local M = {}

-- see luasnip/util/types.lua
local types = {
  textNode = 1,
  insertNode = 2,
  functionNode = 3,
  snippetNode = 4,
  choiceNode = 5,
  dynamicNode = 6,
  snippet = 7,
  exitNode = 8,
  restoreNode = 9,
  node_types = { 1, 2, 3, 4, 5, 6, 7, 8, 9 },
}

function M.config()
  lvim.builtin.luasnip = {
    sources = {
      friendly_snippets = true,
    },
    config = {
      history = false,
      updateevents = "TextChanged,TextChangedI",
      ext_opts = {
        -- Will be populated within config function
      },
    },
    ext_opts = {
      -- Show virtual text to signal when you are inside an sippets
      [types.insertNode] = {
        active = {
          virt_text = { { "<-- snip insert", "BufferInactiveIndex" } },
        },
      },
      -- Helps to notice when you are within a choice node
      [types.choiceNode] = {
        active = {
          virt_text = { { "<-- choice", "BufferInactiveIndex" } },
        },
      },
    },
  }
end

function M.setup()
  local utils = require "lvim.utils"
  local paths = {}
  if lvim.builtin.luasnip.sources.friendly_snippets then
    paths[#paths + 1] = utils.join_paths(get_runtime_dir(), "site", "pack", "packer", "start", "friendly-snippets")
  end

  local user_snippets = utils.join_paths(get_config_dir(), "snippets")
  if utils.is_directory(user_snippets) then
    paths[#paths + 1] = user_snippets
  end

  local luasnip = require "luasnip"
  luasnip.config.set_config(lvim.builtin.luasnip.config)

  -- When no paths are provided, luasnip will search in the runtimepath
  require("luasnip.loaders.from_lua").lazy_load()
  require("luasnip.loaders.from_vscode").lazy_load { paths = paths }
  require("luasnip.loaders.from_snipmate").lazy_load()
end

---when inside a snippet, seeks to the nearest luasnip field if possible, and checks if it is jumpable
---@param dir number 1 for forward, -1 for backward; defaults to 1
---@return boolean true if a jumpable luasnip field is found while inside a snippet
local function jumpable(dir)
  local luasnip_ok, luasnip = pcall(require, "luasnip")
  if not luasnip_ok then
    return false
  end

  local win_get_cursor = vim.api.nvim_win_get_cursor
  local get_current_buf = vim.api.nvim_get_current_buf

  ---sets the current buffer's luasnip to the one nearest the cursor
  ---@return boolean true if a node is found, false otherwise
  local function seek_luasnip_cursor_node()
    -- TODO(kylo252): upstream this
    -- for outdated versions of luasnip
    if not luasnip.session.current_nodes then
      return false
    end

    local node = luasnip.session.current_nodes[get_current_buf()]
    if not node then
      return false
    end

    local snippet = node.parent.snippet
    local exit_node = snippet.insert_nodes[0]

    local pos = win_get_cursor(0)
    pos[1] = pos[1] - 1

    -- exit early if we're past the exit node
    if exit_node then
      local exit_pos_end = exit_node.mark:pos_end()
      if (pos[1] > exit_pos_end[1]) or (pos[1] == exit_pos_end[1] and pos[2] > exit_pos_end[2]) then
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil

        return false
      end
    end

    node = snippet.inner_first:jump_into(1, true)
    while node ~= nil and node.next ~= nil and node ~= snippet do
      local n_next = node.next
      local next_pos = n_next and n_next.mark:pos_begin()
      local candidate = n_next ~= snippet and next_pos and (pos[1] < next_pos[1])
          or (pos[1] == next_pos[1] and pos[2] < next_pos[2])

      -- Past unmarked exit node, exit early
      if n_next == nil or n_next == snippet.next then
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil

        return false
      end

      if candidate then
        luasnip.session.current_nodes[get_current_buf()] = node
        return true
      end

      local ok
      ok, node = pcall(node.jump_from, node, 1, true) -- no_move until last stop
      if not ok then
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil

        return false
      end
    end

    -- No candidate, but have an exit node
    if exit_node then
      -- to jump to the exit node, seek to snippet
      luasnip.session.current_nodes[get_current_buf()] = snippet
      return true
    end

    -- No exit node, exit from snippet
    snippet:remove_from_jumplist()
    luasnip.session.current_nodes[get_current_buf()] = nil
    return false
  end

  if dir == -1 then
    return luasnip.in_snippet() and luasnip.jumpable(-1) else
    return luasnip.in_snippet() and seek_luasnip_cursor_node() and luasnip.jumpable(1)
  end
end

M.methods = {}

M.methods.jumpable = jumpable

return M