newline-after-import.js

/**
 * @fileoverview Rule to enforce new line after import not followed by another import.
 * @author Radek Benkel
 */

import isStaticRequire from '../core/staticRequire'
import docsUrl from '../docsUrl'

import debug from 'debug'
const log = debug('eslint-plugin-import:rules:newline-after-import')

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

function containsNodeOrEqual(outerNode, innerNode) {
    return outerNode.range[0] <= innerNode.range[0] && outerNode.range[1] >= innerNode.range[1]
}

function getScopeBody(scope) {
    if (scope.block.type === 'SwitchStatement') {
      log('SwitchStatement scopes not supported')
      return null
    }

    const { body } = scope.block
    if (body && body.type === 'BlockStatement') {
        return body.body
    }

    return body
}

function findNodeIndexInScopeBody(body, nodeToFind) {
    return body.findIndex((node) => containsNodeOrEqual(node, nodeToFind))
}

function getLineDifference(node, nextNode) {
  return nextNode.loc.start.line - node.loc.end.line
}

function isClassWithDecorator(node) {
  return node.type === 'ClassDeclaration' && node.decorators && node.decorators.length
}

module.exports = {
  meta: {
    type: 'layout',
    docs: {
      url: docsUrl('newline-after-import'),
    },
    schema: [
      {
        'type': 'object',
        'properties': {
          'count': {
            'type': 'integer',
            'minimum': 1,
          },
        },
        'additionalProperties': false,
      },
    ],
    fixable: 'whitespace',
  },
  create: function (context) {
    let level = 0
    const requireCalls = []

    function checkForNewLine(node, nextNode, type) {
      if (isClassWithDecorator(nextNode)) {
        nextNode = nextNode.decorators[0]
      }

      const options = context.options[0] || { count: 1 }
      const lineDifference = getLineDifference(node, nextNode)
      const EXPECTED_LINE_DIFFERENCE = options.count + 1

      if (lineDifference < EXPECTED_LINE_DIFFERENCE) {
        let column = node.loc.start.column

        if (node.loc.start.line !== node.loc.end.line) {
          column = 0
        }

        context.report({
          loc: {
            line: node.loc.end.line,
            column,
          },
          message: `Expected ${options.count} empty line${options.count > 1 ? 's' : ''} \
after ${type} statement not followed by another ${type}.`,
          fix: fixer => fixer.insertTextAfter(
            node,
            '\n'.repeat(EXPECTED_LINE_DIFFERENCE - lineDifference)
          ),
        })
      }
    }

    function incrementLevel() {
      level++
    }
    function decrementLevel() {
      level--
    }

    return {
      ImportDeclaration: function (node) {
        const { parent } = node
        const nodePosition = parent.body.indexOf(node)
        const nextNode = parent.body[nodePosition + 1]

        if (nextNode && nextNode.type !== 'ImportDeclaration') {
          checkForNewLine(node, nextNode, 'import')
        }
      },
      CallExpression: function(node) {
        if (isStaticRequire(node) && level === 0) {
          requireCalls.push(node)
        }
      },
      'Program:exit': function () {
        log('exit processing for', context.getFilename())
        const scopeBody = getScopeBody(context.getScope())
        log('got scope:', scopeBody)

        requireCalls.forEach(function (node, index) {
          const nodePosition = findNodeIndexInScopeBody(scopeBody, node)
          log('node position in scope:', nodePosition)

          const statementWithRequireCall = scopeBody[nodePosition]
          const nextStatement = scopeBody[nodePosition + 1]
          const nextRequireCall = requireCalls[index + 1]

          if (nextRequireCall && containsNodeOrEqual(statementWithRequireCall, nextRequireCall)) {
            return
          }

          if (nextStatement &&
             (!nextRequireCall || !containsNodeOrEqual(nextStatement, nextRequireCall))) {

            checkForNewLine(statementWithRequireCall, nextStatement, 'require')
          }
        })
      },
      FunctionDeclaration: incrementLevel,
      FunctionExpression: incrementLevel,
      ArrowFunctionExpression: incrementLevel,
      BlockStatement: incrementLevel,
      ObjectExpression: incrementLevel,
      Decorator: incrementLevel,
      'FunctionDeclaration:exit': decrementLevel,
      'FunctionExpression:exit': decrementLevel,
      'ArrowFunctionExpression:exit': decrementLevel,
      'BlockStatement:exit': decrementLevel,
      'ObjectExpression:exit': decrementLevel,
      'Decorator:exit': decrementLevel,
    }
  },
}