feat(collectors) basic implementation of boring collectors; sender via http(s) to hard coded api route

internal/collectors/disk/disk.go

@@ -0,0 +1,58 @@
+package disk
+
+import (
+	"syscall"
+
+	"bugs.watch/agent/internal/aggregate"
+)
+
+type Stats struct {
+	TotalBytes uint64
+	UsedBytes  uint64
+}
+
+// Read returns disk usage statistics for the root filesystem.
+func Read() (Stats, error) {
+	var fs syscall.Statfs_t
+
+	if err := syscall.Statfs("/", &fs); err != nil {
+		return Stats{}, err
+	}
+
+	total := fs.Blocks * uint64(fs.Bsize)
+	free := fs.Bavail * uint64(fs.Bsize)
+	used := total - free
+
+	return Stats{
+		TotalBytes: total,
+		UsedBytes:  used,
+	}, nil
+}
+
+// UsedPercent returns disk usage as a percentage.
+func UsedPercent(stats Stats) float64 {
+	if stats.TotalBytes == 0 {
+		return 0
+	}
+	return (float64(stats.UsedBytes) / float64(stats.TotalBytes)) * 100.0
+}
+
+// Collector implements the collectors.Collector interface for disk usage.
+type Collector struct{}
+
+func New() *Collector {
+	return &Collector{}
+}
+
+func (c *Collector) Name() string {
+	return "disk"
+}
+
+func (c *Collector) Collect(window *aggregate.Window) {
+	stats, err := Read()
+	if err != nil {
+		return
+	}
+
+	window.AddDisk(UsedPercent(stats))
+}