" Debugger plugin using gdb.
"
" Author: Bram Moolenaar
" Copyright: Vim license applies, see ":help license"
" Last Update: 2018 Jun 3
"
" WORK IN PROGRESS - Only the basics work
" Note: On MS-Windows you need a recent version of gdb.  The one included with
" MingW is too old (7.6.1).
" I used version 7.12 from http://www.equation.com/servlet/equation.cmd?fa=gdb
"
" There are two ways to run gdb:
" - In a terminal window; used if possible, does not work on MS-Windows
"   Not used when g:termdebug_use_prompt is set to 1.
" - Using a "prompt" buffer; may use a terminal window for the program
"
" For both the current window is used to view source code and shows the
" current statement from gdb.
"
" USING A TERMINAL WINDOW
"
" Opens two visible terminal windows:
" 1. runs a pty for the debugged program, as with ":term NONE"
" 2. runs gdb, passing the pty of the debugged program
" A third terminal window is hidden, it is used for communication with gdb.
"
" USING A PROMPT BUFFER
"
" Opens a window with a prompt buffer to communicate with gdb.
" Gdb is run as a job with callbacks for I/O.
" On Unix another terminal window is opened to run the debugged program
" On MS-Windows a separate console is opened to run the debugged program
"
" The communication with gdb uses GDB/MI.  See:
" https://sourceware.org/gdb/current/onlinedocs/gdb/GDB_002fMI.html
"
" For neovim compatibility, the vim specific calls were replaced with neovim
" specific calls:
"   term_start -> term_open
"   term_sendkeys -> chansend
"   term_getline -> getbufline
"   job_info && term_getjob -> using linux command ps to get the tty
"   balloon -> nvim floating window
"
" The code for opening the floating window was taken from the beautiful
" implementation of LanguageClient-Neovim: 
" https://github.com/autozimu/LanguageClient-neovim/blob/0ed9b69dca49c415390a8317b19149f97ae093fa/autoload/LanguageClient.vim#L304
"
" Neovim terminal also works seamlessly on windows, which is why the ability
" Author: Bram Moolenaar
" Copyright: Vim license applies, see ":help license"

" In case this gets sourced twice.
if exists(':Termdebug')
  finish
endif

" The terminal feature does not work with gdb on win32.
if !has('win32')
  let s:way = 'terminal'
else
  let s:way = 'prompt'
endif

let s:keepcpo = &cpo
set cpo&vim

" The command that starts debugging, e.g. ":Termdebug vim".
" To end type "quit" in the gdb window.
command -nargs=* -complete=file -bang Termdebug call s:StartDebug(<bang>0, <f-args>)
command -nargs=+ -complete=file -bang TermdebugCommand call s:StartDebugCommand(<bang>0, <f-args>)

" Name of the gdb command, defaults to "gdb".
if !exists('g:termdebugger')
  let g:termdebugger = 'gdb'
endif

let s:pc_id = 12
let s:break_id = 13  " breakpoint number is added to this
let s:stopped = 1

" Take a breakpoint number as used by GDB and turn it into an integer.
" The breakpoint may contain a dot: 123.4 -> 123004
" The main breakpoint has a zero subid.
func s:Breakpoint2SignNumber(id, subid)
  return s:break_id + a:id * 1000 + a:subid
endfunction

func s:Highlight(init, old, new)
  let default = a:init ? 'default ' : ''
  if a:new ==# 'light' && a:old !=# 'light'
    exe "hi " . default . "debugPC term=reverse ctermbg=lightblue guibg=lightblue"
  elseif a:new ==# 'dark' && a:old !=# 'dark'
    exe "hi " . default . "debugPC term=reverse ctermbg=darkblue guibg=darkblue"
  endif
endfunc

call s:Highlight(1, '', &background)
hi default debugBreakpoint term=reverse ctermbg=red guibg=red

func s:StartDebug(bang, ...)
  " First argument is the command to debug, second core file or process ID.
  call s:StartDebug_internal({'gdb_args': a:000, 'bang': a:bang})
endfunc

func s:StartDebugCommand(bang, ...)
  " First argument is the command to debug, rest are run arguments.
  call s:StartDebug_internal({'gdb_args': [a:1], 'proc_args': a:000[1:], 'bang': a:bang})
endfunc

func s:StartDebug_internal(dict)
  if exists('s:gdbwin')
    echoerr 'Terminal debugger already running, cannot run two'
    return
  endif
  if !executable(g:termdebugger)
    echoerr 'Cannot execute debugger program "' .. g:termdebugger .. '"'
    return
  endif

  let s:ptywin = 0
  let s:pid = 0

  " Uncomment this line to write logging in "debuglog".
  " call ch_logfile('debuglog', 'w')

  let s:sourcewin = win_getid(winnr())
  let s:startsigncolumn = &signcolumn

  let s:save_columns = 0
  let s:allleft = 0
  if exists('g:termdebug_wide')
    if &columns < g:termdebug_wide
      let s:save_columns = &columns
      let &columns = g:termdebug_wide
      " If we make the Vim window wider, use the whole left halve for the debug
      " windows.
      let s:allleft = 1
    endif
    let s:vertical = 1
  else
    let s:vertical = 0
  endif

  " Override using a terminal window by setting g:termdebug_use_prompt to 1.
  let use_prompt = exists('g:termdebug_use_prompt') && g:termdebug_use_prompt
  if !has('win32') && !use_prompt
    let s:way = 'terminal'
   else
    let s:way = 'prompt'
   endif

  if s:way == 'prompt'
    call s:StartDebug_prompt(a:dict)
  else
    call s:StartDebug_term(a:dict)
  endif
endfunc

" Use when debugger didn't start or ended.
func s:CloseBuffers()
  exe 'bwipe! ' . s:ptybuf
  unlet! s:gdbwin
endfunc

func s:StartDebug_term(dict)
  " Open a terminal window without a job, to run the debugged program in.
  execute s:vertical ? 'vnew' : 'new'
  let s:pty_job_id = termopen('tail -f /dev/null;#gdb program')
  if s:pty_job_id == 0
    echoerr 'invalid argument (or job table is full) while opening terminal window'
    return
  elseif s:pty_job_id == -1
    echoerr 'Failed to open the program terminal window'
    return
  endif
  let pty_job_info = nvim_get_chan_info(s:pty_job_id)
  let s:ptybuf = pty_job_info['buffer']
  let pty = pty_job_info['pty']
  let s:ptywin = win_getid(winnr())
  if s:vertical
    " Assuming the source code window will get a signcolumn, use two more
    " columns for that, thus one less for the terminal window.
    exe (&columns / 2 - 1) . "wincmd |"
    if s:allleft
      " use the whole left column
      wincmd H
    endif
  endif

  " Create a hidden terminal window to communicate with gdb
  let s:comm_job_id = jobstart('tail -f /dev/null;#gdb communication', {
        \ 'on_stdout': function('s:CommOutput'),
        \ 'pty': v:true,
        \ })
  " hide terminal buffer
  if s:comm_job_id == 0
    echoerr 'invalid argument (or job table is full) while opening communication terminal window'
    exe 'bwipe! ' . s:ptybuf
    return
  elseif s:comm_job_id == -1
    echoerr 'Failed to open the communication terminal window'
    exe 'bwipe! ' . s:ptybuf
    return
  endif
  let comm_job_info = nvim_get_chan_info(s:comm_job_id)
  let commpty = comm_job_info['pty']

  " Open a terminal window to run the debugger.
  " Add -quiet to avoid the intro message causing a hit-enter prompt.
  let gdb_args = get(a:dict, 'gdb_args', [])
  let proc_args = get(a:dict, 'proc_args', [])

  let cmd = [g:termdebugger, '-quiet', '-tty', pty] + gdb_args
  "call ch_log('executing "' . join(cmd) . '"')
  execute 'new'
  let s:gdb_job_id = termopen(cmd, {'on_exit': function('s:EndTermDebug')})
  if s:gdb_job_id == 0
    echoerr 'invalid argument (or job table is full) while opening gdb terminal window'
    exe 'bwipe! ' . s:ptybuf
    return
  elseif s:gdb_job_id == -1
    echoerr 'Failed to open the gdb terminal window'
    call s:CloseBuffers()
    return
  endif
  let gdb_job_info = nvim_get_chan_info(s:gdb_job_id)
  let s:gdbbuf = gdb_job_info['buffer']
  let s:gdbwin = win_getid(winnr())

  " Set arguments to be run
  if len(proc_args)
    call chansend(s:gdb_job_id, 'set args ' . join(proc_args) . "\r")
  endif

  " Connect gdb to the communication pty, using the GDB/MI interface
  call chansend(s:gdb_job_id, 'new-ui mi ' . commpty . "\r")

  " Wait for the response to show up, users may not notice the error and wonder
  " why the debugger doesn't work.
  let try_count = 0
  while 1
    if nvim_get_chan_info(s:gdb_job_id) == {}
      echoerr string(g:termdebugger) . ' exited unexpectedly'
      call s:CloseBuffers()
      return
    endif

    let response = ''
    for lnum in range(1,200)
      if len(getbufline(s:gdbbuf, lnum)) > 0 && getbufline(s:gdbbuf, lnum)[0] =~ 'new-ui mi '
        " response can be in the same line or the next line
        let response = getbufline(s:gdbbuf, lnum)[0] . getbufline(s:gdbbuf, lnum + 1)[0]
        if response =~ 'Undefined command'
          echoerr 'Sorry, your gdb is too old, gdb 7.12 is required'
	  call s:CloseBuffers()
          return
        endif
        if response =~ 'New UI allocated'
          " Success!
          break
        endif
        if response =~ 'Reading symbols from' && response !~ 'new-ui'
          " Reading symbols might take a while
	  let try_count -= 1
        endif
      endif
    endfor
    if response =~ 'New UI allocated'
      break
    endif
    let try_count += 1
    if try_count > 100
      echoerr 'Cannot check if your gdb works, continuing anyway'
      break
    endif
    sleep 10m
  endwhile

  " Interpret commands while the target is running.  This should usualy only be
  " exec-interrupt, since many commands don't work properly while the target is
  " running.
  call s:SendCommand('-gdb-set mi-async on')
  " Older gdb uses a different command.
  call s:SendCommand('-gdb-set target-async on')

  " Disable pagination, it causes everything to stop at the gdb
  " "Type <return> to continue" prompt.
  call s:SendCommand('set pagination off')

  call s:StartDebugCommon(a:dict)
endfunc

func s:StartDebug_prompt(dict)
  " Open a window with a prompt buffer to run gdb in.
  if s:vertical
    vertical new
  else
    new
  endif
  let s:gdbwin = win_getid(winnr())
  let s:promptbuf = bufnr('')
  call prompt_setprompt(s:promptbuf, 'gdb> ')
  set buftype=prompt
  file gdb
  call prompt_setcallback(s:promptbuf, function('s:PromptCallback'))
  call prompt_setinterrupt(s:promptbuf, function('s:PromptInterrupt'))

  if s:vertical
    " Assuming the source code window will get a signcolumn, use two more
    " columns for that, thus one less for the terminal window.
    exe (&columns / 2 - 1) . "wincmd |"
  endif

  " Add -quiet to avoid the intro message causing a hit-enter prompt.
  let gdb_args = get(a:dict, 'gdb_args', [])
  let proc_args = get(a:dict, 'proc_args', [])

  let cmd = [g:termdebugger, '-quiet', '--interpreter=mi2'] + gdb_args
  "call ch_log('executing "' . join(cmd) . '"')

  let s:gdbjob = jobstart(cmd, {
	\ 'on_exit': function('s:EndPromptDebug'),
	\ 'on_stdout': function('s:GdbOutCallback'),
	\ })
  if s:gdbjob == 0
    echoerr 'invalid argument (or job table is full) while starting gdb job'
    exe 'bwipe! ' . s:ptybuf
    return
  elseif s:gdbjob == -1
    echoerr 'Failed to start the gdb job'
    call s:CloseBuffers()
    return
  endif

  " Interpret commands while the target is running.  This should usualy only
  " be exec-interrupt, since many commands don't work properly while the
  " target is running.
  call s:SendCommand('-gdb-set mi-async on')
  " Older gdb uses a different command.
  call s:SendCommand('-gdb-set target-async on')

  let s:ptybuf = 0
  if has('win32')
    " MS-Windows: run in a new console window for maximum compatibility
    call s:SendCommand('set new-console on')
  else
    " Unix: Run the debugged program in a terminal window.  Open it below the
    " gdb window.
    execute 'new'
    wincmd x | wincmd j
    belowright let s:pty_job_id = termopen('tail -f /dev/null;#gdb program')
    if s:pty_job_id == 0
      echoerr 'invalid argument (or job table is full) while opening terminal window'
      return
    elseif s:pty_job_id == -1
      echoerr 'Failed to open the program terminal window'
      return
    endif
    let pty_job_info = nvim_get_chan_info(s:pty_job_id)
    let s:ptybuf = pty_job_info['buffer']
    let pty = pty_job_info['pty']
    let s:ptywin = win_getid(winnr())
    call s:SendCommand('tty ' . pty)

    " Since GDB runs in a prompt window, the environment has not been set to
    " match a terminal window, need to do that now.
    call s:SendCommand('set env TERM = xterm-color')
    call s:SendCommand('set env ROWS = ' . winheight(s:ptywin))
    call s:SendCommand('set env LINES = ' . winheight(s:ptywin))
    call s:SendCommand('set env COLUMNS = ' . winwidth(s:ptywin))
    call s:SendCommand('set env COLORS = ' . &t_Co)
    call s:SendCommand('set env VIM_TERMINAL = ' . v:version)
  endif
  call s:SendCommand('set print pretty on')
  call s:SendCommand('set breakpoint pending on')
  " Disable pagination, it causes everything to stop at the gdb
  call s:SendCommand('set pagination off')

  " Set arguments to be run
  if len(proc_args)
    call s:SendCommand('set args ' . join(proc_args))
  endif

  call s:StartDebugCommon(a:dict)
  startinsert
endfunc

func s:StartDebugCommon(dict)
  " Sign used to highlight the line where the program has stopped.
  " There can be only one.
  sign define debugPC linehl=debugPC

  " Install debugger commands in the text window.
  call win_gotoid(s:sourcewin)
  call s:InstallCommands()
  call win_gotoid(s:gdbwin)

  " Contains breakpoints that have been placed, key is a string with the GDB
  " breakpoint number.
  " Each entry is a dict, containing the sub-breakpoints.  Key is the subid.
  " For a breakpoint that is just a number the subid is zero.
  " For a breakpoint "123.4" the id is "123" and subid is "4".
  " Example, when breakpoint "44", "123", "123.1" and "123.2" exist:
  " {'44': {'0': entry}, '123': {'0': entry, '1': entry, '2': entry}}
  let s:breakpoints = {}

  " Contains breakpoints by file/lnum.  The key is "fname:lnum".
  " Each entry is a list of breakpoint IDs at that position.
  let s:breakpoint_locations = {}

  augroup TermDebug
    au BufRead * call s:BufRead()
    au BufUnload * call s:BufUnloaded()
    au OptionSet background call s:Highlight(0, v:option_old, v:option_new)
  augroup END

  " Run the command if the bang attribute was given and got to the debug
  " window.
  if get(a:dict, 'bang', 0)
    call s:SendCommand('-exec-run')
    call win_gotoid(s:ptywin)
  endif
endfunc

" Send a command to gdb.  "cmd" is the string without line terminator.
func s:SendCommand(cmd)
  "call ch_log('sending to gdb: ' . a:cmd)
  if s:way == 'prompt'
    call chansend(s:gdbjob, a:cmd . "\n")
  else
    call chansend(s:comm_job_id, a:cmd . "\r")
  endif
endfunc

" This is global so that a user can create their mappings with this.
func TermDebugSendCommand(cmd)
  if s:way == 'prompt'
    call chansend(s:gdbjob, a:cmd . "\n")
  else
    let do_continue = 0
    if !s:stopped
      let do_continue = 1
      if s:way == 'prompt'
        " Need to send a signal to get the UI to listen.  Strangely this is only
        " needed once.
        call jobstop(s:gdbjob)
      else
        call s:SendCommand('-exec-interrupt')
      endif
      sleep 10m
    endif
    call chansend(s:gdb_job_id, a:cmd . "\r")
    if do_continue
      Continue
    endif
  endif
endfunc

" Function called when entering a line in the prompt buffer.
func s:PromptCallback(text)
  call s:SendCommand(a:text)
endfunc

" Function called when pressing CTRL-C in the prompt buffer.
func s:PromptInterrupt()
  "call ch_log('Interrupting gdb')
  call system('kill -SIGINT ' . s:pid)
endfunc

" Function called when gdb outputs text.
func s:GdbOutCallback(job_id, msgs, event)
  "call ch_log('received from gdb: ' . a:text)

  " Drop the gdb prompt, we have our own.
  " Drop status and echo'd commands.
  call filter(a:msgs, { index, val ->
        \ val !=# '(gdb)' && val !=# '^done' && val[0] !=# '&'})

  let lines = []
  let index = 0

  for msg in a:msgs
    if msg =~ '^^error,msg='
      if exists('s:evalexpr')
            \ && s:DecodeMessage(msg[11:])
            \    =~ 'A syntax error in expression, near\|No symbol .* in current context'
        " Silently drop evaluation errors.
        call remove(a:msgs, index)
        unlet s:evalexpr
        continue
      endif
    elseif msg[0] == '~'
      call add(lines, s:DecodeMessage(msg[1:]))
      call remove(a:msgs, index)
      continue
    endif
    let index += 1
  endfor

  let curwinid = win_getid(winnr())
  call win_gotoid(s:gdbwin)

  " Add the output above the current prompt.
  for line in lines
    call append(line('$') - 1, line)
  endfor
  if !empty(lines)
    set modified
  endif

  call win_gotoid(curwinid)
  call s:CommOutput(a:job_id, a:msgs, a:event)
endfunc

" Decode a message from gdb.  quotedText starts with a ", return the text up
" to the next ", unescaping characters.
func s:DecodeMessage(quotedText)
  if a:quotedText[0] != '"'
    echoerr 'DecodeMessage(): missing quote in ' . a:quotedText
    return
  endif
  let result = ''
  let i = 1
  while a:quotedText[i] != '"' && i < len(a:quotedText)
    if a:quotedText[i] == '\'
      let i += 1
      if a:quotedText[i] == 'n'
        " drop \n
        let i += 1
        continue
      endif
    endif
    let result .= a:quotedText[i]
    let i += 1
  endwhile
  return result
endfunc

" Extract the "name" value from a gdb message with fullname="name".
func s:GetFullname(msg)
  if a:msg !~ 'fullname'
    return ''
  endif
  let name = s:DecodeMessage(substitute(a:msg, '.*fullname=', '', ''))
  if has('win32') && name =~ ':\\\\'
    " sometimes the name arrives double-escaped
    let name = substitute(name, '\\\\', '\\', 'g')
  endif
  return name
endfunc

function s:EndTermDebug(job_id, exit_code, event)
  unlet s:gdbwin

  call s:EndDebugCommon()
endfunc

func s:EndDebugCommon()
  let curwinid = win_getid(winnr())

  if exists('s:ptybuf') && s:ptybuf
    exe 'bwipe! ' . s:ptybuf
  endif

  call win_gotoid(s:sourcewin)
  let &signcolumn = s:startsigncolumn
  call s:DeleteCommands()

  call win_gotoid(curwinid)

  if s:save_columns > 0
    let &columns = s:save_columns
  endif

  au! TermDebug
endfunc

func s:EndPromptDebug(job_id, exit_code, event)
  let curwinid = win_getid(winnr())
  call win_gotoid(s:gdbwin)
  close
  if curwinid != s:gdbwin
    call win_gotoid(curwinid)
  endif

  call s:EndDebugCommon()
  unlet s:gdbwin
  "call ch_log("Returning from EndPromptDebug()")
endfunc

func s:CommOutput(job_id, msgs, event)

  for msg in a:msgs
    " remove prefixed NL
    if msg[0] == "\n"
      let msg = msg[1:]
    endif
    if msg != ''
      if msg =~ '^\(\*stopped\|\*running\|=thread-selected\)'
        call s:HandleCursor(msg)
      elseif msg =~ '^\^done,bkpt=' || msg =~ '^=breakpoint-created,'
        call s:HandleNewBreakpoint(msg)
      elseif msg =~ '^=breakpoint-deleted,'
        call s:HandleBreakpointDelete(msg)
      elseif msg =~ '^=thread-group-started'
        call s:HandleProgramRun(msg)
      elseif msg =~ '^\^done,value='
        call s:HandleEvaluate(msg)
      elseif msg =~ '^\^error,msg='
        call s:HandleError(msg)
      endif
    endif
  endfor
endfunc

" Install commands in the current window to control the debugger.
func s:InstallCommands()
  let save_cpo = &cpo
  set cpo&vim

  command Break call s:SetBreakpoint()
  command Clear call s:ClearBreakpoint()
  command Step call s:SendCommand('-exec-step')
  command Over call s:SendCommand('-exec-next')
  command Finish call s:SendCommand('-exec-finish')
  command -nargs=* Run call s:Run(<q-args>)
  command -nargs=* Arguments call s:SendCommand('-exec-arguments ' . <q-args>)
  command Stop call s:SendCommand('-exec-interrupt')

  " using -exec-continue results in CTRL-C in gdb window not working
  if s:way == 'prompt'
    command Continue call s:SendCommand('continue')
  else
    command Continue call chansend(s:gdb_job_id, "continue\r")
  endif

  command -range -nargs=* Evaluate call s:Evaluate(<range>, <q-args>)
  command Gdb call win_gotoid(s:gdbwin)
  command Program call win_gotoid(s:ptywin)
  command Source call s:GotoSourcewinOrCreateIt()
  " command Winbar call s:InstallWinbar()

  " TODO: can the K mapping be restored?
  nnoremap K :Evaluate<CR>

  let &cpo = save_cpo
endfunc

" let s:winbar_winids = []

" Delete installed debugger commands in the current window.
func s:DeleteCommands()
  delcommand Break
  delcommand Clear
  delcommand Step
  delcommand Over
  delcommand Finish
  delcommand Run
  delcommand Arguments
  delcommand Stop
  delcommand Continue
  delcommand Evaluate
  delcommand Gdb
  delcommand Program
  delcommand Source
  " delcommand Winbar

  nunmap K

  exe 'sign unplace ' . s:pc_id
  for [id, entries] in items(s:breakpoints)
    for subid in keys(entries)
      exe 'sign unplace ' . s:Breakpoint2SignNumber(id, subid)
    endfor
  endfor
  unlet s:breakpoints
  unlet s:breakpoint_locations

  sign undefine debugPC
  for val in s:BreakpointSigns
    exe "sign undefine debugBreakpoint" . val
  endfor
  let s:BreakpointSigns = []
endfunc

" :Break - Set a breakpoint at the cursor position.
func s:SetBreakpoint()
  " Setting a breakpoint may not work while the program is running.
  " Interrupt to make it work.
  let do_continue = 0
  if !s:stopped
    let do_continue = 1
    call s:SendCommand('-exec-interrupt')
    sleep 10m
  endif
  " Use the fname:lnum format, older gdb can't handle --source.
  call s:SendCommand('-break-insert '
        \ . fnameescape(expand('%:p')) . ':' . line('.'))
  if do_continue
    call s:SendCommand('-exec-continue')
  endif
endfunc

" :Clear - Delete a breakpoint at the cursor position.
func s:ClearBreakpoint()
  let fname = fnameescape(expand('%:p'))
  let lnum = line('.')
  let bploc = printf('%s:%d', fname, lnum)
  if has_key(s:breakpoint_locations, bploc)
    let idx = 0
    for id in s:breakpoint_locations[bploc]
      if has_key(s:breakpoints, id)
        " Assume this always works, the reply is simply "^done".
        call s:SendCommand('-break-delete ' . id)
        for subid in keys(s:breakpoints[id])
          exe 'sign unplace ' . s:Breakpoint2SignNumber(id, subid)
        endfor
        unlet s:breakpoints[id]
        unlet s:breakpoint_locations[bploc][idx]
        break
      else
	let idx += 1
      endif
    endfor
    if empty(s:breakpoint_locations[bploc])
      unlet s:breakpoint_locations[bploc]
    endif
  endif
endfunc

func s:Run(args)
  if a:args != ''
    call s:SendCommand('-exec-arguments ' . a:args)
  endif
  call s:SendCommand('-exec-run')
endfunc

func s:SendEval(expr)
  call s:SendCommand('-data-evaluate-expression "' . a:expr . '"')
  let s:evalexpr = a:expr
endfunc

" :Evaluate - evaluate what is under the cursor
func s:Evaluate(range, arg)
  if a:arg != ''
    let expr = a:arg
    let s:evalFromBalloonExpr = 0
  elseif a:range == 2
    let pos = getcurpos()
    let reg = getreg('v', 1, 1)
    let regt = getregtype('v')
    normal! gv"vy
    let expr = @v
    call setpos('.', pos)
    call setreg('v', reg, regt)
    let s:evalFromBalloonExpr = 1
  else
    let expr = expand('<cexpr>')
    let s:evalFromBalloonExpr = 1
  endif
  let s:ignoreEvalError = 0
  call s:SendEval(expr)
endfunc

let s:ignoreEvalError = 0
let s:evalFromBalloonExpr = 0
let s:evalFromBalloonExprResult = ''

" Handle the result of data-evaluate-expression
func s:HandleEvaluate(msg)
  let value = substitute(a:msg, '.*value="\(.*\)"', '\1', '')
  let value = substitute(value, '\\"', '"', 'g')
  let value = substitute(value, '
', '\1', '')
  if s:evalFromBalloonExpr
    if s:evalFromBalloonExprResult == ''
      let s:evalFromBalloonExprResult = s:evalexpr . ': ' . value
    else
      let s:evalFromBalloonExprResult .= ' = ' . value
    endif
    let s:evalFromBalloonExprResult = split(s:evalFromBalloonExprResult, '\\n')
    call s:OpenHoverPreview(s:evalFromBalloonExprResult, v:null)
    let s:evalFromBalloonExprResult = ''
  else
    echomsg '"' . s:evalexpr . '": ' . value
  endif

  if s:evalexpr[0] != '*' && value =~ '^0x' && value != '0x0' && value !~ '"$'
    " Looks like a pointer, also display what it points to.
    let s:ignoreEvalError = 1
    call s:SendEval('*' . s:evalexpr)
  else
    let s:evalFromBalloonExprResult = ''
  endif
endfunc

function! s:ShouldUseFloatWindow() abort
  if exists('*nvim_open_win') && (get(g:, 'termdebug_useFloatingHover', 1) == 1)
    return v:true
  else
    return v:false
  endif
endfunction

function! s:CloseFloatingHoverOnCursorMove(win_id, opened) abort
  if getpos('.') == a:opened
    " Just after opening floating window, CursorMoved event is run.
    " To avoid closing floating window immediately, check the cursor
    " was really moved
    return
  endif
  autocmd! nvim_termdebug_close_hover
  let winnr = win_id2win(a:win_id)
  if winnr == 0
    return
  endif
  call nvim_win_close(a:win_id, v:true)
endfunction

function! s:CloseFloatingHoverOnBufEnter(win_id, bufnr) abort
    let winnr = win_id2win(a:win_id)
    if winnr == 0
        " Float window was already closed
        autocmd! nvim_termdebug_close_hover
        return
    endif
    if winnr == winnr()
        " Cursor is moving into floating window. Do not close it
        return
    endif
    if bufnr('%') == a:bufnr
        " When current buffer opened hover window, it's not another buffer. Skipped
        return
    endif
    autocmd! nvim_termdebug_close_hover
    call nvim_win_close(a:win_id, v:true)
  endfunction

" Open preview window. Window is open in:
"   - Floating window on Neovim (0.4.0 or later)
"   - Preview window on Neovim (0.3.0 or earlier) or Vim
function! s:OpenHoverPreview(lines, filetype) abort
    " Use local variable since parameter is not modifiable
    let lines = a:lines
    let bufnr = bufnr('%')

    let use_float_win = s:ShouldUseFloatWindow()
    if use_float_win
      let pos = getpos('.')

      " Calculate width and height
      let width = 0
      for index in range(len(lines))
        let line = lines[index]
        let lw = strdisplaywidth(line)
        if lw > width
          let width = lw
        endif
        let lines[index] = line
      endfor

      let height = len(lines)

      " Calculate anchor
      " Prefer North, but if there is no space, fallback into South
      let bottom_line = line('w0') + winheight(0) - 1
      if pos[1] + height <= bottom_line
        let vert = 'N'
        let row = 1
      else
        let vert = 'S'
        let row = 0
      endif

      " Prefer West, but if there is no space, fallback into East
      if pos[2] + width <= &columns
        let hor = 'W'
        let col = 0
      else
        let hor = 'E'
        let col = 1
      endif

      let buf = nvim_create_buf(v:false, v:true)
      call nvim_buf_set_lines(buf, 0, -1, v:true, lines)
      " using v:true for second argument of nvim_open_win make the floating
      " window disappear
      let float_win_id = nvim_open_win(buf, v:false, {
            \   'relative': 'cursor',
            \   'anchor': vert . hor,
            \   'row': row,
            \   'col': col,
            \   'width': width,
            \   'height': height,
            \   'style': 'minimal',
            \ })

      if a:filetype isnot v:null
        call nvim_win_set_option(float_win_id, 'filetype', a:filetype)
      endif

      call nvim_buf_set_option(buf, 'modified', v:false)
      call nvim_buf_set_option(buf, 'modifiable', v:false)

      " Unlike preview window, :pclose does not close window. Instead, close
      " hover window automatically when cursor is moved.
      let call_after_move = printf('<SID>CloseFloatingHoverOnCursorMove(%d, %s)', float_win_id, string(pos))
      let call_on_bufenter = printf('<SID>CloseFloatingHoverOnBufEnter(%d, %d)', float_win_id, bufnr)
      augroup nvim_termdebug_close_hover
        execute 'autocmd CursorMoved,CursorMovedI,InsertEnter <buffer> call ' . call_after_move
        execute 'autocmd BufEnter * call ' . call_on_bufenter
      augroup END
    else
      echomsg a:lines[0]
    endif
endfunction

" Handle an error.
func s:HandleError(msg)
  if s:ignoreEvalError
    " Result of s:SendEval() failed, ignore.
    let s:ignoreEvalError = 0
    let s:evalFromBalloonExpr = 0
    return
  endif
  echoerr substitute(a:msg, '.*msg="\(.*\)"', '\1', '')
endfunc

func s:GotoSourcewinOrCreateIt()
  if !win_gotoid(s:sourcewin)
    new
    let s:sourcewin = win_getid(winnr())
    " call s:InstallWinbar()
  endif
endfunc

" Handle stopping and running message from gdb.
" Will update the sign that shows the current position.
func s:HandleCursor(msg)
  let wid = win_getid(winnr())

  if a:msg =~ '^\*stopped'
    "call ch_log('program stopped')
    let s:stopped = 1
  elseif a:msg =~ '^\*running'
    "call ch_log('program running')
    let s:stopped = 0
  endif

  if a:msg =~ 'fullname='
    let fname = s:GetFullname(a:msg)
  else
    let fname = ''
  endif
  if a:msg =~ '^\(\*stopped\|=thread-selected\)' && filereadable(fname)
    let lnum = substitute(a:msg, '.*line="\([^"]*\)".*', '\1', '')
    if lnum =~ '^[0-9]*$'
   call s:GotoSourcewinOrCreateIt()
      if expand('%:p') != fnamemodify(fname, ':p')
        if &modified
          " TODO: find existing window
          exe 'split ' . fnameescape(fname)
          let s:sourcewin = win_getid(winnr())
          " call s:InstallWinbar()
        else
          exe 'edit ' . fnameescape(fname)
        endif
      endif
      exe lnum
      exe 'sign unplace ' . s:pc_id
      exe 'sign place ' . s:pc_id . ' line=' . lnum . ' name=debugPC file=' . fname
      setlocal signcolumn=yes
    endif
  elseif !s:stopped || fname != ''
    exe 'sign unplace ' . s:pc_id
  endif

  call win_gotoid(wid)
endfunc

let s:BreakpointSigns = []

func s:CreateBreakpoint(id, subid)
  let nr = printf('%d.%d', a:id, a:subid)
  if index(s:BreakpointSigns, nr) == -1
    call add(s:BreakpointSigns, nr)
    exe "sign define debugBreakpoint" . nr . " text=" . substitute(nr, '\..*', '', '') . " texthl=debugBreakpoint"
  endif
endfunc

func! s:SplitMsg(s)
  return split(a:s, '{.\{-}}\zs')
endfunction

" Handle setting a breakpoint
" Will update the sign that shows the breakpoint
func s:HandleNewBreakpoint(msg)
  if a:msg !~ 'fullname='
    " a watch does not have a file name
    return
  endif
  for msg in s:SplitMsg(a:msg)
    let fname = s:GetFullname(msg)
    if empty(fname)
      continue
    endif
    let nr = substitute(msg, '.*number="\([0-9.]*\)\".*', '\1', '')
    if empty(nr)
      return
    endif

    " If "nr" is 123 it becomes "123.0" and subid is "0".
    " If "nr" is 123.4 it becomes "123.4.0" and subid is "4"; "0" is discarded.
    let [id, subid; _] = map(split(nr . '.0', '\.'), 'v:val + 0')
    call s:CreateBreakpoint(id, subid)

    if has_key(s:breakpoints, id)
      let entries = s:breakpoints[id]
    else
      let entries = {}
      let s:breakpoints[id] = entries
    endif
    if has_key(entries, subid)
      let entry = entries[subid]
    else
      let entry = {}
      let entries[subid] = entry
    endif

    let lnum = substitute(msg, '.*line="\([^"]*\)".*', '\1', '')
    let entry['fname'] = fname
    let entry['lnum'] = lnum

    let bploc = printf('%s:%d', fname, lnum)
    if !has_key(s:breakpoint_locations, bploc)
      let s:breakpoint_locations[bploc] = []
    endif
    let s:breakpoint_locations[bploc] += [id]

    if bufloaded(fname)
      call s:PlaceSign(id, subid, entry)
    endif
  endfor
endfunc

func s:PlaceSign(id, subid, entry)
  let nr = printf('%d.%d', a:id, a:subid)
  exe 'sign place ' . s:Breakpoint2SignNumber(a:id, a:subid) . ' line=' . a:entry['lnum'] . ' name=debugBreakpoint' . nr . ' file=' . a:entry['fname']
  let a:entry['placed'] = 1
endfunc

" Handle deleting a breakpoint
" Will remove the sign that shows the breakpoint
func s:HandleBreakpointDelete(msg)
  let id = substitute(a:msg, '.*id="\([0-9]*\)\".*', '\1', '') + 0
  if empty(id)
    return
  endif
  if has_key(s:breakpoints, id)
    for [subid, entry] in items(s:breakpoints[id])
      if has_key(entry, 'placed')
        exe 'sign unplace ' . s:Breakpoint2SignNumber(id, subid)
        unlet entry['placed']
      endif
    endfor
    unlet s:breakpoints[id]
  endif
endfunc

" Handle the debugged program starting to run.
" Will store the process ID in s:pid
func s:HandleProgramRun(msg)
  let nr = substitute(a:msg, '.*pid="\([0-9]*\)\".*', '\1', '') + 0
  if nr == 0
    return
  endif
  let s:pid = nr
  "call ch_log('Detected process ID: ' . s:pid)
endfunc

" Handle a BufRead autocommand event: place any signs.
func s:BufRead()
  let fname = expand('<afile>:p')
  for [id, entries] in items(s:breakpoints)
    for [subid, entry] in items(entries)
      if entry['fname'] == fname
        call s:PlaceSign(id, subid, entry)
      endif
    endfor
  endfor
endfunc

" Handle a BufUnloaded autocommand event: unplace any signs.
func s:BufUnloaded()
  let fname = expand('<afile>:p')
  for [id, entries] in items(s:breakpoints)
    for [subid, entry] in items(entries)
      if entry['fname'] == fname
        let entry['placed'] = 0
      endif
    endfor
  endfor
endfunc

let &cpo = s:keepcpo
unlet s:keepcpo