From dd137f3a3712fa663741efeaea41dc3cc7f0bb0d Mon Sep 17 00:00:00 2001
From: frazze-jobb <frazze@erlang.org>
Date: Tue, 22 Aug 2023 11:48:43 +0200
Subject: [PATCH] ssh: support dumb terminals in ssh client

---
 lib/ssh/src/ssh_cli.erl  | 37 ++++++++++++++++++++++++++++++++-----
 lib/stdlib/src/edlin.erl |  3 +++
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/lib/ssh/src/ssh_cli.erl b/lib/ssh/src/ssh_cli.erl
index 9f6d3be21d91..2ba406ad69e6 100644
--- a/lib/ssh/src/ssh_cli.erl
+++ b/lib/ssh/src/ssh_cli.erl
@@ -418,6 +418,28 @@ to_group(Data, Group) ->
 %%% displaying device...
 %%% We are *not* really unicode aware yet, we just filter away characters 
 %%% beyond the latin1 range. We however handle the unicode binaries...
+io_request(Request, Buf, Tty = #ssh_pty{term = "dumb"}, Group) ->
+    %% When we have a dumb terminal, we should only support outputing text, no navigation
+    %% or redraws necessary.
+    case Request of
+        {put_chars, Cs} ->
+            put_chars_dumb(bin_to_list(Cs), Buf, Tty);
+        {put_chars, unicode, Cs} ->
+            put_chars_dumb(unicode:characters_to_list(Cs,unicode), Buf, Tty);
+        {put_chars_sync, unicode, Cs, Reply} ->
+            Group ! {reply, Reply, ok},
+            put_chars_dumb(unicode:characters_to_list(Cs,unicode), Buf, Tty);
+        {insert_chars, Cs} ->
+            put_chars_dumb(bin_to_list(Cs), Buf, Tty);
+        {insert_chars, unicode, Cs} ->
+            put_chars_dumb(unicode:characters_to_list(Cs,unicode), Buf, Tty);
+        {requests,Rs} ->
+            io_requests(Rs, Buf, Tty, [], Group);
+        beep ->
+            {[7], Buf};
+        _Ignore ->
+            {[], Buf}
+    end;
 io_request({window_change, OldTty}, Buf, Tty, _Group) ->
     window_change(Tty, OldTty, Buf);
 io_request({put_chars, Cs}, Buf, Tty, _Group) ->
@@ -509,10 +531,10 @@ get_tty_command(left, N, _TerminalType) ->
 -define(TABWIDTH, 8).
 
 %% convert input characters to buffer and to writeout
-%% Note that the buf is reversed but the buftail is not
+%% Note that Bef is reversed but Aft is not
 %% (this is handy; the head is always next to the cursor)
 conv_buf([], {LB, {Bef, Aft}, LA, Col}, AccWrite, _Tty) ->
-    {{LB, {Bef, Aft}, LA}, lists:reverse(AccWrite), Col};
+    {{LB, {Bef, Aft}, LA, Col}, lists:reverse(AccWrite)};
 conv_buf([13, 10 | Rest], {LB, {Bef, Aft}, LA, Col}, AccWrite, Tty = #ssh_pty{width = W}) ->
     conv_buf(Rest, {[lists:reverse(Bef)|LB], {[], tl2(Aft)}, LA, Col+(W-(Col rem W))}, [10, 13 | AccWrite], Tty);
 conv_buf([13 | Rest], {LB, {Bef, Aft}, LA, Col}, AccWrite, Tty = #ssh_pty{width = W}) ->
@@ -531,20 +553,25 @@ conv_buf([C | Rest], {LB, {Bef, Aft}, LA, Col}, AccWrite, Tty) ->
 %%% put characters before the prompt
 put_chars(Chars, Buf, Tty) ->
     case Buf of
-        {[],{[],[]},[],_} -> {_, WriteBuf, _} = conv_buf(Chars, Buf, [], Tty),
+        {[],{[],[]},[],_} -> {_, WriteBuf} = conv_buf(Chars, Buf, [], Tty),
             {WriteBuf, Buf};
         _ ->
             {Delete, DeletedState} = io_request(delete_line, Buf, Tty, []),
-            {_, PutBuffer, _} = conv_buf(Chars, DeletedState, [], Tty),
+            {_, PutBuffer} = conv_buf(Chars, DeletedState, [], Tty),
             {Redraw, _} = io_request(redraw_prompt_pre_deleted, Buf, Tty, []),
             {[Delete, PutBuffer, Redraw], Buf}
     end.
+%%% put characters at current position (possibly overwriting
+%%% characters after current position in buffer)
+put_chars_dumb(Chars, Buf, Tty) ->
+    {NewBuf, WriteBuf} = conv_buf(Chars, Buf, [], Tty),
+    {WriteBuf, NewBuf}.
 
 %%% insert character at current position
 insert_chars([], Buf, _Tty) ->
     {[], Buf};
 insert_chars(Chars, {_LB,{_Bef, Aft},LA, _Col}=Buf, Tty) ->
-    {{NewLB, {NewBef, _NewAft}, _NewLA}, WriteBuf, NewCol} = conv_buf(Chars, Buf, [], Tty),
+    {{NewLB, {NewBef, _NewAft}, _NewLA, NewCol}, WriteBuf} = conv_buf(Chars, Buf, [], Tty),
     M = move_cursor(special_at_width(NewCol+length(Aft), Tty), NewCol, Tty),
     {[WriteBuf, Aft | M], {NewLB,{NewBef, Aft},LA, NewCol}}.
 
diff --git a/lib/stdlib/src/edlin.erl b/lib/stdlib/src/edlin.erl
index d3b189c1a723..f09ef1e68835 100644
--- a/lib/stdlib/src/edlin.erl
+++ b/lib/stdlib/src/edlin.erl
@@ -71,6 +71,9 @@ start(Pbs) ->
 
 %% Only two modes used: 'none' and 'search'. Other modes can be
 %% handled inline through specific character handling.
+start(Pbs, {_,{_,_},[]}=Cont) ->
+    %% Skip redraw if the cursor is at the end.
+    {more_chars,{line,Pbs,Cont,none},[{insert_chars,unicode,multi_line_prompt(Pbs)}]};
 start(Pbs, {_,{_,_},_}=Cont) ->
     {more_chars,{line,Pbs,Cont,none},redraw(Pbs, Cont, [])};