import bpy


def merge_layers(rlayers, obname=None):
    print(f'Merging {len(rlayers)} layers')
    print('->', [r.layer for r in rlayers])
    print()

    if not rlayers:
        return ('ERROR', 'No render layer sent to merge')

    ng = rlayers[0].outputs[0].links[0].to_node
    rlayers.sort(key=lambda x: x.location.y, reverse=True)

    # change colors of those nodes
    color = random_color()
    for n in rlayers:
        n.use_custom_color = True
        n.color = color


    # get inside socket (group input) from outside socket list (should be already ordered)
    
    ## by name
    # for i, inp in enumerate(ng.node_tree.inputs):
    #     if inp.name == 

    # by connection order

    socket_list = []
    grp_sockets = []

    for n in rlayers:
        if n.outputs[0].links[0].to_node != ng:
            print(f'Skip {n.layer}, connect to {n.outputs[0].links[0].to_node} instead of {ng.name}')
            continue
        
        sock_in = n.outputs[0].links[0].to_socket
        for i, s in enumerate(ng.inputs):
            if s == sock_in:
                print(i, s.name)
                socket_list.append(s)
                grp_sockets.append(ng.node_tree.nodes['Group Input'].outputs[i])
                break
    
    # debug
    for inp, grps in zip(socket_list, grp_sockets):
        if inp.name != grps.name:
            print(f'\n! Problem ! : {inp.name}, {grps.name}')
            return

    ## 
    # JUST CREATE ANOTHER GROUP NODE FOR THE MERGE !
    ##


def merge_selected_layers():
    '''Merge command from selected GP layers'''
    ob = bpy.context.object
    layer_names = [l.info for l in ob.data.layers if l.select and not l.hide]
    print("layer_names", layer_names)#Dbg
    
    if len(layer_names) < 2:
        print(f'Should select multiple layers for merging')
        return

    render = bpy.data.scenes.get('Render')
    if render:
        nodes = render.node_tree.nodes
    
    clean_ob_name = bpy.path.clean_name(ob.name)
    rlayers = []
    for l in layer_names:
        ## identifier is clean_name(ob.name).layer_name
        
        idname = f'{clean_ob_name}.{l}'
        
        # check the render layer that have a parent frame
        rlayer = [n for n in nodes if n.type == 'R_LAYERS' and n.layer == idname and n.parent]
        if not rlayer:
            # send to function to generate the rlayer and connect
            # rlayer = creation
            continue

        rlayers.append(rlayer)

    merge_layers(rlayers, obname=clean_ob_name)


def merge_selected_render_layers():
    '''Merge command from selected render layers nodes'''
    render = bpy.data.scenes.get('Render')
    if not render:
        print('No render scene')
        return
    
    nodes = render.node_tree.nodes
    selection = [n for n in nodes if n.select and n.type == 'R_LAYERS']
    
    # should be from the same object:
    assert all(selection[0].layer.split('.')[0] == n.layer.split('.')[0] for n in selection), 'Not every nodes start with the same object'

    # obname = selection[0].layer.split('.')[0]
    merge_layers(selection)




# merge_selected_layers() # function to merge from GP dopesheet

merge_selected_render_layers() # function to merge from nodegroup