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// Package filter evaluates deterministic, local-only Usenet filters.
package filter
import (
"fmt"
"path"
"regexp"
"strings"
"time"
)
type Field string
const (
FieldAny Field = "any"
FieldFrom Field = "from"
FieldSubject Field = "subject"
FieldNewsgroups Field = "newsgroups"
FieldMessageID Field = "message-id"
FieldReferences Field = "references"
FieldDate Field = "date"
FieldBody Field = "body"
FieldHeader Field = "header"
FieldVFaceHash Field = "vface-hash"
FieldRead Field = "read"
)
type Operator string
const (
OperatorContains Operator = "contains"
OperatorExact Operator = "exact"
OperatorRegexp Operator = "regexp"
OperatorGlob Operator = "glob"
)
type Action string
const (
ActionKeep Action = "keep"
ActionHide Action = "hide"
ActionMarkRead Action = "mark-read"
ActionHighlight Action = "highlight"
ActionTag Action = "tag"
ActionMuteThread Action = "mute-thread"
)
type Rule struct {
ID string `json:"id"`
Enabled bool `json:"enabled"`
Field Field `json:"field"`
Header string `json:"header,omitempty"`
Operator Operator `json:"operator"`
Pattern string `json:"pattern"`
Action Action `json:"action"`
Tag string `json:"tag,omitempty"`
Reason string `json:"reason,omitempty"`
}
type Article struct {
From string
Subject string
Newsgroups string
MessageID string
References string
Date string
Body string
Read bool
Headers map[string]string
}
type Result struct {
Hidden bool
MarkRead bool
Highlight bool
MuteThread bool
Tags []string
MatchedRules []string
}
type InvalidRuleError struct{ Message string }
func (e *InvalidRuleError) Error() string { return e.Message }
func Evaluate(article Article, rules []Rule) (Result, error) {
var result Result
for _, rule := range rules {
if !rule.Enabled {
continue
}
if err := validateRule(rule); err != nil {
return Result{}, err
}
values := fieldValues(article, rule)
matched, err := match(values, rule.Operator, rule.Pattern)
if err != nil {
return Result{}, fmt.Errorf("rule %q: %w", rule.ID, err)
}
if !matched {
continue
}
result.MatchedRules = append(result.MatchedRules, rule.ID)
switch rule.Action {
case ActionHide:
result.Hidden = true
case ActionMarkRead:
result.MarkRead = true
case ActionHighlight:
result.Highlight = true
case ActionTag:
if rule.Tag != "" && !contains(result.Tags, rule.Tag) {
result.Tags = append(result.Tags, rule.Tag)
}
case ActionMuteThread:
result.MuteThread = true
case ActionKeep:
default:
return Result{}, &InvalidRuleError{Message: fmt.Sprintf("rule %q has unsupported action %q", rule.ID, rule.Action)}
}
}
return result, nil
}
func validateRule(rule Rule) error {
if strings.TrimSpace(rule.Pattern) == "" {
return &InvalidRuleError{Message: fmt.Sprintf("rule %q has an empty pattern", rule.ID)}
}
switch rule.Field {
case FieldAny, FieldFrom, FieldSubject, FieldNewsgroups, FieldMessageID,
FieldReferences, FieldDate, FieldBody, FieldHeader, FieldVFaceHash, FieldRead:
default:
return &InvalidRuleError{Message: fmt.Sprintf("rule %q has unsupported field %q", rule.ID, rule.Field)}
}
if rule.Field == FieldHeader && strings.TrimSpace(rule.Header) == "" {
return &InvalidRuleError{Message: fmt.Sprintf("rule %q needs a header name", rule.ID)}
}
switch rule.Operator {
case OperatorContains, OperatorExact, OperatorRegexp, OperatorGlob:
default:
return &InvalidRuleError{Message: fmt.Sprintf("rule %q has unsupported operator %q", rule.ID, rule.Operator)}
}
switch rule.Action {
case ActionKeep, ActionHide, ActionMarkRead, ActionHighlight, ActionTag, ActionMuteThread:
default:
return &InvalidRuleError{Message: fmt.Sprintf("rule %q has unsupported action %q", rule.ID, rule.Action)}
}
return nil
}
func fieldValues(article Article, rule Rule) []string {
if rule.Field == FieldAny {
return []string{article.From, article.Subject, article.Newsgroups, article.MessageID, article.References, article.Date, article.Body, vfaceValue(article.Headers)}
}
if rule.Field == FieldHeader {
for key, value := range article.Headers {
if strings.EqualFold(key, rule.Header) {
return []string{value}
}
}
return nil
}
switch rule.Field {
case FieldFrom:
return []string{article.From}
case FieldSubject:
return []string{article.Subject}
case FieldNewsgroups:
return []string{article.Newsgroups}
case FieldMessageID:
return []string{article.MessageID}
case FieldReferences:
return []string{article.References}
case FieldDate:
return []string{article.Date}
case FieldBody:
return []string{article.Body}
case FieldVFaceHash:
return []string{vfaceValue(article.Headers)}
case FieldRead:
return []string{fmt.Sprintf("%t", article.Read)}
default:
return nil
}
}
func vfaceValue(headers map[string]string) string {
for _, key := range []string{"Identity-Hash", "X-VFace-Hash", "X-VFace-PNG-SHA256"} {
for header, value := range headers {
if strings.EqualFold(header, key) {
return value
}
}
}
return ""
}
func match(values []string, operator Operator, pattern string) (bool, error) {
for _, value := range values {
switch operator {
case OperatorContains:
if strings.Contains(strings.ToLower(value), strings.ToLower(pattern)) {
return true, nil
}
case OperatorExact:
if strings.EqualFold(strings.TrimSpace(value), strings.TrimSpace(pattern)) {
return true, nil
}
case OperatorRegexp:
re, err := regexp.Compile(pattern)
if err != nil {
return false, err
}
if re.MatchString(value) {
return true, nil
}
case OperatorGlob:
matched, err := path.Match(strings.ToLower(pattern), strings.ToLower(value))
if err != nil {
return false, err
}
if matched {
return true, nil
}
}
}
return false, nil
}
func contains(values []string, wanted string) bool {
for _, value := range values {
if value == wanted {
return true
}
}
return false
}
// ParseDate is kept here so callers can validate date filters without adding
// parser logic to the UI. It accepts the common RFC 5322 form and RFC3339.
func ParseDate(value string) (time.Time, error) {
if parsed, err := time.Parse(time.RFC1123Z, value); err == nil {
return parsed, nil
}
return time.Parse(time.RFC3339, value)
}
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