package orchestrator

import (
	"os"
	"path/filepath"
	"strconv"
)

// Config holds all tunables for the orchestrator.
type Config struct {
	FCBin      string // path to firecracker binary
	BaseDir    string // working directory for all state
	Kernel     string // path to vmlinux
	KernelURL  string // URL to download vmlinux if Kernel file is missing
	CustomRootfs string // Custom path to rootfs if FC_ROOTFS is set
	VCPUs      int64
	MemMiB     int64
	Bridge       string // host bridge name, or "none" to skip networking
	BridgeCIDR   string // e.g. "172.30.0.1/24"
	GuestPrefix  string // e.g. "172.30.0" — clones get .11, .12, ...
	GuestGW      string // default gateway for guest VMs
	AutoNetConfig bool   // inject guest IP/GW/DNS via MMDS on clone start
	BootArgs     string
}

func DefaultConfig() Config {
	c := Config{
		FCBin:       envOr("FC_BIN", "firecracker"),
		BaseDir:     envOr("FC_BASE_DIR", "/tmp/fc-orch"),
		VCPUs:       envOrInt("FC_VCPUS", 1),
		MemMiB:      envOrInt("FC_MEM_MIB", 128),
		Bridge:      envOr("FC_BRIDGE", "fcbr0"),
		BridgeCIDR:  envOr("FC_BRIDGE_CIDR", "172.30.0.1/24"),
		GuestPrefix:  envOr("FC_GUEST_PREFIX", "172.30.0"),
		GuestGW:      envOr("FC_GUEST_GW", "172.30.0.1"),
		AutoNetConfig: envOr("FC_AUTO_NET_CONFIG", "") == "1",
		BootArgs:     "console=ttyS0 reboot=k panic=1 pci=off i8042.noaux",
	}
	c.Kernel = envOr("FC_KERNEL", c.BaseDir+"/vmlinux")
	c.KernelURL = envOr("FC_KERNEL_URL",
		"https://s3.amazonaws.com/spec.ccfc.min/firecracker-ci/20260408-ce2a467895c1-0/x86_64/vmlinux-6.1.166")
	c.CustomRootfs = os.Getenv("FC_ROOTFS")
	return c
}

// RootfsPath returns the path to the root filesystem depending on the requested distribution.
func (c Config) RootfsPath(distro string) string {
	if c.CustomRootfs != "" {
		return c.CustomRootfs
	}
	return filepath.Join(c.BaseDir, "rootfs-"+distro+".ext4")
}

func envOr(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func envOrInt(key string, fallback int64) int64 {
	if v := os.Getenv(key); v != "" {
		if n, err := strconv.ParseInt(v, 10, 64); err == nil {
			return n
		}
	}
	return fallback
}