package platforms

import (
	"bufio"
	"os"
	"runtime"
	"strings"

	"github.com/containerd/containerd/errdefs"
	"github.com/containerd/containerd/log"
	"github.com/pkg/errors"
)

// Present the ARM instruction set architecture, eg: v7, v8
var cpuVariant string

func init() {
	if isArmArch(runtime.GOARCH) {
		cpuVariant = getCPUVariant()
	} else {
		cpuVariant = ""
	}
}

// For Linux, the kernel has already detected the ABI, ISA and Features.
// So we don't need to access the ARM registers to detect platform information
// by ourselves. We can just parse these information from /proc/cpuinfo
func getCPUInfo(pattern string) (info string, err error) {
	if !isLinuxOS(runtime.GOOS) {
		return "", errors.Wrapf(errdefs.ErrNotImplemented, "getCPUInfo for OS %s", runtime.GOOS)
	}

	cpuinfo, err := os.Open("/proc/cpuinfo")
	if err != nil {
		return "", err
	}
	defer cpuinfo.Close()

	// Start to Parse the Cpuinfo line by line. For SMP SoC, we parse
	// the first core is enough.
	scanner := bufio.NewScanner(cpuinfo)
	for scanner.Scan() {
		newline := scanner.Text()
		list := strings.Split(newline, ":")

		if len(list) > 1 && strings.EqualFold(strings.TrimSpace(list[0]), pattern) {
			return strings.TrimSpace(list[1]), nil
		}
	}

	// Check whether the scanner encountered errors
	err = scanner.Err()
	if err != nil {
		return "", err
	}

	return "", errors.Wrapf(errdefs.ErrNotFound, "getCPUInfo for pattern: %s", pattern)
}

func getCPUVariant() string {
	variant, err := getCPUInfo("Cpu architecture")
	if err != nil {
		log.L.WithError(err).Error("failure getting variant")
		return ""
	}

	switch variant {
	case "8":
		variant = "v8"
	case "7", "7M", "?(12)", "?(13)", "?(14)", "?(15)", "?(16)", "?(17)":
		variant = "v7"
	case "6", "6TEJ":
		variant = "v6"
	case "5", "5T", "5TE", "5TEJ":
		variant = "v5"
	case "4", "4T":
		variant = "v4"
	case "3":
		variant = "v3"
	default:
		variant = "unknown"
	}

	return variant
}