defmodule Odinsea.Scripting.Manager do
  @moduledoc """
  Base script manager for loading and caching game scripts.
  
  This module provides functionality for:
  - Loading script files from disk
  - Caching compiled scripts in ETS
  - Hot-reloading scripts without server restart
  - Resolving script modules by name
  
  ## Script Loading
  
  Scripts are loaded from the `scripts/` directory with the following structure:
  - `scripts/npc/` - NPC conversation scripts (857 files)
  - `scripts/portal/` - Portal scripts (700 files)
  - `scripts/event/` - Event scripts (95 files)
  - `scripts/quest/` - Quest scripts (445 files)
  - `scripts/reactor/` - Reactor scripts (272 files)
  
  ## Hot Reload
  
  When `script_reload` is enabled in configuration, scripts are reloaded
  from disk on each invocation (useful for development).
  
  ## Script Compilation
  
  Scripts can be implemented as:
  1. Elixir modules compiled at build time
  2. Elixir modules compiled dynamically at runtime (Code.eval_string)
  3. JavaScript executed via QuickJS (future enhancement)
  4. Lua executed via luerl (future enhancement)
  
  ## Configuration
  
      config :odinsea, Odinsea.Scripting,
        script_reload: true,  # Enable hot-reload in development
        scripts_path: "priv/scripts"  # Path to script files
  """

  use GenServer
  require Logger

  alias Odinsea.Scripting.{Behavior, PlayerAPI}

  # ETS table names for caching
  @script_cache :script_cache
  @script_timestamps :script_timestamps

  # Script types
  @script_types [:npc, :portal, :event, :quest, :reactor]

  # ============================================================================
  # Types
  # ============================================================================

  @type script_type :: :npc | :portal | :event | :quest | :reactor
  @type script_module :: module()
  @type script_result :: {:ok, script_module()} | {:error, term()}

  # ============================================================================
  # Client API
  # ============================================================================

  @doc """
  Starts the script manager.
  """
  @spec start_link(keyword()) :: GenServer.on_start()
  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @doc """
  Loads all scripts from the scripts directory.
  
  ## Parameters
    - `type` - Optional script type to load (nil loads all)
  
  ## Returns
    - `{:ok, count}` - Number of scripts loaded
    - `{:error, reason}` - Loading failed
  """
  @spec load_all(script_type() | nil) :: {:ok, integer()} | {:error, term()}
  def load_all(type \\ nil) do
    GenServer.call(__MODULE__, {:load_all, type})
  end

  @doc """
  Loads a single script file.
  
  ## Parameters
    - `path` - Relative path within scripts directory (e.g., "npc/1002001.js")
  
  ## Returns
    - `{:ok, module}` - Script loaded successfully
    - `{:error, reason}` - Loading failed
  """
  @spec load_script(String.t()) :: script_result()
  def load_script(path) do
    GenServer.call(__MODULE__, {:load_script, path})
  end

  @doc """
  Gets a cached script module.
  
  ## Parameters
    - `type` - Script type (:npc, :portal, etc.)
    - `name` - Script name (e.g., "1002001", "08_xmas_st")
  
  ## Returns
    - `{:ok, module}` - Script found
    - `{:error, :not_found}` - Script not found
  """
  @spec get_script(script_type(), String.t()) :: script_result()
  def get_script(type, name) do
    case :ets.lookup(@script_cache, {type, name}) do
      [{_, module}] -> 
        if script_reload?() do
          # Reload if hot-reload is enabled
          reload_script(type, name)
        else
          {:ok, module}
        end
      [] -> 
        # Try to load from file
        load_and_cache(type, name)
    end
  end

  @doc """
  Reloads a script from disk.
  
  ## Parameters
    - `type` - Script type
    - `name` - Script name
  
  ## Returns
    - `{:ok, module}` - Script reloaded successfully
    - `{:error, reason}` - Reload failed
  """
  @spec reload_script(script_type(), String.t()) :: script_result()
  def reload_script(type, name) do
    GenServer.call(__MODULE__, {:reload_script, type, name})
  end

  @doc """
  Clears all cached scripts.
  """
  @spec clear_cache() :: :ok
  def clear_cache() do
    GenServer.call(__MODULE__, :clear_cache)
  end

  @doc """
  Returns the file path for a script.
  
  ## Parameters
    - `type` - Script type
    - `name` - Script name
  
  ## Returns
    - File path as string
  """
  @spec script_path(script_type(), String.t()) :: String.t()
  def script_path(type, name) do
    base = scripts_path()
    ext = script_extension()
    Path.join([base, to_string(type), "#{name}#{ext}"])
  end

  @doc """
  Checks if a script file exists.
  
  ## Parameters
    - `type` - Script type
    - `name` - Script name
  
  ## Returns
    - `true` - Script exists
    - `false` - Script does not exist
  """
  @spec script_exists?(script_type(), String.t()) :: boolean()
  def script_exists?(type, name) do
    script_path(type, name)
    |> File.exists?()
  end

  @doc """
  Lists all available scripts of a given type.
  
  ## Parameters
    - `type` - Script type
  
  ## Returns
    - List of script names
  """
  @spec list_scripts(script_type()) :: [String.t()]
  def list_scripts(type) do
    base = Path.join(scripts_path(), to_string(type))
    ext = script_extension()
    
    case File.ls(base) do
      {:ok, files} ->
        files
        |> Enum.filter(&String.ends_with?(&1, ext))
        |> Enum.map(&String.replace_suffix(&1, ext, ""))
      {:error, _} ->
        []
    end
  end

  @doc """
  Compiles a script file into an Elixir module.
  
  This is a stub implementation that can be extended to support:
  - JavaScript via QuickJS
  - Lua via luerl
  - Direct Elixir modules
  
  ## Parameters
    - `source` - Script source code
    - `module_name` - Name for the compiled module
  
  ## Returns
    - `{:ok, module}` - Compilation successful
    - `{:error, reason}` - Compilation failed
  """
  @spec compile_script(String.t(), module()) :: script_result()
  def compile_script(source, module_name) do
    # Stub implementation - creates a minimal module
    # In production, this would parse JavaScript/Lua and generate Elixir code
    # or compile to bytecode for a JS/Lua runtime
    
    try do
      # For now, create a stub module
      # This would be replaced with actual JS/Lua compilation
      ast = quote do
        defmodule unquote(module_name) do
          @behaviour Odinsea.Scripting.Behavior
          
          # Stub implementations
          def start(_api), do: :ok
          def action(_api, _mode, _type, _selection), do: :ok
          def enter(_api), do: :ok
          def act(_api), do: :ok
          def init(_em), do: :ok
          def setup(_em, _args), do: :ok
        end
      end
      
      Code.eval_quoted(ast)
      {:ok, module_name}
    rescue
      e -> 
        Logger.error("Script compilation failed: #{inspect(e)}")
        {:error, :compilation_failed}
    end
  end

  # ============================================================================
  # Configuration Helpers
  # ============================================================================

  @doc """
  Returns the base path for scripts.
  """
  @spec scripts_path() :: String.t()
  def scripts_path() do
    Application.get_env(:odinsea, __MODULE__, [])
    |> Keyword.get(:scripts_path, "priv/scripts")
    |> Path.expand()
  end

  @doc """
  Returns whether hot-reload is enabled.
  """
  @spec script_reload?() :: boolean()
  def script_reload?() do
    Application.get_env(:odinsea, __MODULE__, [])
    |> Keyword.get(:script_reload, false)
  end

  @doc """
  Returns the script file extension.
  """
  @spec script_extension() :: String.t()
  def script_extension() do
    # Could be .js for JavaScript, .lua for Lua, .ex for Elixir
    Application.get_env(:odinsea, __MODULE__, [])
    |> Keyword.get(:script_extension, ".ex")
  end

  # ============================================================================
  # Server Callbacks
  # ============================================================================

  @impl true
  def init(_opts) do
    # Create ETS tables for caching
    :ets.new(@script_cache, [:named_table, :set, :public, 
             read_concurrency: true, write_concurrency: true])
    :ets.new(@script_timestamps, [:named_table, :set, :public,
             read_concurrency: true, write_concurrency: true])
    
    Logger.info("Script Manager initialized")
    
    {:ok, %{loaded: 0}}
  end

  @impl true
  def handle_call({:load_all, type}, _from, state) do
    types = if type, do: [type], else: @script_types
    
    count = Enum.reduce(types, 0, fn script_type, acc ->
      scripts = list_scripts(script_type)
      loaded = Enum.count(scripts, fn name ->
        case load_and_cache(script_type, name) do
          {:ok, _} -> true
          {:error, _} -> false
        end
      end)
      acc + loaded
    end)
    
    Logger.info("Loaded #{count} scripts")
    {:reply, {:ok, count}, %{state | loaded: count}}
  end

  @impl true
  def handle_call({:load_script, path}, _from, state) do
    result = do_load_script(path)
    {:reply, result, state}
  end

  @impl true
  def handle_call({:reload_script, type, name}, _from, state) do
    # Remove from cache
    :ets.delete(@script_cache, {type, name})
    :ets.delete(@script_timestamps, {type, name})
    
    # Reload
    result = load_and_cache(type, name)
    {:reply, result, state}
  end

  @impl true
  def handle_call(:clear_cache, _from, state) do
    :ets.delete_all_objects(@script_cache)
    :ets.delete_all_objects(@script_timestamps)
    Logger.info("Script cache cleared")
    {:reply, :ok, %{state | loaded: 0}}
  end

  # ============================================================================
  # Private Functions
  # ============================================================================

  defp load_and_cache(type, name) do
    path = script_path(type, name)
    
    case File.read(path) do
      {:ok, source} ->
        module_name = module_name_for(type, name)
        
        case compile_script(source, module_name) do
          {:ok, module} ->
            :ets.insert(@script_cache, {{type, name}, module})
            :ets.insert(@script_timestamps, {{type, name}, File.stat!(path).mtime})
            {:ok, module}
          
          {:error, reason} ->
            Logger.warning("Failed to compile script #{path}: #{inspect(reason)}")
            {:error, :compilation_failed}
        end
      
      {:error, reason} ->
        Logger.debug("Script not found: #{path}")
        {:error, reason}
    end
  end

  defp do_load_script(path) do
    full_path = Path.join(scripts_path(), path)
    
    case File.read(full_path) do
      {:ok, source} ->
        # Determine type and name from path
        [type_str, filename] = Path.split(path)
        name = Path.rootname(filename)
        type = String.to_existing_atom(type_str)
        module_name = module_name_for(type, name)
        
        compile_script(source, module_name)
      
      {:error, reason} ->
        {:error, reason}
    end
  end

  defp module_name_for(type, name) do
    # Generate a valid Elixir module name
    # e.g., Odinsea.Scripting.NPC.Script_1002001
    type_module = type |> to_string() |> Macro.camelize()
    safe_name = sanitize_module_name(name)
    Module.concat(["Odinsea", "Scripting", type_module, "Script_#{safe_name}"])
  end

  defp sanitize_module_name(name) do
    # Convert script name to valid module name
    name
    |> String.replace(~r/[^a-zA-Z0-9_]/, "_")
    |> String.replace_prefix("", "Script_")
  end
end