Finish markov chain generation impl

* Markov chains will train and generate chains correctly now
* Implement Markov.save_chains/0
* Add a couple more utils that help accomplish the above

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

lib/contrib/markov/chain.ex

@@ -1,5 +1,5 @@
 defmodule Omnibot.Contrib.Markov.Chain do
-  alias Omnibot.Contrib.Markov.Chain
+  alias Omnibot.{Contrib.Markov.Chain, Util}
 
   @enforce_keys [:order]
   defstruct order: 2, chain: []
@@ -14,17 +14,18 @@ defmodule Omnibot.Contrib.Markov.Chain do
     Enum.filter(words, &(String.length(&1) > 0))
     |> Enum.chunk_every(order + 1, 1) # this gives us a "sliding window" effect
     |> Enum.reduce(chain, &case Enum.split(&1, order) do
-      {words, []} -> if length(words) == order,
+      {words, []} when length(words) == order -> add_weight(&2, words, nil)
-          # Null case for the chain; this is an "end" state
+      {words, []} -> add_weight(&2, Util.pad_trailing(words, nil, order), nil)
-          do: add_weight(&2, words, nil),
-          else: &2 # TODO ? train [a, nil] -> b ?
       {words, [next]} -> add_weight(&2, words, next)
     end)
   end
 
   def add_weight(%Chain {chain: chain, order: order}, key, word, increment \\ 1) do
-    if length(key) != order, do: raise(ArgumentError, message: "invalid key (length #{length(key)} vs. order #{order})")
+    if length(key) != order do
-    chain = case Enum.find_index(chain, fn {listkey, _} -> listkey == key end) do
+      raise(ArgumentError, message: "invalid key (length #{length(key)} vs. order #{order})")
+    end
+
+    chain = case find_index(chain, key) do
       # Insert weight
       nil -> [{key, %{word => increment}} | chain]
       # Update weight
@@ -36,4 +37,38 @@ defmodule Omnibot.Contrib.Markov.Chain do
     end
     %Chain{chain: chain, order: order}
   end
+
+  def get(chain, key) when is_list(chain) do
+    item = Enum.find(chain, fn {listkey, _} -> listkey == key end)
+    case item do
+      nil -> nil
+      {_, weights} -> weights
+    end
+  end
+
+  def get(chain, key), do: get(chain.chain, key)
+
+  def find_index(chain, key) when is_list(chain) do
+    Enum.find_index(chain, fn {listkey, _} -> listkey == key end)
+  end
+
+  def find_index(chain = %Chain{}, key), do: find_index(chain.chain, key)
+
+  def generate(chain) do
+    {seed, _} = Stream.filter(chain.chain, fn {key, _} -> length(key) == chain.order end)
+                |> Enum.random()
+    generate(chain, seed)
+  end
+
+  def generate(chain, key) do
+    do_generate(chain, key) |> Enum.join(" ")
+  end
+
+  defp do_generate(_chain, [nil | _]), do: []
+
+  defp do_generate(chain, key) do
+    weights = get(chain, key) || []
+    [next | key] = key ++ [Util.weighted_random(weights)]
+    [next | do_generate(chain, key)]
+  end
 end

lib/contrib/markov/markov.ex

@@ -1,28 +1,44 @@
 defmodule Omnibot.Contrib.Markov do
   use Omnibot.Plugin
-  alias Omnibot.Contrib.Markov.Chain
+  alias Omnibot.{Contrib.Markov.Chain, Util}
   require Logger
 
-  @default_config path: "markov", order: 2, save_every: 5 * 60
+  @default_config path: "markov.ets", order: 2, save_every: 5 * 60
+
+  command "!markov", ["force"] do
+    # Choose a random value from the sender
+    Irc.send_to(irc, channel, "TODO")
+  end
+
+  command "!markov", ["all"] do
+    Irc.send_to(irc, channel, "TODO")
+  end
+
+  command "!markov", ["status"] do
+    Irc.send_to(irc, channel, "TODO")
+  end
 
   @impl true
   def children(cfg) do
-    [{Task, fn ->
+    [
+      {Task, fn ->
         Stream.timer(cfg[:save_every] * 1000)
         |> Stream.cycle()
         |> Stream.each(fn _ -> save_chains() end)
         |> Stream.run()
-    end}]
+      end}
+    ]
   end
 
   @impl true
   def on_init(_cfg) do
     # Create the markov database
     path = String.to_atom(cfg()[:path])
-    {:ok, db} = :dets.open_file(path, [:named_table])
+    {:ok, db} = :dets.open_file(path, [])
-    chains = :ets.new(:markov_chains, [:public])
+    chains = :ets.new(:markov_chains, [:named_table, :public])
     :dets.to_ets(db, chains)
-    :dets.close(db)
+    :ok = :dets.close(db)
+    chains
   end
 
   @impl true
@@ -48,7 +64,7 @@ defmodule Omnibot.Contrib.Markov do
     db = state()
     case user_chain(channel, user) do
       nil -> :ets.insert_new(db, {{channel, user}, chain})
-      chain -> :ets.insert(db, {{channel, user}, chain})
+      _old_chain -> :ets.insert(db, {{channel, user}, chain})
     end
   end
 
@@ -58,7 +74,14 @@ defmodule Omnibot.Contrib.Markov do
   end
 
   def save_chains() do
-    # TODO
+    start = Util.now_unix()
-    Logger.info("Saved markov chains")
+    Logger.debug("Saving markov chains")
+
+    {:ok, db} = :dets.open_file(cfg()[:path], [])
+    :ets.to_dets(state(), db)
+    :ok = :dets.close(db)
+
+    stop = Util.now_unix()
+    Logger.info("Saved markov chains in #{stop - start} seconds")
   end
 end

lib/util.ex

@@ -14,4 +14,27 @@ defmodule Omnibot.Util do
   def denotify_nick(nick) do
     String.graphemes(nick) |> Enum.join("\u200b")
   end
+
+  def weighted_random(items) when is_map(items) do
+    Enum.to_list(items) |> weighted_random()
+  end
+
+  def weighted_random([]), do: nil
+
+  def weighted_random(items) do
+    value = items
+            |> Enum.reduce(0, fn {_, weight}, total -> total + weight end)
+            |> :rand.uniform()
+    select_item(items, value)
+  end
+
+  defp select_item([{item, _}], _), do: item
+
+  defp select_item([{item, weight} | _], index) when weight >= index, do: item
+
+  defp select_item([{_, weight} | tail], index), do: select_item(tail, index - weight)
+
+  def pad_trailing(list, _what, len) when length(list) >= len, do: list
+
+  def pad_trailing(list, what, len), do: pad_trailing(list ++ [what], what, len)
 end

test/contrib/markov/chain_test.exs

@@ -9,6 +9,32 @@ defmodule MarkovChainTest do
       {["bar", "baz"], %{nil => 1}},
       {["foo", "bar"], %{"baz" => 1}},
     ]
+
+    chain = chain |> Chain.train(~w(foo bar baz))
+
+    assert chain.chain == [
+      {["bar", "baz"], %{nil => 2}},
+      {["foo", "bar"], %{"baz" => 2}},
+    ]
+
+    chain = chain |> Chain.train(~w(baz bar foo))
+
+    assert chain.chain == [
+      {["bar", "foo"], %{nil => 1}},
+      {["baz", "bar"], %{"foo" => 1}},
+      {["bar", "baz"], %{nil => 2}},
+      {["foo", "bar"], %{"baz" => 2}},
+    ]
+
+    chain = chain |> Chain.train(~w(a b c))
+    assert chain.chain == [
+      {["b", "c"], %{nil => 1}},
+      {["a", "b"], %{"c" => 1}},
+      {["bar", "foo"], %{nil => 1}},
+      {["baz", "bar"], %{"foo" => 1}},
+      {["bar", "baz"], %{nil => 2}},
+      {["foo", "bar"], %{"baz" => 2}},
+    ]
   end
 
   test "chain add_weight works correctly" do
@@ -28,5 +54,17 @@ defmodule MarkovChainTest do
     assert chain.chain == [
       {["foo", "bar"], %{"baz" => 3, "qux" => 1}}
     ]
+
+    chain = chain |> Chain.add_weight(["bar", "baz"], "qux")
+    assert chain.chain == [
+      {["bar", "baz"], %{"qux" => 1}},
+      {["foo", "bar"], %{"baz" => 3, "qux" => 1}},
+    ]
+
+    chain = chain |> Chain.add_weight(["bar", "baz"], nil)
+    assert chain.chain == [
+      {["bar", "baz"], %{"qux" => 1, nil => 1}},
+      {["foo", "bar"], %{"baz" => 3, "qux" => 1}},
+    ]
   end
 end

test/util_test.exs

@@ -12,4 +12,14 @@ defmodule Omnibot.UtilTest do
     assert Util.string_or_nil("") == nil
     assert Util.string_or_nil("asdf") == "asdf"
   end
+
+  test "pad_trailing" do
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 7) == [1, 2, 3, 4, nil, nil, nil]
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 6) == [1, 2, 3, 4, nil, nil]
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 5) == [1, 2, 3, 4, nil]
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 4) == [1, 2, 3, 4]
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 3) == [1, 2, 3, 4]
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 2) == [1, 2, 3, 4]
+    assert Util.pad_trailing([1, 2, 3, 4], nil, 1) == [1, 2, 3, 4]
+  end
 end