/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */

import * as t from "@babel/types";

import getFunctionName from "../utils/getFunctionName";
import { getAst } from "../utils/ast";

/**
 * "implicit"
 * Variables added automaticly like "this" and "arguments"
 *
 * "var"
 * Variables declared with "var" or non-block function declarations
 *
 * "let"
 * Variables declared with "let".
 *
 * "const"
 * Variables declared with "const", or added as const
 * bindings like inner function expressions and inner class names.
 *
 * "import"
 * Imported binding names exposed from other modules.
 *
 * "global"
 * Variables that reference undeclared global values.
 */

// Location information about the expression immediartely surrounding a
// given binding reference.

function isGeneratedId(id) {
  return !/\/originalSource/.test(id);
}

export function parseSourceScopes(sourceId) {
  const ast = getAst(sourceId);
  if (!ast || !Object.keys(ast).length) {
    return null;
  }

  return buildScopeList(ast, sourceId);
}

export function buildScopeList(ast, sourceId) {
  const { global, lexical } = createGlobalScope(ast, sourceId);

  const state = {
    // The id for the source that scope list is generated for
    sourceId,

    // A map of any free variables(variables which are used within the current scope but not
    // declared within the scope). This changes when a new scope is created.
    freeVariables: new Map(),

    // A stack of all the free variables created across all the scopes that have
    // been created.
    freeVariableStack: [],

    inType: null,

    // The current scope, a new scope is potentially created on a visit to each node
    // depending in the criteria. Initially set to the lexical global scope which is the
    // child to the global scope.
    scope: lexical,

    // A stack of all the existing scopes, this is mainly used retrieve the parent scope
    // (which is the last scope push onto the stack) on exiting a visited node.
    scopeStack: [],

    declarationBindingIds: new Set(),
  };
  t.traverse(ast, scopeCollectionVisitor, state);

  for (const [key, freeVariables] of state.freeVariables) {
    let binding = global.bindings[key];
    if (!binding) {
      binding = {
        type: "global",
        refs: [],
      };
      global.bindings[key] = binding;
    }

    binding.refs = freeVariables.concat(binding.refs);
  }

  // TODO: This should probably check for ".mjs" extension on the
  // original file, and should also be skipped if the the generated
  // code is an ES6 module rather than a script.
  if (
    isGeneratedId(sourceId) ||
    (ast.program.sourceType === "script" && !looksLikeCommonJS(global))
  ) {
    stripModuleScope(global);
  }

  return toParsedScopes([global], sourceId) || [];
}

function toParsedScopes(children, sourceId) {
  if (!children || children.length === 0) {
    return undefined;
  }
  return children.map(scope => ({
    // Removing unneed information from TempScope such as parent reference.
    // We also need to convert BabelLocation to the Location type.
    start: scope.loc.start,
    end: scope.loc.end,
    type:
      scope.type === "module" || scope.type === "function-body"
        ? "block"
        : scope.type,
    scopeKind: "",
    displayName: scope.displayName,
    bindings: scope.bindings,
    children: toParsedScopes(scope.children, sourceId),
  }));
}

/**
 * Create a new scope object and link the scope to it parent.
 *
 * @param {String} type - scope type
 * @param {String} displayName - The scope display name
 * @param {Object} parent - The parent object scope
 * @param {Object} loc - The start and end postions (line/columns) of the scope
 * @returns {Object} The newly created scope
 */
function createTempScope(type, displayName, parent, loc) {
  const scope = {
    type,
    displayName,
    parent,

    // A list of all the child scopes
    children: [],
    loc,

    // All the bindings defined in this scope
    // bindings = [binding, ...]
    // binding = { type: "", refs: []}
    bindings: Object.create(null),
  };

  if (parent) {
    parent.children.push(scope);
  }
  return scope;
}

// Sets a new current scope and creates a new map to store the free variables
// that may exist in this scope.
function pushTempScope(state, type, displayName, loc) {
  const scope = createTempScope(type, displayName, state.scope, loc);

  state.scope = scope;

  state.freeVariableStack.push(state.freeVariables);
  state.freeVariables = new Map();
  return scope;
}

function isNode(node, type) {
  return node ? node.type === type : false;
}

// Walks up the scope tree to the top most variable scope
function getVarScope(scope) {
  let s = scope;
  while (s.type !== "function" && s.type !== "module") {
    if (!s.parent) {
      return s;
    }
    s = s.parent;
  }
  return s;
}

function fromBabelLocation(location, sourceId) {
  return {
    sourceId,
    line: location.line,
    column: location.column,
  };
}

function parseDeclarator(
  declaratorId,
  targetScope,
  type,
  locationType,
  declaration,
  state
) {
  if (isNode(declaratorId, "Identifier")) {
    let existing = targetScope.bindings[declaratorId.name];
    if (!existing) {
      existing = {
        type,
        refs: [],
      };
      targetScope.bindings[declaratorId.name] = existing;
    }
    state.declarationBindingIds.add(declaratorId);
    existing.refs.push({
      type: locationType,
      start: fromBabelLocation(declaratorId.loc.start, state.sourceId),
      end: fromBabelLocation(declaratorId.loc.end, state.sourceId),
      declaration: {
        start: fromBabelLocation(declaration.loc.start, state.sourceId),
        end: fromBabelLocation(declaration.loc.end, state.sourceId),
      },
    });
  } else if (isNode(declaratorId, "ObjectPattern")) {
    declaratorId.properties.forEach(prop => {
      parseDeclarator(
        prop.value,
        targetScope,
        type,
        locationType,
        declaration,
        state
      );
    });
  } else if (isNode(declaratorId, "ArrayPattern")) {
    declaratorId.elements.forEach(item => {
      parseDeclarator(
        item,
        targetScope,
        type,
        locationType,
        declaration,
        state
      );
    });
  } else if (isNode(declaratorId, "AssignmentPattern")) {
    parseDeclarator(
      declaratorId.left,
      targetScope,
      type,
      locationType,
      declaration,
      state
    );
  } else if (isNode(declaratorId, "RestElement")) {
    parseDeclarator(
      declaratorId.argument,
      targetScope,
      type,
      locationType,
      declaration,
      state
    );
  } else if (t.isTSParameterProperty(declaratorId)) {
    parseDeclarator(
      declaratorId.parameter,
      targetScope,
      type,
      locationType,
      declaration,
      state
    );
  }
}

function isLetOrConst(node) {
  return node.kind === "let" || node.kind === "const";
}

function hasLexicalDeclaration(node, parent) {
  const nodes = [];
  if (t.isSwitchStatement(node)) {
    for (const caseNode of node.cases) {
      nodes.push(...caseNode.consequent);
    }
  } else {
    nodes.push(...node.body);
  }

  const isFunctionBody = t.isFunction(parent, { body: node });

  return nodes.some(
    child =>
      isLexicalVariable(child) ||
      t.isClassDeclaration(child) ||
      (!isFunctionBody && t.isFunctionDeclaration(child))
  );
}
function isLexicalVariable(node) {
  return isNode(node, "VariableDeclaration") && isLetOrConst(node);
}

// Creates the global scopes for this source, the overall global scope
// and a lexical global scope.
function createGlobalScope(ast, sourceId) {
  const global = createTempScope("object", "Global", null, {
    start: fromBabelLocation(ast.loc.start, sourceId),
    end: fromBabelLocation(ast.loc.end, sourceId),
  });

  const lexical = createTempScope("block", "Lexical Global", global, {
    start: fromBabelLocation(ast.loc.start, sourceId),
    end: fromBabelLocation(ast.loc.end, sourceId),
  });

  return { global, lexical };
}

const scopeCollectionVisitor = {
  // eslint-disable-next-line complexity
  enter(node, ancestors, state) {
    state.scopeStack.push(state.scope);

    const parentNode =
      ancestors.length === 0 ? null : ancestors[ancestors.length - 1].node;

    if (state.inType) {
      return;
    }

    if (t.isProgram(node)) {
      const scope = pushTempScope(state, "module", "Module", {
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
      });
      scope.bindings.this = {
        type: "implicit",
        refs: [],
      };
    } else if (t.isFunction(node)) {
      let { scope } = state;

      if (t.isFunctionExpression(node) && isNode(node.id, "Identifier")) {
        scope = pushTempScope(state, "block", "Function Expression", {
          start: fromBabelLocation(node.loc.start, state.sourceId),
          end: fromBabelLocation(node.loc.end, state.sourceId),
        });
        state.declarationBindingIds.add(node.id);
        scope.bindings[node.id.name] = {
          type: "const",
          refs: [
            {
              type: "fn-expr",
              start: fromBabelLocation(node.id.loc.start, state.sourceId),
              end: fromBabelLocation(node.id.loc.end, state.sourceId),
              declaration: {
                start: fromBabelLocation(node.loc.start, state.sourceId),
                end: fromBabelLocation(node.loc.end, state.sourceId),
              },
            },
          ],
        };
      }

      if (t.isFunctionDeclaration(node) && isNode(node.id, "Identifier")) {
        // This ignores Annex B function declaration hoisting, which
        // is probably a fine assumption.
        state.declarationBindingIds.add(node.id);
        const refs = [
          {
            type: "fn-decl",
            start: fromBabelLocation(node.id.loc.start, state.sourceId),
            end: fromBabelLocation(node.id.loc.end, state.sourceId),
            declaration: {
              start: fromBabelLocation(node.loc.start, state.sourceId),
              end: fromBabelLocation(node.loc.end, state.sourceId),
            },
          },
        ];

        if (scope.type === "block") {
          scope.bindings[node.id.name] = {
            type: "let",
            refs,
          };
        } else {
          // Add the binding to the ancestor scope
          getVarScope(scope).bindings[node.id.name] = {
            type: "var",
            refs,
          };
        }
      }

      scope = pushTempScope(
        state,
        "function",
        getFunctionName(node, parentNode),
        {
          // Being at the start of a function doesn't count as
          // being inside of it.
          start: fromBabelLocation(
            node.params[0] ? node.params[0].loc.start : node.loc.start,
            state.sourceId
          ),
          end: fromBabelLocation(node.loc.end, state.sourceId),
        }
      );

      node.params.forEach(param =>
        parseDeclarator(param, scope, "var", "fn-param", node, state)
      );

      if (!t.isArrowFunctionExpression(node)) {
        scope.bindings.this = {
          type: "implicit",
          refs: [],
        };
        scope.bindings.arguments = {
          type: "implicit",
          refs: [],
        };
      }

      if (
        t.isBlockStatement(node.body) &&
        hasLexicalDeclaration(node.body, node)
      ) {
        scope = pushTempScope(state, "function-body", "Function Body", {
          start: fromBabelLocation(node.body.loc.start, state.sourceId),
          end: fromBabelLocation(node.body.loc.end, state.sourceId),
        });
      }
    } else if (t.isClass(node)) {
      if (t.isIdentifier(node.id)) {
        // For decorated classes, the AST considers the first the decorator
        // to be the start of the class. For the purposes of mapping class
        // declarations however, we really want to look for the "class Foo"
        // piece. To achieve that, we estimate the location of the declaration
        // instead.
        let declStart = node.loc.start;
        if (node.decorators && node.decorators.length) {
          // Estimate the location of the "class" keyword since it
          // is unlikely to be a different line than the class name.
          declStart = {
            line: node.id.loc.start.line,
            column: node.id.loc.start.column - "class ".length,
          };
        }

        const declaration = {
          start: fromBabelLocation(declStart, state.sourceId),
          end: fromBabelLocation(node.loc.end, state.sourceId),
        };

        if (t.isClassDeclaration(node)) {
          state.declarationBindingIds.add(node.id);
          state.scope.bindings[node.id.name] = {
            type: "let",
            refs: [
              {
                type: "class-decl",
                start: fromBabelLocation(node.id.loc.start, state.sourceId),
                end: fromBabelLocation(node.id.loc.end, state.sourceId),
                declaration,
              },
            ],
          };
        }

        const scope = pushTempScope(state, "block", "Class", {
          start: fromBabelLocation(node.loc.start, state.sourceId),
          end: fromBabelLocation(node.loc.end, state.sourceId),
        });

        state.declarationBindingIds.add(node.id);
        scope.bindings[node.id.name] = {
          type: "const",
          refs: [
            {
              type: "class-inner",
              start: fromBabelLocation(node.id.loc.start, state.sourceId),
              end: fromBabelLocation(node.id.loc.end, state.sourceId),
              declaration,
            },
          ],
        };
      }
    } else if (t.isForXStatement(node) || t.isForStatement(node)) {
      const init = node.init || node.left;
      if (isNode(init, "VariableDeclaration") && isLetOrConst(init)) {
        // Debugger will create new lexical environment for the for.
        pushTempScope(state, "block", "For", {
          // Being at the start of a for loop doesn't count as
          // being inside it.
          start: fromBabelLocation(init.loc.start, state.sourceId),
          end: fromBabelLocation(node.loc.end, state.sourceId),
        });
      }
    } else if (t.isCatchClause(node)) {
      const scope = pushTempScope(state, "block", "Catch", {
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
      });
      parseDeclarator(node.param, scope, "var", "catch", node, state);
    } else if (
      t.isBlockStatement(node) &&
      // Function body's are handled in the function logic above.
      !t.isFunction(parentNode) &&
      hasLexicalDeclaration(node, parentNode)
    ) {
      // Debugger will create new lexical environment for the block.
      pushTempScope(state, "block", "Block", {
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
      });
    } else if (
      t.isVariableDeclaration(node) &&
      (node.kind === "var" ||
        // Lexical declarations in for statements are handled above.
        !t.isForStatement(parentNode, { init: node }) ||
        !t.isForXStatement(parentNode, { left: node }))
    ) {
      // Finds right lexical environment
      const hoistAt = !isLetOrConst(node)
        ? getVarScope(state.scope)
        : state.scope;
      node.declarations.forEach(declarator => {
        parseDeclarator(
          declarator.id,
          hoistAt,
          node.kind,
          node.kind,
          node,
          state
        );
      });
    } else if (
      t.isImportDeclaration(node) &&
      (!node.importKind || node.importKind === "value")
    ) {
      node.specifiers.forEach(spec => {
        if (spec.importKind && spec.importKind !== "value") {
          return;
        }

        if (t.isImportNamespaceSpecifier(spec)) {
          state.declarationBindingIds.add(spec.local);

          state.scope.bindings[spec.local.name] = {
            // Imported namespaces aren't live import bindings, they are
            // just normal const bindings.
            type: "const",
            refs: [
              {
                type: "import-ns-decl",
                start: fromBabelLocation(spec.local.loc.start, state.sourceId),
                end: fromBabelLocation(spec.local.loc.end, state.sourceId),
                declaration: {
                  start: fromBabelLocation(node.loc.start, state.sourceId),
                  end: fromBabelLocation(node.loc.end, state.sourceId),
                },
              },
            ],
          };
        } else {
          state.declarationBindingIds.add(spec.local);

          state.scope.bindings[spec.local.name] = {
            type: "import",
            refs: [
              {
                type: "import-decl",
                start: fromBabelLocation(spec.local.loc.start, state.sourceId),
                end: fromBabelLocation(spec.local.loc.end, state.sourceId),
                importName: t.isImportDefaultSpecifier(spec)
                  ? "default"
                  : spec.imported.name,
                declaration: {
                  start: fromBabelLocation(node.loc.start, state.sourceId),
                  end: fromBabelLocation(node.loc.end, state.sourceId),
                },
              },
            ],
          };
        }
      });
    } else if (t.isTSEnumDeclaration(node)) {
      state.declarationBindingIds.add(node.id);
      state.scope.bindings[node.id.name] = {
        type: "const",
        refs: [
          {
            type: "ts-enum-decl",
            start: fromBabelLocation(node.id.loc.start, state.sourceId),
            end: fromBabelLocation(node.id.loc.end, state.sourceId),
            declaration: {
              start: fromBabelLocation(node.loc.start, state.sourceId),
              end: fromBabelLocation(node.loc.end, state.sourceId),
            },
          },
        ],
      };
    } else if (t.isTSModuleDeclaration(node)) {
      state.declarationBindingIds.add(node.id);
      state.scope.bindings[node.id.name] = {
        type: "const",
        refs: [
          {
            type: "ts-namespace-decl",
            start: fromBabelLocation(node.id.loc.start, state.sourceId),
            end: fromBabelLocation(node.id.loc.end, state.sourceId),
            declaration: {
              start: fromBabelLocation(node.loc.start, state.sourceId),
              end: fromBabelLocation(node.loc.end, state.sourceId),
            },
          },
        ],
      };
    } else if (t.isTSModuleBlock(node)) {
      pushTempScope(state, "block", "TypeScript Namespace", {
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
      });
    } else if (
      t.isIdentifier(node) &&
      t.isReferenced(node, parentNode) &&
      // Babel doesn't cover this in 'isReferenced' yet, but it should
      // eventually.
      !t.isTSEnumMember(parentNode, { id: node }) &&
      !t.isTSModuleDeclaration(parentNode, { id: node }) &&
      // isReferenced above fails to see `var { foo } = ...` as a non-reference
      // because the direct parent is not enough to know that the pattern is
      // used within a variable declaration.
      !state.declarationBindingIds.has(node)
    ) {
      let freeVariables = state.freeVariables.get(node.name);
      if (!freeVariables) {
        freeVariables = [];
        state.freeVariables.set(node.name, freeVariables);
      }

      freeVariables.push({
        type: "ref",
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
        meta: buildMetaBindings(state.sourceId, node, ancestors),
      });
    } else if (isOpeningJSXIdentifier(node, ancestors)) {
      let freeVariables = state.freeVariables.get(node.name);
      if (!freeVariables) {
        freeVariables = [];
        state.freeVariables.set(node.name, freeVariables);
      }

      freeVariables.push({
        type: "ref",
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
        meta: buildMetaBindings(state.sourceId, node, ancestors),
      });
    } else if (t.isThisExpression(node)) {
      let freeVariables = state.freeVariables.get("this");
      if (!freeVariables) {
        freeVariables = [];
        state.freeVariables.set("this", freeVariables);
      }

      freeVariables.push({
        type: "ref",
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
        meta: buildMetaBindings(state.sourceId, node, ancestors),
      });
    } else if (t.isClassProperty(parentNode, { value: node })) {
      const scope = pushTempScope(state, "function", "Class Field", {
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
      });
      scope.bindings.this = {
        type: "implicit",
        refs: [],
      };
      scope.bindings.arguments = {
        type: "implicit",
        refs: [],
      };
    } else if (
      t.isSwitchStatement(node) &&
      hasLexicalDeclaration(node, parentNode)
    ) {
      pushTempScope(state, "block", "Switch", {
        start: fromBabelLocation(node.loc.start, state.sourceId),
        end: fromBabelLocation(node.loc.end, state.sourceId),
      });
    }

    if (
      // In general Flow expressions are deleted, so they can't contain
      // runtime bindings, but typecasts are the one exception there.
      (t.isFlow(node) && !t.isTypeCastExpression(node)) ||
      // In general TS items are deleted, but TS has a few wrapper node
      // types that can contain general JS expressions.
      (node.type.startsWith("TS") &&
        !t.isTSTypeAssertion(node) &&
        !t.isTSAsExpression(node) &&
        !t.isTSNonNullExpression(node) &&
        !t.isTSModuleDeclaration(node) &&
        !t.isTSModuleBlock(node) &&
        !t.isTSParameterProperty(node) &&
        !t.isTSExportAssignment(node))
    ) {
      // Flag this node as a root "type" node. All items inside of this
      // will be skipped entirely.
      state.inType = node;
    }
  },
  exit(node, ancestors, state) {
    const currentScope = state.scope;
    const parentScope = state.scopeStack.pop();
    if (!parentScope) {
      throw new Error("Assertion failure - unsynchronized pop");
    }
    state.scope = parentScope;

    // It is possible, as in the case of function expressions, that a single
    // node has added multiple scopes, so we need to traverse upward here
    // rather than jumping stright to 'parentScope'.
    for (
      let scope = currentScope;
      scope && scope !== parentScope;
      scope = scope.parent
    ) {
      const { freeVariables } = state;
      state.freeVariables = state.freeVariableStack.pop();
      const parentFreeVariables = state.freeVariables;

      // Match up any free variables that match this scope's bindings and
      // merge then into the refs.
      for (const key of Object.keys(scope.bindings)) {
        const binding = scope.bindings[key];

        const freeVars = freeVariables.get(key);
        if (freeVars) {
          binding.refs.push(...freeVars);
          freeVariables.delete(key);
        }
      }

      // Move any undeclared references in this scope into the parent for
      // processing in higher scopes.
      for (const [key, value] of freeVariables) {
        let refs = parentFreeVariables.get(key);
        if (!refs) {
          refs = [];
          parentFreeVariables.set(key, refs);
        }

        refs.push(...value);
      }
    }

    if (state.inType === node) {
      state.inType = null;
    }
  },
};

function isOpeningJSXIdentifier(node, ancestors) {
  if (!t.isJSXIdentifier(node)) {
    return false;
  }

  for (let i = ancestors.length - 1; i >= 0; i--) {
    const { node: parent, key } = ancestors[i];

    if (t.isJSXOpeningElement(parent) && key === "name") {
      return true;
    } else if (!t.isJSXMemberExpression(parent) || key !== "object") {
      break;
    }
  }

  return false;
}

function buildMetaBindings(
  sourceId,
  node,
  ancestors,
  parentIndex = ancestors.length - 1
) {
  if (parentIndex <= 1) {
    return null;
  }
  const parent = ancestors[parentIndex].node;
  const grandparent = ancestors[parentIndex - 1].node;

  // Consider "0, foo" to be equivalent to "foo".
  if (
    t.isSequenceExpression(parent) &&
    parent.expressions.length === 2 &&
    t.isNumericLiteral(parent.expressions[0]) &&
    parent.expressions[1] === node
  ) {
    let { start, end } = parent.loc;

    if (t.isCallExpression(grandparent, { callee: parent })) {
      // Attempt to expand the range around parentheses, e.g.
      // (0, foo.bar)()
      start = grandparent.loc.start;
      end = Object.assign({}, end);
      end.column += 1;
    }

    return {
      type: "inherit",
      start: fromBabelLocation(start, sourceId),
      end: fromBabelLocation(end, sourceId),
      parent: buildMetaBindings(sourceId, parent, ancestors, parentIndex - 1),
    };
  }

  // Consider "Object(foo)", and "__webpack_require__.i(foo)" to be
  // equivalent to "foo" since they are essentially identity functions.
  if (
    t.isCallExpression(parent) &&
    (t.isIdentifier(parent.callee, { name: "Object" }) ||
      (t.isMemberExpression(parent.callee, { computed: false }) &&
        t.isIdentifier(parent.callee.object, { name: "__webpack_require__" }) &&
        t.isIdentifier(parent.callee.property, { name: "i" }))) &&
    parent.arguments.length === 1 &&
    parent.arguments[0] === node
  ) {
    return {
      type: "inherit",
      start: fromBabelLocation(parent.loc.start, sourceId),
      end: fromBabelLocation(parent.loc.end, sourceId),
      parent: buildMetaBindings(sourceId, parent, ancestors, parentIndex - 1),
    };
  }

  if (t.isMemberExpression(parent, { object: node })) {
    if (parent.computed) {
      if (t.isStringLiteral(parent.property)) {
        return {
          type: "member",
          start: fromBabelLocation(parent.loc.start, sourceId),
          end: fromBabelLocation(parent.loc.end, sourceId),
          property: parent.property.value,
          parent: buildMetaBindings(
            sourceId,
            parent,
            ancestors,
            parentIndex - 1
          ),
        };
      }
    } else {
      return {
        type: "member",
        start: fromBabelLocation(parent.loc.start, sourceId),
        end: fromBabelLocation(parent.loc.end, sourceId),
        property: parent.property.name,
        parent: buildMetaBindings(sourceId, parent, ancestors, parentIndex - 1),
      };
    }
  }
  if (
    t.isCallExpression(parent, { callee: node }) &&
    !parent.arguments.length
  ) {
    return {
      type: "call",
      start: fromBabelLocation(parent.loc.start, sourceId),
      end: fromBabelLocation(parent.loc.end, sourceId),
      parent: buildMetaBindings(sourceId, parent, ancestors, parentIndex - 1),
    };
  }

  return null;
}

function looksLikeCommonJS(rootScope) {
  const hasRefs = name =>
    rootScope.bindings[name] && !!rootScope.bindings[name].refs.length;

  return (
    hasRefs("__dirname") ||
    hasRefs("__filename") ||
    hasRefs("require") ||
    hasRefs("exports") ||
    hasRefs("module")
  );
}

function stripModuleScope(rootScope) {
  const rootLexicalScope = rootScope.children[0];
  const moduleScope = rootLexicalScope.children[0];
  if (moduleScope.type !== "module") {
    throw new Error("Assertion failure - should be module");
  }

  Object.keys(moduleScope.bindings).forEach(name => {
    const binding = moduleScope.bindings[name];
    if (binding.type === "let" || binding.type === "const") {
      rootLexicalScope.bindings[name] = binding;
    } else {
      rootScope.bindings[name] = binding;
    }
  });
  rootLexicalScope.children = moduleScope.children;
  rootLexicalScope.children.forEach(child => {
    child.parent = rootLexicalScope;
  });
}