" Use VIM improved mode
set nocompatible

" Ensure we work with Unicode
set encoding=utf-8
scriptencoding utf-8

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

" Number of remembered undo steps
set undolevels=1000


" Ensure the XDG variables exist even when `vim` is started
" outside a login shell (e.g., from a desktop launcher)
let $XDG_CONFIG_HOME = get(environ(), 'XDG_CONFIG_HOME', $HOME . '/.config')
let $XDG_STATE_HOME = get(environ(), 'XDG_STATE_HOME', $HOME . '/.local/state')

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]


" Make :!cmd use `bash` and load the shell aliases
set shell=/bin/bash
let $BASH_ENV = expand("$XDG_CONFIG_HOME/shell/aliases")


" 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
"
" Note: `viminfo` is a plain string option, so `:set` does not expand
" environment variables in it (unlike the path options below)
" => Build the value via `execute` to expand $XDG_STATE_HOME
execute 'set viminfo+=n' . $XDG_STATE_HOME . '/vim/viminfo'
"
" Use dedicated folders to store temporary backup, swap, and undo files
" (Note: // means that `vim` adapts names automatically to avoid duplicates)
set backupdir=$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

" Make search highlights readable
" => Explicit `ctermfg` with each `ctermbg`
"    because the palette only guarantees contrast
"    of each ANSI hue against the background
augroup search_highlight
    autocmd!
    autocmd ColorScheme * hi Search    cterm=bold ctermfg=black ctermbg=yellow
                      \ | hi IncSearch cterm=bold,reverse ctermfg=yellow ctermbg=black
                      \ | hi CurSearch cterm=bold ctermfg=black ctermbg=cyan
augroup END

" Make warnings and errors in the status bar stand out
augroup message_highlight
    autocmd!
    autocmd ColorScheme * hi WarningMsg cterm=bold,reverse ctermfg=yellow ctermbg=black
                      \ | hi ErrorMsg   cterm=bold,reverse ctermfg=red    ctermbg=black
augroup END

" Apply all ColorScheme overrides above on startup
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

" Three lines for commands and messages, so that
" longer warnings fit without a "Press ENTER" prompt
set cmdheight=3

" 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


" 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>


" Write with `sudo` rights with w!! or wq!!
function! SudoWrite() abort
    " `silent` to skip the "Press ENTER" prompt
    silent write !sudo tee % >/dev/null
    if v:shell_error
        " Repaint first, then show the error, so that it is not wiped
        redraw!
        echohl ErrorMsg | echomsg 'sudo write failed' | echohl None
    else
        " Keep the undo history intact
        set nomodified
        " Suppress the "File has changed ..." warning
        " (Note: With `autoread` on, `checktime` syncs the timestamp silently;
        "  without it, a hidden but blocking W11 prompt would appear)
        let s:autoread = &autoread
        set autoread
        silent! checktime %
        let &autoread = s:autoread
        " Repaint last to cancel any pending "Press ENTER" state
        redraw!
        echo ''
    endif
endfunction
"
command! -bar SudoWrite call SudoWrite()
cnoreabbrev w!!  silent SudoWrite
"
" Quit only if the `sudo` write did not fail
command! -bar SudoWriteQuit call SudoWrite() | if !v:shell_error | quit | endif
cnoreabbrev wq!!  silent SudoWriteQuit


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


" Make the cursor easier to see

let &t_EI = "\e[2 q"  " normal mode: steady block
let &t_SI = "\e[1 q"  " insert mode: blinking block
let &t_SR = "\e[2 q"  " replace mode: steady block

augroup cursor_shape
  autocmd!
  autocmd VimEnter * silent execute "!echo -ne '\e[2 q'" | redraw!
  autocmd VimLeave * silent execute "!echo -ne '\e[1 q'" | redraw!
augroup END


" 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), and
"  - Absolute and relative numbers (<leader>a) in normal mode
"
" The default is hidden and relative when shown
"
" Note: Both flags are buffer-local ("b:") with global ("g:") fallbacks,
" so that filetype plugins can enable numbers per buffer
" without leaking into other buffers
let g:show_numbers=0
let g:show_absolute_numbers=0
"
function! ShowLineNumbers()
    if get(b:, 'show_numbers', get(g:, 'show_numbers', 0))
        setlocal number
        if get(b:, 'show_absolute_numbers', get(g:, 'show_absolute_numbers', 0))
            setlocal norelativenumber
        else
            setlocal relativenumber
        endif
    else
        setlocal nonumber
        setlocal norelativenumber
    endif
endfunction
"
function! ToggleLineNumbers()
    let b:show_numbers = !get(b:, 'show_numbers', get(g:, 'show_numbers', 0))
    call ShowLineNumbers()
endfunction
"
function! ToggleAbsoluteAndRelativeLineNumbers()
    let b:show_absolute_numbers = !get(b:, 'show_absolute_numbers', get(g:, 'show_absolute_numbers', 0))
    call ShowLineNumbers()
endfunction
"
" Auto-switch between absolute and relative numbering when switching modes
" where insert mode always shows absolute numbers when numbers are shown
augroup numbertoggle
    autocmd!
    autocmd BufEnter,FocusGained,InsertLeave * call ShowLineNumbers()
    autocmd BufLeave,FocusLost,InsertEnter   *
        \ if get(b:, 'show_numbers', get(g:, 'show_numbers', 0))
        \ |     setlocal number 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>:echo<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>


" Save and quit, in three symmetric flavors:
"  - Quit        => <c-q> / <leader>q  (~ `:quit`)
"  - Save        => <c-s> / <leader>w  (~ `:update`)
"  - Save & Quit => <c-z> / <leader>z  (~ `:exit`)
"
" The <c-*> chords work in normal, visual, and insert mode
" whereas the <leader> variants are chord-free alternatives in normal mode
"
" VIM's built-ins remain untouched and complete the picture:
"  - ZZ => `:exit`  => Save if changed, then quit (~ "Keep changes, and close")
"  - ZQ => `:quit!` => Discard changes, then quit (~ "Never mind, just close")
"
" Notes:
"  - <c-s> and <c-q> require flow control to be off
"    (see `stty -ixon` in ~/.bashrc and ~/.zshrc),
"    or they freeze the terminal instead
"  - <c-z> no longer suspends VIM into a background job
"  - `:exit` writes only if there are changes, then quits
"
nnoremap <c-q>      :quit<cr>
vnoremap <c-q>      <c-c>:quit<cr>
inoremap <c-q>      <esc>:quit<cr>
nnoremap <leader>q  :quit<cr>
"
nnoremap <c-s>      :update<cr>
vnoremap <c-s>      <c-c>:update<cr>
inoremap <c-s>      <c-o>:update<cr>
nnoremap <leader>w  :update<cr>
"
nnoremap <c-z>      :exit<cr>
vnoremap <c-z>      <c-c>:exit<cr>
inoremap <c-z>      <esc>:exit<cr>
nnoremap <leader>z  :exit<cr>
"
" Show a dialog to save changes instead of an error message
set confirm


" 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$

" Make X replace the character under the cursor with a space
nnoremap X  r<space>

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

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


" Warn if a file was changed on disk by some other process
" => The buffer is NOT reloaded automatically; instead:
"     - `:DiffDisk` shows what differs (close with `:q` in the split)
"     - `:e` takes the disk version, `:w` keeps the buffer
augroup checktime
    autocmd!
    autocmd FocusGained,BufEnter * silent! checktime
augroup END
"
" Show a diff between the buffer and its file on disk
" => Close the split with :q; diff mode ends automatically
command! DiffDisk vert new | set buftype=nofile | read ++edit # | 0d_
                \ | diffthis | wincmd p | diffthis | wincmd p
                \ | autocmd BufWinLeave <buffer> diffoff!


" Jump to the last known cursor position when reopening a file,
" skipping commit messages and invalid positions
augroup restore_position
    autocmd!
    autocmd BufReadPost * if line("'\"") >= 1 && line("'\"") <= line("$") && &filetype !~# 'commit'
                      \ |     execute "normal! g`\""
                      \ | endif
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>