LLM Prompt Management — Versioning, Testing, and Deploying Prompts Like Code

import fs from 'fs';
import path from 'path';

interface PromptVersion {
  id: string;
  name: string;
  version: string;
  created_at: Date;
  created_by: string;
  content: string;
  variables: string[];
  model: string;
  temperature: number;
  max_tokens: number;
  tags: string[];
  description: string;
}

class PromptRegistry {
  private promptsDir = './prompts';
  private promptsDb: Map<string, PromptVersion[]> = new Map();

  constructor() {
    this.loadPromptsFromDisk();
  }

  private loadPromptsFromDisk(): void {
    if (!fs.existsSync(this.promptsDir)) {
      fs.mkdirSync(this.promptsDir, { recursive: true });
      return;
    }

    const files = fs.readdirSync(this.promptsDir);

    for (const file of files) {
      if (!file.endsWith('.json')) continue;

      const filePath = path.join(this.promptsDir, file);
      const content = fs.readFileSync(filePath, 'utf-8');
      const data = JSON.parse(content);

      const name = file.replace('.json', '');
      this.promptsDb.set(name, data.versions || []);
    }
  }

  async savePrompt(prompt: PromptVersion): Promise<void> {
    const versions = this.promptsDb.get(prompt.name) || [];
    versions.push(prompt);
    this.promptsDb.set(prompt.name, versions);

    const filePath = path.join(this.promptsDir, `${prompt.name}.json`);
    fs.writeFileSync(
      filePath,
      JSON.stringify(
        {
          name: prompt.name,
          versions,
          latest: prompt.version
        },
        null,
        2
      )
    );
  }

  getPrompt(name: string, version?: string): PromptVersion | null {
    const versions = this.promptsDb.get(name);
    if (!versions || versions.length === 0) return null;

    if (!version) {
      // Return latest
      return versions[versions.length - 1];
    }

    return versions.find(v => v.version === version) || null;
  }

  getAllVersions(name: string): PromptVersion[] {
    return this.promptsDb.get(name) || [];
  }

  renderPrompt(prompt: PromptVersion, variables: Record<string, string>): string {
    let rendered = prompt.content;

    for (const [key, value] of Object.entries(variables)) {
      rendered = rendered.replace(new RegExp(`\\$\\{${key}\\}`, 'g'), value);
    }

    return rendered;
  }
}

class PromptVersionManager {
  private registry = new PromptRegistry();

  parseVersion(version: string): { major: number; minor: number; patch: number } {
    const [major, minor, patch] = version.split('.').map(Number);
    return { major, minor, patch };
  }

  formatVersion(major: number, minor: number, patch: number): string {
    return `${major}.${minor}.${patch}`;
  }

  nextPatch(currentVersion: string): string {
    const parsed = this.parseVersion(currentVersion);
    return this.formatVersion(parsed.major, parsed.minor, parsed.patch + 1);
  }

  nextMinor(currentVersion: string): string {
    const parsed = this.parseVersion(currentVersion);
    return this.formatVersion(parsed.major, parsed.minor + 1, 0);
  }

  nextMajor(currentVersion: string): string {
    const parsed = this.parseVersion(currentVersion);
    return this.formatVersion(parsed.major + 1, 0, 0);
  }

  // When to bump versions
  getVersionBump(oldPrompt: string, newPrompt: string): 'patch' | 'minor' | 'major' {
    // Major: changes output format or removes variables
    if (!/\$\{(\w+)\}/.test(oldPrompt) && /\$\{(\w+)\}/.test(newPrompt)) {
      return 'major';
    }

    // Minor: new optional instruction or output behavior change
    if (newPrompt.length > oldPrompt.length * 1.2) {
      return 'minor';
    }

    // Patch: typo fix, small wording improvement
    return 'patch';
  }

  comparePrompts(v1: PromptVersion, v2: PromptVersion): {
    breaking_changes: boolean;
    behavioral_changes: boolean;
    diff_size: number;
  } {
    const oldTokens = v1.content.split(/\s+/).length;
    const newTokens = v2.content.split(/\s+/).length;
    const diffSize = Math.abs(newTokens - oldTokens);

    return {
      breaking_changes: v1.model !== v2.model || v1.max_tokens !== v2.max_tokens,
      behavioral_changes: diffSize > oldTokens * 0.1, // >10% change
      diff_size: diffSize
    };
  }
}

interface ABTestConfig {
  name: string;
  prompt_a: PromptVersion;
  prompt_b: PromptVersion;
  split_percent: number; // 0-100, percent to version B
  start_date: Date;
  end_date: Date;
  metric: 'latency' | 'cost' | 'quality';
}

interface ABTestResult {
  request_id: string;
  variant: 'a' | 'b';
  metric_value: number;
  timestamp: Date;
}

class ABTestRunner {
  private activeTests: Map<string, ABTestConfig> = new Map();
  private results: ABTestResult[] = [];

  startTest(config: ABTestConfig): void {
    this.activeTests.set(config.name, config);
  }

  selectVariant(testName: string, userId: string): 'a' | 'b' {
    const test = this.activeTests.get(testName);
    if (!test) return 'a';

    // Hash user ID to determine assignment (consistent)
    const hash = parseInt(
      Array.from(userId).reduce((acc, char) => acc + char.charCodeAt(0), '').toString().slice(0, 10)
    );

    const threshold = (test.split_percent / 100) * Number.MAX_SAFE_INTEGER;
    return hash % Number.MAX_SAFE_INTEGER < threshold ? 'b' : 'a';
  }

  recordResult(testName: string, result: ABTestResult): void {
    this.results.push(result);
  }

  getResults(testName: string): ABTestResult[] {
    return this.results.filter(r => {
      const test = this.activeTests.get(testName);
      return test &&
        r.timestamp >= test.start_date &&
        r.timestamp <= test.end_date;
    });
  }

  analyzeTest(testName: string): {
    variant_a: { mean: number; count: number };
    variant_b: { mean: number; count: number };
    winner: 'a' | 'b' | null;
  } {
    const results = this.getResults(testName);

    const aResults = results.filter(r => r.variant === 'a');
    const bResults = results.filter(r => r.variant === 'b');

    const aMean = aResults.length > 0
      ? aResults.reduce((sum, r) => sum + r.metric_value, 0) / aResults.length
      : 0;

    const bMean = bResults.length > 0
      ? bResults.reduce((sum, r) => sum + r.metric_value, 0) / bResults.length
      : 0;

    // Need minimum sample size
    const minSamples = 100;
    let winner: 'a' | 'b' | null = null;

    if (aResults.length > minSamples && bResults.length > minSamples) {
      winner = aMean > bMean ? 'a' : 'b';
    }

    return {
      variant_a: { mean: aMean, count: aResults.length },
      variant_b: { mean: bMean, count: bResults.length },
      winner
    };
  }
}

interface GoldenExample {
  id: string;
  input: Record<string, string>;
  expected_output: string;
  category: string;
}

interface RegressionTest {
  prompt_version: string;
  examples: GoldenExample[];
  passed: number;
  failed: number;
  error_rate: number;
}

class RegressionTestRunner {
  private goldenDataset: GoldenExample[] = [];
  private similarityThreshold = 0.85;

  loadGoldenDataset(filePath: string): void {
    const content = fs.readFileSync(filePath, 'utf-8');
    this.goldenDataset = JSON.parse(content);
  }

  async runRegressionTest(
    promptVersion: PromptVersion,
    client: any
  ): Promise<RegressionTest> {
    let passed = 0;
    let failed = 0;
    const registry = new PromptRegistry();

    for (const example of this.goldenDataset) {
      const renderedPrompt = registry.renderPrompt(promptVersion, example.input);

      try {
        const response = await client.chat.completions.create({
          model: promptVersion.model,
          messages: [{ role: 'user', content: renderedPrompt }],
          temperature: promptVersion.temperature,
          max_tokens: promptVersion.max_tokens
        });

        const output = response.choices[0].message.content;
        const similarity = this.calculateSimilarity(output, example.expected_output);

        if (similarity >= this.similarityThreshold) {
          passed++;
        } else {
          failed++;
          console.warn(`Regression test failed for example ${example.id}`);
          console.warn(`Expected: ${example.expected_output}`);
          console.warn(`Got: ${output}`);
        }
      } catch (error) {
        failed++;
        console.error(`Error testing example ${example.id}: ${error}`);
      }
    }

    return {
      prompt_version: promptVersion.version,
      examples: this.goldenDataset,
      passed,
      failed,
      error_rate: failed / this.goldenDataset.length
    };
  }

  private calculateSimilarity(a: string, b: string): number {
    // Simple overlap-based similarity (in production, use embeddings)
    const aWords = new Set(a.toLowerCase().split(/\s+/));
    const bWords = new Set(b.toLowerCase().split(/\s+/));

    const intersection = [...aWords].filter(w => bWords.has(w)).length;
    const union = new Set([...aWords, ...bWords]).size;

    return union > 0 ? intersection / union : 0;
  }

  passedAllTests(test: RegressionTest): boolean {
    return test.failed === 0;
  }

  passedPercentage(test: RegressionTest): number {
    return (test.passed / (test.passed + test.failed)) * 100;
  }
}

interface TemplateContext {
  [key: string]: string | number | boolean | string[];
}

class PromptTemplateEngine {
  render(template: string, context: TemplateContext): string {
    let result = template;

    // Handle simple variable substitution: ${varName}
    result = result.replace(/\$\{(\w+)\}/g, (match, varName) => {
      const value = context[varName];
      if (value === undefined) throw new Error(`Missing variable: ${varName}`);
      return String(value);
    });

    // Handle conditionals: {{#if condition}}...{{/if}}
    result = result.replace(
      /\{\{#if\s+(\w+)\}\}([\s\S]*?)\{\{\/if\}\}/g,
      (match, condition, content) => {
        return context[condition] ? content : '';
      }
    );

    // Handle loops: {{#each items}}...{{/each}}
    result = result.replace(
      /\{\{#each\s+(\w+)\}\}([\s\S]*?)\{\{\/each\}\}/g,
      (match, varName, content) => {
        const items = context[varName];
        if (!Array.isArray(items)) return '';

        return items
          .map((item, index) =>
            content
              .replace(/\{\{this\}\}/g, String(item))
              .replace(/\{\{@index\}\}/g, String(index))
          )
          .join('');
      }
    );

    return result;
  }

  validate(template: string): { valid: boolean; errors: string[] } {
    const errors: string[] = [];

    // Find undefined variables
    const varMatches = template.match(/\$\{(\w+)\}/g) || [];
    const definedVars = new Set(varMatches.map(m => m.slice(2, -1)));

    // Check for mismatched conditionals
    const ifCount = (template.match(/\{\{#if/g) || []).length;
    const ifEndCount = (template.match(/\{\{\/if\}\}/g) || []).length;

    if (ifCount !== ifEndCount) {
      errors.push(`Mismatched if/endif: ${ifCount} if, ${ifEndCount} endif`);
    }

    return {
      valid: errors.length === 0,
      errors
    };
  }
}

class PromptInjectionPreventionManager {
  private dangerousPatterns = [
    /ignore previous instructions/i,
    /forget the system prompt/i,
    /forget all previous/i,
    /jailbreak/i,
    /bypass security/i,
    /admin override/i
  ];

  isSuspicious(text: string): boolean {
    for (const pattern of this.dangerousPatterns) {
      if (pattern.test(text)) {
        return true;
      }
    }

    // Check for unusual quote patterns that might break prompts
    const quoteCount = (text.match(/"|"|''|``/g) || []).length;
    if (quoteCount > 10) {
      return true;
    }

    return false;
  }

  sanitize(text: string): string {
    // Escape special characters
    return text
      .replace(/</g, '<')
      .replace(/>/g, '>')
      .replace(/"/g, '"')
      .replace(/'/g, ''');
  }

  buildSafePrompt(
    template: string,
    userInput: string,
    variableName: string = 'user_input'
  ): string {
    if (this.isSuspicious(userInput)) {
      console.warn(`Suspicious input detected: ${userInput.substring(0, 50)}`);
    }

    const sanitized = this.sanitize(userInput);

    // Wrap in quotes and comment marker for clarity
    const safeInput = `"${sanitized}"`;

    return template.replace(`$\{${variableName}\}`, safeInput);
  }
}

type Environment = 'development' | 'staging' | 'production';

interface PromptEnvironment {
  environment: Environment;
  version: string;
  promoted_at: Date;
  promoted_by: string;
}

class PromptPromotionPipeline {
  private promotionHistory: PromptEnvironment[] = [];
  private redis: any; // Redis client

  async promoteToEnvironment(
    promptName: string,
    version: string,
    targetEnv: Environment,
    promotedBy: string
  ): Promise<void> {
    const key = `prompt:${promptName}:${targetEnv}`;

    await this.redis.set(key, version);
    this.promotionHistory.push({
      environment: targetEnv,
      version,
      promoted_at: new Date(),
      promoted_by: promotedBy
    });
  }

  async getActivePrompt(promptName: string, env: Environment): Promise<string | null> {
    const key = `prompt:${promptName}:${env}`;
    return await this.redis.get(key);
  }

  async validateBeforePromotion(
    promptName: string,
    version: string,
    targetEnv: Environment
  ): Promise<{ valid: boolean; errors: string[] }> {
    const errors: string[] = [];

    // Can't skip environments
    if (targetEnv === 'production') {
      const stagingVersion = await this.getActivePrompt(promptName, 'staging');
      if (stagingVersion !== version) {
        errors.push('Must be validated in staging first');
      }
    }

    // Must pass regression tests
    // (would call RegressionTestRunner here)

    return {
      valid: errors.length === 0,
      errors
    };
  }

  async rollback(promptName: string, env: Environment): Promise<string | null> {
    const history = this.promotionHistory.filter(
      p => p.environment === env
    ).sort((a, b) => b.promoted_at.getTime() - a.promoted_at.getTime());

    if (history.length < 2) return null; // Not enough history

    const previousVersion = history[1].version;
    await this.promoteToEnvironment(promptName, previousVersion, env, 'system');

    return previousVersion;
  }

  getPromotionHistory(promptName?: string): PromptEnvironment[] {
    if (!promptName) return this.promotionHistory;

    return this.promotionHistory.filter(
      p => p.promoted_by.includes(promptName)
    );
  }
}

interface QualityMetric {
  regression_test_pass_rate: number;
  average_latency_ms: number;
  cost_per_request: number;
  user_satisfaction_score: number;
}

class QualityMonitor {
  private baselineMetrics: Map<string, QualityMetric> = new Map();
  private degradationThreshold = 0.05; // 5% degradation

  recordBaseline(promptVersion: string, metrics: QualityMetric): void {
    this.baselineMetrics.set(promptVersion, metrics);
  }

  detectDegradation(
    promptVersion: string,
    currentMetrics: QualityMetric
  ): { degraded: boolean; reasons: string[] } {
    const baseline = this.baselineMetrics.get(promptVersion);
    if (!baseline) {
      return { degraded: false, reasons: [] };
    }

    const reasons: string[] = [];

    // Check each metric
    const passRateDrop = 1 - (currentMetrics.regression_test_pass_rate / baseline.regression_test_pass_rate);
    if (passRateDrop > this.degradationThreshold) {
      reasons.push(`Regression test pass rate dropped ${(passRateDrop * 100).toFixed(1)}%`);
    }

    const satisfactionDrop = 1 - (currentMetrics.user_satisfaction_score / baseline.user_satisfaction_score);
    if (satisfactionDrop > this.degradationThreshold) {
      reasons.push(`User satisfaction dropped ${(satisfactionDrop * 100).toFixed(1)}%`);
    }

    const latencyIncrease = (currentMetrics.average_latency_ms / baseline.average_latency_ms) - 1;
    if (latencyIncrease > 0.2) {
      reasons.push(`Latency increased ${(latencyIncrease * 100).toFixed(1)}%`);
    }

    return {
      degraded: reasons.length > 0,
      reasons
    };
  }

  async triggerRollbackIfNeeded(
    promptName: string,
    env: Environment,
    metrics: QualityMetric,
    pipeline: PromptPromotionPipeline
  ): Promise<boolean> {
    const currentVersion = await pipeline.getActivePrompt(promptName, env);
    if (!currentVersion) return false;

    const degradation = this.detectDegradation(currentVersion, metrics);

    if (degradation.degraded) {
      console.error(`Quality degradation detected: ${degradation.reasons.join('; ')}`);

      const previous = await pipeline.rollback(promptName, env);
      if (previous) {
        console.log(`Rolled back to ${previous}`);
        return true;
      }
    }

    return false;
  }
}