import bpy
import bmesh
import operator
import time
import math
from mathutils import Vector


image_material_prefix = "TT_checker_"


# Return all faces of selected objects or only selected faces
def get_selected_object_faces():
    object_faces_indexies = {}

    previous_mode = bpy.context.object.mode

    if bpy.context.object.mode == 'EDIT':
        # Only selected Mesh faces
        obj = bpy.context.active_object
        if obj.type == 'MESH' and obj.data.uv_layers:
            bm = bmesh.from_edit_mesh(obj.data)
            bm.faces.ensure_lookup_table()
            object_faces_indexies[obj] = [face.index for face in bm.faces if face.select]
    else:
        # Selected objects with all faces each
        selected_objects = [obj for obj in bpy.context.selected_objects]
        for obj in selected_objects:
            if obj.type == 'MESH' and obj.data.uv_layers:
                bpy.ops.object.mode_set(mode='OBJECT')
                bpy.ops.object.select_all(action='DESELECT')
                bpy.context.view_layer.objects.active = obj
                obj.select_set( state = True, view_layer = None)

                bpy.ops.object.mode_set(mode='EDIT')
                bm = bmesh.from_edit_mesh(obj.data)
                bm.faces.ensure_lookup_table()
                object_faces_indexies[obj] = [face.index for face in bm.faces]

    bpy.ops.object.mode_set(mode=previous_mode)

    return object_faces_indexies



def get_object_texture_image(obj):

    previous_mode = bpy.context.active_object.mode
    bpy.ops.object.mode_set(mode='OBJECT')

    # Search in material & texture slots
    for slot_mat in obj.material_slots:

        if slot_mat.material:

            # Check for traditional texture slots in material
            if slot_mat.material.texture_paint_images:
                active_slot = slot_mat.material.paint_active_slot
                if slot_mat.material.texture_paint_images[active_slot]:
                    return slot_mat.material.texture_paint_images[active_slot]

            # Check if material uses Nodes
            if hasattr(slot_mat.material , 'node_tree'):
                if slot_mat.material.node_tree:
                    for node in slot_mat.material.node_tree.nodes:
                        if type(node) is bpy.types.ShaderNodeTexImage:
                            if node.image:
                                return node.image

    

    return None



def image_resize(image, size_x, size_y):
    if image and image.source == 'FILE' or image.source == 'GENERATED':
        image.generated_width = int(size_x)
        image.generated_height = int(size_y)
        image.scale( int(size_x), int(size_y) )
    
    

def checker_images_cleanup():
    # Clean up unused images
    for image in bpy.data.images:
        if image and image_material_prefix in image.name:
            # Remove unused images
            if not image.users:
                image.user_clear()
                bpy.data.images.remove(image)
                return

            # Check if name missmatches size
            name = get_checker_name(image.generated_type , image.size[0], image.size[1])
            if image.name != name:
                # In cycles find related material as well
                if image.name in bpy.data.materials:
                    bpy.data.materials[image.name].name = name
                image.name = name

    for material in bpy.data.materials:
        if material and image_material_prefix in material.name:
            # Remove unused images
            if not material.users:
                material.user_clear()
                bpy.data.materials.remove(material)



def get_checker_name(mode, size_x, size_y):
    return (image_material_prefix+"{1}x{2}_{0}").format(mode, size_x, size_y)



def get_area_triangle_uv(A,B,C, size_x, size_y):
    scale_x = size_x / max(size_x, size_y)
    scale_y = size_y / max(size_x, size_y)
    A.x/=scale_x
    B.x/=scale_x
    C.x/=scale_x
    
    A.y/=scale_y
    B.y/=scale_y
    C.y/=scale_y

    return get_area_triangle(A,B,C)


def get_area_triangle(A,B,C):
    # Heron's formula: http://www.1728.org/triang.htm
    # area = square root (s • (s - a) • (s - b) • (s - c))
    a = (B-A).length
    b = (C-B).length
    c = (A-C).length
    s = (a+b+c)/2

    # Use abs(s-a) for values that otherwise generate negative values e.g. pinched UV verts, otherwise math domain error
    return math.sqrt(s * abs(s-a) * abs(s-b) * abs(s-c))