Fastener

class Fastener(FastenerSpecification, Feature):
    """
    Represents a fastener as a callout on the drawing specifies it (e.g.
    `3x PEM CLS-M4-2`, `4x DIN 929 M12`, `6x weld stud M6x15`).
    """

    quantity: int = Field(
        ...,
        ge=1,
        description="The number of pieces. Must be at least 1.",
        examples=[3],
    )
    note: Optional[str] = Field(
        None,
        description=(
            "Placement text the callout adds, as written (e.g. `pointing "
            "inward`), if any. It says on which side or in which direction the "
            "fastener is fitted, which matters to the manufacturing step."
        ),
        examples=["pointing inward"],
    )

class FastenerSpecification(BaseModel):
    """
    Describes a fastener: a press-in nut (e.g. `PEM CLS-M4-2`), a weld nut
    (e.g. `DIN 929 M12`), a weld stud (e.g. `M6x15`), a screw (e.g.
    `ISO 4762 M6x20`) and the like.

    The same description is used for a fastener callout on the drawing
    (`Fastener`) and for a row of the bill of material that lists the
    fastener (`BillOfMaterialRow.fastener`), so the two can be matched.
    """

    fastener_type: FastenerType = Field(
        ...,
        description="The kind of fastener, by how it is joined.",
        examples=[FastenerType.PRESS_IN_NUT],
    )
    designation: Optional[str] = Field(
        None,
        description=(
            "The designation of the fastener as written on the drawing, with "
            "spacing normalized (e.g. `PEM CLS-M4-2`, `DIN 929 M12`, "
            "`ISO 4762 M6x20`). None when the drawing names only the kind of "
            "fastener and its thread (e.g. `Einpressmutter M5`)."
        ),
        examples=["PEM CLS-M4-2"],
    )
    standard: Optional[str] = Field(
        None,
        description="The standard the fastener is specified by, if one is named.",
        examples=["DIN 929"],
    )
    manufacturer: Optional[str] = Field(
        None,
        description="The manufacturer, if the designation names one.",
        examples=["PEM"],
    )
    thread: Optional[ThreadUnion] = Field(
        None,
        description=(
            "The thread of one piece of the fastener (e.g. `M4` for "
            "`PEM CLS-M4-2`), if it has one. A pitch that is not written is "
            "the standard coarse pitch."
        ),
    )
    length: Optional[Size] = Field(
        None,
        description=(
            "The length of the fastener, if stated (e.g. `15` in a weld stud "
            "`M6x15`, `20` in `ISO 4762 M6x20`). A manufacturer's code that is "
            "not a length, such as the shank code `2` in `PEM CLS-M4-2`, is "
            "not reported here."
        ),
        examples=[
            Size(
                size_type=SizeType.LINEAR,
                value=Decimal("15"),
                tolerance=None,
                unit="millimeter",
            )
        ],
    )

class FastenerType(str, Enum):
    """Kinds of fastener a drawing or a bill of material names.

    Fastener is meant as in ISO 1891 ("Fasteners - Terminology"): the parts
    that join other parts. The categories follow how the fastener is joined,
    because that decides the manufacturing or assembly step.

    Joined to the component while it is made:

    - PRESS_IN_NUT: a self-clinching or broaching nut pressed into sheet
      metal, e.g. PEM types S, CLS or SP (``PEM CLS-M4-2``), often written
      "Einpressmutter".
    - PRESS_IN_STUD: a self-clinching stud pressed into sheet metal, e.g.
      PEM types FH or FHS (``PEM FH-M4-10``), often written "Einpressbolzen".
    - PRESS_IN_STANDOFF: a self-clinching spacer with a thread or a through
      hole, e.g. PEM types SO or BSO (``PEM SO-M3-8``).
    - WELD_NUT: a nut welded onto the part, e.g. a hexagon weld nut to
      DIN 929 or a square weld nut to DIN 928.
    - WELD_STUD: a threaded stud or pin welded onto the part, e.g. a stud
      for arc stud welding to ISO 13918.
    - THREADED_INSERT: a thread insert set into a hole, e.g. a wire thread
      insert to DIN 8140 or a threaded bushing.
    - RIVET_NUT: a blind rivet nut, set from one side of the part.

    Separate parts of an assembly, as a bill of material lists them:

    - SCREW: a screw or bolt, e.g. ``ISO 4762 M6x20`` or ``ISO 4017 M8x30``.
    - NUT: a nut that is screwed on, e.g. ``ISO 4032 M8``.
    - WASHER: a washer, e.g. ``ISO 7089 8`` or ``DIN 125-A 6.4``.

    - OTHER: a fastener that fits none of the above, such as a pin or a
      rivet. ``designation`` says what it is.
    """

    PRESS_IN_NUT = "PRESS_IN_NUT"
    PRESS_IN_STUD = "PRESS_IN_STUD"
    PRESS_IN_STANDOFF = "PRESS_IN_STANDOFF"
    WELD_NUT = "WELD_NUT"
    WELD_STUD = "WELD_STUD"
    THREADED_INSERT = "THREADED_INSERT"
    RIVET_NUT = "RIVET_NUT"
    SCREW = "SCREW"
    NUT = "NUT"
    WASHER = "WASHER"
    OTHER = "OTHER"