parser/gotest: Create output collector that preserves the line order

parser/gotest/internal/collector/collector.go

@@ -0,0 +1,81 @@
+// Package collector collects output lines grouped by id and provides ways to
+// retrieve and merge output ordered by the time each line was added.
+package collector
+
+import (
+	"sort"
+	"time"
+)
+
+// line is a single line of output captured at some point in time.
+type line struct {
+	Timestamp time.Time
+	Text      string
+}
+
+// Output stores output lines grouped by id. Output can be retrieved for one or
+// more ids and output of different ids can be merged together, all while
+// preserving their original order based on the time it was collected.
+type Output struct {
+	m map[int][]line
+}
+
+// New returns a new output collector.
+func New() *Output {
+	return &Output{m: make(map[int][]line)}
+}
+
+// Clear deletes all output for the given id.
+func (o *Output) Clear(id int) {
+	o.m[id] = nil
+}
+
+// Append appends the given line of text to the output of the specified id.
+func (o *Output) Append(id int, text string) {
+	o.m[id] = append(o.m[id], line{time.Now(), text})
+}
+
+// Contains returns true if any output lines were collected for the given id.
+func (o *Output) Contains(id int) bool {
+	return len(o.m[id]) > 0
+}
+
+// Get returns the output lines for the given id.
+func (o *Output) Get(id int) []string {
+	var lines []string
+	for _, line := range o.m[id] {
+		lines = append(lines, line.Text)
+	}
+	return lines
+}
+
+// GetAll returns the output lines for all ids sorted by the collection
+// timestamp of each line of output.
+func (o *Output) GetAll(ids ...int) []string {
+	var output []line
+	for _, id := range ids {
+		output = append(output, o.m[id]...)
+	}
+	sort.Slice(output, func(i, j int) bool {
+		return output[i].Timestamp.Before(output[j].Timestamp)
+	})
+	var lines []string
+	for _, line := range output {
+		lines = append(lines, line.Text)
+	}
+	return lines
+}
+
+// Merge merges the output lines from fromID into intoID, and sorts the output
+// by the collection timestamp of each line of output.
+func (o *Output) Merge(fromID, intoID int) {
+	var merged []line
+	for _, id := range []int{fromID, intoID} {
+		merged = append(merged, o.m[id]...)
+	}
+	sort.Slice(merged, func(i, j int) bool {
+		return merged[i].Timestamp.Before(merged[j].Timestamp)
+	})
+	o.m[intoID] = merged
+	delete(o.m, fromID)
+}