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                 = 2048
	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 GuestSessionStatus string

const (
	GuestSessionStatusStarting GuestSessionStatus = "starting"
	GuestSessionStatusRunning  GuestSessionStatus = "running"
	GuestSessionStatusExited   GuestSessionStatus = "exited"
	GuestSessionStatusFailed   GuestSessionStatus = "failed"
	GuestSessionStatusStopping GuestSessionStatus = "stopping"
)

type GuestSessionStdinMode string

const (
	GuestSessionStdinClosed GuestSessionStdinMode = "closed"
	GuestSessionStdinPipe   GuestSessionStdinMode = "pipe"
)

type DaemonConfig struct {
	LogLevel            string
	FirecrackerBin      string
	SSHKeyPath          string
	AutoStopStaleAfter  time.Duration
	StatsPollInterval   time.Duration
	MetricsPollInterval time.Duration
	BridgeName          string
	BridgeIP            string
	CIDR                string
	TapPoolSize         int
	DefaultDNS          string
	DefaultImageName    string
	FileSync            []FileSyncEntry
	VMDefaults          VMDefaultsOverride
}

// FileSyncEntry is a user-declared host→guest file or directory copy
// applied to each VM's work disk at vm create time. Host is expanded
// against the host user's $HOME for "~/..."; Guest is expanded
// against /root (banger VMs are single-user root). If the host path
// is a directory, it's copied recursively; if it's a file, it's
// copied as a file. Missing host paths are a soft skip (warned, not
// fatal). Mode defaults to 0600 for files and 0755 for directories.
type FileSyncEntry struct {
	Host  string
	Guest string
	Mode  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"`
	WorkSeedPath                  string    `json:"work_seed_path,omitempty"`
	KernelPath                    string    `json:"kernel_path"`
	InitrdPath                    string    `json:"initrd_path,omitempty"`
	ModulesDir                    string    `json:"modules_dir,omitempty"`
	BuildSize                     string    `json:"build_size,omitempty"`
	SeededSSHPublicKeyFingerprint string    `json:"seeded_ssh_public_key_fingerprint,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"`
}

// VMRuntime holds the durable runtime state that the daemon needs
// to reach a VM: identity, declared state, and deterministic derived
// paths. Transient kernel/process handles (PID, tap, loop devices,
// dm-snapshot names) live on VMHandles, NOT here — the daemon keeps
// them in an in-memory cache backed by a per-VM handles.json scratch
// file, so a daemon restart rebuilds them from OS state rather than
// trusting whatever was last written into a SQLite column.
//
// Everything in VMRuntime is safe to persist: the paths are
// deterministic from (VM ID, layout) and survive restart unchanged;
// GuestIP and DNSName are assigned at create time and never move;
// LastError carries the last failure message for debugging. State
// mirrors VMRecord.State.
type VMRuntime struct {
	State         VMState `json:"state"`
	GuestIP       string  `json:"guest_ip"`
	APISockPath   string  `json:"api_sock_path,omitempty"`
	VSockPath     string  `json:"vsock_path,omitempty"`
	VSockCID      uint32  `json:"vsock_cid,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"`
	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 GuestSession struct {
	ID            string                `json:"id"`
	VMID          string                `json:"vm_id"`
	Name          string                `json:"name"`
	Backend       string                `json:"backend"`
	AttachBackend string                `json:"attach_backend,omitempty"`
	AttachMode    string                `json:"attach_mode,omitempty"`
	Command       string                `json:"command"`
	Args          []string              `json:"args,omitempty"`
	CWD           string                `json:"cwd,omitempty"`
	Env           map[string]string     `json:"env,omitempty"`
	StdinMode     GuestSessionStdinMode `json:"stdin_mode,omitempty"`
	Status        GuestSessionStatus    `json:"status"`
	ExitCode      *int                  `json:"exit_code,omitempty"`
	GuestPID      int                   `json:"guest_pid,omitempty"`
	GuestStateDir string                `json:"guest_state_dir,omitempty"`
	StdoutLogPath string                `json:"stdout_log_path,omitempty"`
	StderrLogPath string                `json:"stderr_log_path,omitempty"`
	Tags          map[string]string     `json:"tags,omitempty"`
	LastError     string                `json:"last_error,omitempty"`
	Attachable    bool                  `json:"attachable"`
	Reattachable  bool                  `json:"reattachable"`
	LaunchStage   string                `json:"launch_stage,omitempty"`
	LaunchMessage string                `json:"launch_message,omitempty"`
	LaunchRawLog  string                `json:"launch_raw_log,omitempty"`
	CreatedAt     time.Time             `json:"created_at"`
	StartedAt     time.Time             `json:"started_at,omitempty"`
	UpdatedAt     time.Time             `json:"updated_at"`
	EndedAt       time.Time             `json:"ended_at,omitempty"`
}

type WorkspacePrepareMode string

const (
	WorkspacePrepareModeShallowOverlay WorkspacePrepareMode = "shallow_overlay"
	WorkspacePrepareModeFullCopy       WorkspacePrepareMode = "full_copy"
	WorkspacePrepareModeMetadataOnly   WorkspacePrepareMode = "metadata_only"
)

type WorkspacePrepareResult struct {
	VMID          string               `json:"vm_id"`
	SourcePath    string               `json:"source_path"`
	RepoRoot      string               `json:"repo_root"`
	RepoName      string               `json:"repo_name"`
	GuestPath     string               `json:"guest_path"`
	Mode          WorkspacePrepareMode `json:"mode"`
	ReadOnly      bool                 `json:"readonly"`
	HeadCommit    string               `json:"head_commit,omitempty"`
	CurrentBranch string               `json:"current_branch,omitempty"`
	BranchName    string               `json:"branch_name,omitempty"`
	BaseCommit    string               `json:"base_commit,omitempty"`
	PreparedAt    time.Time            `json:"prepared_at"`
}

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)
	}
}