"""
Basic FileHandler for Operator that imports multiple files
----------------------------------------------------------

Also operators can be invoked with multiple files from 'drag-and-drop',
but for this it is required to define the following properties:

.. code-block:: python

    directory: StringProperty(subtype='FILE_PATH', options={'SKIP_SAVE', 'HIDDEN'})
    files: CollectionProperty(type=bpy.types.OperatorFileListElement, options={'SKIP_SAVE', 'HIDDEN'})

These ``directory`` and ``files`` properties now will be used by the
``FileHandler`` to set 'drag-and-drop' filepath data.

Additional properties can also be shown in a popup dialog by using
``invoke_popup()`` from ``ImportHelper``.

"""

import bpy
from bpy_extras.io_utils import ImportHelper
from mathutils import Vector


class ShaderScriptImport(bpy.types.Operator, ImportHelper):
    """Test importer that creates scripts nodes from .txt files"""
    bl_idname = "shader.script_import"
    bl_label = "Import a text file as a script node"

    # This operator can import multiple .txt files, we need the following directory and files
    # properties that the file handler will use to set files path data.
    directory: bpy.props.StringProperty(subtype='FILE_PATH', options={'SKIP_SAVE', 'HIDDEN'})
    files: bpy.props.CollectionProperty(type=bpy.types.OperatorFileListElement, options={'SKIP_SAVE', 'HIDDEN'})

    set_label: bpy.props.BoolProperty(name="Set Label", default=False)

    @classmethod
    def poll(cls, context):
        return (context.region and context.region.type == 'WINDOW'
                and context.area and context.area.ui_type == 'ShaderNodeTree'
                and context.object and context.object.type == 'MESH'
                and context.material)

    def execute(self, context):
        """The directory property needs to be set."""
        if not self.directory:
            return {'CANCELLED'}
        x = 0.0
        y = 0.0
        for file in self.files:
            # Calls to the operator can set unfiltered file names,
            # ensure the file extension is .txt
            if file.name.endswith(".txt"):
                node_tree = context.material.node_tree
                text_node = node_tree.nodes.new(type="ShaderNodeScript")
                text_node.mode = 'EXTERNAL'
                import os
                filepath = os.path.join(self.directory, file.name)
                text_node.filepath = filepath
                text_node.location = Vector((x, y))
                if self.set_label:
                    text_node.label = file.name
                x += 20.0
                y -= 20.0
        return {'FINISHED'}

    def invoke(self, context, event):
        """Use ImportHelper's invoke_popup() to handle the invocation.

        If the operator is called by the file handler, the `directory` and `files` properties are set
        and additional properties such as `set_label` are shown in a popup.
        Otherwise, the file select window is invoked.

        This depends on setting `options={'SKIP_SAVE'}` to the properties options to avoid reusing
        filepath data between operator calls.

        """
        return self.invoke_popup(context)


class SHADER_FH_script_import(bpy.types.FileHandler):
    bl_idname = "SHADER_FH_script_import"
    bl_label = "File handler for shader script node import"
    bl_import_operator = "shader.script_import"
    bl_file_extensions = ".txt"

    @classmethod
    def poll_drop(cls, context):
        return (context.region and context.region.type == 'WINDOW'
                and context.area and context.area.ui_type == 'ShaderNodeTree')


bpy.utils.register_class(ShaderScriptImport)
bpy.utils.register_class(SHADER_FH_script_import)