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.\" Copyright (c) 2019 Ted Unangst
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.Dd $Mdocdate$
.Dt HFCS 1
.Os
.Sh NAME
.Nm hfcs
.Nd honk filtering and censorship system
.Sh DESCRIPTION
The honk filtering and censorship system,
.Nm hfcs ,
controls what messages are seen and how they are presented to the user.
Filter rules are based on a series of matches and actions.
It is accessed via the
.Pa filters
menu item.
.Pp
Each filter has an optional
.Ar name
and
.Ar notes
for user defined purposes.
.Pp
The following match types are possible.
All nonempty criteria must match.
.Bl -tag -width include-audience
.It Ar who
Match an actor or domain name.
Matches against
.Fa Ar actor
property.
.It Ar include audience
Previous match is applied against
.Fa to
and
.Fa cc
fields as well.
.It Ar text
Regular expression match against the post
.Fa content .
The special value of "." will match any post with a summary only.
.It Ar is announce
Is announced (shared).
.It Ar announce of
Limit prevous match to only specified actor or domain name.
.El
.Pp
The following actions may be applied.
Multiple actions may be applied, but some are subsumed by others.
.Bl -tag -width tenletters
.It Ar reject
Reject this message entirely.
.It Ar skip media
Don't include images or attachments.
.It Ar hide
Remove this message from most feeds.
.It Ar collapse
Show only a short summary with click to view content.
.It Ar rewrite
Rewrite message content, using
.Ar replace
replacement text.
.El
.Pp
The
.Ar text
and
.Ar rewrite
fields are case insensitive word anchored regular expressions.
Specifically, an argument
.Ql re
will be automatically rewritten as
.Ql \\\b(?i:re)\\\b .
The
.Ar replace
text may refer to submatches using $1, etc.
.Pp
A post marked sensitive that does not otherwise contain a summary will
have an invisible summary of
.Dq unspecified horror
that can be matched against and will appear if the post is collapsed.
.Pp
An optional expiration may be specified as a duration.
XdYhZm for X days, Y hours, and Z minutes.
.Sh SEE ALSO
.Xr honk 1
.Sh CAVEATS
Not seeing is not erasing.