add parser installer

lua/nvim-treesitter/install.lua

@@ -0,0 +1,74 @@
+local api = vim.api
+local fn = vim.fn
+
+local M = {}
+local package_path = nil
+local repositories = {
+  javascript = {
+    url = "https://github.com/tree-sitter/tree-sitter-javascript",
+    files = "src/parser.c src/scanner.c",
+  },
+  c = {
+    url = "https://github.com/tree-sitter/tree-sitter-c",
+    files = "src/parser.c"
+  }
+}
+
+-- TODO(kyazdani): there might be a better way to get the plugin path
+for _, path in pairs(api.nvim_list_runtime_paths()) do
+  if string.match(path, '.*/nvim%-treesitter') then
+    package_path = path
+    break
+  end
+end
+
+local function create_compile_command(ft, path, files)
+  -- TODO(kyazdani): should download the parser in $XDG_CACHE_HOME instead of /tmp
+  return "cd /tmp/tree-sitter-"..ft..[[ && \
+    gcc -o parser.so -shared ]]..files..[[ -Os -I./src && \
+    mv parser.so ]]..path.."/parsers/"..ft..[[.so && \
+    rm -rf /tmp/tree-sitter-]]..ft
+end
+
+local function create_download_command(url)
+  return "cd /tmp && git clone "..url
+end
+
+function M.install_parser(lang)
+  if fn.has('win32') == 1 then
+    -- TODO(kyazdani): this should work on windows too
+    api.nvim_err_writeln('This command is not available on windows at the moment.')
+    return
+  end
+
+  if not lang then
+    api.nvim_err_writeln("usage: install_parser('language')")
+    return
+  end
+
+  local repository = repositories[lang]
+  if not repository then
+    api.nvim_err_writeln('Parser not available for language '..lang)
+    return
+  end
+
+  if not package_path then
+    api.nvim_err_writeln('Plugin runtime path not found.')
+    return
+  end
+
+  if not fn.executable('git') == 1 then
+    api.nvim_err_writeln('Please install `git` to download parsers.')
+    return
+  end
+
+  print("Downloading parser...")
+  fn.system(create_download_command(repository.url))
+
+  print("Compiling parser...")
+  fn.system(create_compile_command(lang, package_path, repository.files))
+
+  print("Install for the " ..lang.." parser was successfull")
+end
+
+return M