defmodule RiakEcto3 do
  @default_hostname "localhost"
  @default_port 8087

  @moduledoc """
  Riak KV 2.0 adapter for Ecto 3.
  Works by mapping Ecto Schemas to Riak Map-CRDTs.

  **NOTE:** To use, ensure the following has been executed on your Riak database:

      riak-admin bucket-type create your_database_name '{"props":{"datatype":"map"}}'
      riak-admin bucket-type activate your_database_name

  Here, `your_database_name` refers to any name you'd like the bucket type
  that RiakEcto3 will use to be called. This is the same name you should use
  in your configuration.
  The `mix ecto.create` task will also do this for you.

  ## Supported Configuration Options:

  - `database:` Name of the `bucket_type` to use for storing all data of this Repo.
  This should be a bucket_type that has the datatype set to `map`.
  - `hostname:` The hostname to connect to. Defaults to `#{@default_hostname}`.
  - `port:` The port to connect to. Defaults to `#{@default_port}`.

  ## Ecto

  RiakEcto3 currently does not use a pool (but this might change in the future).

  ## Queries

  RiakEcto3 only supports `get`.

  (In the future, hopefully we support simple 2i (secondary indexes) as well)

  ## Mix tasks

  ### Storage

  RiakEcto3 only supports the `mix ecto.create` task.
  This task will use `riak-admin` locally to create an appropriate bucket-type
  that uses the `map` CRDT.
  Be aware that `riak-admin` does not use any connection-settings, as it expects
  to be ran on the computer that (one of the nodes of) the database will reside on.

  The `mix ecto.drop` task is not supported, because Riak has no way to
  drop an existing bucket_type.
  """

  @behaviour Ecto.Adapter
  @behaviour Ecto.Adapter.Storage

  @impl Ecto.Adapter
  defmacro __before_compile__(_env) do
    quote do

      @doc """
      Fetches a struct using the given primary key `id`.

      On success, will return the struct.
      On failure (if the struct does not exist within the Riak database), returns `nil`.

      iex> alice = %User{name: "Alice", age: 10, id: "33"}
      iex> Repo.get(User, "33") == nil
      true
      iex> {:ok, %User{name: "Alice", age: 10, id: "33"}} = Repo.insert(alice)
      iex> %user{name: "Alice", age: 10, id: "33"} = Repo.get(User, "33")
      iex> {:ok, %User{name: "Alice", age: 10, id: "33"}} = Repo.delete(alice)
      iex> Repo.get(User, "33") == nil
      true

      """
      def get(schema_module, id, opts \\ []) do
        {adapter, meta} = Ecto.Repo.Registry.lookup(__MODULE__)
        adapter.get(__MODULE__, meta, schema_module, id, opts)
      end

      @doc """
      Inserts (or updates) a struct in the database.
      Pass either a struct or an `Ecto.Changeset`

      On success, will return `{:ok, struct}`.
      On failure (when there were validation problems for instance), will return `{:error, struct_or_changeset}`
      """
      def insert(struct_or_changeset, opts \\ []) do
        {adapter, meta} = Ecto.Repo.Registry.lookup(__MODULE__)
        adapter.insert(__MODULE__, meta, struct_or_changeset, opts)
      end

      @doc """
      Deletes a struct from the database, using the primary ID of the struct or changeset
      passed to this function.

      Returns `{:ok, struct}` on success.
      Raises `Ecto.NoPrimaryKeyValueError` if the passed struct or changeset does not have a primary key set.
      """
      def delete(struct_or_changeset, opts \\ []) do
        {adapter, meta} = Ecto.Repo.Registry.lookup(__MODULE__)
        adapter.delete(__MODULE__, meta, struct_or_changeset, opts)
      end

      @doc """
      Allows you to perform a raw SOLR query on a given Schema module.

      See https://docs.riak.com/riak/kv/2.2.3/developing/usage/search/index.html
      and https://docs.riak.com/riak/kv/2.2.3/developing/usage/searching-data-types.1.html#data-types-and-search-examples

      for more information and syntax.

      A query is prefixed to constrain it to the given schema module's bucket (in the database's bucket type).

      The response of this will either be `{:error, problem}` or `{:ok, results}`
      where `results` will be a list of maps.
      Each of these maps has a `:meta`-key containing the raw SOLR result for that resource,
      and a `:resource` key, which is a 0-arity function that will fetch the given resource from the repo when called.

      Example:

      iex> bob = %User{name: "Bob", id: "42", age: 41}
      iex> {:ok, _} = Repo.insert(bob)
      iex> :timer.sleep(1000) # It takes 'typically a second' before SOLR is able to see changes.
      iex> {:ok, results} = Repo.riak_raw_solr_query(RiakEcto3Test.Example.User, "age_register:[40 TO 41]")
      iex> results |> Enum.map(fn elem -> elem.resource.() end) |> Enum.any?(fn user -> user.name == "Bob" end)
      true
      """
      def riak_raw_solr_query(schema_module, query, solr_opts \\ []) do
        {adapter, meta} = Ecto.Repo.Registry.lookup(__MODULE__)
        adapter.raw_solr_query(__MODULE__, meta, schema_module, query, solr_opts)
      end

      @doc """
      Allows you look up all keys in between a lower and upper bound.

      Be aware that since all Riak keys are strings, these lower and upper bounds are also cast to strings,
      and that lexicographical comparisons are made!

      Under the hood, it uses Riak's 'secondary indexes', which are only supported when using the
      'Leveldb' or 'Memory' storage backends.

      Example:

      iex> bob = %User{name: "Bob", id: "1234", age: 38}
      iex> {:ok, _} = Repo.insert(bob)
      iex> jose = %User{name: "Jose", id: "1240", age: 30}
      iex> {:ok, _} = Repo.insert(jose)
      iex> Repo.riak_find_keys_between(User, "1200", "1300") |> Enum.sort
      ["1234", "1240"]
      """
      def riak_find_keys_between(schema_module, lower_bound, upper_bound) do
        {adapter, meta} = Ecto.Repo.Registry.lookup(__MODULE__)
        adapter.find_keys_between(__MODULE__, meta, schema_module, lower_bound, upper_bound)
      end
    end
  end


  @impl Ecto.Adapter
  @doc """
  NOTE: Currently we are not using the connection pool to keep the implementation simple.
  This could be changed in a future version since `Riak` provides one.
  """
  def checkout(_adapter_meta, _config, fun) do
    fun.()
  end

  @impl Ecto.Adapter
  @doc """
  Dumps datatypes so they can properly be stored in Riak
  """
  def dumpers(primitive_type, ecto_type)
  def dumpers(:string, type), do: [type, &RiakEcto3.Dumpers.string/1]
  def dumpers(:id, type), do: [type, &RiakEcto3.Dumpers.integer/1]
  def dumpers(:integer, type), do: [type, &RiakEcto3.Dumpers.integer/1]
  def dumpers(:boolean, type), do: [type, &RiakEcto3.Dumpers.boolean/1]
  def dumpers(:float, type), do: [type, &RiakEcto3.Dumpers.float/1]
  def dumpers(:binary_id, type), do: [type, &RiakEcto3.Dumpers.string/1]
  def dumpers(_primitive, type) do
    [type]
  end

  @impl Ecto.Adapter
  @doc """
  Implementation of Ecto.Adapter.ensure_all_started
  """
  def ensure_all_started(_config, app_restart_type) do
    with {:ok, from_driver} <- Application.ensure_all_started(:riak, app_restart_type) do
      # We always return the adapter to force it to be restarted if necessary, because this is what `ecto_sql` also does.
      # See: https://github.com/elixir-ecto/ecto_sql/blob/master/lib/ecto/adapters/sql.ex#L420
      {:ok, (List.delete(from_driver, :riak) ++ [:riak])}
    end
  end

  @impl Ecto.Adapter
  @doc """
  Initializes the connection with Riak.

  Implementation of Ecto.Adapter.init
  """
  def init(config) do
    hostname = Keyword.get(config, :hostname, @default_hostname)
    port = Keyword.get(config, :port, @default_port)
    child_spec = %{id: Riak.Connection, start: {Riak.Connection, :start_link, [String.to_charlist(hostname), port]}}
    {:ok, child_spec, %{}}
  end

  @impl Ecto.Adapter
  @doc """
  TODO Properly implement
  """
  def loaders(primitive_type, ecto_type)
  def loaders(:string, type), do: [&RiakEcto3.Loaders.string/1, type]
  def loaders(:id, type), do: [&RiakEcto3.Loaders.integer/1, type]
  def loaders(:integer, type), do: [&RiakEcto3.Loaders.integer/1, type]
  def loaders(:boolean, type), do: [&RiakEcto3.Loaders.boolean/1, type]
  def loaders(:float, type), do: [&RiakEcto3.Loaders.float/1, type]
  def loaders(:binary_id, type), do: [&RiakEcto3.Loaders.string/1, type]
  def loaders(_primitive, type), do: [type]

  @doc """
  Implementation of Repo.get

  Returns `nil` if nothing is found. Returns the structure if something was found.
  Raises an ArgumentError using improperly.
  """
  def get(repo, meta, schema_module, id, _opts) do
    source = schema_module.__schema__(:source)
    riak_id = "#{id}"
    result = Riak.find(meta.pid, repo.config[:database], source, riak_id)
    case result do
      {:error, problem} -> raise ArgumentError, "Riak error: #{problem}"
      nil -> nil
      riak_map ->
        repo.load(schema_module, load_riak_map(riak_map))
    end
  end

  defp load_riak_map(riak_map) do
    riak_map
    |> Riak.CRDT.Map.value
    |> Enum.map(fn {{key, value_type}, riak_value} ->
      value = case value_type do
                :register -> riak_value # String
                :counter -> riak_value # TODO
                :flag -> riak_value # TODO
                :map -> raise "Not Implemented"
              end
      {String.to_existing_atom(key), value}
    end)
    |> Enum.into(%{})
  end

  def dump(struct = %schema_module{}) do
    build_riak_map(schema_module, Map.from_struct(struct))
  end

  defp build_riak_map(schema_module, map = %{}) do
    map
    |> Map.to_list
    |> Enum.map(fn {key, value} ->
      type = schema_module.__schema__(:type, key)
      {key, type, value}
    end)
    |> Enum.reject(fn {_key, type, _} ->
      type == nil
    end)
    |> Enum.map(fn {key, type, value} ->
      case Ecto.Type.adapter_dump(__MODULE__, type, value) do
        {:ok, riak_value} ->
          {Atom.to_string(key), riak_value}
          _ -> raise "Could not properly dump `#{value}` to Ecto type `#{inspect(type)}`. Please make sure it is cast properly."
      end
    end)
    |> Enum.reduce(Riak.CRDT.Map.new, fn {key, value}, riak_map ->
      Riak.CRDT.Map.put(riak_map, key, value)
    end)
  end

  @doc """
  Implementation of Repo.insert
  """
  def insert(repo, meta, struct_or_changeset, opts)
  def insert(repo, meta, changeset = %Ecto.Changeset{data: struct = %schema_module{}, changes: changes}, opts) do
    riak_map = build_riak_map(schema_module, changes)

    source = schema_module.__schema__(:source)
    [primary_key | _] = schema_module.__schema__(:primary_key)
    riak_id = "#{Map.fetch!(struct, primary_key)}"

    case do_insert(repo, meta, source, riak_map, riak_id, schema_module, opts) do
      :ok -> {:ok, repo.get(schema_module, riak_id)}
      :error -> {:error, changeset}
    end
  end
  def insert(repo, meta, struct = %schema_module{}, opts) do
    riak_map = dump(struct)

    source = schema_module.__schema__(:source)
    [primary_key | _] = schema_module.__schema__(:primary_key)
    riak_id = "#{Map.fetch!(struct, primary_key)}"

    case do_insert(repo, meta, source, riak_map, riak_id, schema_module, opts) do
      :ok -> {:ok, repo.get(schema_module, riak_id)}
      :error -> {:error, Ecto.Changeset.change(struct)}
    end
  end

  defp do_insert(repo, meta, source, riak_map, riak_id, schema_module, _opts) do
    case Riak.update(meta.pid, riak_map, repo.config[:database], source, riak_id) do
      {:ok, riak_map} ->
        res = repo.load(schema_module, load_riak_map(riak_map))
        {:ok, res}
      other ->
        other
    end
  end

  @doc """
  Implementation of Repo.delete
  """
  def delete(repo, meta, struct_or_changeset, opts)
  def delete(_repo, _meta, changeset = %Ecto.Changeset{valid?: false}, _opts) do
    {:error, changeset}
  end
  def delete(repo, meta, %Ecto.Changeset{data: struct = %_schema_module{}}, opts) do
    delete(repo, meta, struct, opts)
  end

  def delete(repo, meta, struct = %schema_module{}, _opts) do
    source = schema_module.__schema__(:source)
    [primary_key | _] = schema_module.__schema__(:primary_key)
    riak_id = "#{Map.fetch!(struct, primary_key)}"
    if riak_id == "" do
      raise Ecto.NoPrimaryKeyValueError
    end

    case Riak.delete(meta.pid, repo.config[:database], source, riak_id) do
      :ok -> {:ok, struct}
      :error -> raise Ecto.StaleEntryError
    end
  end

  def raw_solr_query(repo, meta, schema_module, query, solr_opts) do
    require Logger

    source = schema_module.__schema__(:source)
    database = repo.config[:database]
    compound_query = ~s[_yz_rt:"#{database}" AND _yz_rb:"#{source}" AND #{query}]
    index = "#{database}_index"
    case Riak.Search.query(meta.pid, index, compound_query, solr_opts) do
      {:error, problem} ->
        Logger.debug("Solr Query that was executed: #{compound_query}")
        {:error, problem}
      {:ok, {:search_results, results, _max_score, _num_found}} ->
        results =
          results
          |> Enum.map(fn {_index_name, properties} ->
          meta = Enum.into(properties, %{})
          resource = fn -> repo.get(schema_module, meta["_yz_rk"]) end
          %{meta: meta, resource: resource}
        end)
        {:ok, results}
    end
  end

  def find_keys_between(repo, meta, schema_module, lower_bound, upper_bound) do
    source = schema_module.__schema__(:source)
    database = repo.config[:database]
    {:ok, {:index_results_v1, results, _, _}} = :riakc_pb_socket.get_index(meta.pid, {database, source}, "$key", to_string(lower_bound), to_string(upper_bound))
    results
  end


  @impl Ecto.Adapter.Storage
  def storage_up(config) do
    require Logger
    {:ok, database} = Keyword.fetch(config, :database)
    already_exists_binary = "Error creating bucket type #{database}:\nalready_active\n"
    with hostname = Keyword.get(config, :hostname, @default_hostname),
         port = Keyword.get(config, :port, @default_port),
         {:ok, pid} <- Riak.Connection.start_link(String.to_charlist(hostname), port),
           Logger.info("Creating bucket type `#{database}`..."),
         {res1, 0} <- System.cmd("riak-admin", ["bucket-type", "create", database, ~s[{"props":{"datatype":"map"}}]]),
           Logger.info("Activating Bucket Type `#{database}`..."),
         {res2, 0} <- System.cmd("riak-admin", ["bucket-type", "activate", database]),
           database_index = "#{database}_index",
           Logger.info("Creating Search Index `#{database_index}`..."),
           :ok <- Riak.Search.Index.put(pid, database_index),
           Logger.info("Associating Search Index `#{database_index}`with bucket type `#{database}`..."),
           :ok <- Riak.Bucket.Type.put(pid, database, search_index: database_index)
      do
      IO.puts res1
      IO.puts res2
      :ok
      else
        {^already_exists_binary, 1} ->
          {:error, :already_up}
        {command_error_string, 1} when is_binary(command_error_string) ->
          IO.inspect(command_error_string, label: "command_error_string")
        {:error, command_error_string}
        error ->
          {:error, error}
    end
  end

  @impl Ecto.Adapter.Storage
  def storage_down(config) do
    require Logger
    with {:ok, database} <- Keyword.fetch(config, :database),
         hostname = Keyword.get(config, :hostname, @default_hostname),
           port = Keyword.get(config, :port, @default_port),
         {:ok, pid} <- Riak.Connection.start_link(String.to_charlist(hostname), port),
           buckets = Riak.Bucket.Type.list!(pid, database) do
      for bucket <- buckets do
        Logger.info "Flushing values in bucket `#{bucket}`"
        keys = Riak.Bucket.keys!(pid, database, bucket)
        n_keys = Enum.count(keys)

        keys
        |> Enum.with_index
        |> Enum.each(fn {key, index} ->
          Riak.delete(pid, database, bucket, key)
          ProgressBar.render(index + 1, n_keys)
        end)
      end
      Logger.info "NOTE: Riak does not support 'dropping' a bucket type (or buckets contained within), so this task has only removed all data contained within them."
      :ok
    end
  end
end