Version the package and command from the commit

[onechat] / memory.go

diff --git a/memory.go b/memory.go
index ca8277c629889037c17c4ef221bcf94c049f0e8c..7cbcce68c40f4b06382e3c8f3e71dfcbb3388d26 100644 (file)
--- a/memory.go
+++ b/memory.go
@@ -5,6 +5,7 @@ import (
        "encoding/json"
        "errors"
        "fmt"
        "encoding/json"
        "errors"
        "fmt"

+       "log"

        "os"
        "path/filepath"
        "strings"
        "os"
        "path/filepath"
        "strings"


@@ -12,24 +13,73 @@ import (
        "time"
 )
 
        "time"
 )
 

-// errNoView tells that a chat has messages but no saved view.
-var errNoView = errors.New("the chat has messages but no saved view")
+var (
+       // errMemoryNoView tells that a chat has messages but no saved view.
+       errMemoryNoView = errors.New("the chat has messages but no saved view")
+
+       // errMemoryUnsettled tells that a line of the view stays pending,
+       // because its build failed.
+       errMemoryUnsettled = errors.New("a summary of the view failed, and it is tried again at the next message")
+)
+
+// openMemory opens the chat in root and starts the builds that are ready. The
+// clock gives the dates of new messages and the days of new nodes. logger gets
+// one line for each failed build. The builds stop when ctx ends or at Close.
+func openMemory(ctx context.Context, root string, clock func() time.Time, summarizer Summarizer, logger *log.Logger) (*Memory, error) {
+       log, err := openLog(ctx, root, clock)
+       if err != nil {
+               return nil, err
+       }
+
+       m := &Memory{
+               root:       root,
+               log:        log,
+               queue:      newBuildQueue(),
+               summarizer: summarizer,
+               logger:     logger,
+               changed:    make(chan struct{}),
+       }
+
+       m.ctx, m.cancel = context.WithCancel(ctx)
+
+       m.syncer, err = openSyncer(root)
+       if err != nil {
+               return nil, errors.Join(err, m.Close())
+       }
+
+       m.tree, err = openTree(ctx, root, log.Len(), clock)
+       if err != nil {
+               return nil, errors.Join(err, m.Close())
+       }
+
+       err = m.load()
+       if err != nil {
+               return nil, errors.Join(fmt.Errorf("load view: %w", err), m.Close())
+       }
+
+       err = m.restoreQueue()
+       if err != nil {
+               return nil, errors.Join(fmt.Errorf("restore build queue: %w", err), m.Close())
+       }
+
+       err = m.catchUp()
+       if err != nil {
+               return nil, errors.Join(err, m.Close())
+       }
+
+       m.mutex.Lock()
+       m.syncer.Written()
+       m.dispatch()
+       m.mutex.Unlock()
+
+       return m, nil
+}

 
 // Summarizer builds the text of one node with a model.
 type Summarizer interface {
        Summarize(ctx context.Context, task Task) (string, error)
 }
 
 
 // Summarizer builds the text of one node with a model.
 type Summarizer interface {
        Summarize(ctx context.Context, task Task) (string, error)
 }
 

-// Task is the build of the node (Level, Index). Context is the compaction view
-// for the build. Input holds the source "kind: text" of a leaf, or the two
-// child lines of a merge with their newlines as spaces.
-type Task struct {
-       Level   int
-       Index   int
-       Context string
-       Input   []string
-}
-

 // Memory is the memory of one chat: the message log, the summary tree, the chat
 // view, the compaction view, and the queue of the builds. The compaction view
 // is the chat view merged further, at the limits of 16 to 32 KB. It takes the
 // Memory is the memory of one chat: the message log, the summary tree, the chat
 // view, the compaction view, and the queue of the builds. The compaction view
 // is the chat view merged further, at the limits of 16 to 32 KB. It takes the


@@ -52,106 +102,215 @@ type Memory struct {
        mutex      sync.Mutex
        root       string
        log        *Log
        mutex      sync.Mutex
        root       string
        log        *Log

-       syncer     *syncer
+       syncer     *Syncer

        tree       *Tree
        chat       *View
        cview      *View
        tree       *Tree
        chat       *View
        cview      *View

-       queue      *queue
+       queue      *BuildQueue

        summarizer Summarizer
        summarizer Summarizer

+       logger     *log.Logger

        ctx        context.Context
        cancel     context.CancelFunc
        workers    sync.WaitGroup
        changed    chan struct{}
 }
 
        ctx        context.Context
        cancel     context.CancelFunc
        workers    sync.WaitGroup
        changed    chan struct{}
 }
 

-// viewFile is the content of view.json.
-type viewFile struct {
-       Chat       viewState `json:"chat"`
-       Compaction viewState `json:"compaction"`
-}
+// Close stops the builds, waits for them, makes the writes durable, closes the
+// files of the chat, and releases its lock.
+func (m *Memory) Close() error {
+       m.cancel()
+       m.workers.Wait()

 
 

-// openMemory opens the chat in root and starts the builds that are ready. The
-// clock gives the dates of new messages and the days of new nodes. The builds
-// stop when ctx ends or at Close.
-func openMemory(ctx context.Context, root string, clock func() time.Time, summarizer Summarizer) (*Memory, error) {
-       log, err := openLog(ctx, root, clock)
-       if err != nil {
-               return nil, err
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       var err error
+
+       if m.syncer != nil {
+               err = m.syncer.Close()

        }
 
        }
 

-       m := &Memory{
-               root:       root,
-               log:        log,
-               queue:      newQueue(),
-               summarizer: summarizer,
-               changed:    make(chan struct{}),
+       if m.tree != nil {
+               err = errors.Join(err, m.tree.Close())

        }
 
        }
 

-       m.ctx, m.cancel = context.WithCancel(ctx)
+       return errors.Join(err, m.log.Close())
+}

 
 

-       m.syncer, err = openSyncer(root)
+// Append logs a new message, adds it to the tree and the views, and starts the
+// builds that are ready, also the failed ones.
+func (m *Memory) Append(kind, text string) (Message, error) {
+       return m.AppendDated(kind, text, "")
+}
+
+// AppendDated appends a message with its RFC 3339 date and builds its nodes. An
+// empty date uses the clock, as Append does.
+func (m *Memory) AppendDated(kind, text, date string) (Message, error) {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       message, err := m.log.AppendDated(kind, text, date)

        if err != nil {
        if err != nil {

-               return nil, errors.Join(err, m.Close())
+               return Message{}, fmt.Errorf("append dated log message: %w", err)

        }
 
        }
 

-       m.tree, err = openTree(ctx, root, log.Len(), clock)
+       defer m.syncer.Written()
+
+       err = m.addMessage(message)

        if err != nil {
        if err != nil {

-               return nil, errors.Join(err, m.Close())
+               return Message{}, fmt.Errorf("add dated message to memory: %w", err)

        }
 
        }
 

-       err = m.load()
+       err = m.save()

        if err != nil {
        if err != nil {

-               return nil, errors.Join(fmt.Errorf("load view: %w", err), m.Close())
+               return Message{}, fmt.Errorf("save dated message view: %w", err)

        }
 
        }
 

-       err = m.restoreQueue()
-       if err != nil {
-               return nil, errors.Join(fmt.Errorf("restore build queue: %w", err), m.Close())
+       m.queue.Retry()
+       m.dispatch()
+
+       return message, nil
+}
+
+// children reads the two children of the node key.
+func (m *Memory) children(key NodeKey) (Node, Node, error) {
+       var children [2]Node
+
+       for n := range children {
+               child, built, err := m.tree.Node(key.level-1, 2*key.index+n)
+               if err != nil {
+                       return Node{}, Node{}, err
+               }
+
+               if !built {
+                       return Node{}, Node{}, fmt.Errorf("node (%d, %d) is not built", key.level-1, 2*key.index+n)
+               }
+
+               children[n] = child

        }
 
        }
 

-       err = m.catchUp()
-       if err != nil {
-               return nil, errors.Join(err, m.Close())
+       return children[0], children[1], nil
+}
+
+// Wait returns when no build runs. The failed builds wait for the next message.
+func (m *Memory) Wait(ctx context.Context) error {
+       for {
+               m.mutex.Lock()
+
+               running := m.queue.Running()
+               changed := m.changed
+               m.mutex.Unlock()
+
+               if running == 0 {
+                       return nil
+               }
+
+               select {
+               case <-changed:
+               case <-ctx.Done():
+                       return ctx.Err()
+               }
+       }
+}
+
+// Settle returns when the chat view has no pending line, so that every message
+// so far is summarized. A pending line with no build that runs belongs to a
+// failed build, which waits for the next message, so Settle returns
+// errMemoryUnsettled in place of a wait that never ends.
+func (m *Memory) Settle(ctx context.Context) error {
+       for {
+               m.mutex.Lock()
+
+               pending := m.chat.Pending()
+               running := m.queue.Running()
+               changed := m.changed
+               m.mutex.Unlock()
+
+               if !pending {
+                       return nil
+               }
+
+               if running == 0 {
+                       return errMemoryUnsettled
+               }
+
+               select {
+               case <-changed:
+               case <-ctx.Done():
+                       return ctx.Err()
+               }

        }
        }

+}
+
+// Flush returns when every write before the call is durable.
+func (m *Memory) Flush(ctx context.Context) error {
+       return m.syncer.Flush(ctx)
+}

 
 

+// ViewLines returns the lines of the chat view, each with its newline, without
+// the leaf lines of the messages in skip.
+func (m *Memory) ViewLines(skip map[int]bool) []string {

        m.mutex.Lock()
        m.mutex.Lock()

-       m.syncer.Written()
-       m.dispatch()
-       m.mutex.Unlock()
+       defer m.mutex.Unlock()

 
 

-       return m, nil
+       return m.chat.LinesWithout(skip)
+}
+
+// Len returns the number of messages in the log.
+func (m *Memory) Len() int {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       return m.log.Len()
+}
+
+// Message reads the message with the given ID.
+func (m *Memory) Message(id int) (Message, error) {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       return m.log.Message(id)
+}
+
+// Node reads the node (l, i) if it is built.
+func (m *Memory) Node(level, index int) (Node, bool, error) {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       return m.tree.Node(level, index)

 }
 
 // load reads the saved views.
 func (m *Memory) load() error {
        data, err := os.ReadFile(m.viewPath())
        if errors.Is(err, os.ErrNotExist) && m.log.Len() == 0 {
 }
 
 // load reads the saved views.
 func (m *Memory) load() error {
        data, err := os.ReadFile(m.viewPath())
        if errors.Is(err, os.ErrNotExist) && m.log.Len() == 0 {

-               m.chat = newView(chatHigh, chatLow)
-               m.cview = newView(compactionHigh, compactionLow)
+               m.chat = newView(viewChatHigh, viewChatLow)
+               m.cview = newView(viewCompactionHigh, viewCompactionLow)

 
                return nil
        }
 
        if errors.Is(err, os.ErrNotExist) {
 
                return nil
        }
 
        if errors.Is(err, os.ErrNotExist) {

-               return errNoView
+               return errMemoryNoView

        }
 
        if err != nil {
                return fmt.Errorf("read view: %w", err)
        }
 
        }
 
        if err != nil {
                return fmt.Errorf("read view: %w", err)
        }
 

-       var file viewFile
+       var file MemoryViewFile
+

        err = json.Unmarshal(data, &file)
        if err != nil {
                return fmt.Errorf("decode view: %w", err)
        }
 
        err = json.Unmarshal(data, &file)
        if err != nil {
                return fmt.Errorf("decode view: %w", err)
        }
 

-       m.chat, err = restoreView(file.Chat, chatHigh, chatLow, m.tree)
+       m.chat, err = restoreView(file.Chat, viewChatHigh, viewChatLow, m.tree)

        if err != nil {
                return fmt.Errorf("chat view: %w", err)
        }
 
        if err != nil {
                return fmt.Errorf("chat view: %w", err)
        }
 

-       m.cview, err = restoreView(file.Compaction, compactionHigh, compactionLow, m.tree)
+       m.cview, err = restoreView(file.Compaction, viewCompactionHigh, viewCompactionLow, m.tree)

        if err != nil {
                return fmt.Errorf("compaction view: %w", err)
        }
        if err != nil {
                return fmt.Errorf("compaction view: %w", err)
        }


@@ -188,6 +347,7 @@ func (m *Memory) restoreQueue() error {
                leaf, free := freeLeaf(message)
                if !free {
                        m.queue.AddLeaf(id)
                leaf, free := freeLeaf(message)
                if !free {
                        m.queue.AddLeaf(id)

+

                        continue
                }
 
                        continue
                }
 


@@ -238,54 +398,27 @@ func (m *Memory) catchUp() error {
        return m.save()
 }
 
        return m.save()
 }
 

-// Close stops the builds, waits for them, makes the writes durable, closes the
-// files of the chat, and releases its lock.
-func (m *Memory) Close() error {
-       m.cancel()
-       m.workers.Wait()
-
-       m.mutex.Lock()
-       defer m.mutex.Unlock()
-
-       var err error
-       if m.syncer != nil {
-               err = m.syncer.Close()
-       }
-
-       if m.tree != nil {
-               err = errors.Join(err, m.tree.Close())
-       }
-
-       return errors.Join(err, m.log.Close())
-}
-
-// Append logs a new message, adds it to the tree and the views, and starts the
-// builds that are ready, also the failed ones.
-func (m *Memory) Append(kind, text string) (Message, error) {
-       m.mutex.Lock()
-       defer m.mutex.Unlock()
+// dispatch starts the builds that are ready, up to the limit. A build whose
+// input cannot be read fails and waits for the next message.
+func (m *Memory) dispatch() {
+       for m.ctx.Err() == nil {
+               key, ready := m.queue.Next()
+               if !ready {
+                       return
+               }

 
 

-       message, err := m.log.Append(kind, text)
-       if err != nil {
-               return Message{}, err
-       }
+               task, err := m.task(key)
+               if err != nil {
+                       m.failed(key, fmt.Errorf("read its input: %w", err))
+                       m.queue.Fail(key)

 
 

-       defer m.syncer.Written()
+                       continue
+               }

 
 

-       err = m.addMessage(message)
-       if err != nil {
-               return Message{}, err
-       }
+               m.workers.Add(1)

 
 

-       err = m.save()
-       if err != nil {
-               return Message{}, err
+               go m.run(key, task)

        }
        }

-
-       m.queue.Retry()
-       m.dispatch()
-
-       return message, nil

 }
 
 // addMessage builds the leaf of message when it needs no model call, or else
 }
 
 // addMessage builds the leaf of message when it needs no model call, or else


@@ -327,6 +460,28 @@ func (m *Memory) addMessage(message Message) error {
        return nil
 }
 
        return nil
 }
 

+// save writes the views to view.json.
+func (m *Memory) save() error {
+       data, err := json.Marshal(MemoryViewFile{
+               Chat:       m.chat.State(),
+               Compaction: m.cview.State(),
+       })
+       if err != nil {
+               return fmt.Errorf("encode view: %w", err)
+       }
+
+       err = writeFileAtomic(m.viewPath(), append(data, '\n'))
+       if err != nil {
+               return fmt.Errorf("save view: %w", err)
+       }
+
+       return nil
+}
+
+func (m *Memory) viewPath() string {
+       return filepath.Join(m.root, "view.json")
+}
+

 // build adds node to the tree, keeps it in the views when it is a pending line,
 // and settles its parent.
 func (m *Memory) build(node Node) error {
 // build adds node to the tree, keeps it in the views when it is a pending line,
 // and settles its parent.
 func (m *Memory) build(node Node) error {


@@ -338,15 +493,15 @@ func (m *Memory) build(node Node) error {
        m.chat.Refresh(node)
        m.cview.Refresh(node)
 
        m.chat.Refresh(node)
        m.cview.Refresh(node)
 

-       return m.settle(nodeKey{node.Level, node.Index})
+       return m.settle(NodeKey{node.Level, node.Index})

 }
 
 // settle looks at the parent of the built node key when both children are
 // built. It builds each parent that needs no model call, up the tree, and adds
 // the first other parent to the queue.
 }
 
 // settle looks at the parent of the built node key when both children are
 // built. It builds each parent that needs no model call, up the tree, and adds
 // the first other parent to the queue.

-func (m *Memory) settle(key nodeKey) error {
+func (m *Memory) settle(key NodeKey) error {

        for {
        for {

-               parent := nodeKey{key.level + 1, key.index / 2}
+               parent := NodeKey{key.level + 1, key.index / 2}

                ready, err := m.ready(parent)
                if err != nil || !ready {
                        return err
                ready, err := m.ready(parent)
                if err != nil || !ready {
                        return err


@@ -360,6 +515,7 @@ func (m *Memory) settle(key nodeKey) error {
                node, free := freeMerge(left, right)
                if !free {
                        m.queue.AddMerge(parent)
                node, free := freeMerge(left, right)
                if !free {
                        m.queue.AddMerge(parent)

+

                        return nil
                }
 
                        return nil
                }
 


@@ -372,62 +528,9 @@ func (m *Memory) settle(key nodeKey) error {
        }
 }
 
        }
 }
 

-// ready tells if both children of the node key are built and the node is not.
-func (m *Memory) ready(key nodeKey) (bool, error) {
-       for _, index := range []int{2 * key.index, 2*key.index + 1} {
-               built, err := m.tree.Built(key.level-1, index)
-               if err != nil || !built {
-                       return false, err
-               }
-       }
-
-       built, err := m.tree.Built(key.level, key.index)
-
-       return !built, err
-}
-
-// children reads the two children of the node key.
-func (m *Memory) children(key nodeKey) (Node, Node, error) {
-       var children [2]Node
-       for n := range children {
-               child, built, err := m.tree.Node(key.level-1, 2*key.index+n)
-               if err != nil {
-                       return Node{}, Node{}, err
-               }
-
-               if !built {
-                       return Node{}, Node{}, fmt.Errorf("node (%d, %d) is not built", key.level-1, 2*key.index+n)
-               }
-
-               children[n] = child
-       }
-
-       return children[0], children[1], nil
-}
-
-// dispatch starts the builds that are ready, up to the limit. A build whose
-// input cannot be read fails and waits for the next message.
-func (m *Memory) dispatch() {
-       for m.ctx.Err() == nil {
-               key, ready := m.queue.Next()
-               if !ready {
-                       return
-               }
-
-               task, err := m.task(key)
-               if err != nil {
-                       m.queue.Fail(key)
-                       continue
-               }
-
-               m.workers.Add(1)
-               go m.run(key, task)
-       }
-}
-

 // task returns the build task of the node key, with its input read from the log
 // or the tree.
 // task returns the build task of the node key, with its input read from the log
 // or the tree.

-func (m *Memory) task(key nodeKey) (Task, error) {
+func (m *Memory) task(key NodeKey) (Task, error) {

        task := Task{
                Level:   key.level,
                Index:   key.index,
        task := Task{
                Level:   key.level,
                Index:   key.index,


@@ -459,7 +562,7 @@ func (m *Memory) task(key nodeKey) (Task, error) {
 
 // run builds one node with the summarizer. A failed build stays in the queue
 // until the next message.
 
 // run builds one node with the summarizer. A failed build stays in the queue
 // until the next message.

-func (m *Memory) run(key nodeKey, task Task) {
+func (m *Memory) run(key NodeKey, task Task) {

        defer m.workers.Done()
 
        text, err := m.summarizer.Summarize(m.ctx, task)
        defer m.workers.Done()
 
        text, err := m.summarizer.Summarize(m.ctx, task)


@@ -477,6 +580,10 @@ func (m *Memory) run(key nodeKey, task Task) {
                m.syncer.Written()
        }
 
                m.syncer.Written()
        }
 

+       if err != nil && m.ctx.Err() == nil {
+               m.failed(key, err)
+       }
+

        if err != nil {
                m.queue.Fail(key)
        } else {
        if err != nil {
                m.queue.Fail(key)
        } else {


@@ -484,55 +591,37 @@ func (m *Memory) run(key nodeKey, task Task) {
        }
 
        close(m.changed)
        }
 
        close(m.changed)

+

        m.changed = make(chan struct{})
        m.dispatch()
 }
 
        m.changed = make(chan struct{})
        m.dispatch()
 }
 

-// Wait returns when no build runs. The failed builds wait for the next message.
-func (m *Memory) Wait(ctx context.Context) error {
-       for {
-               m.mutex.Lock()
-               running := m.queue.Running()
-               changed := m.changed
-               m.mutex.Unlock()
-
-               if running == 0 {
-                       return nil
-               }
+// failed logs the failed build of the node key with its cause err.
+func (m *Memory) failed(key NodeKey, err error) {
+       m.logger.Printf("summary failed, retry at next message: node (%d, %d): %v", key.level, key.index, err)
+}

 
 

-               select {
-               case <-changed:
-               case <-ctx.Done():
-                       return ctx.Err()
+// ready tells if both children of the node key are built and the node is not.
+func (m *Memory) ready(key NodeKey) (bool, error) {
+       for _, index := range []int{2 * key.index, 2*key.index + 1} {
+               built, err := m.tree.Built(key.level-1, index)
+               if err != nil || !built {
+                       return false, err

                }
        }
                }
        }

-}

 
 

-// Flush returns when every write before the call is durable.
-func (m *Memory) Flush(ctx context.Context) error {
-       return m.syncer.Flush(ctx)
-}
+       built, err := m.tree.Built(key.level, key.index)

 
 

-// save writes the views to view.json.
-func (m *Memory) save() error {
-       data, err := json.Marshal(viewFile{
-               Chat:       m.chat.State(),
-               Compaction: m.cview.State(),
-       })
-       if err != nil {
-               return fmt.Errorf("encode view: %w", err)
-       }
+       return !built, err
+}

 
 

-       err = writeFileAtomic(m.viewPath(), append(data, '\n'))
-       if err != nil {
-               return fmt.Errorf("save view: %w", err)
+func (m *Memory) context(level, index int) string {
+       end := index
+       if level > 0 {
+               end = nodeEnd(level, index)

        }
 
        }
 

-       return nil
-}
-
-func (m *Memory) viewPath() string {
-       return filepath.Join(m.root, "view.json")
+       return m.cview.Context(end)

 }
 
 // View returns the chat view as the model reads it.
 }
 
 // View returns the chat view as the model reads it.


@@ -553,11 +642,92 @@ func (m *Memory) Context(level, index int) string {
        return m.context(level, index)
 }
 
        return m.context(level, index)
 }
 

-func (m *Memory) context(level, index int) string {
-       end := index
-       if level > 0 {
-               end = nodeEnd(level, index)
+// rebuildComplete checks the whole tree, not only the visible view. A compactor
+// can fail without an HTTP error, for example with an empty line. Such a failed
+// merge can be absent from the view and must prevent a swap.
+func (m *Memory) rebuildComplete() error {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       if len(m.queue.leaves) != 0 || len(m.queue.queued) != 0 {
+               return errors.New("rebuild failed: summary tree has unfinished nodes")

        }
 
        }
 

-       return m.cview.Context(end)
+       return nil
+}
+
+// buildModelLines returns the sizes of the nodes that the model wrote, in tree
+// order. A node that fits its source with no model call is not one of them.
+func (m *Memory) buildModelLines() ([]int, error) {
+       m.mutex.Lock()
+       defer m.mutex.Unlock()
+
+       keys, err := m.tree.Keys()
+       if err != nil {
+               return nil, fmt.Errorf("list built nodes: %w", err)
+       }
+
+       var sizes []int
+
+       for _, key := range keys {
+               var node Node
+
+               node, _, err = m.tree.Node(key.level, key.index)
+               if err != nil {
+                       return nil, fmt.Errorf("read built node: %w", err)
+               }
+
+               var model bool
+
+               model, err = m.buildBuiltByModel(key)
+               if err != nil {
+                       return nil, fmt.Errorf("check model source: %w", err)
+               }
+
+               if model {
+                       sizes = append(sizes, node.Size)
+               }
+       }
+
+       return sizes, nil
+}
+
+// buildBuiltByModel tells if the node key needed a model call: a leaf whose
+// source is over nodeBytes, or a merge whose children do not fit in one node.
+func (m *Memory) buildBuiltByModel(key NodeKey) (bool, error) {
+       if key.level == 0 {
+               message, err := m.log.Message(key.index)
+               if err != nil {
+                       return false, fmt.Errorf("read leaf source: %w", err)
+               }
+
+               _, free := freeLeaf(message)
+
+               return !free, nil
+       }
+
+       left, right, err := m.children(key)
+       if err != nil {
+               return false, fmt.Errorf("read merge sources: %w", err)
+       }
+
+       _, free := freeMerge(left, right)
+
+       return !free, nil
+}
+
+// Task is the build of the node (Level, Index). Context is the compaction view
+// for the build. Input holds the source "kind: text" of a leaf, or the two
+// child lines of a merge with their newlines as spaces.
+type Task struct {
+       Level   int
+       Index   int
+       Context string
+       Input   []string
+}
+
+// MemoryViewFile is the content of view.json.
+type MemoryViewFile struct {
+       Chat       ViewState `json:"chat"`
+       Compaction ViewState `json:"compaction"`

 }
 }