1 files changed, 152 insertions, 0 deletions
diff --git a/gerbonara/cad/kicad/sexp.py b/gerbonara/cad/kicad/sexp.py
new file mode 100644
index 0000000..9312489
--- /dev/null
+++ b/gerbonara/cad/kicad/sexp.py
@@ -0,0 +1,152 @@
+import math
+import re
+import functools
+from typing import Any, Optional
+import uuid
+from dataclasses import dataclass, fields, field
+from copy import deepcopy
+
+
+class SexpError(ValueError):
+    """ Low-level error parsing S-Expression format """ 
+    pass
+
+
+class FormatError(ValueError):
+    """ Semantic error in S-Expression structure """
+    pass
+
+
+class AtomType(type):
+    def __getattr__(cls, key):
+        return cls(key)
+
+
+@functools.total_ordering
+class Atom(metaclass=AtomType):
+    def __init__(self, obj=''):
+        if isinstance(obj, str):
+            self.value = obj
+        elif isinstance(obj, Atom):
+            self.value = obj.value
+        else:
+            raise TypeError(f'Atom argument must be str, not {type(obj)}')
+
+    def __str__(self):
+        return self.value
+
+    def __repr__(self):
+        return f'@{self.value}'
+
+    def __hash__(self):
+        return hash(self.value)
+
+    def __eq__(self, other):
+        if not isinstance(other, (Atom, str)):
+            return self.value == other
+        return self.value == str(other)
+
+    def __lt__(self, other):
+        if not isinstance(other, (Atom, str)):
+            raise TypeError(f'Cannot compare Atom and {type(other)}')
+        return self.value < str(other)
+
+    def __gt__(self, other):
+        if not isinstance(other, (Atom, str)):
+            raise TypeError(f'Cannot compare Atom and {type(other)}')
+        return self.value > str(other)
+
+
+term_regex = r"""(?mx)
+    \s*(?:
+        "((?:\\\\|\\"|[^"])*)"|
+        (\()|
+        (\))|
+        ([+-]?\d+\.\d+(?=[\s\)]))|
+        (\-?\d+(?=[\s\)]))|
+        ([^0-9"\s()][^"\s)]*)
+       )"""
+
+
+def parse_sexp(sexp: str) -> Any:
+    re_iter = re.finditer(term_regex, sexp)
+    rv = list(_parse_sexp_internal(re_iter))
+
+    for leftover in re_iter:
+        quoted_str, lparen, rparen, *rest = leftover.groups()
+        if quoted_str or lparen or any(rest):
+            raise SexpError(f'Leftover garbage after end of expression at position {leftover.start()}')  # noqa: E501
+
+        elif rparen:
+            raise SexpError(f'Unbalanced closing parenthesis at position {leftover.start()}')
+
+    if len(rv) == 0:
+        raise SexpError('No or empty expression')
+
+    if len(rv) > 1:
+        print(rv[0])
+        print(rv[1])
+        raise SexpError('Missing initial opening parenthesis')
+
+    return rv[0]
+
+
+def _parse_sexp_internal(re_iter) -> Any:
+    for match in re_iter:
+        quoted_str, lparen, rparen, float_num, integer_num, bare_str = match.groups()
+
+        if lparen:
+            yield list(_parse_sexp_internal(re_iter))
+        elif rparen:
+            break
+        elif bare_str is not None:
+            yield Atom(bare_str)
+        elif quoted_str is not None:
+            yield quoted_str.replace('\\"', '"')
+        elif float_num:
+            yield float(float_num)
+        elif integer_num:
+            yield int(integer_num)
+
+
+def build_sexp(exp, indent='  ') -> str:
+    # Special case for multi-values
+    if isinstance(exp, (list, tuple)):
+        joined = '('
+        for i, elem in enumerate(exp):
+            if 1 <= i <= 5 and len(joined) < 120 and not isinstance(elem, (list, tuple)):
+                joined += ' '
+            elif i >= 1:
+                joined += '\n' + indent
+            joined += build_sexp(elem, indent=f'{indent}  ')
+        return joined + ')'
+
+    if exp == '':
+        return '""'
+
+    if isinstance(exp, str):
+        exp = exp.replace('"', r'\"')
+        return f'"{exp}"'
+
+    if isinstance(exp, float):
+        # python whyyyy
+        val = f'{exp:.6f}'
+        val = val.rstrip('0')
+        if val[-1] == '.':
+            val += '0'
+        return val
+    else:
+        return str(exp)
+
+
+if __name__ == "__main__":
+    sexp = """ ( ( Winson_GM-402B_5x5mm_P1.27mm data "quoted data" 123 4.5)
+         (data "with \\"escaped quotes\\"")
+         (data (123 (4.5) "(more" "data)")))"""
+
+    print("Input S-expression:")
+    print(sexp)
+    parsed = parse_sexp(sexp)
+    print("\nParsed to Python:", parsed)
+
+    print("\nThen back to: '%s'" % build_sexp(parsed))