MOSS Controller

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Overview

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Constructor

public function __construct()

• auth - Requires user authentication

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Methods

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index()

public function index($assignment_id)

• Admin and head_instructor only
• Aborts with 403 for other roles

• All assignments list
• Current MOSS user ID from settings
• Selected assignment information
• Last MOSS update timestamp
• MOSS results for each problem:
  • Problem data
  • MOSS report URL (if available)
  • “submission submitted” message (if processing)
  • NULL (if not yet analyzed)

$assignment = Assignment::find($assignment_id);
if ($assignment == null)
    abort(404, 'Can not find this assignment!');

$moss_userid = Setting::get('moss_userid');
if ($moss_userid == null) 
    $moss_userid = -1;

$moss_problems = array();
foreach ($assignment->problems as $problem) {
    $moss_problems[$problem->id]['problem'] = $problem;
    $path = Submission::get_path('', $assignment_id, $problem->id) . '/';
    
    if (file_exists($path . "moss_link.txt") && file_get_contents($path . "moss_link.txt") != '') {
        $moss_problems[$problem->id]['moss'] = shell_exec("tail -n1 $path/moss_link.txt");
        shell_exec("rm $path/moss_running");
    } else if (file_exists($path . "moss_running")) {
        $moss_problems[$problem->id]['moss'] = "submission submitted to moss, awaiting response, please be patient";
    } else {
        $moss_problems[$problem->id]['moss'] = NULL;
    }
}

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update()

public function update(Request $request, $assignment_id = FALSE)

• Admin and head_instructor only (implied from route)

1. Saves MOSS user ID to settings
2. Reads original MOSS script template
3. Replaces placeholder with actual user ID
4. Writes configured script to tester path
5. Makes script executable

$userid = $request->moss_userid;
Setting::set('moss_userid', $userid);

$moss_original = trim(file_get_contents(
    rtrim(Setting::get('tester_path'), '/') . '/moss_original'
));
$moss_path = rtrim(Setting::get('tester_path'), '/') . '/moss';

file_put_contents(
    $moss_path, 
    str_replace('MOSS_USER_ID', $userid, $moss_original)
);

shell_exec("chmod +x {$moss_path}");

​

detect()

public function detect(Request $request, $assignment_id = FALSE)

• detect: required

• Admin and head_instructor only (implied from form submission)

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Private Methods

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_detect()

private function _detect($assignment_id = FALSE)

1. Get Final Submissions
   • Fetches all final submissions for the assignment
   • Groups submissions by problem ID
2. For Each Problem:
   • Builds list of submission file paths
   • Submits files to MOSS via command line
   • Redirects MOSS output to moss_link.txt
   • Creates moss_running flag file
3. Update Timestamp
   • Records MOSS update time in assignment record

assignments_root/assignment_{id}/problem_{id}/
├── {username1}/
│   └── {filename}.{ext}
├── {username2}/
│   └── {filename}.{ext}
├── moss_link.txt        # MOSS result URL
└── moss_running         # Flag indicating processing

$items = Submission::get_final_submissions($assignment_id);
$groups = array();

// Group by problem
foreach ($items as $item) {
    if (!isset($groups[$item->problem_id]))
        $groups[$item->problem_id] = array($item);
    else
        array_push($groups[$item->problem_id], $item);
}

// Process each problem
foreach ($groups as $problem_id => $group) {
    $list = '';
    $assignment_path = $assignments_path . "/assignment_{$assignment_id}";
    
    foreach ($group as $item) {
        $list .= "problem_{$problem_id}/{$item->username}/{$item->file_name}." .
                 (string)Language::find($item->language_id)->extension . " ";
    }
    
    shell_exec(
        "list='$list'; cd $assignment_path; $tester_path/moss \$list > problem_{$problem_id}/moss_link.txt 2>&1 &"
    );
    shell_exec("cd $assignment_path/problem_{$problem_id}; touch moss_running");
}

Assignment::where('id', $assignment_id)->update(['moss_update' => date('Y-m-d H:i:s')]);

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MOSS Integration Workflow

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1. Initial Setup

1. Obtain MOSS Account
   • Register at Stanford MOSS website
   • Receive MOSS user ID via email
2. Configure Wecode
   • Navigate to MOSS page for any assignment
   • Enter MOSS user ID in configuration form
   • Submit to save and configure MOSS script

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2. Running Detection

1. Select Assignment
   • Navigate to /moss/{assignment_id}
   • View current MOSS status for all problems
2. Trigger Detection
   • Click “Detect” button
   • System collects all final submissions
   • Submissions grouped by problem
   • Files submitted to MOSS in background
3. Processing States
   • Not Analyzed: No MOSS results yet (NULL)
   • Processing: “submission submitted to moss, awaiting response”
   • Complete: MOSS report URL displayed

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3. Viewing Results

1. Check Status
   • Refresh MOSS page to check for completion
   • Once complete, MOSS URL appears
2. Access Report
   • Click on MOSS URL
   • Opens Stanford MOSS report in new tab
   • Report shows similarity percentages and matches

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MOSS Script Configuration

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Template Structure

#!/usr/bin/perl
# MOSS configuration
$userid = MOSS_USER_ID;
# ... rest of MOSS script

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Configuration Process

1. Read moss_original template from tester path
2. Replace MOSS_USER_ID with actual user ID
3. Write to moss file in tester path
4. Make executable with chmod +x

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Paths

• Template: {tester_path}/moss_original
• Configured Script: {tester_path}/moss
• Results: {assignments_root}/assignment_{id}/problem_{id}/moss_link.txt

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MOSS Result Files

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moss_link.txt

... MOSS processing output ...
http://moss.stanford.edu/results/1234567890

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moss_running

• Created when MOSS detection starts
• Deleted when results are retrieved
• Presence indicates “awaiting response” state

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Settings

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moss_userid

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Notes

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Supported Languages

• C/C++ (.c, .cpp, .cc, .h)
• Java (.java)
• Python (.py, .py2, .py3)
• Pascal (.pas)
• And many more

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Background Processing

moss $list > moss_link.txt 2>&1 &

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Result Persistence

• Independent analysis per problem
• Easy re-analysis without data loss
• Direct file access for debugging

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Related Models

• Assignment: Assignment being analyzed
• Submission: Student submissions to compare
• Language: Programming language detection
• Setting: MOSS configuration storage