thrimshim changes for modified

would be ideal to check all args to see if any don't match (and refuse to modify in that case)
but eh too much work to properly normalise.

DATABASE.md

@@ -163,3 +163,4 @@ columns                    | type                                 | role
 `editor`                   | `TEXT`                               | state       | Email address of the last editor; corresponds to an entry in the `editors` table. Only set when state is not `UNEDITED`.
 `edit_time`                | `TIMESTAMP`                          | state       | Time of the last edit. Only set when state is not `UNEDITED`.
 `upload_time`              | `TIMESTAMP`                          | state       | Time when video state is set to `DONE`. Only set when state is `DONE`.
+`last_modified`            | `TIMESTAMP`                          | state       | Time when video state was last set to `MODIFIED`, or NULL if it has never been. Only used for diagnostics.

thrimshim/thrimshim/main.py

@@ -3,8 +3,6 @@ from functools import wraps
 import json
 import logging
 import re
-import signal
-import sys
 
 import argh
 import flask
@@ -213,6 +211,12 @@ def update_row(ident, editor=None):
 		'sheet_name', 'event_start', 'event_end',
 		'category', 'description', 'notes', 'tags',
 	]
+	# These columns may be modified when a video is in state 'DONE',
+	# and are a subset of edit_columns.
+	modifiable_columns = [
+		'video_title', 'video_description', 'video_tags',
+	]
+	assert set(modifiable_columns) - set(edit_columns) == set()
 
 	# Check vital edit columns are in new_row
 	wanted = set(non_null_columns + ['state'] + sheet_columns)
@@ -274,7 +278,10 @@ def update_row(ident, editor=None):
 		return 'Row {} not found'.format(ident), 404
 	assert old_row['id'] == ident
 
-	if old_row['state'] not in ['UNEDITED', 'EDITED', 'CLAIMED']:
+	if new_row['state'] == 'MODIFIED':
+		if old_row['state'] not in ['DONE', 'MODIFIED']:
+			return 'Video is in state {} and cannot be modified'.format(old_row['state']), 403
+	elif old_row['state'] not in ['UNEDITED', 'EDITED', 'CLAIMED']:
 		return 'Video already published', 403
 
 	# check whether row has been changed in the sheet since editing has begun
@@ -293,6 +300,27 @@ def update_row(ident, editor=None):
 	if changes and not override_changes:
 		return 'Sheet columns have changed since editing has begun. Please review changes\n' + changes, 409
 
+	if new_row['state'] == 'MODIFIED':
+		# Modifying published rows is more limited, we ignore all other fields.
+		for column in set(modifiable_columns) & set(non_null_columns):
+			if new_row[column] is None:
+				missing.append(column)
+		if missing:
+			return 'Fields {} must be non-null for modified video'.format(', '.join(missing)), 400
+		build_query = sql.SQL("""
+			UPDATE events
+			SET last_modified = NOW(), error = NULL, state = 'MODIFIED', {}
+			WHERE id = %(id)s AND state IN ('DONE', 'MODIFIED')
+		""").format(sql.SQL(", ").join(
+			sql.SQL("{} = {}").format(
+				sql.Identifier(column), database.get_column_placeholder(column),
+			) for column in modifiable_columns
+		))
+		result = database.query(conn, build_query, id=ident, **new_row)
+		if result.rowcount != 1:
+			return 'Video changed state while we were updating - maybe it was reset?', 403
+
+	else:
 		# handle state columns
 		if new_row['state'] == 'EDITED':
 			missing = []
@@ -386,7 +414,8 @@ def reset_row(ident, editor=None):
 	query = """
 		UPDATE events 
 		SET state='UNEDITED', error = NULL, video_id = NULL, video_link = NULL,
-			uploader = NULL, editor = NULL, edit_time = NULL, upload_time = NULL
+			uploader = NULL, editor = NULL, edit_time = NULL, upload_time = NULL,
+			last_modified = NULL
 		WHERE id = %s {}
 	""".format(
 		"" if force else "AND state IN ('UNEDITED', 'EDITED', 'CLAIMED')",