local utils = require('muwiki.utils')
local config = require('muwiki.config')

local M = {}

---@class Link
---@field text string Display text of the link
---@field target string Link destination (URL or path)
---@field type 'web'|'file'|'wiki' Type of link

---@class Handler
---@field name string Display name of the handler
---@field cmd string|function Command or function to handle the URL
---@field exts string[]? Optional list of file extensions this handler supports

local function is_text_extension(ext)
  local text_exts = config.options.text_extensions or {}
  ext = ext:gsub("^%.", "")
  for _, text_ext in ipairs(text_exts) do
    local normalized = text_ext:gsub("^%.", "")
    if normalized == ext then
      return true
    end
  end
  return false
end

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

---Get link information at cursor position
---@return Link|nil link_info Table with text, target, and type, or nil if no link found
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

---Open the link under cursor
---Uses xdg-open for web links and unmatched file:// links
---Opens matching text_extensions in Neovim buffer
---Wiki links always open in Neovim
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
    vim.system({ 'xdg-open', link.target }, { detach = true })
    return
  end

  if link.type == 'file' then
    local file_path = utils.resolve(link.target)
    local ext = file_path:match('%.([^%.]+)$')
    if ext and is_text_extension(ext) then
      utils.open_in_buffer(file_path)
    else
      vim.system({ 'xdg-open', file_path }, { detach = true })
    end
    return
  end

  local file_path = utils.resolve(link.target)
  utils.open_in_buffer(file_path)
end

---Open link with a selectable handler from a menu
---@param handlers Handler[] List of handler tables with name, cmd, and optional exts
---@param link Link? Optional pre-fetched link info, will get from cursor if not provided
function M.open_with_menu(handlers, link)
  link = link or M.get_link()
  if not link then
    vim.notify('No link under cursor', vim.log.levels.WARN)
    return
  end

  local ext = link.target:match('%.([^%.]+)$')
  ext = ext and ext:lower() or nil

  local matching_handlers = {}
  for _, handler in ipairs(handlers) do
    if handler.exts then
      for _, handler_ext in ipairs(handler.exts) do
        if handler_ext:lower() == ext then
          table.insert(matching_handlers, handler)
          break
        end
      end
    else
      table.insert(matching_handlers, handler)
    end
  end

  if #matching_handlers == 0 then
    vim.notify('No handlers for file type: ' .. (ext or 'unknown'), vim.log.levels.WARN)
    return
  end

  local url = link.target
  if link.type == 'file' then
    url = utils.resolve(url)
  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 "' .. link.text .. '" with:',
  }, function(choice, idx)
    if choice and idx then
      local handler = matching_handlers[idx]
      if type(handler.cmd) == 'function' then
        handler.cmd(url)
      else
        vim.system({ handler.cmd, url }, { detach = true })
      end
    end
  end)
end

---Create a link from visual selection
---Converts selected text to [text](normalized_text.md)
---Must be called in visual mode
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 = utils.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 = utils.wiki_root(0)
  if not wiki_root then
    vim.notify('Not in a wiki buffer', vim.log.levels.ERROR)
    return
  end

  local target_path = utils.resolve(link_target)
  utils.open_in_buffer(target_path)
end

---Jump to next or previous markdown link in buffer
---@param direction 'next'|'prev' Direction to search
function M.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

return M