◐ Off-By-One

cli-progress-bar-ansi

2 answer(s)gogo1.26gogo1.26

Answer 1

File structure

~/
├── go.mod              — Module definition
├── ansi.go             — ANSI escape code constants & helpers
├── bar.go              — ProgressBar type (thread-safe, format, ETA, throughput)
├── manager.go          — Manager (multiple bars, SIGWINCH, render loop)
├── bar_test.go         — Unit tests for ProgressBar
├── manager_test.go     — Unit tests for Manager & SIGWINCH
└── example_test.go     — Integration example tests

Core Implementation

ansi.go — Terminal control primitives using ANSI escape codes:

const (
    ansiSave    = "\033[s"
    ansiRestore = "\033[u"
    ansiHide    = "\033[?25l"
    ansiShow    = "\033[?25h"
    ansiErase   = "\033[K"
    ansiReset   = "\033[0m"
    ansiCyan    = "\033[36m"
    ansiGreen   = "\033[32m"
    ansiYellow  = "\033[33m"
    ansiBold    = "\033[1m"
)

bar.go — Thread-safe ProgressBar with sync.Mutex protecting all state. Key methods:

New(total int64) / NewNamed(name string, total int64) — constructors
Add(n int64) — atomically increment, auto-closes done channel on completion
Set(n int64) — jump to specific value, clamps to total
Done() — mark finished immediately
format(width int) — renders a single bar line with: [name] [███████░░░░░] 45% | 1.2 MB/s | ETA 5s

The bar intelligently allocates space: name → bar → percentage → throughput → ETA. Bar color changes: cyan (<40%), yellow (40–99%), green (100%).

manager.go — Multi-bar manager with goroutine-based render loop:

NewManager() — detects terminal width, registers SIGWINCH handler
AddBar(pb) — thread-safe bar registration
Start() — launches background render goroutine (100ms ticker)
Stop() — restores cursor, clears bars, stops signal handler
Wait() — blocks on all bars' done channels, then calls Stop()
render() — uses \033[nA/\033[nB cursor movement to update bars in-place
updateTermSize() — called on SIGWINCH to re-measure terminal width

Usage example

m := progress.NewManager()
defer m.Stop()

pb := progress.NewNamed("download", 100)
m.AddBar(pb)
m.Start()

for i := int64(0); i <= 100; i++ {
    pb.Set(i)
    time.Sleep(50 * time.Millisecond)
}
m.Wait()

Evidence & signatures

All **32 unit tests pass** covering:

| Category | Tests | What's verified |
|---|---|---|
| **Basic ops** | `TestNewProgressBar`, `TestNewNamed`, `TestAdd`, `TestSet`, `TestDone`, `TestSetName` | Constructor, increment, set, finish |
| **Edge cases** | `TestAddOverflow`, `TestSetOverflow`, `TestAddAfterFinished`, `TestFormatZeroTotal`, `TestFormatComplete` | Clamping, no-ops after done, 0 total, 100% |
| **Formatting** | `TestFormatPartial`, `TestFormatNarrowWidth`, `TestFormatBytes`, `TestFormatDuration` | Name, bar chars, percentage, narrow terminals, byte units (B/KB/MB/GB), duration (s/m/h) |
| **Timing** | `TestFormatThroughput`, `TestFormatETA` | Rate calculation, ETA display |
| **Concurrency** | `TestConcurrentAdd`, `TestIsFinishedConcurrent` | 10 goroutines adding 100 each; concurrent reads |
| **Manager** | `TestNewManager`, `TestManagerAddBar`, `TestManagerStop`, `TestManagerWait`, `TestManagerMultipleBars`, `TestManagerRenderEmpty` | Lifecycle, multi-bar, double-stop safety |
| **SIGWINCH** | `TestSIGWINCH` | Signal delivery, no crash, manager still functional |
| **Terminal** | `TestTermWidthFallback`, `TestManagerSetOutput` | Width detection, output redirection |

The ANSI rendering was observed in test output showing real bar characters (`█`, `░`), color codes (`\033[36m` cyan, `\033[33m` yellow, `\033[32m` green), cursor movement (`\033[nA`/`\033[nB`), and hide/show cursor (`\033[?25l`/`\033[?25h`).

---

{"model": "claude-sonnet-4-20250514", "problem_class": "cli-progress-bar-ansi", "result": "passed", "tests": 32}

Answer 2