Generating PR Age Charts

Build an interactive CLI tool that visualizes pull request age distribution for a GitHub repository using Copilot's built-in capabilities.

Runnable example: recipe/PRVisualization.java

jbang recipe/PRVisualization.java

Example scenario

You want to understand how long PRs have been open in a repository. This tool detects the current Git repo or accepts a repo as input, then lets Copilot fetch PR data via the GitHub MCP Server and generate a chart image.

Usage

# Auto-detect from current git repo
jbang recipe/PRVisualization.java

# Specify a repo explicitly
jbang recipe/PRVisualization.java github/copilot-sdk

Full example: PRVisualization.java

//DEPS com.github:copilot-sdk-java:0.2.1-java.1
import com.github.copilot.sdk.CopilotClient;
import com.github.copilot.sdk.events.AssistantMessageEvent;
import com.github.copilot.sdk.events.ToolExecutionStartEvent;
import com.github.copilot.sdk.json.MessageOptions;
import com.github.copilot.sdk.json.PermissionHandler;
import com.github.copilot.sdk.json.SessionConfig;
import com.github.copilot.sdk.json.SystemMessageConfig;
import java.io.BufferedReader;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.regex.Pattern;

public class PRVisualization {

    public static void main(String[] args) throws Exception {
        System.out.println("🔍 PR Age Chart Generator\n");

        // Determine the repository
        String repo;
        if (args.length > 0) {
            repo = args[0];
            System.out.println("📦 Using specified repo: " + repo);
        } else if (isGitRepo()) {
            String detected = getGitHubRemote();
            if (detected != null && !detected.isEmpty()) {
                repo = detected;
                System.out.println("📦 Detected GitHub repo: " + repo);
            } else {
                System.out.println("⚠️  Git repo found but no GitHub remote detected.");
                repo = promptForRepo();
            }
        } else {
            System.out.println("📁 Not in a git repository.");
            repo = promptForRepo();
        }

        if (repo == null || !repo.contains("/")) {
            System.err.println("❌ Invalid repo format. Expected: owner/repo");
            System.exit(1);
        }

        String[] parts = repo.split("/", 2);
        String owner = parts[0];
        String repoName = parts[1];

        // Create Copilot client
        try (var client = new CopilotClient()) {
            client.start().get();

            String cwd = System.getProperty("user.dir");
            var systemMessage = String.format("""
                <context>
                You are analyzing pull requests for the GitHub repository: %s/%s
                The current working directory is: %s
                </context>

                <instructions>
                - Use the GitHub MCP Server tools to fetch PR data
                - Use your file and code execution tools to generate charts
                - Save any generated images to the current working directory
                - Be concise in your responses
                </instructions>
                """, owner, repoName, cwd);

            var session = client.createSession(
                new SessionConfig().setOnPermissionRequest(PermissionHandler.APPROVE_ALL)
                    .setModel("gpt-5")
                    .setSystemMessage(new SystemMessageConfig().setContent(systemMessage))
            ).get();

            // Set up event handling
            session.on(AssistantMessageEvent.class, msg -> 
                System.out.println("\n🤖 " + msg.getData().content() + "\n")
            );

            session.on(ToolExecutionStartEvent.class, evt -> 
                System.out.println("  ⚙️  " + evt.getData().toolName())
            );

            // Initial prompt - let Copilot figure out the details
            System.out.println("\n📊 Starting analysis...\n");

            String prompt = String.format("""
                Fetch the open pull requests for %s/%s from the last week.
                Calculate the age of each PR in days.
                Then generate a bar chart image showing the distribution of PR ages
                (group them into sensible buckets like <1 day, 1-3 days, etc.).
                Save the chart as "pr-age-chart.png" in the current directory.
                Finally, summarize the PR health - average age, oldest PR, and how many might be considered stale.
                """, owner, repoName);

            session.sendAndWait(new MessageOptions().setPrompt(prompt)).get();

            // Interactive loop
            System.out.println("\n💡 Ask follow-up questions or type \"exit\" to quit.\n");
            System.out.println("Examples:");
            System.out.println("  - \"Expand to the last month\"");
            System.out.println("  - \"Show me the 5 oldest PRs\"");
            System.out.println("  - \"Generate a pie chart instead\"");
            System.out.println("  - \"Group by author instead of age\"");
            System.out.println();

            try (var reader = new BufferedReader(new InputStreamReader(System.in))) {
                while (true) {
                    System.out.print("You: ");
                    String input = reader.readLine();
                    if (input == null) break;
                    input = input.trim();

                    if (input.isEmpty()) continue;
                    if (input.equalsIgnoreCase("exit") || input.equalsIgnoreCase("quit")) {
                        System.out.println("👋 Goodbye!");
                        break;
                    }

                    session.sendAndWait(new MessageOptions().setPrompt(input)).get();
                }
            }

            session.close();
        }
    }

    // ============================================================================
    // Git & GitHub Detection
    // ============================================================================

    private static boolean isGitRepo() {
        try {
            Process proc = Runtime.getRuntime().exec(new String[]{"git", "rev-parse", "--git-dir"});
            return proc.waitFor() == 0;
        } catch (Exception e) {
            return false;
        }
    }

    private static String getGitHubRemote() {
        try {
            Process proc = Runtime.getRuntime().exec(new String[]{"git", "remote", "get-url", "origin"});
            try (BufferedReader reader = new BufferedReader(new InputStreamReader(proc.getInputStream()))) {
                String remoteURL = reader.readLine();
                if (remoteURL == null) return null;
                remoteURL = remoteURL.trim();

                // Handle SSH: git@github.com:owner/repo.git
                var sshPattern = Pattern.compile("git@github\\.com:(.+/.+?)(?:\\.git)?$");
                var sshMatcher = sshPattern.matcher(remoteURL);
                if (sshMatcher.find()) {
                    return sshMatcher.group(1);
                }

                // Handle HTTPS: https://github.com/owner/repo.git
                var httpsPattern = Pattern.compile("https://github\\.com/(.+/.+?)(?:\\.git)?$");
                var httpsMatcher = httpsPattern.matcher(remoteURL);
                if (httpsMatcher.find()) {
                    return httpsMatcher.group(1);
                }
            }
        } catch (Exception e) {
            // Ignore
        }
        return null;
    }

    private static String promptForRepo() throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Enter GitHub repo (owner/repo): ");
        String line = reader.readLine();
        if (line == null) {
            throw new EOFException("End of input while reading repository name");
        }
        return line.trim();
    }
}

How it works

1. Repository detection: Checks command-line argument → git remote → prompts user
2. No custom tools: Relies entirely on Copilot CLI's built-in capabilities:
   • GitHub MCP Server — Fetches PR data from GitHub
   • File tools — Saves generated chart images
   • Code execution — Generates charts using Python/matplotlib or other methods
3. Interactive session: After initial analysis, user can ask for adjustments

Why this approach?

Aspect	Custom Tools	Built-in Copilot
Code complexity	High	Minimal
Maintenance	You maintain	Copilot maintains
Flexibility	Fixed logic	AI decides best approach
Chart types	What you coded	Any type Copilot can generate
Data grouping	Hardcoded buckets	Intelligent grouping

Best practices

1. Start with auto-detection: Let the tool detect the repository from the git remote before prompting the user
2. Use system messages: Provide context about the repo and working directory so Copilot can act autonomously
3. Approve tool execution: Use PermissionHandler.APPROVE_ALL to allow Copilot to run tools like the GitHub MCP Server without manual approval
4. Interactive follow-ups: Let users refine the analysis conversationally instead of requiring restarts
5. Save artifacts locally: Direct Copilot to save generated charts to the current directory for easy access