local lib=require("transforms")

local adjust=lib.internal.range_adjust
local view=lib.internal.table_view


function lib.sub(tbl,f,l)
checkArg(1,tbl,'table')
local r,s={},#tbl
f,l=adjust(f,l,s)
l=math.min(l,s)
for i=math.max(f,1),l do
r[#r+1]=tbl[i]
end
return r
end


function lib.partition(tbl,partitioner,dropEnds,f,l)
checkArg(1,tbl,'table')
checkArg(2,partitioner,'function','table')
checkArg(3,dropEnds,'boolean','nil')
if type(partitioner)=='table'then
return lib.partition(tbl,function(e,i,tbl)
return lib.first(tbl,partitioner,i)
end,dropEnds,f,l)
end
local s=#tbl
f,l=adjust(f,l,s)
local cut=view(tbl,f,l)
local result={}
local need=true
local exp=function()if need then result[#result+1]={}need=false end end
local i=f
while i<=l do
local e=cut[i]
local ds,de=partitioner(e,i,cut)

if ds==true then ds,de=i,i
elseif ds==false then ds,de=nil,nil end
if ds~=nil then
ds,de=adjust(ds,de,l)
ds=ds>=i and ds
end
if not ds then
exp()
table.insert(result[#result],e)
else
local sub=lib.sub(cut,i,not dropEnds and de or(ds-1))
if#sub>0 then
exp()
result[#result+math.min(#result[#result],1)]=sub
end

local ensured=math.max(math.max(de or ds,ds),i)
if de and ds and de<ds and ensured==i then
if#result==0 then result[1]={}end
table.insert(result[#result],e)
end
i=ensured
need=true
end
i=i+1
end

return result
end


function lib.foreach(tbl,c,f,l)
checkArg(1,tbl,'table')
checkArg(2,c,'function','string')
local ck=c
c=type(c)=="string"and function(e)return e[ck]end or c
local s=#tbl
f,l=adjust(f,l,s)
tbl=view(tbl,f,l)
local r={}
for i=f,l do
local n,k=c(tbl[i],i,tbl)
if n~=nil then
if k then r[k]=n
else r[#r+1]=n end
end
end
return r
end

function lib.where(tbl,p,f,l)
return lib.foreach(tbl,
function(e,i,tbl)
return p(e,i,tbl)and e or nil
end,f,l)
end



function lib.at(tbl,index)
checkArg(1,tbl,"table")
checkArg(2,index,"number","nil")
local current_index=1
for k,v in pairs(tbl)do
if current_index==index then
return k,v
end
current_index=current_index+1
end
return nil,current_index-1
end