/**
 * Grammar Generator
 * 
 * Converts collected user information into Tree-sitter grammar.js files
 * with paradigm-aware rule generation
 */

import { LanguageArchitecture, LanguageFeatures, LanguageSyntax } from '../commands/new.js';

export interface GrammarRule {
  name: string;
  definition: string;
  comment?: string;
}

export interface GeneratedGrammar {
  name: string;
  rules: GrammarRule[];
  extras: string[];
  conflicts: string[][];
  precedences: string[][];
  word?: string;
}

/**
 * Generate a complete Tree-sitter grammar from user specifications
 */
export function generateGrammar(
  architecture: LanguageArchitecture,
  features: LanguageFeatures,
  syntax: LanguageSyntax
): GeneratedGrammar {
  const rules: GrammarRule[] = [];
  const extras: string[] = [];
  
  // Start with the root rule - this varies by paradigm
  rules.push(generateRootRule(architecture, features));
  
  // Add basic token rules
  rules.push(...generateTokenRules(syntax));
  
  // Add paradigm-specific rules
  rules.push(...generateParadigmRules(architecture, features, syntax));
  
  // Add data structure rules if specified
  if (features.dataStructures.length > 0) {
    rules.push(...generateDataStructureRules(features.dataStructures));
  }
  
  // Add control flow rules if specified
  if (features.controlFlow.length > 0) {
    rules.push(...generateControlFlowRules(features.controlFlow, syntax));
  }
  
  // Set up extras (whitespace and comments)
  extras.push('/\\s/', `$.${getCommentRuleName(syntax.comments.pattern)}`);
  
  return {
    name: architecture.name,
    rules,
    extras,
    conflicts: [], // TODO: Add conflicts if needed
    precedences: generatePrecedences(architecture, features),
    word: 'identifier' // Most languages use identifier as word token
  };
}

/**
 * Generate the root rule based on language paradigm
 */
function generateRootRule(architecture: LanguageArchitecture, features: LanguageFeatures): GrammarRule {
  let definition: string;
  
  switch (architecture.paradigm) {
    case 'declarative':
      definition = 'repeat(choice($.rule_declaration, $.constraint, $.fact))';
      break;
    case 'functional':
      definition = 'repeat(choice($.function_definition, $.expression, $.binding))';
      break;
    case 'object-oriented':
      definition = 'repeat(choice($.class_definition, $.statement, $.expression))';
      break;
    case 'procedural':
    case 'mixed':
    default:
      definition = 'repeat(choice($.statement, $.expression, $.declaration))';
      break;
  }
  
  return {
    name: 'source_file',
    definition,
    comment: `Root rule for ${architecture.paradigm} language`
  };
}

/**
 * Generate basic token rules (identifiers, numbers, strings, comments)
 */
function generateTokenRules(syntax: LanguageSyntax): GrammarRule[] {
  const rules: GrammarRule[] = [];
  
  // Identifier
  rules.push({
    name: 'identifier',
    definition: `/${syntax.identifiers.pattern}/`,
    comment: `Identifiers: ${syntax.identifiers.examples.join(', ')}`
  });
  
  // Numbers
  rules.push({
    name: 'number',
    definition: `/${syntax.numbers.pattern}/`,
    comment: `Numbers: ${syntax.numbers.examples.join(', ')}`
  });
  
  // Strings
  rules.push({
    name: 'string',
    definition: `/${syntax.strings.pattern}/`,
    comment: `Strings: ${syntax.strings.examples.join(', ')}`
  });
  
  // Comments
  const commentRuleName = getCommentRuleName(syntax.comments.pattern);
  rules.push({
    name: commentRuleName,
    definition: `/${escapeRegex(syntax.comments.pattern)}.*$/`,
    comment: `Line comments starting with ${syntax.comments.pattern}`
  });
  
  return rules;
}

/**
 * Generate paradigm-specific rules
 */
function generateParadigmRules(
  architecture: LanguageArchitecture,
  features: LanguageFeatures,
  syntax: LanguageSyntax
): GrammarRule[] {
  const rules: GrammarRule[] = [];
  
  // Variable declarations (common to most paradigms)
  rules.push({
    name: 'variable_declaration',
    definition: `seq("${syntax.variables.keyword}", $.identifier, "${syntax.variables.operator}", $.expression, "${syntax.variables.terminator}")`,
    comment: `Variable declarations: ${syntax.variables.example}`
  });
  
  // Expression rule (fundamental to all paradigms)
  rules.push(generateExpressionRule(architecture, features));
  
  // Statement rule (for imperative paradigms)
  if (['procedural', 'object-oriented', 'mixed'].includes(architecture.paradigm)) {
    rules.push(generateStatementRule(architecture, features));
  }
  
  // Add paradigm-specific constructs
  switch (architecture.paradigm) {
    case 'object-oriented':
      if (syntax.paradigmExamples.class) {
        rules.push(generateClassRule(syntax.paradigmExamples.class));
      }
      break;
    case 'functional':
      if (syntax.paradigmExamples.function) {
        rules.push(generateFunctionRule(syntax.paradigmExamples.function, features.functionTypes));
      }
      break;
    case 'declarative':
      if (syntax.paradigmExamples.rule) {
        rules.push(generateDeclarativeRule(syntax.paradigmExamples.rule));
      }
      break;
  }
  
  return rules;
}

/**
 * Generate expression rule based on paradigm
 */
function generateExpressionRule(architecture: LanguageArchitecture, features: LanguageFeatures): GrammarRule {
  const choices = [
    '$.identifier',
    '$.number', 
    '$.string',
    '$.parenthesized_expression'
  ];
  
  // Add function calls if functions are supported
  if (features.functionTypes.length > 0) {
    choices.push('$.function_call');
  }
  
  // Add data structure literals
  if (features.dataStructures.includes('arrays')) {
    choices.push('$.array_literal');
  }
  if (features.dataStructures.includes('objects')) {
    choices.push('$.object_literal');
  }
  
  // Add binary operations for most paradigms
  if (architecture.paradigm !== 'declarative') {
    choices.push('$.binary_expression');
  }
  
  return {
    name: 'expression',
    definition: `choice(${choices.join(', ')})`,
    comment: 'Expression rule covering all expression types'
  };
}

/**
 * Generate statement rule for imperative paradigms
 */
function generateStatementRule(architecture: LanguageArchitecture, features: LanguageFeatures): GrammarRule {
  const choices = [
    '$.variable_declaration',
    '$.expression_statement'
  ];
  
  // Add control flow statements
  if (features.controlFlow.includes('conditionals')) {
    choices.push('$.if_statement');
  }
  if (features.controlFlow.includes('loops')) {
    choices.push('$.for_statement', '$.while_statement');
  }
  
  return {
    name: 'statement',
    definition: `choice(${choices.join(', ')})`,
    comment: 'Statement rule for imperative constructs'
  };
}

/**
 * Generate data structure rules
 */
function generateDataStructureRules(dataStructures: string[]): GrammarRule[] {
  const rules: GrammarRule[] = [];
  
  if (dataStructures.includes('arrays')) {
    rules.push({
      name: 'array_literal',
      definition: 'seq("[", optional(seq($.expression, repeat(seq(",", $.expression)))), "]")',
      comment: 'Array literals: [1, 2, 3]'
    });
  }
  
  if (dataStructures.includes('objects')) {
    rules.push({
      name: 'object_literal',
      definition: 'seq("{", optional(seq($.property, repeat(seq(",", $.property)))), "}")',
      comment: 'Object literals: {key: value}'
    });
    
    rules.push({
      name: 'property',
      definition: 'seq(choice($.identifier, $.string), ":", $.expression)',
      comment: 'Object property: key: value'
    });
  }
  
  if (dataStructures.includes('tuples')) {
    rules.push({
      name: 'tuple_literal',
      definition: 'seq("(", $.expression, repeat1(seq(",", $.expression)), ")")',
      comment: 'Tuple literals: (a, b, c)'
    });
  }
  
  return rules;
}

/**
 * Generate control flow rules
 */
function generateControlFlowRules(controlFlow: string[], syntax: LanguageSyntax): GrammarRule[] {
  const rules: GrammarRule[] = [];
  
  if (controlFlow.includes('conditionals')) {
    rules.push({
      name: 'if_statement',
      definition: 'seq("if", "(", $.expression, ")", $.block, optional(seq("else", choice($.if_statement, $.block))))',
      comment: 'If-else statements'
    });
    
    rules.push({
      name: 'block',
      definition: 'seq("{", repeat($.statement), "}")',
      comment: 'Code blocks'
    });
  }
  
  if (controlFlow.includes('loops')) {
    rules.push({
      name: 'while_statement',
      definition: 'seq("while", "(", $.expression, ")", $.block)',
      comment: 'While loops'
    });
    
    rules.push({
      name: 'for_statement',
      definition: 'seq("for", "(", optional($.statement), ";", optional($.expression), ";", optional($.expression), ")", $.block)',
      comment: 'For loops'
    });
  }
  
  return rules;
}

/**
 * Generate class rule from user example
 */
function generateClassRule(classExample: string): GrammarRule {
  // Simple class rule - could be enhanced with more parsing
  return {
    name: 'class_definition',
    definition: 'seq("class", $.identifier, "{", repeat($.method_definition), "}")',
    comment: `Class definition based on: ${classExample}`
  };
}

/**
 * Generate function rule from user example
 */
function generateFunctionRule(functionExample: string, functionTypes: string[]): GrammarRule {
  let definition = 'seq("function", $.identifier, "(", optional($.parameter_list), ")", $.block)';
  
  // Add arrow functions if supported
  if (functionTypes.includes('anonymous')) {
    definition = `choice(${definition}, $.arrow_function)`;
  }
  
  return {
    name: 'function_definition',
    definition,
    comment: `Function definition based on: ${functionExample}`
  };
}

/**
 * Generate declarative rule from user example
 */
function generateDeclarativeRule(ruleExample: string): GrammarRule {
  return {
    name: 'rule_declaration',
    definition: 'seq("rule", $.identifier, optional(seq("when", $.expression)))',
    comment: `Rule declaration based on: ${ruleExample}`
  };
}

/**
 * Generate precedences based on paradigm
 */
function generatePrecedences(architecture: LanguageArchitecture, features: LanguageFeatures): string[][] {
  // Basic precedence for binary operations
  const precedences = [
    ['$.binary_expression']
  ];
  
  // Add function call precedence if functions are supported
  if (features.functionTypes.length > 0) {
    precedences.push(['$.function_call']);
  }
  
  return precedences;
}

/**
 * Generate the complete grammar.js file content
 */
export function generateGrammarFile(grammar: GeneratedGrammar): string {
  const lines: string[] = [];
  
  lines.push('/**');
  lines.push(` * Grammar for ${grammar.name}`);
  lines.push(' * Generated by DSK (DSL Development Kit)');
  lines.push(' */');
  lines.push('');
  lines.push('module.exports = grammar({');
  lines.push(`  name: '${grammar.name}',`);
  lines.push('');
  
  // Add word token if specified
  if (grammar.word) {
    lines.push(`  word: $ => $.${grammar.word},`);
    lines.push('');
  }
  
  // Add rules
  lines.push('  rules: {');
  
  grammar.rules.forEach((rule, index) => {
    if (rule.comment) {
      lines.push(`    // ${rule.comment}`);
    }
    lines.push(`    ${rule.name}: $ => ${rule.definition}${index < grammar.rules.length - 1 ? ',' : ''}`);
    if (index < grammar.rules.length - 1) {
      lines.push('');
    }
  });
  
  lines.push('  }');
  
  // Add extras
  if (grammar.extras.length > 0) {
    lines.push(',');
    lines.push('');
    lines.push('  extras: $ => [');
    grammar.extras.forEach((extra, index) => {
      lines.push(`    ${extra}${index < grammar.extras.length - 1 ? ',' : ''}`);
    });
    lines.push('  ]');
  }
  
  // Add conflicts if any
  if (grammar.conflicts.length > 0) {
    lines.push(',');
    lines.push('');
    lines.push('  conflicts: $ => [');
    grammar.conflicts.forEach((conflict, index) => {
      lines.push(`    [${conflict.join(', ')}]${index < grammar.conflicts.length - 1 ? ',' : ''}`);
    });
    lines.push('  ]');
  }
  
  // Add precedences if any
  if (grammar.precedences.length > 0) {
    lines.push(',');
    lines.push('');
    lines.push('  precedences: $ => [');
    grammar.precedences.forEach((prec, index) => {
      lines.push(`    [${prec.join(', ')}]${index < grammar.precedences.length - 1 ? ',' : ''}`);
    });
    lines.push('  ]');
  }
  
  lines.push('});');
  lines.push('');
  
  return lines.join('\n');
}

/**
 * Helper functions
 */
function getCommentRuleName(commentPattern: string): string {
  switch (commentPattern) {
    case '//': return 'line_comment_slash';
    case '#': return 'line_comment_hash';
    case ';': return 'line_comment_semicolon';
    default: return 'line_comment';
  }
}

function escapeRegex(pattern: string): string {
  return pattern.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
}