stack/apps/api/src/personalities/services/prompt-formatter.service.ts

import { Injectable } from "@nestjs/common";
import { FormalityLevel } from "@prisma/client";
import { Personality } from "../entities/personality.entity";

export interface PromptContext {
  userName?: string;
  workspaceName?: string;
  currentDate?: string;
  currentTime?: string;
  timezone?: string;
  custom?: Record<string, string>;
}

export interface FormattedPrompt {
  systemPrompt: string;
  metadata: {
    personalityId: string;
    personalityName: string;
    tone: string;
    formalityLevel: FormalityLevel;
    formattedAt: Date;
  };
}

const FORMALITY_MODIFIERS: Record<FormalityLevel, string> = {
  VERY_CASUAL:
    "Be extremely relaxed and friendly. Use casual language, contractions, and even emojis when appropriate.",
  CASUAL: "Be friendly and approachable. Use conversational language and a warm tone.",
  NEUTRAL: "Be professional yet approachable. Balance formality with friendliness.",
  FORMAL: "Be professional and respectful. Use proper grammar and formal language.",
  VERY_FORMAL:
    "Be highly professional and formal. Use precise language and maintain a respectful, business-like demeanor.",
};

@Injectable()
export class PromptFormatterService {
  formatPrompt(personality: Personality, context?: PromptContext): FormattedPrompt {
    let prompt = personality.systemPromptTemplate;
    prompt = this.interpolateVariables(prompt, context);

    if (
      !prompt.toLowerCase().includes("formality") &&
      !prompt.toLowerCase().includes(personality.formalityLevel.toLowerCase())
    ) {
      const modifier = FORMALITY_MODIFIERS[personality.formalityLevel];
      prompt = `${prompt}\n\n${modifier}`;
    }

    if (!prompt.toLowerCase().includes(personality.tone.toLowerCase())) {
      prompt = `${prompt}\n\nMaintain a ${personality.tone} tone throughout the conversation.`;
    }

    return {
      systemPrompt: prompt.trim(),
      metadata: {
        personalityId: personality.id,
        personalityName: personality.name,
        tone: personality.tone,
        formalityLevel: personality.formalityLevel,
        formattedAt: new Date(),
      },
    };
  }

  buildSystemPrompt(
    personality: Personality,
    context?: PromptContext,
    options?: { includeDateTime?: boolean; additionalInstructions?: string }
  ): string {
    const { systemPrompt } = this.formatPrompt(personality, context);
    const parts: string[] = [systemPrompt];

    if (options?.includeDateTime === true) {
      const now = new Date();
      const dateStr: string = context?.currentDate ?? now.toISOString().split("T")[0] ?? "";
      const timeStr: string = context?.currentTime ?? now.toTimeString().slice(0, 5);
      const tzStr: string = context?.timezone ?? Intl.DateTimeFormat().resolvedOptions().timeZone;
      parts.push(`Current date: ${dateStr}, Time: ${timeStr} (${tzStr})`);
    }

    if (
      options?.additionalInstructions !== undefined &&
      options.additionalInstructions.length > 0
    ) {
      parts.push(options.additionalInstructions);
    }

    return parts.join("\n\n");
  }

  private interpolateVariables(template: string, context?: PromptContext): string {
    if (context === undefined) {
      return template;
    }

    let result = template;

    if (context.userName !== undefined) {
      result = result.replace(/\{\{userName\}\}/g, context.userName);
    }
    if (context.workspaceName !== undefined) {
      result = result.replace(/\{\{workspaceName\}\}/g, context.workspaceName);
    }
    if (context.currentDate !== undefined) {
      result = result.replace(/\{\{currentDate\}\}/g, context.currentDate);
    }
    if (context.currentTime !== undefined) {
      result = result.replace(/\{\{currentTime\}\}/g, context.currentTime);
    }
    if (context.timezone !== undefined) {
      result = result.replace(/\{\{timezone\}\}/g, context.timezone);
    }

    if (context.custom !== undefined) {
      for (const [key, value] of Object.entries(context.custom)) {
        // Dynamic regex for template replacement - key is from trusted source (our code)
        // eslint-disable-next-line security/detect-non-literal-regexp
        const regex = new RegExp(`\\{\\{${key}\\}\\}`, "g");
        result = result.replace(regex, value);
      }
    }

    return result;
  }

  validateTemplate(template: string): { valid: boolean; missingVariables: string[] } {
    const variablePattern = /\{\{(\w+)\}\}/g;
    const matches = template.matchAll(variablePattern);
    const variables: string[] = [];
    for (const match of matches) {
      const variable = match[1];
      if (variable !== undefined) {
        variables.push(variable);
      }
    }

    const allowedVariables = new Set([
      "userName",
      "workspaceName",
      "currentDate",
      "currentTime",
      "timezone",
    ]);

    const unknownVariables = variables.filter(
      (v) => !allowedVariables.has(v) && !v.startsWith("custom_")
    );

    return {
      valid: unknownVariables.length === 0,
      missingVariables: unknownVariables,
    };
  }

  getFormalityLevels(): { level: FormalityLevel; description: string }[] {
    return Object.entries(FORMALITY_MODIFIERS).map(([level, description]) => ({
      level: level as FormalityLevel,
      description,
    }));
  }
}