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// Package thread builds local Usenet conversation trees from article headers.
package thread
import (
"sort"
"strings"
"aegis/internal/nntp"
)
type Node struct {
Header nntp.ArticleHeader
Parent *Node
Children []*Node
}
func Build(headers []nntp.ArticleHeader) []*Node {
ordered := append([]nntp.ArticleHeader(nil), headers...)
sort.SliceStable(ordered, func(i, j int) bool {
if ordered[i].Number == ordered[j].Number {
return ordered[i].MessageID < ordered[j].MessageID
}
return ordered[i].Number < ordered[j].Number
})
nodes := make(map[string]*Node, len(ordered))
for _, header := range ordered {
node := &Node{Header: header}
if key := canonicalID(header.MessageID); key != "" {
nodes[key] = node
}
}
var roots []*Node
for _, node := range nodesInOrder(ordered, nodes) {
parentID := lastReference(node.Header.References)
parent := nodes[canonicalID(parentID)]
if parent == nil || parent == node {
roots = append(roots, node)
continue
}
node.Parent = parent
parent.Children = append(parent.Children, node)
}
for _, node := range nodesInOrder(ordered, nodes) {
sort.SliceStable(node.Children, func(i, j int) bool { return node.Children[i].Header.Number < node.Children[j].Header.Number })
}
return roots
}
func nodesInOrder(headers []nntp.ArticleHeader, nodes map[string]*Node) []*Node {
result := make([]*Node, 0, len(headers))
seen := make(map[*Node]struct{}, len(headers))
for _, header := range headers {
node := nodes[canonicalID(header.MessageID)]
if node == nil {
continue
}
if _, ok := seen[node]; ok {
continue
}
seen[node] = struct{}{}
result = append(result, node)
}
return result
}
func lastReference(value string) string {
parts := strings.Fields(value)
if len(parts) == 0 {
return ""
}
return parts[len(parts)-1]
}
func canonicalID(value string) string {
return strings.ToLower(strings.TrimSpace(value))
}
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