Plugin System

/**
 * Resolve plugin by name or path
 * @param {string} name - Plugin name or path to resolve
 * @returns {Object} Resolved plugin object
 */
function resolvePlugin(name);

/**
 * Resolve preset by name or path  
 * @param {string} name - Preset name or path to resolve
 * @returns {Object} Resolved preset object
 */
function resolvePreset(name);

const babel = require("babel-core");

// Resolve plugin by name
const arrowPlugin = babel.resolvePlugin("transform-es2015-arrow-functions");
console.log(arrowPlugin); // Plugin object

// Resolve preset by name  
const es2015Preset = babel.resolvePreset("es2015");
console.log(es2015Preset); // Preset configuration

// Use resolved plugins in transform
const result = babel.transform("const fn = () => 42;", {
  plugins: [arrowPlugin]
});
console.log(result.code);

/**
 * Option Manager for processing transformation options
 */
class OptionManager {
  /**
   * Create new OptionManager instance
   * @param {Logger} log - Logger instance (optional)
   * @param {Pipeline} pipeline - Pipeline instance (optional)
   */
  constructor(log, pipeline);
  
  /**
   * Initialize and normalize options
   * @param {Object} opts - Raw options object
   * @returns {Object} Normalized options
   */
  init(opts);
  
  /**
   * Create bare options object with defaults
   * @returns {Object} Default options object
   */
  static createBareOptions();
  
  /**
   * Normalize plugin object
   * @param {any} plugin - Plugin to normalize
   * @param {string} loc - Plugin location for errors
   * @param {number} i - Plugin index for errors
   * @param {string} alias - Plugin alias
   * @returns {Plugin} Normalized plugin instance
   */
  static normalisePlugin(plugin, loc, i, alias);
}

// Access OptionManager
const OptionManager = babel.OptionManager;

const babel = require("babel-core");

// Create option manager
const OptionManager = babel.OptionManager;
const optionManager = new OptionManager();

// Process raw options
const rawOptions = {
  presets: ["es2015"],
  plugins: ["transform-runtime"],
  sourceMaps: true,
  filename: "input.js"
};

const normalizedOptions = optionManager.init(rawOptions);
console.log(normalizedOptions); // Fully processed options

// Create default options
const defaultOptions = OptionManager.createBareOptions();
console.log(defaultOptions); // Default option set

/**
 * Configuration schema object defining all available Babel options
 */
const options;

const babel = require("babel-core");

// Access configuration schema
console.log(babel.options);  // Configuration schema object

// Schema includes definitions for:
// - filename, filenameRelative, inputSourceMap
// - env, mode, retainLines, highlightCode
// - presets, plugins, babelrc, extends
// - ignore, only, sourceMaps, sourceType
// - parserOpts, generatorOpts, etc.

// Use schema for validation or tool integration
function validateBabelConfig(userConfig) {
  const schema = babel.options;
  
  // Validate user config against schema
  for (const key in userConfig) {
    if (!(key in schema)) {
      console.warn(`Unknown option: ${key}`);
    }
  }
  
  return userConfig;
}

const config = validateBabelConfig({
  presets: ['es2015'],
  sourceMaps: true,
  filename: 'input.js'
});

// Plugin configuration formats (multiple valid types):
// - string: Plugin name
// - Function: Plugin function  
// - [string]: Plugin name in array
// - [string, Object]: Plugin with options
// - [Function, Object]: Plugin function with options
// - PluginObject: Direct plugin object

// PluginObject structure:
const pluginObject = {
  visitor: Object,          // VisitorObject with AST visitor methods
  pre: Function,            // Pre-transformation hook (optional)
  post: Function,           // Post-transformation hook (optional)
  manipulateOptions: Function, // Option manipulation hook (optional)
  inherits: Object,         // Plugin inheritance (optional)
  name: String             // Plugin name (optional)
};

// VisitorObject structure:
const visitorObject = {
  // Each nodeType can be:
  // - Function (single visitor function)
  // - { enter: Function, exit: Function } (enter/exit visitors)
  // - Array<Function> (multiple visitors)
  Identifier: Function,
  FunctionDeclaration: {
    enter: Function,
    exit: Function
  },
  CallExpression: [Function, Function]  // Multiple visitors
};

// String plugin names
{
  plugins: [
    "transform-es2015-arrow-functions",
    "transform-es2015-classes"
  ]
}

// Plugin with options
{
  plugins: [
    ["transform-es2015-modules-commonjs", {
      allowTopLevelThis: true,
      strict: false
    }]
  ]
}

// Function plugin
{
  plugins: [
    function customPlugin(babel) {
      const t = babel.types;
      return {
        visitor: {
          Identifier(path) {
            if (path.node.name === "oldName") {
              path.node.name = "newName";
            }
          }
        }
      };
    }
  ]
}

// Plugin object
{
  plugins: [
    {
      visitor: {
        CallExpression: {
          enter(path) {
            console.log("Entering call expression");
          },
          exit(path) {
            console.log("Exiting call expression");
          }
        }
      },
      pre(file) {
        console.log("Starting transformation of:", file.opts.filename);
      },
      post(file) {
        console.log("Finished transformation of:", file.opts.filename);
      }
    }
  ]
}

// Preset configuration formats
type PresetConfig =
  | string                          // Preset name
  | Function                        // Preset function  
  | [string]                        // Preset name in array
  | [string, Object]                // Preset with options
  | [Function, Object]              // Preset function with options
  | PresetObject;                   // Direct preset object

interface PresetObject {
  plugins?: Array<PluginConfig>;    // Plugins in preset
  presets?: Array<PresetConfig>;    // Sub-presets
  options?: Object;                 // Preset options
}

// Basic preset usage
{
  presets: ["es2015", "react"]
}

// Preset with options
{
  presets: [
    ["es2015", {
      modules: false,    // Keep ES6 modules
      loose: true       // Use loose transformations
    }],
    ["react", {
      pragma: "h"       // Use 'h' instead of React.createElement
    }]
  ]
}

// Custom preset function
{
  presets: [
    function customPreset(context, options = {}) {
      return {
        plugins: [
          "transform-es2015-arrow-functions",
          "transform-es2015-classes",
          options.includeRuntime ? "transform-runtime" : null
        ].filter(Boolean)
      };
    }
  ]
}

// Environment-specific presets
{
  presets: [
    ["es2015", { modules: false }]
  ],
  env: {
    test: {
      presets: [
        ["es2015", { modules: "commonjs" }]  // CommonJS for testing
      ]
    }
  }
}

// Complete plugin with all hooks
function myCustomPlugin(babel) {
  const t = babel.types;
  
  return {
    name: "my-custom-plugin",
    
    // Pre-transformation setup
    pre(file) {
      this.customData = new Map();
      console.log("Processing file:", file.opts.filename);
    },
    
    // Visitor pattern for AST transformation
    visitor: {
      // Transform arrow functions
      ArrowFunctionExpression(path) {
        const { node } = path;
        
        // Convert to function expression
        const funcExpr = t.functionExpression(
          null, // no name
          node.params,
          t.isExpression(node.body) 
            ? t.blockStatement([t.returnStatement(node.body)])
            : node.body
        );
        
        path.replaceWith(funcExpr);
      },
      
      // Track variable declarations
      VariableDeclarator: {
        enter(path) {
          const name = path.node.id.name;
          this.customData.set(name, path.node.init);
        }
      },
      
      // Transform specific identifiers
      Identifier(path) {
        if (path.node.name === "DEBUG" && path.isReferencedIdentifier()) {
          path.replaceWith(t.booleanLiteral(process.env.NODE_ENV !== 'production'));
        }
      }
    },
    
    // Post-transformation cleanup
    post(file) {
      console.log("Transformed variables:", Array.from(this.customData.keys()));
      this.customData.clear();
    },
    
    // Manipulate parser options
    manipulateOptions(opts, parserOpts) {
      // Enable JSX parsing if not already enabled
      if (!parserOpts.plugins.includes('jsx')) {
        parserOpts.plugins.push('jsx');
      }
    }
  };
}

// Use custom plugin
const result = babel.transform(code, {
  plugins: [myCustomPlugin]
});

// Plugin with options and state
function configurablePlugin(babel, options = {}) {
  const t = babel.types;
  const { 
    prefix = 'transformed_',
    exclude = [],
    verbose = false 
  } = options;
  
  return {
    visitor: {
      Identifier: {
        enter(path, state) {
          // Access plugin options
          const shouldTransform = !exclude.includes(path.node.name);
          
          // Access file-level state
          if (!state.transformedCount) {
            state.transformedCount = 0;
          }
          
          if (shouldTransform && path.isReferencedIdentifier()) {
            const newName = prefix + path.node.name;
            path.node.name = newName;
            state.transformedCount++;
            
            if (verbose) {
              console.log(`Transformed identifier: ${path.node.name} -> ${newName}`);
            }
          }
        }
      }
    },
    
    post(file) {
      if (verbose) {
        console.log(`Total transformations: ${file.transformedCount || 0}`);
      }
    }
  };
}

// Usage with options
const result = babel.transform(code, {
  plugins: [
    [configurablePlugin, {
      prefix: 'renamed_',
      exclude: ['React', 'document'],
      verbose: true
    }]
  ]
});

// EnvironmentConfig structure:
const environmentConfig = {
  env: {
    // Environment-specific configurations
    development: {
      plugins: Array,     // Development plugins
      presets: Array,     // Development presets
      sourceMaps: Boolean // Any other options
    },
    production: {
      plugins: Array,     // Production plugins  
      presets: Array,     // Production presets
      minified: Boolean   // Any other options
    },
    test: {
      plugins: Array,     // Test plugins
      presets: Array      // Test presets
    }
    // Additional environments...
  }
};

// Environment-based configuration
const babelConfig = {
  presets: [
    ["es2015", { modules: false }]
  ],
  plugins: [
    "transform-object-rest-spread"
  ],
  env: {
    // Development environment
    development: {
      plugins: [
        "transform-react-jsx-source",     // Add source info for debugging
        "transform-react-jsx-self"        // Add __self prop
      ]
    },
    
    // Production environment  
    production: {
      plugins: [
        "transform-react-remove-prop-types", // Remove PropTypes
        "babel-plugin-transform-react-constant-elements" // Optimize React
      ]
    },
    
    // Test environment
    test: {
      presets: [
        ["es2015", { modules: "commonjs" }] // CommonJS for Jest
      ],
      plugins: [
        "transform-dynamic-import"          // Transform dynamic imports
      ]
    }
  }
};

// Environment is determined by BABEL_ENV or NODE_ENV
process.env.NODE_ENV = 'production';
const result = babel.transform(code, babelConfig);

// Dynamic plugin configuration
function createBabelConfig(options = {}) {
  const plugins = [
    "transform-object-rest-spread"
  ];
  
  // Conditionally add plugins
  if (options.includeRuntime) {
    plugins.push(["transform-runtime", {
      polyfill: false,
      regenerator: true
    }]);
  }
  
  if (options.optimizeReact) {
    plugins.push(
      "transform-react-constant-elements",
      "transform-react-inline-elements"
    );
  }
  
  if (options.removeConsole) {
    plugins.push(["transform-remove-console", {
      exclude: ["error", "warn"]
    }]);
  }
  
  return {
    presets: [
      ["es2015", { modules: options.modules || false }]
    ],
    plugins
  };
}

// Usage
const devConfig = createBabelConfig({
  includeRuntime: true,
  modules: "commonjs"
});

const prodConfig = createBabelConfig({
  optimizeReact: true,
  removeConsole: true
});

// Plugin resolution follows these patterns:
const resolutionExamples = {
  // Scoped plugins
  "@babel/plugin-transform-arrow-functions": "@babel/plugin-transform-arrow-functions",
  
  // Short names resolve to babel-plugin-*
  "transform-arrow-functions": "babel-plugin-transform-arrow-functions",
  
  // Relative paths
  "./custom-plugin": "./custom-plugin.js",
  
  // Absolute paths  
  "/path/to/plugin": "/path/to/plugin.js",
  
  // Node modules
  "my-babel-plugin": "my-babel-plugin"
};

// Preset resolution follows similar patterns with babel-preset-* prefix

// Plugin loading error handling
try {
  const result = babel.transform(code, {
    plugins: ["nonexistent-plugin"]
  });
} catch (err) {
  if (err.message.includes('Cannot resolve plugin')) {
    console.error('Plugin not found:', err.message);
    // Fallback configuration
    const fallbackResult = babel.transform(code, {
      presets: ["es2015"] // Use preset instead
    });
  }
}

// Preset loading error handling
try {
  const result = babel.transform(code, {
    presets: ["invalid-preset"]  
  });
} catch (err) {
  if (err.message.includes('Cannot resolve preset')) {
    console.error('Preset not found:', err.message);
  }
}