package system

import (
	"math"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"testing"
)

// R-889 — real numbers, measured 2026-10-06 07:55 on demo-hp guest 9201 (`df -P` + `stat -f`):
//
//	/mnt/sys_drive  df: 72064432 1K-blocks, used 15460836, avail 52917208, Use% 23
//	                stat -f: bsize=4096 blocks=18016108 free=14150899 avail=13229302
//
// The old formula ((blocks-free)/blocks) gave 21.5 % there; df gives 23 %. And the R-516 (11) shape: 61.8 of 68.7 GB
// with 5 % reserved read 90 % where df read 95 %.
func TestDFUsedPercent_MatchesDFOnRealNumbers(t *testing.T) {
	const bs = 4096.0
	blocks, free, avail := 18016108.0, 14150899.0, 13229302.0
	used := (blocks - free) * bs
	got := DFUsedPercent(used, avail*bs)
	if math.Ceil(got) != 23 {
		t.Fatalf("demo-hp /mnt/sys_drive: DFUsedPercent = %.2f, df prints 23%% (it rounds up)", got)
	}
	old := (blocks - free) / blocks * 100
	if math.Abs(got-old) < 1 {
		t.Fatalf("the df number (%.2f) must differ from the old used/total (%.2f) on a disk with reserved blocks", got, old)
	}
	// R-516 (11): a 68.7 GB filesystem with 5 % reserved, 61.8 GB used.
	total, usedGB := 68.7, 61.8
	availGB := total*0.95 - usedGB
	if p := DFUsedPercent(usedGB, availGB); math.Round(p) != 95 {
		t.Fatalf("the R-516 shape reads %.1f %%, df read 95 %%", p)
	}
	if DFUsedPercent(0, 0) != 0 || DFUsedPercent(10, 0) != 100 {
		t.Fatal("empty → 0, nothing available → 100")
	}
}

// Every disk percent in the controller is the df one: no production Go file divides a used/avail figure by the whole
// filesystem any more. Red-proof: put `float64(used) / float64(total) * 100` back in mounts_linux.go — this fails.
func TestR889_EveryDiskPercentIsTheDFOne(t *testing.T) {
	bad := regexp.MustCompile(`(?:/\s*float64\(total\)\s*\*\s*100|/\s*[A-Za-z_.]*TotalGB\s*\*\s*100)`)
	root := filepath.Join("..", "..")
	var hits []string
	for _, dir := range []string{"internal", "cmd"} {
		_ = filepath.Walk(filepath.Join(root, dir), func(p string, info os.FileInfo, err error) error {
			if err != nil || info.IsDir() || !strings.HasSuffix(p, ".go") || strings.HasSuffix(p, "_test.go") {
				return nil
			}
			b, rerr := os.ReadFile(p)
			if rerr != nil {
				return nil
			}
			for i, line := range strings.Split(string(b), "\n") {
				if bad.MatchString(line) && !strings.HasPrefix(strings.TrimSpace(line), "//") {
					hits = append(hits, p+":"+itoa(uint64(i+1))+": "+strings.TrimSpace(line))
				}
			}
			return nil
		})
	}
	if len(hits) > 0 {
		t.Fatalf("a disk percent divides by the whole filesystem (not df's used/(used+avail)) — use DFUsedPercent:\n%s", strings.Join(hits, "\n"))
	}
}