local t = require('test.unit.testutil')
local describe, before_each = t.describe, t.before_each
local itp = t.gen_itp(t.it)

local ffi = t.ffi
local eq = t.eq
local to_cstr = t.to_cstr

local lib = t.cimport(
  './src/nvim/mbyte.h',
  './src/nvim/charset.h',
  './src/nvim/grid.h',
  './src/nvim/option_vars.h'
)

describe('mbyte', function()
  -- Convert from bytes to string
  local function to_string(bytes)
    local s = {}
    for i = 1, #bytes do
      s[i] = string.char(bytes[i])
    end
    return table.concat(s)
  end

  before_each(function() end)

  itp('utf_ptr2char', function()
    -- For strings with length 1 the first byte is returned.
    for c = 0, 255 do
      eq(c, lib.utf_ptr2char(to_string({ c, 0 })))
    end

    -- Some ill formed byte sequences that should not be recognized as UTF-8
    -- First byte: 0xc0 or 0xc1
    -- Second byte: 0x80 .. 0xbf
    --eq(0x00c0, lib.utf_ptr2char(to_string({0xc0, 0x80})))
    --eq(0x00c1, lib.utf_ptr2char(to_string({0xc1, 0xbf})))
    --
    -- Sequences with more than four bytes
  end)

  for n = 0, 0xF do
    itp(('utf_char2bytes for chars 0x%x - 0x%x'):format(n * 0x1000, n * 0x1000 + 0xFFF), function()
      local char_p = ffi.typeof('char[?]')
      for c = n * 0x1000, n * 0x1000 + 0xFFF do
        local p = char_p(4, 0)
        lib.utf_char2bytes(c, p)
        eq(c, lib.utf_ptr2char(p))
        eq(lib.vim_iswordc(c), lib.vim_iswordp(p))
      end
    end)
  end

  describe('utfc_ptr2schar', function()
    local function test_seq(seq)
      local firstc = ffi.new('int[1]')
      local buf = ffi.new('char[32]')
      lib.schar_get(buf, lib.utfc_ptr2schar(to_string(seq), firstc))
      local str = ffi.string(buf)
      if 1 > 2 then -- for debugging
        local tbl = {}
        for i = 1, #str do
          table.insert(tbl, string.format('0x%02x', string.byte(str, i)))
        end
        print('{ ' .. table.concat(tbl, ', ') .. ' }')
        io.stdout:flush()
      end
      return { str, firstc[0] }
    end

    local function byte(val)
      return { string.char(val), val }
    end

    itp('1-byte sequences', function()
      eq({ '', 0 }, test_seq { 0 })
      for c = 1, 127 do
        eq(byte(c), test_seq { c })
      end
      for c = 128, 255 do
        eq({ '', c }, test_seq { c })
      end
    end)

    itp('2-byte sequences', function()
      -- No combining characters
      eq(byte(0x7f), test_seq { 0x7f, 0x7f })
      -- No combining characters
      eq(byte(0x7f), test_seq { 0x7f, 0x80 })

      -- No UTF-8 sequence
      eq({ '', 0xc2 }, test_seq { 0xc2, 0x7f })
      -- One UTF-8 character
      eq({ '\xc2\x80', 0x80 }, test_seq { 0xc2, 0x80 })
      -- No UTF-8 sequence
      eq({ '', 0xc2 }, test_seq { 0xc2, 0xc0 })
    end)

    itp('3-byte sequences', function()
      -- No second UTF-8 character
      eq(byte(0x7f), test_seq { 0x7f, 0x80, 0x80 })
      -- No combining character
      eq(byte(0x7f), test_seq { 0x7f, 0xc2, 0x80 })

      -- Combining character is U+0300
      eq({ '\x29\xcc\x80', 0x29 }, test_seq { 0x29, 0xcc, 0x80 })
      -- invalid start byte for combining
      eq({ '\x7f', 0x7f }, test_seq { 0x7f, 0xcc, 0x80 })

      -- No UTF-8 sequence
      eq({ '', 0xc2 }, test_seq { 0xc2, 0x7f, 0xcc })
      -- Incomplete combining character
      eq({ '\xc2\x80', 0x80 }, test_seq { 0xc2, 0x80, 0xcc })

      -- One UTF-8 character (composing only)
      eq({ ' \xe2\x83\x90', 0x20d0 }, test_seq { 0xe2, 0x83, 0x90 })
    end)

    itp('4-byte sequences', function()
      -- No following combining character
      eq(byte(0x7f), test_seq { 0x7f, 0x7f, 0xcc, 0x80 })
      eq(byte(0x29), test_seq { 0x29, 0x29, 0xcc, 0x80 })
      -- No second UTF-8 character
      eq(byte(0x7f), test_seq { 0x7f, 0xc2, 0xcc, 0x80 })

      -- Combining character U+0300
      eq({ '\x29\xcc\x80', 0x29 }, test_seq { 0x29, 0xcc, 0x80, 0xcc })

      -- No UTF-8 sequence
      eq({ '', 0xc2 }, test_seq { 0xc2, 0x7f, 0xcc, 0x80 })
      -- No following UTF-8 character
      eq({ '\xc2\x80', 0x80 }, test_seq { 0xc2, 0x80, 0xcc, 0xcc })
      -- Combining character U+0301
      eq({ '\xc2\xbc\xcc\x81', 0xbc }, test_seq { 0xc2, 0xbc, 0xcc, 0x81 })
      -- U+0080 : not a valid start char
      eq({ '\xc2\x80', 0x80 }, test_seq { 0xc2, 0x80, 0xcc, 0x81 })

      -- One UTF-8 character
      eq({ '\xf4\x80\x80\x80', 0x100000 }, test_seq { 0xf4, 0x80, 0x80, 0x80 })
    end)

    itp('5+-byte sequences', function()
      -- No following combining character
      eq(byte(0x7f), test_seq { 0x7f, 0x7f, 0xcc, 0x80, 0x80 })
      -- No second UTF-8 character
      eq(byte(0x7f), test_seq { 0x7f, 0xc2, 0xcc, 0x80, 0x80 })

      -- Combining character U+0300
      eq({ '\x29\xcc\x80', 0x29 }, test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x00 })

      -- Combining characters U+0300 and U+0301
      eq({ '\x29\xcc\x80\xcc\x81', 0x29 }, test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x81 })
      -- Combining characters U+0300, U+0301, U+0302
      eq(
        { '\x29\xcc\x80\xcc\x81\xcc\x82', 0x29 },
        test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x81, 0xcc, 0x82 }
      )
      -- Combining characters U+0300, U+0301, U+0302, U+0303
      eq(
        { '\x29\xcc\x80\xcc\x81\xcc\x82\xcc\x83', 0x29 },
        test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x81, 0xcc, 0x82, 0xcc, 0x83 }
      )
      -- Combining characters U+0300, U+0301, U+0302, U+0303, U+0304
      eq(
        { '\x29\xcc\x80\xcc\x81\xcc\x82\xcc\x83\xcc\x84', 0x29 },
        test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x81, 0xcc, 0x82, 0xcc, 0x83, 0xcc, 0x84 }
      )
      -- Combining characters U+0300, U+0301, U+0302, U+0303, U+0304, U+0305
      eq(
        { '\x29\xcc\x80\xcc\x81\xcc\x82\xcc\x83\xcc\x84\xcc\x85', 0x29 },
        test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x81, 0xcc, 0x82, 0xcc, 0x83, 0xcc, 0x84, 0xcc, 0x85 }
      )

      -- Combining characters U+0300, U+0301, U+0302, U+0303, U+0304, U+0305, U+0306
      eq(
        { '\x29\xcc\x80\xcc\x81\xcc\x82\xcc\x83\xcc\x84\xcc\x85\xcc\x86', 0x29 },
        test_seq {
          0x29,
          0xcc,
          0x80,
          0xcc,
          0x81,
          0xcc,
          0x82,
          0xcc,
          0x83,
          0xcc,
          0x84,
          0xcc,
          0x85,
          0xcc,
          0x86,
        }
      )

      -- Only three following combining characters U+0300, U+0301, U+0302
      eq(
        { '\x29\xcc\x80\xcc\x81\xcc\x82', 0x29 },
        test_seq { 0x29, 0xcc, 0x80, 0xcc, 0x81, 0xcc, 0x82, 0xc2, 0x80, 0xcc, 0x84, 0xcc, 0x85 }
      )

      -- No UTF-8 sequence
      eq({ '', 0xc2 }, test_seq { 0xc2, 0x7f, 0xcc, 0x80, 0x80 })
      -- No following UTF-8 character
      eq({ '\xc2\xbc', 0xbc }, test_seq { 0xc2, 0xbc, 0xcc, 0xcc, 0x80 })
      -- Combining character U+0301
      eq({ '\xc2\xbc\xcc\x81', 0xbc }, test_seq { 0xc2, 0xbc, 0xcc, 0x81, 0x7f })
      -- Combining character U+0301
      eq({ '\xc2\xbc\xcc\x81', 0xbc }, test_seq { 0xc2, 0xbc, 0xcc, 0x81, 0xcc })

      -- One UTF-8 character
      eq({ '\xf4\x80\x80\x80', 0x100000 }, test_seq { 0xf4, 0x80, 0x80, 0x80, 0x7f })

      -- One UTF-8 character
      eq({ '\xf4\x80\x80\x80', 0x100000 }, test_seq { 0xf4, 0x80, 0x80, 0x80, 0x80 })
      -- One UTF-8 character
      eq({ '\xf4\x80\x80\x80', 0x100000 }, test_seq { 0xf4, 0x80, 0x80, 0x80, 0xcc })

      -- Combining characters U+1AB0 and U+0301
      eq(
        { '\xf4\x80\x80\x80\xe1\xaa\xb0\xcc\x81', 0x100000 },
        test_seq { 0xf4, 0x80, 0x80, 0x80, 0xe1, 0xaa, 0xb0, 0xcc, 0x81 }
      )
    end)
  end)

  describe('utf_cp_bounds_len', function()
    local tests = {
      {
        name = 'for valid string',
        str = 'iÀiiⱠiⱠⱠ𐀀i',
        offsets = {
          b = { 0, 0, 1, 0, 0, 0, 1, 2, 0, 0, 1, 2, 0, 1, 2, 0, 1, 2, 3, 0 },
          e = { 1, 2, 1, 1, 1, 3, 2, 1, 1, 3, 2, 1, 3, 2, 1, 4, 3, 2, 1, 1 },
        },
      },
      {
        name = 'for string with incomplete sequence',
        str = 'i\xC3iÀⱠiÀ\xE2\xB1Ⱡ\xF0\x90\x80',
        offsets = {
          b = { 0, 0, 0, 0, 1, 0, 1, 2, 0, 0, 1, 0, 0, 0, 1, 2, 0, 0, 0 },
          e = { 1, 1, 1, 2, 1, 3, 2, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 1, 1 },
        },
      },
      {
        name = 'for string with trailing bytes after multibyte',
        str = 'iÀ\xA0Ⱡ\xA0Ⱡ𐀀\xA0i',
        offsets = {
          b = { 0, 0, 1, 0, 0, 1, 2, 0, 0, 1, 2, 0, 1, 2, 3, 0, 0 },
          e = { 1, 2, 1, 1, 3, 2, 1, 1, 3, 2, 1, 4, 3, 2, 1, 1, 1 },
        },
      },
    }

    for _, test in ipairs(tests) do
      itp(test.name, function()
        local cstr = to_cstr(test.str)
        local b_offsets, e_offsets = {}, {}
        for i = 1, #test.str do
          local result = lib.utf_cp_bounds_len(cstr, cstr + i - 1, #test.str - (i - 1))
          table.insert(b_offsets, result.begin_off)
          table.insert(e_offsets, result.end_off)
        end
        eq(test.offsets, { b = b_offsets, e = e_offsets })
      end)
    end

    itp('does not read before start', function()
      local str = '𐀀'
      local expected_offsets = { b = { 0, 0, 0 }, e = { 1, 1, 1 } }
      local cstr = to_cstr(str) + 1
      local b_offsets, e_offsets = {}, {}
      for i = 1, 3 do
        local result = lib.utf_cp_bounds_len(cstr, cstr + i - 1, 3 - (i - 1))
        table.insert(b_offsets, result.begin_off)
        table.insert(e_offsets, result.end_off)
      end
      eq(expected_offsets, { b = b_offsets, e = e_offsets })
    end)

    itp('does not read past the end', function()
      local str = '𐀀'
      local expected_offsets = { b = { 0, 0, 0 }, e = { 1, 1, 1 } }
      local cstr = to_cstr(str)
      local b_offsets, e_offsets = {}, {}
      for i = 1, 3 do
        local result = lib.utf_cp_bounds_len(cstr, cstr + i - 1, 3 - (i - 1))
        table.insert(b_offsets, result.begin_off)
        table.insert(e_offsets, result.end_off)
      end
      eq(expected_offsets, { b = b_offsets, e = e_offsets })
    end)
  end)

  describe('utf_ptr2cells', function()
    local function check(str, expected)
      -- TODO: rework a better test structure for the new world
      -- of bounded and unbounded CharInfo iterators
      eq(expected, lib.utf_ptr2cells(to_cstr(str)))
      -- this a bit of a cop-out (string not cluster), but see above
      eq(expected, lib.mb_string2cells_len(to_cstr(str), #str))
    end

    itp('gives a spacing mark its own cell', function()
      check('ำ', 1)
      check('ท', 1)
      check('ทำ', 2)
      check('का', 2)
    end)

    itp('gives the halfwidth katakana sound marks their own cell', function()
      check('ｶ', 1)
      check('ｶﾞ', 2)
      check('ﾊﾟ', 2) -- U+FF9F, the semi-voiced mark
    end)

    itp('does not widen clusters of non-spacing marks', function()
      check('ท่', 1)
      check('é', 1) -- decomposed, so the acute joins the cluster
    end)

    itp('clamps to the maximum cells per cluster', function()
      check('ทำำ', 2)
    end)

    itp('leaves double-width and illegal bytes alone', function()
      check('漢', 2)
      eq(4, lib.utf_ptr2cells(to_cstr('\xff'))) -- illegal byte, shown as <ff>
    end)
  end)

  itp('utf_head_off', function()
    local function check(str, expected_glyphs)
      local len = #str
      local cstr = to_cstr(str)
      local breaks = { 0 } -- SOT
      local pos = 0
      local mb_glyphs = {}
      while pos < len do
        local clen = lib.utfc_ptr2len(cstr + pos)
        if clen == 0 then
          eq(0, string.byte(str, pos + 1)) -- only NUL bytes can has length zery
          clen = 1 -- but skip it, otherwise we get stuck
        end
        if clen > 1 then
          table.insert(mb_glyphs, string.sub(str, pos + 1, pos + clen))
        end
        pos = pos + clen
        table.insert(breaks, pos)
      end
      eq(len, breaks[#breaks]) -- include EOT as break
      -- we could also send in breaks, but this is more human readable
      eq(expected_glyphs, mb_glyphs)

      for i = 1, #breaks - 1 do
        local start, next = breaks[i], breaks[i + 1]

        for p = start, next - 1 do
          eq(p - start, lib.utf_head_off(cstr, cstr + p))
        end
      end
      eq(0, lib.utf_head_off(cstr, cstr + len)) -- NUL byte is safe
    end
    -- stylua doesn't like ZWJ chars..
    -- stylua: ignore start
    check('hej och hå 🧑‍🌾!', { 'å', '🧑‍🌾' })

    -- emoji (various kinds of combinations, use g8 to see them)
    check("🏳️‍⚧️🧑‍🌾❤️😂🏴‍☠️", {"🏳️‍⚧️", "🧑‍🌾", "❤️", "😂", "🏴‍☠️"})
    check('🏳️‍⚧️xy🧑‍🌾\r❤️😂å🏴‍☠️€', { '🏳️‍⚧️', '🧑‍🌾', '❤️', '😂', 'å', '🏴‍☠️', '€' })
    check('🏳️‍⚧️\000🧑‍🌾\000❤️\000😂\000å\000🏴‍☠️\000€', { '🏳️‍⚧️', '🧑‍🌾', '❤️', '😂', 'å', '🏴‍☠️', '€' })
    check('\195🏳️‍⚧️\198🧑‍🌾\165❤️\168\195😂\255🏴‍☠️\129€\165', { '🏳️‍⚧️', '🧑‍🌾', '❤️', '😂', '🏴‍☠️', '€' })

    check('🇦🅱️ 🇦🇽 🇦🇨🇦 🇲🇽🇹🇱',{'🇦', '🅱️', '🇦🇽', '🇦🇨', '🇦', '🇲🇽', '🇹🇱'})
    check('🏴󠁧󠁢󠁳󠁣󠁴󠁿🏴󠁧󠁢󠁷󠁬󠁳󠁿', {'🏴󠁧󠁢󠁳󠁣󠁴󠁿', '🏴󠁧󠁢󠁷󠁬󠁳󠁿'})

    check('å\165ü\195aëq\168β\000\169本\255', {'å', 'ü', 'ë', 'β', '本'})

    lib.p_arshape = true -- default
    check('سلام', { 'س', 'لا', 'م' })
    lib.p_arshape = false
    check('سلام', { 'س', 'ل', 'ا', 'م' })

    check('L̓̉̑̒̌̚ơ̗̌̒̄̀ŕ̈̈̎̐̕è̇̅̄̄̐m̖̟̟̅̄̚', {'L̓̉̑̒̌̚', 'ơ̗̌̒̄̀', 'ŕ̈̈̎̐̕', 'è̇̅̄̄̐', 'm̖̟̟̅̄̚'})
    -- stylua: ignore end
  end)

  describe('utf_fold', function()
    itp('does not crash with surrogates #30527', function()
      eq(0xddfb, lib.utf_fold(0xddfb)) -- low surrogate, invalid as a character
      eq(0xd800, lib.utf_fold(0xd800)) -- high surrogate, invalid as a character
    end)

    itp("doesn't crash on invalid codepoints", function()
      eq(9000000, lib.utf_fold(9000000))
      eq(0, lib.utf_fold(0))
    end)
  end)
end)