local babycode = {}

local string_trim = require("lapis.util").trim
local emoji = require("lib.babycode-emoji")

local Parser = require("lib.babycode-parser")

local function s_split(s, delimiter, max_matches, trim, allow_empty)
  local result = {}
  if s == "" then
    return result
  end
  trim = trim == nil and true or trim
  local tr = function(subj)
    if trim then return string_trim(subj) else return subj end
  end
  max_matches = max_matches or -1
  allow_empty = allow_empty == nil and true or allow_empty
  
  if delimiter == "" then
    for i=1, #s do
      local c = s:sub(i, 1)
      if allow_empty or c ~= "" then
        table.insert(result, c)
        if max_matches > 0 and #result == max_matches then
          break
        end
      end
    end
    return result
  end
  
  local current_pos = 1
  local delim_len = #delimiter
  
  while true do
    if max_matches > 0 and #result >= max_matches then
      break
    end
---@diagnostic disable-next-line: param-type-mismatch
    local start_pos, end_pos = s:find(delimiter, current_pos, true)
    if not start_pos then
      break
    end
    local substr = s:sub(current_pos, start_pos - 1)
    if allow_empty or substr ~= "" then
      table.insert(result, tr(substr))
    end
    current_pos = end_pos + 1
  end
  
  local substr = s:sub(current_pos)
  if allow_empty or substr ~= "" then
    table.insert(result, tr(substr))
  end
  
  return result
end

local function list(tag, children)
  local list_body = children:gsub("  +\n", "<br>"):gsub("\n\n+", "\1")
  local list_items = s_split(list_body, "\1")
  local lis = ""
  for _, li in ipairs(list_items) do
    lis = lis .. "<li>" .. li .. "</li>"
  end
  return "<" .. tag .. ">" .. lis .. "</" .. tag .. ">"
end

local tags = {
  b = "<strong>$S</strong>",
  i = "<em>$S</em>",
  s = "<del>$S</del>",
  img = "<div class=\"post-img-container\"><img class=\"block-img\" src=$A alt=%S></div>",
  url = "<a href=\"$A\">$S</a>",
  quote = "<blockquote>$S</blockquote>",
  code = function(children)
    local is_inline = children:match("\n") == nil
    if is_inline then
      return "<code class=\"inline-code\">" .. children .. "</code>"
    else
      local t = string_trim(children)
      local button = ("<button type=button class=\"copy-code\" value=\"%s\">Copy</button>"):format(t)
      return "<pre><span class=\"copy-code-container\">"..button.."</span><code>"..t.."</code></pre>"
    end
  end,
  ul = function(children)
    return list("ul", children)
  end,
  ol = function(children)
    return list("ol", children)
  end,
}

local text_only = {
  code = true,
}

---renders babycode to html
---@param s string input babycode
---@param html_escape fun(s: string): string function to escape html
function babycode.to_html(s, html_escape)
  -- normalize line ending chars
  local subj = string_trim(html_escape(s)):gsub("\r\n", "\n"):gsub("\r", "\n")
  local parser = Parser.new(subj)
  parser.valid_bbcode_tags = tags
  parser.valid_emotes = emoji
  parser.bbcode_tags_only_text_children = text_only
  
  local elements = parser:parse()
  local out = ""
  local function fold(element, nobr)
    if type(element) == "string" then
      if nobr then
        return element
      end
      return element:gsub("  +\n", "<br>"):gsub("\n\n+", "<br><br>")
    end
    if element.type == "bbcode" then
      local c = ""
      for _, child in ipairs(element.children) do
        local _nobr = element.name == "code" or element.name == "ul" or element.name == "ol"
        c = c .. fold(child, _nobr)
      end
      local res = ""
      if type(tags[element.name]) == "string" then
        res = (tags[element.name]):gsub("%$S", c)
        if element.attribute then
          res = res:gsub("%$A", element.attribute)
        end
        return res
      elseif type(tags[element.name]) == "function" then
        res = tags[element.name](c, element.attribute)
      end
      return res
    elseif element.type == "link" then
      return "<a href=\""..element.url.."\">"..element.url.."</a>"
    elseif element.type == "emote" then
      return emoji[element.name]
    elseif element.type == "ruler" then
      return "<hr>"
    end
  end
  for _, e in ipairs(elements) do
    out = out .. fold(e, false)
  end
  return out
end

return babycode