defmodule Mix.Tasks.Ab.Test do
  @moduledoc """
  Mix task that compiles Elixir files, extracts modules, and runs AB.property_test on their exported functions.

  ## Usage

      mix ab.test path/to/file.ex
      mix ab.test path/to/directory

  ## Examples

      # Test a single file
      mix ab.test lib/my_module.ex

      # Test all .ex files in a directory recursively
      mix ab.test lib/

      # Test with verbose output
      mix ab.test lib/my_module.ex --verbose

      # Show only failures in a structured format
      mix ab.test lib/my_module.ex --failures-only

      # Skip functions without typespecs (soft mode)
      mix ab.test lib/my_module.ex --soft

      # Test all files in a directory with soft mode
      mix ab.test lib/ --soft

  ## Options

  - `--verbose`, `-v`: Enable verbose output showing input/output for each test
  - `--failures-only`, `-f`: Show only failed tests in a structured format with:
    - Function name
    - Why it failed
    - Incorrect typespec
    - Expected typespec
    - File path and line number
  - `--soft`, `-s`: Skip functions without typespecs instead of erroring out

  This task will:
  1. Compile the specified Elixir file(s) or all .ex files in a directory (recursively)
  2. Extract the module from each compiled file
  3. Find all exported functions with typespecs
  4. Run AB.property_test on each function
  5. Error out if functions without typespecs are found (unless --soft flag is used)

  When processing directories, the task will:
  - Recursively find all .ex files
  - Skip hidden directories (starting with .)
  - Skip common build directories (_build, deps, node_modules)
  """

  use Mix.Task

  @shortdoc "Compiles Elixir files and runs AB.property_test on their exported functions"

  @impl Mix.Task
  def run(args) do
    # Start ExUnit
    ExUnit.start(autorun: false)

    {opts, paths} = parse_args(args)

    if paths == [] do
      Mix.shell().error(
        "No file or directory specified. Usage: mix ab.test <file.ex> or <directory>"
      )

      System.halt(1)
    end

    # Expand paths to individual files
    all_files = expand_paths_to_files(paths)

    if all_files == [] do
      Mix.shell().error("No .ex files found in the specified paths")
      System.halt(1)
    end

    Mix.shell().info("Found #{length(all_files)} .ex files to process")

    Enum.each(all_files, fn file ->
      test_file(file, opts)
    end)
  end

  defp parse_args(args) do
    {opts, files, _} =
      OptionParser.parse(args,
        switches: [verbose: :boolean, failures_only: :boolean, soft: :boolean],
        aliases: [v: :verbose, f: :failures_only, s: :soft]
      )

    {opts, files}
  end

  defp test_file(file_path, opts) do
    Mix.shell().info("Testing file: #{file_path}")

    case compile_and_extract_module(file_path) do
      {:ok, module} ->
        run_property_tests(module, opts, file_path)

      {:error, reason} ->
        Mix.shell().error("Failed to compile file: #{reason}")
        System.halt(1)
    end
  end

  defp compile_and_extract_module(file_path) do
    # Extract module name from the file first
    case extract_module_from_file(file_path) do
      {:ok, module} ->
        # Now compile the file using elixirc to preserve typespecs
        compile_with_elixirc(file_path, module)

      error ->
        error
    end
  end

  defp compile_with_elixirc(file_path, module) do
    # Use Code.compile_file which has access to the current Mix environment
    # This includes all dependencies that are already loaded
    case Code.compile_file(file_path) do
      [{^module, _}] ->
        {:ok, module}

      [{^module, _}, _] ->
        {:ok, module}

      [] ->
        {:error, "No module compiled"}

      _ ->
        {:error, "Unexpected compilation result"}
    end
  end

  defp extract_module_from_file(file_path) do
    case File.read(file_path) do
      {:ok, content} ->
        # Parse the AST to extract the module name
        case Code.string_to_quoted(content) do
          {:ok, ast} ->
            module_name = extract_module_name_from_ast(ast)

            if module_name do
              {:ok, module_name}
            else
              {:error, "Could not find module name in file"}
            end

          {:error, reason} ->
            {:error, "Failed to parse file: #{inspect(reason)}"}
        end

      {:error, reason} ->
        {:error, "Failed to read file: #{reason}"}
    end
  end

  defp extract_module_name_from_ast({:defmodule, _, [module_alias | _]}) do
    case module_alias do
      {:__aliases__, _, parts} ->
        Module.concat(parts)

      name when is_atom(name) ->
        name

      _ ->
        nil
    end
  end

  defp extract_module_name_from_ast({:__block__, _, statements}) do
    Enum.find_value(statements, fn statement ->
      extract_module_name_from_ast(statement)
    end)
  end

  defp extract_module_name_from_ast(_), do: nil

  defp run_property_tests(module, opts, file_path) do
    Mix.shell().info("Running property tests for module: #{module}")

    # The module should already be loaded from compilation
    run_tests_for_module(module, opts, file_path)
  end

  defp run_tests_for_module(module, opts, file_path) do
    soft_mode = Keyword.get(opts, :soft, false)

    # Get all exported functions with typespecs
    functions_with_specs = get_functions_with_specs(module)

    # Get all exported functions
    all_exported_functions = module.__info__(:functions)

    # Find functions without specs
    functions_without_specs =
      all_exported_functions
      |> Enum.reject(fn {name, arity} ->
        {name, arity} in functions_with_specs
      end)

    # Handle functions without specs
    if functions_without_specs != [] do
      if soft_mode do
        Mix.shell().info(
          "Warning: Found #{length(functions_without_specs)} functions without typespecs (skipping): #{format_function_list(functions_without_specs)}"
        )
      else
        Mix.shell().error(
          "Error: Found #{length(functions_without_specs)} functions without typespecs:"
        )

        Enum.each(functions_without_specs, fn {name, arity} ->
          Mix.shell().error(
            "  - #{String.replace_leading(to_string(module), "Elixir.", "")}.#{name}/#{arity}"
          )
        end)

        Mix.shell().error("Use --soft flag to skip functions without typespecs")
        System.halt(1)
      end
    end

    # Run tests for functions with specs
    case functions_with_specs do
      [] ->
        Mix.shell().info("No functions with typespecs found in #{module}")

      functions ->
        Mix.shell().info("Found #{length(functions)} functions with typespecs")
        run_tests_for_functions(module, functions, opts, file_path)
    end
  end

  defp get_functions_with_specs(module) do
    case Code.Typespec.fetch_specs(module) do
      {:ok, specs} ->
        exported_functions = module.__info__(:functions)

        specs
        |> Enum.map(fn {{function_name, arity}, _} -> {function_name, arity} end)
        |> Enum.filter(fn {function_name, arity} ->
          {function_name, arity} in exported_functions
        end)

      _ ->
        []
    end
  end

  defp run_tests_for_functions(module, functions, opts, file_path) do
    verbose = Keyword.get(opts, :verbose, false)
    failures_only = Keyword.get(opts, :failures_only, false)

    if not failures_only do
      Mix.shell().info("\n=== Running property tests for #{length(functions)} functions ===")
    end

    results =
      Enum.map(functions, fn {function_name, _arity} ->
        if not failures_only do
          Mix.shell().info("Testing #{module}.#{function_name}")
        end

        run_single_property_test(module, function_name, verbose, failures_only)
      end)

    # Summary
    passed = Enum.count(results, &(&1 == :ok))
    failed = length(results) - passed

    if failures_only do
      # Only show failures in the specified format
      failures = Enum.filter(results, &(&1 != :ok))

      if failures != [] do
        Mix.shell().info("\n=== Failures ===")

        Enum.with_index(failures, 1)
        |> Enum.each(fn {failure, index} ->
          format_failure_output(module, failure, index, file_path)
        end)
      else
        Mix.shell().info("All tests passed!")
      end
    else
      Mix.shell().info("\n=== Summary ===")
      Mix.shell().info("✓ Passed: #{passed}")
      Mix.shell().info("✗ Failed: #{failed}")
    end

    if failed > 0 do
      System.halt(1)
    end
  end

  defp run_single_property_test(module, function_name, verbose, failures_only) do
    # Run the property test with details capture
    case AB.run_property_test_with_details(module, function_name, verbose: verbose) do
      {:ok, count} ->
        if not failures_only do
          Mix.shell().info(
            "  ✓ #{module}.#{function_name} passed all property tests (#{count} runs)"
          )
        end

        :ok

      {:error, details} ->
        if not failures_only do
          Mix.shell().error("  ✗ #{module}.#{function_name} failed property test")
          Mix.shell().error("    #{details.reason}")
        end

        {:error, details}
    end
  end

  defp format_failure_output(
         _module,
         {:error, details},
         index,
         file_path
       ) do
    function_name = details.function_name
    module = details.module
    arity = get_arity_for_function(module, function_name)

    # Get typespec correction suggestion if we have the actual values
    suggestion =
      if details.inputs && details.result && details.mismatch_type do
        AB.suggest_typespec_correction(
          module,
          function_name,
          details.inputs,
          details.result,
          details.mismatch_type
        )
      else
        nil
      end

    # Get line number for the function - try both approaches
    line_number =
      case get_line_number_for_function(module, function_name) do
        0 -> get_line_number_from_source(file_path, function_name)
        line -> line
      end

    # Format the failure output - remove Elixir. prefix if present
    module_name =
      if to_string(module) |> String.starts_with?("Elixir.") do
        to_string(module) |> String.replace_leading("Elixir.", "")
      else
        to_string(module)
      end

    Mix.shell().info("#{index}. #{module_name}.#{function_name}/#{arity}")
    Mix.shell().info("   - Why it failed: #{details.reason}")

    # Show the actual inputs and result if available
    if details.inputs do
      Mix.shell().info("   - Generated input: #{inspect(details.inputs)}")
    end

    if details.result do
      Mix.shell().info("   - Actual result: #{inspect(details.result)}")
    end

    # Show typespec suggestion
    case suggestion do
      nil ->
        # No suggestion available
        :ok

      {:error, error_msg} ->
        Mix.shell().info("   - Could not analyze typespec: #{error_msg}")

      %{old_spec: old_spec, new_spec: new_spec, reason: _suggestion_reason} ->
        Mix.shell().info("   - Incorrect typespec: #{old_spec}")
        Mix.shell().info("   - Suggested typespec: #{new_spec}")
    end

    Mix.shell().info("   - #{file_path}:#{line_number}")
    Mix.shell().info("")
  end

  defp get_line_number_for_function(module, function_name) do
    # Try to get line number from the function's metadata
    case Code.Typespec.fetch_specs(module) do
      {:ok, specs} ->
        case Enum.find(specs, fn {{name, _arity}, _} -> name == function_name end) do
          {{_name, _arity}, {_spec, context, metadata}} ->
            # Try to get line number from context or metadata
            cond do
              # Check if context has line information
              is_list(context) and Keyword.has_key?(context, :line) ->
                Keyword.get(context, :line, 0)

              # Check if metadata has line information
              is_list(metadata) and Keyword.has_key?(metadata, :line) ->
                Keyword.get(metadata, :line, 0)

              # Look for line information in the metadata list
              is_list(metadata) ->
                case Enum.find(metadata, fn {key, _} -> key == :line end) do
                  {:line, line} -> line
                  _ -> 0
                end

              true ->
                0
            end

          _ ->
            0
        end

      _ ->
        0
    end
  end

  defp get_line_number_from_source(file_path, function_name) do
    # Try to find the line number by parsing the source file
    case File.read(file_path) do
      {:ok, content} ->
        lines = String.split(content, "\n")

        # Look for the function definition
        case Enum.with_index(lines, 1)
             |> Enum.find({nil, 0}, fn {line, _index} ->
               # Look for function definition patterns
               String.contains?(line, "def #{function_name}") or
                 String.contains?(line, "def #{function_name}(") or
                 String.contains?(line, "def #{function_name} ")
             end) do
          {_line, line_number} -> line_number
          _ -> 0
        end

      {:error, _} ->
        0
    end
  end

  defp get_arity_for_function(module, function_name) do
    # Get arity from the module's exported functions
    case module.__info__(:functions) do
      functions when is_list(functions) ->
        case Enum.find(functions, fn {name, _arity} -> name == function_name end) do
          {_name, arity} -> arity
          _ -> 0
        end

      _ ->
        0
    end
  end

  defp format_function_list(functions) do
    functions
    |> Enum.map(fn {name, arity} -> "#{name}/#{arity}" end)
    |> Enum.join(", ")
  end

  defp expand_paths_to_files(paths) do
    paths
    |> Enum.flat_map(fn path ->
      if File.dir?(path) do
        find_ex_files_recursively(path)
      else
        if String.ends_with?(path, ".ex") do
          [path]
        else
          []
        end
      end
    end)
    |> Enum.uniq()
  end

  defp find_ex_files_recursively(directory) do
    case File.ls(directory) do
      {:ok, entries} ->
        entries
        |> Enum.flat_map(fn entry ->
          full_path = Path.join(directory, entry)

          cond do
            File.dir?(full_path) ->
              # Skip hidden directories and common build directories
              if String.starts_with?(entry, ".") or entry in ["_build", "deps", "node_modules"] do
                []
              else
                find_ex_files_recursively(full_path)
              end

            String.ends_with?(entry, ".ex") ->
              [full_path]

            true ->
              []
          end
        end)

      {:error, _reason} ->
        Mix.shell().error("Could not read directory: #{directory}")
        []
    end
  end
end