defmodule SyntropyWeb.Api.RunRequest do
  @moduledoc false

  @type parsed_request :: %{prompt: String.t(), opts: keyword()}

  @strategies ~w(single parallel all auto)
  @required_source_fields ~w(engine repository review_goal)
  @source_tool_actions ~w(search open_file related_files dependency_context)

  @spec parse(map()) :: {:ok, parsed_request()} | {:error, [map()]}
  def parse(params) do
    with {:ok, prompt} <- parse_prompt(Map.get(params, "prompt")),
         {:ok, strategy} <- parse_strategy(Map.get(params, "strategy")),
         {:ok, agent_ids} <- parse_agent_ids(Map.get(params, "agent_ids")),
         {:ok, agent_count} <-
           parse_positive_integer(Map.get(params, "agent_count"), 3, "agent_count"),
         {:ok, synthesize} <- parse_boolean(Map.get(params, "synthesize"), true, "synthesize"),
         {:ok, source_review} <- parse_source_review(Map.get(params, "source_review")),
         {:ok, source_tool} <- parse_source_tool(Map.get(params, "source_tool")),
         :ok <- validate_source_tool_context(source_tool, source_review),
         {:ok, code_review} <- parse_code_review(Map.get(params, "code_review")),
         {:ok, kind} <- parse_kind(Map.get(params, "kind"), source_review),
         :ok <- validate_code_review_context(kind, code_review, source_review, source_tool) do
      {:ok,
       %{
         prompt: prompt,
         opts:
           []
           |> Keyword.put(:strategy, strategy)
           |> maybe_put(:agent_ids, agent_ids)
           |> Keyword.put(:agent_count, agent_count)
           |> Keyword.put(:synthesize, synthesize)
           |> Keyword.put(:kind, kind)
           |> maybe_put(:source_review, source_review)
           |> maybe_put(:source_tool, source_tool)
           |> maybe_put(:code_review, code_review)
       }}
    else
      {:error, errors} -> {:error, errors}
    end
  end

  defp maybe_put(opts, _key, nil), do: opts
  defp maybe_put(opts, key, value), do: Keyword.put(opts, key, value)

  defp parse_prompt(prompt) when is_binary(prompt) do
    trimmed = String.trim(prompt)

    if trimmed == "" do
      {:error, [error("prompt", "must be a non-empty string")]}
    else
      {:ok, trimmed}
    end
  end

  defp parse_prompt(_prompt), do: {:error, [error("prompt", "is required")]}

  defp parse_strategy(nil), do: {:ok, :parallel}

  defp parse_strategy(strategy) when is_binary(strategy) do
    if strategy in @strategies do
      {:ok, String.to_atom(strategy)}
    else
      {:error, [error("strategy", "must be one of single, parallel, all, auto")]}
    end
  end

  defp parse_strategy(_strategy),
    do: {:error, [error("strategy", "must be one of single, parallel, all, auto")]}

  defp parse_agent_ids(nil), do: {:ok, nil}

  defp parse_agent_ids(agent_ids) when is_list(agent_ids) do
    if Enum.all?(agent_ids, &is_binary/1) do
      {:ok, agent_ids}
    else
      {:error, [error("agent_ids", "must be an array of strings")]}
    end
  end

  defp parse_agent_ids(_agent_ids),
    do: {:error, [error("agent_ids", "must be an array of strings")]}

  defp parse_positive_integer(nil, default, _field), do: {:ok, default}

  defp parse_positive_integer(value, _default, _field) when is_integer(value) and value > 0,
    do: {:ok, value}

  defp parse_positive_integer(value, _default, field) when is_binary(value) do
    case Integer.parse(value) do
      {parsed, ""} when parsed > 0 -> {:ok, parsed}
      _other -> {:error, [error(field, "must be a positive integer")]}
    end
  end

  defp parse_positive_integer(_value, _default, field),
    do: {:error, [error(field, "must be a positive integer")]}

  defp parse_boolean(nil, default, _field), do: {:ok, default}
  defp parse_boolean(value, _default, _field) when is_boolean(value), do: {:ok, value}
  defp parse_boolean(_value, _default, field), do: {:error, [error(field, "must be a boolean")]}

  defp parse_kind(nil, nil), do: {:ok, "prompt"}
  defp parse_kind(nil, _source_review), do: {:ok, "source_review"}

  defp parse_kind(kind, _source_review) when kind in ["prompt", "source_review", "code_review"],
    do: {:ok, kind}

  defp parse_kind(_kind, _source_review),
    do: {:error, [error("kind", "must be prompt, source_review, or code_review")]}

  # Receipts runs read a local repository, so they sit behind the same gate
  # as the local source tool. `code_review` is never inferred: the kind must
  # be explicit and the payload must travel with it, exclusively.
  defp parse_code_review(nil), do: {:ok, nil}

  defp parse_code_review(code_review) when is_map(code_review) do
    checks = Map.get(code_review, "checks")

    cond do
      not source_tool_enabled?() ->
        {:error, [error("code_review", "is disabled in this environment")]}

      not present_string?(Map.get(code_review, "repo_path")) ->
        {:error, [error("code_review.repo_path", "is required")]}

      not present_string?(Map.get(code_review, "base")) ->
        {:error, [error("code_review.base", "is required")]}

      not (is_nil(checks) or (is_list(checks) and Enum.all?(checks, &present_string?/1))) ->
        {:error, [error("code_review.checks", "must be an array of check names")]}

      true ->
        {:ok, normalize_code_review(code_review, checks)}
    end
  end

  defp parse_code_review(_code_review),
    do: {:error, [error("code_review", "must be an object")]}

  defp validate_code_review_context("code_review", nil, _source_review, _source_tool),
    do: {:error, [error("code_review", "is required when kind is code_review")]}

  defp validate_code_review_context("code_review", _code_review, source_review, source_tool)
       when not is_nil(source_review) or not is_nil(source_tool),
       do:
         {:error, [error("code_review", "cannot be combined with source_review or source_tool")]}

  defp validate_code_review_context("code_review", _code_review, _source_review, _source_tool),
    do: :ok

  defp validate_code_review_context(_kind, nil, _source_review, _source_tool), do: :ok

  defp validate_code_review_context(_kind, _code_review, _source_review, _source_tool),
    do: {:error, [error("kind", "must be code_review when a code_review object is provided")]}

  defp normalize_code_review(code_review, checks) do
    normalized = %{
      "repo_path" => String.trim(Map.get(code_review, "repo_path")),
      "base" => String.trim(Map.get(code_review, "base"))
    }

    normalized =
      case Map.get(code_review, "head") do
        head when is_binary(head) -> Map.put(normalized, "head", String.trim(head))
        _other -> normalized
      end

    if is_list(checks) do
      Map.put(normalized, "checks", Enum.map(checks, &String.trim/1))
    else
      normalized
    end
  end

  defp parse_source_review(nil), do: {:ok, nil}

  defp parse_source_review(source_review) when is_map(source_review) do
    missing =
      Enum.filter(@required_source_fields, fn field ->
        not present_string?(Map.get(source_review, field))
      end)

    focus_areas = Map.get(source_review, "focus_areas")

    cond do
      missing != [] ->
        {:error,
         Enum.map(missing, fn field -> error("source_review.#{field}", "is required") end)}

      not is_list(focus_areas) ->
        {:error, [error("source_review.focus_areas", "must be an array")]}

      true ->
        {:ok, source_review}
    end
  end

  defp parse_source_review(_source_review),
    do: {:error, [error("source_review", "must be an object")]}

  defp parse_source_tool(nil), do: {:ok, nil}

  defp parse_source_tool(source_tool) when is_map(source_tool) do
    cond do
      not source_tool_enabled?() ->
        {:error, [error("source_tool", "is disabled in this environment")]}

      Map.get(source_tool, "engine") != "librarian" ->
        {:error, [error("source_tool.engine", "must be librarian")]}

      not present_string?(Map.get(source_tool, "repo_path")) ->
        {:error, [error("source_tool.repo_path", "is required")]}

      true ->
        with {:ok, allowed_actions} <-
               parse_source_tool_actions(Map.get(source_tool, "allowed_actions")) do
          {:ok, normalize_source_tool(source_tool, allowed_actions)}
        end
    end
  end

  defp parse_source_tool(_source_tool),
    do: {:error, [error("source_tool", "must be an object")]}

  defp validate_source_tool_context(nil, _source_review), do: :ok

  defp validate_source_tool_context(_source_tool, source_review) when is_map(source_review) do
    if Map.get(source_review, "engine") == "librarian" do
      :ok
    else
      {:error, [error("source_tool", "requires a librarian source_review")]}
    end
  end

  defp validate_source_tool_context(_source_tool, _source_review),
    do: {:error, [error("source_tool", "requires source_review")]}

  defp source_tool_enabled? do
    Application.get_env(:syntropy, :source_tool_enabled, false) ||
      System.get_env("SYNTROPY_ENABLE_LOCAL_REPO_REVIEW") == "true"
  end

  defp normalize_source_tool(source_tool, allowed_actions) do
    %{
      "engine" => "librarian",
      "repo_path" => String.trim(Map.get(source_tool, "repo_path")),
      "allowed_actions" => allowed_actions
    }
    |> maybe_put_source_tool_integer(source_tool, "budget")
    |> maybe_put_source_tool_integer(source_tool, "timeout_ms")
    |> maybe_put_source_tool_integer(source_tool, "max_stdout_bytes")
  end

  defp parse_source_tool_actions(nil), do: {:ok, @source_tool_actions}

  defp parse_source_tool_actions(actions) when is_list(actions) do
    normalized =
      actions
      |> Enum.map(fn
        action when is_binary(action) -> String.trim(action)
        _action -> nil
      end)

    unsupported =
      normalized
      |> Enum.reject(&(&1 in @source_tool_actions))

    cond do
      normalized == [] ->
        {:error, [error("source_tool.allowed_actions", "must include at least one action")]}

      unsupported != [] ->
        {:error,
         [
           error(
             "source_tool.allowed_actions",
             "must contain only search, open_file, related_files, or dependency_context"
           )
         ]}

      true ->
        {:ok, Enum.uniq(normalized)}
    end
  end

  defp parse_source_tool_actions(_actions),
    do: {:error, [error("source_tool.allowed_actions", "must be an array of strings")]}

  defp maybe_put_source_tool_integer(normalized, source_tool, key) do
    case positive_integer_value(Map.get(source_tool, key)) do
      nil -> normalized
      value -> Map.put(normalized, key, value)
    end
  end

  defp positive_integer_value(value) when is_integer(value) and value > 0, do: value

  defp positive_integer_value(value) when is_binary(value) do
    case Integer.parse(value) do
      {parsed, ""} when parsed > 0 -> parsed
      _other -> nil
    end
  end

  defp positive_integer_value(_value), do: nil

  defp present_string?(value), do: is_binary(value) and String.trim(value) != ""

  defp error(field, message), do: %{field: field, message: message}
end