From 69295e463bc1c92c2d745d0e77b1985515952522 Mon Sep 17 00:00:00 2001
From: Stas Versilov <stas.versilov@gmail.com>
Date: Mon, 7 May 2018 01:44:59 +0400
Subject: [PATCH] Large matrices pretty print.

---
 lib/matrex/inspect.ex | 53 ++++++++++++++++++++++++++-----------------
 1 file changed, 32 insertions(+), 21 deletions(-)

diff --git a/lib/matrex/inspect.ex b/lib/matrex/inspect.ex
index eb36a19..6344110 100644
--- a/lib/matrex/inspect.ex
+++ b/lib/matrex/inspect.ex
@@ -10,7 +10,7 @@ defimpl Inspect, for: Matrex do
         },
         %{width: screen_width} = _opts
       )
-      when columns < screen_width / 8 do
+      when columns < screen_width / 8 and rows <= 50 do
     rows_as_strings =
       for(
         row <- 1..rows,
@@ -32,21 +32,21 @@ defimpl Inspect, for: Matrex do
 
   def inspect(
         %Matrex{
-          data:
-            <<
-              rows::unsigned-integer-little-32,
-              columns::unsigned-integer-little-32,
-              body::binary
-            >> = data
+          data: <<
+            rows::unsigned-integer-little-32,
+            columns::unsigned-integer-little-32,
+            body::binary
+          >>
         },
         %{width: screen_width} = _opts
       )
-      when columns >= screen_width / 8 do
+      when columns >= screen_width / 8 or rows > 50 do
     suffix_size = prefix_size = div(screen_width, 16)
     element_chars_size = 8
 
     rows_as_strings =
-      for row <- 0..(rows - 1), do: format_row(body, row, rows, columns, suffix_size, prefix_size)
+      for row <- displayable_rows(rows),
+          do: format_row(body, row, rows, columns, suffix_size, prefix_size)
 
     rows_as_strings = [
       binary_part(body, 0, prefix_size * @element_byte_size)
@@ -54,22 +54,33 @@ defimpl Inspect, for: Matrex do
       | rows_as_strings
     ]
 
-    # rows_as_strings =
-    #   for(
-    #     row <- 1..rows,
-    #     do:
-    #       Matrex.row_as_list(data, row - 1)
-    #       |> Enum.map(&(Float.round(&1, 5) |> Float.to_string() |> String.pad_leading(8)))
-    #       |> Enum.join()
-    #   )
-
-    row_length = element_chars_size * (suffix_size + prefix_size) + 8
+    row_length = element_chars_size * (suffix_size + prefix_size) + 5
+    half_row_length = div(row_length, 2)
     top = "#{IO.ANSI.white()}┌#{String.pad_trailing("", row_length)}┐\n│#{IO.ANSI.yellow()}"
     bottom = " #{IO.ANSI.white()}│\n└#{String.pad_trailing("", row_length)}┘"
-    contents_str = rows_as_strings |> Enum.join(IO.ANSI.white() <> "  ...  " <> IO.ANSI.yellow())
-    "#Matrix[#{rows}x#{columns}]\n#{top}#{contents_str}#{bottom}"
+
+    contents_str =
+      rows_as_strings
+      |> Enum.join(IO.ANSI.white() <> "  … " <> IO.ANSI.yellow())
+      |> String.replace(
+        ~r/\n.*⋮.*\n/,
+        "\n│#{String.pad_leading("", half_row_length, "     ⋮  ")}… #{
+          String.pad_trailing("", half_row_length - 1, "     ⋮  ")
+        }│\n"
+      )
+
+    "#{IO.ANSI.white()}#Matrix#{IO.ANSI.light_white()}[#{IO.ANSI.yellow()}#{rows}#{
+      IO.ANSI.light_white()
+    }×#{IO.ANSI.yellow()}#{columns}#{IO.ANSI.light_white()}]\n#{top}#{contents_str}#{bottom}"
   end
 
+  defp displayable_rows(rows) when rows > 50,
+    do: Enum.to_list(0..25) ++ [-1] ++ Enum.to_list((rows - 25)..(rows - 1))
+
+  defp displayable_rows(rows), do: 0..(rows - 1)
+
+  defp format_row(_body, -1, _rows, _columns, _, _), do: "⋮"
+
   defp format_row(body, row, rows, columns, suffix_size, prefix_size) when row == rows - 1 do
     n = chunk_offset(row, columns, suffix_size)