adding 3 loop types for connector

src/connector.jl

@@ -1,51 +1,92 @@
 using Tables
-
 abstract type AbstractConnector end
-
 Base.length(conn::AbstractConnector) = Inf
 hasnext(conn::AbstractConnector) = true
 reset!(conn::AbstractConnector) = nothing
 
+abstract type LoopType end
+struct Foward <: LoopType end
+struct Backward <: LoopType end
+struct Yoyo <: LoopType end
+struct None <: LoopType end
+
 mutable struct TablesConnector <: AbstractConnector
     rows
     state::Int
     args::Dict{Symbol, Any}
+    loop::LoopType
+    incremental::Int
 end
 
-function TablesConnector(data; shuffle::Bool = false)
+function TablesConnector(data; shuffle::Bool = false, loop::LoopType = None())
+
     if !Tables.istable(data)
         throw(ArgumentError("data must have the Tables.jl interface"))
     end
 
     if shuffle
         data = data[Random.shuffle(1:size(data,1)), :]
     end
-
-    return TablesConnector(Tables.rows(data), 0, Dict{Symbol, Any}())
+    state = typeof(loop) == typeof(Backward()) ? size(data, 1) + 1 : 0
+    incremental = typeof(loop) == typeof(Backward()) ? -1 : 1
+    return TablesConnector(Tables.rows(data), state, Dict{Symbol, Any}(),loop,incremental)
 end
 
-function TablesConnector(data, orderBy::Symbol; rev::Bool = false)
+
+
+function TablesConnector(data, orderBy::Symbol; rev::Bool = false, loop::LoopType = None())
     if !(orderBy in propertynames(data))
         throw(ArgumentError("data doesn't have the column $orderBy"))
     end
 
     data = sort(data, orderBy, rev = rev)
-
-    return TablesConnector(data)
+    return TablesConnector(data;loop = loop)
 end
 
 TablesConnector(filename::String) = TablesConnector(CSV.read(filename; header = false))
 
 Base.length(conn::TablesConnector) = length(conn.rows)
-hasnext(conn::TablesConnector) = conn.state < length(conn)
+function hasnext(conn::TablesConnector)
+    if typeof(conn.loop) == typeof(None())
+        return conn.state < length(conn)
+    else
+        return true
+    end
+end
+
+function next(conn::TablesConnector) return next(conn,conn.loop) end
 
-function next(conn::TablesConnector)
+function next(conn::TablesConnector,::None)
     if conn.state >= length(conn)
         return nothing
     end
 
     conn.state += 1
+    return DataFrame([conn.rows[conn.state]])
+end
+
+function next(conn::TablesConnector,::Foward)
+    conn.state += conn.incremental
+    temp = conn.state % length(conn)
+    conn.state = temp == 0 ? length(conn) : temp
+    return DataFrame([conn.rows[conn.state]])
+end
 
+function next(conn::TablesConnector,::Backward)
+    conn.state += conn.incremental
+    temp = conn.state % length(conn)
+    conn.state = temp == 0 ? length(conn) : temp
+    return DataFrame([conn.rows[conn.state]])
+end
+
+function next(conn::TablesConnector,::Yoyo)
+    conn.state += conn.incremental
+    if conn.state == length(conn)
+        conn.incremental *= - 1
+    elseif conn.state == 0
+        conn.state = 2
+        conn.incremental *= - 1
+    end
     return DataFrame([conn.rows[conn.state]])
 end
 
@@ -64,6 +105,6 @@ end
 function next(conn::GeneratorConnector)
     total = 100
     data = conn.generator(;n_samples = total, conn.args...)
-    
+
     return DataFrame(data[1 + Int(floor(rand(1,1)[1] .* size(data)[1])), :])
 end