module.exports = class ArrowSpacing

    rule:
        name: 'arrow_spacing'
        level : 'ignore'
        message : 'Function arrow (->) must be spaced properly'
        description: """
            <p>This rule checks to see that there is spacing before and after
            the arrow operator that declares a function. This rule is disabled
            by default.</p> <p>Note that if arrow_spacing is enabled, and you
            pass an empty function as a parameter, arrow_spacing will accept
            either a space or no space in-between the arrow operator and the
            parenthesis</p>
            <pre><code># Both of this will not trigger an error,
            # even with arrow_spacing enabled.
            x(-> 3)
            x( -> 3)

            # However, this will trigger an error
            x((a,b)-> 3)
            </code>
            </pre>
             """

    tokens: [ '->' ]

    lintToken : (token, tokenApi) ->
        # Throw error unless the following happens.
        #
        # We will take a look at the previous token to see
        # 1. That the token is properly spaced
        # 2. Wasn't generated by the CoffeeScript compiler
        # 3. That it is just indentation
        # 4. If the function declaration has no parameters
        # e.g. x(-> 3)
        #      x( -> 3)
        #
        # or a statement is wrapped in parentheses
        # e.g. (-> true)()
        #
        # we will accept either having a space or not having a space there.

        pp = tokenApi.peek(-1)
        unless (token.spaced? or token.newLine? or @atEof(tokenApi)) and
               # Throw error unless the previous token...
               ((pp.spaced? or pp[0] is 'TERMINATOR') or #1
                pp.generated? or #2
                pp[0] is "INDENT" or #3
                (pp[1] is "(" and not pp.generated?)) #4
            true
        else
            null

    # Are there any more meaningful tokens following the current one?
    atEof: (tokenApi) ->
        {tokens, i } = tokenApi
        for token in tokens.slice(i + 1)
            unless token.generated or token[0] in ['OUTDENT', 'TERMINATOR']
                return false
        true