overview: |
  Inverted Section tags and End Section tags are used in combination to wrap a
  section of the template.

  These tags' content MUST be a non-whitespace character sequence NOT
  containing the current closing delimiter; each Inverted Section tag MUST be
  followed by an End Section tag with the same content within the same
  section.

  This tag's content names the data to replace the tag.  Name resolution is as
  follows:
    1) Split the name on periods; the first part is the name to resolve, any
    remaining parts should be retained.
    2) Walk the context stack from top to bottom, finding the first context
    that is a) a hash containing the name as a key OR b) an object responding
    to a method with the given name.
    3) If the context is a hash, the data is the value associated with the
    name.
    4) If the context is an object and the method with the given name has an
    arity of 1, the method SHOULD be called with a String containing the
    unprocessed contents of the sections; the data is the value returned.
    5) Otherwise, the data is the value returned by calling the method with
    the given name.
    6) If any name parts were retained in step 1, each should be resolved
    against a context stack containing only the result from the former
    resolution.  If any part fails resolution, the result should be considered
    falsey, and should interpolate as the empty string.
  If the data is not of a list type, it is coerced into a list as follows: if
  the data is truthy (e.g. `!!data == true`), use a single-element list
  containing the data, otherwise use an empty list.

  This section MUST NOT be rendered unless the data list is empty.

  Inverted Section and End Section tags SHOULD be treated as standalone when
  appropriate.
tests:
  - name: Falsey
    desc: Falsey sections should have their contents rendered.
    data: { boolean: false }
    template: '"{{^boolean}}This should be rendered.{{/boolean}}"'
    expected: '"This should be rendered."'

  - name: Truthy
    desc: Truthy sections should have their contents omitted.
    data: { boolean: true }
    template: '"{{^boolean}}This should not be rendered.{{/boolean}}"'
    expected: '""'

  - name: Null is falsey
    desc: Null is falsey.
    data: { "null": null }
    template: '"{{^null}}This should be rendered.{{/null}}"'
    expected: '"This should be rendered."'

  - name: Context
    desc: Objects and hashes should behave like truthy values.
    data: { context: { name: 'Joe' } }
    template: '"{{^context}}Hi {{name}}.{{/context}}"'
    expected: '""'

  - name: List
    desc: Lists should behave like truthy values.
    data: { list: [ { n: 1 }, { n: 2 }, { n: 3 } ] }
    template: '"{{^list}}{{n}}{{/list}}"'
    expected: '""'

  - name: Empty List
    desc: Empty lists should behave like falsey values.
    data: { list: [ ] }
    template: '"{{^list}}Yay lists!{{/list}}"'
    expected: '"Yay lists!"'

  - name: Doubled
    desc: Multiple inverted sections per template should be permitted.
    data: { bool: false, two: 'second' }
    template: |
      {{^bool}}
      * first
      {{/bool}}
      * {{two}}
      {{^bool}}
      * third
      {{/bool}}
    expected: |
      * first
      * second
      * third

  - name: Nested (Falsey)
    desc: Nested falsey sections should have their contents rendered.
    data: { bool: false }
    template: "| A {{^bool}}B {{^bool}}C{{/bool}} D{{/bool}} E |"
    expected: "| A B C D E |"

  - name: Nested (Truthy)
    desc: Nested truthy sections should be omitted.
    data: { bool: true }
    template: "| A {{^bool}}B {{^bool}}C{{/bool}} D{{/bool}} E |"
    expected: "| A  E |"

  - name: Context Misses
    desc: Failed context lookups should be considered falsey.
    data: { }
    template: "[{{^missing}}Cannot find key 'missing'!{{/missing}}]"
    expected: "[Cannot find key 'missing'!]"

  # Dotted Names

  - name: Dotted Names - Truthy
    desc: Dotted names should be valid for Inverted Section tags.
    data: { a: { b: { c: true } } }
    template: '"{{^a.b.c}}Not Here{{/a.b.c}}" == ""'
    expected: '"" == ""'

  - name: Dotted Names - Falsey
    desc: Dotted names should be valid for Inverted Section tags.
    data: { a: { b: { c: false } } }
    template: '"{{^a.b.c}}Not Here{{/a.b.c}}" == "Not Here"'
    expected: '"Not Here" == "Not Here"'

  - name: Dotted Names - Broken Chains
    desc: Dotted names that cannot be resolved should be considered falsey.
    data: { a: { } }
    template: '"{{^a.b.c}}Not Here{{/a.b.c}}" == "Not Here"'
    expected: '"Not Here" == "Not Here"'

  # Whitespace Sensitivity

  - name: Surrounding Whitespace
    desc: Inverted sections should not alter surrounding whitespace.
    data: { boolean: false }
    template: " | {{^boolean}}\t|\t{{/boolean}} | \n"
    expected: " | \t|\t | \n"

  - name: Internal Whitespace
    desc: Inverted should not alter internal whitespace.
    data: { boolean: false }
    template: " | {{^boolean}} {{! Important Whitespace }}\n {{/boolean}} | \n"
    expected: " |  \n  | \n"

  - name: Indented Inline Sections
    desc: Single-line sections should not alter surrounding whitespace.
    data: { boolean: false }
    template: " {{^boolean}}NO{{/boolean}}\n {{^boolean}}WAY{{/boolean}}\n"
    expected: " NO\n WAY\n"

  - name: Standalone Lines
    desc: Standalone lines should be removed from the template.
    data: { boolean: false }
    template: |
      | This Is
      {{^boolean}}
      |
      {{/boolean}}
      | A Line
    expected: |
      | This Is
      |
      | A Line

  - name: Standalone Indented Lines
    desc: Standalone indented lines should be removed from the template.
    data: { boolean: false }
    template: |
      | This Is
        {{^boolean}}
      |
        {{/boolean}}
      | A Line
    expected: |
      | This Is
      |
      | A Line

  - name: Standalone Line Endings
    desc: '"\r\n" should be considered a newline for standalone tags.'
    data: { boolean: false }
    template: "|\r\n{{^boolean}}\r\n{{/boolean}}\r\n|"
    expected: "|\r\n|"

  - name: Standalone Without Previous Line
    desc: Standalone tags should not require a newline to precede them.
    data: { boolean: false }
    template: "  {{^boolean}}\n^{{/boolean}}\n/"
    expected: "^\n/"

  - name: Standalone Without Newline
    desc: Standalone tags should not require a newline to follow them.
    data: { boolean: false }
    template: "^{{^boolean}}\n/\n  {{/boolean}}"
    expected: "^\n/\n"

  # Whitespace Insensitivity

  - name: Padding
    desc: Superfluous in-tag whitespace should be ignored.
    data: { boolean: false }
    template: '|{{^ boolean }}={{/ boolean }}|'
    expected: '|=|'