1 files changed, 134 insertions, 0 deletions
diff --git a/gfx/wr/wrench/src/parse_function.rs b/gfx/wr/wrench/src/parse_function.rs
new file mode 100644
index 0000000000..92040b7680
--- /dev/null
+++ b/gfx/wr/wrench/src/parse_function.rs
@@ -0,0 +1,134 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::str::CharIndices;
+
+// support arguments like '4', 'ab', '4.0', '>=10.14', '*123'
+fn acceptable_arg_character(c: char) -> bool {
+    c.is_alphanumeric() || c == '.' || c == '-' || c == '<' || c == '>' || c == '=' || c == '*'
+}
+
+// A crappy parser for parsing strings like "translate(1, 3) blahblah"
+// Returns a tuple with three components:
+// - First component is the function name (e.g. "translate")
+// - Second component is the list of arguments (e.g. vec!["1", "3"])
+// - Third component is the rest of the string "blahblah"
+pub fn parse_function(s: &str) -> (&str, Vec<&str>, &str) {
+    // XXX: This is not particularly easy to read. Sorry.
+    struct Parser<'a> {
+        itr: CharIndices<'a>,
+        start: usize,
+        o: Option<(usize, char)>,
+    }
+    impl<'a> Parser<'a> {
+        fn skip_whitespace(&mut self) {
+            while let Some(k) = self.o {
+                if !k.1.is_whitespace() {
+                    break;
+                }
+                self.start = k.0 + k.1.len_utf8();
+                self.o = self.itr.next();
+            }
+        }
+    }
+    let mut c = s.char_indices();
+    let o = c.next();
+    let mut p = Parser {
+        itr: c,
+        start: 0,
+        o,
+    };
+
+    p.skip_whitespace();
+
+    let mut end = p.start;
+    while let Some(k) = p.o {
+        if !k.1.is_alphabetic() && k.1 != '_' && k.1 != '-' {
+            break;
+        }
+        end = k.0 + k.1.len_utf8();
+        p.o = p.itr.next();
+    }
+
+    let name = &s[p.start .. end];
+    let mut args = Vec::new();
+
+    p.skip_whitespace();
+
+    if let Some(k) = p.o {
+        if k.1 != '(' {
+            return (name, args, &s[p.start ..]);
+        }
+        p.start = k.0 + k.1.len_utf8();
+        p.o = p.itr.next();
+    }
+
+    loop {
+        p.skip_whitespace();
+
+        let mut end = p.start;
+        let mut brackets: Vec<char> = Vec::new();
+        while let Some(k) = p.o {
+            let prev_bracket_count = brackets.len();
+            match k.1 {
+                '[' | '(' => brackets.push(k.1),
+                ']' | ')' => {
+                    let open_bracket = match k.1 {
+                        ']' => '[',
+                        ')' => '(',
+                        _ => panic!(),
+                    };
+                    match brackets.pop() {
+                        // Allow final closing ) for command invocation after args
+                        None if k.1 == ')' => break,
+                        Some(bracket) if bracket == open_bracket => {}
+                        _ => panic!("Unexpected closing bracket {}", k.1),
+                    }
+                }
+                _ => {}
+            }
+
+            let not_in_bracket = brackets.is_empty() && prev_bracket_count == 0;
+            if !acceptable_arg_character(k.1) && not_in_bracket {
+                break;
+            }
+            end = k.0 + k.1.len_utf8();
+            p.o = p.itr.next();
+        }
+
+        args.push(&s[p.start .. end]);
+
+        p.skip_whitespace();
+
+        if let Some(k) = p.o {
+            p.start = k.0 + k.1.len_utf8();
+            p.o = p.itr.next();
+            // unless we find a comma we're done
+            if k.1 != ',' {
+                if k.1 != ')' {
+                    panic!("Unexpected closing character: {}", k.1);
+                }
+                break;
+            }
+        } else {
+            break;
+        }
+    }
+    (name, args, &s[p.start ..])
+}
+
+#[test]
+fn test() {
+    assert_eq!(parse_function("rotate(40)").0, "rotate");
+    assert_eq!(parse_function("  rotate(40)").0, "rotate");
+    assert_eq!(parse_function("  rotate  (40)").0, "rotate");
+    assert_eq!(parse_function("  rotate  (  40 )").1[0], "40");
+    assert_eq!(parse_function("rotate(-40.0)").1[0], "-40.0");
+    assert_eq!(parse_function("drop-shadow(0, [1, 2, 3, 4], 5)").1[0], "0");
+    assert_eq!(parse_function("drop-shadow(0, [1, 2, 3, 4], 5)").1[1], "[1, 2, 3, 4]");
+    assert_eq!(parse_function("drop-shadow(0, [1, 2, 3, 4], 5)").1[2], "5");
+    assert_eq!(parse_function("drop-shadow(0, [1, 2, [3, 4]], 5)").1[1], "[1, 2, [3, 4]]");
+    assert_eq!(parse_function("func(nest([1, 2]), [3, 4])").1[0], "nest([1, 2])");
+    assert_eq!(parse_function("func(nest([1, 2]), [nest(3), nest(4)])").1[1], "[nest(3), nest(4)]");
+}