" A fundamental question for this plugin is whether insertmode
" is always relevant. This is where we try to get an answer.
function! s:IsEditableBuffer()
  if &buftype ==# 'nofile'
     \|| !&modifiable
     \|| &readonly
     \|| bufname('%') =~# 'NERD_tree_'
    return 0
  else
    return 1
  endif
endfunction

" Make sure insert mode is the default mode only when opening/switching
" to files that you want to edit.
function! s:InsertMode()
  if s:IsEditableBuffer() == 1
    exe "set insertmode"
  else
    exe "set noinsertmode"
  endif
endfunction

" Count number of open buffers. They don't have to be visible.
function! s:CountListedBuffers()
  let bfr_count = 0
  for bfr in range(1, bufnr("$"))
    if buflisted(bfr)
       \&& ! empty(bufname(bfr))
       \|| getbufvar(bfr, '&buftype') ==# 'help'
       let bfr_count += 1
    endif
  endfor
  return bfr_count
endfunction

" The number of visible lines in the current buffer.
" TODO: Include wrapped lines in the total, so that we can start scrolling
"       through *visible* lines rather than file lines.
function! s:BufferLines()
  return line('w$') - line('w0')
endfunction

function! s:InsertAndSelectionBehaviour()
  " Intelligently set/unset insertmode
  augroup start_insertmode
    autocmd!
    autocmd BufEnter * call s:InsertMode()
  augroup END

  " Mostly changes the way selection works.
  " See: http://vimdoc.sourceforge.net/htmldoc/gui.html#:behave
  " An extract from the docs about the difference between `behave mswin`
  " and `behave xterm`:
  "               mswin              xterm
  "  'selectmode' 'mouse,key'        ''
  "  'mousemodel' 'popup'            'extend'
  "  'keymodel'   'startsel,stopsel' ''
  "  'selection'  'exclusive'        'inclusive'
  behave mswin

  " Make 'v' commands default to Visual mode.
  " Not sure how useful this is because the mappings that use 'v'-based
  " commands don't seem to follow this option. Thus why you will see <C-G>
  " after some selection-based commands to switch from Visual to Selection
  " Mode. So might be better to give experienced users who are pressing
  " 'v' in normal mode the expected behaviour.
  set selectmode+=cmd
endfunction

" All shortcuts in one function so they can be more easily controlled.
function! g:SetNoVimModeShortcuts()
  " Basic interactions with the editor
  if g:novim_mode_use_general_app_shortcuts == 1
    " CTRL+q to completely exit vim
    inoremap <silent> <C-Q> <C-O>:call novim_mode#ExitVim()<CR>
    snoremap <silent> <C-Q> <C-O>:call novim_mode#ExitVim()<CR>
    nnoremap <silent> <C-Q> :call novim_mode#ExitVim()<CR>

    " CTRL+n for new file
    inoremap <C-N> <C-O>:edit<Space>
    " CTRL+o to open file
    " TODO: hook into netrw or NERDTree
    inoremap <C-O> <C-O>:edit<Space>
    " CTRL+s saves
    inoremap <silent> <C-S> <C-O>:update<CR>

    " Goto line number
    inoremap <C-G> <C-O>:call novim_mode#GotoLine()<CR>

    " ALT+; for command prompt
    inoremap <M-;> <C-O>:

    " <ALT+o> replaces native <C-O> for one-time normal mode commands.
    inoremap <M-o> <C-O>
    snoremap <M-o> <C-O>
  endif

  " General fixes to editor behaviour
  if g:novim_mode_use_editor_fixes == 1
    " Fix HOME to go back to the first non-whitespace character of the line
    inoremap <silent> <Home> <C-O>^

    " Tweaks PageUp behaviour to get cursor to first line on top page
    inoremap <silent> <PageUp> <C-O>:call novim_mode#PageUp()<CR>
  endif

  " Move between splits, panes, windows, etc and close them
  if g:novim_mode_use_pane_controls == 1
    inoremap <silent> <M-Left>  <C-O><C-W><Left>
    nnoremap <silent> <M-Left>  <C-W><Left>
    inoremap <silent> <M-Down>  <C-O><C-W><Down>
    nnoremap <silent> <M-Down>  <C-W><Down>
    inoremap <silent> <M-Up>    <C-O><C-W><Up>
    nnoremap <silent> <M-Up>    <C-W><Up>
    inoremap <silent> <M-Right> <C-O><C-W><Right>
    nnoremap <silent> <M-Right> <C-W><Right>

    " This allows unsaved buffers to be kept in the background.
    set hidden

    " CTRL+w to delete current pane-like things.
    inoremap <silent> <C-W> <C-O>:call novim_mode#ClosePane()<CR>
    snoremap <silent> <C-W> <C-O>:call novim_mode#ClosePane()<CR>
    nnoremap <silent> <C-W> :call novim_mode#ClosePane()<CR>
  end

  " Selecting, copy, paste, etc
  if g:novim_mode_use_copypasting == 1
    " One of those curious features of Vim: without `onemore` when pasting
    " at the end of a line, pasted text gets put *before* the cursor.
    set virtualedit=onemore
    " NB. All these use the named 'p' register.
    inoremap <C-V> <C-O>"pP
    snoremap <C-C> <C-O>"pyi
    inoremap <C-C> <C-O>"pY
    snoremap <C-X> <C-O>"pxi
    inoremap <C-X> <C-O>"pdd
    " Select word under cursor
    inoremap <C-D> <C-O>viw<C-G>
    " Select current line
    inoremap <C-L> <C-O>V<C-G>
    " Append next line to selection
    snoremap <C-L> <C-O>gj

    " CTRL-A for selecting all text
    inoremap <C-A> <C-O>gg<C-O>gH<C-O>G
    snoremap <C-A> <C-O><C-C>gggH<C-O>G
  endif

  " Indenting
  if g:novim_mode_use_indenting == 1
    " TODO: TAB doesn't work in mswin selection mode, but SHIFT+TAB does??
    snoremap <Tab> <C-O>>gv
    inoremap <M-]> <C-T>
    snoremap <M-]> <C-O>>gv
    " Unindenting
    snoremap <S-Tab> <C-O><gv
    inoremap <M-[> <C-D>
    snoremap <M-[> <C-O><gv
  endif

  if g:novim_mode_use_finding == 1
    " Find
    inoremap <C-F> <C-O>/
    " Find selected word under cursor
    snoremap <C-F> <C-O>y/<C-R>"<CR>
    " Find next
    inoremap <F3> <C-O>n
    " Find previous
    inoremap <S-F3> <C-O>N
    " Find and replace
    inoremap <C-H> <C-O>:%s/[FIND]/[REPLACE]/g
    " Clears highlighting.
    " NB. Overriding ESC makes it harder to get into NORMAL mode.
    inoremap <silent> <Esc> <C-O>:noh<CR>
  endif

  " Undo/redo
  if g:novim_mode_use_undoing == 1
    " Use <M-o><C-Z> for native terminal backgrounding.
    " The <Esc>s used in the `snoremap` commands seem to prevent the selection
    " process itself being put in the undo history - so now the undo actually undoes
    " the last *text* activity.
    inoremap <silent> <C-Z> <C-O>u
    snoremap <silent> <C-Z> <Esc><C-O>u
    " Map CTRL+u as well for now just because by default it deletes the line above
    " the cursor.
    inoremap <silent> <C-U> <C-O>u
    snoremap <silent> <C-U> <Esc><C-O>u
    " Redo
    inoremap <silent> <C-Y> <C-O><C-R>
    snoremap <silent> <C-Y> <Esc><C-O><C-R>
  endif

  " Useful, but not necessarily core or conventional, shortcuts for manipulating
  " text.
  if g:novim_mode_use_text_tricks == 1
    " CTRL+ALTt+k deletes the current line under the cursor
    inoremap <silent> <C-M-K> <C-O>"_dd

    " CTRL+ALT+d duplicates current line.
    " NB. Uses the named 'd' register.
    inoremap <silent> <C-M-D> <C-O>"dyy<C-O>"dp

    " CTRL+DOWN/UP moves the current/selected line(s) up and down
    inoremap <silent> <C-Up> <C-O>:m -2<CR>
    snoremap <silent> <C-Up> <C-O>:m '<-2<CR>gv=gv<C-G>
    inoremap <silent> <C-Down> <C-O>:m +1<CR>
    snoremap <silent> <C-Down> <C-O>:m '>+1<CR>gv=gv<C-G>
  endif
endfunction

" By default Vim treats wrapped text as a single line even though it may
" appear as many lines on screen. So here we try to make wrapped text behave
" more conventionally.
function! s:SetWrappedTextNavigation()
  " Allow text to wrap in text files
  au BufNewFile,BufRead *.txt,*.md,*.markdown setlocal linebreak spell

  " Make arrow keys move through wrapped lines
  " TODO:
  "   * Make END key move to end of current wrapped piece of line.
  "   * Scroll window 1 wrapped soft line at a time rather an entire block of wrapped
  "     lines.
  au BufNewFile,BufRead *.txt,*.md,*.markdown inoremap <buffer> <Up> <C-O>gk
  au BufNewFile,BufRead *.txt,*.md,*.markdown inoremap <buffer> <Down> <C-O>gj
endfunction

" Try to intuitively and intelligently close things like buffers, splits,
" panes, quicklist, etc, basically anything that looks like a pane.
function! novim_mode#ClosePane()
  if s:IsEditableBuffer() == 1
    " Close any location lists on screen.
    exe "lclose"
    " Close any quickfix lists on screen.
    exe "cclose"

    if s:CountListedBuffers() > 1
      " By default if the buffer is the only one on screen, closing it closes the
      " tab/window. So this little trick does a switch to the next buffer,
      " then closes the previous buffer.
      exe "bp\|bd #"
    else
      quit
    endif
  else
    quit
  endif
endfunction

" TODO: Mention any unsaved buffers
function! novim_mode#ExitVim()
  let l:confirmed = confirm('Do you really want to quit Vim?', "&Yes\n&No", 2)
  if l:confirmed == 1
    quitall!
  endif
endfunction

function! novim_mode#GotoLine()
  let l:line_number = input('Goto line: ')
  execute line_number
endfunction

" Just to get PAGEUP to move to the first line when on the first page.
function! novim_mode#PageUp()
  " If current line is higher than the size of the buffer
  if line(".") > s:BufferLines()
    " Normal PageUp
    execute "normal! \<C-b>"
  else
    " Goto first line
    execute "normal! gg"
  endif
endfunction

function! g:novim_mode#StartNoVimMode()
  call s:InsertAndSelectionBehaviour()

  if g:novim_mode_use_better_wrap_navigation == 1
    call s:SetWrappedTextNavigation()
  endif

  if g:novim_mode_use_shortcuts == 1
    call g:SetNoVimModeShortcuts()
  endif
endfunction