File download from workflow data (#122)

spiffworkflow-backend/src/spiffworkflow_backend/api.yml

@@ -1605,6 +1605,45 @@ paths:
               schema:
                 $ref: "#/components/schemas/Workflow"
 
+  /process-data-file-download/{modified_process_model_identifier}/{process_instance_id}/{process_data_identifier}:
+    parameters:
+      - name: modified_process_model_identifier
+        in: path
+        required: true
+        description: The modified id of an existing process model
+        schema:
+          type: string
+      - name: process_instance_id
+        in: path
+        required: true
+        description: The unique id of an existing process instance.
+        schema:
+          type: integer
+      - name: process_data_identifier
+        in: path
+        required: true
+        description: The identifier of the process data.
+        schema:
+          type: string
+      - name: index
+        in: query
+        required: false
+        description: The optional index of the value if key's value is an array
+        schema:
+          type: integer
+    get:
+      operationId: spiffworkflow_backend.routes.process_api_blueprint.process_data_file_download
+      summary: Download the file referneced in the process data value.
+      tags:
+        - Data Objects
+      responses:
+        "200":
+          description: Fetch succeeded.
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Workflow"
+
   /send-event/{modified_process_model_identifier}/{process_instance_id}:
     parameters:
       - name: modified_process_model_identifier

spiffworkflow-backend/src/spiffworkflow_backend/routes/process_api_blueprint.py

@@ -1,7 +1,9 @@
 """APIs for dealing with process groups, process models, and process instances."""
+import base64
 import json
 from typing import Any
 from typing import Dict
+from typing import Optional
 
 import flask.wrappers
 from flask import Blueprint
@@ -81,10 +83,12 @@ def process_list() -> Any:
     return SpecReferenceSchema(many=True).dump(references)
 
 
-def process_data_show(
+def _process_data_fetcher(
     process_instance_id: int,
     process_data_identifier: str,
     modified_process_model_identifier: str,
+    download_file_data: bool,
+    index: Optional[int] = None,
 ) -> flask.wrappers.Response:
     """Process_data_show."""
     process_instance = _find_process_instance_by_id_or_raise(process_instance_id)
@@ -94,6 +98,26 @@ def process_data_show(
     if process_data_identifier in all_process_data:
         process_data_value = all_process_data[process_data_identifier]
 
+    if process_data_value is not None and index is not None:
+        process_data_value = process_data_value[index]
+
+    if (
+        download_file_data
+        and isinstance(process_data_value, str)
+        and process_data_value.startswith("data:")
+    ):
+        parts = process_data_value.split(";")
+        mimetype = parts[0][4:]
+        filename = parts[1]
+        base64_value = parts[2].split(",")[1]
+        file_contents = base64.b64decode(base64_value)
+
+        return Response(
+            file_contents,
+            mimetype=mimetype,
+            headers={"Content-disposition": f"attachment; filename={filename}"},
+        )
+
     return make_response(
         jsonify(
             {
@@ -105,6 +129,37 @@ def process_data_show(
     )
 
 
+def process_data_show(
+    process_instance_id: int,
+    process_data_identifier: str,
+    modified_process_model_identifier: str,
+) -> flask.wrappers.Response:
+    """Process_data_show."""
+    return _process_data_fetcher(
+        process_instance_id,
+        process_data_identifier,
+        modified_process_model_identifier,
+        False,
+        None,
+    )
+
+
+def process_data_file_download(
+    process_instance_id: int,
+    process_data_identifier: str,
+    modified_process_model_identifier: str,
+    index: Optional[int] = None,
+) -> flask.wrappers.Response:
+    """Process_data_file_download."""
+    return _process_data_fetcher(
+        process_instance_id,
+        process_data_identifier,
+        modified_process_model_identifier,
+        True,
+        index,
+    )
+
+
 # sample body:
 # {"ref": "refs/heads/main", "repository": {"name": "sample-process-models",
 # "full_name": "sartography/sample-process-models", "private": False .... }}

spiffworkflow-backend/src/spiffworkflow_backend/routes/user.py

@@ -17,6 +17,7 @@ from flask import request
 from werkzeug.wrappers import Response
 
 from spiffworkflow_backend.exceptions.api_error import ApiError
+from spiffworkflow_backend.helpers.api_version import V1_API_PATH_PREFIX
 from spiffworkflow_backend.models.user import UserModel
 from spiffworkflow_backend.services.authentication_service import AuthenticationService
 from spiffworkflow_backend.services.authentication_service import (
@@ -58,6 +59,10 @@ def verify_token(
     if not token and "Authorization" in request.headers:
         token = request.headers["Authorization"].removeprefix("Bearer ")
 
+    if not token and "access_token" in request.cookies:
+        if request.path.startswith(f"{V1_API_PATH_PREFIX}/process-data-file-download/"):
+            token = request.cookies["access_token"]
+
     # This should never be set here but just in case
     _clear_auth_tokens_from_thread_local_data()
 

spiffworkflow-backend/src/spiffworkflow_backend/scripts/markdown_file_download_link.py

@@ -0,0 +1,51 @@
+"""Markdown_file_download_link."""
+from typing import Any
+from urllib.parse import unquote
+
+from flask import current_app
+
+from spiffworkflow_backend.models.process_model import ProcessModelInfo
+from spiffworkflow_backend.models.script_attributes_context import (
+    ScriptAttributesContext,
+)
+from spiffworkflow_backend.scripts.script import Script
+
+
+class GetMarkdownFileDownloadLink(Script):
+    """GetMarkdownFileDownloadLink."""
+
+    @staticmethod
+    def requires_privileged_permissions() -> bool:
+        """We have deemed this function safe to run without elevated permissions."""
+        return False
+
+    def get_description(self) -> str:
+        """Get_description."""
+        return """Returns a string which is a string in markdown format."""
+
+    def run(
+        self,
+        script_attributes_context: ScriptAttributesContext,
+        *_args: Any,
+        **kwargs: Any,
+    ) -> Any:
+        """Run."""
+        # example input:
+        #  "data:application/pdf;name=Harmeet_1234.pdf;base64,JV...."
+        process_data_identifier = kwargs["key"]
+        parts = kwargs["file_data"].split(";")
+        file_index = kwargs["file_index"]
+        label = unquote(parts[1].split("=")[1])
+        process_model_identifier = script_attributes_context.process_model_identifier
+        modified_process_model_identifier = (
+            ProcessModelInfo.modify_process_identifier_for_path_param(
+                process_model_identifier
+            )
+        )
+        process_instance_id = script_attributes_context.process_instance_id
+        url = current_app.config["SPIFFWORKFLOW_BACKEND_URL"]
+        url += f"/v1.0/process-data-file-download/{modified_process_model_identifier}/"
+        f"{process_instance_id}/{process_data_identifier}?index={file_index}"
+        link = f"[{label}]({url})"
+
+        return link