From d91cc1235e01061561ae017e47c448a4412f6902 Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 9 Jun 2020 12:38:46 +1000
Subject: [PATCH] Add dependent tasks

---
 .../10459dd24d3d_add_depends_to_tasks.py      | 28 ++++++++++++++++
 src/pyelephant.py                             | 33 +++++++++++++++++--
 2 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 alembic/versions/10459dd24d3d_add_depends_to_tasks.py

diff --git a/alembic/versions/10459dd24d3d_add_depends_to_tasks.py b/alembic/versions/10459dd24d3d_add_depends_to_tasks.py
new file mode 100644
index 0000000..e8704d4
--- /dev/null
+++ b/alembic/versions/10459dd24d3d_add_depends_to_tasks.py
@@ -0,0 +1,28 @@
+"""add depends to tasks
+
+Revision ID: 10459dd24d3d
+Revises: 17946e7038d7
+Create Date: 2020-05-21 11:07:46.953781
+
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision = '10459dd24d3d'
+down_revision = '17946e7038d7'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_table(
+        'depends',
+        sa.Column('first_id', sa.Integer, sa.ForeignKey('tasks.id'), primary_key=True),
+        sa.Column('second_id', sa.Integer, sa.ForeignKey('tasks.id'), primary_key=True)
+    )
+
+
+def downgrade():
+    op.drop_table('depends')
diff --git a/src/pyelephant.py b/src/pyelephant.py
index 1886099..57da621 100755
--- a/src/pyelephant.py
+++ b/src/pyelephant.py
@@ -2,13 +2,24 @@
 
 import sqlalchemy as sa
 import sqlalchemy.ext.declarative.base
+import sqlalchemy.orm
 
 import dateparser
 
+from typing import List
+
+
 ###############################################################################
 Base = sqlalchemy.ext.declarative.declarative_base()
 
 
+depends_association = sa.Table(
+    "depends", Base.metadata,
+    sa.Column('first_id', sa.Integer, sa.ForeignKey('tasks.id'), primary_key=True),
+    sa.Column('second_id', sa.Integer, sa.ForeignKey('tasks.id'), primary_key=True)
+)
+
+
 class Task(Base):
     __tablename__ = "tasks"
 
@@ -18,14 +29,26 @@ class Task(Base):
     due_at = sa.Column(sa.DateTime, nullable=True)
     active = sa.Column(sa.Boolean, server_default=sa.sql.expression.true(), nullable=False)
 
+    depends = sa.orm.relationship(
+        'Task',
+        secondary=depends_association,
+        primaryjoin=id == depends_association.c.first_id,
+        secondaryjoin=id == depends_association.c.second_id
+    )
+
 
 ###############################################################################
-def add(session: sa.orm.Session, title: str, due: str = None):
+def add(session: sa.orm.Session, title: str, due: str = None, depends: List[int] = None):
     if due is not None:
         due = dateparser.parse(due)
 
+    if depends is None:
+        depends = []
+
     obj = Task(title=title, due_at=due)
+    obj.depends.extend([session.query(Task).filter(Task.id == idx).one() for idx in depends])
     session.add(obj)
+
     session.commit()
     show_by_obj(session, obj)
 
@@ -46,7 +69,7 @@ def rm(session: sa.orm.Session, index: int):
 
 # -----------------------------------------------------------------------------
 def show_by_obj(session: sa.orm.Session, obj: Task):
-    print(obj.id, obj.created_at, obj.due_at, obj.active, obj.title)
+    print(obj.id, obj.created_at, obj.due_at, obj.active, obj.title, [i.id for i in obj.depends])
 
 
 # -----------------------------------------------------------------------------
@@ -92,6 +115,12 @@ if __name__ == '__main__':
         add_parser = subparsers.add_parser('add')
         add_parser.set_defaults(func=add, due=None)
         add_parser.add_argument("title", type=str)
+        add_parser.add_argument(
+            "--depends",
+            type=int,
+            nargs="*",
+            help="Task IDs that must be completed before this task"
+        )
         add_parser.add_argument("--due", type=str)
 
         done_parser = subparsers.add_parser('done')