refactor: Add a generic provider module

In preperation for coc support

lua/symbols-outline.lua

@@ -1,12 +1,12 @@
 local vim = vim
 
 local parser = require('symbols-outline.parser')
+local providers = require('symbols-outline.providers.init')
 local ui = require('symbols-outline.ui')
 local writer = require('symbols-outline.writer')
 local config = require('symbols-outline.config')
 local lsp_utils = require('symbols-outline.utils.lsp_utils')
 local utils = require('symbols-outline.utils.init')
-local markdown = require('symbols-outline.markdown')
 local view = require('symbols-outline.view')
 
 local M = {}
@@ -29,10 +29,6 @@ local function setup_buffer_autocmd()
 
 end
 
-local function getParams()
-    return {textDocument = vim.lsp.util.make_text_document_params()}
-end
-
 -------------------------
 -- STATE
 -------------------------
@@ -48,7 +44,7 @@ local function wipe_state()
     M.state = {outline_items = {}, flattened_outline_items = {}}
 end
 
-local function __refresh ()
+local function __refresh()
     if M.state.outline_buf ~= nil then
         local function refresh_handler(response)
             if response == nil or type(response) ~= 'table' then
@@ -70,11 +66,7 @@ local function __refresh ()
                                    M.state.flattened_outline_items)
         end
 
-        if vim.api.nvim_buf_get_option(0, 'ft') == 'markdown' then
-            refresh_handler(markdown.handle_markdown())
-        end
-        vim.lsp.buf_request_all(0, "textDocument/documentSymbol", getParams(),
-                                refresh_handler)
+        providers.request_symbols(refresh_handler)
     end
 end
 
@@ -195,16 +187,12 @@ end
 
 function M.open_outline()
     if M.state.outline_buf == nil then
-        if vim.api.nvim_buf_get_option(0, 'ft') == 'markdown' then
-            handler(markdown.handle_markdown())
-        end
-        vim.lsp.buf_request_all(0, "textDocument/documentSymbol", getParams(),
-                                handler)
+        providers.request_symbols(handler)
     end
 end
 
 function M.close_outline()
-    if M.state.outline_buf ~= nil then
+    if M.state.outline_buf then
         vim.api.nvim_win_close(M.state.outline_win, true)
     end
 end