X-Git-Url: https://git.giacomolli.uk/onechat/blobdiff_plain/9f17bfb1173524553fff5301b0664267b430e6e3..442c68e1d384a7da0d9ab039704bf763a1c3ac35:/view.go

diff --git a/view.go b/view.go
index 158b59e..ddd97ed 100644
--- a/view.go
+++ b/view.go
@@ -13,6 +13,11 @@ const (
 	chatHigh = 128000
 	chatLow  = 64000
 
+	// compactionHigh and compactionLow are the limits of the compaction
+	// view in bytes.
+	compactionHigh = 32000
+	compactionLow  = 16000
+
 	// pending is the text of a line that is not built yet.
 	pending = "(not summarized yet: zoom it)"
 )
@@ -96,23 +101,27 @@ func (v *View) State() viewState {
 }
 
 // Append adds the leaf of the next message as a line and merges when the view
-// is too large.
-func (v *View) Append(tree nodeReader) {
+// 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})
 	v.end++
-	v.fit(tree)
+
+	return v.fit(tree)
 }
 
-func (v *View) fit(tree nodeReader) {
+// 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)
 	if size > v.high {
 		v.merging = true
 	}
 
+	merged := false
 	for v.merging && size > v.low {
 		best := v.mostDue(tree)
 		if best < 0 {
-			return
+			return merged
 		}
 
 		left, right := v.lines[best], v.lines[best+1]
@@ -120,9 +129,42 @@ func (v *View) fit(tree nodeReader) {
 		size += lineSize(tree, parent) - lineSize(tree, left) - lineSize(tree, right)
 		v.lines[best] = parent
 		v.lines = append(v.lines[:best+1], v.lines[best+2:]...)
+		merged = true
 	}
 
 	v.merging = false
+
+	return merged
+}
+
+// Coarsen takes each merge of other, a view of the same messages, and then
+// merges in one batch until the size is at most low. Each line of the result is
+// 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) {
+	lines := make([]nodeKey, 0, len(v.lines))
+	mine, theirs := 0, 0
+	for start := 0; start < v.end; {
+		line := v.lines[mine]
+		if other.lines[theirs].level > line.level {
+			line = other.lines[theirs]
+		}
+
+		lines = append(lines, line)
+		start = nodeEnd(line.level, line.index)
+		for mine < len(v.lines) && v.lines[mine].index<<v.lines[mine].level < start {
+			mine++
+		}
+
+		for theirs < len(other.lines) && other.lines[theirs].index<<other.lines[theirs].level < start {
+			theirs++
+		}
+	}
+
+	v.lines = lines
+	v.merging = true
+	v.fit(tree)
 }
 
 // mostDue returns the position of the left line of the most due sibling pair
@@ -176,6 +218,26 @@ func (v *View) Render(tree nodeReader) string {
 	return text.String()
 }
 
+// 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 {
+	var text strings.Builder
+	text.WriteString("<chat>\n")
+	for _, line := range v.lines {
+		_, built := tree.Node(line.level, line.index)
+		if !built || nodeEnd(line.level, line.index) > end {
+			break
+		}
+
+		renderLine(&text, tree, 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)