local startup = {}
local ns = vim.api.nvim_create_namespace("startup")
-- tables with tables: {line, align, cursor should move on, highlight}
startup.lines = {}
startup.formatted_text = {}
startup.sections = {}
startup.section_highlights = {}
startup.open_sections = {}
startup.good_lines = {}
startup.settings = require("startup.config")

local get_cur_line = vim.api.nvim_get_current_line

---set option in buffer
local set_buf_opt = vim.api.nvim_buf_set_option

local section_alignments = {}
local sections_with_mappings = {}

local startup_nvim_displayed
local startup_nvim_loaded

local current_section = ""

local opts = { noremap = true, silent = true }
local settings = require("startup.config")

---@type startup.utils
local utils = require("startup.utils")

---creates a mapping for the current buffer
---@param mapping string the mapping to use
---@param command string the command to be mapped
local buf_map = function(mapping, command)
  vim.api.nvim_buf_set_keymap(0, "n", mapping, command, opts)
end

---open fold under cursor
function startup.open_section()
  set_buf_opt(0, "modifiable", true)
  local line_nr = vim.api.nvim_win_get_cursor(0)[1]
  local section_name = vim.trim(get_cur_line())
  local section_align = section_alignments[section_name]
  local section_highlight = startup.section_highlights[section_name]
  local section_entries = startup.sections[section_name]
  if section_entries == nil or section_name == "" then
    return
  end
  section_entries = startup.align(section_entries, section_align)
  for i, section in ipairs(startup.open_sections) do
    if section == section_name then
      vim.api.nvim_buf_set_lines(
        0,
        line_nr,
        line_nr + #section_entries,
        false,
        {}
      )
      table.remove(startup.open_sections, i)
      return
    end
  end
  vim.api.nvim_buf_set_lines(0, line_nr, line_nr, false, section_entries)
  for number, _ in ipairs(section_entries) do
    vim.api.nvim_buf_add_highlight(
      0,
      ns,
      section_highlight,
      line_nr + number - 1,
      0,
      -1
    )
  end
  table.insert(startup.open_sections, section_name)
  vim.cmd([[silent! %s/\s\+$//]]) -- clear trailing whitespace
  vim.api.nvim_win_set_cursor(0, { line_nr, math.floor(vim.o.columns / 2) })
  set_buf_opt(0, "modifiable", false)
end

local function create_mappings(mappings)
  buf_map(
    settings.mappings.execute_command,
    ":lua require'startup'.check_line()<CR>"
  )
  buf_map(
    settings.mappings.open_file,
    "<cmd>lua require('startup').open_file()<CR>"
  )
  buf_map(
    settings.mappings.open_section,
    "<cmd>lua require'startup'.open_section()<CR>"
  )
  buf_map(
    settings.mappings.open_file_split,
    "<cmd>lua require('startup').open_file_vsplit()<CR>"
  )
  buf_map(
    settings.mappings.open_help,
    "<cmd>lua require'startup.utils'.key_help()<CR>"
  )
  if mappings ~= {} then
    for _, cmd in pairs(mappings) do
      buf_map(cmd[2], "<cmd>" .. cmd[1] .. "<CR>")
    end
  end
end

---ask for a filename and create file
function startup.new_file()
  local name = vim.fn.input("Filename: > ")
  vim.cmd("e " .. name)
end

---check if current line is one of the commands
function startup.check_line()
  local line = get_cur_line()
  for _, section in ipairs(sections_with_mappings) do
    for name, command in pairs(settings[section].content) do
      if line:match(name) then
        vim.cmd(command[1])
      end
    end
  end
end

---open file under cursor
function startup.open_file()
  local filename = get_cur_line()
  vim.cmd("e " .. filename)
end

---open file under cursor in split
function startup.open_file_vsplit()
  local filename = get_cur_line()
  vim.cmd("vsplit " .. filename)
end

---creates a table with the strings in it aligned
---@param dict table the strings to be aligned
---@param alignment string the alignement(left,center or right)
---@return table aligned the aligned strings
function startup.align(dict, alignment)
  local margin_calculated = 0
  local margin = settings.margin and type(settings.margin) == "number" or 5
  if margin < 1 then
    margin_calculated = vim.o.columns * margin
  else
    margin_calculated = margin
  end
  local aligned = {}
  local max_len = utils.longest_line(dict)
  if alignment == "center" then
    local space_left = vim.o.columns - max_len
    for _, line in ipairs(dict) do
      table.insert(aligned, utils.spaces(space_left / 2) .. line)
    end
  elseif alignment == "left" then
    for _, line in ipairs(dict) do
      table.insert(aligned, utils.spaces(margin_calculated) .. line)
    end
  elseif alignment == "right" then
    for _, line in ipairs(dict) do
      table.insert(
        aligned,
        utils.spaces(vim.o.columns - max_len - margin_calculated - 10) .. line
      )
    end
  end
  margin_calculated = 0
  return aligned
end

---creates mapping names from table of mappings
---@param mappings table
---@return table
function startup.mapping_names(mappings)
  local mapnames = {}
  local strings = {}
  for title, command in pairs(mappings) do
    if settings.options.mapping_keys then
      table.insert(strings, title .. command[2])
    else
      table.insert(strings, title)
    end
  end
  local length = utils.longest_line(strings) + 18
  for name, cmd in pairs(mappings) do
    if settings.options.mapping_keys then
      local space = utils.spaces(length - #cmd[2] - #name)
      table.insert(mapnames, name .. space .. cmd[2])
    else
      local space = utils.spaces(length - #name)
      table.insert(mapnames, name .. space)
    end
  end

  return mapnames
end

function startup.display()
  if startup_nvim_displayed then
    return
  end
  startup_nvim_displayed = true
  local padding_nr = 1
  utils.set_buf_options()
  local parts = settings.parts
  vim.cmd([[hi link StartupFoldedSection Special]])
  for _, part in ipairs(parts) do
    utils.empty(settings.options.paddings[padding_nr])
    padding_nr = padding_nr + 1
    current_section = part
    local options = settings[part]
    utils.validate_settings(options)
    if type(options.content) == "function" then
      options.content = options.content()
    end
    if options.highlight == "" then
      vim.cmd(
        "highlight Startup"
          .. part
          .. " guifg="
          .. options.default_color
          .. " guibg="
          .. settings.colors.background
      )
      options.highlight = "Startup" .. part
    end
    if options.type == "text" then
      if options.fold_section then
        section_alignments[vim.trim(options.title)] = options.align
        startup.sections[vim.trim(options.title)] = options.content
        startup.section_highlights[vim.trim(options.title)] = options.highlight
        startup.good_lines[#startup.good_lines + 1] = vim.trim(options.title)
        table.insert(
          startup.lines,
          { options.title, options.align, true, "StartupFoldedSection" }
        )
      else
        for _, line in ipairs(options.content) do
          table.insert(
            startup.lines,
            { line, options.align, false, options.highlight }
          )
        end
      end
    elseif options.type == "mapping" then
      if options.fold_section then
        section_alignments[vim.trim(options.title)] = options.align
        for _, line in ipairs(startup.mapping_names(options.content)) do
          startup.good_lines[#startup.good_lines + 1] = vim.trim(line)
        end
        startup.sections[vim.trim(options.title)] =
          startup.mapping_names(
            options.content
          )
        startup.section_highlights[vim.trim(options.title)] = options.highlight
        startup.good_lines[#startup.good_lines + 1] = vim.trim(options.title)
        table.insert(
          startup.lines,
          { options.title, options.align, true, "StartupFoldedSection" }
        )
        for _, line in ipairs(options.content) do
          startup.good_lines[#startup.good_lines + 1] = vim.trim(line)
        end
      else
        for _, line in ipairs(startup.mapping_names(options.content)) do
          startup.good_lines[#startup.good_lines + 1] = vim.trim(line)
          table.insert(
            startup.lines,
            { line, options.align, true, options.highlight }
          )
          if settings.options.empty_lines_between_mappings then
            utils.empty(1)
          end
        end
      end
      table.insert(sections_with_mappings, part)
      create_mappings(options.content)
    elseif options.type == "oldfiles" then
      local old_files
      if options.oldfiles_directory then
        old_files = utils.get_oldfiles_directory(options.oldfiles_amount)
      else
        old_files = utils.get_oldfiles(options.oldfiles_amount)
      end
      if options.fold_section then
        section_alignments[vim.trim(options.title)] = options.align
        startup.sections[vim.trim(options.title)] = old_files
        startup.section_highlights[vim.trim(options.title)] = options.highlight
        startup.good_lines[#startup.good_lines + 1] = vim.trim(options.title)
        for _, line in ipairs(old_files) do
          startup.good_lines[#startup.good_lines + 1] = vim.trim(line)
        end
        table.insert(
          startup.lines,
          { options.title, options.align, true, "StartupFoldedSection" }
        )
      else
        for _, line in ipairs(old_files) do
          startup.good_lines[#startup.good_lines + 1] = vim.trim(line)
          table.insert(
            startup.lines,
            { line, options.align, true, options.highlight }
          )
        end
      end
    end
    create_mappings({})
  end
  if settings.folded_section_color ~= "" then
    vim.cmd(
      [[highlight StartupFoldedSection guifg=]]
        .. settings.colors.folded_section
    )
  end
  for _, line in ipairs(startup.lines) do
    table.insert(
      startup.formatted_text,
      startup.align({ line[1] }, line[2])[1]
    )
  end
  set_buf_opt(0, "modifiable", true)
  vim.api.nvim_buf_set_lines(0, 0, -1, true, {})
  vim.api.nvim_buf_set_lines(0, 0, -1, false, startup.formatted_text)
  vim.cmd([[silent! %s/\s\+$//]]) -- clear trailing whitespace
  for linenr, line in ipairs(startup.lines) do
    vim.api.nvim_buf_add_highlight(0, ns, line[4], linenr - 1, 0, -1)
  end
  if settings.options.after and settings.options.after ~= "" then
    settings.options.after()
  end
  set_buf_opt(0, "modifiable", false)
  vim.api.nvim_win_set_cursor(0, { 1, 1 })
  vim.api.nvim_win_set_cursor(0, {
    #settings.header.content + settings.options.paddings[1] + 1,
    math.floor(vim.o.columns / 2),
  })
  vim.cmd(
    [[autocmd CursorMoved * lua require"startup.utils".reposition_cursor()]]
  )
end

---Create autocmds for startup.nvim and update settings with update
---@param update table the settings to use
function startup.setup(update)
  if startup_nvim_loaded then
    return
  end
  startup_nvim_loaded = true
  settings = vim.tbl_deep_extend("force", settings, update or {})
  startup.settings = settings
  vim.cmd("command! Startup :lua require('startup').display()")
  vim.cmd(
    [[autocmd VimEnter * lua if vim.fn.argc() == 0 then require("startup").display() end]],
    [[autocmd BufRead * lua if vim.fn.argc() == 0 then require("startup").display() end]]
  )
  vim.cmd(
    [[autocmd VimResized * lua if vim.bo.ft == "startup" then require"startup".redraw() end]]
  )
end

---Clears the screen and redraws the whole startup screen
function startup.redraw()
  startup.formatted_text = {}
  for _, line in ipairs(startup.lines) do
    table.insert(
      startup.formatted_text,
      startup.align({ line[1] }, line[2])[1]
    )
  end
  set_buf_opt(0, "modifiable", true)
  vim.api.nvim_buf_set_lines(0, 0, -1, true, {})
  vim.api.nvim_buf_set_lines(0, 0, -1, false, startup.formatted_text)
  vim.cmd([[silent! %s/\s\+$//]]) -- clear trailing whitespace
  for linenr, line in ipairs(startup.lines) do
    vim.api.nvim_buf_add_highlight(0, ns, line[4], linenr - 1, 0, -1)
  end
  set_buf_opt(0, "modifiable", false)
end

return startup