feat: Control Windows services and read their event log as workloads

internal/workloads/control_windows.go

@@ -0,0 +1,74 @@
+package workloads
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"gitea.hostxtra.co.uk/mrhid6/vantage/agent/internal/winexec"
+)
+
+// AgentUnit is the service this agent runs as — the NSSM service name written
+// by installer/setup.ps1. Change one, change the other.
+const AgentUnit = "VantageAgent"
+
+// A Windows agent is never itself in a container; the Linux build reads
+// /proc/self/cgroup, and there is no equivalent question to ask here.
+var ownContainerID = ""
+
+// Windows service names are case-insensitive, so the comparison must be too.
+func isProtectedUnit(id, name string) bool {
+	return strings.EqualFold(id, AgentUnit) || strings.EqualFold(name, AgentUnit)
+}
+
+func controlPlatform(ctx context.Context, kind, id, action string) error {
+	switch kind {
+	case "container":
+		// Docker behaves identically on Windows, so this path is shared in
+		// spirit with the Linux one rather than routed through PowerShell.
+		cmd := exec.CommandContext(ctx, "docker", action, id)
+		if out, err := cmd.CombinedOutput(); err != nil {
+			if ctx.Err() == context.DeadlineExceeded {
+				return fmt.Errorf("%s %s timed out after %s", action, id, controlTimeout)
+			}
+			return fmt.Errorf("%s %s: %s", action, id, strings.TrimSpace(string(out)))
+		}
+		return nil
+
+	case "unit":
+		// -Force is required: Stop-Service without it refuses outright when
+		// another service depends on the target, and that refusal reads to an
+		// operator as a silent no-op.
+		//
+		// sc.exe is avoided because it returns before the operation completes,
+		// which turns a timeout into a false success.
+		var verb string
+		switch action {
+		case "start":
+			verb = "Start-Service"
+		case "stop":
+			verb = "Stop-Service"
+		case "restart":
+			verb = "Restart-Service"
+		default:
+			return fmt.Errorf("unknown action %q", action)
+		}
+
+		script := "$ErrorActionPreference='Stop'\n" + verb + " -Name " + psQuote(id)
+		if action != "start" {
+			script += " -Force"
+		}
+
+		if _, err := winexec.Run(ctx, script); err != nil {
+			if ctx.Err() == context.DeadlineExceeded {
+				return fmt.Errorf("%s %s timed out after %s", action, id, controlTimeout)
+			}
+			return fmt.Errorf("%s %s: %w", action, id, err)
+		}
+		return nil
+
+	default:
+		return fmt.Errorf("unknown workload kind %q", kind)
+	}
+}

internal/workloads/logs_windows.go

@@ -0,0 +1,75 @@
+package workloads
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strconv"
+
+	"gitea.hostxtra.co.uk/mrhid6/vantage/agent/internal/winexec"
+)
+
+func logsPlatform(ctx context.Context, kind, id string, tail int) (string, error) {
+	switch kind {
+	case "container":
+		cmd := exec.CommandContext(ctx, "docker", "logs",
+			"--tail", strconv.Itoa(tail), "--timestamps", id)
+		out, err := cmd.CombinedOutput()
+		if err != nil && len(out) == 0 {
+			return "", fmt.Errorf("read logs for %s: %s", id, errText(err))
+		}
+		return string(out), nil
+
+	case "unit":
+		display := serviceDisplayName(ctx, id)
+
+		// Timestamps are formatted PowerShell-side rather than left to
+		// ConvertTo-Json, whose DateTime rendering differs between PowerShell
+		// versions — one of them emits /Date(1699...)/.
+		//
+		// -ErrorAction SilentlyContinue because Get-WinEvent treats "no events
+		// matched" as a terminating error, and a quiet service is normal.
+		names := psQuote(id)
+		if display != "" && display != id {
+			names += "," + psQuote(display)
+		}
+		names += "," + psQuote(scmProvider)
+
+		script := `
+$ErrorActionPreference = 'SilentlyContinue'
+$rows = Get-WinEvent -FilterHashtable @{LogName='System','Application'; ProviderName=@(` + names + `)} ` +
+			`-MaxEvents ` + strconv.Itoa(tail) + ` |
+  ForEach-Object {
+    [pscustomobject]@{
+      t = $_.TimeCreated.ToUniversalTime().ToString('o')
+      l = [string]$_.LevelDisplayName
+      p = [string]$_.ProviderName
+      m = [string]$_.Message
+    }
+  }
+ConvertTo-Json -InputObject @($rows) -Depth 3 -Compress
+`
+
+		out, err := winexec.Run(ctx, script)
+		if err != nil {
+			return "", fmt.Errorf("read events for %s: %w", id, err)
+		}
+		return parseEvents(out, id, display)
+
+	default:
+		return "", fmt.Errorf("unknown workload kind %q", kind)
+	}
+}
+
+// serviceDisplayName resolves a service's display name, which is what Service
+// Control Manager events name it by. An empty answer is fine — the filter then
+// matches on the service name alone.
+func serviceDisplayName(ctx context.Context, id string) string {
+	out, err := winexec.Run(ctx,
+		"$ErrorActionPreference='SilentlyContinue'\n"+
+			"(Get-Service -Name "+psQuote(id)+").DisplayName")
+	if err != nil {
+		return ""
+	}
+	return trimLine(out)
+}

internal/workloads/winparse.go

@@ -142,3 +142,61 @@ func parseServices(jsonText, systemRoot string) ([]Workload, error) {
 func psQuote(s string) string {
 	return "'" + strings.ReplaceAll(s, "'", "''") + "'"
 }
+
+// scmProvider is the provider every service's start and stop is logged under,
+// host-wide.
+const scmProvider = "Service Control Manager"
+
+type winEvent struct {
+	T string `json:"t"`
+	L string `json:"l"`
+	P string `json:"p"`
+	M string `json:"m"`
+}
+
+// parseEvents renders Get-WinEvent output as text in the shape journalctl
+// --output=short-iso produces, so the log dialog needs no per-platform
+// rendering: "<timestamp>  <level>  <message>", oldest first.
+func parseEvents(jsonText, serviceName, displayName string) (string, error) {
+	s := strings.TrimSpace(jsonText)
+	if s == "" || s == "null" {
+		return "", nil
+	}
+
+	var rows []winEvent
+	if err := json.Unmarshal([]byte(s), &rows); err != nil {
+		var one winEvent
+		if err2 := json.Unmarshal([]byte(s), &one); err2 != nil {
+			return "", err
+		}
+		rows = []winEvent{one}
+	}
+
+	var lines []string
+	for _, e := range rows {
+		if strings.EqualFold(e.P, scmProvider) {
+			if !strings.Contains(e.M, serviceName) &&
+				(displayName == "" || !strings.Contains(e.M, displayName)) {
+				continue
+			}
+		}
+		msg := strings.TrimSpace(strings.ReplaceAll(e.M, "\r\n", " "))
+		lines = append(lines, e.T+"  "+e.L+"  "+msg)
+	}
+
+	// Get-WinEvent is newest-first. Reverse it.
+	for i, j := 0, len(lines)-1; i < j; i, j = i+1, j-1 {
+		lines[i], lines[j] = lines[j], lines[i]
+	}
+	return strings.Join(lines, "\n"), nil
+}
+
+// trimLine reduces single-value PowerShell output to its first non-empty line.
+func trimLine(s string) string {
+	for _, l := range strings.Split(s, "\n") {
+		if t := strings.TrimSpace(l); t != "" {
+			return t
+		}
+	}
+	return ""
+}

internal/workloads/winparse_test.go

@@ -1,6 +1,9 @@
 package workloads
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 func TestServicePath(t *testing.T) {
 	cases := []struct{ in, want string }{
@@ -105,3 +108,55 @@ func TestPSQuote(t *testing.T) {
 		t.Fatalf("psQuote = %s", got)
 	}
 }
+
+func TestParseEventsFormatsAndOrders(t *testing.T) {
+	// Get-WinEvent returns newest first; journalctl --output=short-iso returns
+	// oldest first, and the log dialog and capLog's front-trim both assume the
+	// most recent line is at the bottom.
+	in := `[
+	  {"t":"2026-08-13T10:22:31.0000000Z","l":"Error","p":"Contoso","m":"broker died"},
+	  {"t":"2026-08-13T10:22:03.0000000Z","l":"Information","p":"Contoso","m":"broker starting"}
+	]`
+
+	got, err := parseEvents(in, "Contoso", "Contoso Broker")
+	if err != nil {
+		t.Fatalf("parseEvents: %v", err)
+	}
+
+	want := "2026-08-13T10:22:03.0000000Z  Information  broker starting\n" +
+		"2026-08-13T10:22:31.0000000Z  Error  broker died"
+	if got != want {
+		t.Fatalf("parseEvents =\n%q\nwant\n%q", got, want)
+	}
+}
+
+// Service Control Manager logs every service on the host under one provider, so
+// its rows must be filtered down to the target or the log is somebody else's.
+func TestParseEventsFiltersOtherServicesSCM(t *testing.T) {
+	in := `[
+	  {"t":"2026-08-13T10:00:00Z","l":"Information","p":"Service Control Manager","m":"The Print Spooler service entered the running state."},
+	  {"t":"2026-08-13T10:00:01Z","l":"Information","p":"Service Control Manager","m":"The Contoso Broker service entered the running state."}
+	]`
+
+	got, err := parseEvents(in, "Contoso", "Contoso Broker")
+	if err != nil {
+		t.Fatalf("parseEvents: %v", err)
+	}
+	if strings.Contains(got, "Print Spooler") {
+		t.Errorf("another service's SCM event leaked in:\n%s", got)
+	}
+	if !strings.Contains(got, "Contoso Broker") {
+		t.Errorf("the target's SCM event was dropped:\n%s", got)
+	}
+}
+
+// A service that has logged nothing is normal. An error there would read as a
+// broken feature.
+func TestParseEventsEmpty(t *testing.T) {
+	for _, in := range []string{"", "[]", "null"} {
+		got, err := parseEvents(in, "Contoso", "Contoso Broker")
+		if err != nil || got != "" {
+			t.Fatalf("parseEvents(%q) = %q, err %v", in, got, err)
+		}
+	}
+}