X-Git-Url: https://git.giacomolli.uk/onechat/blobdiff_plain/e5343bd4c3ec69192e92f4be339b855eef36b6ec..4b9b22619008f0829b7f5a8685e7b1d2a9aeb6bb:/view.go?ds=sidebyside

diff --git a/view.go b/view.go
index ddd97ed..70182d0 100644
--- a/view.go
+++ b/view.go
@@ -24,7 +24,8 @@ const (
 
 // nodeReader gives the built nodes of a tree.
 type nodeReader interface {
-	Node(level, index int) (Node, bool)
+	Built(level, index int) (bool, error)
+	Node(level, index int) (Node, bool, error)
 }
 
 // View is a list of tree nodes that covers messages 0 to end-1 without a gap,
@@ -33,18 +34,20 @@ type nodeReader interface {
 // the size is at most low. A batch merges only pairs whose parent is built. If
 // the batch cannot get to low, it continues at each new message until it does.
 //
-// The size of a line is the size of its node text, or the size of the pending
-// text when the node is not built.
+// The view keeps the nodes of its built lines in memory, so its size and its
+// text need no read of the tree. The size of a line is the size of its node
+// text, or the size of the pending text when the node is not built.
 //
 // For the sibling pair (l, i) and (l, i+1), due is (T - last) / 2^l, with T the
 // number of messages and last the ID of the last message of the pair. That is
 // how long ago the pair ended, measured in its own line size. With a budget of
-// the length of Taelin's rollback push list, this order makes the same merges
-// as the push. The oldest pair wins a tie.
+// the length of the rollback push list of the reference design, this order
+// makes the same merges as the push. The oldest pair wins a tie.
 type View struct {
 	high    int
 	low     int
 	lines   []nodeKey
+	nodes   map[nodeKey]Node
 	end     int
 	merging bool
 }
@@ -58,8 +61,9 @@ type viewState struct {
 // newView returns an empty view with the limits high and low.
 func newView(high, low int) *View {
 	return &View{
-		high: high,
-		low:  low,
+		high:  high,
+		low:   low,
+		nodes: make(map[nodeKey]Node),
 	}
 }
 
@@ -74,7 +78,11 @@ func restoreView(state viewState, high, low int, tree nodeReader) (*View, error)
 			return nil, fmt.Errorf("view line (%d, %d) does not start at message %d", line.level, line.index, v.end)
 		}
 
-		_, built := tree.Node(line.level, line.index)
+		built, err := v.load(tree, line)
+		if err != nil {
+			return nil, err
+		}
+
 		if line.level > 0 && !built {
 			return nil, fmt.Errorf("view line (%d, %d) is not built", line.level, line.index)
 		}
@@ -86,6 +94,18 @@ func restoreView(state viewState, high, low int, tree nodeReader) (*View, error)
 	return v, nil
 }
 
+// load keeps the node of line when it is built, and tells if it is.
+func (v *View) load(tree nodeReader, line nodeKey) (bool, error) {
+	node, built, err := tree.Node(line.level, line.index)
+	if err != nil || !built {
+		return false, err
+	}
+
+	v.nodes[line] = node
+
+	return true, nil
+}
+
 // State returns the saved form of the view.
 func (v *View) State() viewState {
 	state := viewState{
@@ -102,8 +122,14 @@ func (v *View) State() viewState {
 
 // Append adds the leaf of the next message as a line and merges when the view
 // is too large. It tells if a merge changed the view.
-func (v *View) Append(tree nodeReader) bool {
-	v.lines = append(v.lines, nodeKey{0, v.end})
+func (v *View) Append(tree nodeReader) (bool, error) {
+	line := nodeKey{0, v.end}
+	_, err := v.load(tree, line)
+	if err != nil {
+		return false, err
+	}
+
+	v.lines = append(v.lines, line)
 	v.end++
 
 	return v.fit(tree)
@@ -111,22 +137,29 @@ func (v *View) Append(tree nodeReader) bool {
 
 // fit merges the most due pairs while a batch runs, and tells if a merge
 // changed the view.
-func (v *View) fit(tree nodeReader) bool {
-	size := v.Size(tree)
+func (v *View) fit(tree nodeReader) (bool, error) {
+	size := v.Size()
 	if size > v.high {
 		v.merging = true
 	}
 
 	merged := false
 	for v.merging && size > v.low {
-		best := v.mostDue(tree)
-		if best < 0 {
-			return merged
+		best, err := v.mostDue(tree)
+		if err != nil || best < 0 {
+			return merged, err
 		}
 
 		left, right := v.lines[best], v.lines[best+1]
 		parent := nodeKey{left.level + 1, left.index / 2}
-		size += lineSize(tree, parent) - lineSize(tree, left) - lineSize(tree, right)
+		_, err = v.load(tree, parent)
+		if err != nil {
+			return merged, err
+		}
+
+		size += v.lineSize(parent) - v.lineSize(left) - v.lineSize(right)
+		delete(v.nodes, left)
+		delete(v.nodes, right)
 		v.lines[best] = parent
 		v.lines = append(v.lines[:best+1], v.lines[best+2:]...)
 		merged = true
@@ -134,7 +167,7 @@ func (v *View) fit(tree nodeReader) bool {
 
 	v.merging = false
 
-	return merged
+	return merged, nil
 }
 
 // Coarsen takes each merge of other, a view of the same messages, and then
@@ -142,16 +175,23 @@ func (v *View) fit(tree nodeReader) bool {
 // the coarser of the two lines that start at its first message. Dyadic ranges
 // either nest or do not overlap, so the result covers the messages without a
 // gap.
-func (v *View) Coarsen(other *View, tree nodeReader) {
+func (v *View) Coarsen(other *View, tree nodeReader) error {
 	lines := make([]nodeKey, 0, len(v.lines))
+	nodes := make(map[nodeKey]Node, len(v.nodes))
 	mine, theirs := 0, 0
 	for start := 0; start < v.end; {
 		line := v.lines[mine]
+		node, built := v.nodes[line]
 		if other.lines[theirs].level > line.level {
 			line = other.lines[theirs]
+			node, built = other.nodes[line]
 		}
 
 		lines = append(lines, line)
+		if built {
+			nodes[line] = node
+		}
+
 		start = nodeEnd(line.level, line.index)
 		for mine < len(v.lines) && v.lines[mine].index<<v.lines[mine].level < start {
 			mine++
@@ -163,13 +203,16 @@ func (v *View) Coarsen(other *View, tree nodeReader) {
 	}
 
 	v.lines = lines
+	v.nodes = nodes
 	v.merging = true
-	v.fit(tree)
+	_, err := v.fit(tree)
+
+	return err
 }
 
 // mostDue returns the position of the left line of the most due sibling pair
 // whose parent is built, or -1 when there is no such pair.
-func (v *View) mostDue(tree nodeReader) int {
+func (v *View) mostDue(tree nodeReader) (int, error) {
 	best := -1
 	bestDue := 0.0
 	for n := 0; n+1 < len(v.lines); n++ {
@@ -178,39 +221,69 @@ func (v *View) mostDue(tree nodeReader) int {
 			continue
 		}
 
-		_, built := tree.Node(left.level+1, left.index/2)
-		if !built {
+		last := nodeEnd(right.level, right.index) - 1
+		due := math.Ldexp(float64(v.end-last), -left.level)
+		if best >= 0 && due <= bestDue {
 			continue
 		}
 
-		last := nodeEnd(right.level, right.index) - 1
-		due := math.Ldexp(float64(v.end-last), -left.level)
-		if best < 0 || due > bestDue {
+		built, err := tree.Built(left.level+1, left.index/2)
+		if err != nil {
+			return -1, err
+		}
+
+		if built {
 			best = n
 			bestDue = due
 		}
 	}
 
-	return best
+	return best, nil
+}
+
+// Refresh keeps node when it is the node of a pending line.
+func (v *View) Refresh(node Node) {
+	key := nodeKey{node.Level, node.Index}
+	for n := len(v.lines) - 1; n >= 0; n-- {
+		line := v.lines[n]
+		if line == key {
+			v.nodes[key] = node
+			return
+		}
+
+		if line.index<<line.level <= key.index<<key.level {
+			return
+		}
+	}
 }
 
 // Size returns the sum of the line sizes.
-func (v *View) Size(tree nodeReader) int {
+func (v *View) Size() int {
 	size := 0
 	for _, line := range v.lines {
-		size += lineSize(tree, line)
+		size += v.lineSize(line)
 	}
 
 	return size
 }
 
+// lineSize returns the size of a view line.
+func (v *View) lineSize(line nodeKey) int {
+	node, built := v.nodes[line]
+	if !built {
+		return len(pending)
+	}
+
+	return node.Size
+}
+
 // Render returns the view as the model reads it: one line "id+n|text" for each
 // node inside <chat> tags, with the newlines of the text as spaces.
-func (v *View) Render(tree nodeReader) string {
+func (v *View) Render() string {
 	var text strings.Builder
 	text.WriteString("<chat>\n")
 	for _, line := range v.lines {
-		renderLine(&text, tree, line)
+		v.renderLine(&text, line)
 	}
 
 	text.WriteString("</chat>")
@@ -218,48 +291,38 @@ func (v *View) Render(tree nodeReader) string {
 	return text.String()
 }
 
+// renderLine writes one view line, "id+n|text", and a newline.
+func (v *View) renderLine(text *strings.Builder, line nodeKey) {
+	body := pending
+	node, built := v.nodes[line]
+	if built {
+		body = strings.ReplaceAll(node.Text, "\n", " ")
+	}
+
+	text.WriteString(strconv.Itoa(line.index << line.level))
+	text.WriteByte('+')
+	text.WriteString(strconv.Itoa(1 << line.level))
+	text.WriteByte('|')
+	text.WriteString(body)
+	text.WriteByte('\n')
+}
+
 // Context returns the lines of the view before message end as the model reads
 // them. It stops at the first line that is not built, so a compaction never
 // sees a pending mark or a part of a message.
-func (v *View) Context(tree nodeReader, end int) string {
+func (v *View) Context(end int) string {
 	var text strings.Builder
 	text.WriteString("<chat>\n")
 	for _, line := range v.lines {
-		_, built := tree.Node(line.level, line.index)
+		_, built := v.nodes[line]
 		if !built || nodeEnd(line.level, line.index) > end {
 			break
 		}
 
-		renderLine(&text, tree, line)
+		v.renderLine(&text, line)
 	}
 
 	text.WriteString("</chat>")
 
 	return text.String()
 }
-
-// lineSize returns the size of a view line.
-func lineSize(tree nodeReader, line nodeKey) int {
-	node, built := tree.Node(line.level, line.index)
-	if !built {
-		return len(pending)
-	}
-
-	return node.Size
-}
-
-// renderLine writes one view line, "id+n|text", and a newline.
-func renderLine(text *strings.Builder, tree nodeReader, line nodeKey) {
-	body := pending
-	node, built := tree.Node(line.level, line.index)
-	if built {
-		body = strings.ReplaceAll(node.Text, "\n", " ")
-	}
-
-	text.WriteString(strconv.Itoa(line.index << line.level))
-	text.WriteByte('+')
-	text.WriteString(strconv.Itoa(1 << line.level))
-	text.WriteByte('|')
-	text.WriteString(body)
-	text.WriteByte('\n')
-}