//go:build unix

package stats

import (
	"fmt"
	"os"
	"syscall"
)

// DiskUsage returns the space on the file systems holding paths (label ->
// directory), one entry per file system with the labels of the paths on
// it, in the order of labels.
func DiskUsage(labels []string, paths map[string]string) []Disk {
	var out []Disk
	byDev := map[string]int{}
	for _, l := range labels {
		p := paths[l]
		fi, err := os.Stat(p)
		if err != nil {
			continue
		}
		dev := fmt.Sprint(p)
		if st, ok := fi.Sys().(*syscall.Stat_t); ok {
			dev = fmt.Sprint(st.Dev)
		}
		if i, ok := byDev[dev]; ok {
			out[i].Holds = append(out[i].Holds, l)
			continue
		}
		var fs syscall.Statfs_t
		if err := syscall.Statfs(p, &fs); err != nil {
			continue
		}
		byDev[dev] = len(out)
		out = append(out, Disk{Path: p, Holds: []string{l}, Total: int64(fs.Blocks) * int64(fs.Bsize), Free: int64(fs.Bavail) * int64(fs.Bsize)})
	}
	return out
}