constraints

type ConflictResolver func(attrValues map[string]interface{}) error

type ConstraintsValue struct {
	Target *Value
}

type Validator interface {

	// RegisterConflicts is used to define cross-constraint override behaviour.
	// The red and blue attribute lists contain attribute names which conflict
	// with those in the other list.
	// When two constraints conflict:
	//  it is an error to set both constraints in the same constraints Value.
	//  when a constraints Value overrides another which specifies a conflicting
	//   attribute, the attribute in the overridden Value is cleared.
	RegisterConflicts(reds, blues []string)

	// RegisterConflictResolver defines a resolver between two conflicting constraints.
	// When there is a registered conflict between two contraints, it can be resolved by
	// calling the resolver, if it returns a nil error, the conflict is considered resolved.
	RegisterConflictResolver(red, blue string, resolver ConflictResolver)

	// RegisterUnsupported records attributes which are not supported by a constraints Value.
	RegisterUnsupported(unsupported []string)

	// RegisterVocabulary records allowed values for the specified constraint attribute.
	// allowedValues is expected to be a slice/array but is declared as interface{} so
	// that vocabs of different types can be passed in.
	RegisterVocabulary(attributeName string, allowedValues interface{})

	// Validate returns an error if the given constraints are not valid, and also
	// any unsupported attributes.
	Validate(cons Value) ([]string, error)

	// Merge merges cons into consFallback, with any conflicting attributes from cons
	// overriding those from consFallback.
	Merge(consFallback, cons Value) (Value, error)

	// UpdateVocabulary merges new attribute values with existing values.
	// This method does not overwrite or delete values, i.e.
	//     if existing values are {a, b}
	//     and new values are {c, d},
	//     then the merge result would be {a, b, c, d}.
	UpdateVocabulary(attributeName string, newValues interface{})
}

type Value struct {

	// Arch, if not nil or empty, indicates that a machine must run the named
	// architecture.
	Arch *string `json:"arch,omitempty" yaml:"arch,omitempty"`

	// Container, if not nil, indicates that a machine must be the specified container type.
	Container *instance.ContainerType `json:"container,omitempty" yaml:"container,omitempty"`

	// CpuCores, if not nil, indicates that a machine must have at least that
	// number of effective cores available.
	CpuCores *uint64 `json:"cores,omitempty" yaml:"cores,omitempty"`

	// CpuPower, if not nil, indicates that a machine must have at least that
	// amount of CPU power available, where 100 CpuPower is considered to be
	// equivalent to 1 Amazon ECU (or, roughly, a single 2007-era Xeon).
	CpuPower *uint64 `json:"cpu-power,omitempty" yaml:"cpu-power,omitempty"`

	// Mem, if not nil, indicates that a machine must have at least that many
	// megabytes of RAM.
	Mem *uint64 `json:"mem,omitempty" yaml:"mem,omitempty"`

	// RootDisk, if not nil, indicates that a machine must have at least
	// that many megabytes of disk space available in the root disk. In
	// providers where the root disk is configurable at instance startup
	// time, an instance with the specified amount of disk space in the OS
	// disk might be requested.
	RootDisk *uint64 `json:"root-disk,omitempty" yaml:"root-disk,omitempty"`

	// RootDiskSource, if specified, determines what storage the root
	// disk should be allocated from. This will be provider specific -
	// in the case of vSphere it identifies the datastore the root
	// disk file should be created in.
	RootDiskSource *string `json:"root-disk-source,omitempty" yaml:"root-disk-source,omitempty"`

	// Tags, if not nil, indicates tags that the machine must have applied to it.
	// An empty list is treated the same as a nil (unspecified) list, except an
	// empty list will override any default tags, where a nil list will not.
	Tags *[]string `json:"tags,omitempty" yaml:"tags,omitempty"`

	// InstanceRole, if not nil, indicates that the specified role/profile for
	// the given cloud should be used. Only valid for clouds which support
	// instance roles. Currently only for AWS with instance-profiles
	InstanceRole *string `json:"instance-role,omitempty" yaml:"instance-role,omitempty"`

	// InstanceType, if not nil, indicates that the specified cloud instance type
	// be used. Only valid for clouds which support instance types.
	InstanceType *string `json:"instance-type,omitempty" yaml:"instance-type,omitempty"`

	// Spaces, if not nil, holds a list of juju network spaces that
	// should be available (or not) on the machine. Positive and
	// negative values are accepted, and the difference is the latter
	// have a "^" prefix to the name.
	Spaces *[]string `json:"spaces,omitempty" yaml:"spaces,omitempty"`

	// VirtType, if not nil or empty, indicates that a machine must run the named
	// virtual type. Only valid for clouds with multi-hypervisor support.
	VirtType *string `json:"virt-type,omitempty" yaml:"virt-type,omitempty"`

	// Zones, if not nil, holds a list of availability zones limiting where
	// the machine can be located.
	Zones *[]string `json:"zones,omitempty" yaml:"zones,omitempty"`

	// AllocatePublicIP, if nil or true, signals that machines should be
	// created with a public IP address instead of a cloud local one.
	// The default behaviour if the value is not specified is to allocate
	// a public IP so that public cloud behaviour works out of the box.
	AllocatePublicIP *bool `json:"allocate-public-ip,omitempty" yaml:"allocate-public-ip,omitempty"`

	// ImageID, if not nil, indicates that a machine must use the specified
	// image. This is provider specific, and for the moment is only
	// implemented on MAAS clouds.
	ImageID *string `json:"image-id,omitempty" yaml:"image-id,omitempty"`
}