if !found {
identifier += "+json"
}
}
identifier = mime.FormatMediaType(identifier, params)
// Concoct a Go type name from the identifier, should it be possible to set it in the apidsl?
// pros: control the type name generated, cons: not needed in apidsl, adds one more thing to worry about
lastPart := identifier
lastPartIndex := strings.LastIndex(identifier, "/")
if lastPartIndex > -1 {
lastPart = identifier[lastPartIndex+1:]
}
plusIndex := strings.Index(lastPart, "+")
if plusIndex > 0 {
lastPart = lastPart[:plusIndex]
}
lastPart = strings.TrimPrefix(lastPart, "vnd.")
elems := strings.Split(lastPart, ".")
for i, e := range elems {
elems[i] = strings.Title(e)
}
typeName := strings.Join(elems, "")
if typeName == "" {
mediaTypeCount++
typeName = fmt.Sprintf("MediaType%d", mediaTypeCount)
}
// Now save the type in the API media types map
mt := design.NewMediaTypeDefinition(typeName, identifier, apidsl)
design.Design.MediaTypes[canonicalID] = mt
return mt
}
// CollectionOf creates a collection media type from its element media type. A collection media
// type represents the content of responses that return a collection of resources such as "list"
// actions. This function can be called from any place where a media type can be used.
// The resulting media type identifier is built from the element media type by appending the media
// type parameter "type" with value "collection".
func CollectionOf(v interface{}, apidsl ...func()) *design.MediaTypeDefinition {
var m *design.MediaTypeDefinition
var ok bool
m, ok = v.(*design.MediaTypeDefinition)
if !ok {
if id, ok := v.(string); ok {
m = design.Design.MediaTypes[design.CanonicalIdentifier(id)]
}
}
if m == nil {
dslengine.ReportError("invalid CollectionOf argument: not a media type and not a known media type identifier")
// don't return nil to avoid panics, the error will get reported at the end
return design.NewMediaTypeDefinition("InvalidCollection", "text/plain", nil)
}
id := m.Identifier
mediatype, params, err := mime.ParseMediaType(id)
if err != nil {
dslengine.ReportError("invalid media type identifier %#v: %s", id, err)
// don't return nil to avoid panics, the error will get reported at the end
return design.NewMediaTypeDefinition("InvalidCollection", "text/plain", nil)
}
hasType := false
for param := range params {
if param == "type" {
hasType = true
break
}
}
if !hasType {
params["type"] = "collection"
}
id = mime.FormatMediaType(mediatype, params)
canonical := design.CanonicalIdentifier(id)
if mt, ok := design.GeneratedMediaTypes[canonical]; ok {
// Already have a type for this collection, reuse it.
return mt
}
mt := design.NewMediaTypeDefinition("", id, func() {
if mt, ok := mediaTypeDefinition(); ok {
// Cannot compute collection type name before element media type DSL has executed
// since the DSL may modify element type name via the TypeName function.
mt.TypeName = m.TypeName + "Collection"
mt.AttributeDefinition = &design.AttributeDefinition{Type: ArrayOf(m)}
if len(apidsl) > 0 {
dslengine.Execute(apidsl[0], mt)
}
if mt.Views == nil {
// If the apidsl didn't create any views (or there is no apidsl at all)
// then inherit the views from the collection element.
mt.Views = make(map[string]*design.ViewDefinition)
for n, v := range m.Views {
mt.Views[n] = v
}
}
}
})
// Do not execute the apidsl right away, will be done last to make sure the element apidsl has run
// first.
design.GeneratedMediaTypes[canonical] = mt
return mt
}
// CollectionOf creates a collection media type from its element media type. A collection media
// type represents the content of responses that return a collection of resources such as "list"
// actions. This function can be called from any place where a media type can be used.
// The resulting media type identifier is built from the element media type by appending the media
// type parameter "type" with value "collection".
func CollectionOf(v interface{}, apidsl ...func()) *design.MediaTypeDefinition {
if design.GeneratedMediaTypes == nil {
design.GeneratedMediaTypes = make(design.MediaTypeRoot)
dslengine.Roots = append(dslengine.Roots, design.GeneratedMediaTypes)
}
var m *design.MediaTypeDefinition
var ok bool
m, ok = v.(*design.MediaTypeDefinition)
if !ok {
if id, ok := v.(string); ok {
m = design.Design.MediaTypes[design.CanonicalIdentifier(id)]
}
}
if m == nil {
dslengine.ReportError("invalid CollectionOf argument: not a media type and not a known media type identifier")
return nil
}
id := m.Identifier
mediatype, params, err := mime.ParseMediaType(id)
if err != nil {
dslengine.ReportError("invalid media type identifier %#v: %s", id, err)
return nil
}
hasType := false
for param := range params {
if param == "type" {
hasType = true
break
}
}
if !hasType {
params["type"] = "collection"
}
id = mime.FormatMediaType(mediatype, params)
typeName := m.TypeName + "Collection"
if mt, ok := design.GeneratedMediaTypes[typeName]; ok {
// Already have a type for this collection, reuse it.
return mt
}
mt := design.NewMediaTypeDefinition(typeName, id, func() {
if mt, ok := mediaTypeDefinition(true); ok {
mt.TypeName = typeName
mt.AttributeDefinition = &design.AttributeDefinition{Type: ArrayOf(m)}
mt.APIVersions = m.APIVersions
if len(apidsl) > 0 {
dslengine.Execute(apidsl[0], mt)
}
if mt.Views == nil {
// If the apidsl didn't create any views (or there is no apidsl at all)
// then inherit the views from the collection element.
mt.Views = make(map[string]*design.ViewDefinition)
for n, v := range m.Views {
mt.Views[n] = v
}
}
}
})
// Do not execute the apidsl right away, will be done last to make sure the element apidsl has run
// first.
design.GeneratedMediaTypes[typeName] = mt
return mt
}