! Copyright (C) 2009 Doug Coleman.
! See https://factorcode.org/license.txt for BSD license.
USING: accessors arrays assocs calendar.parser combinators
combinators.short-circuit globs http.client kernel math.parser
namespaces present regexp regexp.combinators sequences splitting
splitting.monotonic unicode urls ;
IN: robots

! visit-time is GMT, request-rate is pages/second
! crawl-rate is seconds

SYMBOL: robot-identities
robot-identities [ { "FactorSpider" } ] initialize

TUPLE: robots site sitemap rules rules-quot ;

: <robots> ( site sitemap rules -- robots )
    \ robots new
        swap >>rules
        swap >>sitemap
        swap >>site ;

TUPLE: rules user-agents allows disallows
visit-time request-rate crawl-delay unknowns ;

<PRIVATE

: >robots.txt-url ( url -- url' )
    >url URL" robots.txt" derive-url ;

: get-robots.txt ( url -- robots.txt )
    >robots.txt-url http-get nip ;

: normalize-robots.txt ( string -- sitemaps seq )
    split-lines
    [ [ unicode:blank? ] trim ] map
    [ "#" head? ] reject harvest
    [ ":" split1 [ [ unicode:blank? ] trim ] bi@ [ >lower ] dip  ] { } map>assoc
    [ first "sitemap" = ] partition [ values ] dip
    [
        {
            [ [ first "user-agent" = ] both? ]
            [ nip first "user-agent" = not ]
        } 2||
    ] monotonic-split ;

: <rules> ( -- rules )
    rules new
        V{ } clone >>user-agents
        V{ } clone >>allows
        V{ } clone >>disallows
        H{ } clone >>unknowns ;

: add-user-agent ( rules agent -- rules ) over user-agents>> push ;
: add-allow ( rules allow -- rules ) >url over allows>> push ;
: add-disallow ( rules disallow -- rules ) >url over disallows>> push ;

: parse-robots.txt-line ( rules seq -- rules )
    first2 swap {
        { "user-agent" [ add-user-agent ] }
        { "allow" [ add-allow ] }
        { "disallow" [ add-disallow ] }
        { "crawl-delay" [ string>number >>crawl-delay ] }
        { "request-rate" [ string>number >>request-rate ] }
        {
            "visit-time" [ "-" split1 [ hhmm>duration ] bi@ 2array
            >>visit-time
        ] }
        [ pick unknowns>> push-at ]
    } case ;

: derive-urls ( url seq -- seq' )
    [ derive-url present ] with { } map-as ;

: robot-rules-quot ( robots -- quot )
    [
        [ site>> ] [ rules>> allows>> ] bi
        derive-urls [ <glob> ] map
        <or>
    ] [
        [ site>> ] [ rules>> disallows>> ] bi
        derive-urls [ <glob> ] map <and> <not>
    ] bi 2array <or> '[ _ matches? ] ;

: relevant-rules ( robots -- rules )
    [
        user-agents>> [
            robot-identities get [ swap glob-matches? ] with any?
        ] any?
    ] filter ;

PRIVATE>

: parse-robots.txt ( string -- sitemaps rules-seq )
    normalize-robots.txt [
        [ <rules> dup ] dip [ parse-robots.txt-line drop ] with each
    ] map ;

: url>robots ( url -- robots )
    >url dup get-robots.txt parse-robots.txt <robots> ;