import { EventEmitter } from 'events';

export interface Property {
  id: string;
  description: string;
  predicate: (input: any) => boolean;
  generators: DataGenerator[];
  invariant: string;
  examples: any[];
  counterExamples?: any[];
}

export interface DataGenerator {
  type: string;
  constraints: any;
  generate: () => any;
}

export interface ValidationResult {
  valid: boolean;
  violations: PropertyViolation[];
  coverage: number;
  confidence: number;
  recommendations: string[];
}

export interface PropertyViolation {
  property: string;
  input: any;
  expected: any;
  actual: any;
  severity: 'low' | 'medium' | 'high' | 'critical';
}

export interface CodeSpecification {
  function: string;
  parameters: Parameter[];
  returnType: string;
  preconditions: string[];
  postconditions: string[];
  invariants: string[];
  examples: TestCase[];
}

export interface Parameter {
  name: string;
  type: string;
  constraints: any[];
}

export interface TestCase {
  input: any;
  output: any;
  description: string;
}

/**
 * Property-Based Testing Engine for FlowX
 * Generates semantic properties and validates code against invariants
 */
export class PropertyTestingEngine extends EventEmitter {
  private hypothesisGenerator: HypothesisGenerator;
  private propertyValidator: PropertyValidator;
  private invariantChecker: InvariantChecker;
  private dataGenerators: Map<string, DataGenerator>;

  constructor() {
    super();
    this.hypothesisGenerator = new HypothesisGenerator();
    this.propertyValidator = new PropertyValidator();
    this.invariantChecker = new InvariantChecker();
    this.dataGenerators = new Map();
    this.initializeBuiltInGenerators();
  }

  /**
   * Generate properties from code specification
   */
  async generateProperties(code: string, spec: CodeSpecification): Promise<Property[]> {
    try {
      this.emit('generation:start', { code, spec });

      // Generate semantic properties from specification
      const semanticProperties = await this.hypothesisGenerator.generateFromSpec(spec);
      
      // Extract invariants from code analysis
      const codeInvariants = await this.extractInvariantsFromCode(code);
      
      // Generate edge case properties
      const edgeCaseProperties = await this.generateEdgeCaseProperties(spec);
      
      // Combine all properties
      const allProperties = [
        ...semanticProperties,
        ...codeInvariants,
        ...edgeCaseProperties
      ];

      // Validate and filter properties
      const validatedProperties = await this.validateProperties(allProperties, code);

      this.emit('generation:complete', { 
        properties: validatedProperties.length,
        coverage: this.calculateCoverage(validatedProperties, spec)
      });

      return validatedProperties;
    } catch (error) {
      this.emit('generation:error', error);
      throw new Error(`Property generation failed: ${error instanceof Error ? error.message : String(error)}`);
    }
  }

  /**
   * Validate invariants in code
   */
  async validateInvariants(code: string): Promise<ValidationResult> {
    try {
      this.emit('validation:start', { code });

      const violations: PropertyViolation[] = [];
      const properties = await this.extractPropertiesFromCode(code);

      for (const property of properties) {
        const result = await this.invariantChecker.validate(property, code);
        if (!result.valid) {
          violations.push(...result.violations);
        }
      }

      const validationResult: ValidationResult = {
        valid: violations.length === 0,
        violations,
        coverage: this.calculatePropertyCoverage(properties),
        confidence: this.calculateConfidence(violations, properties),
        recommendations: this.generateRecommendations(violations)
      };

      this.emit('validation:complete', validationResult);
      return validationResult;

    } catch (error) {
      this.emit('validation:error', error);
      throw new Error(`Invariant validation failed: ${error instanceof Error ? error.message : String(error)}`);
    }
  }

  /**
   * Run property-based tests with generated data
   */
  async runPropertyTests(
    properties: Property[], 
    code: string, 
    iterations: number = 1000
  ): Promise<ValidationResult> {
    const violations: PropertyViolation[] = [];
    let totalTests = 0;

    for (const property of properties) {
      for (let i = 0; i < iterations; i++) {
        totalTests++;
        
        // Generate test data
        const testData = this.generateTestData(property.generators);
        
        // Execute code with test data
        const result = await this.executeCode(code, testData);
        
        // Check property
        if (!property.predicate(result)) {
          violations.push({
            property: property.id,
            input: testData,
            expected: property.description,
            actual: result,
            severity: this.assessSeverity(property, result)
          });
        }
      }
    }

    return {
      valid: violations.length === 0,
      violations,
      coverage: (totalTests - violations.length) / totalTests,
      confidence: Math.max(0, 1 - violations.length / totalTests),
      recommendations: this.generateRecommendations(violations)
    };
  }

  /**
   * Generate edge case properties
   */
  private async generateEdgeCaseProperties(spec: CodeSpecification): Promise<Property[]> {
    const edgeCaseProperties: Property[] = [];

    // Null/undefined checks
    edgeCaseProperties.push({
      id: 'null-safety',
      description: 'Function should handle null/undefined inputs gracefully',
      predicate: (result) => result !== undefined && !this.causesError(result),
      generators: [this.createNullGenerator()],
      invariant: 'No null pointer exceptions',
      examples: [null, undefined]
    });

    // Boundary value checks
    if (spec.parameters.some(p => p.type === 'number')) {
      edgeCaseProperties.push({
        id: 'boundary-values',
        description: 'Function should handle boundary values correctly',
        predicate: (result) => this.isValidBoundaryResult(result),
        generators: [this.createBoundaryValueGenerator()],
        invariant: 'Boundary values produce valid results',
        examples: [Number.MAX_SAFE_INTEGER, Number.MIN_SAFE_INTEGER, 0, -1, 1]
      });
    }

    // String edge cases
    if (spec.parameters.some(p => p.type === 'string')) {
      edgeCaseProperties.push({
        id: 'string-edge-cases',
        description: 'Function should handle string edge cases',
        predicate: (result) => this.isValidStringResult(result),
        generators: [this.createStringEdgeCaseGenerator()],
        invariant: 'String edge cases handled properly',
        examples: ['', ' ', '\n', '\t', '🚀', 'very'.repeat(1000)]
      });
    }

    return edgeCaseProperties;
  }

  /**
   * Initialize built-in data generators
   */
  private initializeBuiltInGenerators(): void {
    // Integer generator
    this.dataGenerators.set('integer', {
      type: 'integer',
      constraints: { min: -1000, max: 1000 },
      generate: () => Math.floor(Math.random() * 2000) - 1000
    });

    // String generator
    this.dataGenerators.set('string', {
      type: 'string',
      constraints: { maxLength: 100 },
      generate: () => this.generateRandomString(Math.floor(Math.random() * 100))
    });

    // Array generator
    this.dataGenerators.set('array', {
      type: 'array',
      constraints: { maxSize: 50 },
      generate: () => Array.from(
        { length: Math.floor(Math.random() * 50) }, 
        () => Math.random()
      )
    });

    // Boolean generator
    this.dataGenerators.set('boolean', {
      type: 'boolean',
      constraints: {},
      generate: () => Math.random() > 0.5
    });
  }

  /**
   * Extract properties from code analysis
   */
  private async extractPropertiesFromCode(code: string): Promise<Property[]> {
    // This would use AST analysis to find implicit properties
    // For now, return basic properties
    return [
      {
        id: 'no-errors',
        description: 'Code should not throw unexpected errors',
        predicate: (result) => !this.causesError(result),
        generators: [this.dataGenerators.get('string')!],
        invariant: 'No runtime errors',
        examples: []
      }
    ];
  }

  /**
   * Generate test data using property generators
   */
  private generateTestData(generators: DataGenerator[]): any {
    if (generators.length === 1) {
      return generators[0].generate();
    }
    return generators.map(gen => gen.generate());
  }

  /**
   * Execute code with test data (mock implementation)
   */
  private async executeCode(code: string, testData: any): Promise<any> {
    // In a real implementation, this would safely execute the code
    // with the test data in a sandboxed environment
    try {
      // Mock execution result
      return { success: true, data: testData };
    } catch (error) {
      return { success: false, error: error instanceof Error ? error.message : String(error) };
    }
  }

  /**
   * Assess severity of property violation
   */
  private assessSeverity(property: Property, result: any): 'low' | 'medium' | 'high' | 'critical' {
    if (property.id.includes('security') || property.id.includes('null-safety')) {
      return 'critical';
    }
    if (property.id.includes('boundary') || property.id.includes('edge')) {
      return 'high';
    }
    if (this.causesError(result)) {
      return 'high';
    }
    return 'medium';
  }

  /**
   * Generate recommendations based on violations
   */
  private generateRecommendations(violations: PropertyViolation[]): string[] {
    const recommendations: string[] = [];
    
    for (const violation of violations) {
      switch (violation.severity) {
        case 'critical':
          recommendations.push(`CRITICAL: Fix ${violation.property} - this could cause security issues or crashes`);
          break;
        case 'high':
          recommendations.push(`HIGH: Address ${violation.property} - likely to cause production issues`);
          break;
        case 'medium':
          recommendations.push(`MEDIUM: Consider fixing ${violation.property} for better robustness`);
          break;
        default:
          recommendations.push(`LOW: ${violation.property} could be improved`);
      }
    }

    return recommendations;
  }

  /**
   * Utility methods
   */
  private causesError(result: any): boolean {
    return result && result.error !== undefined;
  }

  private isValidBoundaryResult(result: any): boolean {
    return result !== null && result !== undefined && !this.causesError(result);
  }

  private isValidStringResult(result: any): boolean {
    return typeof result === 'string' || (result && !this.causesError(result));
  }

  private generateRandomString(length: number): string {
    const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    return Array.from({ length }, () => chars[Math.floor(Math.random() * chars.length)]).join('');
  }

  private calculateCoverage(properties: Property[], spec: CodeSpecification): number {
    // Calculate how well properties cover the specification
    const totalConcerns = spec.preconditions.length + spec.postconditions.length + spec.invariants.length;
    const coveredConcerns = properties.length;
    return totalConcerns > 0 ? Math.min(1, coveredConcerns / totalConcerns) : 1;
  }

  private calculatePropertyCoverage(properties: Property[]): number {
    // Basic coverage calculation
    return properties.length > 0 ? 0.8 : 0;
  }

  private calculateConfidence(violations: PropertyViolation[], properties: Property[]): number {
    if (properties.length === 0) return 0;
    const criticalViolations = violations.filter(v => v.severity === 'critical').length;
    const highViolations = violations.filter(v => v.severity === 'high').length;
    
    // Reduce confidence based on severity
    const penaltyFactor = (criticalViolations * 0.4) + (highViolations * 0.2) + (violations.length * 0.1);
    return Math.max(0, 1 - penaltyFactor / properties.length);
  }

  private async validateProperties(properties: Property[], code: string): Promise<Property[]> {
    // Filter out invalid or redundant properties
    return properties.filter(property => 
      typeof property.predicate === 'function' && 
      property.generators && 
      property.generators.length > 0
    );
  }

  private async extractInvariantsFromCode(code: string): Promise<Property[]> {
    // This would analyze the code to extract implicit invariants
    return [];
  }

  private createNullGenerator(): DataGenerator {
    return {
      type: 'null',
      constraints: {},
      generate: () => Math.random() > 0.5 ? null : undefined
    };
  }

  private createBoundaryValueGenerator(): DataGenerator {
    return {
      type: 'boundary',
      constraints: {},
      generate: () => {
        const values = [0, 1, -1, Number.MAX_SAFE_INTEGER, Number.MIN_SAFE_INTEGER];
        return values[Math.floor(Math.random() * values.length)];
      }
    };
  }

  private createStringEdgeCaseGenerator(): DataGenerator {
    return {
      type: 'string-edge',
      constraints: {},
      generate: () => {
        const edgeCases = ['', ' ', '\n', '\t', '🚀', 'very'.repeat(1000)];
        return edgeCases[Math.floor(Math.random() * edgeCases.length)];
      }
    };
  }
}

/**
 * Hypothesis Generator - Creates properties from specifications
 */
export class HypothesisGenerator {
  async generateFromSpec(spec: CodeSpecification): Promise<Property[]> {
    const properties: Property[] = [];

    // Generate properties from preconditions
    for (const precondition of spec.preconditions) {
      properties.push({
        id: `precondition-${precondition.replace(/\s+/g, '-')}`,
        description: `Precondition: ${precondition}`,
        predicate: () => true, // Would be derived from precondition
        generators: this.createGeneratorsForPrecondition(precondition),
        invariant: precondition,
        examples: []
      });
    }

    // Generate properties from postconditions
    for (const postcondition of spec.postconditions) {
      properties.push({
        id: `postcondition-${postcondition.replace(/\s+/g, '-')}`,
        description: `Postcondition: ${postcondition}`,
        predicate: () => true, // Would be derived from postcondition
        generators: this.createGeneratorsForPostcondition(postcondition),
        invariant: postcondition,
        examples: []
      });
    }

    return properties;
  }

  private createGeneratorsForPrecondition(precondition: string): DataGenerator[] {
    // Create appropriate generators based on precondition analysis
    return [{
      type: 'generic',
      constraints: {},
      generate: () => Math.random()
    }];
  }

  private createGeneratorsForPostcondition(postcondition: string): DataGenerator[] {
    // Create appropriate generators based on postcondition analysis
    return [{
      type: 'generic',
      constraints: {},
      generate: () => Math.random()
    }];
  }
}

/**
 * Property Validator - Validates properties against code
 */
export class PropertyValidator {
  async validate(property: Property, code: string): Promise<ValidationResult> {
    // Implement property validation logic
    return {
      valid: true,
      violations: [],
      coverage: 1,
      confidence: 1,
      recommendations: []
    };
  }
}

/**
 * Invariant Checker - Validates code invariants
 */
export class InvariantChecker {
  async validate(property: Property, code: string): Promise<ValidationResult> {
    // Implement invariant checking logic
    return {
      valid: true,
      violations: [],
      coverage: 1,
      confidence: 1,
      recommendations: []
    };
  }
}