import bpy

from . import utils
from bpy_extras.view3d_utils import location_3d_to_region_2d

def is_stroke_in_view(stroke, matrix, region, region_3d):
    ## for optimization, use first and last
    region_width = region.width
    region_height = region.height
    point_list = [stroke.points[0], stroke.points[-1]]
    # point_list = stroke.points # whole points
    
    coord_list = [matrix @ point.position for point in point_list]

    for coord in coord_list:
        # Convert 3D coordinates to 2D screen coordinates
        screen_coord = location_3d_to_region_2d(region, region_3d, coord)
        if screen_coord is None:
            continue
        # Check if the point is within the viewport bounds
        if 0 <= screen_coord.x <= region_width and 0 <= screen_coord.y <= region_height:
            ## one point in view, in view
            return True
    
    return False

class GP_OT_delete_view_bound(bpy.types.Operator):
    bl_idname = "grease_pencil.delete_view_bound"
    bl_label = "Delete View Bound"
    bl_description = "Delete all selected strokes / points only if there are in view (current viewport region)\
        \nnote: does not work in multiframe yet)"
    bl_options = {'REGISTER', 'UNDO'}

    # def invoke(self, context, event):
    ## TODO: add scope (default to automatic)
    ## TODO: add option for normal delete (currenly only dissolve), probably another operator.

    @classmethod
    def poll(cls, context):
        return context.mode == 'EDIT_GREASE_PENCIL'

    def execute(self, context):
        gp = context.grease_pencil
        if not gp:
            self.report({'ERROR'}, "No Grease Pencil object found")
            return {'CANCELLED'}
        
        ob = context.object
        if not ob or ob.type != 'GREASEPENCIL':
            self.report({'ERROR'}, "Active object is not a Grease Pencil object")
            return {'CANCELLED'}

        select_mode = context.scene.tool_settings.gpencil_selectmode_edit
        matrix_world = ob.matrix_world.copy()

        ## only visibile and unlocked layer in active GP object
        layers = [l for l in gp.layers if not l.hide and not l.lock]

        region = context.region
        region_3d = context.space_data.region_3d        

        removed_ct = 0
        avoid_ct = 0
        for layer in layers:
            if context.scene.tool_settings.use_grease_pencil_multi_frame_editing:
                ## multiframe, affect all selected frames and active frame
                target_frames = [f for f in layer.frames if f.select or f == layer.current_frame()]
            else:
                ## Only active frame
                current = layer.current_frame()
                if not current:
                    continue
                target_frames = [current]

            for frame in target_frames:
                drawing = frame.drawing
                if not drawing or not drawing.strokes:
                    continue

                stroke_indices_to_delete = []
                ## List comprehention version (For stroke mode only)
                # stroke_indices_to_delete = [sidx for sidx, stroke in enumerate(drawing.strokes) if stroke.select and is_stroke_in_view(stroke, matrix_world, region, region_3d)]
                for sid, stroke in enumerate(drawing.strokes):
                    if not stroke.select:
                        continue
                    
                    # Check if the stroke is within the view bounds
                    if not is_stroke_in_view(stroke, matrix_world, region, region_3d):
                        avoid_ct += 1
                        continue

                    ## No need for further check if we are in stroke mod (direct delete)
                    if select_mode == 'STROKE':
                        stroke_indices_to_delete.append(sid)
                        removed_ct += 1
                        continue
                    
                    ## --- Handle points ---

                    ## remove points, only Dissolve for now.
                    select_count = len([p for p in stroke.points if p.select])
                    if select_count == len(stroke.points):
                        ## Mark as full delete and go next
                        stroke_indices_to_delete.append(sid)
                        continue


                    ## Make a copy of deselected points attributes
                    point_attrs = []
                    for p in stroke.points:
                        if p.select:
                            continue
                        point_attrs.append([p.position.copy(), p.rotation, p.radius, p.opacity])

                    ## remove as many points as select_count
                    stroke.remove_points(select_count)
                    
                    ## re-assign attributes in order
                    for i, p in enumerate(stroke.points):
                        if i < len(point_attrs):
                            p.position = point_attrs[i][0]
                            p.rotation = point_attrs[i][1]
                            p.radius = point_attrs[i][2]
                            p.opacity = point_attrs[i][3]
                        p.select = False  # Deselect all points after processing
                    
                    removed_ct += 1
                    ## End of stroke loop (here either part if the stroke is deleted or marked for deletion )

                if stroke_indices_to_delete:
                    # print(f'layer {layer.name} : delete {len(stroke_indices_to_delete)} strokes')
                    drawing.remove_strokes(indices=stroke_indices_to_delete)

        if removed_ct and avoid_ct:
            self.report({'INFO'}, f"Skipped {avoid_ct} out of view")
        elif not removed_ct and not avoid_ct:
            self.report({'WARNING'}, "Nothing to Delete")
        elif not removed_ct and avoid_ct:
            self.report({'WARNING'}, "All selected strokes are out of view")

        return {'FINISHED'}


def draw_delete_view_bound_ui(self, context):
    layout = self.layout
    layout.operator('grease_pencil.delete_view_bound', text='Delete View bound', icon='LOCKVIEW_ON') # RESTRICT_VIEW_ON


classes = (
    # GP_OT_delete_strokes_view_bound,
    # GP_OT_delete_points_view_bound,
    GP_OT_delete_view_bound,
)

def register():
    if bpy.app.background:
        return

    for cl in classes:
        bpy.utils.register_class(cl)
    bpy.types.VIEW3D_MT_edit_greasepencil_delete.append(draw_delete_view_bound_ui)

    ## make scene property for empty key preservation and bake movement for layers...
    # register_keymaps()

def unregister():
    if bpy.app.background:
        return

    bpy.types.VIEW3D_MT_edit_greasepencil_delete.remove(draw_delete_view_bound_ui)
    # unregister_keymaps()
    for cl in reversed(classes):
        bpy.utils.unregister_class(cl)