defmodule Cmd.Worktrees do
  @behaviour Cmd

  @impl Cmd
  def requires_project?(), do: true

  @impl Cmd
  def spec do
    [
      worktrees: [
        name: "worktrees",
        about: "Manage git worktrees for the current project",
        options: [
          project: Cmd.project_arg()
        ],
        subcommands: [
          list: [
            name: "list",
            about: "List worktrees with branch, merge status, and size"
          ],
          create: [
            name: "create",
            about: "Create a new conversation-scoped worktree",
            options: [
              conversation: [
                value_name: "CONVERSATION_ID",
                long: "--conversation",
                short: "-c",
                help: "Conversation id for worktree naming",
                parser: :string,
                required: true
              ],
              branch: [
                value_name: "BRANCH",
                long: "--branch",
                short: "-b",
                help: "Branch name (default: auto-generated)",
                parser: :string,
                required: false
              ]
            ]
          ],
          delete: [
            name: "delete",
            about: "Remove a conversation worktree",
            options: [
              conversation: [
                value_name: "CONVERSATION_ID",
                long: "--conversation",
                short: "-c",
                help: "Conversation id whose worktree to remove",
                parser: :string,
                required: true
              ]
            ]
          ],
          view: [
            name: "view",
            about: "Show the diff of a conversation worktree from its fork point",
            options: [
              conversation: [
                value_name: "CONVERSATION_ID",
                long: "--conversation",
                short: "-c",
                help: "Conversation id whose worktree diff to view",
                parser: :string,
                required: true
              ]
            ]
          ],
          merge: [
            name: "merge",
            about: "Review, merge, and optionally clean up a conversation worktree",
            options: [
              conversation: [
                value_name: "CONVERSATION_ID",
                long: "--conversation",
                short: "-c",
                help: "Conversation id whose worktree to merge",
                parser: :string,
                required: true
              ]
            ]
          ]
        ]
      ]
    ]
  end

  @impl Cmd
  def run(_opts, [:list], _unknown) do
    with {:ok, project} <- Store.get_project(),
         {:ok, root} <- GitCli.Worktree.project_root(),
         {:ok, entries} <- GitCli.Worktree.list(root) do
      managed =
        Enum.filter(entries, fn entry ->
          GitCli.Worktree.fnord_managed?(project.name, entry.path)
        end)

      if managed == [] do
        UI.info("No fnord-managed worktrees found")
      else
        managed
        |> Enum.map(fn entry ->
          %{
            "Conversation" => Path.basename(entry.path),
            "Branch" => entry.branch || "-",
            "Base" => Map.get(entry, :base_branch) || "-",
            "Status" => format_merge_status(entry.merge_status),
            "Dirty" =>
              if(GitCli.Worktree.has_uncommitted_changes?(entry.path), do: "yes", else: "-"),
            "Size" => format_size(entry.size),
            "Path" => entry.path
          }
        end)
        |> Owl.Table.new(
          padding_x: 1,
          sort_columns: fn a, b -> column_order(a) <= column_order(b) end
        )
        |> UI.puts()

        print_merge_hints()
      end

      :ok
    else
      {:error, :not_a_repo} ->
        UI.error("Not inside a git repository")
        {:error, :not_a_repo}

      {:error, reason} ->
        UI.error("Failed to list worktrees: #{format_reason(reason)}")
        {:error, reason}
    end
  end

  def run(%{conversation: conv_id}, [:view], _unknown) do
    with {:ok, meta} <- resolve_worktree_meta(conv_id),
         {:ok, root} <- resolve_repo_root_for_view(meta.path),
         {:ok, diff} <- GitCli.Worktree.diff_from_fork_point(root, meta.branch, meta.base_branch) do
      if byte_size(diff) > 0 do
        diff
        |> GitCli.Worktree.Review.colorize_diff()
        |> UI.puts()
      else
        UI.info("No changes from fork point")
      end

      :ok
    else
      {:error, :missing_worktree_path} ->
        UI.error("Worktree path does not exist or is inaccessible")
        {:error, :missing_worktree_path}

      {:error, :not_a_repo} ->
        UI.error("Worktree path is not inside a git repository")
        {:error, :not_a_repo}

      {:error, reason} ->
        UI.error("Failed to view worktree diff: #{format_reason(reason)}")
        {:error, reason}
    end
  end

  def run(%{conversation: conversation_id} = opts, [:create], _unknown) do
    with {:ok, project} <- Store.get_project(),
         {:ok, entry} <-
           GitCli.Worktree.create(project.name, conversation_id, Map.get(opts, :branch)) do
      UI.info("Created worktree", entry.path)
      :ok
    else
      {:error, :not_a_repo} ->
        UI.error("Not inside a git repository")
        {:error, :not_a_repo}

      {:error, reason} ->
        UI.error("Failed to create worktree: #{format_reason(reason)}")
        {:error, reason}
    end
  end

  def run(%{conversation: conv_id}, [:delete], _unknown) do
    with {:ok, meta} <- resolve_worktree_meta(conv_id),
         {:ok, root} <- GitCli.Worktree.project_root(),
         :ok <- Cmd.WorktreeLifecycle.warn_if_unmerged(root, meta),
         {:ok, :ok} <- Cmd.WorktreeLifecycle.delete_worktree(root, meta.path) do
      UI.info("Deleted worktree", meta.path)

      case GitCli.Worktree.delete_branch(root, meta.branch) do
        {:ok, :ok} ->
          UI.info("Deleted branch", meta.branch)

        {:error, _} ->
          case GitCli.Worktree.force_delete_branch(root, meta.branch) do
            {:ok, :ok} ->
              UI.info("Force-deleted branch", meta.branch)

            {:error, _} ->
              UI.debug("worktrees", "Branch #{meta.branch} not found (already cleaned up)")
          end
      end

      Cmd.WorktreeLifecycle.clear_worktree_from_conversation(conv_id)
      :ok
    else
      {:error, :cancelled} ->
        UI.info("Worktree deletion cancelled")
        :ok

      {:error, :not_a_repo} ->
        UI.error("Not inside a git repository")
        {:error, :not_a_repo}

      {:error, reason} ->
        UI.error("Failed to delete worktree: #{format_reason(reason)}")
        {:error, reason}
    end
  end

  def run(%{conversation: conv_id}, [:merge], _unknown) do
    with {:ok, meta} <- resolve_worktree_meta(conv_id),
         {:ok, root} <- GitCli.Worktree.project_root() do
      # Copy gitignored/excluded files before the review flow may delete the
      # worktree. Same eager-copy strategy as Cmd.Ask.
      copied_files = copy_ignored_writes_for_conversation(conv_id, meta.path, root)

      case GitCli.Worktree.Review.interactive_review(root, meta, ignored_files: copied_files) do
        {:cleaned_up, _sha, _mode} ->
          Cmd.WorktreeLifecycle.clear_worktree_from_conversation(conv_id)

        _ ->
          :ok
      end
    else
      {:error, :not_a_repo} ->
        UI.error("Not inside a git repository")
        {:error, :not_a_repo}

      {:error, reason} ->
        UI.error("Failed to merge worktree: #{format_reason(reason)}")
        {:error, reason}
    end
  end

  def run(_opts, [], _unknown) do
    UI.error("No subcommand specified. Use 'fnord worktrees --help' for help.")
  end

  def run(_opts, _subcommands, _unknown) do
    UI.error("Unknown subcommand. Use 'fnord worktrees --help' for help.")
  end

  # Reads the gitignored_writes accumulator from a conversation's persisted
  # metadata and copies those files (plus any found by the safety-net scan)
  # from the worktree to the source repo. Returns the list of successfully
  # copied relative paths for display in the review section.
  @spec copy_ignored_writes_for_conversation(String.t(), String.t(), String.t()) :: [String.t()]
  defp copy_ignored_writes_for_conversation(conv_id, worktree_path, source_root) do
    conv = Store.Project.Conversation.new(conv_id)

    conv_meta =
      case Store.Project.Conversation.read(conv) do
        {:ok, data} -> data.metadata
        _ -> %{}
      end

    files =
      conv_meta
      |> Map.get(:gitignored_writes, [])
      |> Enum.filter(&File.exists?(Path.join(worktree_path, &1)))

    if files != [] do
      results = GitCli.Worktree.copy_ignored_files(source_root, worktree_path, files)

      Enum.each(results, fn
        {:ok, _rel} -> :ok
        {:error, rel, reason} -> UI.warn("Failed to copy #{rel}: #{reason}")
      end)

      for {:ok, rel} <- results, do: rel
    else
      []
    end
  end

  # Resolves worktree metadata from a conversation id by first consulting the
  # conversation's persisted metadata and then falling back to a matching
  # fnord-managed worktree discovered from the repository's worktree list.
  @spec resolve_worktree_meta(String.t()) ::
          {:ok, GitCli.Worktree.Review.worktree_info()} | {:error, atom()}
  defp resolve_worktree_meta(conv_id) do
    case resolve_worktree_meta_from_conversation(conv_id) do
      {:ok, _} = ok -> ok
      {:error, _} -> resolve_worktree_meta_from_disk(conv_id)
    end
  end

  defp resolve_worktree_meta_from_conversation(conv_id) do
    conv = Store.Project.Conversation.new(conv_id)

    with {:ok, data} <- Store.Project.Conversation.read(conv) do
      raw =
        data.metadata
        |> GitCli.Worktree.normalize_worktree_meta_in_parent()
        |> Map.get(:worktree)

      case raw do
        %{path: path, branch: branch, base_branch: base_branch}
        when is_binary(path) and is_binary(branch) and is_binary(base_branch) ->
          {:ok, raw}

        _ ->
          {:error, :no_worktree_metadata}
      end
    end
  end

  defp resolve_worktree_meta_from_disk(conv_id) do
    with {:ok, project} <- Store.get_project(),
         {:ok, root} <- GitCli.Worktree.project_root(),
         {:ok, entries} <- GitCli.Worktree.list(root) do
      case Enum.find(entries, fn entry ->
             GitCli.Worktree.fnord_managed?(project.name, entry.path) and
               Path.basename(entry.path) == conv_id and
               is_binary(entry.branch) and
               is_binary(entry.base_branch)
           end) do
        nil -> {:error, :no_worktree_metadata}
        entry -> {:ok, %{path: entry.path, branch: entry.branch, base_branch: entry.base_branch}}
      end
    end
  end

  @spec resolve_repo_root_for_view(String.t()) ::
          {:ok, String.t()} | {:error, :missing_worktree_path | :not_a_repo}
  defp resolve_repo_root_for_view(path) when is_binary(path) do
    if File.dir?(path) do
      case System.cmd("git", ["rev-parse", "--show-toplevel"], cd: path, stderr_to_stdout: true) do
        {out, 0} -> {:ok, String.trim(out)}
        _ -> {:error, :not_a_repo}
      end
    else
      {:error, :missing_worktree_path}
    end
  end

  defp format_merge_status(:merged), do: "merged"
  defp format_merge_status(:ahead), do: "ahead"
  defp format_merge_status(:diverged), do: "diverged"
  defp format_merge_status(_), do: "unknown"

  # Appends the merge-command template below the table so the user has the
  # invocation in front of them without having to remember the flag shape.
  # The conversation id placeholder stays generic - the ids are already
  # visible in the Conversation column of the table above.
  defp print_merge_hints() do
    UI.puts("")
    UI.puts("To merge a worktree:")
    UI.puts("  fnord worktrees merge -c <conversation-id>")
    UI.puts("")
  end

  defp format_size(bytes) when bytes >= 1_048_576, do: "#{Float.round(bytes / 1_048_576, 1)} MB"
  defp format_size(bytes) when bytes >= 1_024, do: "#{Float.round(bytes / 1_024, 1)} KB"
  defp format_size(bytes), do: "#{bytes} B"

  @column_order %{
    "Conversation" => 0,
    "Branch" => 1,
    "Base" => 2,
    "Status" => 3,
    "Dirty" => 4,
    "Size" => 5,
    "Path" => 6
  }
  defp column_order(col), do: Map.get(@column_order, col, 99)

  defp format_reason(reason) when is_atom(reason), do: Atom.to_string(reason)
end