import bpy
import bmesh
import operator
from mathutils import Vector
from collections import defaultdict
from math import pi


class op(bpy.types.Operator):
    bl_idname = "uv.textools_uv_channel_swap"
    bl_label = "Move UV Channel"
    bl_description = "Move UV channel up or down"
    bl_options = {'REGISTER', 'UNDO'}

    is_down : bpy.props.BoolProperty(default=False)

    @classmethod
    def poll(cls, context):
        if bpy.context.active_object == None:
            return False
        if bpy.context.active_object.type != 'MESH':
            return False
        if len(bpy.context.object.data.uv_layers) <= 1:
            return False
        return True


    def execute(self, context):
        uv_layers = bpy.context.object.data.uv_layers

        if uv_layers.active_index == 0 and not self.is_down:
            return {'FINISHED'}
        elif uv_layers.active_index == len(uv_layers)-1 and self.is_down:
            return {'FINISHED'}

        def get_index(name):
            return ([i for i in range(len(uv_layers)) if uv_layers[i].name == name])[0]

        def move_bottom(name):
            # Set index
            uv_layers.active_index = get_index(name)
            # Copy (to bottom)
            bpy.ops.mesh.uv_texture_add()
            # Delete previous
            uv_layers.active_index = get_index(name)
            bpy.ops.mesh.uv_texture_remove()
            # Rename new
            uv_layers.active_index = len(uv_layers)-1
            uv_layers.active.name = name

        count = len(uv_layers)

        index_A = uv_layers.active_index
        index_B = index_A + (1 if self.is_down else -1)

        if not self.is_down:
            # Move up
            for n in [uv_layers[i].name for i in range(index_B, count) if i != index_A]:
                move_bottom(n)
            bpy.context.scene.texToolsSettings.uv_channel = str(index_B)

        elif self.is_down:
            # Move down
            for n in [uv_layers[i].name for i in range(index_A, count) if i != index_B]:
                move_bottom(n)
            bpy.context.scene.texToolsSettings.uv_channel = str(index_B)

        return {'FINISHED'}

bpy.utils.register_class(op)