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|
package mailstuff
import (
"regexp"
"strings"
)
// https://www.jwz.org/doc/threading.html
// TODO: See ./jwz.md for RFC 5256 changes we might want to bring in.
// Definitions /////////////////////////////////////////////////////////////////
type jwzContainer struct {
Message *jwzMessage
Parent *jwzContainer
Children Set[*jwzContainer]
}
type jwzMessage struct {
Subject string
ID jwzID
References []jwzID
}
type jwzID = MessageID //string
func (ancestor *jwzContainer) IsAncestorOf(descendent *jwzContainer) bool {
if ancestor == descendent {
return true
}
for child := range ancestor.Children {
if child.IsAncestorOf(descendent) {
return true
}
}
return false
}
// The Algorithm ///////////////////////////////////////////////////////////////
var jwzSubjectRE = regexp.MustCompile(`^(?:\s*[Rr][Ee](?:\[[0-9]+\])?:)*`)
func jwzThreadMessages(msgs map[jwzID]*jwzMessage) Set[*jwzContainer] {
idTable := make(map[jwzID]*jwzContainer, len(msgs))
// 1. For each message
for _, msg := range msgs {
// A.
msgContainer := idTable[msg.ID]
if msgContainer != nil && msgContainer.Message == nil {
msgContainer.Message = msg
} else {
msgContainer = &jwzContainer{
Message: msg,
Children: make(Set[*jwzContainer]),
}
idTable[msg.ID] = msgContainer
}
// B.
for _, refID := range msg.References {
refContainer := idTable[refID]
if refContainer == nil {
refContainer = &jwzContainer{
Children: make(Set[*jwzContainer]),
}
idTable[refID] = refContainer
}
}
for i := 0; i+1 < len(msg.References); i++ {
parent := idTable[msg.References[i]]
child := idTable[msg.References[i+1]]
if child.Parent == nil && !parent.IsAncestorOf(child) && !child.IsAncestorOf(parent) {
parent.Children.Insert(child)
child.Parent = parent
}
}
// C.
if len(msg.References) == 0 {
if msgContainer.Parent != nil {
delete(msgContainer.Parent.Children, msgContainer)
}
msgContainer.Parent = nil
} else {
msgContainer.Parent = idTable[msg.References[len(msg.References)-1]]
msgContainer.Parent.Children.Insert(msgContainer)
}
}
// 2. Find the root Set
root := &jwzContainer{
Children: make(Set[*jwzContainer]),
}
for _, container := range idTable {
if container.Parent == nil {
container.Parent = root
root.Children.Insert(container)
}
}
// 3. Discard id_table
idTable = nil
// 4. Prune empty containers
var recurse func(*jwzContainer)
recurse = func(container *jwzContainer) {
// Recurse. This is a touch complicated because
// `recurse(child)` might insert into
// `container.Children`, and those insertions might
// not be emitted by the range loop
for visited := make(Set[*jwzContainer]); ; {
beforeSize := len(visited)
for child := range container.Children {
if visited.Has(child) {
continue
}
recurse(child)
visited.Insert(child)
}
if len(visited) == beforeSize {
break
}
}
if container.Parent == nil {
return
}
// Main.
if container.Message == nil {
if len(container.Children) == 0 { // A.
delete(container.Parent.Children, container)
} else { // B.
if len(container.Children) == 1 || container.Parent != root {
for child := range container.Children {
container.Parent.Children.Insert(child)
child.Parent = container.Parent
}
delete(container.Parent.Children, container)
}
}
}
}
recurse(root)
// 5. Group root Set by subject
// A.
subjectTable := make(map[string]*jwzContainer)
// B.
for this := range root.Children {
var subject string
if this.Message != nil {
subject = this.Message.Subject
} else {
subject = this.Children.PickOne().Message.Subject
}
prefix := jwzSubjectRE.FindString(subject)
subject = strings.TrimSpace(subject[len(prefix):])
if subject == "" {
continue
}
if other := subjectTable[subject]; other == nil {
subjectTable[subject] = this
} else if other.Message == nil {
subjectTable[subject] = this
} else if jwzSubjectRE.MatchString(other.Message.Subject) && prefix == "" {
subjectTable[subject] = this
}
}
// C.
for this := range root.Children {
var subject string
if this.Message != nil {
subject = this.Message.Subject
} else {
subject = this.Children.PickOne().Message.Subject
}
prefix := jwzSubjectRE.FindString(subject)
subject = strings.TrimSpace(subject[len(prefix):])
other := subjectTable[subject]
if other == nil || other == this {
continue
}
switch {
case this.Message == nil && other.Message == nil:
for child := range this.Children {
other.Children.Insert(child)
child.Parent = other
}
delete(root.Children, this)
case (this.Message == nil) != (other.Message == nil):
var empty, nonEmpty *jwzContainer
if this.Message == nil {
empty = this
nonEmpty = other
} else {
empty = other
nonEmpty = this
}
empty.Children.Insert(nonEmpty)
nonEmpty.Parent = empty
case other.Message != nil && !jwzSubjectRE.MatchString(other.Message.Subject) && prefix != "":
other.Children.Insert(this)
this.Parent = other
// skip the reverse of the above case--it happened implicitly
default:
newParent := &jwzContainer{
Children: make(Set[*jwzContainer], 2),
}
newParent.Children.Insert(this)
this.Parent = newParent
newParent.Children.Insert(other)
other.Parent = newParent
subjectTable[subject] = newParent
root.Children.Insert(newParent)
delete(root.Children, this)
delete(root.Children, other)
}
}
// 6. Now you're done threading
for child := range root.Children {
child.Parent = nil
}
return root.Children
}
|
