1 files changed, 90 insertions, 0 deletions
diff --git a/pkg/contracts/contracts.go b/pkg/contracts/contracts.go
new file mode 100644
index 0000000..a8b4201
--- /dev/null
+++ b/pkg/contracts/contracts.go
@@ -0,0 +1,90 @@
+package contracts
+
+// Entity is implemented by every type Icinga DB should synchronize.
+type Entity interface {
+	Fingerprinter
+	IDer
+}
+
+// Fingerprinter is implemented by every entity that uniquely identifies itself.
+type Fingerprinter interface {
+	// Fingerprint returns the value that uniquely identifies the entity.
+	Fingerprint() Fingerprinter
+}
+
+// ID is a unique identifier of an entity.
+type ID interface {
+	// String returns the string representation form of the ID.
+	// The String method is used to use the ID in functions
+	// where it needs to be compared or hashed.
+	String() string
+}
+
+// IDer is implemented by every entity that uniquely identifies itself.
+type IDer interface {
+	ID() ID   // ID returns the ID.
+	SetID(ID) // SetID sets the ID.
+}
+
+// Equaler is implemented by every type that is comparable.
+type Equaler interface {
+	Equal(Equaler) bool // Equal checks for equality.
+}
+
+// Checksum is a unique identifier of an entity.
+type Checksum interface {
+	Equaler
+	// String returns the string representation form of the Checksum.
+	// The String method is used to use the Checksum in functions
+	// where it needs to be compared or hashed.
+	String() string
+}
+
+// Checksumer is implemented by every entity with a checksum.
+type Checksumer interface {
+	Checksum() Checksum   // Checksum returns the Checksum.
+	SetChecksum(Checksum) // SetChecksum sets the Checksum.
+}
+
+// EntityFactoryFunc knows how to create an Entity.
+type EntityFactoryFunc func() Entity
+
+// Waiter implements the Wait method,
+// which blocks until execution is complete.
+type Waiter interface {
+	Wait() error // Wait waits for execution to complete.
+}
+
+// The WaiterFunc type is an adapter to allow the use of ordinary functions as Waiter.
+// If f is a function with the appropriate signature, WaiterFunc(f) is a Waiter that calls f.
+type WaiterFunc func() error
+
+// Wait implements the Waiter interface.
+func (f WaiterFunc) Wait() error {
+	return f()
+}
+
+// Initer implements the Init method,
+// which initializes the object in addition to zeroing.
+type Initer interface {
+	Init() // Init initializes the object.
+}
+
+// Upserter implements the Upsert method,
+// which returns a part of the object for ON DUPLICATE KEY UPDATE.
+type Upserter interface {
+	Upsert() interface{} // Upsert partitions the object.
+}
+
+// TableNamer implements the TableName method,
+// which returns the table of the object.
+type TableNamer interface {
+	TableName() string // TableName tells the table.
+}
+
+// Scoper implements the Scope method,
+// which returns a struct specifying the WHERE conditions that
+// entities must satisfy in order to be SELECTed.
+type Scoper interface {
+	Scope() interface{}
+}