internal/app/state: improve handles internals

This replaces the Store interface with something better reflecting the underlying data format for #19. An implementation of Store is provided on top of the new code to ease transition.

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

internal/app/state/state.go

@@ -2,9 +2,16 @@
 package state
 
 import (
+	"strconv"
+
+	"hakurei.app/container/check"
 	"hakurei.app/hst"
+	"hakurei.app/internal/lockedfile"
+	"hakurei.app/message"
 )
 
+/* this provides an implementation of Store on top of the improved state tracking to ease in the changes */
+
 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.
@@ -16,6 +23,13 @@ type Store interface {
 	List() (identities []int, err error)
 }
 
+// NewMulti returns an instance of the multi-file store.
+func NewMulti(msg message.Msg, prefix *check.Absolute) Store {
+	store := &stateStore{msg: msg, base: prefix.Append("state")}
+	store.fileMu = lockedfile.MutexAt(store.base.Append(storeMutexName).String())
+	return store
+}
+
 // Cursor provides access to the store of an identity.
 type Cursor interface {
 	Save(state *hst.State) error
@@ -23,3 +37,62 @@ type Cursor interface {
 	Load() (map[hst.ID]*hst.State, error)
 	Len() (int, error)
 }
+
+// do implements stateStore.Do on storeHandle.
+func (h *storeHandle) do(f func(c Cursor)) (bool, error) {
+	if unlock, err := h.fileMu.Lock(); err != nil {
+		return false, &hst.AppError{Step: "acquire lock on store segment " + strconv.Itoa(h.identity), Err: err}
+	} else {
+		defer unlock()
+	}
+
+	f(h)
+	return true, nil
+}
+
+/* these compatibility methods must only be called while fileMu is held */
+
+func (h *storeHandle) Save(state *hst.State) error {
+	return (&stateEntryHandle{nil, h.path.Append(state.ID.String()), state.ID}).save(state)
+}
+
+func (h *storeHandle) Destroy(id hst.ID) error {
+	return (&stateEntryHandle{nil, h.path.Append(id.String()), id}).destroy()
+}
+
+func (h *storeHandle) Load() (map[hst.ID]*hst.State, error) {
+	entries, n, err := h.entries()
+	if err != nil {
+		return nil, err
+	}
+
+	r := make(map[hst.ID]*hst.State, n)
+	for eh := range entries {
+		if eh.decodeErr != nil {
+			err = eh.decodeErr
+			break
+		}
+		var s hst.State
+		if _, err = eh.load(&s); err != nil {
+			break
+		}
+		r[eh.ID] = &s
+	}
+	return r, err
+}
+
+func (h *storeHandle) Len() (int, error) {
+	entries, _, err := h.entries()
+	if err != nil {
+		return -1, err
+	}
+
+	var n int
+	for eh := range entries {
+		if eh.decodeErr != nil {
+			err = eh.decodeErr
+		}
+		n++
+	}
+	return n, err
+}