//go:build linux

// tera-recovery-updater is the static PID 1 for authenticated offline updates.
package main

import (
	"bufio"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
	"time"

	"golang.org/x/sys/unix"

	"tera-clone/services/tera-api/internal/update"
	"tera-clone/services/tera-api/internal/update/recoveryapply"
	"tera-clone/services/tera-api/internal/update/recoveryrequest"
)

const (
	updateRoot      = "/userdata/update"
	trustDirectory  = "/etc/tera/update-trust"
	product         = "tera-core-x48-pro"
	hardwareProfile = "fet3568j-c"
	sectorBytes     = 512
)

func main() {
	mustMount("devtmpfs", "/dev", "devtmpfs", unix.MS_NOSUID, "mode=0755")
	mustMount("proc", "/proc", "proc", unix.MS_NOSUID|unix.MS_NOEXEC|unix.MS_NODEV, "")
	mustMount("sysfs", "/sys", "sysfs", unix.MS_NOSUID|unix.MS_NOEXEC|unix.MS_NODEV, "")
	// ttyS2 is a best-effort development trace only. The final product does not
	// expose COM5; durable status and journal files in userdata are authoritative.
	console, err := os.OpenFile("/dev/ttyS2", os.O_WRONLY, 0)
	if err != nil {
		console = os.Stdout
	}
	log := func(format string, values ...any) {
		fmt.Fprintf(console, "[tera-recovery-updater] "+format+"\r\n", values...)
	}
	log("START authenticated offline recovery updater")

	cmdline, err := os.ReadFile("/proc/cmdline")
	if err != nil || !containsWord(string(cmdline), "tera.recovery=update") || !containsWord(string(cmdline), "rdinit=/init") {
		hold(log, "FAIL unexpected recovery kernel command line: %q (%v)", strings.TrimSpace(string(cmdline)), err)
	}
	for _, partition := range recoveryPartitionContract {
		if err := requirePartName(partition.UEventPath, partition.Name); err != nil {
			hold(log, "FAIL partition identity %s: %v", partition.Name, err)
		}
	}
	misc, err := os.OpenFile(miscDevice, os.O_RDWR, 0)
	if err != nil {
		hold(log, "FAIL open misc: %v", err)
	}
	message, err := recoveryrequest.ReadAt(misc)
	if err != nil {
		hold(log, "FAIL read authenticated recovery request: %v", err)
	}
	log("PASS recovery request operation=%s", message.OperationID)
	if err := unix.Mount(userdataDevice, "/userdata", "ext4", unix.MS_NODEV|unix.MS_NOSUID|unix.MS_NOEXEC|unix.MS_NOATIME, userdataMountData); err != nil {
		hold(log, "FAIL mount userdata: %v", err)
	}
	bootBytes, err := blockBytes(bootSizePath)
	if err != nil {
		hold(log, "FAIL boot partition size: %v", err)
	}
	rootfsBytes, err := blockBytes(rootfsSizePath)
	if err != nil {
		hold(log, "FAIL rootfs partition size: %v", err)
	}
	packagePath := updateRoot + "/validated/" + message.OperationID + ".pkg"
	statusPath := updateRoot + "/journal/status.json"
	deviceVersion, err := readDeviceVersion(statusPath, message.OperationID)
	if err != nil {
		hold(log, "FAIL durable device-version binding: %v", err)
	}
	engine, err := recoveryapply.New(recoveryapply.Options{
		OperationID:    message.OperationID,
		PackagePath:    packagePath,
		JournalPath:    recoveryapply.JournalPath(updateRoot, message.OperationID),
		StatusPath:     statusPath,
		TrustDirectory: trustDirectory,
		Product:        product,
		Profile:        hardwareProfile,
		CurrentVersion: deviceVersion,
		Targets: map[string]recoveryapply.Target{
			"rootfs": {Path: rootfsDevice, MaxBytes: rootfsBytes},
			"boot":   {Path: bootDevice, MaxBytes: bootBytes},
		},
		ClearRecovery: func() error { return recoveryrequest.WriteAt(misc, recoveryrequest.Clear()) },
	})
	if err != nil {
		hold(log, "FAIL recovery engine setup: %v", err)
	}
	if err := engine.Run(); err != nil {
		hold(log, "FAIL recovery apply: %v", err)
	}
	log("PASS all selected payloads and readbacks verified; recovery request cleared")
	_ = misc.Close()
	unix.Sync()
	log("REBOOT normal boot")
	if err := unix.Reboot(unix.LINUX_REBOOT_CMD_RESTART); err != nil {
		hold(log, "FAIL reboot normal system: %v", err)
	}
	for {
		time.Sleep(time.Hour)
	}
}

func mustMount(source, target, filesystem string, flags uintptr, data string) {
	if err := unix.Mount(source, target, filesystem, flags, data); err != nil {
		fmt.Fprintf(os.Stderr, "mount %s: %v\n", target, err)
		for {
			time.Sleep(time.Hour)
		}
	}
}

func containsWord(value, wanted string) bool {
	for _, word := range strings.Fields(value) {
		if word == wanted {
			return true
		}
	}
	return false
}

func requirePartName(path, wanted string) error {
	file, err := os.Open(path)
	if err != nil {
		return err
	}
	defer file.Close()
	scanner := bufio.NewScanner(io.LimitReader(file, 4096))
	for scanner.Scan() {
		if scanner.Text() == "PARTNAME="+wanted {
			return nil
		}
	}
	if err := scanner.Err(); err != nil {
		return err
	}
	return fmt.Errorf("expected PARTNAME=%s", wanted)
}

func blockBytes(path string) (int64, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return 0, err
	}
	sectors, err := strconv.ParseInt(strings.TrimSpace(string(data)), 10, 64)
	if err != nil || sectors <= 0 || sectors > (1<<62)/sectorBytes {
		return 0, errors.New("invalid block-sector count")
	}
	return sectors * sectorBytes, nil
}

func readDeviceVersion(path, operationID string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()
	var status update.Status
	decoder := json.NewDecoder(io.LimitReader(file, 1024*1024))
	if err := decoder.Decode(&status); err != nil {
		return "", err
	}
	var trailing any
	if err := decoder.Decode(&trailing); err != io.EOF {
		return "", errors.New("status journal must contain exactly one JSON value")
	}
	if status.OperationID != operationID || strings.TrimSpace(status.DeviceVersion) == "" {
		return "", errors.New("status journal operation or device version does not match recovery request")
	}
	return status.DeviceVersion, nil
}

func hold(log func(string, ...any), format string, values ...any) {
	log(format, values...)
	for {
		time.Sleep(time.Hour)
	}
}