local vim = assert(vim)
local M = {}

local cons = "tnshrdlcumwfgypkbvjxqz" -- 21
local vowel = "aeiou" -- 5

local hsel1 = "tnshrdlcumwfgypkbvjxqz" -- 21
local hsel2 = "aeiou" -- 5

local function char_at(s, i)
  local m = (i % #s) + 1
  return string.sub(s, m, m)
end

local function new_panel(buf, row, col, width, height)
  local w = vim.api.nvim_open_win(buf, false, {
    relative = 'win',
    row = row,
    col = col,
    width = width,
    height = height,
    focusable = true,
    style = 'minimal'
  })
  vim.api.nvim_win_set_option(w, "winhighlight", "Normal:WarpNormal")
  return w
end

M.open_vertical = function()
  local current_win = vim.api.nvim_get_current_win()
  local height = vim.api.nvim_win_get_height(current_win)
  local topline = vim.fn.line('w0')
  local width_of_garbage = vim.fn.getwininfo(current_win)[1].textoff

  M.row_map = {}

  M.vert_buf = vim.api.nvim_create_buf(0, 1)
  local line = 0
  M.vert_lines = {}
  local real_width = math.max(3, width_of_garbage)
  while line < height do
    local t = char_at(cons, line) .. char_at(vowel, line)
    table.insert(M.vert_lines, (' '):rep(real_width - 3) .. t .. ' ')
    M.row_map[t] = topline + line
    line = line + 1
  end
  vim.api.nvim_buf_set_lines(M.vert_buf, 0, -1, 0, M.vert_lines)
  return new_panel(M.vert_buf, 0, 0, real_width, height);
end

M.open_horiz = function()
  local current_win = vim.api.nvim_get_current_win()
  local curpos = vim.api.nvim_win_get_cursor(0)
  local topline = vim.fn.line('w0')

  local width_of_garbage = vim.fn.getwininfo(current_win)[1].textoff
  local width = vim.api.nvim_win_get_width(current_win) - width_of_garbage

  M.horiz_bufnr = vim.api.nvim_create_buf(0, 1)
  local line_at = vim.fn.getline(curpos[1])
  local max_width = math.min(width, #line_at + 1)

  return new_panel(M.horiz_bufnr, curpos[1] - topline + 1, width_of_garbage - 1,
                   max_width + 2, 1)
end

M.filter_horiz_string = function(ch)
  local new_horiz_line = ''
  local i = 1

  while i <= #M.horiz_line do
    local curch = char_at(M.horiz_line, i - 1)
    if curch == ch then
      new_horiz_line = new_horiz_line .. char_at(M.horiz_line, i)
    else
      new_horiz_line = new_horiz_line .. ' '
    end
    i = i + 1
  end
  vim.api.nvim_buf_set_lines(M.horiz_bufnr, 0, -1, 0, {' ' .. new_horiz_line})
end

M.filter_vert_text = function(ch)
  local new_vert_text = {}
  for _, t in pairs(M.vert_lines) do
    local str = t:gsub("^%s*" .. ch, function(m) return (' '):rep(#m) end)

    if t:match('^%s*' .. ch) then
      table.insert(new_vert_text, str)
    else
      table.insert(new_vert_text, "")
    end
  end
  M.vert_lines = new_vert_text
  vim.api.nvim_buf_set_lines(M.vert_buf, 0, -1, 0, M.vert_lines)
end

local function next_char()
  vim.cmd("redraw!")
  return vim.fn.nr2char(vim.fn.getchar())
end

M.run = function(strat_fn)
  if not strat_fn then
    strat_fn = require('warp.strategy.default').default_col_strategy
  end

  local current_pos = vim.api.nvim_win_get_cursor(0)
  local old_scroll = vim.o.scrolloff
  vim.o.scrolloff = 0

  (function()
    local w

    local cleanup = function(win)
      vim.api.nvim_buf_delete(vim.api.nvim_win_get_buf(win), {force = true})
    end

    local read_row = function()
      w = M.open_vertical()
      local vch1 = next_char()
      if vch1 == '\x1b' then
        return
      elseif vch1 == '.' then
        return current_pos[1]
      else
        M.filter_vert_text(vch1)
        local vch2 = next_char()
        if vch1 == '\x1b' then return end
        return M.row_map[vch1 .. vch2]
      end
    end

    local r = read_row()
    if w then
      cleanup(w)
      w = nil
    end

    if not r then return end

    vim.api.nvim_win_set_cursor(0, {r, current_pos[2]})

    local strat = strat_fn()
    w = M.open_horiz()
    local disp = strat.display()
    if disp then
      vim.api
          .nvim_buf_set_lines(M.horiz_bufnr, 0, -1, 0, {' ' .. disp})
      local ch = next_char()
      while ch ~= '\x1b' and strat.on_char(ch) do
        vim.api.nvim_buf_set_lines(M.horiz_bufnr, 0, -1, 0,
                                   {' ' .. strat.display()})
        ch = next_char()
      end
    end

    cleanup(w)
  end)()

  vim.o.scrolloff = old_scroll
end

return M