# All files / src/semantics index.js

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     /**
     * Semantic Analysis
     *
     * The semantic analyzer below accepts a Walt AST and maps it, returning a new
     * transformed AST which contains all necessary data to generate the final
     * WebAssembly binary.
     *
     * The transformations may or may not create new nodes or attach metadata to
     * existing nodes.
     *
     * Metadata is information necessary to generate a valid binary, like type info.
     */

    // @flow
    import { combineParsers } from '../plugin';
    import { map } from 'walt-parser-tools/map-node';
    import { enter as enterScope } from 'walt-parser-tools/scope';
    import { AST_METADATA } from './metadata';
    import core from '../core';
    import base from '../base';
    import _types from '../core/types';
    import unary from '../core/unary';
    import _function from '../core/function';
    import _imports from '../core/imports';
    import booleans from '../core/bool';
    import array from '../core/array';
    import memory from '../core/memory';
    import statics from '../core/statics';
    import functionPointer from '../core/function-pointer';
    import struct from '../core/struct';
    import native from '../core/native';
    import defaultArguments from '../syntax-sugar/default-arguments';
    import sizeof from '../syntax-sugar/sizeof';
    import { GLOBAL_INDEX } from './metadata.js';
    import type {
      NodeType,
      Context,
      SemanticOptions,
      SemanticsFactory,
    } from '../flow/types';

    export const builtinSemantics = [
      base,
      core,
      _imports,
      _types,
      unary,
      _function,
      booleans,
      array,
      memory,
      statics,
      functionPointer,
      struct,
      native,
      sizeof,
      defaultArguments,
    ];

    const getBuiltInParsers = (): SemanticsFactory[] => {
      return [
        base().semantics,
        core().semantics,
        _imports().semantics,
        _types().semantics,
        unary().semantics,
        _function().semantics,
        booleans().semantics,
        array().semantics,
        memory().semantics,
        statics().semantics,
        functionPointer().semantics,
        struct().semantics,
        native().semantics,
        sizeof().semantics,
        defaultArguments().semantics,
      ];
    };

    // Return AST with full transformations applied
    function semantics(
      ast: NodeType,
      extraSemantics: SemanticsFactory[] = [],
      options: SemanticOptions
    ): NodeType {
      // Generate all the plugin instances with proper options
      const plugins = [...getBuiltInParsers(), ...extraSemantics];

      // Here each semantics parser will receive a reference to the parser & fragment
      // this allows a semantic parser to utilize the same grammar rules as the rest
      // of the program.
      const combined = combineParsers(plugins.map(p => p(options)));

      // The context is what we use to transfer state from one parser to another.
      // Global state like type information and scope chains for example.
      const context: Context = {
        functions: {},
        types: {},
        userTypes: {},
        table: {},
        hoist: [],
        statics: {},
        path: [],
        scopes: enterScope([], GLOBAL_INDEX),
        memories: [],
        tables: [],
      };
      // Parse the current ast
      const parsed = map(combined)([ast, context]);

      const { functions, scopes, types, userTypes, statics, hoist } = context;
      return {
        ...parsed,
        meta: {
          ...parsed.meta,
          // Attach information collected to the AST
          [AST_METADATA]: {
            functions,
            globals: scopes[0],
            types,
            userTypes,
            statics,
          },
        },
        params: [...parsed.params, ...hoist],
      };
    }

    export default semantics;