grammar InkBlotAntlrGrammar;

import InkBlotAntlrLexer;

/*
 * STORY
 */

story: topLevelStatements ;

/*
 * STATEMENTS FOR THE VARIOUS LEVELS
 */

topLevelStatements:
    topLevelStatement+
    ;

topLevelStatement:
    contentText
    | multiDivert
    ;

 knotLevelStatements:
    (contentText
    | multiDivert
    )+
    ;

 stitchLevelStatements:
    (contentText
    | multiDivert
    )+
    ;

 innerBlockLevelStatements:
    (contentText
    | multiDivert
    )+
    ;

/*
 * STATEMENTS
 */

contentText: CONTENT_TEXT_NO_ESCAPE_SIMPLE ;

mixedTextAndLogic:
    // TODO: ~ is not allowed as first symbol of this (see InkParser_Content => MixedTextAndLog), let's implement it in the C# side?
    // like in innerInlineSequenceObjects, a bit of a chaos to avoid having completely empty entries
    contentText? (inlineLogicOrGlueOrTagStart? contentText | inlineLogicOrGlueOrTagStart contentText?)+
    // TODO: this is valid only when not parsing a choice, see above for the code where this logic is implemented
    multiDivert
    // TODO: management of tag ftw O_O
    ;

inlineLogicOrGlueOrTagStart:
    inlineLogic
    // TODO: glue, tag start
    ;

inlineLogic:
    INLINE_LOGIC_START
    WS?
    innerLogic
    // TODO: += and -= are disabled here (don't know why)
    WS?
    INLINE_LOGIC_END
    // TODO: tags ftw
    ;
    
innerLogic:
    WS?
    sequenceTypeAnnotation innerSequenceObjects
    // TODO: the rest of InkParser_Logic => InnerLogic
    ;

multiDivert:
    WS?
    (
        THREAD_ARROW divertIdentifierWithArguments
        // here be dragons: trying to express the various "Possible patterns" of InkParser_Divert => MultiDivert
        | (DIVERT_ARROW divertIdentifierWithArguments)+ TUNNEL_ARROW divertIdentifierWithArguments
        | (DIVERT_ARROW divertIdentifierWithArguments)+ TUNNEL_ARROW
        | (DIVERT_ARROW divertIdentifierWithArguments)+ DIVERT_ARROW
        | TUNNEL_ARROW
        | DIVERT_ARROW // TODO: this is only valid in default choices ( https://github.com/inkle/ink/blob/master/Documentation/WritingWithInk.md#fallback-choices )
    ) 
    ;

divertIdentifierWithArguments:
    WS? identifier WS? ('.' WS? identifier WS? )*
    WS?
    (
    '('
    expression (',' expression)*
    ')'
    )?
    WS?
    ;

identifier:
    // TODO: reject numbers-only identifier - see InkParser_Logic => Identifier
    IDENTIFIER
    ;

expression:
    // TODO: temporary stuff here
    IDENTIFIER
    ;

// all possible symbols or word(s) for sequencing
sequenceTypeAnnotation:
    op=SEQUENCE_TYPE_SYMBOL_ANNOTATION
    | ONCE
    | CYCLE
    | SHUFFLE
    | STOPPING
    | SHUFFLE_ONCE
    | SHUFFLE_STOPPING
    ;

/* a list of sequence objects, either compressed in a single line (e.g.: {a|b|c}) or expanded in multiple lines (e.g.:
{\n- a\n- b\n- c}
*/
innerSequenceObjects:
    NL innerMultilineSequenceObjects
    | innerInlineSequenceObjects
    ;

innerMultilineSequenceObjects:
    singleMultilineSequenceElement+
    ;

singleMultilineSequenceElement:
    WS?
    /* TODO: how to express this? and why is it here? InkParser_Sequences => SingleMultilineSequenceElement
            if (ParseString ("->") != null)
                return null;
    */
    '-'
    WS?
    (
        innerBlockLevelStatements
        | MULTILINE_WS
    )
    ;

innerInlineSequenceObjects:
    // it's a bit chaotic, in order to allow for empty mixedTextAndLogic, but always require at least one entry
    (mixedTextAndLogic ('|' mixedTextAndLogic?)*)
    | ('|' mixedTextAndLogic?)+
    ;