fix(agent): handle vnstat 1.x JSON format to prevent frontend crash

[s0up4200]

Summary

• Adds backend normalization of vnstat JSON v1 format (vnstat 1.18 and earlier) to v2 format in the agent's historical export handler
• Renames plural keys (hours/days/months) to singular (hour/day/month)
• Synthesizes missing time field for hour entries from the id field
• Adds defensive null checks in the frontend parseMonitorUsagePeriods to prevent crashes if any period data is missing
• Removes debug console.log statements from production code
• Uses existing MonitorPeriod type instead of inline type literals

Test plan

• Unit tests added for normalizeVnstatV1 covering: full normalization, missing day in date, no interfaces, empty traffic
• Existing formatBytesPerSecond test converted to subtests
• go test ./internal/agent/ passes
• pnpm tsc --noEmit passes
• Verify with an actual vnstat 1.18 agent that bandwidth data displays correctly

Fixes #163

Summary by CodeRabbit

• New Features

  • Improved parsing and time-handling for monitor usage periods, with graceful empty-period summaries and more accurate week/month calculations.
  • Added normalization to accept older network traffic data formats.

• Bug Fixes

  • Improved resilience when traffic data is missing or incomplete; avoids errors and preserves sensible summaries.

• Tests

  • Added comprehensive tests for data-format normalization, edge cases, and byte-rate formatting.

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📝 Walkthrough

Walkthrough

Adds server-side normalization that converts vnstat JSON v1 (plural keys, missing hour time) into v2-like structure before timezone enrichment and frontend parsing; includes tests and frontend parser adjustments to handle missing traffic periods.

Changes

Cohort / File(s)	Summary
Backend normalization internal/agent/bandwidth.go	Adds normalizeVnstatV1(data map[string]any) and invokes it when jsonversion == "1". Converts plural traffic keys (hours→hour, days→day, months→month), synthesizes time fields for hour entries (deriving hour/minute from id), ensures a date.day when missing, and sets jsonversion to "2" before further processing.
Backend tests internal/agent/bandwidth_test.go	New tests covering standard v1→v2 normalization, hour entries lacking day, no interfaces, empty traffic, and formatBytesPerSecond formatting across units.
Frontend parser web/src/utils/monitorDataParser.ts	Refactors parsing to tolerate missing traffic periods: introduces EMPTY_SUMMARY, MonitorPeriod usage, resolveAgentTime, guarded access returning empty summaries when hour/day/month arrays are absent, and helper date utilities for week/month calculations.

Sequence Diagram(s)

sequenceDiagram
  participant Agent as Agent (vnStat JSON)
  participant Backend as Backend normalize
  participant Backend2 as Backend enrich
  participant Frontend as Frontend parser

  Agent->>Backend: send vnstat JSON (jsonversion "1" or "2")
  Backend->>Backend: if jsonversion == "1" → normalizeVnstatV1 (rename keys, synthesize time, set "2")
  Backend->>Backend2: add server_time / timezone info
  Backend2->>Frontend: return normalized + enriched JSON
  Frontend->>Frontend: parseMonitorUsagePeriods (guard missing periods, compute summaries)

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 I hopped through keys both old and new,
Turned "hours" to "hour" and forged timestamps true.
Tests snugly tucked, the frontend won't sigh—
Old vnstat whispers now speak clear and spry.
Hooray for compatibility, one small hop high! 🥕

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 15.79% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and accurately summarizes the main change: handling vnstat 1.x JSON format to prevent frontend crashes, which is the core objective of the PR.
Linked Issues check	✅ Passed	The PR addresses all coding requirements from issue #163: normalizes vnstat v1 JSON to v2 format in backend [163], adds defensive null checks in frontend [163], and includes tests for normalization [163].
Out of Scope Changes check	✅ Passed	All changes are in scope: backend normalization and tests for vnstat v1-to-v2 conversion directly address #163, frontend null checks prevent crashes, and console.log removal is minor cleanup supporting the fix.

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✨ Finishing touches

• 📝 Generate docstrings

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Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@web/src/utils/monitorDataParser.ts`:
- Around line 21-45: The early-return in monitorDataParser (the branch that
currently returns getEmptyUsage() when !traffic.hour && !traffic.day &&
!traffic.month) discards traffic.total; change this so that when period data is
missing you still return an object that preserves the "All Time" total (use
traffic.total when present) while keeping other period entries as empty. Locate
the guard around traffic and modify it to build the final return shape (the
object with keys like "This Hour", "Last Hour", Today, "This week", "This
Month", and "All Time") so that "All Time" uses traffic.total (or converts it
into {download:0, upload:0, total: traffic.total} if needed) instead of dropping
it; keep calls to
getCurrentHour/getLastHour/getToday/getThisWeek/getCurrentMonth and
getEmptyUsage for missing periods and use
data.server_time/data.server_time_unix/ timezone logic unchanged.

🧹 Nitpick comments (1)

internal/agent/bandwidth.go (1)

170-227: Avoid time drift by reusing a single now.

time.Now() is called inside normalization and again for server_time. If this crosses midnight, hour entries may get a different day than server_time, which can skew frontend matching. Consider capturing now once and passing it into normalization for consistency and deterministic behavior.

♻️ Proposed refactor

-	// Normalize vnstat 1.x JSON format to 2.x format
-	// vnstat 1.x uses "hours"/"days"/"months" (plural) and lacks "time" fields
-	// vnstat 2.x uses "hour"/"day"/"month" (singular) with "time" fields
-	if jsonVer, ok := bandwidthData["jsonversion"].(string); ok && jsonVer == "1" {
-		normalizeVnstatV1(bandwidthData)
-	}
-
-	// Add server time information for timezone handling
-	now := time.Now()
+	// Capture time once for normalization + server_time
+	now := time.Now()
+
+	// Normalize vnstat 1.x JSON format to 2.x format
+	// vnstat 1.x uses "hours"/"days"/"months" (plural) and lacks "time" fields
+	// vnstat 2.x uses "hour"/"day"/"month" (singular) with "time" fields
+	if jsonVer, ok := bandwidthData["jsonversion"].(string); ok && jsonVer == "1" {
+		normalizeVnstatV1(bandwidthData, now)
+	}

-func normalizeVnstatV1(data map[string]any) {
+func normalizeVnstatV1(data map[string]any, now time.Time) {
 ...
-						dateMap["day"] = float64(time.Now().Day())
+						dateMap["day"] = float64(now.Day())