From fa789984f4c66b6e0c27a46550c4f6b40a492357 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sergio=20Mart=C3=ADnez=20Portela?=
 <sergio@codigoparallevar.com>
Date: Sat, 10 Jun 2023 15:55:43 +0200
Subject: [PATCH] Implement long-operation cache.

---
 scripts/gen_centered_graph.py |  3 +-
 scripts/ops_cache.py          | 75 +++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+), 2 deletions(-)

diff --git a/scripts/gen_centered_graph.py b/scripts/gen_centered_graph.py
index 8176e16..fce246e 100644
--- a/scripts/gen_centered_graph.py
+++ b/scripts/gen_centered_graph.py
@@ -5,10 +5,9 @@ import ops_cache
 import copy
 import tempfile
 
-# TODO: Cache results
 # TODO: Properly render outgouing links
 
-# @ops_cache()
+@ops_cache.cache
 def gen(headline_id, graph):
     reference_node = headline_id
 
diff --git a/scripts/ops_cache.py b/scripts/ops_cache.py
index e69de29..45c1431 100644
--- a/scripts/ops_cache.py
+++ b/scripts/ops_cache.py
@@ -0,0 +1,75 @@
+import sqlite3
+import json
+import logging
+from typing import Optional
+import xdg
+import os
+import datetime
+
+CACHE_DB: Optional[sqlite3.Connection] = None
+CACHE_PATH = os.path.join(xdg.xdg_cache_home(), 'codigoparallevar', 'ops.sqlite3')
+
+def init_db():
+    global CACHE_DB
+
+    os.makedirs(os.path.dirname(CACHE_PATH), exist_ok=True)
+    CACHE_DB = sqlite3.connect(CACHE_PATH)
+
+    cur = CACHE_DB.cursor()
+    cur.execute('''CREATE TABLE IF NOT EXISTS ops(
+        in_val TEXT PRIMARY KEY,
+        code TEXT,
+        out_val TEXT,
+        added_at DateTime
+    );
+    ''')
+    CACHE_DB.commit()
+    cur.close()
+
+def query_cache(in_val, code):
+    if CACHE_DB is None:
+        init_db()
+    assert CACHE_DB is not None
+    cur = CACHE_DB.cursor()
+    cur.execute('''SELECT out_val FROM ops WHERE in_val = ? AND code = ?''', (in_val, code))
+
+    # Should return only one result, right? 🤷
+    results = cur.fetchall()
+    assert len(results) < 2
+    if len(results) == 0:
+        return None
+    else:
+        return results[0][0]
+
+def save_cache(in_val, code, out_val):
+    if CACHE_DB is None:
+        init_db()
+    assert CACHE_DB is not None
+    cur = CACHE_DB.cursor()
+    cur.execute('''
+    INSERT INTO ops(in_val, code, out_val, added_at)
+    VALUES (?, ?, ?, ?);''',
+                (in_val, code, out_val, datetime.datetime.now()))
+    CACHE_DB.commit()
+    cur.close()
+
+def cache(fun):
+    fun_code = fun.__code__.co_code.decode('latin-1')
+    def wrapped(*kargs, **kwargs):
+        in_val = json.dumps({
+            'kargs': kargs,
+            'kwargs': kwargs,
+            'fun_code': fun_code,
+        })
+
+        cache_result = query_cache(in_val, fun_code)
+        found_in_cache = cache_result is not None
+        if not found_in_cache:
+            out_val = fun(*kargs, **kwargs)
+            save_cache(in_val, fun_code, out_val)
+        else:
+            out_val = cache_result
+
+        logging.info("{} bytes in, {} bytes out (in_cache: {})".format(len(in_val), len(out_val), found_in_cache))
+        return out_val
+    return wrapped