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))
}