/**
 * @fileoverview Rule to flag dangling underscores in variable declarations.
 * @author Matt DuVall <http://www.mattduvall.com>
 */

'use strict';

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
  meta: {
    type: 'suggestion',

    defaultOptions: [
      {
        allow: [],
        allowAfterSuper: false,
        allowAfterThis: false,
        allowAfterThisConstructor: false,
        allowFunctionParams: true,
        allowInArrayDestructuring: true,
        allowInObjectDestructuring: true,
        enforceInClassFields: false,
        enforceInMethodNames: false,
      },
    ],

    docs: {
      description: 'Disallow dangling underscores in identifiers',
      recommended: false,
      frozen: true,
      url: 'https://eslint.org/docs/latest/rules/no-underscore-dangle',
    },

    schema: [
      {
        type: 'object',
        properties: {
          allow: {
            type: 'array',
            items: {
              type: 'string',
            },
          },
          allowAfterThis: {
            type: 'boolean',
          },
          allowAfterSuper: {
            type: 'boolean',
          },
          allowAfterThisConstructor: {
            type: 'boolean',
          },
          enforceInMethodNames: {
            type: 'boolean',
          },
          allowFunctionParams: {
            type: 'boolean',
          },
          enforceInClassFields: {
            type: 'boolean',
          },
          allowInArrayDestructuring: {
            type: 'boolean',
          },
          allowInObjectDestructuring: {
            type: 'boolean',
          },
        },
        additionalProperties: false,
      },
    ],

    messages: {
      unexpectedUnderscore: "Unexpected dangling '_' in '{{identifier}}'.",
    },
  },

  create(context) {
    const [
      {
        allow,
        allowAfterSuper,
        allowAfterThis,
        allowAfterThisConstructor,
        allowFunctionParams,
        allowInArrayDestructuring,
        allowInObjectDestructuring,
        enforceInClassFields,
        enforceInMethodNames,
      },
    ] = context.options;
    const sourceCode = context.sourceCode;

    //-------------------------------------------------------------------------
    // Helpers
    //-------------------------------------------------------------------------

    /**
     * Check if identifier is present inside the allowed option
     * @param {string} identifier name of the node
     * @returns {boolean} true if its is present
     * @private
     */
    function isAllowed(identifier) {
      return allow.includes(identifier);
    }

    /**
     * Check if identifier has a dangling underscore
     * @param {string} identifier name of the node
     * @returns {boolean} true if its is present
     * @private
     */
    function hasDanglingUnderscore(identifier) {
      const len = identifier.length;

      return (
        identifier !== '_' &&
        (identifier[0] === '_' || identifier[len - 1] === '_')
      );
    }

    /**
     * Check if identifier is a special case member expression
     * @param {string} identifier name of the node
     * @returns {boolean} true if its is a special case
     * @private
     */
    function isSpecialCaseIdentifierForMemberExpression(identifier) {
      return identifier === '__proto__';
    }

    /**
     * Check if identifier is a special case variable expression
     * @param {string} identifier name of the node
     * @returns {boolean} true if its is a special case
     * @private
     */
    function isSpecialCaseIdentifierInVariableExpression(identifier) {
      // Checks for the underscore library usage here
      return identifier === '_';
    }

    /**
     * Check if a node is a member reference of this.constructor
     * @param {ASTNode} node node to evaluate
     * @returns {boolean} true if it is a reference on this.constructor
     * @private
     */
    function isThisConstructorReference(node) {
      return (
        node.object.type === 'MemberExpression' &&
        node.object.property.name === 'constructor' &&
        node.object.object.type === 'ThisExpression'
      );
    }

    /**
     * Check if function parameter has a dangling underscore.
     * @param {ASTNode} node function node to evaluate
     * @returns {void}
     * @private
     */
    function checkForDanglingUnderscoreInFunctionParameters(node) {
      if (!allowFunctionParams) {
        node.params.forEach((param) => {
          const { type } = param;
          let nodeToCheck;

          if (type === 'RestElement') {
            nodeToCheck = param.argument;
          } else if (type === 'AssignmentPattern') {
            nodeToCheck = param.left;
          } else {
            nodeToCheck = param;
          }

          if (nodeToCheck.type === 'Identifier') {
            const identifier = nodeToCheck.name;

            if (hasDanglingUnderscore(identifier) && !isAllowed(identifier)) {
              context.report({
                node: param,
                messageId: 'unexpectedUnderscore',
                data: {
                  identifier,
                },
              });
            }
          }
        });
      }
    }

    /**
     * Check if function has a dangling underscore
     * @param {ASTNode} node node to evaluate
     * @returns {void}
     * @private
     */
    function checkForDanglingUnderscoreInFunction(node) {
      if (node.type === 'FunctionDeclaration' && node.id) {
        const identifier = node.id.name;

        if (
          typeof identifier !== 'undefined' &&
          hasDanglingUnderscore(identifier) &&
          !isAllowed(identifier)
        ) {
          context.report({
            node,
            messageId: 'unexpectedUnderscore',
            data: {
              identifier,
            },
          });
        }
      }
      checkForDanglingUnderscoreInFunctionParameters(node);
    }

    /**
     * Check if variable expression has a dangling underscore
     * @param {ASTNode} node node to evaluate
     * @returns {void}
     * @private
     */
    function checkForDanglingUnderscoreInVariableExpression(node) {
      sourceCode.getDeclaredVariables(node).forEach((variable) => {
        const definition = variable.defs.find((def) => def.node === node);
        const identifierNode = definition.name;
        const identifier = identifierNode.name;
        let parent = identifierNode.parent;

        while (
          !['VariableDeclarator', 'ArrayPattern', 'ObjectPattern'].includes(
            parent.type
          )
        ) {
          parent = parent.parent;
        }

        if (
          hasDanglingUnderscore(identifier) &&
          !isSpecialCaseIdentifierInVariableExpression(identifier) &&
          !isAllowed(identifier) &&
          !(allowInArrayDestructuring && parent.type === 'ArrayPattern') &&
          !(allowInObjectDestructuring && parent.type === 'ObjectPattern')
        ) {
          context.report({
            node,
            messageId: 'unexpectedUnderscore',
            data: {
              identifier,
            },
          });
        }
      });
    }

    /**
     * Check if member expression has a dangling underscore
     * @param {ASTNode} node node to evaluate
     * @returns {void}
     * @private
     */
    function checkForDanglingUnderscoreInMemberExpression(node) {
      const identifier = node.property.name,
        isMemberOfThis = node.object.type === 'ThisExpression',
        isMemberOfSuper = node.object.type === 'Super',
        isMemberOfThisConstructor = isThisConstructorReference(node);

      if (
        typeof identifier !== 'undefined' &&
        hasDanglingUnderscore(identifier) &&
        !(isMemberOfThis && allowAfterThis) &&
        !(isMemberOfSuper && allowAfterSuper) &&
        !(isMemberOfThisConstructor && allowAfterThisConstructor) &&
        !isSpecialCaseIdentifierForMemberExpression(identifier) &&
        !isAllowed(identifier)
      ) {
        context.report({
          node,
          messageId: 'unexpectedUnderscore',
          data: {
            identifier,
          },
        });
      }
    }

    /**
     * Check if method declaration or method property has a dangling underscore
     * @param {ASTNode} node node to evaluate
     * @returns {void}
     * @private
     */
    function checkForDanglingUnderscoreInMethod(node) {
      const identifier = node.key.name;
      const isMethod =
        node.type === 'MethodDefinition' ||
        (node.type === 'Property' && node.method);

      if (
        typeof identifier !== 'undefined' &&
        enforceInMethodNames &&
        isMethod &&
        hasDanglingUnderscore(identifier) &&
        !isAllowed(identifier)
      ) {
        context.report({
          node,
          messageId: 'unexpectedUnderscore',
          data: {
            identifier:
              node.key.type === 'PrivateIdentifier' ?
                `#${identifier}`
              : identifier,
          },
        });
      }
    }

    /**
     * Check if a class field has a dangling underscore
     * @param {ASTNode} node node to evaluate
     * @returns {void}
     * @private
     */
    function checkForDanglingUnderscoreInClassField(node) {
      const identifier = node.key.name;

      if (
        typeof identifier !== 'undefined' &&
        hasDanglingUnderscore(identifier) &&
        enforceInClassFields &&
        !isAllowed(identifier)
      ) {
        context.report({
          node,
          messageId: 'unexpectedUnderscore',
          data: {
            identifier:
              node.key.type === 'PrivateIdentifier' ?
                `#${identifier}`
              : identifier,
          },
        });
      }
    }

    //--------------------------------------------------------------------------
    // Public API
    //--------------------------------------------------------------------------

    return {
      FunctionDeclaration: checkForDanglingUnderscoreInFunction,
      VariableDeclarator: checkForDanglingUnderscoreInVariableExpression,
      MemberExpression: checkForDanglingUnderscoreInMemberExpression,
      MethodDefinition: checkForDanglingUnderscoreInMethod,
      PropertyDefinition: checkForDanglingUnderscoreInClassField,
      Property: checkForDanglingUnderscoreInMethod,
      FunctionExpression: checkForDanglingUnderscoreInFunction,
      ArrowFunctionExpression: checkForDanglingUnderscoreInFunction,
    };
  },
};