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// Package sortthread implements SORT and THREAD for go-imap.
//
// SORT and THREAD are defined in RFC 5256.
package sortthread
import (
"fmt"
"regexp"
"strings"
"github.com/emersion/go-imap"
)
const SortCapability = "SORT"
var ThreadCapabilities = []string{"THREAD=ORDEREDSUBJECT", "THREAD=REF", "THREAD=REFERENCES"}
// ThreadAlgorithm is the algorithm used by the server to sort messages
type ThreadAlgorithm string
const (
OrderedSubject ThreadAlgorithm = "ORDEREDSUBJECT"
References = "REFERENCES"
)
func formatThreadAlgorithm(algorithm ThreadAlgorithm) imap.RawString {
return imap.RawString(algorithm)
}
// SortField is a field that can be used to sort messages.
type SortField string
const (
SortArrival SortField = "ARRIVAL"
SortCc = "CC"
SortDate = "DATE"
SortFrom = "FROM"
SortSize = "SIZE"
SortSubject = "SUBJECT"
SortTo = "TO"
)
// SortCriterion is a criterion that can be used to sort messages.
type SortCriterion struct {
Field SortField
Reverse bool
}
func formatSortCriteria(criteria []SortCriterion) interface{} {
fields := make([]interface{}, 0, len(criteria))
for _, c := range criteria {
if c.Reverse {
fields = append(fields, imap.RawString("REVERSE"))
}
fields = append(fields, imap.RawString(c.Field))
}
return fields
}
type Thread struct {
Id uint32
Children []*Thread
}
var (
tabsContinuation = regexp.MustCompile(`[\t\\]`)
repeatedSpaces = regexp.MustCompile("[ ]+")
// Includes regex for ABNF rules relevant to base subject
// Note that all ABNF strings are considered lowercase
// subj-fwd-hdr = "[fwd:"
// subj-fwd-trl = "]"
subjFwd = regexp.MustCompile(`(?i)^\[fwd:(.*?)\]$`)
// BLOBCHAR = %x01-5a / %x5c / %x5e-ff
// subj-blob = "[" *BLOBCHAR "]" *WSP
subjBlob = `\[\x01-\x5a\x5c\x5e-\xff]\]\s*`
subjBlobPrefix = regexp.MustCompile(fmt.Sprintf("^%s", subjBlob))
// subj-refwd = ("re" / ("fw" ["d"])) *WSP [subj-blob] ":"
subjReFwd = fmt.Sprintf(`(?:(?:re)|(?:fwd?))\s*(?:%s)?:`, subjBlob)
// subj-leader = (*subj-blob subj-refwd) / WSP
subjLeader = regexp.MustCompile(fmt.Sprintf(`(?i)^(?:(?:%s)*%s)`,
subjBlob, subjReFwd))
// subj-trailer = "(fwd)" / WSP
subjTrailer = regexp.MustCompile(`(?i)\(fwd\)$`)
)
// Steps 2-5 in RFC Section 2.1
func replaceArtifacts(subject string, isReplyFwd *bool) string {
// (2) Remove all trailing text of the subject that matches the
// subj-trailer ABNF; repeat until no more matches are possible.
for {
noTrail := strings.TrimSuffix(subject, " ")
if subjTrailer.MatchString(noTrail) {
noTrail = subjTrailer.ReplaceAllString(noTrail, "")
*isReplyFwd = true
}
if subject == noTrail {
break
}
subject = noTrail
}
return replacePrefix(subject, isReplyFwd)
}
// Steps 3-5 in RFC Section 2.1
func replacePrefix(subject string, isReplyFwd *bool) string {
// (5) Repeat (3) and (4) until no matches remain.
for {
// (3) Remove all prefix text of the subject that matches the subj-
// leader ABNF.
noLeader := strings.TrimPrefix(subject, " ")
if subjLeader.MatchString(noLeader) {
noLeader = subjLeader.ReplaceAllString(noLeader, "")
*isReplyFwd = true
}
// (4) If there is prefix text of the subject that matches the subj-
// blob ABNF, and removing that prefix leaves a non-empty subj-
// base, then remove the prefix text.
noBlob := subjBlobPrefix.ReplaceAllString(noLeader, "")
if noBlob == "" {
subject = noLeader
break
}
if noBlob == subject {
break
}
subject = noBlob
}
return subject
}
// GetBaseSubject returns the base subject of the given string according to
// Section 2.1. The returned string is suitable for comparison with other base
// subjects. The returned bool indicates whether the subject is a reply or a
// forward.
func GetBaseSubject(subject string) (string, bool) {
baseSubject := subject
isReplyFwd := false
// (1) Convert any RFC 2047 encoded-words in the subject to [UTF-8]
// as described in "Internationalization Considerations".
// Convert all tabs and continuations to space. Convert all
// multiple spaces to a single space.
baseSubject = tabsContinuation.ReplaceAllString(baseSubject, " ")
baseSubject = repeatedSpaces.ReplaceAllString(baseSubject, " ")
for {
// Steps 2-5
baseSubject = replaceArtifacts(baseSubject, &isReplyFwd)
// (6) If the resulting text begins with the subj-fwd-hdr ABNF and
// ends with the subj-fwd-trl ABNF, remove the subj-fwd-hdr and
// subj-fwd-trl and repeat from step (2).
submatches := subjFwd.FindStringSubmatch(baseSubject)
if len(submatches) == 0 {
break
} else if len(submatches) != 2 {
panic(fmt.Errorf("Regex undefined behavior on subject %s", baseSubject))
}
baseSubject = submatches[1]
isReplyFwd = true
}
return baseSubject, isReplyFwd
}
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