local _VERSION = '0.1.0';

local DEFAULT_PROMPT = 'reply with exactly: pong';

local function trimTrailingSlash(value)
  return (value:gsub('/+$', ''));
end

local function readAllAndClose(response)
  local body = response.readAll();
  response.close();
  return body;
end

local function statusCode(response)
  if response.getResponseCode then
    return response.getResponseCode();
  end
  return nil;
end

local function mapStatusError(code)
  if code == 401 then return 'token invalide'; end
  if code == 413 then return 'prompt trop long'; end
  if code == 502 then return 'agent indisponible'; end
  if code == 504 then return 'agent trop lent'; end
  if code then return 'erreur proxy: HTTP ' .. tostring(code); end
  return 'erreur proxy inconnue';
end

local function createAiHelloWorld(opts)
  opts = opts or {};

  local httpLib = opts.http or http;
  local settingsLib = opts.settings or settings;
  local prompt = opts.prompt or DEFAULT_PROMPT;

  local api = {};

  function api.version()
    return _VERSION;
  end

  function api.clearSession()
    settingsLib.unset('opencc.session_id');
    if settingsLib.save then settingsLib.save(); end
  end

  function api.askHello(options)
    options = options or {};

    local proxyUrl = options.proxyUrl or settingsLib.get('opencc.proxy_url');
    if not proxyUrl or proxyUrl == '' then
      return false, 'missing opencc.proxy_url; run: settings set opencc.proxy_url <url>';
    end

    local token = options.proxyToken or settingsLib.get('opencc.proxy_token');
    if not token or token == '' then
      return false, 'missing opencc.proxy_token; run: settings set opencc.proxy_token <token>';
    end

    local sessionId = options.sessionId;
    if sessionId == nil then
      sessionId = settingsLib.get('opencc.session_id');
    end

    local body = { prompt = prompt };
    if sessionId and sessionId ~= '' then
      body.sessionId = sessionId;
    end

    local response = httpLib.post(
      trimTrailingSlash(proxyUrl) .. '/ask',
      textutils.serializeJSON(body),
      {
        ['Authorization'] = 'Bearer ' .. token,
        ['Content-Type'] = 'application/json',
      }
    );

    if not response then
      return false, 'proxy injoignable. Verifie opencc.proxy_url et http.rules';
    end

    local code = statusCode(response);
    local responseBody = readAllAndClose(response);
    if code and code ~= 200 then
      return false, mapStatusError(code);
    end

    local decoded = textutils.unserializeJSON(responseBody or '');
    if type(decoded) ~= 'table' then
      return false, 'reponse proxy invalide';
    end
    if type(decoded.reply) ~= 'string' then
      return false, 'reponse proxy sans reply';
    end

    if type(decoded.sessionId) == 'string' and decoded.sessionId ~= '' then
      settingsLib.set('opencc.session_id', decoded.sessionId);
      if settingsLib.save then settingsLib.save(); end
    end

    return true, {
      reply = decoded.reply,
      sessionId = decoded.sessionId,
      truncated = decoded.truncated == true,
    };
  end

  return api;
end

return createAiHelloWorld;