cad: Add KiCad symbol/footprint parser

8 files changed, 1533 insertions, 0 deletions

diff --git a/gerbonara/cad/kicad/base_types.py b/gerbonara/cad/kicad/base_types.py
new file mode 100644
index 0000000..840b9d5
--- /dev/null
+++ b/gerbonara/cad/kicad/base_types.py
@@ -0,0 +1,122 @@
+from .sexp import *
+from .sexp_mapper import *
+import time
+
+from dataclasses import field
+import math
+import uuid
+
+
+@sexp_type('color')
+class Color:
+    r: int = None
+    g: int = None
+    b: int = None
+    a: int = None
+
+
+@sexp_type('stroke')
+class Stroke:
+    width: Named(float) = 0.254
+    type: Named(AtomChoice(Atom.dash, Atom.dot, Atom.dash_dot_dot, Atom.dash_dot, Atom.default, Atom.solid)) = Atom.default
+    color: Color = None
+
+    @property
+    def width_mil(self):
+        return mm_to_mil(self.width)
+
+    @width_mil.setter
+    def width_mil(self, value):
+        self.width = mil_to_mm(value)
+
+
+@sexp_type('xy')
+class XYCoord:
+    x: float = 0
+    y: float = 0
+
+    def isclose(self, other, tol=1e-6):
+        return math.isclose(self.x, other.x, tol) and math.isclose(self.y, other.y, tol)
+
+
+@sexp_type('pts')
+class PointList:
+    xy : List(XYCoord) = field(default_factory=list)
+
+
+@sexp_type('xyz')
+class XYZCoord:
+    x: float = 0
+    y: float = 0
+    z: float = 0
+
+
+@sexp_type('at')
+class AtPos(XYCoord):
+    x: float = 0 # in millimeter
+    y: float = 0 # in millimeter
+    rotation: int = 0  # in degrees, can only be 0, 90, 180 or 270.
+    unlocked: Flag() = False
+
+    def __before_sexp__(self):
+        self.rotation = int(round(self.rotation % 360))
+
+    @property
+    def rotation_rad(self):
+        return math.radians(self.rotation)
+
+    @rotation_rad.setter
+    def rotation_rad(self, value):
+        self.rotation = math.degrees(value)
+
+
+@sexp_type('font')
+class FontSpec:
+    face: Named(str) = None
+    size: Rename(XYCoord) = field(default_factory=lambda: XYCoord(1.27, 1.27))
+    thickness: Named(float) = None
+    bold: Flag() = False
+    italic: Flag() = False
+    line_spacing: Named(float) = None
+
+
+@sexp_type('justify')
+class Justify:
+    h: AtomChoice(Atom.left, Atom.right) = None
+    v: AtomChoice(Atom.top, Atom.bottom) = None
+    mirror: Flag() = False
+
+
+@sexp_type('effects')
+class TextEffect:
+    font: FontSpec = field(default_factory=FontSpec)
+    justify: OmitDefault(Justify) = field(default_factory=Justify)
+    hide: Flag() = False
+
+
+@sexp_type('tstamp')
+class Timestamp:
+    value: str = field(default_factory=uuid.uuid4)
+
+    def __after_parse__(self, parent):
+        self.value = str(self.value)
+
+    def before_sexp(self):
+        self.value = Atom(str(self.value))
+
+    def bump(self):
+        self.value = uuid.uuid4()
+
+@sexp_type('tedit')
+class EditTime:
+    value: str = field(default_factory=time.time)
+
+    def __after_parse__(self, parent):
+        self.value = int(str(self.value), 16)
+
+    def __before_sexp__(self):
+        self.value = Atom(f'{int(self.value):08X}')
+
+    def bump(self):
+        self.value = time.time()
+
diff --git a/gerbonara/cad/kicad/footprint.py b/gerbonara/cad/kicad/footprint.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/gerbonara/cad/kicad/footprint.py
diff --git a/gerbonara/cad/kicad/footprints.py b/gerbonara/cad/kicad/footprints.py
new file mode 100644
index 0000000..f76fd3f
--- /dev/null
+++ b/gerbonara/cad/kicad/footprints.py
@@ -0,0 +1,316 @@
+"""
+Library for handling KiCad's footprint files (`*.kicad_mod`).
+"""
+
+import copy
+import enum
+import datetime
+import math
+import time
+from typing import Any, Dict, Iterable, List, Optional, Tuple, Union
+
+from .sexp import *
+from .base_types import *
+from .primitives import *
+from . import graphical_primitives as gr
+
+
+@sexp_type('property')
+class Property:
+    key: str = ''
+    value: str = ''
+
+
+@sexp_type('attr')
+class Attribute:
+    type: AtomChoice(Atom.smd, Atom.through_hole) = None
+    board_only: Flag() = False
+    exclude_from_pos_files: Flag() = False
+    exclude_from_bom: Flag() = False
+
+
+@sexp_type('fp_text')
+class Text:
+    type: AtomChoice(Atom.reference, Atom.value, Atom.user) = Atom.user
+    text: str = ""
+    at: AtPos = field(default_factory=AtPos)
+    unlocked: Flag() = False
+    layer: Named(str) = None
+    hide: Flag() = False
+    effects: TextEffect = field(default_factory=TextEffect)
+    tstamp: Timestamp = None
+
+
+@sexp_type('fp_text_box')
+class TextBox:
+    locked: Flag() = False
+    text: str = None
+    start: Rename(XYCoord) = None
+    end: Named(XYCoord) = None
+    pts: PointList = None
+    angle: Named(float) = 0.0
+    layer: Named(str) = None
+    tstamp: Timestamp = None
+    effects: TextEffect = field(default_factory=TextEffect)
+    stroke: Stroke = field(default_factory=Stroke)
+    render_cache: RenderCache = None
+
+
+@sexp_type('fp_line')
+class Line:
+    start: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    stroke: Stroke = None
+    locked: Flag() = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('fp_rect')
+class Rectangle:
+    start: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    stroke: Stroke = None
+    fill: Named(AtomChoice(Atom.solid, Atom.none)) = None
+    locked: Flag() = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('fp_circle')
+class Circle:
+    center: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    stroke: Stroke = None
+    fill: Named(AtomChoice(Atom.solid, Atom.none)) = None
+    locked: Flag() = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('fp_arc')
+class Arc:
+    start: Rename(XYCoord) = None
+    mid: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    stroke: Stroke = None
+    locked: Flag() = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('fp_poly')
+class Polygon:
+    pts: PointList = field(default_factory=PointList)
+    layer: Named(str) = None
+    width: Named(float) = None
+    stroke: Stroke = None
+    fill: Named(AtomChoice(Atom.solid, Atom.none)) = None
+    locked: Flag() = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('fp_curve')
+class Curve:
+    pts: PointList = field(default_factory=PointList)
+    layer: Named(str) = None
+    width: Named(float) = None
+    stroke: Stroke = None
+    locked: Flag() = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('format')
+class DimensionFormat:
+    prefix: Named(str) = None
+    suffix: Named(str) = None
+    units: Named(int) = 3
+    units_format: Named(int) = 0
+    precision: Named(int) = 3
+    override_value: Named(str) = None
+    suppress_zeros: Flag() = False
+
+
+@sexp_type('style')
+class DimensionStyle:
+    thickness: Named(float) = None
+    arrow_length: Named(float) = None
+    text_position_mode: Named(int) = 0
+    extension_height: Named(float) = None
+    text_frame: Named(int) = 0
+    extension_offset: Named(str) = None
+    keep_text_aligned: Flag() = False
+
+
+@sexp_type('dimension')
+class Dimension:
+    locked: Flag() = False
+    type: AtomChoice(Atom.aligned, Atom.leader, Atom.center, Atom.orthogonal, Atom.radial) = None
+    layer: Named(str) = None
+    tstamp: Timestamp = None
+    pts: PointList = field(default_factory=PointList)
+    height: Named(float) = None
+    orientation: Named(int) = 0
+    leader_length: Named(float) = None
+    gr_text: Named(Text) = None
+    format: DimensionFormat = field(default_factory=DimensionFormat)
+    style: DimensionStyle = field(default_factory=DimensionStyle)
+
+
+@sexp_type('drill')
+class Drill:
+    oval: Flag() = False
+    diameter: float = 0
+    width: float = None
+    offset: Rename(XYCoord) = None
+
+
+@sexp_type('net')
+class NetDef:
+    number: int = None
+    name: str = None
+
+
+@sexp_type('options')
+class CustomPadOptions:
+    clearance: Named(AtomChoice(Atom.outline, Atom.convexhull)) = Atom.outline
+    anchor: Named(AtomChoice(Atom.rect, Atom.circle)) = Atom.rect
+
+
+@sexp_type('primitives')
+class CustomPadPrimitives:
+    annotation_bboxes: List(gr.AnnotationBBox) = field(default_factory=list)
+    lines: List(gr.Line) = field(default_factory=list)
+    rectangles: List(gr.Rectangle) = field(default_factory=list)
+    circles: List(gr.Circle) = field(default_factory=list)
+    arcs: List(gr.Arc) = field(default_factory=list)
+    polygons: List(gr.Polygon) = field(default_factory=list)
+    curves: List(gr.Curve) = field(default_factory=list)
+    width: Named(float) = None
+    fill: Named(YesNoAtom()) = True
+
+
+@sexp_type('chamfer')
+class Chamfer:
+    top_left: Flag() = False
+    top_right: Flag() = False
+    bottom_left: Flag() = False
+    bottom_right: Flag() = False
+
+@sexp_type('pad')
+class Pad:
+    number: str = None
+    type: AtomChoice(Atom.thru_hole, Atom.smd, Atom.connect, Atom.np_thru_hole) = None
+    shape: AtomChoice(Atom.circle, Atom.rect, Atom.oval, Atom.trapezoid, Atom.roundrect, Atom.custom) = None
+    at: AtPos = field(default_factory=AtPos)
+    locked: Wrap(Flag()) = False
+    size: Rename(XYCoord) = field(default_factory=XYCoord)
+    drill: Drill = None
+    layers: Named(Array(str)) = field(default_factory=list)
+    properties: List(Property) = field(default_factory=list)
+    remove_unused_layers: Wrap(Flag()) = False
+    keep_end_layers: Wrap(Flag()) = False
+    rect_delta: Rename(XYCoord) = None
+    roundrect_rratio: Named(float) = None
+    thermal_bridge_angle: Named(int) = 45
+    chamfer_ratio: Named(float) = None
+    chamfer: Chamfer = None
+    net: NetDef = None
+    tstamp: Timestamp = None
+    pin_function: Named(str) = None
+    pintype: Named(str) = None
+    die_length: Named(float) = None
+    solder_mask_margin: Named(float) = None
+    solder_paste_margin: Named(float) = None
+    solder_paste_margin_ratio: Named(float) = None
+    clearance: Named(float) = None
+    zone_connect: Named(int) = None
+    thermal_width: Named(float) = None
+    thermal_gap: Named(float) = None
+    options: OmitDefault(CustomPadOptions) = None
+    primitives: OmitDefault(CustomPadPrimitives) = None
+
+
+@sexp_type('group')
+class Group:
+    name: str = ""
+    id: Named(str) = ""
+    members: Named(List(str)) = field(default_factory=list)
+
+
+@sexp_type('model')
+class Model:
+    name: str = ''
+    at: Named(XYZCoord) = field(default_factory=XYZCoord)
+    offset: Named(XYZCoord) = field(default_factory=XYZCoord)
+    scale: Named(XYZCoord) = field(default_factory=XYZCoord)
+    rotate: Named(XYZCoord) = field(default_factory=XYZCoord)
+
+
+SUPPORTED_FILE_FORMAT_VERSIONS = [20210108, 20211014, 20221018]
+@sexp_type('footprint')
+class Footprint:
+    name: str = None
+    _version: Named(int, name='version') = 20210108
+    generator: Named(Atom) = Atom.kicad_library_utils
+    locked: Flag() = False
+    placed: Flag() = False
+    layer: Named(str) = 'F.Cu'
+    tedit: EditTime = field(default_factory=EditTime)
+    tstamp: Timestamp = None
+    at: AtPos = field(default_factory=AtPos)
+    descr: Named(str) = None
+    tags: Named(str) = None
+    properties: List(Property) = field(default_factory=list)
+    path: Named(str) = None
+    autoplace_cost90: Named(float) = None
+    autoplace_cost180: Named(float) = None
+    solder_mask_margin: Named(float) = None
+    solder_paste_margin: Named(float) = None
+    solder_paste_ratio: Named(float) = None
+    clearance: Named(float) = None
+    zone_connect: Named(int) = None
+    thermal_width: Named(float) = None
+    thermal_gap: Named(float) = None
+    attributes: List(Attribute) = field(default_factory=list)
+    private_layers: Named(str) = None
+    net_tie_pad_groups: Named(str) = None
+    texts: List(Text) = field(default_factory=list)
+    text_boxes: List(TextBox) = field(default_factory=list)
+    lines: List(Line) = field(default_factory=list)
+    rectangles: List(Rectangle) = field(default_factory=list)
+    circles: List(Circle) = field(default_factory=list)
+    arcs: List(Arc) = field(default_factory=list)
+    polygons: List(Polygon) = field(default_factory=list)
+    curves: List(Curve) = field(default_factory=list)
+    dimensions: List(Dimension) = field(default_factory=list)
+    pads: List(Pad) = field(default_factory=list)
+    zones: List(Zone) = field(default_factory=list)
+    groups: List(Group) = field(default_factory=list)
+    models: List(Model) = field(default_factory=list)
+    _ : SEXP_END = None
+    original_filename: str = None
+
+    @property
+    def version(self):
+        return self._version
+
+    @version.setter
+    def version(self, value):
+        if value not in SUPPORTED_FILE_FORMAT_VERSIONS:
+            raise FormatError(f'File format version {value} is not supported. Supported versions are {", ".join(map(str, SUPPORTED_FILE_FORMAT_VERSIONS))}.')
+
+    @classmethod
+    def open(cls, filename: str) -> 'Library':
+        with open(filename) as f:
+            return cls.parse(f.read())
+
+    def write(self, filename=None) -> None:
+        with open(filename or self.original_filename, 'w') as f:
+            f.write(build_sexp(sexp(self)))
+
+
diff --git a/gerbonara/cad/kicad/graphical_primitives.py b/gerbonara/cad/kicad/graphical_primitives.py
new file mode 100644
index 0000000..391b38b
--- /dev/null
+++ b/gerbonara/cad/kicad/graphical_primitives.py
@@ -0,0 +1,111 @@
+
+from .sexp import *
+from .base_types import *
+from .primitives import *
+
+@sexp_type('layer')
+class TextLayer:
+    layer: str = ''
+    knockout: Flag() = False
+
+
+@sexp_type('gr_text')
+class Text:
+    text: str = ''
+    at: AtPos = field(default_factory=AtPos)
+    layer: TextLayer = field(default_factory=TextLayer)
+    tstamp: Timestamp = None
+    effects: TextEffect = field(default_factory=TextEffect)
+
+
+@sexp_type('gr_text_box')
+class TextBox:
+    locked: Flag() = False
+    text: str = ''
+    start: Named(XYCoord) = None
+    end: Named(XYCoord) = None
+    pts: PointList = field(default_factory=PointList)
+    angle: OmitDefault(Named(float)) = 0.0
+    layer: Named(str) = ""
+    tstamp: Timestamp = None
+    effects: TextEffect = field(default_factory=TextEffect)
+    stroke: Stroke = field(default_factory=Stroke)
+    render_cache: RenderCache = None
+
+
+@sexp_type('gr_line')
+class Line:
+    start: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    angle: Named(float) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    tstamp: Timestamp = None
+
+
+@sexp_type('fill')
+class FillMode:
+    # Needed for compatibility with weird files
+    fill: AtomChoice(Atom.solid, Atom.yes, Atom.no, Atom.none) = False
+
+    @classmethod
+    def __map__(self, obj, parent=None):
+        return obj[0] in (Atom.solid, Atom.yes)
+
+    @classmethod
+    def __sexp__(self, value):
+        yield [Atom.fill, Atom.solid if value else Atom.none]
+
+@sexp_type('gr_rect')
+class Rectangle:
+    start: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    fill: FillMode = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('gr_circle')
+class Circle:
+    center: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    fill: FillMode = False
+    tstamp: Timestamp = None
+
+
+@sexp_type('gr_arc')
+class Arc:
+    start: Rename(XYCoord) = None
+    mid: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    layer: Named(str) = None
+    width: Named(float) = None
+    tstamp: Timestamp = None
+
+
+@sexp_type('gr_poly')
+class Polygon:
+    pts: PointList = field(default_factory=PointList)
+    layer: Named(str) = None
+    width: Named(float) = None
+    fill: FillMode= False
+    tstamp: Timestamp = None
+
+
+@sexp_type('gr_curve')
+class Curve:
+    pts: PointList = field(default_factory=PointList)
+    layer: Named(str) = None
+    width: Named(float) = None
+    tstamp: Timestamp = None
+
+
+@sexp_type('gr_bbox')
+class AnnotationBBox:
+    start: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+
+ 
diff --git a/gerbonara/cad/kicad/primitives.py b/gerbonara/cad/kicad/primitives.py
new file mode 100644
index 0000000..30ae611
--- /dev/null
+++ b/gerbonara/cad/kicad/primitives.py
@@ -0,0 +1,97 @@
+
+import enum
+
+from .sexp import *
+from .base_types import *
+
+
+@sexp_type('hatch')
+class Hatch:
+    style: AtomChoice(Atom.none, Atom.edge, Atom.full) = Atom.edge
+    pitch: float = 0.5
+
+
+@sexp_type('connect_pads')
+class PadConnection:
+    type: AtomChoice(Atom.thru_hole_only, Atom.full, Atom.no) = None
+    clearance: Named(float) = 0
+
+
+@sexp_type('keepout')
+class ZoneKeepout:
+    tracks_allowed:     Named(YesNoAtom(yes=Atom.allowed, no=Atom.not_allowed), name='tracks')       = True
+    vias_allowed:       Named(YesNoAtom(yes=Atom.allowed, no=Atom.not_allowed), name='vias')         = True
+    pads_allowed:       Named(YesNoAtom(yes=Atom.allowed, no=Atom.not_allowed), name='pads')         = True
+    copperpour_allowed: Named(YesNoAtom(yes=Atom.allowed, no=Atom.not_allowed), name='copperpour')   = True
+    footprints_allowed: Named(YesNoAtom(yes=Atom.allowed, no=Atom.not_allowed), name='footprints')   = True
+
+
+@sexp_type('smoothing')
+class ZoneSmoothing:
+    style: AtomChoice(Atom.chamfer, Atom.fillet) = Atom.chamfer
+    radius: Named(float) = None
+
+
+@sexp_type('fill')
+class ZoneFill:
+    yes: Flag() = False
+    mode: Flag(atom=Atom.hatched) = False
+    thermal_gap: Named(float) = 0.508
+    thermal_bridge_width: Named(float) = 0.508
+    smoothing: ZoneSmoothing = None
+    island_removal_node: Named(int) = None
+    islan_area_min: Named(float) = None
+    hatch_thickness: Named(float) = None
+    hatch_gap: Named(float) = None
+    hatch_orientation: Named(int) = None
+    hatch_smoothing_level: Named(int) = None
+    hatch_smoothing_value: Named(float) = None
+    hatch_border_algorithm: Named(int) = None
+    hatch_min_hole_area: Named(float) = None
+
+
+@sexp_type('filled_polygon')
+class FillPolygon:
+    layer: Named(str) = ""
+    pts: PointList = field(default_factory=PointList)
+
+
+@sexp_type('fill_segments')
+class FillSegment:
+    layer: Named(str) = ""
+    pts: PointList = field(default_factory=PointList)
+
+
+@sexp_type('zone')
+class Zone:
+    net: Named(int) = 0
+    net_name: Named(str) = ""
+    layer: Named(str) = None
+    layers: Named(Array(str)) = None
+    tstamp: Timestamp = None
+    name: Named(str) = None
+    hatch: Hatch = None
+    priority: OmitDefault(Named(int)) = 0
+    connect_pads: PadConnection = field(default_factory=PadConnection)
+    min_thickness: Named(float) = 0.254
+    filled_areas_thickness: Flag() = True
+    keepouts: List(ZoneKeepout) = field(default_factory=list)
+    fill: ZoneFill = field(default_factory=ZoneFill)
+    polygon: Named(PointList) = field(default_factory=PointList)
+    fill_polygons: List(FillPolygon) = field(default_factory=list)
+    fill_segments: List(FillSegment) = field(default_factory=list)
+
+
+@sexp_type('polygon')
+class RenderCachePolygon:
+    pts: PointList = field(default_factory=PointList)
+
+
+@sexp_type('render_cache')
+class RenderCache:
+    text: str = None
+    rotation: int = 0
+    polygons: List(RenderCachePolygon) = field(default_factory=list)
+
+
+
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))
diff --git a/gerbonara/cad/kicad/sexp_mapper.py b/gerbonara/cad/kicad/sexp_mapper.py
new file mode 100644
index 0000000..cb7c99f
--- /dev/null
+++ b/gerbonara/cad/kicad/sexp_mapper.py
@@ -0,0 +1,289 @@
+
+from dataclasses import MISSING
+from .sexp import *
+
+
+SEXP_END = type('SEXP_END', (), {})
+
+
+class AtomChoice:
+    def __init__(self, *choices):
+        self.choices = choices
+
+    def __contains__(self, value):
+        return value in self.choices
+
+    def __atoms__(self):
+        return self.choices
+
+    def __map__(self, obj, parent=None):
+        obj, = obj
+        if obj not in self:
+            raise TypeError(f'Invalid atom {obj} for {type(self)}, valid choices are: {", ".join(map(str, self.choices))}')
+        return obj
+
+    def __sexp__(self, value):
+        yield value
+
+
+class Flag:
+    def __init__(self, atom=None, invert=None):
+        self.atom, self.invert = atom, invert
+
+    def __bind_field__(self, field):
+        if self.atom is None:
+            self.atom = Atom(field.name)
+        if self.invert is None:
+            self.invert = bool(field.default)
+
+    def __atoms__(self):
+        return [self.atom]
+
+    def __map__(self, obj, parent=None):
+        return not self.invert
+
+    def __sexp__(self, value):
+        if bool(value) == (not self.invert):
+            yield self.atom
+
+
+def sexp(t, v):
+    if v is None:
+        return []
+    elif t in (int, float, str, Atom):
+        return [t(v)]
+    elif hasattr(t, '__sexp__'):
+        return list(t.__sexp__(v))
+    elif isinstance(t, list):
+        t, = t
+        return [sexp(t, elem) for elem in v]
+    else:
+        raise TypeError(f'Python type {t} has no defined s-expression serialization')
+
+
+def map_sexp(t, v, parent=None):
+    if t is not Atom and hasattr(t, '__map__'):
+        return t.__map__(v, parent=parent)
+    elif t in (int, float, str, Atom):
+        v, = v
+        if not isinstance(v, t):
+            types = set({type(v), t})
+            if types == {int, float} or types == {str, Atom}:
+                v = t(v)
+            else:
+                raise TypeError(f'Cannot map s-expression value {v} of type {type(v)} to Python type {t}')
+        return v
+    elif isinstance(t, list):
+        t, = t
+        return [map_sexp(t, elem, parent=parent) for elem in v]
+    else:
+        raise TypeError(f'Python type {t} has no defined s-expression deserialization')
+
+
+class WrapperType:
+    def __init__(self, next_type):
+        self.next_type = next_type
+
+    def __bind_field__(self, field):
+        self.field = field
+        getattr(self.next_type, '__bind_field__', lambda x: None)(field)
+
+    def __atoms__(self):
+        if hasattr(self, 'name_atom'):
+            return [self.name_atom]
+        elif self.next_type is Atom:
+            return []
+        else:
+            return getattr(self.next_type, '__atoms__', lambda: [])()
+
+class Named(WrapperType):
+    def __init__(self, next_type, name=None):
+        super().__init__(next_type)
+        self.name_atom = Atom(name) if name else None
+
+    def __bind_field__(self, field):
+        if self.next_type is not Atom:
+            getattr(self.next_type, '__bind_field__', lambda x: None)(field)
+        if self.name_atom is None:
+            self.name_atom = Atom(field.name)
+
+    def __map__(self, obj, parent=None):
+        k, *obj = obj
+        if self.next_type in (int, float, str, Atom) or isinstance(self.next_type, AtomChoice):
+            return map_sexp(self.next_type, [*obj], parent=parent)
+        else:
+            return map_sexp(self.next_type, obj, parent=parent)
+
+    def __sexp__(self, value):
+        value = sexp(self.next_type, value)
+        if value is not None:
+            yield [self.name_atom, *value]
+
+
+class Rename(WrapperType):
+    def __init__(self, next_type, name=None):
+        super().__init__(next_type)
+        self.name_atom = Atom(name) if name else None
+
+    def __bind_field__(self, field):
+        if self.name_atom is None:
+            self.name_atom = Atom(field.name)
+
+    def __map__(self, obj, parent=None):
+        return map_sexp(self.next_type, obj, parent=parent)
+
+    def __sexp__(self, value):
+        value, = sexp(self.next_type, value)
+        if self.next_type in (str, float, int, Atom): 
+            yield [self.name_atom, *value]
+        else:
+            key, *rest = value
+            yield [self.name_atom, *rest]
+
+
+class OmitDefault(WrapperType):
+    def __bind_field__(self, field):
+        getattr(self.next_type, '__bind_field__', lambda x: None)(field)
+        if field.default_factory != MISSING:
+            self.default = field.default_factory()
+        else:
+            self.default = field.default
+
+    def __map__(self, obj, parent=None):
+        return map_sexp(self.next_type, obj, parent=parent)
+
+    def __sexp__(self, value):
+        if value != self.default:
+            yield from sexp(self.next_type, value)
+
+
+class YesNoAtom:
+    def __init__(self, yes=Atom.yes, no=Atom.no):
+        self.yes, self.no = yes, no
+
+    def __map__(self, value, parent=None):
+        value, = value
+        return value == self.yes
+
+    def __sexp__(self, value):
+        yield self.yes if value else self.no
+
+
+class Wrap(WrapperType):
+    def __map__(self, value, parent=None):
+        value, = value
+        return map_sexp(self.next_type, value, parent=parent)
+
+    def __sexp__(self, value):
+        for inner in sexp(self.next_type, value):
+            yield [inner]
+
+
+class Array(WrapperType):
+    def __map__(self, value, parent=None):
+        return [map_sexp(self.next_type, [elem], parent=parent) for elem in value]
+    
+    def __sexp__(self, value):
+        for e in value:
+            yield from sexp(self.next_type, e)
+
+
+class List(WrapperType):
+    def __bind_field__(self, field):
+        self.attr = field.name
+
+    def __map__(self, value, parent):
+        l = getattr(parent, self.attr, [])
+        mapped = map_sexp(self.next_type, value, parent=parent)
+        l.append(mapped)
+        setattr(parent, self.attr, l)
+
+    def __sexp__(self, value):
+        for elem in value:
+            yield from sexp(self.next_type, elem)
+
+
+class _SexpTemplate:
+    @staticmethod
+    def __atoms__(kls):
+        return [kls.name_atom]
+
+    @staticmethod
+    def __map__(kls, value, parent=None):
+        positional = iter(kls.positional)
+        inst = kls()
+
+        for v in value[1:]: # skip key
+            if isinstance(v, Atom) and v in kls.keys:
+                name, etype = kls.keys[v]
+                mapped = map_sexp(etype, [v], parent=inst)
+                if mapped is not None:
+                    setattr(inst, name, mapped)
+
+            elif isinstance(v, list):
+                name, etype = kls.keys[v[0]]
+                mapped = map_sexp(etype, v, parent=inst)
+                if mapped is not None:
+                    setattr(inst, name, mapped)
+
+            else:
+                try:
+                    pos_key = next(positional)
+                    setattr(inst, pos_key.name, v)
+                except StopIteration:
+                    raise TypeError(f'Unhandled positional argument {v!r} while parsing {kls}')
+
+        getattr(inst, '__after_parse__', lambda x: None)(parent)
+        return inst
+
+    @staticmethod
+    def __sexp__(kls, value):
+        getattr(value, '__before_sexp__', lambda: None)()
+
+        out = [kls.name_atom]
+        for f in fields(kls):
+            if f.type is SEXP_END:
+                break
+            out += sexp(f.type, getattr(value, f.name))
+        yield out
+
+    @staticmethod
+    def parse(kls, data):
+        return kls.__map__(parse_sexp(data))
+
+    @staticmethod
+    def sexp(self):
+        return next(self.__sexp__(self))
+
+
+def sexp_type(name=None):
+    def register(cls):
+        cls = dataclass(cls)
+        cls.name_atom = Atom(name) if name is not None else None
+        for key in '__sexp__', '__map__', '__atoms__', 'parse':
+            if not hasattr(cls, key):
+                setattr(cls, key, classmethod(getattr(_SexpTemplate, key)))
+
+        if not hasattr(cls, 'sexp'):
+            setattr(cls, 'sexp', getattr(_SexpTemplate, 'sexp'))
+        cls.positional = []
+        cls.keys = {}
+        for f in fields(cls):
+            f_type = f.type
+            if f_type is SEXP_END:
+                break
+
+            if hasattr(f_type, '__bind_field__'):
+                f_type.__bind_field__(f)
+
+            atoms = getattr(f_type, '__atoms__', lambda: [])
+            atoms = list(atoms())
+            for atom in atoms:
+                cls.keys[atom] = (f.name, f_type)
+            if not atoms:
+                cls.positional.append(f)
+
+        return cls
+    return register
+
+
diff --git a/gerbonara/cad/kicad/symbols.py b/gerbonara/cad/kicad/symbols.py
new file mode 100644
index 0000000..de1d23d
--- /dev/null
+++ b/gerbonara/cad/kicad/symbols.py
@@ -0,0 +1,446 @@
+"""
+Library for processing KiCad's symbol files.
+"""
+
+import json
+import string
+import math
+import re
+import sys
+import itertools
+from fnmatch import fnmatch
+from collections import defaultdict
+from dataclasses import field
+from pathlib import Path
+from typing import Any, Dict, List, Optional, Tuple
+
+from .sexp import *
+from .sexp_mapper import *
+from .base_types import *
+
+
+PIN_ETYPE = AtomChoice(Atom.input, Atom.output, Atom.bidirectional, Atom.tri_state, Atom.passive, Atom.free,
+                       Atom.unspecified, Atom.power_in, Atom.power_out, Atom.open_collector, Atom.open_emitter,
+                       Atom.no_connect)
+
+
+PIN_STYLE = AtomChoice(Atom.line, Atom.inverted, Atom.clock, Atom.inverted_clock, Atom.input_low, Atom.clock_low,
+                       Atom.output_low, Atom.edge_clock_high, Atom.non_logic)
+
+
+@sexp_type('alternate')
+class AltFunction:
+    name: str = None
+    etype: PIN_ETYPE = Atom.unspecified
+    shape: PIN_STYLE = Atom.line
+
+
+@sexp_type('__styled_text')
+class StyledText:
+    value: str = None
+    effects: TextEffect = field(default_factory=TextEffect)
+
+
+@sexp_type('pin')
+class Pin:
+    etype: PIN_ETYPE = Atom.unspecified
+    style: PIN_STYLE = Atom.line
+    at: AtPos = field(default_factory=AtPos)
+    length: Named(float) = 2.54
+    hide: Flag() = False
+    name: Rename(StyledText) = field(default_factory=StyledText)
+    number: Rename(StyledText) = field(default_factory=StyledText)
+    alternates: List(AltFunction) = field(default_factory=list)
+
+    @property
+    def direction(self):
+        return {0: 'R', 90: 'U', 180: 'L', 270: 'D'}.get(self.at.rotation, 'R')
+
+    @direction.setter
+    def direction(self, value):
+        self.at.rotation = {0: 'R', 90: 'U', 180: 'L', 270: 'D'}[value[0].upper()]
+
+
+@sexp_type('fill')
+class Fill:
+    type: Named(AtomChoice(Atom.none, Atom.outline, Atom.background)) = Atom.none
+
+
+@sexp_type('circle')
+class Circle:
+    center: Rename(XYCoord) = field(default_factory=XYCoord)
+    radius: Named(float) = 0.0
+    stroke: Stroke = field(default_factory=Stroke)
+    fill: Fill = field(default_factory=Fill)
+
+
+@sexp_type('arc')
+class Arc:
+    start: Rename(XYCoord) = field(default_factory=XYCoord)
+    mid: Rename(XYCoord) = field(default_factory=XYCoord)
+    end: Rename(XYCoord) = field(default_factory=XYCoord)
+    stroke: Stroke = field(default_factory=Stroke)
+    fill: Fill = field(default_factory=Fill)
+
+    # TODO add function to calculate center, bounding box
+
+
+@sexp_type('polyline')
+class Polyline:
+    pts: PointList = field(default_factory=PointList)
+    stroke: Stroke = field(default_factory=Stroke)
+    fill: Fill = field(default_factory=Fill)
+
+    @property
+    def points(self):
+        return self.pts.xy
+
+    @points.setter
+    def points(self, value):
+        self.pts.xy = value
+
+    @property
+    def closed(self):
+        # if the last and first point are the same, we consider the polyline closed
+        # a closed triangle will have 4 points (A-B-C-A) stored in the list of points
+        return len(self.points) > 3 and self.points[0] == self.points[-1]
+
+    @property
+    def bbox(self):
+        if not self.points:
+            return (0.0, 0.0, 0.0, 0.0)
+
+        return (min(p.x for p in self.points),
+                min(p.y for p in self.points),
+                max(p.x for p in self.points),
+                max(p.y for p in self.points))
+
+    def as_rectangle(self):
+        (maxx, maxy, minx, miny) = self.get_boundingbox()
+        return Rectangle(
+            minx,
+            maxy,
+            maxx,
+            miny,
+            self.stroke_width,
+            self.stroke_color,
+            self.fill_type,
+            self.fill_color,
+            unit=self.unit,
+            demorgan=self.demorgan,
+        )
+
+    def get_center_of_boundingbox(self):
+        (maxx, maxy, minx, miny) = self.get_boundingbox()
+        return ((minx + maxx) / 2, ((miny + maxy) / 2))
+
+    def is_rectangle(self):
+        # a rectangle has 5 points and is closed
+        if len(self.points) != 5 or not self.is_closed():
+            return False
+
+        # construct lines between the points
+        p0 = self.points[0]
+        for p1_idx in range(1, len(self.points)):
+            p1 = self.points[p1_idx]
+            dx = p1.x - p0.x
+            dy = p1.y - p0.y
+            if dx != 0 and dy != 0:
+                # if a line is neither horizontal or vertical its not
+                # part of a rectangle
+                return False
+            # select next point
+            p0 = p1
+
+        return True
+
+
+@sexp_type('at')
+class TextPos(XYCoord):
+    x: float = 0 # in millimeter
+    y: float = 0 # in millimeter
+    rotation: int = 0  # in degrees
+
+    def __after_parse__(self, parent):
+        self.rotation = self.rotation / 10
+
+    def __before_sexp__(self):
+        self.rotation = round((self.rotation % 360) * 10)
+
+    @property
+    def rotation_rad(self):
+        return math.radians(self.rotation)
+
+    @rotation_rad.setter
+    def rotation_rad(self, value):
+        self.rotation = math.degrees(value)
+
+
+@sexp_type('text')
+class Text:
+    text: str = None
+    at: TextPos = field(default_factory=TextPos)
+    rotation: float = None
+    effects: TextEffect = field(default_factory=TextEffect)
+
+
+@sexp_type('rectangle')
+class Rectangle:
+    """
+    Some v6 symbols use rectangles, newer ones encode them as polylines.
+    At some point in time we can most likely remove this class since its not used anymore
+    """
+
+    start: Rename(XYCoord) = None
+    end: Rename(XYCoord) = None
+    stroke: Stroke = field(default_factory=Stroke)
+    fill: Fill = field(default_factory=Fill)
+
+    def as_polyline(self):
+        x1, y1 = self.start
+        x2, y2 = self.end
+        return Polyline([Point(x1, y1), Point(x2, y1), Point(x2, y2), Point(x1, y2), Point(x1, y1)],
+                        self.stroke, self.fill)
+
+
+@sexp_type('property')
+class Property:
+    name: str = None
+    value: str = None
+    id: Named(int) = None
+    at: AtPos = field(default_factory=AtPos)
+    effects: TextEffect = field(default_factory=TextEffect)
+
+
+@sexp_type('pin_numbers')
+class PinNumberSpec:
+    hide: Flag() = False
+
+
+@sexp_type('pin_names')
+class PinNameSpec:
+    offset: OmitDefault(Named(float)) = 0.508
+    hide: Flag() = False
+
+
+@sexp_type('symbol')
+class Unit:
+    name: str = None
+    circles: List(Circle) = field(default_factory=list)
+    arcs: List(Arc) = field(default_factory=list)
+    polylines: List(Polyline) = field(default_factory=list)
+    rectangles: List(Rectangle) = field(default_factory=list)
+    texts: List(Text) = field(default_factory=list)
+    pins: List(Pin) = field(default_factory=list)
+    unit_name: Named(str) = None
+    _ : SEXP_END = None
+    global_units: list = field(default_factory=list)
+    unit_global: Flag() = False
+    style_global: Flag() = False
+    demorgan_style: int = 1
+    unit_index: int = 1
+    symbol = None
+
+    def __after_parse__(self, parent):
+        self.symbol = parent
+
+        if not (m := re.fullmatch(r'(.*)_([0-9]+)_([0-9]+)', self.name)):
+            raise FormatError(f'Invalid unit name "{self.name}"')
+        sym_name, unit_index, demorgan_style = m.groups()
+        if sym_name != self.symbol.name:
+            raise FormatError(f'Unit name "{self.name}" does not match symbol name "{self.symbol.name}"')
+        self.demorgan_style = int(demorgan_style)
+        self.unit_index = int(unit_index)
+        self.style_global = self._demorgan_style == 0
+        self.unit_global = self.unit_index == 0
+
+    def __before_sexp__(self):
+        self.name = f'{self.symbol.name}_{self.unit_index}_{self.demorgan_style}'
+
+    def __getattr__(self, name):
+        if name.startswith('all_'):
+            name = name[4:]
+            return itertools.chain(getattr(self.global_units, name, []), getattr(self, name, []))
+
+    def pin_stacks(self):
+        stacks = defaultdict(lambda: set())
+        for pin in self.all_pins():
+            stacks[(pin.at.x, pin.at.y)].add(pin)
+        return stacks
+
+
+@sexp_type('symbol')
+class Symbol:
+    name: str = None
+    extends: Named(str) = None
+    power: Wrap(Flag()) = False
+    pin_numbers: OmitDefault(PinNumberSpec) = field(default_factory=PinNumberSpec)
+    pin_names: OmitDefault(PinNameSpec) = field(default_factory=PinNameSpec)
+    in_bom: Named(YesNoAtom()) = True
+    on_board: Named(YesNoAtom()) = True
+    properties: List(Property) = field(default_factory=list)
+    raw_units: List(Unit) = field(default_factory=list)
+    _ : SEXP_END = None
+    styles: {str: {str: Unit}} = None
+    global_units: {str: {str: Unit}} = None
+    library = None
+
+    def __after_parse__(self, parent):
+        self.library = parent
+
+        self.global_units = {}
+        self.styles = {}
+
+        if self.extends:
+            self.in_bom = None
+            self.on_board = None
+
+        self.properties = {prop.name: prop for prop in self.properties}
+        if (prop := self.properties.get('ki_fp_filters')):
+            prop.value = prop.value.split() if prop.value else []
+
+        for unit in self.raw_units:
+            if unit.unit_global or unit.style_global:
+                d = self.global_units.get(unit.demorgan_style, {})
+                d[unit.name] = unit
+                self.global_units[unit.demorgan_style] = d
+
+                for other in self.raw_units:
+                    if other.unit_global or other.style_global or other == unit:
+                        continue
+                    if not (unit.unit_global or other.name == unit.name):
+                        continue
+                    if not (unit.style_global or other.demorgan_style == unit.demorgan_style):
+                        continue
+                    other.global_units.append(unit)
+
+            else:
+                d = self.styles.get(unit.demorgan_style, {})
+                d[unit.name] = unit
+                self.styles[unit.demorgan_style] = d
+
+    def __before_sexp__(self):
+        self.raw_units = ([unit for style in self.global_units.values() for unit in style.values()] +
+                            [unit for style in self.styles.values() for unit in style.values()])
+        if (prop := self.properties.get('ki_fp_filters')):
+            if not isinstance(prop.value, str):
+                prop.value = ' '.join(prop.value)
+        self.properties = list(self.properties.values())
+
+    def default_properties(self):
+        for i, (name, value, hide) in enumerate([
+            ('Reference',       'U',        False),
+            ('Value',           None,       False),
+            ('Footprint',       None,       True),
+            ('Datasheet',       None,       True),
+            ('ki_locked',       None,       True),
+            ('ki_keywords',     None,       True),
+            ('ki_description',  None,       True),
+            ('ki_fp_filters',   None,       False),
+            ]):
+            self.properties[name] = Property(name=name, value=value, id=i, effects=TextEffect(hide=hide))
+
+    def units(self, demorgan_style=None):
+        if self.extends:
+            return self.library[self.extends].units(demorgan_style)
+        else:
+            return self.styles.get(demorgan_style or 'default', {})
+
+    def get_center_rectangle(self, units):
+        # return a polyline for the requested unit that is a rectangle
+        # and is closest to the center
+        candidates = {}
+        # building a dict with floats as keys.. there needs to be a rule against that^^
+        pl_rects = [i.as_polyline() for i in self.rectangles]
+        pl_rects.extend(pl for pl in self.polylines if pl.is_rectangle())
+        for pl in pl_rects:
+            if pl.unit in units:
+                # extract the center, calculate the distance to origin
+                (x, y) = pl.get_center_of_boundingbox()
+                dist = math.sqrt(x * x + y * y)
+                candidates[dist] = pl
+
+        if candidates:
+            # sort the list return the first (smallest) item
+            return candidates[sorted(candidates.keys())[0]]
+        return None
+
+    def is_graphic_symbol(self):
+        return self.extends is None and (
+            not self.pins or self.get_property("Reference").value == "#SYM"
+        )
+
+    def pins_by_name(self, demorgan_style=None):
+        pins = defaultdict(lambda: set())
+        for unit in self.units(demorgan_style):
+            for pin in unit.all_pins:
+                pins[pin.name].add(pin)
+        return pins
+
+    def pins_by_number(self, demorgan_style=None):
+        pins = defaultdict(lambda: set())
+        for unit in self.units(demorgan_style):
+            for pin in unit.all_pins:
+                pins[pin.number].add(pin)
+        return pins
+
+    def __getattr__(self, name):
+        if name.startswith('all_'):
+            return itertools.chain(getattr(unit, name) for unit in self.raw_units)
+
+    def filter_pins(self, name=None, direction=None, electrical_type=None):
+        for pin in self.all_pins:
+            if name and not fnmatch(pin.name, name):
+                continue
+            if direction and not pin.direction in direction:
+                continue
+            if electrical_type and not pin.etype in electical_type:
+                continue
+            yield pin
+
+    def heuristically_small(self):
+        """ Heuristically try to determine whether this is a "small" component like a resistor, capacitor, LED, diode,
+        or transistor etc. When we have at most two pins, or there is no filled rectangle as symbol outline and we have
+        3 or 4 pins, we assume this is a small symbol.
+        """
+        if len(self.all_pins) <= 2:
+            return True
+        if len(self.all_pins) > 4:
+            return False
+        return bool(self.get_center_rectangle(range(self.unit_count)))
+
+
+SUPPORTED_FILE_FORMAT_VERSIONS = [20211014, 20220914]
+@sexp_type('kicad_symbol_lib')
+class Library:
+    _version: Named(int, name='version') = 20211014
+    generator: Named(Atom) = Atom.kicad_library_utils
+    symbols: List(Symbol) = field(default_factory=list)
+    _ : SEXP_END = None
+    original_filename: str = None
+
+    @property
+    def version(self):
+        return self._version
+
+    @version.setter
+    def version(self, value):
+        if value not in SUPPORTED_FILE_FORMAT_VERSIONS:
+            raise FormatError(f'File format version {value} is not supported. Supported versions are {", ".join(map(str, SUPPORTED_FILE_FORMAT_VERSIONS))}.')
+
+    @classmethod
+    def open(cls, filename: str):
+        with open(filename) as f:
+            return cls.parse(f.read())
+
+    def write(self, filename=None):
+        with open(filename or self.original_filename, 'w') as f:
+            f.write(build_sexp(sexp(self)))
+
+
+if __name__ == "__main__":
+    if len(sys.argv) >= 2:
+        a = Library.open(sys.argv[1])
+        print(build_sexp(sexp(a)))
+    else:
+        print("pass a .kicad_sym file please")