# 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/pr-visualization.go](recipe/pr-visualization.go)
>
> ```bash
> # Auto-detect from current git repo
> go run recipe/pr-visualization.go
>
> # Specify a repo explicitly
> go run recipe/pr-visualization.go -repo github/copilot-sdk
> ```

## 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.

## Prerequisites

```bash
go get github.com/github/copilot-sdk/go
```

## Usage

```bash
# Auto-detect from current git repo
go run pr-visualization.go

# Specify a repo explicitly
go run pr-visualization.go -repo github/copilot-sdk
```

## Full example: pr-visualization.go

```go
package main

import (
    "bufio"
    "context"
    "flag"
    "fmt"
    "log"
    "os"
    "os/exec"
    "regexp"
    "strings"
    copilot "github.com/github/copilot-sdk/go"
)

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

func isGitRepo() bool {
    cmd := exec.Command("git", "rev-parse", "--git-dir")
    return cmd.Run() == nil
}

func getGitHubRemote() string {
    cmd := exec.Command("git", "remote", "get-url", "origin")
    output, err := cmd.Output()
    if err != nil {
        return ""
    }

    remoteURL := strings.TrimSpace(string(output))

    // Handle SSH: git@github.com:owner/repo.git
    sshRe := regexp.MustCompile(`git@github\.com:(.+/.+?)(?:\.git)?$`)
    if matches := sshRe.FindStringSubmatch(remoteURL); matches != nil {
        return matches[1]
    }

    // Handle HTTPS: https://github.com/owner/repo.git
    httpsRe := regexp.MustCompile(`https://github\.com/(.+/.+?)(?:\.git)?$`)
    if matches := httpsRe.FindStringSubmatch(remoteURL); matches != nil {
        return matches[1]
    }

    return ""
}

func promptForRepo() string {
    reader := bufio.NewReader(os.Stdin)
    fmt.Print("Enter GitHub repo (owner/repo): ")
    repo, _ := reader.ReadString('\n')
    return strings.TrimSpace(repo)
}

// ============================================================================
// Main Application
// ============================================================================

func main() {
    ctx := context.Background()
    repoFlag := flag.String("repo", "", "GitHub repository (owner/repo)")
    flag.Parse()

    fmt.Println("🔍 PR Age Chart Generator\n")

    // Determine the repository
    var repo string

    if *repoFlag != "" {
        repo = *repoFlag
        fmt.Printf("📦 Using specified repo: %s\n", repo)
    } else if isGitRepo() {
        detected := getGitHubRemote()
        if detected != "" {
            repo = detected
            fmt.Printf("📦 Detected GitHub repo: %s\n", repo)
        } else {
            fmt.Println("⚠️  Git repo found but no GitHub remote detected.")
            repo = promptForRepo()
        }
    } else {
        fmt.Println("📁 Not in a git repository.")
        repo = promptForRepo()
    }

    if repo == "" || !strings.Contains(repo, "/") {
        log.Fatal("❌ Invalid repo format. Expected: owner/repo")
    }

    parts := strings.SplitN(repo, "/", 2)
    owner, repoName := parts[0], parts[1]

    // Create Copilot client
    client := copilot.NewClient(nil)

    if err := client.Start(ctx); err != nil {
        log.Fatal(err)
    }
    defer client.Stop()

    cwd, _ := os.Getwd()
    session, err := client.CreateSession(ctx, &copilot.SessionConfig{
        Model: "gpt-5",
        SystemMessage: &copilot.SystemMessageConfig{
            Content: fmt.Sprintf(`
<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),
        },
    })
    if err != nil {
        log.Fatal(err)
    }
    defer session.Destroy()

    // Set up event handling
    session.On(func(event copilot.SessionEvent) {
        switch event.Type {
        case "assistant.message":
            if event.Data.Content != nil {
                fmt.Printf("\n🤖 %s\n\n", *event.Data.Content)
            }
        case "tool.execution_start":
            if event.Data.ToolName != nil {
                fmt.Printf("  ⚙️  %s\n", *event.Data.ToolName)
            }
        }
    })

    // Initial prompt - let Copilot figure out the details
    fmt.Println("\n📊 Starting analysis...\n")

    prompt := fmt.Sprintf(`
      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)

    if _, err := session.SendAndWait(ctx, copilot.MessageOptions{Prompt: prompt}); err != nil {
        log.Fatal(err)
    }

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

    reader := bufio.NewReader(os.Stdin)
    for {
        fmt.Print("You: ")
        input, _ := reader.ReadString('\n')
        input = strings.TrimSpace(input)

        if input == "" {
            continue
        }
        if strings.ToLower(input) == "exit" || strings.ToLower(input) == "quit" {
            fmt.Println("👋 Goodbye!")
            break
        }

        if _, err := session.SendAndWait(ctx, copilot.MessageOptions{Prompt: input}); err != nil {
            log.Printf("Error: %v", err)
        }
    }
}
```

## How it works

1. **Repository detection**: Checks `--repo` flag → 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**          |
