app: remove split implementation

It is completely nonsensical and highly error-prone to have multiple implementations of this in the same build. This should be switched at compile time instead therefore the split packages are pointless.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/app/state/state.go

@@ -0,0 +1,49 @@
+// Package state provides cross-process state tracking for hakurei container instances.
+package state
+
+import (
+	"errors"
+	"io"
+	"time"
+
+	"hakurei.app/hst"
+)
+
+var ErrNoConfig = errors.New("state does not contain config")
+
+type Entries map[ID]*State
+
+type Store interface {
+	// Do calls f exactly once and ensures store exclusivity until f returns.
+	// Returns whether f is called and any errors during the locking process.
+	// Cursor provided to f becomes invalid as soon as f returns.
+	Do(aid int, f func(c Cursor)) (ok bool, err error)
+
+	// List queries the store and returns a list of aids known to the store.
+	// Note that some or all returned aids might not have any active apps.
+	List() (aids []int, err error)
+
+	// Close releases any resources held by Store.
+	Close() error
+}
+
+// Cursor provides access to the store
+type Cursor interface {
+	Save(state *State, configWriter io.WriterTo) error
+	Destroy(id ID) error
+	Load() (Entries, error)
+	Len() (int, error)
+}
+
+// State is an instance state
+type State struct {
+	// hakurei instance id
+	ID ID `json:"instance"`
+	// child process PID value
+	PID int `json:"pid"`
+	// sealed app configuration
+	Config *hst.Config `json:"config"`
+
+	// process start time
+	Time time.Time `json:"time"`
+}