defmodule CljElixir.Compiler do
  @moduledoc """
  Orchestrates the CljElixir compilation pipeline.

  Chains: Reader -> Analyzer -> Transformer -> Elixir compilation.

  The pipeline:

  1. **Reader** (`CljElixir.Reader`) - Parses source text into CljElixir AST
     (s-expression forms represented as Elixir terms).
  2. **Analyzer** (`CljElixir.Analyzer`) - Validates the AST, checking special form
     arity, map literal structure, recur position, etc.
  3. **Transformer** (`CljElixir.Transformer`) - Converts CljElixir AST into Elixir
     AST (`{operation, metadata, arguments}` tuples).
  4. **Elixir Compiler** - `Code.eval_quoted/3` or `Code.compile_quoted/2` handles
     macro expansion, protocol consolidation, and BEAM bytecode generation.
  """

  @doc """
  Compile a CljElixir source string to Elixir AST.

  Runs the full pipeline: read -> analyze -> transform.

  Returns `{:ok, elixir_ast}` on success, or `{:error, diagnostics}` on failure.

  ## Options

    * `:file` - the source file path for error reporting (default: `"nofile"`)
  """
  @spec compile_string(String.t(), keyword()) :: {:ok, term()} | {:error, list()}
  def compile_string(source, opts \\ []) do
    file = opts[:file] || "nofile"

    with {:ok, forms} <- read(source, file),
         {:ok, forms} <- analyze(forms, opts),
         {:ok, elixir_ast} <- transform(forms, opts) do
      {:ok, elixir_ast}
    end
  end

  @doc """
  Compile a `.clje` file to Elixir AST.

  Reads the file from disk and delegates to `compile_string/2` with the
  `:file` option set automatically.

  Returns `{:ok, elixir_ast}` on success, or `{:error, diagnostics}` on failure.
  Raises `File.Error` if the file cannot be read.
  """
  @spec compile_file(Path.t(), keyword()) :: {:ok, term()} | {:error, list()}
  def compile_file(path, opts \\ []) do
    case File.read(path) do
      {:ok, source} ->
        compile_string(source, Keyword.put(opts, :file, path))

      {:error, reason} ->
        {:error,
         [
           %{
             severity: :error,
             message: "could not read file #{path}: #{:file.format_error(reason)}",
             file: path,
             line: 0,
             col: 0
           }
         ]}
    end
  end

  @doc """
  Compile and evaluate a CljElixir source string.

  Compiles the source to Elixir AST and evaluates it via `Code.eval_quoted/3`.

  Returns `{:ok, result, bindings}` on success, or `{:error, diagnostics}` on failure.

  ## Options

    * `:file` - the source file path for error reporting (default: `"nofile"`)
    * `:bindings` - variable bindings for evaluation (default: `[]`)
    * `:env` - the macro environment for evaluation
  """
  @spec eval_string(String.t(), keyword()) :: {:ok, term(), keyword()} | {:error, list()}
  def eval_string(source, opts \\ []) do
    with {:ok, ast} <- compile_string(source, opts) do
      try do
        bindings = opts[:bindings] || []
        env_opts = build_eval_opts(opts)
        {result, new_bindings} = Code.eval_quoted(ast, bindings, env_opts)
        {:ok, result, new_bindings}
      rescue
        e ->
          file = opts[:file] || "nofile"

          {:error,
           [
             %{
               severity: :error,
               message: format_eval_error(e),
               file: file,
               line: extract_line(e),
               col: 0
             }
           ]}
      end
    end
  end

  @doc """
  Compile and evaluate a `.clje` file.

  Reads the file from disk and delegates to `eval_string/2`.

  Returns `{:ok, result, bindings}` on success, or `{:error, diagnostics}` on failure.
  Raises `File.Error` if the file cannot be read.
  """
  @spec eval_file(Path.t(), keyword()) :: {:ok, term(), keyword()} | {:error, list()}
  def eval_file(path, opts \\ []) do
    case File.read(path) do
      {:ok, source} ->
        eval_string(source, Keyword.put(opts, :file, path))

      {:error, reason} ->
        {:error,
         [
           %{
             severity: :error,
             message: "could not read file #{path}: #{:file.format_error(reason)}",
             file: path,
             line: 0,
             col: 0
           }
         ]}
    end
  end

  @doc """
  Compile a CljElixir source string to BEAM modules and write .beam files.

  Compiles the source to Elixir AST and then uses `Code.compile_quoted/2` to
  produce BEAM bytecode modules.

  Returns `{:ok, [{module, binary}]}` on success, or `{:error, diagnostics}` on failure.

  ## Options

    * `:file` - the source file path for error reporting (default: `"nofile"`)
  """
  @spec compile_to_beam(String.t(), keyword()) ::
          {:ok, [{module(), binary()}]} | {:error, list()}
  def compile_to_beam(source, opts \\ []) do
    with {:ok, ast} <- compile_string(source, opts) do
      try do
        file = opts[:file] || "nofile"
        modules = Code.compile_quoted(ast, file)
        {:ok, modules}
      rescue
        e ->
          file = opts[:file] || "nofile"

          {:error,
           [
             %{
               severity: :error,
               message: "BEAM compilation failed: #{format_eval_error(e)}",
               file: file,
               line: extract_line(e),
               col: 0
             }
           ]}
      end
    end
  end

  @doc """
  Compile a `.clje` file to BEAM modules and write .beam files to the given
  output directory.

  Returns `{:ok, [{module, binary}]}` on success, or `{:error, diagnostics}` on failure.

  ## Options

    * `:output_dir` - directory to write .beam files (default: does not write)
  """
  @spec compile_file_to_beam(Path.t(), keyword()) ::
          {:ok, [{module(), binary()}]} | {:error, list()}
  def compile_file_to_beam(path, opts \\ []) do
    case File.read(path) do
      {:ok, source} ->
        opts = Keyword.put(opts, :file, path)

        with {:ok, modules} <- compile_to_beam(source, opts) do
          case opts[:output_dir] do
            nil ->
              {:ok, modules}

            output_dir ->
              write_beam_files(modules, output_dir)
          end
        end

      {:error, reason} ->
        {:error,
         [
           %{
             severity: :error,
             message: "could not read file #{path}: #{:file.format_error(reason)}",
             file: path,
             line: 0,
             col: 0
           }
         ]}
    end
  end

  # ---------------------------------------------------------------------------
  # Private helpers
  # ---------------------------------------------------------------------------

  defp read(source, file) do
    case CljElixir.Reader.read_string(source) do
      {:ok, forms} ->
        {:ok, forms}

      {:error, reason} when is_binary(reason) ->
        {:error,
         [%{severity: :error, message: "read error: #{reason}", file: file, line: 0, col: 0}]}

      {:error, reason} ->
        {:error,
         [
           %{
             severity: :error,
             message: "read error: #{inspect(reason)}",
             file: file,
             line: 0,
             col: 0
           }
         ]}
    end
  end

  defp analyze(forms, _opts) do
    case CljElixir.Analyzer.analyze(forms) do
      {:ok, analyzed_forms} ->
        {:ok, analyzed_forms}

      {:error, diagnostics} when is_list(diagnostics) ->
        {:error, diagnostics}

      {:error, reason} ->
        {:error,
         [%{severity: :error, message: "analysis error: #{inspect(reason)}", line: 0, col: 0}]}
    end
  end

  defp transform(forms, opts) do
    try do
      ctx =
        if opts[:vector_as_list] do
          %CljElixir.Transformer.Context{vector_as_list: true}
        else
          %CljElixir.Transformer.Context{}
        end

      elixir_ast = CljElixir.Transformer.transform(forms, ctx)
      {:ok, elixir_ast}
    rescue
      e ->
        {:error,
         [
           %{
             severity: :error,
             message: "transform error: #{format_eval_error(e)}",
             line: 0,
             col: 0
           }
         ]}
    end
  end

  defp build_eval_opts(opts) do
    eval_opts = [file: opts[:file] || "nofile"]

    case opts[:env] do
      nil -> eval_opts
      env -> Keyword.put(eval_opts, :env, env)
    end
  end

  defp format_eval_error(%{__struct__: struct} = e) when is_atom(struct) do
    Exception.message(e)
  rescue
    _ -> inspect(e)
  end

  defp format_eval_error(e), do: inspect(e)

  defp extract_line(%{line: line}) when is_integer(line), do: line
  defp extract_line(_), do: 0

  defp write_beam_files(modules, output_dir) do
    File.mkdir_p!(output_dir)

    Enum.each(modules, fn {module, binary} ->
      beam_path = Path.join(output_dir, "#{module}.beam")
      File.write!(beam_path, binary)
    end)

    {:ok, modules}
  end
end