-- some constants people might like to tweak
Text_color = {r=0, g=0, b=0}
Cursor_color = {r=1, g=0, b=0}
Focus_stroke_color = {r=1, g=0, b=0}  -- what mouse is hovering over
Highlight_color = {r=0.7, g=0.7, b=0.9}  -- selected text
Fold_color = {r=0, g=0.6, b=0}
Fold_background_color = {r=0, g=0.7, b=0}

Margin_top = 15
Margin_left = 25
Margin_right = 25

edit = {}

-- run in both tests and a real run
function edit.initialize_state(top, left, right, font_height, line_height)  -- currently always draws to bottom of screen
  local result = {
    -- a line of bifold text consists of an A side and an optional B side, each of which is a string
    -- expanded: whether to show B side
    lines = {{data='', dataB=nil, expanded=nil}},  -- array of lines

    -- Lines can be too long to fit on screen, in which case they _wrap_ into
    -- multiple _screen lines_.

    -- rendering wrapped text lines needs some additional short-lived data per line:
    --   startpos, the index of data the line starts rendering from, can only be >1 for topmost line on screen
    --   starty, the y coord in pixels the line starts rendering from
    --   fragments: snippets of rendered love.graphics.Text, guaranteed to not straddle screen lines
    --   screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line
    line_cache = {},

    -- Given wrapping, any potential location for the text cursor can be described in two ways:
    -- * schema 1: As a combination of line index and position within a line (in utf8 codepoint units)
    -- * schema 2: As a combination of line index, screen line index within the line, and a position within the screen line.
    -- Positions (and screen line indexes) can be in either the A or the B side.
    --
    -- Most of the time we'll only persist positions in schema 1, translating to
    -- schema 2 when that's convenient.
    --
    -- Make sure these coordinates are never aliased, so that changing one causes
    -- action at a distance.
    screen_top1 = {line=1, pos=1, posB=nil},  -- position of start of screen line at top of screen
    cursor1 = {line=1, pos=1, posB=nil},  -- position of cursor
    screen_bottom1 = {line=1, pos=1, posB=nil},  -- position of start of screen line at bottom of screen

    -- cursor coordinates in pixels
    cursor_x = 0,
    cursor_y = 0,

    font_height = font_height,
    line_height = line_height,
    em = App.newText(love.graphics.getFont(), 'm'),  -- widest possible character width

    top = top,
    left = left,
    right = right,
    width = right-left,

    filename = love.filesystem.getUserDirectory()..'/lines.txt',
    next_save = nil,

    -- undo
    history = {},
    next_history = 1,

    -- search
    search_term = nil,
    search_text = nil,
    search_backup = nil,  -- stuff to restore when cancelling search
  }
  return result
end  -- App.initialize_state

function edit.draw(State)
  State.button_handlers = {}
  App.color(Text_color)
  assert(#State.lines == #State.line_cache)
  if not Text.le1(State.screen_top1, State.cursor1) then
    print(State.screen_top1.line, State.screen_top1.pos, State.screen_top1.posB, State.cursor1.line, State.cursor1.pos, State.cursor1.posB)
    assert(false)
  end
  State.cursor_x = nil
  State.cursor_y = nil
  local y = State.top
--?   print('== draw')
  for line_index = State.screen_top1.line,#State.lines do
    local line = State.lines[line_index]
--?     print('draw:', y, line_index, line)
    if y + State.line_height > App.screen.height then break end
    State.screen_bottom1 = {line=line_index, pos=nil, posB=nil}
--?     print('text.draw', y, line_index)
    local startpos, startposB = 1, nil
    if line_index == State.screen_top1.line then
      if State.screen_top1.pos then
        startpos = State.screen_top1.pos
      else
        startpos, startposB = nil, State.screen_top1.posB
      end
    end
    y, State.screen_bottom1.pos, State.screen_bottom1.posB = Text.draw(State, line_index, y, startpos, startposB)
    y = y + State.line_height
--?     print('=> y', y)
  end
  if State.search_term then
    Text.draw_search_bar(State)
  end
end

function edit.update(State, dt)
  if State.next_save and State.next_save < App.getTime() then
    save_to_disk(State)
    State.next_save = nil
  end
end

function schedule_save(State)
  if State.next_save == nil then
    State.next_save = App.getTime() + 3  -- short enough that you're likely to still remember what you did
  end
end

function edit.quit(State)
  -- make sure to save before quitting
  if State.next_save then
    save_to_disk(State)
  end
end

function edit.mouse_pressed(State, x,y, mouse_button)
  if State.search_term then return end
--?   print('press', State.selection1.line, State.selection1.pos)
  if mouse_press_consumed_by_any_button_handler(State, x,y, mouse_button) then
    -- press on a button and it returned 'true' to short-circuit
    return
  end

  for line_index,line in ipairs(State.lines) do
    if Text.in_line(State, line_index, x,y) then
      local pos,posB = Text.to_pos_on_line(State, line_index, x, y)
--?       print(x,y, 'setting cursor:', line_index, pos, posB)
      State.cursor1 = {line=line_index, pos=pos, posB=posB}
      break
    end
  end
end

function edit.mouse_released(State, x,y, mouse_button)
end

function edit.textinput(State, t)
  for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
  if State.search_term then
    State.search_term = State.search_term..t
    State.search_text = nil
    Text.search_next(State)
  else
    Text.textinput(State, t)
  end
  schedule_save(State)
end

function edit.keychord_pressed(State, chord, key)
  if State.search_term then
    if chord == 'escape' then
      State.search_term = nil
      State.search_text = nil
      State.cursor1 = State.search_backup.cursor
      State.screen_top1 = State.search_backup.screen_top
      State.search_backup = nil
      Text.redraw_all(State)  -- if we're scrolling, reclaim all fragments to avoid memory leaks
    elseif chord == 'return' then
      State.search_term = nil
      State.search_text = nil
      State.search_backup = nil
    elseif chord == 'backspace' then
      local len = utf8.len(State.search_term)
      local byte_offset = Text.offset(State.search_term, len)
      State.search_term = string.sub(State.search_term, 1, byte_offset-1)
      State.search_text = nil
    elseif chord == 'down' then
      if State.cursor1.pos then
        State.cursor1.pos = State.cursor1.pos+1
      else
        State.cursor1.posB = State.cursor1.posB+1
      end
      Text.search_next(State)
    elseif chord == 'up' then
      Text.search_previous(State)
    end
    return
  elseif chord == 'C-f' then
    State.search_term = ''
    State.search_backup = {
      cursor={line=State.cursor1.line, pos=State.cursor1.pos, posB=State.cursor1.posB},
      screen_top={line=State.screen_top1.line, pos=State.screen_top1.pos, posB=State.screen_top1.posB},
    }
    assert(State.search_text == nil)
  -- bifold text
  elseif chord == 'C-b' then
    State.expanded = not State.expanded
    Text.redraw_all(State)
    if not State.expanded then
      for _,line in ipairs(State.lines) do
        line.expanded = nil
      end
      edit.eradicate_locations_after_the_fold(State)
    end
  elseif chord == 'C-d' then
    if State.cursor1.posB == nil then
      local before = snapshot(State, State.cursor1.line)
      if State.lines[State.cursor1.line].dataB == nil then
        State.lines[State.cursor1.line].dataB = ''
      end
      State.lines[State.cursor1.line].expanded = true
      State.cursor1.pos = nil
      State.cursor1.posB = 1
      if Text.cursor_out_of_screen(State) then
        Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
      end
      schedule_save(State)
      record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
    end
  -- zoom
  elseif chord == 'C-=' then
    edit.update_font_settings(State, State.font_height+2)
    Text.redraw_all(State)
  elseif chord == 'C--' then
    edit.update_font_settings(State, State.font_height-2)
    Text.redraw_all(State)
  elseif chord == 'C-0' then
    edit.update_font_settings(State, 20)
    Text.redraw_all(State)
  -- undo
  elseif chord == 'C-z' then
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    local event = undo_event(State)
    if event then
      local src = event.before
      State.screen_top1 = deepcopy(src.screen_top)
      State.cursor1 = deepcopy(src.cursor)
      patch(State.lines, event.after, event.before)
      patch_placeholders(State.line_cache, event.after, event.before)
      -- if we're scrolling, reclaim all fragments to avoid memory leaks
      Text.redraw_all(State)
      schedule_save(State)
    end
  elseif chord == 'C-y' then
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    local event = redo_event(State)
    if event then
      local src = event.after
      State.screen_top1 = deepcopy(src.screen_top)
      State.cursor1 = deepcopy(src.cursor)
      patch(State.lines, event.before, event.after)
      -- if we're scrolling, reclaim all fragments to avoid memory leaks
      Text.redraw_all(State)
      schedule_save(State)
    end
  -- clipboard
  elseif chord == 'C-c' then
    local s = Text.selection(State)
    if s then
      App.setClipboardText(s)
    end
  elseif chord == 'C-x' then
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    local s = Text.cut_selection(State, State.left, State.right)
    if s then
      App.setClipboardText(s)
    end
    schedule_save(State)
  elseif chord == 'C-v' then
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    -- We don't have a good sense of when to scroll, so we'll be conservative
    -- and sometimes scroll when we didn't quite need to.
    local before_line = State.cursor1.line
    local before = snapshot(State, before_line)
    local clipboard_data = App.getClipboardText()
    for _,code in utf8.codes(clipboard_data) do
      local c = utf8.char(code)
      if c == '\n' then
        Text.insert_return(State)
      else
        Text.insert_at_cursor(State, c)
      end
    end
    if Text.cursor_out_of_screen(State) then
      Text.snap_cursor_to_bottom_of_screen(State, State.left, State.right)
    end
    schedule_save(State)
    record_undo_event(State, {before=before, after=snapshot(State, before_line, State.cursor1.line)})
  -- dispatch to text
  else
    for _,line_cache in ipairs(State.line_cache) do line_cache.starty = nil end  -- just in case we scroll
    Text.keychord_pressed(State, chord)
  end
end

function edit.eradicate_locations_after_the_fold(State)
  -- eradicate side B from any locations we track
  if State.cursor1.posB then
    State.cursor1.posB = nil
    State.cursor1.pos = utf8.len(State.lines[State.cursor1.line].data)
    State.cursor1.pos = Text.pos_at_start_of_screen_line(State, State.cursor1)
  end
  if State.screen_top1.posB then
    State.screen_top1.posB = nil
    State.screen_top1.pos = utf8.len(State.lines[State.screen_top1.line].data)
    State.screen_top1.pos = Text.pos_at_start_of_screen_line(State, State.screen_top1)
  end
end

function edit.key_released(State, key, scancode)
end

function edit.update_font_settings(State, font_height)
  State.font_height = font_height
  love.graphics.setFont(love.graphics.newFont(Editor_state.font_height))
  State.line_height = math.floor(font_height*1.3)
  State.em = App.newText(love.graphics.getFont(), 'm')
  Text_cache = {}
end

--== some methods for tests

Test_margin_left = 25

function edit.initialize_test_state()
  -- if you change these values, tests will start failing
  return edit.initialize_state(
      15,  -- top margin
      Test_margin_left,
      App.screen.width,  -- right margin = 0
      14,  -- font height assuming default LÖVE font
      15)  -- line height
end

-- all textinput events are also keypresses
-- TODO: handle chords of multiple keys
function edit.run_after_textinput(State, t)
  edit.keychord_pressed(State, t)
  edit.textinput(State, t)
  edit.key_released(State, t)
  App.screen.contents = {}
  edit.draw(State)
end

-- not all keys are textinput
function edit.run_after_keychord(State, chord)
  edit.keychord_pressed(State, chord)
  edit.key_released(State, chord)
  App.screen.contents = {}
  edit.draw(State)
end

function edit.run_after_mouse_click(State, x,y, mouse_button)
  App.fake_mouse_press(x,y, mouse_button)
  edit.mouse_pressed(State, x,y, mouse_button)
  App.fake_mouse_release(x,y, mouse_button)
  edit.mouse_released(State, x,y, mouse_button)
  App.screen.contents = {}
  edit.draw(State)
end

function edit.run_after_mouse_press(State, x,y, mouse_button)
  App.fake_mouse_press(x,y, mouse_button)
  edit.mouse_pressed(State, x,y, mouse_button)
  App.screen.contents = {}
  edit.draw(State)
end

function edit.run_after_mouse_release(State, x,y, mouse_button)
  App.fake_mouse_release(x,y, mouse_button)
  edit.mouse_released(State, x,y, mouse_button)
  App.screen.contents = {}
  edit.draw(State)
end