// src/core/engine.js - Main Baba Yaga engine (optimized by default)

import { BabaYagaConfig } from './config.js';
import { InputValidator, SecurityValidator } from './validation.js';
import { BabaError } from './error.js';
import { createLexer, createOptimizedLexer, createLexerWithFallback } from './lexer.js';
import { createParser } from './parser.js';
import { createInterpreter } from './interpreter.js';
import { ScopeStack, CompatibleScopeStack } from './scope-stack.js';
import { OptimizedBuiltins } from './builtins.js';
import { globalASTPool } from './ast-pool.js';

/**
 * Main Baba Yaga engine with optimizations enabled by default
 * This is the primary engine that should be used for all new code
 */
export class BabaYagaEngine {
  constructor(config = new BabaYagaConfig()) {
    this.config = config;
    this.validator = config.sandboxMode 
      ? new SecurityValidator(config) 
      : new InputValidator(config);
    
    // Initialize optimization components (enabled by default)
    this.optimizedBuiltins = new OptimizedBuiltins();
    this.astPool = globalASTPool;
    
    // Performance tracking
    this.stats = {
      totalExecutions: 0,
      totalTime: 0,
      averageTime: 0,
      errors: 0,
      lexingTime: 0,
      parsingTime: 0,
      interpretingTime: 0,
      optimizationStats: {
        lexerOptimizations: 0,
        scopeOptimizations: 0,
        builtinOptimizations: 0,
        astPoolHits: 0
      }
    };

    // Warm up optimization components if enabled
    if (config.enableOptimizations) {
      this.warmUp();
    }
  }

  /**
   * Warm up optimization components for better initial performance
   */
  warmUp() {
    // Warm up AST pools
    this.astPool.warmUp('BinaryExpression', 50);
    this.astPool.warmUp('FunctionCall', 30);
    this.astPool.warmUp('Identifier', 100);
    this.astPool.warmUp('NumberLiteral', 50);
    
    // Warm up with a simple program
    const warmupCode = 'x : 1 + 2; y : x * 3;';
    try {
      this.executeSync(warmupCode, { silent: true });
    } catch (error) {
      // Ignore warmup errors
    }
  }

  /**
   * Execute Baba Yaga source code
   */
  async execute(source, options = {}) {
    const startTime = performance.now();
    
    try {
      // Validate input
      this.validator.validateSourceCode(source, options.filename || '<input>');
      
      // Lexical analysis (use legacy lexer by default due to critical bug in optimized version)
      const lexStart = performance.now();
      const lexer = this.config.enableOptimizations 
        ? await createLexerWithFallback(source, true)  // Try optimized with fallback
        : await createLexerWithFallback(source, false); // Use legacy directly
      const tokens = lexer.allTokens();
      const lexTime = performance.now() - lexStart;
      
      if (this.config.enableDebugMode) {
        console.log(`[DEBUG] Lexing: ${lexTime.toFixed(2)}ms, Tokens: ${tokens.length}`);
      }
      
      // Parsing with AST pooling
      const parseStart = performance.now();
      const parser = this.createOptimizedParser(tokens, source);
      const ast = parser.parse();
      const parseTime = performance.now() - parseStart;
      
      // Validate AST
      this.validator.validateAST(ast, source);
      
      if (this.config.enableDebugMode) {
        console.log(`[DEBUG] Parsing: ${parseTime.toFixed(2)}ms, AST depth: ${this.getASTDepth(ast)}`);
      }
      
      // Optimized interpretation
      const interpretStart = performance.now();
      const host = this.createOptimizedHostInterface(source, options);
      const interpreter = this.createOptimizedInterpreter(ast, host);
      
      // Set up execution timeout
      const result = await this.executeWithTimeout(interpreter, host);
      const interpretTime = performance.now() - interpretStart;
      
      // Update statistics
      const executionTime = performance.now() - startTime;
      this.updateStats(executionTime, false, lexTime, parseTime, interpretTime);
      
      if (this.config.showTimings) {
        console.log(`[TIMING] Total: ${executionTime.toFixed(2)}ms (Lex: ${lexTime.toFixed(2)}ms, Parse: ${parseTime.toFixed(2)}ms, Interpret: ${interpretTime.toFixed(2)}ms)`);
      }
      
      // Clean up AST if pooling is enabled
      if (this.config.enableOptimizations) {
        this.astPool.releaseTree(ast);
      }
      
      return {
        result,
        executionTime,
        success: true,
        breakdown: {
          lexingTime: lexTime,
          parsingTime: parseTime,
          interpretingTime: interpretTime
        }
      };
      
    } catch (error) {
      const executionTime = performance.now() - startTime;
      this.updateStats(executionTime, true);
      
      // Format error for display
      if (error instanceof BabaError) {
        const formattedError = this.config.verboseErrors ? error.formatError() : error.message;
        
        return {
          error: formattedError,
          errorType: error.name,
          executionTime,
          success: false,
          suggestions: error.suggestions
        };
      } else {
        // Unexpected error
        if (this.config.enableDebugMode) {
          console.error('[INTERNAL ERROR]', error);
        }
        return {
          error: 'Internal error occurred',
          errorType: 'InternalError',
          executionTime,
          success: false,
          suggestions: ['Report this as a bug', 'Check for malformed input']
        };
      }
    }
  }

  /**
   * Synchronous execution for simple cases
   */
  executeSync(source, options = {}) {
    // Simple implementation for sync cases
    let result;
    let error;
    
    this.execute(source, options).then(
      res => { result = res; },
      err => { error = err; }
    );
    
    // Simple busy wait (not recommended for production)
    const start = Date.now();
    while (result === undefined && error === undefined && Date.now() - start < 1000) {
      // Wait
    }
    
    if (error) throw error;
    return result;
  }

  // [Include all the optimization methods from engine-optimized.js]
  
  createOptimizedParser(tokens, source) {
    const parser = createParser(tokens, this.config.enableDebugMode, source);
    
    if (this.config.enableOptimizations) {
      const originalParse = parser.parse.bind(parser);
      parser.parse = () => {
        const ast = originalParse();
        this.stats.optimizationStats.astPoolHits += this.astPool.getStats().poolHits;
        return ast;
      };
    }
    
    return parser;
  }

  createOptimizedInterpreter(ast, host) {
    const interpreter = createInterpreter(ast, host);
    
    if (this.config.enableOptimizations) {
      // Replace scope with optimized scope stack
      const originalScope = interpreter.scope;
      const optimizedScope = new CompatibleScopeStack();
      
      // Copy existing scope data
      for (const [key, value] of originalScope.entries()) {
        optimizedScope.set(key, value);
      }
      
      interpreter.scope = optimizedScope;
      
      // Inject optimized built-ins
      this.injectOptimizedBuiltins(interpreter);
    }
    
    return interpreter;
  }

  injectOptimizedBuiltins(interpreter) {
    const originalVisitFunctionCall = interpreter.visitFunctionCall;
    
    interpreter.visitFunctionCall = (node) => {
      // Try optimized path first
      if (node.callee && node.callee.type === 'Identifier') {
        const functionName = node.callee.name;
        const args = node.arguments.map(arg => interpreter.visit(arg));
        
        if (this.optimizedBuiltins.canOptimize(functionName, args)) {
          const result = this.optimizedBuiltins.execute(functionName, args, interpreter);
          if (result !== null) {
            this.stats.optimizationStats.builtinOptimizations++;
            return result;
          }
        }
      }
      
      // Fall back to standard implementation
      return originalVisitFunctionCall.call(interpreter, node);
    };
  }

  createOptimizedHostInterface(source, options) {
    return {
      source,
      scope: options.scope || new Map(),
      io: {
        out: (...args) => {
          if (options.silent) return;
          
          if (options.onOutput) {
            options.onOutput(...args);
          } else {
            console.log(...args);
          }
        },
        in: () => {
          if (options.onInput) {
            return options.onInput();
          } else {
            throw new BabaError('Input not available in this context');
          }
        },
        emit: (event) => {
          if (options.onEvent) {
            options.onEvent(event);
          }
        },
        addListener: (topic, handler) => {
          if (options.onAddListener) {
            return options.onAddListener(topic, handler);
          }
          return () => {};
        },
        debug: this.config.enableDebugMode ? console.log : () => {},
        ...this.config.ioHandlers
      },
      optimizations: this.config.enableOptimizations ? {
        builtins: this.optimizedBuiltins,
        astPool: this.astPool
      } : undefined
    };
  }

  async executeWithTimeout(interpreter, host) {
    let timeoutId;
    
    const executionPromise = new Promise((resolve, reject) => {
      try {
        const result = interpreter.interpret();
        resolve(result);
      } catch (error) {
        reject(error);
      }
    });
    
    const timeoutPromise = new Promise((_, reject) => {
      timeoutId = setTimeout(() => {
        reject(new BabaError(
          `Execution timeout after ${this.config.maxExecutionTime}ms`,
          null,
          host.source,
          ['Reduce recursion depth', 'Optimize algorithm complexity', 'Increase maxExecutionTime']
        ));
      }, this.config.maxExecutionTime);
    });
    
    try {
      const result = await Promise.race([executionPromise, timeoutPromise]);
      clearTimeout(timeoutId);
      return result;
    } catch (error) {
      clearTimeout(timeoutId);
      throw error;
    }
  }

  getASTDepth(node, depth = 0) {
    if (!node || typeof node !== 'object') {
      return depth;
    }

    let maxDepth = depth;
    const childFields = ['body', 'left', 'right', 'operand', 'callee', 'arguments', 'elements', 'discriminants', 'cases'];
    
    for (const field of childFields) {
      const child = node[field];
      if (child) {
        if (Array.isArray(child)) {
          for (const item of child) {
            maxDepth = Math.max(maxDepth, this.getASTDepth(item, depth + 1));
          }
        } else {
          maxDepth = Math.max(maxDepth, this.getASTDepth(child, depth + 1));
        }
      }
    }

    return maxDepth;
  }

  updateStats(executionTime, isError, lexTime = 0, parseTime = 0, interpretTime = 0) {
    this.stats.totalExecutions++;
    this.stats.totalTime += executionTime;
    this.stats.averageTime = this.stats.totalTime / this.stats.totalExecutions;
    this.stats.lexingTime += lexTime;
    this.stats.parsingTime += parseTime;
    this.stats.interpretingTime += interpretTime;
    
    if (isError) {
      this.stats.errors++;
    }
  }

  getStats() {
    const builtinStats = this.optimizedBuiltins.getStats();
    const astPoolStats = this.astPool.getStats();
    
    return {
      ...this.stats,
      errorRate: this.stats.totalExecutions > 0 ? this.stats.errors / this.stats.totalExecutions : 0,
      averageLexTime: this.stats.totalExecutions > 0 ? this.stats.lexingTime / this.stats.totalExecutions : 0,
      averageParseTime: this.stats.totalExecutions > 0 ? this.stats.parsingTime / this.stats.totalExecutions : 0,
      averageInterpretTime: this.stats.totalExecutions > 0 ? this.stats.interpretingTime / this.stats.totalExecutions : 0,
      optimizations: {
        builtinOptimizationRate: builtinStats.optimizationRate,
        astPoolHitRate: astPoolStats.hitRate,
        astPoolReuseRate: astPoolStats.reuseRate,
        totalOptimizations: this.stats.optimizationStats.builtinOptimizations + this.stats.optimizationStats.astPoolHits
      }
    };
  }

  resetStats() {
    this.stats = {
      totalExecutions: 0,
      totalTime: 0,
      averageTime: 0,
      errors: 0,
      lexingTime: 0,
      parsingTime: 0,
      interpretingTime: 0,
      optimizationStats: {
        lexerOptimizations: 0,
        scopeOptimizations: 0,
        builtinOptimizations: 0,
        astPoolHits: 0
      }
    };
    
    this.optimizedBuiltins.resetStats();
    this.astPool.resetStats();
  }
}

/**
 * Convenience function for quick execution
 */
export async function execute(source, config = new BabaYagaConfig({ enableOptimizations: true })) {
  const engine = new BabaYagaEngine(config);
  return engine.execute(source);
}

/**
 * Create engine with preset configurations
 */
export function createEngine(preset = 'default') {
  let config;
  
  switch (preset) {
    case 'development':
      config = BabaYagaConfig.development();
      config.enableOptimizations = true;
      break;
    case 'production':
      config = BabaYagaConfig.production();
      config.enableOptimizations = true;
      break;
    case 'testing':
      config = BabaYagaConfig.testing();
      config.enableOptimizations = true;
      break;
    case 'sandbox':
      config = BabaYagaConfig.sandbox();
      config.enableOptimizations = true;
      break;
    default:
      config = new BabaYagaConfig({ enableOptimizations: true });
  }
  
  return new BabaYagaEngine(config);
}