defmodule BearCli.Accounts do
  @moduledoc """
  `bear accounts` 指令群（帳號管理；docs/commands.md §3.9、issue #12）。

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

  CLI 對外介面一律以 `email` 識別帳號（人類可讀、唯一）；API 路徑參數為
  UUID，由本模組先以 list 分頁比對解析。帳號 JSON 不含 `hash_password`、
  `totp_secret` 等機密欄位（API 端保證），CLI 亦不顯示。

  `create`／`set-password` 未給 `--password` 時由 CLI 產生隨機密碼，並只在
  成功當下一次性輸出（不寫入憑證檔／log／`--verbose`）；密碼一律不進命令列
  （避免 shell history／`ps`），改以互動輸入（不回顧）或 `--generate-password`。

  敏感規則與伺服器端一致：不可移除自己的 admin 角色（403）、不可刪除自己（403）。

  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
  alias BearCli.TTY

  @list_per_page_fetch 100
  @max_fetch_pages 50

  # -- 入口 --

  @doc """
  執行 `bear accounts <動詞>`，回傳退出碼。`opts[:accounts_api]` 可注入假
  API 模組供測試（需實作 `accounts_list/3`、`accounts_create/3`、
  `accounts_get/3`、`accounts_update_role/4`、`accounts_set_password/4`、
  `accounts_delete/3`）。
  """
  def run(verb, opts) do
    api = opts[:accounts_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
    params = [page: opts[:page] || 1, per_page: opts[:per_page] || 20]

    case api.accounts_list(ctx.issuer, ctx.token, params) do
      {:ok, body} ->
        accounts = body["data"] || []
        page = body["page"] || params[:page]
        per_page = body["per_page"] || params[:per_page]
        total = body["total"] || length(accounts)
        render_list(opts, accounts, page, per_page, total)
        0

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

  defp execute(:show, ctx, opts, api) do
    with {:ok, account} <- resolve_account(ctx, opts[:email_arg], api) do
      case api.accounts_get(ctx.issuer, ctx.token, account["id"]) do
        {:ok, body} ->
          show_account(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
    with {:ok, password} <- read_password(opts) do
      attrs = %{"email" => opts[:email], "hash_password" => password}
      attrs = if opts[:role], do: Map.put(attrs, "role", opts[:role]), else: attrs

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

          if opts[:json] do
            IO.puts(Jason.encode!(%{ok: true, account: account, initial_password: password}))
          else
            IO.puts("帳號已建立：#{account["email"]}（#{account["role"]}）")
            print_password_block(password)
          end

          0

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

  defp execute(:update, ctx, opts, api) do
    with {:ok, account} <- resolve_account(ctx, opts[:email_arg], api) do
      case api.accounts_update_role(ctx.issuer, ctx.token, account["id"], %{"role" => opts[:role]}) do
        {:ok, body} ->
          updated = body["data"] || %{}

          if opts[:json] do
            IO.puts(Jason.encode!(%{ok: true, account: updated}))
          else
            IO.puts("#{updated["email"]}：角色 → #{updated["role"]}")
          end

          0

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

  defp execute(:"set-password", ctx, opts, api) do
    with {:ok, account} <- resolve_account(ctx, opts[:email_arg], api),
         {:ok, password} <- read_password(opts) do
      case api.accounts_set_password(ctx.issuer, ctx.token, account["id"], %{
             "hash_password" => password
           }) do
        {:ok, _body} ->
          if opts[:json] do
            IO.puts(Jason.encode!(%{ok: true, email: account["email"], new_password: password}))
          else
            IO.puts("已為 #{account["email"]} 設定新密碼。")
            print_password_block(password)
          end

          0

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

  defp execute(:delete, ctx, opts, api) do
    with {:ok, account} <- resolve_account(ctx, opts[:email_arg], api) do
      case api.accounts_delete(ctx.issuer, ctx.token, account["id"]) do
        {:ok, _body} ->
          if opts[:json] do
            IO.puts(Jason.encode!(%{ok: true, email: account["email"], deleted: true}))
          else
            IO.puts("已刪除帳號：#{account["email"]}")
          end

          0

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

  # -- email → UUID 解析（分頁全量列舉比對；設頁數上限避免無限迴圈）--

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

  defp resolve_account(ctx, email, api) do
    with {:ok, all} <- fetch_all(ctx, api) do
      case Enum.find(all, &(&1["email"] == email)) do
        nil -> {:error, "找不到 email 為 #{email} 的帳號", 1}
        account -> {:ok, account}
      end
    else
      {:error, message, code} -> {:error, message, code}
    end
  end

  defp fetch_all(ctx, api) do
    do_fetch_all(ctx, api, 1, [])
  end

  defp do_fetch_all(_ctx, _api, page, acc) when page > @max_fetch_pages, do: {:ok, acc}

  defp do_fetch_all(ctx, api, page, acc) do
    case api.accounts_list(ctx.issuer, ctx.token, page: page, per_page: @list_per_page_fetch) do
      {:ok, body} ->
        entries = body["data"] || []
        acc = acc ++ entries
        total = body["total"]

        if entries == [] or length(entries) < @list_per_page_fetch or
             (is_integer(total) and length(acc) >= total) do
          {:ok, acc}
        else
          do_fetch_all(ctx, api, page + 1, acc)
        end

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

  # -- 密碼輸入（不進命令列；非 TTY 且未 --generate-password → 用法錯誤）--

  defp read_password(%{generate_password: true}), do: {:ok, generate_password()}

  defp read_password(_opts) do
    if tty?() do
      password = prompt_password("新密碼（至少 8 字元，含字母與數字）：")
      confirm = prompt_password("再次輸入新密碼：")

      cond do
        password != confirm ->
          {:error, "兩次輸入的密碼不一致", 2}

        weak_password?(password) ->
          {:error, "密碼至少 8 字元且須包含字母與數字", 2}

        true ->
          {:ok, password}
      end
    else
      {:error, "非 TTY 環境無法互動輸入密碼；請加 --generate-password 由 CLI 產生", 2}
    end
  end

  @password_chars "ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnpqrstuvwxyz23456789"
  @password_length 16

  defp generate_password do
    @password_chars
    |> String.codepoints()
    |> Enum.take_random(@password_length)
    |> Enum.join()
  end

  defp weak_password?(password) when is_binary(password) do
    String.length(password) >= 8 and Regex.match?(~r/[a-zA-Z]/, password) and
      Regex.match?(~r/[0-9]/, password)
  end

  defp weak_password?(_), do: true

  # stdin 是否為 TTY：優先以 fd 0 實際裝置判定（escript 環境 :io.columns/0
  # 一律 enotsup，真終端機會被誤判；見 BearCli.TTY，issue #19）。
  defp tty? do
    TTY.stdin_tty?()
  end

  defp prompt_password(prompt) do
    IO.puts(:stderr, prompt)
    IO.gets("") |> String.trim_trailing("\n")
  end

  # -- 輸出 --

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

  @table_headers ["EMAIL", "ROLE", "TOTP", "CREATED AT"]

  defp print_table(accounts) do
    rows =
      Enum.map(accounts, fn account ->
        [
          account["email"] || "",
          account["role"] || "",
          totp_label(account["totp_enabled"]),
          account["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

  @account_fields ~w(id email role totp_enabled created_at updated_at)

  defp show_account(account, opts) do
    if opts[:json] do
      IO.puts(Jason.encode!(%{ok: true, account: account}))
    else
      Enum.each(@account_fields, fn field ->
        IO.puts("#{String.pad_trailing(field, 16)}: #{format_account_value(account[field])}")
      end)
    end
  end

  defp format_account_value(nil), do: "(無)"
  defp format_account_value(true), do: "已啟用"
  defp format_account_value(false), do: "未啟用"
  defp format_account_value(value) when is_binary(value), do: value
  defp format_account_value(value), do: Jason.encode!(value)

  defp totp_label(true), do: "on"
  defp totp_label(false), do: "off"
  defp totp_label(_), do: "(未知)"

  # 初始／新密碼只在成功當下一次性輸出（不寫入憑證檔／log／--verbose）。
  defp print_password_block(password) do
    IO.puts("初始密碼（只顯示這一次，請立即保存並轉交當事人）：")
    IO.puts("  #{password}")
  end

  # -- 錯誤處理 --

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