//go:build linux

package main

import (
	"encoding/json"
	"fmt"
	"os"
	"os/exec"
	"strings"
)

// reinstallBootloader mounts the freshly cloned root (and ESP), bind-mounts
// the API filesystems, and runs grub-install + grub-mkconfig inside a chroot.
// It is best-effort: it returns a human summary and never a hard error, so a
// clone still completes even when boot repair cannot.
func reinstallBootloader(diskPath, optsJSON string) string {
	var o bootOpts
	if err := json.Unmarshal([]byte(optsJSON), &o); err != nil {
		return "skipped: bad boot opts: " + err.Error()
	}
	if o.RootPart == 0 {
		return "skipped: no root partition identified (pass --reinstall-bootloader only for a Linux system disk)"
	}
	att, err := attachDisk(diskPath, true)
	if err != nil {
		return "skipped: attach: " + err.Error()
	}
	defer att.cleanup()

	rootNode := partNode(att.blockPath, o.RootPart)
	root, umount, err := mountAt(rootNode, false)
	if err != nil {
		return "skipped: mount root: " + err.Error()
	}
	defer umount()

	if o.ESPPart != 0 {
		espNode := partNode(att.blockPath, o.ESPPart)
		espDir := root + "/boot/efi"
		_ = os.MkdirAll(espDir, 0755)
		if out, err := exec.Command("mount", espNode, espDir).CombinedOutput(); err != nil {
			return "skipped: mount ESP: " + strings.TrimSpace(string(out))
		}
		defer exec.Command("umount", espDir).Run()
	}

	var log strings.Builder
	for _, d := range []string{"dev", "proc", "sys", "run"} {
		_ = exec.Command("mount", "--bind", "/"+d, root+"/"+d).Run()
		defer exec.Command("umount", "-l", root+"/"+d).Run()
	}

	grubTarget := att.blockPath
	if isDevicePath(diskPath) || looksLikeBlockDevice(diskPath) {
		grubTarget = diskPath
	}
	giArgs := []string{root, "grub-install", "--recheck"}
	if o.UEFI {
		giArgs = append(giArgs, "--target=x86_64-efi", "--efi-directory=/boot/efi", "--removable")
	} else {
		giArgs = append(giArgs, grubTarget)
	}
	if out, err := exec.Command("chroot", giArgs...).CombinedOutput(); err != nil {
		fmt.Fprintf(&log, "grub-install failed: %s; ", strings.TrimSpace(string(out)))
	} else {
		log.WriteString("grub-install ok; ")
	}

	mkcfg := "grub-mkconfig"
	if _, err := exec.LookPath("update-grub"); err == nil {
		mkcfg = "update-grub"
	}
	args := []string{root, mkcfg}
	if mkcfg == "grub-mkconfig" {
		args = append(args, "-o", "/boot/grub/grub.cfg")
	}
	if out, err := exec.Command("chroot", args...).CombinedOutput(); err != nil {
		fmt.Fprintf(&log, "%s failed: %s", mkcfg, strings.TrimSpace(string(out)))
	} else {
		log.WriteString(mkcfg + " ok")
	}
	return log.String()
}