defmodule Mix.Tasks.Raxol.InstallHooks do
  @moduledoc """
  Install Git hooks for the Raxol pre-commit system.

  This task installs the pre-commit hook that automatically runs
  `mix raxol.pre_commit` before each commit.

  ## Usage

      mix raxol.install_hooks
      
  ## Options

    * `--force` - Overwrite existing hooks without asking
    * `--backup` - Create backup of existing hooks
    * `--check` - Only check if hooks are installed (dry run)
    
  ## Examples

      # Install hooks (interactive if hooks exist)
      mix raxol.install_hooks
      
      # Force overwrite existing hooks
      mix raxol.install_hooks --force
      
      # Create backup of existing hooks
      mix raxol.install_hooks --backup
      
      # Check if hooks are installed
      mix raxol.install_hooks --check
  """

  use Mix.Task

  @shortdoc "Install Git pre-commit hooks"

  @pre_commit_hook """
  #!/bin/sh
  # Raxol pre-commit hook
  # Generated by mix raxol.install_hooks

  # Allow bypassing the hook with RAXOL_SKIP_CHECKS environment variable
  if [ "$RAXOL_SKIP_CHECKS" = "true" ] || [ "$RAXOL_SKIP_CHECKS" = "1" ]; then
    echo "Skipping Raxol pre-commit checks (RAXOL_SKIP_CHECKS is set)"
    exit 0
  fi

  # Check if we're in a rebase
  if [ -d "$(git rev-parse --git-dir)/rebase-merge" ] || [ -d "$(git rev-parse --git-dir)/rebase-apply" ]; then
    echo "Skipping pre-commit checks during rebase"
    exit 0
  fi

  # Run the pre-commit checks
  echo "Running Raxol pre-commit checks..."
  mix raxol.pre_commit

  # Capture the exit code
  EXIT_CODE=$?

  # Exit with the same code
  if [ $EXIT_CODE -ne 0 ]; then
    echo ""
    echo "Pre-commit checks failed. You can bypass with:"
    echo "  git commit --no-verify"
    echo "  RAXOL_SKIP_CHECKS=true git commit"
  fi

  exit $EXIT_CODE
  """

  @impl Mix.Task
  def run(args) do
    {opts, _, _} =
      OptionParser.parse(args,
        switches: [
          force: :boolean,
          backup: :boolean,
          check: :boolean
        ]
      )

    git_dir = get_git_directory()
    hooks_dir = Path.join(git_dir, "hooks")
    pre_commit_path = Path.join(hooks_dir, "pre-commit")

    if opts[:check] do
      check_hook_status(pre_commit_path)
    else
      install_hook(pre_commit_path, opts)
    end
  end

  defp get_git_directory do
    case System.cmd("git", ["rev-parse", "--git-dir"], stderr_to_stdout: true) do
      {output, 0} ->
        String.trim(output)

      _ ->
        Mix.raise(
          "Not in a Git repository. Please run this command from a Git repository."
        )
    end
  end

  defp check_hook_status(hook_path) do
    case File.exists?(hook_path) do
      true ->
        case File.read!(hook_path) do
          content when content == @pre_commit_hook ->
            IO.puts("✅ Raxol pre-commit hook is installed and up to date")
            {:ok, :current}

          content ->
            case String.contains?(content, "mix raxol.pre_commit") do
              true ->
                IO.puts("⚠️  Raxol pre-commit hook is installed but outdated")
                IO.puts("    Run 'mix raxol.install_hooks' to update")
                {:ok, :outdated}

              false ->
                IO.puts("⚠️  A different pre-commit hook is installed")

                IO.puts(
                  "    Run 'mix raxol.install_hooks --backup' to install Raxol hook"
                )

                {:ok, :different}
            end
        end

      false ->
        IO.puts("❌ No pre-commit hook installed")
        IO.puts("    Run 'mix raxol.install_hooks' to install")
        {:ok, :missing}
    end
  end

  defp install_hook(hook_path, opts) do
    # Check if hook already exists
    case File.exists?(hook_path) do
      true ->
        handle_existing_hook(hook_path, opts)

      false ->
        write_hook(hook_path)
    end
  end

  defp handle_existing_hook(hook_path, opts) do
    existing_content = File.read!(hook_path)

    cond do
      existing_content == @pre_commit_hook ->
        IO.puts("✅ Raxol pre-commit hook is already installed and up to date")
        {:ok, :already_installed}

      opts[:force] ->
        maybe_backup(hook_path, opts)
        write_hook(hook_path)

      String.contains?(existing_content, "mix raxol.pre_commit") ->
        IO.puts("An older version of the Raxol pre-commit hook is installed.")

        case prompt_user("Update to the latest version?") do
          true ->
            maybe_backup(hook_path, opts)
            write_hook(hook_path)

          false ->
            IO.puts("Hook installation cancelled")
            {:ok, :cancelled}
        end

      true ->
        IO.puts("A different pre-commit hook already exists.")
        IO.puts("Content preview:")
        IO.puts(String.slice(existing_content, 0, 200) <> "...")

        case prompt_user("Replace with Raxol pre-commit hook?") do
          true ->
            maybe_backup(hook_path, opts)
            write_hook(hook_path)

          false ->
            IO.puts("Hook installation cancelled")

            IO.puts(
              "You can manually integrate Raxol by adding 'mix raxol.pre_commit' to your existing hook"
            )

            {:ok, :cancelled}
        end
    end
  end

  defp maybe_backup(hook_path, opts) do
    case opts[:backup] do
      true ->
        backup_path = "#{hook_path}.backup.#{timestamp()}"
        File.copy!(hook_path, backup_path)
        IO.puts("📦 Created backup: #{backup_path}")

      _ ->
        :ok
    end
  end

  defp write_hook(hook_path) do
    # Ensure hooks directory exists
    hook_path |> Path.dirname() |> File.mkdir_p!()

    # Write the hook file
    File.write!(hook_path, @pre_commit_hook)

    # Make it executable
    case System.cmd("chmod", ["+x", hook_path]) do
      {_, 0} ->
        IO.puts("✅ Successfully installed Raxol pre-commit hook")
        IO.puts("    Location: #{hook_path}")
        IO.puts("")
        IO.puts("The hook will run automatically before each commit.")
        IO.puts("To bypass: git commit --no-verify")
        {:ok, :installed}

      _ ->
        Mix.raise(
          "Failed to make hook executable. Please run: chmod +x #{hook_path}"
        )
    end
  end

  defp prompt_user(question) do
    case IO.gets("#{question} [y/N]: ") do
      :eof ->
        false

      response when is_binary(response) ->
        response
        |> String.trim()
        |> String.downcase()
        |> then(&(&1 in ["y", "yes"]))

      _ ->
        false
    end
  end

  defp timestamp do
    {{year, month, day}, {hour, minute, second}} = :calendar.local_time()
    "#{year}#{pad(month)}#{pad(day)}_#{pad(hour)}#{pad(minute)}#{pad(second)}"
  end

  defp pad(num), do: num |> Integer.to_string() |> String.pad_leading(2, "0")
end