local core = require "core"
local command = require "core.command"

local vim = {}

local command_buffer = {verb = '', mult_accu = '', inside = ''}

function command_buffer:reset()
  self.verb = ''
  self.mult_accu = ''
  self.inside = ''
end

function command_buffer:mult()
  return self.mult_accu == '' and 1 or tostring(self.mult_accu)
end

function command_buffer:add_mult_char(k)
  self.mult_accu = self.mult_accu .. k
end

local function table_find(t, e)
  for i = 1, #t do
    if t[i] == e then return i end
  end
end

local verbs_obj = {'c', 'd', 'r', 'y'}
local verbs_imm = {'a', 'h', 'i', 'j', 'k', 'l', 'o', 'p', 'u', 'v', 'x', 'O',
  'left', 'right', 'up', 'down', 'escape'}

local vim_objects = {'a', 'b', 'd', 'e', 'i', 'w', 'y', '^', '0', '$'}

local vim_object_map = {
  ['b'] = 'start-of-word',
  ['e'] = 'next-word-end',
  ['w'] = 'next-word-begin',
  ['$'] = 'end-of-line',
  ['^'] = 'start-of-line-content',
  ['0'] = 'start-of-line',
}

local inside_delims = {
  [')'] = {'(', ')'},
  [']'] = {'[', ']'},
  ['}'] = {'{', '}'},
  ['>'] = {'<', '>'},
  ['"'] = {'"', '"'},
  ["'"] = {"'", "'"},
}

local vim_previous_command

local function doc_command(action, command)
  return 'doc:' .. action .. '-' .. command
end

local function vim_execute(mode, verb, mult, object)
  vim_previous_command = {verb, mult, object}
  local action = (mode == 'command' and 'move-to' or 'select-to')
  if verb == '' then
    if object == '$' then
      command.perform_many(mult - 1, doc_command(action, 'next-line'))
      command.perform(doc_command(action, 'end-of-line'))
    else
      if object == 'e' then
        command.perform(doc_command(action, 'next-char'))
      end
      command.perform_many(mult, doc_command(action, vim_object_map[object]))
      if object == 'e' then
        command.perform(doc.command(action, 'previous-char'))
      end
    end
  elseif verb == 'd' or verb == 'y' then
    if mode == 'command' then -- d and y act as immediate mode commands in visual mode
      if object == '$' then
        command.perform_many(mult - 1, 'doc:select-to-next-line')
        command.perform('doc:select-to-end-of-line')
      elseif object == verb then
        command.perform('doc:move-to-start-of-line')
        command.perform_many(mult, 'doc:select-to-next-line')
      else
        command.perform_many(mult, 'doc:select-to-' .. vim_object_map[object])
      end
    end
    command.perform('doc:copy')
    if verb == 'd' then
      command.perform('doc:cut')
    else
      command.perform('doc:move-to-start-of-selection')
    end
    command.perform('core:set-command-mode')
  elseif verb == 'c' then
    command.perform_many(mult, 'doc:select-to-' .. vim_object_map[object])
    command.perform('doc:copy')
    command.perform('doc:cut')
    command.perform('core:set-insert-mode')
  elseif verb == 'h' or verb == 'left' then
    command.perform_many(mult, doc_command(action, 'previous-char'))
  elseif verb == 'j' or verb == 'down' then
    command.perform_many(mult, doc_command(action, 'next-line'))
  elseif verb == 'k' or verb == 'up' then
    command.perform_many(mult, doc_command(action, 'previous-line'))
  elseif verb == 'l' or verb == 'right' then
    command.perform_many(mult, doc_command(action, 'next-char'))
  elseif verb == 'x' then
    command.perform_many(mult, 'doc:delete')
  elseif verb == 'a' then
    command.perform('core:set-insert-mode')
    command.perform('doc:move-to-next-char')
  elseif verb == 'i' then
    command.perform('core:set-insert-mode')
  elseif verb == 'o' then
    command.perform('doc:move-to-end-of-line')
    command.perform('doc:newline')
    command.perform('core:set-insert-mode')
  elseif verb == 'O' then
    command.perform('doc:move-to-start-of-line')
    command.perform('doc:newline')
    command.perform('doc:move-to-previous-line')
    command.perform('core:set-insert-mode')
  elseif verb == 'p' then
    command.perform('doc:paste')
  elseif verb == 'u' then
    command.perform('doc:undo')
  elseif verb == 'v' then
    command.perform('core:set-visual-mode')
  elseif verb == 'y' then
    command.perform('doc:copy')
    command.perform('doc:move-to-start-of-selection')
    command.perform('core:set-command-mode')
  elseif verb == 'escape' then
    command.perform('doc:move-to-end-of-selection')
    command.perform('core:set-command-mode')
  else
    return false
  end
  return true
end

function vim.on_text_input(mode, text_raw, stroke)
  local text = text_raw or stroke
  local byte = text_raw and string.byte(text_raw)
  local byte0, byte9 = string.byte('0'), string.byte('9')
  local view = core.active_view
  local doc = view.doc
  if mode == 'command' or mode == 'visual' then
    if command_buffer.inside ~= '' and inside_delims[text] then
      -- got character for inside delimiter edits
      local outer = command_buffer.inside == 'a'
      doc:select_with_delimiters(inside_delims[text], outer)
      command.perform('doc:delete')
      if command_buffer.verb == 'c' then
        view:set_editing_mode('insert')
      end
      command_buffer:reset()
      return true
    elseif command_buffer.verb == 'r' then
      if text_raw then
        command.perform('doc:delete')
        local line, col = doc:get_selection()
        doc:insert(line, col, text_raw)
        command_buffer:reset()
        return true
      end
    elseif text == '.' then
      if vim_previous_command then
        vim_execute(mode, unpack(vim_previous_command))
        return true
      end
    elseif command_buffer.verb == '' and table_find(verbs_imm, text) then
      -- execute immediate vim command
      vim_execute(mode, text, command_buffer:mult())
      command_buffer:reset()
      return true
    elseif command_buffer.verb == '' and table_find(verbs_obj, text) then
      -- vim command that takes an object
      if mode == 'command' then
        -- store the command without executing
        command_buffer.verb = text
      else
        -- visual mode: execute the command
        vim_execute(mode, text, command_buffer:mult())
        command_buffer:reset()
      end
      return true
    elseif text_raw and byte
    and (byte > byte0 or command_buffer.mult_accu ~= '' and byte == byte0)
    and byte <= byte9 then
      -- numeric command multiplier
      command_buffer:add_mult_char(text_raw)
      return true
    elseif table_find(vim_objects, text) then
      -- object of a verb
      if text == 'i' or text == 'a' then
        command_buffer.inside = text
      else
        vim_execute(mode, command_buffer.verb, command_buffer:mult(), text)
        command_buffer:reset()
      end
      return true
    elseif stroke == 'escape' then
      core.active_view:set_editing_mode('command')
      command_buffer:reset()
      return true
    end
  elseif mode == 'insert' then
    if stroke == 'escape' or stroke == 'ctrl+c' then
      core.active_view:set_editing_mode('command')
      return true
    end
    if stroke == 'backspace' then
      command.perform('doc:backspace')
    end
  end
  return false
end

return vim