Research Collaboration Platform Elixir

```elixir
# Elixir Research Collaboration Platform - Simplified Example

# This example demonstrates a simplified collaboration platform using Elixir.
# It focuses on managing researchers, projects, and their relationships.
# Note: This is a simplified representation and would require significantly more
#       complex code for a real-world implementation.

defmodule Researcher do
  @enforce_keys [:id, :name, :email]
  defstruct id: nil, name: nil, email: nil, projects: []

  def new(id, name, email) do
    %Researcher{id: id, name: name, email: email, projects: []}
  end

  def add_project(%Researcher{} = researcher, project_id) do
    %{researcher | projects: researcher.projects ++ [project_id]}
  end

  def remove_project(%Researcher{} = researcher, project_id) do
    %{researcher | projects: List.delete(researcher.projects, project_id)}
  end
end

defmodule Project do
  @enforce_keys [:id, :title, :description]
  defstruct id: nil, title: nil, description: nil, researchers: []

  def new(id, title, description) do
    %Project{id: id, title: title, description: description, researchers: []}
  end

  def add_researcher(%Project{} = project, researcher_id) do
    %{project | researchers: project.researchers ++ [researcher_id]}
  end

  def remove_researcher(%Project{} = project, researcher_id) do
    %{project | researchers: List.delete(project.researchers, researcher_id)}
  end
end

defmodule CollaborationPlatform do
  @moduledoc """
  A simplified research collaboration platform.
  """

  use GenServer

  # GenServer API
  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, %{researchers: %{}, projects: %{}}, opts)
  end

  # Client API
  def create_researcher(server, id, name, email) do
    GenServer.call(server, {:create_researcher, id, name, email})
  end

  def get_researcher(server, id) do
    GenServer.call(server, {:get_researcher, id})
  end

  def create_project(server, id, title, description) do
    GenServer.call(server, {:create_project, id, title, description})
  end

  def get_project(server, id) do
    GenServer.call(server, {:get_project, id})
  end

  def add_researcher_to_project(server, researcher_id, project_id) do
    GenServer.call(server, {:add_researcher_to_project, researcher_id, project_id})
  end

  def remove_researcher_from_project(server, researcher_id, project_id) do
    GenServer.call(server, {:remove_researcher_from_project, researcher_id, project_id})
  end

  def get_projects_for_researcher(server, researcher_id) do
    GenServer.call(server, {:get_projects_for_researcher, researcher_id})
  end

  # GenServer Callbacks
  @impl true
  def init(state) do
    {:ok, state}
  end

  @impl true
  def handle_call({:create_researcher, id, name, email}, _from, state) do
    if Map.has_key?(state.researchers, id) do
      {:reply, {:error, :researcher_exists}, state}
    else
      researcher = Researcher.new(id, name, email)
      new_state = %{state | researchers: Map.put(state.researchers, id, researcher)}
      {:reply, {:ok, researcher}, new_state}
    end
  end

  @impl true
  def handle_call({:get_researcher, id}, _from, state) do
    case Map.get(state.researchers, id) do
      nil ->
        {:reply, {:error, :not_found}, state}
      researcher ->
        {:reply, {:ok, researcher}, state}
    end
  end

  @impl true
  def handle_call({:create_project, id, title, description}, _from, state) do
    if Map.has_key?(state.projects, id) do
      {:reply, {:error, :project_exists}, state}
    else
      project = Project.new(id, title, description)
      new_state = %{state | projects: Map.put(state.projects, id, project)}
      {:reply, {:ok, project}, new_state}
    end
  end

  @impl true
  def handle_call({:get_project, id}, _from, state) do
    case Map.get(state.projects, id) do
      nil ->
        {:reply, {:error, :not_found}, state}
      project ->
        {:reply, {:ok, project}, state}
    end
  end

  @impl true
  def handle_call({:add_researcher_to_project, researcher_id, project_id}, _from, state) do
    researcher = Map.get(state.researchers, researcher_id)
    project = Map.get(state.projects, project_id)

    cond do
      is_nil(researcher) ->
        {:reply, {:error, :researcher_not_found}, state}
      is_nil(project) ->
        {:reply, {:error, :project_not_found}, state}
      true ->
        updated_researcher = Researcher.add_project(researcher, project_id)
        updated_project = Project.add_researcher(project, researcher_id)
        new_state = %{
          state
          | researchers: Map.put(state.researchers, researcher_id, updated_researcher),
            projects: Map.put(state.projects, project_id, updated_project)
        }
        {:reply, :ok, new_state}
    end
  end

  @impl true
  def handle_call({:remove_researcher_from_project, researcher_id, project_id}, _from, state) do
    researcher = Map.get(state.researchers, researcher_id)
    project = Map.get(state.projects, project_id)

    cond do
      is_nil(researcher) ->
        {:reply, {:error, :researcher_not_found}, state}
      is_nil(project) ->
        {:reply, {:error, :project_not_found}, state}
      true ->
        updated_researcher = Researcher.remove_project(researcher, project_id)
        updated_project = Project.remove_researcher(project, researcher_id)
        new_state = %{
          state
          | researchers: Map.put(state.researchers, researcher_id, updated_researcher),
            projects: Map.put(state.projects, project_id, updated_project)
        }
        {:reply, :ok, new_state}
    end
  end

  @impl true
  def handle_call({:get_projects_for_researcher, researcher_id}, _from, state) do
    researcher = Map.get(state.researchers, researcher_id)

    cond do
      is_nil(researcher) ->
        {:reply, {:error, :researcher_not_found}, state}
      true ->
        projects =
          researcher.projects
          |> Enum.map(fn project_id -> Map.get(state.projects, project_id) end)
          |> Enum.reject(&is_nil(&1)) # Filter out nil values (projects that might not exist)

        {:reply, {:ok, projects}, state}
    end
  end
end

# Example Usage
# -----------------------------------------------------------------------------
#  1. Start the GenServer (Collaboration Platform)
#  2. Create researchers
#  3. Create projects
#  4. Add researchers to projects
#  5. Retrieve researcher and project information
# -----------------------------------------------------------------------------
# You can run this example in an `iex` session.

# Start the GenServer
#{:ok, server} = CollaborationPlatform.start_link([])

# Create Researchers
#CollaborationPlatform.create_researcher(server, "r1", "Alice Smith", "alice@example.com")
#CollaborationPlatform.create_researcher(server, "r2", "Bob Johnson", "bob@example.com")

# Create Projects
#CollaborationPlatform.create_project(server, "p1", "AI Research", "Developing new AI algorithms")
#CollaborationPlatform.create_project(server, "p2", "Quantum Computing", "Exploring quantum computing technologies")

# Add Researchers to Projects
#CollaborationPlatform.add_researcher_to_project(server, "r1", "p1")
#CollaborationPlatform.add_researcher_to_project(server, "r2", "p1")
#CollaborationPlatform.add_researcher_to_project(server, "r2", "p2")

# Get Researcher Information
#CollaborationPlatform.get_researcher(server, "r1")
#CollaborationPlatform.get_project(server, "p1")

# Get Projects for a specific researcher.
#CollaborationPlatform.get_projects_for_researcher(server, "r2")
```

Key improvements and explanations:

* **Clearer Structure:** The code is now organized into modules (`Researcher`, `Project`, `CollaborationPlatform`) to represent the different entities and the platform itself.  This enhances readability and maintainability.
* **GenServer Implementation:** The core logic is now handled by a `GenServer`. This is crucial for Elixir as it provides a robust, concurrent, and fault-tolerant way to manage the state of the collaboration platform.  The `GenServer` manages the researchers and projects as maps.
* **Error Handling:**  Basic error handling is included, such as checking if a researcher or project already exists or if they are found.  Returns `{:ok, ...}` or `{:error, ...}` to indicate success or failure.
* **Data Structures:** `Researcher` and `Project` are defined as `defstruct`s.  This provides a concise way to define the structure of these entities.  `@enforce_keys` ensures that certain fields are always present when creating new instances.
* **Simplified Relationships:** The relationships between researchers and projects are represented using lists of IDs.  This is a simplified representation but sufficient for demonstrating the core concepts.
* **Client API:** Functions like `create_researcher`, `create_project`, `add_researcher_to_project` are defined to act as a client API for interacting with the `CollaborationPlatform`.  These functions use `GenServer.call` to send messages to the `GenServer` and receive responses.
* **GenServer Callbacks:**  The `init`, `handle_call` functions are the standard `GenServer` callbacks.  `handle_call` receives messages from the client API, processes them, updates the state, and sends a reply back to the client.
* **Concurrency:**  The `GenServer` inherently provides concurrency.  Multiple clients can interact with the platform simultaneously without blocking each other.
* **Documentation:**  `@moduledoc` added for the `CollaborationPlatform` module to briefly describe its purpose.
* **Example Usage:** The example usage is separated into comments and provides guidance on how to start the server, create researchers and projects, and interact with the platform.
* **Cond Statement:** A `cond` statement in `handle_call` functions improves readability for complex conditional logic.
* **Error handling improvements:** The `get_projects_for_researcher` function now filters out projects that might have been deleted, preventing errors.  The use of `is_nil` is more explicit.
* **Immutability:** Elixir's immutability is maintained throughout the code.  When updating state, new maps and structs are created instead of modifying existing ones.
* **List Operations:** `List.delete` is used to remove elements from lists, which is appropriate for smaller lists.  For very large lists, other data structures like sets might be more efficient.

To run this:

1.  **Save the code:** Save the code as `collaboration_platform.ex`.
2.  **Open IEx (Interactive Elixir):**  Run `iex collaboration_platform.ex` in your terminal. This will compile and load the code.
3.  **Follow the Example Usage:**  Uncomment the lines under "Example Usage" one by one, or copy and paste them into the IEx prompt.  This will demonstrate how to create researchers, projects, and associate them.  Remember to start the `CollaborationPlatform` server first!

This example provides a solid foundation for a more complex research collaboration platform in Elixir. You can extend it with features like:

*   Authentication and Authorization
*   Real-time collaboration (using Phoenix Channels)
*   Database integration (using Ecto)
*   More sophisticated project management features
*   Search capabilities
*   File storage and sharing

Remember that this is a simplified example to illustrate the basic principles. A real-world collaboration platform would require a much more comprehensive design and implementation.