plugins:
  - compat
  - import
  - react
  - unicorn
  - flowtype
  - jsx-a11y
  - promise
  - no-use-extend-native
  - filenames
  - lodash
  - node
  - flowtype-errors

extends:
  - eslint:recommended
  - plugin:react/recommended
  - plugin:unicorn/recommended
  - plugin:import/errors
  - plugin:import/warnings
  - plugin:lodash/recommended
  - plugin:node/recommended

env:
  browser: true
  node: true
  es6: true
  jest: true
  worker: true
  serviceworker: true

installedESLint: true

parserOptions:
  ecmaVersion: 2017
  ecmaFeatures:
    experimentalObjectRestSpread: true
    generators: true
    jsx: true
  sourceType: module

rules:
  #######################################################################################
  # Basics
  #######################################################################################

  indent:
    - error
    - 2
    - SwitchCase: 1
      VariableDeclarator: 1
      outerIIFEBody: 0
      MemberExpression: 1
      FunctionExpression:
        body: 1
        parameters: 1
      CallExpression:
        arguments: 1
  linebreak-style:
    - error
    - unix
  quotes:
    - error
    - double
    - avoidEscape: true
      allowTemplateLiterals: true
  semi:
    - error
    - never
  no-console:
    - off
  no-extra-parens:
    - off
  class-methods-use-this:
    - warn
    - exceptMethods:
        - componentWillMount
        - componentDidMount
        - componentWillReceiveProps
        - shouldComponentUpdate
        - componentWillUpdate
        - componentDidUpdate
        - componentWillUnmount
  func-call-spacing: error

  # Tolerating both: 1tbs and allman - it's not really that relevant as long
  # as overall indenting is correct
  brace-style:
    - off

  comma-dangle:
    - error
    - never


  #######################################################################################
  # Code Quality
  #######################################################################################

  array-callback-return:
    - error
  block-scoped-var:
    - off

  # Keeping complexity down. The default of 20 is far to high in my opinion.
  complexity:
    - error
    - 10
  consistent-return: error

  # Allo using curly braces or not (e.g. for simple if-statements)
  curly:
    - off

  default-case:
    - error
  dot-location:
    - error
    - property
  dot-notation:
    - error
    - allowKeywords: true

  # Smart option allows simple equal for null-comparison which is good
  eqeqeq:
    - error
    - smart
  no-alert: error

  # Was mainly relevant while people extended Object.prototype.xxx
  guard-for-in:
    - off

  # Match ES5 strict
  no-caller: error

  # Hard to read code must be forbidden
  no-div-regex: error

  # Prefer what ever the developer thinks make code more readable/understandable
  no-else-return:
    - off

  no-empty-function:
    - error
  no-empty-pattern: error

  # This is just stupid
  no-eq-null:
    - off

  no-eval:
    - error
  no-extend-native:
    - error
  no-fallthrough:
    - error
  no-floating-decimal: error

  # I like some of these, but numbers are to awkward for me.
  no-implicit-coercion:
    - error
    - boolean: true
      string: true
      number: false

  # Does not make sense with ES6 modules
  no-implicit-globals:
    - off

  no-implied-eval:
    - error
  no-invalid-this:
    - error
  no-iterator:
    - error
  no-lone-blocks: error

  # Good style
  no-magic-numbers:
    - error
    - ignoreArrayIndexes: true
      ignore: [ -1, 0, 1, 2, 10, 16, 100, 1000 ]

  no-mixed-operators:
    - error
    - groups:
      - ['&', '|', '^', '~', '<<', '>>', '>>>']
      - ['==', '!=', '===', '!==', '>', '>=', '<', '<=']
      - ['&&', '||']
      - ['in', 'instanceof']
      allowSamePrecedence: false

  # Useless formatting with high maintenance
  no-multi-spaces: error

  no-multi-str:
    - error
  no-native-reassign:
    - error
  no-new-func:
    - error
  no-new-wrappers:
    - error
  no-octal:
    - error
  no-octal-escape: error

  valid-typeof: error

  # Disable direct init: new require("app-header")
  no-new-require: error

  # Use path.join/resolve instead
  no-path-concat: error

  # disallow certain object properties
  # http://eslint.org/docs/rules/no-restricted-properties
  no-restricted-properties:
    - error
    - object: 'arguments'
      property: callee
      message: arguments.callee is deprecated
    - property: __defineGetter__
      message: 'Please use Object.defineProperty instead.'
    - property: __defineSetter__
      message: 'Please use Object.defineProperty instead.'
    - object: Math
      property: pow
      message: 'Use the exponentiation operator (**) instead.'

  # Prevent side effects to arguments objects, but also makes code sometimes more complexer
  # when you have some logic in place to deal with different argument sets.
  # Still with ES6 default arguments and destructing params it's easier solvable today than in the past.
  no-param-reassign: error

  # Access NodeJS environment. Used mostly for code variations e.g. `NODE_ENV`
  no-process-env:
    - off

  # Deprecated feature
  no-proto: error

  # Disabled. Therefor they are variables, right?
  no-redeclare:
    - off

  # Readability wins
  no-return-assign: error

  no-script-url:
    - error
  no-self-assign:
    - error
  no-self-compare: error

  # Omit magic syntax... Readability for all wins
  no-sequences: error

  # Good idea to keep some more error info:
  # "The fundamental benefit of Error objects is that they automatically keep track of where they were built and originated."
  no-throw-literal: error

  no-unmodified-loop-condition:
    - error
  no-unused-expressions:
    - error
    - allowTernary: true
      allowShortCircuit: true
  no-useless-call:
    - error
  no-useless-concat:
    - error
  no-useless-computed-key:
    - error
  no-useless-constructor:
    - error
  no-useless-escape:
    - error
  no-useless-rename:
    - error
    - ignoreDestructuring: false
      ignoreImport: false
      ignoreExport: false

  no-void:
    - error
  no-with: error

  # Mainly for securing code compatibility
  radix:
    - error
    - always

  # Does not improve maintainability in my opinion... instead makes
  # unused variables harder to track over time
  vars-on-top:
    - off

  # Prefer inside for readability
  wrap-iife:
    - error
    - inside

  # Actually interesting that this ugliness should be even something to consider
  yoda:
    - error
    - never

  # Enforce strict mode globally which also happens during bundling
  strict:
    - error
    - global

  # Only relevant in IE8 and earlier. Would not allow to use the same error variable in
  # the same scope. Still no good practice for understanding the code.
  no-catch-shadow: error

  # For better maintainability
  no-shadow: error

  # Cleaner code
  no-shadow-restricted-names: error

  no-sparse-arrays: error

  no-this-before-super: error

  # Stupid idea which needs to be prevented
  no-undef-init: error

  # I sometimes like using it to differentiate between null and undefined
  no-undefined:
    - off

  no-unexpected-multiline: error

  no-unreachable: error

  no-unused-vars:
    - error
    - varsIgnorePattern: '^_'
      args: none
  no-use-before-define:
    - error
    - functions: false
      classes: false


  #################################################################
  # Stylistic
  #################################################################

  array-bracket-spacing:
    - error
    - always
    - objectsInArrays: false

  block-spacing:
    - error
    - always

  # See also: https://en.wikipedia.org/wiki/Indent_style
  # brace-style:
  #  - error
  #  - 1tbs

  camelcase: error

  comma-spacing:
    - error
    - before: false
      after: true

  comma-style:
    - error
    - last

  computed-property-spacing:
    - error
    - never

  consistent-this:
    - error
    - self

  eol-last: error

  # Useful for debugging in older browsers, but a lot of work to manually add everywhere
  func-names:
    - off

  jsx-quotes:
    - error
    - prefer-double

  max-lines:
    - warn
    - skipBlankLines: true
      skipComments: true
      max: 250

  # Prefering declaration
  func-style:
    - error
    - declaration
    - allowArrowFunctions: true

  max-statements-per-line:
    - error
    - max: 2

  id-length:
    - error
    - min: 4
      max: 40
      # 'i' + 'l' = typical looping constructs
      # 't' = support convention in ava test runner
      # 'fs' = built-in fs module
      exceptions: ["i", "l", "t", "id", "fs", "url", "uri", "key", "obj", "pos", "row", "col", "map", "min", "max"]
      properties: never

  # Makes sense in NodeJS for native methods but is flawed because it is based purely on the
  # naming and marks errors for a lot of user written UI code.
  no-sync:
    - off

  lines-around-directive:
    - error

  key-spacing:
    - error
    - beforeColon: false
      afterColon: true
      mode: strict

  keyword-spacing: error

  lines-around-comment:
    - error
    - beforeBlockComment: true
      afterBlockComment: false
      beforeLineComment: true
      afterLineComment: false
      allowBlockStart: true
      allowBlockEnd: false
      allowObjectStart: true
      allowObjectEnd: false
      allowArrayStart: true
      allowArrayEnd: false

  max-depth:
    - error
    - maximum: 3

  max-len:
    - error
    - code: 140
      comments: 160
      ignoreUrls: true
      tabWidth: 2

  max-nested-callbacks:
    - error
    - 3

  max-params:
    - error
    - 3

  max-statements:
    - error
    - 25
    - ignoreTopLevelFunctions: true

  new-cap:
    - error
    - capIsNew: false

  new-parens: error

  # It good to have newlines when declaring a block of variables, but not for just one
  # where we directly have some actionable stuff afterwards.
  newline-after-var:
    - off

  # Increase readability, but does not work everywhere... therefor we keep it off
  # and let the individual developer decide.
  newline-before-return: off
  newline-per-chained-call: off

  no-array-constructor: error

  # Generally prevents errors + rule can be disabled locally when required
  no-bitwise: error

  # Don't see why this is regarded as problematic
  no-continue: off
  no-control-regex: error
  no-delete-var: error

  no-dupe-args: error
  no-dupe-keys: error
  no-duplicate-case: error
  no-empty-character-class: error
  no-ex-assign: error
  no-extra-bind: error
  no-extra-label: error
  no-func-assign: error
  no-invalid-regexp: error
  no-label-var: error
  no-labels:
    - error
    - allowLoop: false
      allowSwitch: false

  # Leads to complexer to overlook code
  no-inline-comments: error

  # Might be used to improve code for human logic
  no-lonely-if: off

  no-multiple-empty-lines:
    - error
    - max: 4
      maxEOF: 1
      maxBOF: 0

  # Can help, but also can make code more complex/unnaturally structured
  no-negated-condition: off
  no-nested-ternary: error
  no-new-object: error
  no-obj-calls: error

  # Seems to be a new trend to omit this e.g. in Swift and other modern languages
  # But is pretty convenient in classic for-loops... therefor we allow it there
  no-plusplus:
    - error
    - allowForLoopAfterthoughts: true

  object-property-newline:
    - error
    - allowMultiplePropertiesPerLine: true

  no-confusing-arrow: error

  no-duplicate-imports: error

  no-new-symbol: error

  object-shorthand:
    - error
    - always
    - ignoreConstructors: true
      avoidQuotes: true

  no-restricted-syntax:
    - error
    - WithStatement
    - DebuggerStatement
    - LabeledStatement

  no-spaced-func: error

  no-ternary:
    - off

  # Lead to harder to diff changesets
  no-trailing-spaces: error

  no-underscore-dangle: off

  # Getting people to senior level...
  no-unneeded-ternary: error

  no-whitespace-before-property: error

  object-curly-spacing:
    - error
    - always

  one-var:
    - error
    - initialized: never

  one-var-declaration-per-line:
    - error
    - initializations

  operator-assignment: error

  operator-linebreak:
    - error
    - after

  rest-spread-spacing:
    - error
    - never

  unicode-bom:
    - error
    - never

  use-isnan: error

  # Not needed with Alman style. Interestingly deals with the same issue in a different way.
  padded-blocks:
    - error
    - never

  # That's a neat little setting for keeping code readable
  quote-props:
    - error
    - consistent-as-needed

  semi-spacing:
    - error
    - after: true
      before: false

  # Variables and Imports should be sorted in semantic groups not by name
  sort-imports:
    - off
  sort-vars:
    - off

  # Keeping things readable
  space-before-blocks:
    - error
    - always

  # Parens belong to the function... a spacing could break easy grasping of the code
  space-before-function-paren:
    - error
    - never

  space-in-parens:
    - error
    - never

  space-infix-ops: error

  space-unary-ops:
    - error
    - words: true
      nonwords: false

  spaced-comment:
    - error
    - always

  # I like the improved readability when using parens
  wrap-regex: error

  no-negated-in-lhs: error
  no-regex-spaces: error
  no-template-curly-in-string: error
  no-undef: error
  no-unused-labels: error
  require-yield: error

  #################################################################
  # ES6+
  #################################################################

  # Call me old fashioned
  arrow-body-style:
    - error
    - as-needed
  arrow-parens:
    - error
    - always

  arrow-spacing: error

  constructor-super: error

  # The star is no operator but a modifier of the function
  generator-star-spacing:
    - error
    - before

  no-class-assign: error

  no-prototype-builtins: error

  no-loop-func: error

  no-const-assign: error

  no-dupe-class-members: error

  # Trying to start new code the modern way - at least for what it makes sense
  prefer-arrow-callback:
    - error
  prefer-rest-params:
    - error
  prefer-spread:
    - error
  prefer-template: error


  #######################################################################################
  # Compat Plugin
  #######################################################################################

  compat/compat: warn


  #######################################################################################
  # Import Plugin
  #######################################################################################

  # Loader syntax is useful when loading files with alternative approaches e.g.
  # to detect images sizes, generating API docs, etc.
  import/no-webpack-loader-syntax: off

  import/no-absolute-path: error
  import/no-namespace: error
  import/no-commonjs: error
  import/no-amd: error


  #######################################################################################
  # React Plugin
  #######################################################################################

  react/jsx-no-undef:
    - error
  react/jsx-pascal-case:
    - error
    - allowAllCaps: true
      ignore: []
  react/jsx-uses-react:
    - error
  react/jsx-uses-vars:
    - error
  react/jsx-filename-extension:
    - error
    - extensions: [ ".js" ]

  # Developer Support
  react/display-name: error
  react/require-render-return: error
  react/jsx-key: error

  # Bad practise
  react/no-children-prop: error

  # Make sure React is imported when using JSX
  react/react-in-jsx-scope: error

  # Good idea but currently warns on too many false issues
  react/no-unused-prop-types: off

  # Good idea but currently breaks with helper rendering methods for functional components
  react/no-multi-comp: off

  # Clean code
  react/prefer-es6-class: error
  react/prefer-stateless-function: error
  react/self-closing-comp: error
  react/sort-comp: error
  react/jsx-wrap-multilines: error

  # Formatting
  react/jsx-closing-bracket-location:
    - error
    - line-aligned
  react/jsx-curly-spacing:
    - error
  react/jsx-handler-names:
    - off
  react/jsx-indent:
    - error
    - 2
  react/jsx-indent-props:
    - error
    - 2

  # Unsafe
  react/no-danger: error
  react/no-danger-with-children: error
  react/no-direct-mutation-state: error
  react/no-unescaped-entities: error
  react/style-prop-object: error
  react/jsx-no-duplicate-props:
    - error
    - ignoreCase: true
  react/jsx-no-target-blank: error

  # Don't pollute DOM
  react/no-unknown-property: error

  # Deprecated
  react/no-deprecated: error
  react/no-is-mounted: error
  react/no-string-refs: error

  # Unsafe + Bad performance + Deprecated
  react/no-find-dom-node: error

  # Bad performance
  react/no-did-mount-set-state: error
  react/no-did-update-set-state: error
  react/jsx-no-bind: warn

  #######################################################################################
  # Accessibility Plugin
  #######################################################################################

  jsx-a11y/aria-role: error
  jsx-a11y/img-has-alt: error
  jsx-a11y/img-redundant-alt: error
  jsx-a11y/no-access-key: error
  jsx-a11y/aria-props: error
  jsx-a11y/label-has-for: error
  jsx-a11y/role-has-required-aria-props: error


  #######################################################################################
  # Promise Plugin
  #######################################################################################

  promise/param-names: error
  promise/always-return: off
  promise/catch-or-return: warn
  promise/no-native: off

  # Currently fails with hard eslint parse errors in some use cases (v3)
  # promise/no-return-wrap: error


  #######################################################################################
  # Other Plugins
  #######################################################################################

  # Prevent old style extensions of native objects
  no-use-extend-native/no-use-extend-native: error

  # Don't allow dashes or underscores. Keep in sync with exported symbol name.
  filenames/match-regex:
    - error
    - "^[a-zA-Z][a-zA-Z0-9.]+$"
  filenames/match-exported: error

  # Index files are okay
  filenames/no-index: off

  # Most of the normal ES2015 methods are okay to use nowadays
  lodash/prefer-lodash-method: off

  # Not every type check has to use a lodash method
  lodash/prefer-lodash-typecheck: off

  # Utility method should not be a requirement
  lodash/prefer-constant: off

  # Warns on "global" imports, but also detects cherry imports (which are the future)
  lodash/import-scope: off

  # Typically we use Babel/Buble in most projects right now
  node/no-unsupported-features: off

  # NPM installs in a flat hierarchy which prevent detecting request solved by dependencies
  node/no-unpublished-require: off

  # Duplicated
  unicorn/no-process-exit: off

  # We have something more powerful available to check filenames
  unicorn/filename-case: off

  unicorn/catch-error-name:
    - error
    - name: error

  # Improve support for usage of Flowtype
  flowtype-errors/show-errors: error