1 files changed, 93 insertions, 0 deletions
diff --git a/web/src/js/filt/filt.pegjs b/web/src/js/filt/filt.pegjs
new file mode 100644
index 00000000..06e2ecb3
--- /dev/null
+++ b/web/src/js/filt/filt.pegjs
@@ -0,0 +1,93 @@
+// PEG.js filter rules - see http://pegjs.majda.cz/online
+
+/* Explain Filter */
+{
+  var or = function(first, second) {
+    return first + " or " + second;
+  };
+  var and = function(first, second) {
+    return first + " and " + second;
+  };
+  var not = function(expr) {
+    return "not " + expr;
+  };
+  var binding = function(expr) {
+    return "(" + expr + ")";
+  }
+  var assetFilter = "is asset";
+  var trueFilter = true;
+  var falseFilter = false;
+  var bodyFilter = function(s) {
+    return "body ~= '" + s + "'";
+  }
+  var urlFilter = function(s) {
+    return "url ~= '" + s + "'";
+  }
+}
+
+start "filter expression"
+  = __ orExpr:OrExpr __ { return orExpr; }
+
+ws "whitespace" = [ \t\n\r]
+cc "control character" = [|&!()~"]
+__ "optional whitespace" = ws*
+
+OrExpr
+  = first:AndExpr __ "|" __ second:OrExpr 
+    { return or(first, second); }
+  / AndExpr
+
+AndExpr
+  = first:NotExpr __ "&" __ second:AndExpr 
+    { return and(first, second); }
+  / first:NotExpr ws+ second:AndExpr 
+    { return and(first, second); }
+  / NotExpr
+
+NotExpr
+  = "!" __ expr:NotExpr 
+    { return not(expr); }
+  / BindingExpr
+
+BindingExpr
+  = "(" __ expr:OrExpr __ ")" 
+    { return binding(orExpr); }
+  / Expr
+
+Expr
+  = NullaryExpr
+  / UnaryExpr
+
+NullaryExpr
+  = BooleanLiteral
+  / "~a" { return assetFilter; };
+
+BooleanLiteral
+  = "true" { return trueFilter; }
+  / "false" { return falseFilter; }
+
+UnaryExpr
+  = "~b" ws+ s:StringLiteral { return bodyFilter(s); }
+  / s:StringLiteral { return urlFilter(s); }
+
+StringLiteral "string"
+  = '"' chars:DoubleStringChar* '"' { return chars.join(""); }
+  / "'" chars:SingleStringChar* "'" { return chars.join(""); }
+  / !cc chars:UnquotedStringChar+ { return chars.join(""); }
+
+DoubleStringChar
+  = !["\\] char:. { return char; }
+  / "\\" char:EscapeSequence { return char; }
+
+SingleStringChar
+  = !['\\] char:. { return char; }
+  / "\\" char:EscapeSequence { return char; }
+
+UnquotedStringChar
+  = !ws char:. { return char; }
+
+EscapeSequence
+  = ['"\\]
+  / "n" { return "\n"; }
+  / "r" { return "\r"; }
+  / "t" { return "\t"; }
+\ No newline at end of file