local luv = vim.loop
local utils = require'nvim-tree.utils'
local config = require'nvim-tree.config'
local M = {}

local roots = {}
local fstat_cache = {}

local not_git = 'not a git repo'
local is_win = vim.api.nvim_call_function("has", {"win32"}) == 1

local function update_root_status(root)
  local untracked = ' -u'
  if vim.fn.trim(vim.fn.system('git config --type=bool status.showUntrackedFiles')) == 'false' then
    untracked = ''
  end
  local status = vim.fn.systemlist('cd "'..root..'" && git status --porcelain=v1'..untracked)
  roots[root] = {}

  for _, v in pairs(status) do
    local head = v:sub(0, 2)
    local body = v:sub(4, -1)
    if body:match('%->') ~= nil then
      body = body:gsub('^.* %-> ', '')
    end

    --- Git returns paths with a forward slash wherever you run it, thats why i have to replace it only on windows
    if is_win then
      body = body:gsub("/", "\\")
    end

    roots[root][body] = head
  end
end

---Returns a list of all ignored files and directories in the given git directory.
---@param git_root string|nil
---@return table
function M.get_gitignored(git_root)
  local result = vim.fn.systemlist(
    "git -C '" .. (git_root or "") .. "' ls-files --others --ignored --exclude-standard --directory"
  )
  if result[1] and result[1]:match("^fatal:") then
    return {}
  end

  return result
end

function M.reload_roots()
  for root, status in pairs(roots) do
    if status ~= not_git then
      update_root_status(root)
    end
  end
end

local function get_git_root(path)
  if roots[path] then
    return path, roots[path]
  end

  for name, status in pairs(roots) do
    if status ~= not_git then
      if path:match(utils.path_to_matching_str(name)) then
        return name, status
      end
    end
  end
end

local function create_root(cwd)
  local git_root = vim.fn.system('cd "'..cwd..'" && git rev-parse --show-toplevel')

  if not git_root or #git_root == 0 or git_root:match('fatal') then
    roots[cwd] = not_git
    return false
  end

  if is_win then
    git_root = git_root:gsub("/", "\\")
  end

  update_root_status(git_root:sub(0, -2))
  M.update_gitignore_map()
  return true
end

---Get the root of the git dir containing the given path or `nil` if it's not a
---git dir.
---@param path string
---@return string|nil
function M.git_root(path)
  local git_root, git_status = get_git_root(path)
  if not git_root then
    if not create_root(path) then
      return
    end
    git_root, git_status = get_git_root(path)
  end

  if git_status == not_git then
    return
  end

  return git_root
end

function M.update_status(entries, cwd, parent_node)
  local git_root, git_status = get_git_root(cwd)
  if not git_root then
    if not create_root(cwd) then
      return
    end
    git_root, git_status = get_git_root(cwd)
  elseif git_status == not_git then
    return
  end

  if not git_root then
    return
  end

  if not parent_node then parent_node = {} end

  local matching_cwd = utils.path_to_matching_str( utils.path_add_trailing(git_root) )
  local num_ignored = 0

  for _, node in pairs(entries) do
    if parent_node.git_status == "ignored" or M.should_gitignore(node.absolute_path) then
      node.git_status = "ignored"
      num_ignored = num_ignored + 1

    else
      local relpath = node.absolute_path:gsub(matching_cwd, '')
      if node.entries ~= nil then
        relpath = utils.path_add_trailing(relpath)
        node.git_status = nil
      end

      local status = git_status[relpath]
      if status then
        node.git_status = status
      elseif node.entries ~= nil then
        local matcher = '^'..utils.path_to_matching_str(relpath)
        for key, entry_status in pairs(git_status) do
          if key:match(matcher) then
            node.git_status = entry_status
            break
          end
        end
      else
        node.git_status = nil
      end
    end
  end

  if num_ignored > 0 and num_ignored == #entries then
    parent_node.git_status = "ignored"
  end
end

---A map from git roots to a list of ignored paths
local gitignore_map = {}

---Check if the given path is ignored by git.
---@param path string Absolute path
---@return boolean
function M.should_gitignore(path)
  for _, paths in pairs(gitignore_map) do
    if paths[path] == true then
      return true
    end
  end
  return false
end

---Updates the gitignore map if it's needed. Each entry in the map is only
---updated if changes have been made to the git root's `.gitignore` or
---`.git/info/exclude` files, or it's been invalidated by the
---`invalidate_gitignore_map` function.
function M.update_gitignore_map_sync()
  if not (config.get_icon_state().show_git_icon or vim.g.nvim_tree_git_hl == 1) then
    return
  end

  local ignore_files = { ".gitignore", utils.path_join({".git", "info", "exclude"}) }
  for git_root, git_status in pairs(roots) do
    if git_status ~= not_git then
      -- The mtime for `.gitignore` and `.git/info/exclude` is cached such that
      -- the list of ignored files is only recreated when one of the said files
      -- are modified.
      for _, s in ipairs(ignore_files) do
        local path = utils.path_join({git_root, s})
        local stat = luv.fs_stat(path)
        if stat and stat.mtime then
          if not (fstat_cache[path]
              and fstat_cache[path].mtime == stat.mtime.sec) then

            gitignore_map[git_root] = {
              _valid = false
            }
            fstat_cache[path] = {
              mtime = stat.mtime.sec
            }
          end
        end
      end
    end
  end

  for git_root, paths in pairs(gitignore_map) do
    if not paths._valid then
      gitignore_map[git_root] = {
        _valid = true
      }
      paths = gitignore_map[git_root]

      for _, s in ipairs(M.get_gitignored(git_root)) do
        if is_win then s = s:gsub("/", "\\") end
        s = utils.path_remove_trailing(s)
        paths[utils.path_join({git_root, s})] = true
      end
    end
  end
end

---Updates the gitignore map asynchronously if it's needed.
function M.update_gitignore_map()
  vim.schedule(function()
    M.update_gitignore_map_sync()
  end)
end

---Force the ignore list of this path's git root to be recreated on the next
---call to `update_gitignore_map`.
---@param path string Absolute path
function M.invalidate_gitignore_map(path)
  local git_root = get_git_root(path)
  if git_root and gitignore_map[git_root] then
    gitignore_map[git_root]._valid = false
  end
end

return M