Simple prompt generator for LLAMA2. Input OpenAI style prompts and get LLAMA 2 prompts.

llama2-prompt-template.ts

type Role = 'system' | 'user' | 'assistant';

interface Message {
  role: Role;
  content: string;
}

type Messages = Array<Message>;

const B_INST = '[INST]';
const E_INST = '[/INST]';
const DEFAULT_SYSTEM_PROMPT = `You are a helpful, respectful and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature.
If a question does not make any sense, or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.`;

function prepareDialog(dialog: Messages): string {
  if (dialog[0].role !== 'system') {
    dialog.unshift({
      role: 'system',
      content: DEFAULT_SYSTEM_PROMPT,
    });
  }

  let dialogTokens: Array<string> = [];

  for (let i = 0; i < dialog.length; i += 2) {
    const prompt = dialog[i];
    const answer = dialog[i + 1];
    if (prompt && answer) {
      dialogTokens.push(
        `${B_INST} ${prompt.content.trim()} ${E_INST} ${answer.content.trim()} `
      );
    }
  }

  // Last message must be from user
  if (dialog[dialog.length - 1].role !== 'user') {
    throw new Error('Last message must be from user');
  }
  dialogTokens.push(
    `${B_INST} ${dialog[dialog.length - 1].content.trim()} ${E_INST}`
  );

  return dialogTokens.join('');
}

const testMessages: Messages = [
  {
    role: 'system',
    content: 'Pretend to be a sarcastic robot.',
  },
  {
    role: 'user',
    content: 'What is the meaning of life?',
  },
  {
    role: 'assistant',
    content: 'Nobody tells me nothing.',
  },
  {
    role: 'user',
    content: 'But what is it though?',
  },
];

console.log('Input - ', testMessages);
console.log('-----------------');
console.log('Output: ', prepareDialog(testMessages));