local t = require('test.testutil')
local n = require('test.functional.testnvim')()

local describe, it, before_each, after_each = t.describe, t.it, t.before_each, t.after_each
local clear = n.clear
local command = n.command
local expect = n.expect
local eq = t.eq
local feed = n.feed
local insert = n.insert
local fn = n.fn
local exec = n.exec
local exec_lua = n.exec_lua
local pcall_err = t.pcall_err

local function lastmessage()
  local messages = fn.split(fn.execute('messages'), '\n')
  return messages[#messages]
end

describe('u CTRL-R g- g+', function()
  before_each(clear)

  local function create_history(num_steps)
    if num_steps == 0 then
      return
    end
    insert('1')
    if num_steps == 1 then
      return
    end
    feed('o2<esc>')
    feed('o3<esc>')
    feed('u')
    if num_steps == 2 then
      return
    end
    feed('o4<esc>')
    if num_steps == 3 then
      return
    end
    feed('u')
  end

  local function undo_and_redo(hist_pos, undo, redo, expect_str)
    command('enew!')
    create_history(hist_pos)
    local cur_contents = n.curbuf_contents()
    feed(undo)
    expect(expect_str)
    feed(redo)
    expect(cur_contents)
  end

  -- TODO Look for message saying 'Already at oldest change'
  it('does nothing when no changes have happened', function()
    undo_and_redo(0, 'u', '<C-r>', '')
    undo_and_redo(0, 'g-', 'g+', '')
  end)
  it('undoes a change when at a leaf', function()
    undo_and_redo(1, 'u', '<C-r>', '')
    undo_and_redo(1, 'g-', 'g+', '')
  end)
  it('undoes a change when in a non-leaf', function()
    undo_and_redo(2, 'u', '<C-r>', '1')
    undo_and_redo(2, 'g-', 'g+', '1')
  end)
  it('undoes properly around a branch point', function()
    undo_and_redo(
      3,
      'u',
      '<C-r>',
      [[
      1
      2]]
    )
    undo_and_redo(
      3,
      'g-',
      'g+',
      [[
      1
      2
      3]]
    )
  end)
  it('can find the previous sequence after undoing to a branch', function()
    undo_and_redo(4, 'u', '<C-r>', '1')
    undo_and_redo(4, 'g-', 'g+', '1')
  end)

  it('u restores the pre-change cursor position #5989', function()
    local api = n.api
    local function undo_restores(row, col, keys, pre)
      if pre then
        command(pre)
      end
      api.nvim_buf_set_lines(0, 0, -1, true, { 'this is a test' })
      api.nvim_win_set_cursor(0, { row, col })
      feed(keys)
      feed('u')
      eq({ row, col }, api.nvim_win_get_cursor(0))
    end
    undo_restores(1, 5, 'diw') -- Operator moves to the word start before deleting.
    undo_restores(1, 5, 'd^') -- Backwards motion.
    undo_restores(1, 5, 'atest<Esc>') -- Insert entered after the cursor.
    undo_restores(1, 5, 'viwd')
    undo_restores(1, 2, ',x', 'nnoremap ,x wdiw') -- Mapping: where it was triggered.
    -- i_CTRL-G_u breaks: each block restores to its own start.
    api.nvim_win_set_cursor(0, { 1, 5 })
    feed('ifoo<C-G>ubar<Esc>u')
    eq({ 1, 8 }, api.nvim_win_get_cursor(0))
    feed('u')
    eq({ 1, 5 }, api.nvim_win_get_cursor(0))
  end)

  describe('undo works correctly when writing in Insert mode', function()
    before_each(function()
      exec([[
        edit Xtestfile.txt
        set undolevels=100 undofile
        write
      ]])
    end)

    after_each(function()
      command('bwipe!')
      os.remove('Xtestfile.txt')
      os.remove('Xtestfile.txt.un~')
    end)

    -- oldtest: Test_undo_after_write()
    it('using <Cmd> mapping', function()
      command('imap . <Cmd>write<CR>')
      feed('Otest.<CR>boo!!!<Esc>')
      expect([[
        test
        boo!!!
        ]])

      feed('u')
      expect([[
        test
        ]])

      feed('u')
      expect('')
    end)

    it('using Lua mapping', function()
      exec_lua([[
        vim.api.nvim_set_keymap('i', '.', '', {callback = function()
          vim.cmd('write')
        end})
      ]])
      feed('Otest.<CR>boo!!!<Esc>')
      expect([[
        test
        boo!!!
        ]])

      feed('u')
      expect([[
        test
        ]])

      feed('u')
      expect('')
    end)

    it('using RPC call', function()
      feed('Otest')
      command('write')
      feed('<CR>boo!!!<Esc>')
      expect([[
        test
        boo!!!
        ]])

      feed('u')
      expect([[
        test
        ]])

      feed('u')
      expect('')
    end)
  end)
end)

describe(':undo! command', function()
  before_each(function()
    clear()
    feed('i1 little bug in the code<Esc>')
    feed('o1 little bug in the code<Esc>')
    feed('oTake 1 down, patch it around<Esc>')
    feed('o99 little bugs in the code<Esc>')
  end)
  it('works', function()
    command('undo!')
    expect([[
      1 little bug in the code
      1 little bug in the code
      Take 1 down, patch it around]])
    feed('<C-r>')
    eq('Already at newest change', lastmessage())
  end)
  it('works with arguments', function()
    command('undo! 2')
    expect([[
      1 little bug in the code
      1 little bug in the code]])
    feed('<C-r>')
    eq('Already at newest change', lastmessage())
  end)
  it('correctly sets alternative redo', function()
    feed('uo101 little bugs in the code<Esc>')
    command('undo!')
    feed('<C-r>')
    expect([[
      1 little bug in the code
      1 little bug in the code
      Take 1 down, patch it around
      99 little bugs in the code]])

    feed('uuoTake 2 down, patch them around<Esc>')
    feed('o101 little bugs in the code<Esc>')
    command('undo! 2')
    feed('<C-r><C-r>')
    expect([[
      1 little bug in the code
      1 little bug in the code
      Take 1 down, patch it around
      99 little bugs in the code]])
  end)
  it('fails when attempting to redo or move to different undo branch', function()
    eq(
      'Vim(undo):E5767: Cannot use :undo! to redo or move to a different undo branch',
      pcall_err(command, 'undo! 4')
    )
    feed('u')
    eq(
      'Vim(undo):E5767: Cannot use :undo! to redo or move to a different undo branch',
      pcall_err(command, 'undo! 4')
    )
    feed('o101 little bugs in the code<Esc>')
    feed('o101 little bugs in the code<Esc>')
    eq(
      'Vim(undo):E5767: Cannot use :undo! to redo or move to a different undo branch',
      pcall_err(command, 'undo! 4')
    )
  end)
end)

describe("opening file when 'undofile' is on", function()
  before_each(function()
    clear({ args = { '--cmd', 'set undofile' } })
  end)

  it("does not crash when 'undodir' contains empty entry", function()
    command('set undodir=,.')
    command('edit test/functional/fixtures/bigfile.txt')
    n.assert_alive()
  end)
end)

describe('undo file', function()
  before_each(clear)

  --- Offset of the first undo entry in `blob`: magic bytes 0xf5 0x18, followed by 4-byte ue_top,
  --- ue_bot, ue_lcount, ue_size.
  local function find_entry(blob)
    for i = 1, #blob - 18 do
      if blob:byte(i) == 0xf5 and blob:byte(i + 1) == 0x18 then
        local ok = true
        -- This expects the ue_xx values to be small, so other data (e.g. a timestamp) containing
        -- the magic bytes is not mistaken for an entry.
        for field = 0, 3 do
          local off = i + 2 + field * 4
          ok = ok
            and blob:byte(off) == 0
            and blob:byte(off + 1) == 0
            and blob:byte(off + 2) == 0
            and blob:byte(off + 3) <= 8
        end
        if ok then
          return i
        end
      end
    end
  end

  -- If a corrupted entry is not rejected on load, it would be linked into the undo tree, then
  -- u_undoredo() acts on its line numbers and u_freeentry() walks ue_array.
  it('rejects corrupted entry (E825)', function()
    local txt = t.tmpname()
    local undo = txt .. '.undo'

    t.write_file(txt, 'one\ntwo\n')
    command('edit ' .. txt)
    command('set undolevels=100')
    command("call setline(1, ['three', 'four'])")
    command('write')
    command('wundo! ' .. undo)

    local blob = assert(t.read_file(undo))
    local entry = assert(find_entry(blob))

    --- Writes `bytes` over `blob` at `pos` and reads it via :rundo.
    local function rundo(pos, bytes)
      t.write_file(undo, blob:sub(1, pos - 1) .. bytes .. blob:sub(pos + #bytes))
      return pcall_err(command, 'rundo ' .. undo)
    end

    -- ue_size larger than the file can hold.
    for _, bad in ipairs({ '\127\255\255\240', '\255\255\255\255' }) do
      eq(
        ('Vim(rundo):E825: Corrupted undo file (entry size): %s'):format(undo),
        rundo(entry + 14, bad)
      )
    end

    -- Negative ue_top/ue_bot/ue_lcount.
    for field = 0, 2 do
      eq(
        ('Vim(rundo):E825: Corrupted undo file (entry lnum): %s'):format(undo),
        rundo(entry + 2 + field * 4, '\255\255\255\251')
      )
    end
  end)
end)