import bpy
from bpy.props import FloatProperty
from bpy.types import Context, Operator, Panel


class ArmEditOperator:
    @classmethod
    def poll(cls, context: Context):
        return (
            context.active_object
            and context.active_object.type == 'ARMATURE'
            and context.active_bone
            and context.mode == 'EDIT_ARMATURE'
        )


class ARMATURE_OT_ReadBoneLength(ArmEditOperator, Operator):
    """Make length property equal to actual bone length"""
    bl_idname = "armature.read_bone_length"
    bl_label = "Read Bone Length"
    bl_options = {'UNDO'}

    def execute(self, context):
        context.active_bone.bbone_y = context.active_bone.length
        return {'FINISHED'}


class ARMATURE_OT_MakeBoneSquare(ArmEditOperator, Operator):
    """Make bone's width and depth equal to it's length"""
    bl_idname = "armature.make_bone_square"
    bl_label = "Make Bone Square"
    bl_options = {'UNDO'}

    def execute(self, context):
        context.active_bone.bbone_x = context.active_bone.bbone_z = context.active_bone.length * 0.5
        return {'FINISHED'}


class VIEW3D_PT_bone_size(Panel):
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_label = "Bone Size"
    bl_options = {'DEFAULT_CLOSED'}

    @classmethod
    def poll(cls, context: Context):
        scene = context.space_data
        ob = context.active_object
        return scene and ob and ob.type == 'ARMATURE' and ob.mode == 'EDIT'

    def draw(self, context: Context):
        layout = self.layout

        col = layout.column()
        col.prop(context.active_bone, "bbone_x", text="Bone Width")
        col.prop(context.active_bone, "bbone_z", text="Bone Depth")
        sub = col.row(align=True)
        sub.operator(ARMATURE_OT_ReadBoneLength.bl_idname, icon="COPYDOWN", text="")
        sub.prop(context.active_bone, "bbone_y", text="Bone Length")
        col.operator(ARMATURE_OT_MakeBoneSquare.bl_idname, icon="MESH_PLANE")


def update_length(self, context) -> None:
    context.active_bone.length = self.bbone_y


def register():
    bpy.types.EditBone.bbone_y = FloatProperty(
        name="B-Bone Display Y Length",
        description="B-Bone Y size",
        default=1.0,
        min=0.0,
        soft_min=0.001,
        step=10,
        precision=3,
        options={'HIDDEN'},
        update=update_length,
    )
    bpy.utils.register_class(ARMATURE_OT_ReadBoneLength)
    bpy.utils.register_class(ARMATURE_OT_MakeBoneSquare)
    bpy.utils.register_class(VIEW3D_PT_bone_size)


def unregister():
    bpy.utils.unregister_class(VIEW3D_PT_bone_size)
    bpy.utils.unregister_class(ARMATURE_OT_MakeBoneSquare)
    bpy.utils.unregister_class(ARMATURE_OT_ReadBoneLength)
    del bpy.types.EditBone.bbone_y


register()