📊 Diff, Code Review & Sequence Diagrams

--- a/network_config.py
+++ b/network_config.py
@@ -15,10 +15,12 @@ def configure_interface(device, interface):
     device.connect()
     
     # Configure interface
-    config = f"interface {interface}\n"
-    config += "ip address 192.168.1.1 255.255.255.0\n"
-    config += "no shutdown"
+    config = [
+        f"interface {interface}",
+        "ip address 192.168.1.1 255.255.255.0",
+        "description Configured by automation",
+        "no shutdown"
+    ]
     
-    device.send_config(config)
+    device.send_config_set(config)
     device.disconnect()

# INTERPRETATION:
# - File: network_config.py (modified)
# - Function: configure_interface()
# - Lines affected: 15-25 (hunk starting at line 15)
#
# Changes Made:
# 1. REMOVED: String concatenation for config (lines 18-20)
#    - Old: config = f"interface..." + "ip address..." + "no shutdown"
# 2. ADDED: List-based configuration (lines 18-23)
#    - New: config = ["interface...", "ip address...", "description...", "no shutdown"]
# 3. ADDED: Description line for documentation
# 4. CHANGED: Method name from send_config() to send_config_set()
#    - This accepts list instead of string
#
# Reason: More robust configuration handling

@@ -15,10 +15,12 @@ def configure_interface(device, interface):

BREAKDOWN:
  -15,10    Old file: Starting at line 15, showing 10 lines
  +15,12    New file: Starting at line 15, showing 12 lines
  
INTERPRETATION:
  - The change starts at line 15 in both versions
  - Old version had 10 lines in this section
  - New version has 12 lines (2 lines added)
  - Net change: +2 lines (12 - 10 = 2)

OTHER EXAMPLES:
  @@ -1,5 +1,3 @@      Removed 2 lines (5-3=2)
  @@ -20,7 +20,7 @@    Same number of lines (modification only)
  @@ -100,0 +102,3 @@  Added 3 new lines at line 102

--- a/api_client.py
+++ b/api_client.py
@@ -8,7 +8,8 @@ import requests
 
 class APIClient:
     def __init__(self, base_url, api_key):
-        self.base_url = base_url
+        self.base_url = base_url.rstrip('/')
+        self.session = requests.Session()
         self.api_key = api_key
     
     def get_devices(self):
@@ -22,12 +23,18 @@ class APIClient:
             'X-API-Key': self.api_key
         }
         
-        response = requests.get(url, headers=headers)
-        return response.json()
+        response = self.session.get(url, headers=headers, timeout=30)
+        
+        if response.status_code != 200:
+            raise Exception(f"API Error: {response.status_code}")
+        
+        return response.json()
     
     def update_device(self, device_id, config):
-        url = f"{self.base_url}/devices/{device_id}"
-        response = requests.patch(url, json=config)
+        url = f"{self.base_url}/api/devices/{device_id}"
+        headers = {'X-API-Key': self.api_key}
+        
+        response = self.session.patch(url, json=config, headers=headers, timeout=30)
         return response.status_code == 200

# INTERPRETATION:
# Changes in __init__ method:
#   + Added .rstrip('/') to normalize base_url
#   + Added session object for connection reuse
#
# Changes in get_devices():
#   - Removed direct requests.get(), using self.session
#   + Added timeout parameter (30 seconds)
#   + Added error handling for non-200 status codes
#   + Raises exception with descriptive error message
#
# Changes in update_device():
#   - Old URL: /devices/{id}
#   + New URL: /api/devices/{id} (more specific)
#   + Added headers with API key (was missing!)
#   + Using session instead of direct requests
#   + Added timeout
#
# Summary: Fixed 3 security issues
#   1. URL normalization
#   2. Missing authentication headers
#   3. Added error handling and timeouts

diff --git a/utils.py b/utils.py
index 1a2b3c4..5d6e7f8 100644
--- a/utils.py
+++ b/utils.py
@@ -45,7 +45,7 @@ def calculate_total(items):
     total = 0
     for item in items:
-        total += item.price * item.quantity
+        total += item.price * item.quantity * (1 - item.discount)
     return total

# INTERPRETATION:
# - File: utils.py
# - Function: calculate_total()
# - Change: Added discount calculation
# - Old behavior: Ignored discounts
# - New behavior: Applies discounts to pricing
# - Impact: Bug fix for pricing calculation

diff --git a/config.yaml b/config.yaml
index abc123..def456 100644
--- a/config.yaml
+++ b/config.yaml
@@ -10,6 +10,12 @@ database:
   password: ${DB_PASSWORD}
   port: 5432
 
+cache:
+  enabled: true
+  type: redis
+  host: localhost
+  port: 6379
+  ttl: 3600
+
 logging:
   level: INFO

# INTERPRETATION:
# - File: config.yaml (configuration file)
# - Addition: New "cache" section
# - Features added:
#   * Redis caching enabled
#   * Cache configuration (host, port, TTL)
# - No lines removed (pure addition)
# - Impact: Adding caching layer to application

diff --git a/auth.py b/auth.py
index 111222..333444 100644
--- a/auth.py
+++ b/auth.py
@@ -5,15 +5,20 @@ import hashlib
 
 def authenticate_user(username, password):
-    user = database.query("SELECT * FROM users WHERE username = '" + username + "'")
-    if user:
-        hashed = hashlib.md5(password.encode()).hexdigest()
-        if user.password == hashed:
-            return True
-    return False
+    # Use parameterized query to prevent SQL injection
+    user = database.query(
+        "SELECT * FROM users WHERE username = ?",
+        (username,)
+    )
+    
+    if not user:
+        return False
+    
+    # Use bcrypt instead of MD5 for password hashing
+    return bcrypt.checkpw(password.encode(), user.password)

# INTERPRETATION:
# - File: auth.py (authentication module)
# - Security fixes applied:
#   1. SQL Injection: Changed from string concatenation to parameterized query
#   2. Weak Hashing: Changed from MD5 to bcrypt
#   3. Code structure: Simplified logic flow
# - Lines removed: 6 lines of insecure code
# - Lines added: 9 lines of secure code
# - Net change: +3 lines
# - Impact: Critical security vulnerability fixed