--This class acts as a pipe between the incoming messages and commands.
--It observes the content of the incoming messages, and, depending on the optional flags,
--executes specific commands
--Remember: there can only be one command handler and plugin handler
--per a server handler. Side effects of using multiple command handlers and
--plugin handlers are unknown.
local class = import("classes.baseclass")
local command_handler = class("Command-handler")
local table_utils = import("table-utils")
local purify = import("purify")
function command_handler:__init(parent_server)
  self.server_handler = assert(parent_server,"parent server handler not provided")
  self.command_pool = {}
  self.prefixes = {}
  self.command_meta = {
    plugins = {},
    categories = {}
  }
end
function command_handler:add_prefix(prefix)
  local purified_prefix = purify.purify_escapes(prefix)
  self.prefixes[purified_prefix] = purified_prefix
  return true
end
function command_handler:remove_prefix(prefix)
  local purified_prefix = purify.purify_escapes(prefix)
  if self.prefixes[purified_prefix] or table_utils.count(self.prefixes) <= 1 then
    self.prefix[purified_prefix] = nil
    return true
  else 
    return false, (
        (self.prefixes[purified_prefix] and "No such prefix") or
        "Cannot remove the last remaining prefix"
        )
  end
end
function command_handler:get_prefixes()
  return table_utils.deepcopy(self.prefixes)
end
function command_handler:add_command(command)
  assert(type(command) == "table","command object expected")
  local purified_name = purify.purify_escapes(command.name)
  self.command_pool[purified_name] = command
  if not self.command_meta.plugins[command.parent.name] then
    self.command_meta.plugins[command.parent.name] = {} 
  end
  if not self.command_meta.categories[command.options.category] then
    self.command_meta.categories[command.options.category] = {}
  end
  table.insert(self.command_meta.categories[command.options.category],command.name)
  table.insert(self.command_meta.plugins[command.parent.name],command.name)
  return command
end
function command_handler:remove_command(command)
  assert(type(command) == "table","command object expected")
  local purified_name = purify.purify_escapes(command.name)
  if self.command_pool[purified_name] then
    local command = self.command_pool[purified_name]
    --not exactly optimal, but lists are lists. can't do much about them.
    table_utils.remove_value(self.command_meta.plugins[command.parent.name],command.name)
    if #self.command_meta.plugins[command.parent.name] == 0 then
        self.command_meta.plugins[command.parent.name] = nil
    end
    table_utils.remove_value(self.command_meta.categories[command.options.category],command.name)
    if #self.command_meta.categories[command.options.category] == 0 then
        self.command_meta.categories[command.options.category] = nil
    end
    self.command_pool[purified_name] = nil
    return true
  else 
    return false
  end
end
function command_handler:get_command(name)
  local purified_name = purify.purify_escapes(assert(type(name) == "string") and name)
  if self.command_pool[purified_name] then 
    return self.command_pool[purified_name]
  else
    return false
  end
end
function command_handler:get_commands(name)
  local list = {}
  for k,v in pairs(self.command_pool) do
    table.insert(list,k)
  end
  return list
end
function command_handler:get_commands_metadata()
  return table_utils.deepcopy(self.command_meta)
end
function command_handler:handle(message)
    for name,command in pairs(self.command_pool) do
    if command.options.regex then
      if message.content:match(command.options.regex) then
        command:exec(message)
        return
      end
    else
      if command.options.prefix then
        for _,prefix in pairs(self.prefixes) do
          if message.content:match("^"..prefix..name.."$") or message.content:match("^"..prefix..name.."%s") then
            command:exec(message)
            return
          end
        end
      else
        if message.content:match("^"..name.."$") or message.content:match("^"..name.."%s") then
          command:exec(message)
          return
        end
      end
    end
  end
end
return command_handler