From 636ac88daf2a599b3b7dfc94180f58b8c62cb81f Mon Sep 17 00:00:00 2001
From: thematdev <thematdev@gmail.com>
Date: Wed, 22 Sep 2021 14:29:02 +0300
Subject: [PATCH] Added lockfile system

---
 app/__init__.py     | 35 ++++++++++++++++++++++++++++++-----
 app/hash_manager.py | 17 +++++++++++++++++
 2 files changed, 47 insertions(+), 5 deletions(-)
 create mode 100644 app/hash_manager.py

diff --git a/app/__init__.py b/app/__init__.py
index 69fbc15..5632ca3 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -1,7 +1,8 @@
-from flask import Flask, url_for, render_template
+from flask import Flask, url_for, render_template, abort
 import os
 import json
 from app.config import PANDOC_LINK, PANDOC_PATH
+from app.hash_manager import hash_file_sha512
 import subprocess
 
 app = Flask(__name__)
@@ -24,17 +25,41 @@ def dated_url_for(endpoint, **values):
     return url_for(endpoint, **values)
 
 
+def render_page(page):
+    path = f'{PANDOC_PATH}/{page}'
+    if not os.path.exists(f'{path}'):
+        raise Exception("Page doesn't exist!")
+    in_filename = f'{path}/main.md'
+    out_filename = f'{path}/render.html'
+    os.system(f'pandoc {in_filename} --to html --mathjax --output {out_filename}')
+    print('Creating lock file')
+    os.system(f'echo {hash_file_sha512(in_filename)} > {out_filename}.lock')
+
+
 @app.route(f'/{PANDOC_LINK}/<page>')
 def get_pandoc_page(page):
-    with open(f'{PANDOC_PATH}/{page}/config.json') as f:
+    path = f'{PANDOC_PATH}/{page}'
+    if not os.path.exists(f'{path}'):
+        abort(404)
+    with open(f'{path}/config.json') as f:
         data = json.loads(f.read())
-    filename = f'{PANDOC_PATH}/{page}/main.md'
-    inserted = subprocess.Popen(f'pandoc {filename} -t html --mathjax', shell=True, stdout=subprocess.PIPE).stdout.read().decode('utf-8')
+    if not os.path.exists(f'{path}/render.html') or not os.path.exists(f'{path}/render.html.lock'):
+        print('Rendered page or lockfile for {page} does not exist! Rendering {page}')
+        render_page(page)
+    else:
+        with open(f'{path}/render.html.lock', 'r') as f:
+            rendered_hash = f.read().strip()
+        current_hash = hash_file_sha512(f'{path}/main.md')
+        if rendered_hash != current_hash:
+            print(f'CURRENT: {current_hash}, RENDERED: {rendered_hash}')
+            print('Integrity test failed, rendering {page}!')
+            render_page(page)
     template = data['template']
+    with open(f'{path}/render.html', 'r') as f:
+        inserted = f.read()
     return render_template(template, markdown=inserted)
 
 
 @app.route('/')
 def index():
     return render_template('index.html')
-
diff --git a/app/hash_manager.py b/app/hash_manager.py
new file mode 100644
index 0000000..0f3acd7
--- /dev/null
+++ b/app/hash_manager.py
@@ -0,0 +1,17 @@
+import hashlib
+
+
+BUF_SZ = 4096
+
+
+def hash_file_sha512(filename):
+    res = hashlib.sha512()
+    with open(filename, 'rb') as f:
+        data = f.read(BUF_SZ)
+        while data:
+            res.update(data)
+            data = f.read(BUF_SZ)
+    return res.hexdigest()
+
+
+