-------------------------------------------------------------------------------
-- Tools to deal with the board
-------------------------------------------------------------------------------
local Board = {
  saved_state = nil,
}

local Util = require('oleoboard.util')

-------------------------------------------------------------------------------
-- Internal Functions
-------------------------------------------------------------------------------
local function get_directories(parent_path)

  local directories = {}
  local directory_iterator = vim.loop.fs_scandir(parent_path)

  if directory_iterator then
    while true do
      local name, type = vim.loop.fs_scandir_next(directory_iterator)
      if not name then break end
      if type == "directory" then
        table.insert(directories, 1, parent_path .. '/' .. name)
      end
    end
  else
    vim.api.nvim_err_writeln('Could not read directory ' .. parent_path)
  end

  return directories
end

local function save_state()

  local config_dir = vim.fn.stdpath('config')
  local session_file = config_dir .. '/oleoboard.saved'
  vim.cmd('mks! ' .. session_file)

  Board.saved_state = session_file
end

local function close_all_buffers()
  for _, window in ipairs(vim.api.nvim_list_wins()) do
    if window ~= vim.api.nvim_get_current_win() then
      vim.api.nvim_win_close(window, false)
    end
  end
end

local function restore_state()
  if Board.saved_state then

    local config_dir = vim.fn.stdpath('config')
    local session_file = config_dir .. '/oleoboard.saved'
    if vim.fn.filereadable(session_file) == 1 then
      vim.cmd('source ' .. session_file)
      vim.fn.delete(session_file)
    end

    Board.saved_state = nil
  end
end

local function find_left_neighbor(windows, current_window)

  local left_window = nil

  for _, window in ipairs(windows) do
    local window_position = vim.api.nvim_win_get_position(window)
    local current_position = vim.api.nvim_win_get_position(current_window)
    if Util.is_left_of(current_position, window_position) then
      if left_window then
        local candidate_position = vim.api.nvim_win_get_position(left_window)
        if Util.is_right_of(candidate_position, window_position) then
          left_window = window
        end
      else
        left_window = window
      end
    end
  end

  return left_window
end

local function find_right_neighbor(windows, current_window)

  local right_window = nil

  for _, window in ipairs(windows) do
    local window_position = vim.api.nvim_win_get_position(window)
    local current_position = vim.api.nvim_win_get_position(current_window)
    if Util.is_right_of(current_position, window_position) then
      right_window = window
      break
    end
  end

  return right_window
end

-------------------------------------------------------------------------------
-- Public Interface
-------------------------------------------------------------------------------

--- Toggles the board
function Board.toggle(directory)
  if Board.saved_state then
    Board.close()
  else
    Board.open(directory)
  end
end

--- Opens the board
function Board.open(directory)
  if not directory or directory == '' then
    directory = vim.fn.getcwd()
  end

  local directories = get_directories(directory)
  if #directories > 0 then
    save_state()
    close_all_buffers()
    vim.api.nvim_command('enew')

    for i, directory in ipairs(directories) do
      if i > 1 then
        vim.api.nvim_command('vsplit')
      end
      vim.api.nvim_command('edit ' .. directory)
      vim.api.nvim_buf_set_var(0, 'is_oleoboard_column', true)
    end
  end
end

--- Closes the board
function Board.close()
  for _, window in ipairs(vim.api.nvim_list_wins()) do
    local buffer = vim.api.nvim_win_get_buf(window)
    local ok, is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, buffer, 'is_oleoboard_column')
    if ok and is_oleoboard_column then
      vim.api.nvim_buf_delete(buffer, {force = true})
    end
  end

  restore_state()
end

--- Moves the entry under the cursor to the right
function Board.move_entry_right()

  local current_window = vim.api.nvim_get_current_win()
  local windows = vim.api.nvim_tabpage_list_wins(0)
  local right_window = nil

  right_window = find_right_neighbor(windows, current_window)

  if right_window then
    local buffer = vim.api.nvim_win_get_buf(right_window)
    local ok, is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, buffer, 'is_oleoboard_column')
    if ok and is_oleoboard_column then
      vim.cmd('normal! dd')
      vim.api.nvim_set_current_win(right_window)
      vim.cmd('normal! G')
      vim.cmd('normal! p')
    end
  end
end

--- Moves the entry under the cursor to the left
function Board.move_entry_left()

  local current_window = vim.api.nvim_get_current_win()
  local windows = vim.api.nvim_tabpage_list_wins(0)
  local left_window = nil

  left_window = find_left_neighbor(windows, current_window)

  if left_window then
    local buffer = vim.api.nvim_win_get_buf(left_window)
    local ok, is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, buffer, 'is_oleoboard_column')
    if ok and is_oleoboard_column then
      vim.cmd('normal! dd')
      vim.api.nvim_set_current_win(left_window)
      vim.cmd('normal! G')
      vim.cmd('normal! p')
    end
  end
end

--- Moves the active column to the right
function Board.move_column_right()
  local current_window = vim.api.nvim_get_current_win()
  local windows = vim.api.nvim_tabpage_list_wins(0)
  local right_window = find_right_neighbor(windows, current_window)

  if right_window then
    local right_buffer = vim.api.nvim_win_get_buf(right_window)
    local current_buffer = vim.api.nvim_win_get_buf(current_window)
    local right_ok, right_is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, right_buffer, 'is_oleoboard_column')
    local current_ok, current_is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, current_buffer, 'is_oleoboard_column')
    if right_ok and right_is_oleoboard_column and current_ok and current_is_oleoboard_column then
      vim.api.nvim_win_set_buf(right_window, current_buffer)
      vim.api.nvim_win_set_buf(current_window, right_buffer)
      vim.api.nvim_set_current_win(right_window)
    end
  end
end

--- Moves the active column to the left
function Board.move_column_left()
  local current_window = vim.api.nvim_get_current_win()
  local windows = vim.api.nvim_tabpage_list_wins(0)
  local left_window = find_left_neighbor(windows, current_window)

  if left_window then
    local left_buffer = vim.api.nvim_win_get_buf(left_window)
    local current_buffer = vim.api.nvim_win_get_buf(current_window)
    local left_ok, left_is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, left_buffer, 'is_oleoboard_column')
    local current_ok, current_is_oleoboard_column = pcall(vim.api.nvim_buf_get_var, current_buffer, 'is_oleoboard_column')
    if left_ok and left_is_oleoboard_column and current_ok and current_is_oleoboard_column then
      vim.api.nvim_win_set_buf(left_window, current_buffer)
      vim.api.nvim_win_set_buf(current_window, left_buffer)
      vim.api.nvim_set_current_win(left_window)
    end
  end
end

return Board