defmodule BearCli.Jwks do
  @moduledoc """
  `bear jwks` 指令群（簽章金鑰管理；docs/commands.md §3.8、issue #12）。

  對應伺服器端 JWK 管理 JSON API（alterminal/bear#46，`/api/v1/jwks`、
  PAT Bearer、admin 限定）。認證沿用既有 PAT 憑證（`BEAR_TOKEN` 或憑證檔）。

  金鑰材質（`key_data`）永不經 CLI 顯示（API 端即不序列化）；本群組只管理
  公開中繼資料（kid／kty／alg／active 等）。

  退出碼：0 成功；1 404／422；2 用法錯誤；3 未登入或 401；6 網路／伺服器
  錯誤；8 權限不足（403，僅限 admin）。
  """

  import BearCli.Admin, only: [context: 1, fail: 3, format_api_error: 2]
  alias BearCli.Api

  # -- 入口 --

  @doc """
  執行 `bear jwks <動詞>`，回傳退出碼。`opts[:jwks_api]` 可注入假 API 模組
  供測試（需實作 `jwks_list/2`、`jwks_create/3`、`jwks_get/3`、`jwks_toggle/3`）。
  """
  def run(verb, opts) do
    api = opts[:jwks_api] || Api

    with {:ok, ctx} <- context(opts) do
      execute(verb, ctx, opts, api)
    else
      {:error, message, code} -> fail(opts, message, code)
    end
  end

  # -- 各動詞 --

  defp execute(:list, ctx, opts, api) do
    case api.jwks_list(ctx.issuer, ctx.token) do
      {:ok, body} ->
        render_list(opts, body["data"] || [])
        0

      {:error, _kind, _detail} = error ->
        fail_api(opts, ctx, error)
    end
  end

  defp execute(:show, ctx, opts, api) do
    with {:ok, key} <- resolve_key(ctx, opts[:kid_arg], api) do
      case api.jwks_get(ctx.issuer, ctx.token, key["id"]) do
        {:ok, body} ->
          show_key(body["data"] || %{}, opts)
          0

        {:error, _kind, _detail} = error ->
          fail_api(opts, ctx, error)
      end
    else
      {:error, message, code} -> fail(opts, message, code)
    end
  end

  defp execute(:create, ctx, opts, api) do
    attrs = %{"kid" => opts[:kid], "alg" => opts[:alg] || "RS256"}

    case api.jwks_create(ctx.issuer, ctx.token, attrs) do
      {:ok, body} ->
        key = body["data"] || %{}

        if opts[:json] do
          IO.puts(Jason.encode!(%{ok: true, jwk: key}))
        else
          IO.puts("JWK 已建立：#{key["kid"]}（#{key["alg"]}／#{status_label(key)}）")
        end

        0

      {:error, _kind, _detail} = error ->
        fail_api(opts, ctx, error)
    end
  end

  defp execute(:toggle, ctx, opts, api) do
    with {:ok, key} <- resolve_key(ctx, opts[:kid_arg], api) do
      case api.jwks_toggle(ctx.issuer, ctx.token, key["id"]) do
        {:ok, body} ->
          updated = body["data"] || %{}

          if opts[:json] do
            IO.puts(
              Jason.encode!(%{
                ok: true,
                jwk: %{id: updated["id"], kid: updated["kid"], active: updated["active"]}
              })
            )
          else
            IO.puts("#{key["kid"]}：#{status_label(key)} → #{status_label(updated)}")
          end

          0

        {:error, _kind, _detail} = error ->
          fail_api(opts, ctx, error)
      end
    else
      {:error, message, code} -> fail(opts, message, code)
    end
  end

  # -- kid → UUID 解析（API 路徑參數為 UUID，CLI 對外介面用 kid）--

  defp resolve_key(_ctx, nil, _api), do: {:error, "缺少 <kid> 參數", 2}

  defp resolve_key(ctx, kid, api) do
    case api.jwks_list(ctx.issuer, ctx.token) do
      {:ok, body} ->
        case Enum.find(body["data"] || [], &(&1["kid"] == kid)) do
          nil -> {:error, "找不到 kid 為 #{kid} 的金鑰", 1}
          key -> {:ok, key}
        end

      {:error, _kind, _detail} = error ->
        {message, code} = format_api_error(ctx, error)
        {:error, message, code}
    end
  end

  # -- 輸出 --

  defp render_list(opts, keys) do
    if opts[:json] do
      IO.puts(Jason.encode!(%{ok: true, jwks: keys}))
    else
      print_table(keys)
    end
  end

  @table_headers ["ID", "KID", "KTY", "ALG", "ACTIVE", "CREATED AT"]

  defp print_table(keys) do
    rows =
      Enum.map(keys, fn key ->
        [
          String.slice(key["id"] || "", 0, 8),
          key["kid"] || "",
          key["kty"] || "",
          key["alg"] || "",
          status_label(key),
          key["created_at"] || ""
        ]
      end)

    widths =
      Enum.with_index(@table_headers, fn _header, i ->
        Enum.max([
          String.length(Enum.at(@table_headers, i))
          | Enum.map(rows, &String.length(Enum.at(&1, i)))
        ])
      end)

    render_row = fn cells ->
      cells
      |> Enum.with_index()
      |> Enum.map(fn {cell, i} -> String.pad_trailing(cell, Enum.at(widths, i)) end)
      |> Enum.join("  ")
      |> String.trim_trailing()
    end

    IO.puts(render_row.(@table_headers))
    Enum.each(rows, fn cells -> IO.puts(render_row.(cells)) end)
  end

  @key_fields ~w(id kid kty alg use active created_at)

  defp show_key(key, opts) do
    if opts[:json] do
      IO.puts(Jason.encode!(%{ok: true, jwk: key}))
    else
      Enum.each(@key_fields, fn field ->
        IO.puts("#{String.pad_trailing(field, 14)}: #{format_key_value(key[field])}")
      end)
    end
  end

  defp format_key_value(nil), do: "(無)"
  defp format_key_value(value) when is_binary(value), do: value
  defp format_key_value(value), do: Jason.encode!(value)

  defp status_label(%{"active" => true}), do: "active"
  defp status_label(%{"active" => false}), do: "inactive"
  defp status_label(_), do: "(未知)"

  # -- 錯誤處理 --

  defp fail_api(opts, ctx, error) do
    {message, code} = format_api_error(ctx, error)
    fail(opts, message, code)
  end
end