# This is the Pegex grammar for YAML 1.2.

# TODO:
# Define regexes from spec productions

%grammar yaml
%version 0.1.2
%include pegex-atoms
%symrule >>> indent
%symrule <<< undent
%symrule === ondent
%symrule >=< andent

yaml-stream: (
| comment-line
| blank-line
| yaml-document
)*

yaml-document:
  document-header?
  yaml-node
  document-footer?

document-header: '---' +

document-footer: '...' EOL

block-node:
|  block-seq
|  block-map
|  block-scalar

block-map:
  >>
  block-pair+
  <<

block-seq:
  >>
  block-elem+
  <<

block-scalar:
|  double-quoted
|  single-quoted
|  plain-string
|  empty-string

#   literal-string |
#   folded-string |

block-pair:
  == block-key - COLON - block-value BREAK

block-elem:
  == '- ' block-value BREAK

block-key:
| double-quoted
| single-quoted
| plain-string

block-value:
| flow-collection
| block-node

flow-collection:
| flow-map
| flow-seq

flow-node:
| flow-collection
| flow-scalar

flow-map:
  - '{' -
    flow-pair* % /- COMMA -/
  - '}' -

flow-seq:
  - '[' -
    flow-node* % /- COMMA -/
  /- RSQUARE -/

flow-scalar:
| double-quoted |
| single-quoted |
| plain-string

flow-pair:
  flow-node /- COLON -/ flow-node

double-quoted: /
  DOUBLE
    ((:
    |  BACK BACK
    |  BACK DOUBLE
    |  [^DOUBLE BREAK]
    )*)
  DOUBLE
/

single-quoted: /
  SINGLE
    ((:
    | SINGLE SINGLE
    | [^ SINGLE ]
    )*)
  SINGLE
/

plain-string: / ( [^ non-starters ] [^ non-plain ]* ) /

empty-string: //

literal-string: `literal-string not yet supported`

folded-string: `folded-string not yet supported`

non-starters: /
  PERCENT
  SINGLE
  DOUBLE
  SPACE
/

non-plain: /
  COLON
  BREAK
/