local config = require('muwiki.config')
local paths = require('muwiki.paths')
local io_module = require('muwiki.io')
local external = require('muwiki.external')

local M = {}

local function get_link_type(target)
  if target:match('^https?://') then
    return 'web'
  end
  if target:match('^file://') then
    return 'file'
  end
  return 'wiki'
end

function M.get_link()
  local cursor = vim.api.nvim_win_get_cursor(0)

  local ok, node = pcall(vim.treesitter.get_node, {
    bufnr = 0,
    pos = { cursor[1] - 1, cursor[2] },
    lang = 'markdown',
    ignore_injections = false,
  })

  if not ok or not node then
    return nil
  end

  local link_node = node ---@type TSNode|nil
  while link_node and link_node:type() ~= 'inline_link' do
    link_node = link_node:parent()
  end

  if not link_node then
    return nil
  end

  local text_node, dest_node
  for child in link_node:iter_children() do
    local t = child:type()
    if t == 'link_text' then
      text_node = child
    elseif t == 'link_destination' then
      dest_node = child
    end
  end

  if not text_node or not dest_node then
    return nil
  end

  local destination = vim.treesitter.get_node_text(dest_node, 0)
  return {
    text = vim.treesitter.get_node_text(text_node, 0),
    target = destination,
    type = get_link_type(destination),
  }
end

local function resolve_file_url(url)
  local path = paths.strip_file_protocol(url)
  local path_type = paths.get_path_type(path)

  if path_type == 'relative' then
    local current_dir = vim.fs.dirname(vim.api.nvim_buf_get_name(0))
    path = vim.fs.joinpath(current_dir, path)
  end

  return 'file://' .. vim.fs.normalize(path)
end

function M.handle_web_link(url)
  if not config.options.use_external_handlers then
    return
  end
  external.open(url)
end

function M.handle_file_url(url)
  if not config.options.use_external_handlers then
    return
  end
  local absolute_url = resolve_file_url(url)
  external.open(absolute_url)
end

function M.handle_file_link(target, wiki_root)
  local ok, file_path = pcall(io_module.resolve, target, wiki_root)
  if not ok then
    vim.notify(string.format('Cannot resolve path: %s', target), vim.log.levels.ERROR)
    return
  end

  if not io_module.file_exists(file_path) then
    vim.notify(string.format('File not found: %s', file_path), vim.log.levels.ERROR)
    return
  end

  local ext = file_path:match('%.([^%.]+)$') or ''
  if not io_module.is_text_file(ext) then
    if not config.options.use_external_handlers then
      return
    end
    external.open(file_path)
    return
  end

  io_module.open_in_buffer(file_path)
end

function M.handle_wiki_link(target, wiki_root)
  local file_path = io_module.resolve(target, wiki_root)
  io_module.open_wiki_file(file_path)
end

local function get_wiki_root_or_notify()
  local wiki_root = config.wiki_root(0)
  if not wiki_root then
    vim.notify('Not in a wiki buffer', vim.log.levels.ERROR)
    return nil
  end
  return wiki_root
end

function M.open_link()
  local link = M.get_link()
  if not link then
    vim.notify('No link found under cursor', vim.log.levels.WARN)
    return
  end

  if link.type == 'web' then
    M.handle_web_link(link.target)
    return
  end

  local wiki_root = get_wiki_root_or_notify()
  if not wiki_root then
    return
  end

  if link.type == 'file' then
    if vim.startswith(link.target, 'file://') then
      M.handle_file_url(link.target)
    else
      M.handle_file_link(link.target, wiki_root)
    end
    return
  end

  M.handle_wiki_link(link.target, wiki_root)
end

function M.open_link_with()
  local link = M.get_link()
  if not link then
    vim.notify('No link found under cursor', vim.log.levels.WARN)
    return
  end

  if link.type == 'wiki' then
    vim.notify('Menu not available for wiki links', vim.log.levels.WARN)
    return
  end

  local url = link.target
  if link.type == 'file' then
    local wiki_root = get_wiki_root_or_notify()
    if not wiki_root then
      return
    end
    url = io_module.resolve(url, wiki_root)
  end

  local matching_handlers = external.get_matching(url)

  if #matching_handlers == 0 then
    vim.notify('No handlers available for this URL', vim.log.levels.WARN)
    return
  end

  if #matching_handlers == 1 then
    external.execute(matching_handlers[1], url)
    return
  end

  local handler_names = {}
  for _, handler in ipairs(matching_handlers) do
    table.insert(handler_names, handler.name)
  end

  vim.ui.select(handler_names, {
    prompt = 'Open with:',
  }, function(choice, idx)
    if choice and idx then
      external.execute(matching_handlers[idx], url)
    end
  end)
end

function M.create_link()
  local mode = vim.fn.mode()
  if mode ~= 'v' and mode ~= 'V' then
    vim.notify('Must be in visual mode to create a link', vim.log.levels.WARN)
    return
  end

  local start_pos = vim.fn.getpos('v')
  local end_pos = vim.fn.getpos('.')
  local region = vim.fn.getregion(start_pos, end_pos, { type = mode })

  if not region or #region == 0 then
    vim.notify('No text selected', vim.log.levels.WARN)
    return
  end

  if #region > 1 then
    vim.notify('Multi-line selection not supported', vim.log.levels.WARN)
    return
  end

  local selected_text = region[1]
  local normalized = io_module.normalize_filename(selected_text)
  local link_target = normalized .. '.md'
  local link_text = string.format('[%s](%s)', selected_text, link_target)

  local start_row = start_pos[2]
  local start_col = start_pos[3]
  local end_row = end_pos[2]
  local end_col = end_pos[3]

  if start_row > end_row or (start_row == end_row and start_col > end_col) then
    start_row, end_row = end_row, start_row
    start_col, end_col = end_col, start_col
  end

  start_row = start_row - 1
  start_col = start_col - 1
  end_row = end_row - 1

  if mode == 'V' then
    start_col = 0
    local line = vim.api.nvim_buf_get_lines(0, end_row, end_row + 1, false)[1]
    end_col = #line
  end

  vim.api.nvim_buf_set_text(0, start_row, start_col, end_row, end_col, { link_text })
  vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes('<Esc>', true, false, true), 'n', false)

  local wiki_root = config.wiki_root(0)
  if not wiki_root then
    vim.notify('Not in a wiki buffer', vim.log.levels.ERROR)
    return
  end

  local target_path = io_module.resolve(link_target, wiki_root)
  io_module.open_wiki_file(target_path)
end

local function jump_link(direction)
  local flags = direction == 'next' and 'w' or 'bw'
  local msg = direction == 'next' and 'No more links' or 'No previous links'

  if vim.fn.search('\\[.\\{-}\\]', flags) == 0 then
    vim.notify(msg, vim.log.levels.INFO)
  end
end

function M.next_link()
  jump_link('next')
end

function M.prev_link()
  jump_link('prev')
end

return M