/**
 * @fileoverview Rule to disallow Math.pow in favor of the ** operator
 * @author Milos Djermanovic
 */

'use strict';

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const astUtils = require('./utils/ast-utils');
const { CALL, ReferenceTracker } = require('@eslint-community/eslint-utils');

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

const PRECEDENCE_OF_EXPONENTIATION_EXPR = astUtils.getPrecedence({
  type: 'BinaryExpression',
  operator: '**',
});

/**
 * Determines whether the given node needs parens if used as the base in an exponentiation binary expression.
 * @param {ASTNode} base The node to check.
 * @returns {boolean} `true` if the node needs to be parenthesised.
 */
function doesBaseNeedParens(base) {
  return (
    // '**' is right-associative, parens are needed when Math.pow(a ** b, c) is converted to (a ** b) ** c
    astUtils.getPrecedence(base) <= PRECEDENCE_OF_EXPONENTIATION_EXPR ||
    // An unary operator cannot be used immediately before an exponentiation expression
    base.type === 'AwaitExpression' ||
    base.type === 'UnaryExpression'
  );
}

/**
 * Determines whether the given node needs parens if used as the exponent in an exponentiation binary expression.
 * @param {ASTNode} exponent The node to check.
 * @returns {boolean} `true` if the node needs to be parenthesised.
 */
function doesExponentNeedParens(exponent) {
  // '**' is right-associative, there is no need for parens when Math.pow(a, b ** c) is converted to a ** b ** c
  return astUtils.getPrecedence(exponent) < PRECEDENCE_OF_EXPONENTIATION_EXPR;
}

/**
 * Determines whether an exponentiation binary expression at the place of the given node would need parens.
 * @param {ASTNode} node A node that would be replaced by an exponentiation binary expression.
 * @param {SourceCode} sourceCode A SourceCode object.
 * @returns {boolean} `true` if the expression needs to be parenthesised.
 */
function doesExponentiationExpressionNeedParens(node, sourceCode) {
  const parent =
    node.parent.type === 'ChainExpression' ? node.parent.parent : node.parent;

  const parentPrecedence = astUtils.getPrecedence(parent);
  const needsParens =
    parent.type === 'ClassDeclaration' ||
    (parent.type.endsWith('Expression') &&
      (parentPrecedence === -1 ||
        parentPrecedence >= PRECEDENCE_OF_EXPONENTIATION_EXPR) &&
      !(
        parent.type === 'BinaryExpression' &&
        parent.operator === '**' &&
        parent.right === node
      ) &&
      !(
        (parent.type === 'CallExpression' || parent.type === 'NewExpression') &&
        parent.arguments.includes(node)
      ) &&
      !(
        parent.type === 'MemberExpression' &&
        parent.computed &&
        parent.property === node
      ) &&
      !(parent.type === 'ArrayExpression'));

  return needsParens && !astUtils.isParenthesised(sourceCode, node);
}

/**
 * Optionally parenthesizes given text.
 * @param {string} text The text to parenthesize.
 * @param {boolean} shouldParenthesize If `true`, the text will be parenthesised.
 * @returns {string} parenthesised or unchanged text.
 */
function parenthesizeIfShould(text, shouldParenthesize) {
  return shouldParenthesize ? `(${text})` : text;
}

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

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

    docs: {
      description:
        'Disallow the use of `Math.pow` in favor of the `**` operator',
      recommended: false,
      frozen: true,
      url: 'https://eslint.org/docs/latest/rules/prefer-exponentiation-operator',
    },

    schema: [],
    fixable: 'code',

    messages: {
      useExponentiation: "Use the '**' operator instead of 'Math.pow'.",
    },
  },

  create(context) {
    const sourceCode = context.sourceCode;

    /**
     * Reports the given node.
     * @param {ASTNode} node 'Math.pow()' node to report.
     * @returns {void}
     */
    function report(node) {
      context.report({
        node,
        messageId: 'useExponentiation',
        fix(fixer) {
          if (
            node.arguments.length !== 2 ||
            node.arguments.some((arg) => arg.type === 'SpreadElement') ||
            sourceCode.getCommentsInside(node).length > 0
          ) {
            return null;
          }

          const base = node.arguments[0],
            exponent = node.arguments[1],
            baseText = sourceCode.getText(base),
            exponentText = sourceCode.getText(exponent),
            shouldParenthesizeBase = doesBaseNeedParens(base),
            shouldParenthesizeExponent = doesExponentNeedParens(exponent),
            shouldParenthesizeAll = doesExponentiationExpressionNeedParens(
              node,
              sourceCode
            );

          let prefix = '',
            suffix = '';

          if (!shouldParenthesizeAll) {
            if (!shouldParenthesizeBase) {
              const firstReplacementToken = sourceCode.getFirstToken(base),
                tokenBefore = sourceCode.getTokenBefore(node);

              if (
                tokenBefore &&
                tokenBefore.range[1] === node.range[0] &&
                !astUtils.canTokensBeAdjacent(
                  tokenBefore,
                  firstReplacementToken
                )
              ) {
                prefix = ' '; // a+Math.pow(++b, c) -> a+ ++b**c
              }
            }
            if (!shouldParenthesizeExponent) {
              const lastReplacementToken = sourceCode.getLastToken(exponent),
                tokenAfter = sourceCode.getTokenAfter(node);

              if (
                tokenAfter &&
                node.range[1] === tokenAfter.range[0] &&
                !astUtils.canTokensBeAdjacent(lastReplacementToken, tokenAfter)
              ) {
                suffix = ' '; // Math.pow(a, b)in c -> a**b in c
              }
            }
          }

          const baseReplacement = parenthesizeIfShould(
              baseText,
              shouldParenthesizeBase
            ),
            exponentReplacement = parenthesizeIfShould(
              exponentText,
              shouldParenthesizeExponent
            ),
            replacement = parenthesizeIfShould(
              `${baseReplacement}**${exponentReplacement}`,
              shouldParenthesizeAll
            );

          return fixer.replaceText(node, `${prefix}${replacement}${suffix}`);
        },
      });
    }

    return {
      Program(node) {
        const scope = sourceCode.getScope(node);
        const tracker = new ReferenceTracker(scope);
        const trackMap = {
          Math: {
            pow: { [CALL]: true },
          },
        };

        for (const { node: refNode } of tracker.iterateGlobalReferences(
          trackMap
        )) {
          report(refNode);
        }
      },
    };
  },
};