Explain The Below Stored Procedure

CREATE procedure r_routeGetCache1
@pLongest varchar(32),
@pLongestCls int,
@pDate datetime,
@pSrcInt varchar(7),
@pSrcIntGroup varchar(64),
@pSrcIntDom varchar(64),
@routeclass int=0 ,
@pCLI varchar(32)='',
@pOperatorGroup int = 0 ,
@isgrade int=0

as
begin
declare @pc varchar(2)
declare @dd int
declare @hh int
declare @mm int

set @pc=left(@pLongest,2)
set @dd=1+(@@datefirst+datepart(dw,@pDate)-2)%7
set @hh=(datepart(hh, @pDate)-0)
set @mm=datepart(mi, @pDate)
set nocount on

--- Azam
select top 1 @routeclass = routecls from r_interface
where [group] = @pSrcIntGroup
and state='I'

if @routeclass is null set @routeclass=0
--- End

--insert
CREATE TABLE #operator_selected (
[routecls] [int] NOT NULL ,
[oprId] [int] NOT NULL ,
[cls] [varchar] (1) NOT NULL ,
[pc] [varchar] (2) NOT NULL
)

insert into #operator_selected(routecls,oprid,cls,pc)
select x.routecls,x.oprid,x.cls,x.pc
from RoutingV3..r20_route_timecls x (nolock),
RoutingV3..r_TimeCls y with (nolock),
RoutingV3..r_interface tit with (nolock),
RoutingV3..r_timecode tco with (nolock),
RoutingV3..r_daycode dco with (nolock)
where x.routecls=0
and tit.id = x.oprid and tit.state = 'I'
and y.tintid =x.oprid and y.cls=x.cls
and y.dc=dco.id and y.tc=tco.id and y.sc=0
and @dd between dco.d1 and dco.d2
and ((24+@hh+isnull(tit.prefixcls,0))%24) * 100 + @mm between tco.h1
and tco.h2-1
and x.pc=@pc

CREATE TABLE #timecls_selected (
[routecls] [int] NOT NULL ,
[oprId] [int] NOT NULL ,
[pc] [varchar] (2) NOT NULL ,
[prefixcode] [varchar] (50) NOT NULL ,
cnt int,
clsA int,
clsP int,
clsO int,
clsW int,
[cls] [varchar] (1)
)

insert into
#timecls_selected(routecls,oprid,pc,prefixcode,cnt,clsA,clsP,clsO,clsW,cls)
select a.routecls, a.oprid, a.pc, max(a.prefixCode) prefixCode,
count(*) cnt,
sum(case when a.cls='A' then 1 else 0 end) clsA,
sum(case when a.cls='P' then 1 else 0 end) clsP,
sum(case when a.cls='O' then 1 else 0 end) clsO,
sum(case when a.cls='W' then 1 else 0 end) clsW, 'Z' cls
from RoutingV3..r20_route12 a(nolock), #operator_selected b
where a.routeCls=@routeclass --b.routeCls
and a.oprId=b.oprId and a.cls=b.cls
and a.pc=b.pc
and left(@pLongest,prefixLen)=a.prefixcode
--- Exclude Artificial
--and not (id<0 and parentId is not null and parentId>0)
group by a.routecls, a.oprid, a.pc

update #timecls_selected
set cls = (case when (clsW>0) and (cnt = clsW) then 'W'
when (clsO>0) and (cnt = clsO) then 'O'
when (clsP>0) and (cnt = clsP) then 'P'
when (clsA>0) and (cnt = clsA) then 'A'
else 'Z' end)

update #timecls_selected
set cls = (select max(a.cls) from RoutingV3..r20_route12 a (nolock)
where a.routecls=#timecls_selected.routecls
and a.oprid = #timecls_selected.oprId
and a.pc=#timecls_selected.pc
and a.prefixCode=#timecls_selected.prefixCode
and ((a.cls='A' and #timecls_selected.clsA<>0) or
(a.cls='P' and #timecls_selected.clsP<>0) or
(a.cls='O' and #timecls_selected.clsO<>0) or
(a.cls='W' and #timecls_selected.clsW<>0))
)
where cls = 'Z'

CREATE TABLE #route (
seqno int identity(10,10),
priority int,
[id] int,
isactive int,
reason int,
exception int,
exceptionCls int,
calcexception int,
ext int,
oprid int,
parentid int,
routecls int,
prefixcode varchar(50),
universe varchar(5),
domain varchar(5),
pdomain varchar(5),
[group] varchar(40),
interface varchar(40),
userinfo varchar(40),
hint varchar(100),
clsorg char(1),
cls char(1),
cost float,
flag int,
rating int,
access varchar(10),
redlist int ,quality float)


if @isgrade =0
begin
insert into #route(isactive,reason, exception, exceptionCls, calcexception,[id],parentid,routecls,oprid,prefixcode,clsorg,cls,cost,
priority,rating,flag,ext,quality)
select
case when x.oprid>0 then x.state
else case when quality=99 then 0 else x.state end
end isactive,
x.reason,
isnull(x.exception,0) exception,
--case when x.oprId>0 then isnull(x.exceptionCls,0) else (case when x.quality=99 then 0 else isnull(x.exceptionCls,0) end) end exceptionCls,
isnull(x.exceptionCls,0) exceptionCls,
case when (isnull(x.exception,0) = 0) then 0
when x.exception > 0 then cast((x.exception+0.5)*10 as int)
else case when x.Id>0 then cast((x.exception-0.5)*10 as int) else 0 end
end [calcException],
x.id, x.parentId, x.routeCls, x.oprId, x.prefixCode, x.clsOrg, x.cls,
x.cost, x.priority, rating, x.flag, x.ext,x.quality
from RoutingV3..r20_route12 x(nolock), #timecls_selected b
where x.routecls=b.routecls and x.oprid=b.oprid and x.pc=b.pc and
x.prefixcode=b.prefixcode and x.cls=b.cls
order by x.cost
end
else
begin
insert into #route(isactive,reason, exception, exceptionCls, calcexception,[id],parentid,routecls,oprid,prefixcode,clsorg,cls,cost,
priority,rating,flag,ext,quality)
select
case when x.oprid>0 then x.state
else case when quality=99 then 0 else x.state end
end isactive,
x.reason,
isnull(x.exception,0) exception,
--case when x.oprId>0 then isnull(x.exceptionCls,0) else (case when x.quality=99 then 0 else 10 end) end exceptionCls,
isnull(x.exceptionCls,0) exceptionCls,
case when (isnull(x.exception,0) = 0) then 0
when x.exception > 0 then cast((x.exception+0.5)*10 as int)
else case when x.Id>0 then cast((x.exception-0.5)*10 as int) else 0 end
end [calcException],
x.id, x.parentId, x.routeCls, x.oprId, x.prefixCode, x.clsOrg, x.cls,
x.cost, x.priority, rating, x.flag, x.ext,x.quality
from RoutingV3..r20_route12 x(nolock), #timecls_selected b
where x.routecls=b.routecls and x.oprid=b.oprid and x.pc=b.pc
and x.prefixcode=b.prefixcode and x.cls=b.cls
order by x.quality,x.cost
end

set nocount on
select top 5
'r20_route12' routeset,
x.seqno priority, x.id, x.isactive, x.reason, x.exception, x.exceptionCls, x.calcexception,
isnull(x.ext,0) ext,
x.routecls, x.prefixcode, y.universe, y.domain, y.pdomain,
y.[group], y.name interface, y.userinfo, y.hint, x.clsOrg, x.cls
timecls, x.cost, x.flag, x.rating,
'11111' access, 0 redlist,x.quality grade
into #topN
from #route x, RoutingV3..r_interface y with (nolock)
where x.isActive=1
and x.oprId=y.id
and @pLongest like x.prefixcode+'%'
and exceptionCls<>0
order by seqno+[calcException], x.cost

select
'r20_route12' routeset,
x.seqno priority, x.id, x.isactive, x.reason, x.exception, x.exceptionCls, x.calcexception,
isnull(x.ext,0) ext,
x.routecls, x.prefixcode, y.universe, y.domain, y.pdomain,
y.[group], y.name interface, y.userinfo, y.hint, x.clsOrg, x.cls
timecls, x.cost, x.flag, x.rating,
'11111' access, 0 redlist,x.quality grade
into #all
from #route x, RoutingV3..r_interface y with (nolock)
where x.oprId=y.id
and @pLongest like x.prefixcode+'%'
order by seqno+[calcException], x.cost

delete #all
from #topN a, #all b
where a.id = b.id


set nocount off

select * from #topN where isActive=1
union all
select * from #all where isActive=1
end