defmodule XlsxReader do
  @moduledoc """

  Opens XLSX workbook and reads its worksheets.

  ## Example

  ```elixir
  {:ok, package} = XlsxReader.open("test.xlsx")

  XlsxReader.sheet_names(package)
  # ["Sheet 1", "Sheet 2", "Sheet 3"]

  {:ok, rows} = XlsxReader.sheet(package, "Sheet 1")
  # [
  #   ["Date", "Temperature"],
  #   [~D[2019-11-01], 8.4],
  #   [~D[2019-11-02], 7.5],
  #   ...
  # ]
  ```

  ## Sheet contents

  Sheets are loaded on-demand by `sheet/3` and `sheets/2`.

  The sheet contents is returned as a list of lists:

  ```elixir
  [
    ["A1", "B1", "C1" | _],
    ["A2", "B2", "C2" | _],
    ["A3", "B3", "C3" | _],
    | _
  ]
  ```

  The behavior of the sheet parser can be customized for each
  individual sheet, see `sheet/3`.

  """

  alias XlsxReader.{PackageLoader, ZipArchive}

  @typedoc """
  Source for the XLSX file: file system (`:path`) or in-memory (`:binary`)
  """
  @type source :: :path | :binary

  @typedoc """
  Option to specify the XLSX file source
  """
  @type source_option :: {:source, source()}

  @typedoc """
  List of cell values
  """
  @type row :: list(any())

  @typedoc """
  List of rows
  """
  @type rows :: list(row())

  @typedoc """
  Sheet name
  """
  @type sheet_name :: String.t()

  @typedoc """
  Error tuple with message describing the cause of the error
  """
  @type error :: {:error, String.t()}

  @doc """

  Opens an XLSX file located on the file system (default) or from memory.

  ## Examples

  ### Opening XLSX file on the file system

  ```elixir
  {:ok, package} = XlsxReader.open("test.xlsx")
  ```

  ### Opening XLSX file from memory

  ```elixir
  blob = File.read!("test.xlsx")

  {:ok, package} = XlsxReader.open(blob, source: :binary)
  ```

  ## Options

    * `source`: `:path` (on the file system, default) or `:binary` (in memory)

  """
  @spec open(String.t() | binary(), [source_option]) ::
          {:ok, XlsxReader.Package.t()} | error()
  def open(file, options \\ []) do
    file
    |> ZipArchive.handle(Keyword.get(options, :source, :path))
    |> PackageLoader.open()
  end

  @doc """

  Lists the names of the sheets in the package's workbook

  """
  @spec sheet_names(XlsxReader.Package.t()) :: [sheet_name()]
  def sheet_names(package) do
    for %{name: name} <- package.workbook.sheets, do: name
  end

  @doc """

  Loads the sheet with the given name (see `sheet_names/1`)

  ## Options

    * `type_conversion` - boolean (default: `true`)
    * `blank_value` - placeholder value for empty cells (default: `""`)
    * `empty_rows` - include empty rows (default: `true`)
    * `number_type` - type used for numeric conversion :`Integer`, 'Decimal' or `Float` (default: `Float`)

  The `Decimal` type requires the [decimal](https://github.com/ericmj/decimal) library.

  """
  @spec sheet(XlsxReader.Package.t(), sheet_name(), Keyword.t()) :: {:ok, rows()}
  def sheet(package, sheet_name, options \\ []) do
    PackageLoader.load_sheet_by_name(package, sheet_name, options)
  end

  @doc """

  Loads all the sheets in the workbook.

  On success, returns `{:ok, [{sheet_name, rows}, ...]}`.

  ## Filtering options

    * `only` - include the sheets whose name matches the filter
    * `except` - exclude the sheets whose name matches the filter

  Sheets can filtered by name using:

    * a string (e.g. `"Exact Match"`)
    * a regex (e.g. `~r/Sheet \d+/`)
    * a list of string and/or regexes (e.g. `["Parameters", ~r/Sheet [12]/]`)

  ## Sheet options

  See `sheet/2`.

  """
  @spec sheets(XlsxReader.Package.t(), Keyword.t()) ::
          {:ok, list({sheet_name(), rows()})} | error()
  def sheets(package, options \\ []) do
    package.workbook.sheets
    |> filter_sheets_by_name(
      sheet_filter_option(options, :only),
      sheet_filter_option(options, :except)
    )
    |> Enum.reduce_while([], fn sheet, acc ->
      case PackageLoader.load_sheet_by_rid(package, sheet.rid, options) do
        {:ok, rows} ->
          {:cont, [{sheet.name, rows} | acc]}

        error ->
          {:halt, error}
      end
    end)
    |> case do
      sheets when is_list(sheets) ->
        {:ok, Enum.reverse(sheets)}

      error ->
        error
    end
  end

  @doc """

  Loads all the sheets in the workbook concurrently.

  On success, returns `{:ok, [{sheet_name, rows}, ...]}`.

  When processing files with multiple sheets, `async_sheets/3` is ~3x faster than `sheets/2`
  but it comes with a caveat. `async_sheets/3` uses `Task.async_stream/3` under the hood and thus
  runs each concurrent task with a timeout. If you expect your dataset to be of a significant size,
  you may want to increase it from the default 10000ms (see "Concurrency options" below).

  If the order in which the sheets are returned is not relevant for your application, you can
  pass `ordered: false` (see "Concurrency options" below) for a modest speed gain.

  ## Filtering options

  See `sheets/2`.

  ## Sheet options

  See `sheet/2`.

  ## Concurrency options

    * `max_concurrency` - maximum number of tasks to run at the same time (default: `System.schedulers_online/0`)
    * `ordered` - maintain order consistent with `sheet_names/1` (default: `true`)
    * `timeout` - maximum duration in milliseconds to process a sheet (default: `10_000`)

  """
  def async_sheets(package, sheet_options \\ [], task_options \\ []) do
    max_concurrency = Keyword.get(task_options, :max_concurrency, System.schedulers_online())
    ordered = Keyword.get(task_options, :ordered, true)
    timeout = Keyword.get(task_options, :timeout, 10_000)

    package.workbook.sheets
    |> filter_sheets_by_name(
      sheet_filter_option(sheet_options, :only),
      sheet_filter_option(sheet_options, :except)
    )
    |> Task.async_stream(
      fn sheet ->
        case PackageLoader.load_sheet_by_rid(package, sheet.rid, sheet_options) do
          {:ok, rows} ->
            {:ok, {sheet.name, rows}}

          error ->
            error
        end
      end,
      max_concurrency: max_concurrency,
      ordered: ordered,
      timeout: timeout,
      on_timeout: :kill_task
    )
    |> Enum.reduce_while({:ok, []}, fn
      {:ok, {:ok, entry}}, {:ok, acc} ->
        {:cont, {:ok, [entry | acc]}}

      {:ok, error}, _acc ->
        {:halt, {:error, error}}

      {:exit, :timeout}, _acc ->
        {:halt, {:error, "timeout exceeded"}}

      {:exit, reason}, _acc ->
        {:halt, {:error, reason}}
    end)
    |> case do
      {:ok, list} ->
        if ordered,
          do: {:ok, Enum.reverse(list)},
          else: {:ok, list}

      error ->
        error
    end
  end

  ## Sheet filter

  def sheet_filter_option(options, key),
    do: options |> Keyword.get(key, []) |> List.wrap()

  defp filter_sheets_by_name(sheets, [], []), do: sheets

  defp filter_sheets_by_name(sheets, only, except) do
    Enum.filter(sheets, fn %{name: name} ->
      filter_only?(name, only) && !filter_except?(name, except)
    end)
  end

  defp filter_only?(_name, []), do: true
  defp filter_only?(name, filters), do: Enum.any?(filters, &filter_match?(name, &1))

  defp filter_except?(_name, []), do: false
  defp filter_except?(name, filters), do: Enum.any?(filters, &filter_match?(name, &1))

  defp filter_match?(name, %Regex{} = regex), do: String.match?(name, regex)
  defp filter_match?(exact_match, exact_match) when is_binary(exact_match), do: true
  defp filter_match?(_, _), do: false
end