import math

import bpy
from bpy.props import EnumProperty, IntProperty

HU_TO_METERS_RATIO = 0.025  # 1hu = 2.5cm
GRID_SUBDIVISIONS = 8


class VIEW3D_OT_ResetGrid(bpy.types.Operator):
    """Reset grid settings to defaults"""
    bl_idname = "screen.reset_grid"
    bl_label = "Reset Grid"
    bl_options = {'UNDO'}

    def execute(self, context):
        context.space_data.grid_lines = 16
        context.space_data.grid_scale = 1.0
        context.space_data.grid_subdivisions = 10
        return {'FINISHED'}


class VIEW3D_PT_grid_level(bpy.types.Panel):
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'UI'
    bl_label = "Grid Level"

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

        row = layout.row()
        row.prop(context.scene, "grid_type", expand=True)

        col = layout.column()
        if context.scene.grid_type == 'HAMMER':
            col.prop(context.scene, "grid_hu")

            grid_size = pow(2, context.scene.grid_hu)

            split = col.split(align=True)
            col_l = split.column()
            col_l.alignment = 'RIGHT'
            col_l.label("Hammer Units:")
            col_l.label("Meters:")
            col_r = split.column()
            col_r.label("%i hu" % grid_size)
            col_r.label("%.3f m" % (grid_size * HU_TO_METERS_RATIO))

        elif context.scene.grid_type == 'POWEROF2':
            col.prop(context.scene, "grid_po2")

        layout.operator(VIEW3D_OT_ResetGrid.bl_idname)


def update_grid_hu(self, context) -> None:
    grid_size = pow(2, self.grid_hu)
    context.space_data.grid_lines = max(3, math.ceil(1024 / grid_size))
    context.space_data.grid_scale = grid_size * HU_TO_METERS_RATIO
    context.space_data.grid_subdivisions = GRID_SUBDIVISIONS


def update_grid_po2(self, context) -> None:
    context.space_data.grid_lines = max(3, pow(2, self.grid_po2 + 5))
    context.space_data.grid_scale = 1 / pow(2, self.grid_po2)
    context.space_data.grid_subdivisions = GRID_SUBDIVISIONS


def update_type(self, context) -> None:
    if self.grid_type == 'HAMMER':
        update_grid_hu(self, context)
    elif self.grid_type == 'POWEROF2':
        update_grid_po2(self, context)


def register():
    bpy.types.Scene.grid_type = EnumProperty(
        items=(
            ('HAMMER', "Hammer Units", "Main basic settings"),
            ('POWEROF2', "Power Of 2", "Armature-related settings"),
        ),
        name="Grid type",
        description="",
        update=update_type,
    )
    bpy.types.Scene.grid_hu = IntProperty(
        name="Grid level",
        description="Hammer Units grid level",
        min=0,
        max=9,
        default=6,
        update=update_grid_hu,
    )
    bpy.types.Scene.grid_po2 = IntProperty(
        name="Grid divisions",
        description="Grid divisions in power of 2",
        min=-4,
        max=4,
        default=0,
        update=update_grid_po2,
    )
    bpy.utils.register_class(VIEW3D_OT_ResetGrid)
    bpy.utils.register_class(VIEW3D_PT_grid_level)


def unregister():
    bpy.utils.unregister_class(VIEW3D_PT_grid_level)
    bpy.utils.register_class(VIEW3D_OT_ResetGrid)
    del bpy.types.Scene.grid_po2
    del bpy.types.Scene.grid_hu
    del bpy.types.Scene.grid_type


register()