package model

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"
)

const (
	DefaultBridgeName                = "br-fc"
	DefaultBridgeIP                  = "172.16.0.1"
	DefaultCIDR                      = "24"
	DefaultDNS                       = "1.1.1.1"
	DefaultSystemOverlaySize         = 8 * 1024 * 1024 * 1024
	DefaultWorkDiskSize              = 8 * 1024 * 1024 * 1024
	DefaultMemoryMiB                 = 1024
	DefaultVCPUCount                 = 2
	DefaultStatsPollInterval         = 10 * time.Second
	DefaultStaleSweepInterval        = 1 * time.Minute
	DefaultMetricsPollInterval       = 15 * time.Second
	MaxDiskBytes               int64 = 128 * 1024 * 1024 * 1024
)

type VMState string

const (
	VMStateCreated VMState = "created"
	VMStateRunning VMState = "running"
	VMStateStopped VMState = "stopped"
	VMStateError   VMState = "error"
)

type DaemonConfig struct {
	RuntimeDir          string
	LogLevel            string
	FirecrackerBin      string
	SSHKeyPath          string
	NamegenPath         string
	CustomizeScript     string
	AutoStopStaleAfter  time.Duration
	StatsPollInterval   time.Duration
	MetricsPollInterval time.Duration
	BridgeName          string
	BridgeIP            string
	CIDR                string
	DefaultDNS          string
	DefaultImageName    string
	DefaultRootfs       string
	DefaultBaseRootfs   string
	DefaultKernel       string
	DefaultInitrd       string
	DefaultModulesDir   string
	DefaultPackagesFile string
}

type Image struct {
	ID           string    `json:"id"`
	Name         string    `json:"name"`
	Managed      bool      `json:"managed"`
	ArtifactDir  string    `json:"artifact_dir,omitempty"`
	RootfsPath   string    `json:"rootfs_path"`
	KernelPath   string    `json:"kernel_path"`
	InitrdPath   string    `json:"initrd_path,omitempty"`
	ModulesDir   string    `json:"modules_dir,omitempty"`
	PackagesPath string    `json:"packages_path,omitempty"`
	BuildSize    string    `json:"build_size,omitempty"`
	Docker       bool      `json:"docker"`
	CreatedAt    time.Time `json:"created_at"`
	UpdatedAt    time.Time `json:"updated_at"`
}

type VMSpec struct {
	VCPUCount             int   `json:"vcpu_count"`
	MemoryMiB             int   `json:"memory_mib"`
	SystemOverlaySizeByte int64 `json:"system_overlay_size_bytes"`
	WorkDiskSizeBytes     int64 `json:"work_disk_size_bytes"`
	NATEnabled            bool  `json:"nat_enabled"`
}

type VMRuntime struct {
	State         VMState `json:"state"`
	PID           int     `json:"pid,omitempty"`
	GuestIP       string  `json:"guest_ip"`
	TapDevice     string  `json:"tap_device,omitempty"`
	APISockPath   string  `json:"api_sock_path,omitempty"`
	LogPath       string  `json:"log_path,omitempty"`
	MetricsPath   string  `json:"metrics_path,omitempty"`
	DNSName       string  `json:"dns_name,omitempty"`
	VMDir         string  `json:"vm_dir"`
	SystemOverlay string  `json:"system_overlay_path"`
	WorkDiskPath  string  `json:"work_disk_path"`
	BaseLoop      string  `json:"base_loop,omitempty"`
	COWLoop       string  `json:"cow_loop,omitempty"`
	DMName        string  `json:"dm_name,omitempty"`
	DMDev         string  `json:"dm_dev,omitempty"`
	LastError     string  `json:"last_error,omitempty"`
}

type VMStats struct {
	CollectedAt        time.Time      `json:"collected_at,omitempty"`
	CPUPercent         float64        `json:"cpu_percent,omitempty"`
	RSSBytes           int64          `json:"rss_bytes,omitempty"`
	VSZBytes           int64          `json:"vsz_bytes,omitempty"`
	SystemOverlayBytes int64          `json:"system_overlay_bytes,omitempty"`
	WorkDiskBytes      int64          `json:"work_disk_bytes,omitempty"`
	MetricsRaw         map[string]any `json:"metrics_raw,omitempty"`
}

type VMRecord struct {
	ID            string    `json:"id"`
	Name          string    `json:"name"`
	ImageID       string    `json:"image_id"`
	State         VMState   `json:"state"`
	CreatedAt     time.Time `json:"created_at"`
	UpdatedAt     time.Time `json:"updated_at"`
	LastTouchedAt time.Time `json:"last_touched_at"`
	Spec          VMSpec    `json:"spec"`
	Runtime       VMRuntime `json:"runtime"`
	Stats         VMStats   `json:"stats"`
}

type VMCreateRequest struct {
	Name                  string
	ImageName             string
	VCPUCount             int
	MemoryMiB             int
	SystemOverlaySizeByte int64
	WorkDiskSizeBytes     int64
	NATEnabled            bool
	NoStart               bool
}

type VMSetRequest struct {
	IDOrName          string
	VCPUCount         *int
	MemoryMiB         *int
	WorkDiskSizeBytes *int64
	NATEnabled        *bool
}

type ImageBuildRequest struct {
	Name       string
	BaseRootfs string
	Size       string
	KernelPath string
	InitrdPath string
	ModulesDir string
	Docker     bool
}

func Now() time.Time {
	return time.Now().UTC().Truncate(time.Second)
}

func NewID() (string, error) {
	buf := make([]byte, 32)
	if _, err := rand.Read(buf); err != nil {
		return "", err
	}
	return hex.EncodeToString(buf), nil
}

func ParseSize(raw string) (int64, error) {
	if raw == "" {
		return 0, errors.New("size is required")
	}
	raw = strings.TrimSpace(strings.ToUpper(raw))
	if raw == "" {
		return 0, errors.New("size is required")
	}
	unit := raw[len(raw)-1]
	multiplier := int64(1024 * 1024)
	number := raw
	switch unit {
	case 'K':
		multiplier = 1024
		number = raw[:len(raw)-1]
	case 'M':
		multiplier = 1024 * 1024
		number = raw[:len(raw)-1]
	case 'G':
		multiplier = 1024 * 1024 * 1024
		number = raw[:len(raw)-1]
	default:
		if unit < '0' || unit > '9' {
			return 0, fmt.Errorf("unsupported size suffix: %q", string(unit))
		}
	}
	value, err := strconv.ParseInt(number, 10, 64)
	if err != nil {
		return 0, fmt.Errorf("parse size %q: %w", raw, err)
	}
	result := value * multiplier
	if result <= 0 {
		return 0, fmt.Errorf("size must be positive: %q", raw)
	}
	if result > MaxDiskBytes {
		return 0, fmt.Errorf("size exceeds max of %d bytes", MaxDiskBytes)
	}
	return result, nil
}

func FormatSizeBytes(bytes int64) string {
	switch {
	case bytes%(1024*1024*1024) == 0:
		return fmt.Sprintf("%dG", bytes/(1024*1024*1024))
	case bytes%(1024*1024) == 0:
		return fmt.Sprintf("%dM", bytes/(1024*1024))
	case bytes%1024 == 0:
		return fmt.Sprintf("%dK", bytes/1024)
	default:
		return strconv.FormatInt(bytes, 10)
	}
}