" ======================================================================
" File:            highlight.vim
" Maintainer:      Joshua Potter <jrpotter2112@gmail.com>
"
" ======================================================================

if exists('g:loaded_highlight')
    finish
endif
let g:loaded_highlight = 1


" GLOBAL VARIABLES:
" ======================================================================

let g:highlight_register_default_color = 'Yellow'


" SCRIPT VARIABLES:
" ======================================================================

" s:registry_colors :: { String : String } {{{2
" ----------------------------------------------------------------------
" Mapping between registry name and color that should be used for
" highlighting.

let s:registry_colors = {}


" s:registry :: { String : { String : Match } } {{{2
" ----------------------------------------------------------------------
" Name of register corresponding to a dict of some unique identifier of the
" word being matched, paired with the actual match object.

let s:registry = {}


" FUNCTION: GroupName(reg) {{{1
" ======================================================================
" Note group names are not allowed to have special characters; they 
" must be alphanumeric or underscores.

function! s:GroupName(reg)
    return 'HighlightRegistry_' . char2nr(a:reg)
endfunction


" FUNCTION: InitRegister(reg) {{{1
" ======================================================================
" Setups the group and highlighting. Matches are added afterward.

function! s:InitRegister(reg, color)
    call s:ClearRegister(a:reg)
    let s:registry_colors[a:reg] = a:color
    exe 'hi ' . s:GroupName(a:reg) . ' cterm=bold,underline ctermfg=' . a:color
endfunction


" FUNCTION: ClearRegister(reg) {{{1
" ======================================================================
" Used to clear out the 'registers' that are used to hold which values are
" highlighted under a certain match group.

function! s:ClearRegister(reg)
    exe 'hi clear ' . s:GroupName(a:reg)
    if has_key(s:registry_colors, a:reg)
        unlet s:registry_colors[a:reg]
    endif
    if has_key(s:registry, a:reg)
        for key in keys(s:registry[a:reg])
            call matchdelete(s:registry[a:reg][key])
            unlet s:registry[a:reg][key]
        endfor
        unlet s:registry[a:reg]
    endif
    call s:ActivateRegister(a:reg)
endfunction


" FUNCTION: ActivateRegister(reg) {{{1
" ======================================================================
" We must actively set the search register to perform searches as expected.

function! s:ActivateRegister(reg)
    if has_key(s:registry, a:reg) && has_key(s:registry_colors, a:reg)
        let search = ''
        for key in keys(s:registry[a:reg])
            let search = search . key . '\|'
        endfor
        let @/ = search[:-3]
        exe 'hi Search cterm=bold,underline ctermbg=none ctermfg=' . s:registry_colors[a:reg]
        set hlsearch
    else
        let @/ = ''
    endif
endfunction


" FUNCTION: AppendToSearch(reg, pattern) {{{1
" ======================================================================

function! s:AppendToSearch(reg, pattern)
    let s:last_seen = a:pattern
    if !has_key(s:registry_colors, a:reg)
        call s:InitRegister(a:reg, g:highlight_register_default_color)
    endif
    if !has_key(s:registry, a:reg)
        let s:registry[a:reg] = {}
    endif
    " Don't want to add multiple match objects into registry
    if !has_key(s:registry[a:reg], a:pattern)
        let s:registry[a:reg][a:pattern] = 
                    \ matchadd(s:GroupName(a:reg), a:pattern)
    endif
    call s:ActivateRegister(a:reg)
endfunction


" FUNCTION: AppendToSearchForward(reg, pattern) {{{1
" ======================================================================

function! s:AppendToSearchForward(reg, pattern)
    call s:AppendToSearch(a:reg, a:pattern)
    normal! *
endfunction


" FUNCTION: AppendToSearchBackward(reg, pattern) {{{1
" ======================================================================

function! s:AppendToSearchBackward(reg, pattern)
    call s:AppendToSearch(a:reg, a:pattern)
    normal! #
endfunction


" FUNCTION: RemoveFromSearch(reg, pattern) {{{1
" ======================================================================

function! s:RemoveFromSearch(reg, pattern)
    if has_key(s:registry, a:reg) && has_key(s:registry[a:reg], a:pattern)
        call matchdelete(s:registry[a:reg][a:pattern])
        unlet s:registry[a:reg][a:pattern]
        if len(s:registry[a:reg]) == 0
            unlet s:registry[a:reg]
        endif
    endif
    call s:ActivateRegister(a:reg)
endfunction


" PROCEDURE: Initialize {{{1
" ======================================================================

exe 'hi Search cterm=bold,underline ctermbg=none ctermfg=' . g:highlight_register_default_color

call s:InitRegister('0', 'Yellow')
call s:InitRegister('1', 'DarkYellow')
call s:InitRegister('2', 'Red')
call s:InitRegister('3', 'Magenta')
call s:InitRegister('4', 'Green')
call s:InitRegister('5', 'Cyan')
call s:InitRegister('6', 'Blue')
call s:InitRegister('7', 'White')
call s:InitRegister('8', 'Gray')
call s:InitRegister('9', 'Black')

noremap <unique> <silent> <Plug>HighlightRegistry_AppendToSearch
            \ :call <SID>AppendToSearch(v:register, '\<'.expand('<cword>').'\>')<CR>
noremap <unique> <silent> <Plug>HighlightRegistry_Forward_AppendToSearch
            \ :call <SID>AppendToSearchForward(v:register, '\<'.expand('<cword>').'\>')<CR>
noremap <unique> <silent> <Plug>HighlightRegistry_Backward_AppendToSearch
            \ :call <SID>AppendToSearchBackward(v:register, '\<'.expand('<cword>').'\>')<CR>
noremap <unique> <silent> <Plug>HighlightRegistry_RemoveFromSearch
            \ :call <SID>RemoveFromSearch(v:register, '\<'.expand('<cword>').'\>')<CR>
noremap <unique> <silent> <Plug>HighlightRegistry_ClearRegister
            \ :call <SID>ClearRegister(v:register)<CR>
noremap <unique> <silent> <Plug>HighlightRegistry_ActivateRegister
            \ :call <SID>ActivateRegister(v:register)<CR>

" Basic Mappings
nmap & <Plug>HighlightRegistry_AppendToSearch
nmap * <Plug>HighlightRegistry_Forward_AppendToSearch
nmap # <Plug>HighlightRegistry_Backward_AppendToSearch

" Additional Register Modifiers
nmap y& <Plug>HighlightRegistry_ActivateRegister
nmap d& <Plug>HighlightRegistry_RemoveFromSearch
nmap c& <Plug>HighlightRegistry_ClearRegister