" Use VIM improved mode
set nocompatible


" Disable VIM's startup message
set shortmess+=I

" Number of remembered undo steps
set undolevels=1000


set runtimepath^=$XDG_CONFIG_HOME/vim
set runtimepath+=$XDG_CONFIG_HOME/vim/after

" Set environment variables for convenient usage
let $RC = expand('$XDG_CONFIG_HOME/vim/vimrc')
let $RTP=split(&runtimepath, ',')[0]


" Detect the file's type and load the corresponding plugin and indent files
filetype plugin indent on

" Enable syntax highlighting
syntax on


" Configure tab behavior
set expandtab      " Insert spaces instead of tab characters
set tabstop=4      " Width of an existing tab character
set shiftwidth=4   " Width of one >> or << indent step
set softtabstop=4  " Width inserted/removed by <tab> and <bs>
set shiftround     " Round indents to a multiple of shiftwidth
set autoindent     " Keep the previous line's indent on a new line
vnoremap <tab>    >gv
vnoremap <s-tab>  <gv


" Allow backspace to delete characters in insert mode
" beyond the start of the insertion and end of lines
set backspace=start,eol,indent


" Hide buffers instead of closing them, which means we can have
" unwritten changes to a file and open a new one with :e,
" without having to write the changes first
set hidden


" Set to the folder of the current file and its sub-folders
" (this may need to be adapted for large project folders)
set path=.,**


" Store all vim-related working files in the ~/.local/state/vim folder
set viminfo+=n$XDG_STATE_HOME/vim/viminfo
" Use dedicated folders to store temporary backup, swap, and undo files
" (the // means that VIM adapts names automatically to avoid duplicates)
set backupdir=$XDG_STATE_HOME/vim/backup//
set directory=$XDG_STATE_HOME/vim/swap//
set undodir=$XDG_STATE_HOME/vim/undo//
set undofile

" To disable any of the temporary files, uncomment one of the following
" set nobackup
" set nowritebackup
" set noswapfile
" set noundofile


" Show the filename in the terminal window's title bar
set title


" Do not wrap lines when showing text
set nowrap

" This avoids a problem of losing data upon insertion in old VIMs
set wrapmargin=0


" Show spelling mistakes in italics

augroup spelling
    autocmd!
    autocmd FileType markdown,text,gitcommit setlocal spell spelllang=en_us,de_de
augroup END

augroup spell_highlight
    autocmd!
    autocmd ColorScheme * hi clear SpellBad | hi clear SpellCap
                      \ | hi clear SpellRare | hi clear SpellLocal
                      \ | hi SpellBad cterm=italic
augroup END
silent! doautocmd ColorScheme


" Show whitespace characters
set listchars=tab:»»,extends:›,precedes:‹,nbsp:·,trail:·
set list


" Highlight matching brackets
set showmatch
set matchpairs+=<:>


" Always show the status bar at the bottom
set laststatus=2

" Show current position in status bar
set ruler
set rulerformat=%=%l/%L\ %c\ (%P)

" Show commands in status bar
set showcmd

" If in non-normal mode, show the mode in the status bar
set showmode

" Show a dialog to save changes instead of an error message
set confirm

" Auto-clear messages from the status bar
augroup clear_messages
    autocmd!
    autocmd CursorHold * echo
augroup END


" Better copy and paste behavior (needs vim-gtk3 installed)
if has('clipboard')
    set clipboard=unnamed,unnamedplus
endif


" Make : and ; synonyms
nnoremap ; :


" Use \ and <space> as the <leader> keys and lower time to enter key sequences
let mapleader='\'
set timeoutlen=750
" Make <space> the <leader> in visual mode as well
nmap <space>  \
vmap <space>  \


" Q normally goes into Ex mode
nmap Q  <Nop>


" Get sudo rights when writing a buffer with w!!
cnoremap w!!  w !sudo tee % >/dev/null


" Fix mouse issues with Alacritty terminal
" Source: https://wiki.archlinux.org/title/Alacritty#Mouse_not_working_properly_in_Vim
set ttymouse=sgr


" Enable the mouse for selections, including a toggle for this mode
set mouse=a
let g:mouse_enabled=1
function! ToggleMouse()
    if g:mouse_enabled == 1
        echo "Mouse OFF"
        set mouse=
        let g:mouse_enabled=0
    else
        echo "Mouse ON"
        set mouse=a
        let g:mouse_enabled=1
    endif
endfunction
noremap <silent><leader>m  :call ToggleMouse()<cr>


" Enable toggling between
"  - showing and hiding line numbers (<leader>l)
"  - absolute and relative numbers (<leader>a) in normal mode
"    (default: relative line numbering)
let g:show_numbers=0
let g:show_absolute_numbers=0
function! ShowLineNumbers()
    if g:show_numbers == 1
        set number
        if g:show_absolute_numbers
            set norelativenumber
        else
            set relativenumber
        endif
    else
        set nonumber
        set norelativenumber
    endif
endfunction
function! ToggleLineNumbers()
    if g:show_numbers == 1
        let g:show_numbers=0
    else
        let g:show_numbers=1
    endif
    call ShowLineNumbers()
endfunction
function! ToggleAbsoluteAndRelativeLineNumbers()
    if g:show_absolute_numbers == 1
        let g:show_absolute_numbers=0
    else
        let g:show_absolute_numbers=1
    endif
    call ShowLineNumbers()
endfunction
" Auto-switch between absolute and relative numbering when switching modes
" (insert mode always shows absolute numbers when numbers are shown)
augroup numbertoggle
    autocmd!
    autocmd BufEnter,FocusGained,InsertLeave * call ShowLineNumbers()
    autocmd BufLeave,FocusLost,InsertEnter   * if g:show_numbers == 1 | set number | set norelativenumber | endif
augroup END
" Key bindings
nnoremap <silent><leader>l  :call ToggleLineNumbers()<cr>
nnoremap <silent><leader>a  :call ToggleAbsoluteAndRelativeLineNumbers()<cr>


" Show all possible matches above command-line when tab completing
set wildmenu
set wildmode=longest:full,full


" Highlight search results
set hlsearch

" Shortcut to remove current highlighting
nnoremap <silent><leader>h  :nohlsearch<cr>

" Move cursor to result while typing immediately
set incsearch

" Ignore case when searching
set ignorecase

" Upper case search term => case sensitive search
set smartcase

" Highlight the next match in red for 0.25 seconds
function! HighlightNext()
    let [bufnum, lnum, col, off] = getpos('.')
    let matchlen = strlen(matchstr(strpart(getline('.'),col-1),@/))
    let target_pat = '\c\%#\%('.@/.'\)'
    let ring = matchadd('ErrorMsg', target_pat, 101)
    redraw
    exec 'sleep ' . float2nr(250) . 'm'
    call matchdelete(ring)
    redraw
endfunction
nnoremap <silent>n  n:call HighlightNext()<cr>
nnoremap <silent>N  N:call HighlightNext()<cr>


" Make <leader>w save the buffer in normal mode
" and <c-z> save the buffer in all modes
" (the latter disables making VIM a background job;
"  <c-z> is useful to have as <leader>w does not work in INSERT mode)
nnoremap <leader>w  :update<cr>
nnoremap <c-z>      :update<cr>
vnoremap <c-z>      <c-c>:update<cr>
inoremap <c-z>      <c-o>:update<cr>

" <leader>q quits VIM
nnoremap <leader>q  :quit<cr>

" Easier switching between tabs
noremap <leader>,  <esc>:tabprevious<cr>
noremap <leader>.  <esc>:tabnext<cr>

" Arrow keys either (un)indent lines or move them up or down
" (same for blocks of lines in visual mode)
nnoremap <left>          <<
nnoremap <right>         >>
nnoremap <silent><up>    :m-2<cr>
nnoremap <silent><down>  :m+<cr>
vnoremap <left>          <gv
vnoremap <right>         >gv
vnoremap <up>            :m'<-2<cr>gv=gv
vnoremap <down>          :m'>+1<cr>gv=gv

" Make Y yank the rest of a line, just like C or D work
nnoremap Y  y$

" Alphabetically sort a selection of lines
vnoremap <leader>s  :sort<cr>

" Switch two words, just like xp switches two characters
nnoremap <leader>xp  dwElp


" Auto-reload a file that was changed by some other process
" if the buffer has not yet been changed in the meantime
set autoread
set updatetime=1000
augroup checktime
    autocmd!
    autocmd BufEnter     * silent! checktime
    autocmd CursorHold   * silent! checktime
    autocmd CursorHoldI  * silent! checktime
augroup END


" Auto-reload ~/.config/vim/vimrc on write for a fast edit loop
" => NOTE: This adds to state rather than replacing it,
"          so, for example, removed mappings and options persist
"          until VIM is restarted
augroup vimrc
    autocmd!
    autocmd BufWritePost $MYVIMRC source % | redraw
augroup END
" Key binding to reload ~/.config/vim/vimrc manually
nnoremap <silent><leader>rc  :so $MYVIMRC<cr>