package daemon

import (
	"context"
	"strings"

	"banger/internal/model"
	"banger/internal/paths"
	"banger/internal/system"
)

var vsockHostDevicePath = "/dev/vhost-vsock"

func (d *Daemon) validateStartPrereqs(ctx context.Context, vm model.VMRecord, image model.Image) error {
	checks := system.NewPreflight()
	d.addBaseStartPrereqs(checks, image)
	d.addCapabilityStartPrereqs(ctx, checks, vm, image)
	return checks.Err("vm start preflight failed")
}

func (d *Daemon) validateImageBuildPrereqs(ctx context.Context, baseRootfs, kernelPath, initrdPath, modulesDir, sizeSpec string) error {
	checks := system.NewPreflight()
	d.addImageBuildPrereqs(ctx, checks, baseRootfs, kernelPath, initrdPath, modulesDir, sizeSpec)
	return checks.Err("image build preflight failed")
}

func (d *Daemon) validateWorkDiskResizePrereqs() error {
	checks := system.NewPreflight()
	checks.RequireCommand("truncate", toolHint("truncate"))
	checks.RequireCommand("e2fsck", `install e2fsprogs`)
	checks.RequireCommand("resize2fs", `install e2fsprogs`)
	return checks.Err("work disk resize preflight failed")
}

func (d *Daemon) addNATPrereqs(ctx context.Context, checks *system.Preflight) {
	checks.RequireCommand("iptables", toolHint("iptables"))
	checks.RequireCommand("sysctl", toolHint("sysctl"))
	runner := d.runner
	if runner == nil {
		runner = system.NewRunner()
	}
	out, err := runner.Run(ctx, "ip", "route", "show", "default")
	if err != nil {
		checks.Addf("failed to inspect the default route for NAT: %v", err)
		return
	}
	if _, err := parseDefaultUplink(string(out)); err != nil {
		checks.Addf("failed to detect the uplink interface for NAT: %v", err)
	}
}

func (d *Daemon) addBaseStartPrereqs(checks *system.Preflight, image model.Image) {
	hint := paths.RuntimeBundleHint()

	d.addBaseStartCommandPrereqs(checks)
	checks.RequireExecutable(d.config.FirecrackerBin, "firecracker binary", hint)
	checks.RequireExecutable(d.config.VSockAgentPath, "vsock agent", `run 'make build' or refresh the runtime bundle`)
	checks.RequireFile(vsockHostDevicePath, "vsock host device", "load the vhost_vsock kernel module on the host")
	checks.RequireFile(image.RootfsPath, "rootfs image", "select a valid image or rebuild the runtime bundle")
	checks.RequireFile(image.KernelPath, "kernel image", `set "default_kernel" or refresh the runtime bundle`)
	if strings.TrimSpace(image.InitrdPath) != "" {
		checks.RequireFile(image.InitrdPath, "initrd image", `set "default_initrd" or refresh the runtime bundle`)
	}
}

func (d *Daemon) addBaseStartCommandPrereqs(checks *system.Preflight) {
	for _, command := range []string{"sudo", "ip", "dmsetup", "losetup", "blockdev", "truncate", "pgrep", "chown", "chmod", "kill", "e2cp", "e2rm", "debugfs"} {
		checks.RequireCommand(command, toolHint(command))
	}
}

func (d *Daemon) addImageBuildPrereqs(ctx context.Context, checks *system.Preflight, baseRootfs, kernelPath, initrdPath, modulesDir, sizeSpec string) {
	hint := paths.RuntimeBundleHint()

	for _, command := range []string{"sudo", "ip", "pgrep", "chown", "chmod", "kill"} {
		checks.RequireCommand(command, toolHint(command))
	}
	for _, command := range []string{"mkfs.ext4", "mount", "umount", "cp"} {
		checks.RequireCommand(command, toolHint(command))
	}
	checks.RequireExecutable(d.config.FirecrackerBin, "firecracker binary", hint)
	checks.RequireFile(d.config.SSHKeyPath, "runtime ssh private key", `refresh the runtime bundle`)
	checks.RequireExecutable(d.config.VSockAgentPath, "vsock agent", `run 'make build' or refresh the runtime bundle`)
	checks.RequireFile(baseRootfs, "base rootfs image", `pass --base-rootfs or set "default_base_rootfs"`)
	checks.RequireFile(kernelPath, "kernel image", `pass --kernel or set "default_kernel"`)
	checks.RequireFile(d.config.DefaultPackagesFile, "package manifest", `set "default_packages_file" or refresh the runtime bundle`)
	if strings.TrimSpace(initrdPath) != "" {
		checks.RequireFile(initrdPath, "initrd image", `pass --initrd or set "default_initrd"`)
	}
	if strings.TrimSpace(modulesDir) != "" {
		checks.RequireDir(modulesDir, "modules directory", `pass --modules or set "default_modules_dir"`)
	}
	if strings.TrimSpace(d.config.DefaultPackagesFile) != "" {
		if _, err := system.ReadNormalizedLines(d.config.DefaultPackagesFile); err != nil {
			checks.Addf("package manifest at %s is invalid: %v", d.config.DefaultPackagesFile, err)
		}
	}
	if strings.TrimSpace(sizeSpec) != "" {
		checks.RequireCommand("e2fsck", toolHint("e2fsck"))
		checks.RequireCommand("resize2fs", toolHint("resize2fs"))
	}
	d.addNATPrereqs(ctx, checks)
}

func toolHint(command string) string {
	switch command {
	case "ip":
		return "install iproute2"
	case "iptables":
		return "install iptables"
	case "sysctl", "losetup", "blockdev", "mount", "umount":
		return "install util-linux"
	case "dmsetup":
		return "install device-mapper"
	case "pgrep", "kill":
		return "install procps"
	case "chown", "chmod", "cp", "truncate":
		return "install coreutils"
	case "e2fsck", "resize2fs", "debugfs", "mkfs.ext4":
		return "install e2fsprogs"
	case "e2cp", "e2rm":
		return "install e2tools"
	case "sudo":
		return "install sudo"
	default:
		return ""
	}
}