refactor(v2): init eventstore package (#7806)

* refactor(v2): init database package

* refactor(v2): init eventstore package

* add mock package

* test query constructors

* option based push analog to query

internal/v2/eventstore/push.go

@@ -0,0 +1,190 @@
+package eventstore
+
+import (
+	"context"
+	"database/sql"
+)
+
+type Pusher interface {
+	healthier
+	// Push writes the intents to the storage
+	// if an intent implements [PushReducerIntent] [PushReducerIntent.Reduce] is called after
+	// the intent was stored
+	Push(ctx context.Context, intent *PushIntent) error
+}
+
+func NewPushIntent(instance string, opts ...PushOpt) *PushIntent {
+	intent := &PushIntent{
+		instance: instance,
+	}
+
+	for _, opt := range opts {
+		opt(intent)
+	}
+
+	return intent
+}
+
+type PushIntent struct {
+	instance   string
+	reducer    Reducer
+	tx         *sql.Tx
+	aggregates []*PushAggregate
+}
+
+func (pi *PushIntent) Instance() string {
+	return pi.instance
+}
+
+func (pi *PushIntent) Reduce(events ...*Event[StoragePayload]) error {
+	if pi.reducer == nil {
+		return nil
+	}
+	return pi.reducer.Reduce(events...)
+}
+
+func (pi *PushIntent) Tx() *sql.Tx {
+	return pi.tx
+}
+
+func (pi *PushIntent) Aggregates() []*PushAggregate {
+	return pi.aggregates
+}
+
+type PushOpt func(pi *PushIntent)
+
+func PushReducer(reducer Reducer) PushOpt {
+	return func(pi *PushIntent) {
+		pi.reducer = reducer
+	}
+}
+
+func PushTx(tx *sql.Tx) PushOpt {
+	return func(pi *PushIntent) {
+		pi.tx = tx
+	}
+}
+
+func AppendAggregate(owner, typ, id string, opts ...PushAggregateOpt) PushOpt {
+	return AppendAggregates(NewPushAggregate(owner, typ, id, opts...))
+}
+
+func AppendAggregates(aggregates ...*PushAggregate) PushOpt {
+	return func(pi *PushIntent) {
+		for _, aggregate := range aggregates {
+			aggregate.parent = pi
+		}
+		pi.aggregates = append(pi.aggregates, aggregates...)
+	}
+}
+
+type PushAggregate struct {
+	parent *PushIntent
+	// typ of the aggregate
+	typ string
+	// id of the aggregate
+	id string
+	// owner of the aggregate
+	owner string
+	// Commands is an ordered list of changes on the aggregate
+	commands []Command
+	// CurrentSequence checks the current state of the aggregate.
+	// The following types match the current sequence of the aggregate as described:
+	// * nil or [SequenceIgnore]: Not relevant to add the commands
+	// * [SequenceMatches]: Must exactly match
+	// * [SequenceAtLeast]: Must be >= the given sequence
+	currentSequence CurrentSequence
+}
+
+func NewPushAggregate(owner, typ, id string, opts ...PushAggregateOpt) *PushAggregate {
+	pa := &PushAggregate{
+		typ:   typ,
+		id:    id,
+		owner: owner,
+	}
+
+	for _, opt := range opts {
+		opt(pa)
+	}
+
+	return pa
+}
+
+func (pa *PushAggregate) Type() string {
+	return pa.typ
+}
+
+func (pa *PushAggregate) ID() string {
+	return pa.id
+}
+
+func (pa *PushAggregate) Owner() string {
+	return pa.owner
+}
+
+func (pa *PushAggregate) Commands() []Command {
+	return pa.commands
+}
+
+func (pa *PushAggregate) Aggregate() *Aggregate {
+	return &Aggregate{
+		ID:       pa.id,
+		Type:     pa.typ,
+		Owner:    pa.owner,
+		Instance: pa.parent.instance,
+	}
+}
+
+func (pa *PushAggregate) CurrentSequence() CurrentSequence {
+	return pa.currentSequence
+}
+
+type PushAggregateOpt func(pa *PushAggregate)
+
+func SetCurrentSequence(currentSequence CurrentSequence) PushAggregateOpt {
+	return func(pa *PushAggregate) {
+		pa.currentSequence = currentSequence
+	}
+}
+
+func IgnoreCurrentSequence() PushAggregateOpt {
+	return func(pa *PushAggregate) {
+		pa.currentSequence = SequenceIgnore()
+	}
+}
+
+func CurrentSequenceMatches(sequence uint32) PushAggregateOpt {
+	return func(pa *PushAggregate) {
+		pa.currentSequence = SequenceMatches(sequence)
+	}
+}
+
+func CurrentSequenceAtLeast(sequence uint32) PushAggregateOpt {
+	return func(pa *PushAggregate) {
+		pa.currentSequence = SequenceAtLeast(sequence)
+	}
+}
+
+func AppendCommands(commands ...Command) PushAggregateOpt {
+	return func(pa *PushAggregate) {
+		pa.commands = append(pa.commands, commands...)
+	}
+}
+
+type Command interface {
+	// Creator is the id of the user which created the action
+	Creator() string
+	// Type describes the action it's in the past (e.g. user.created)
+	Type() string
+	// Revision of the action
+	Revision() uint16
+	// Payload returns the payload of the event. It represent the changed fields by the event
+	// valid types are:
+	// * nil: no payload
+	// * struct: which can be marshalled to json
+	// * pointer to struct: which can be marshalled to json
+	// * []byte: json marshalled data
+	Payload() any
+	// UniqueConstraints should be added for unique attributes of an event, if nil constraints will not be checked
+	UniqueConstraints() []*UniqueConstraint
+}