package daemon

import (
	"context"
	"fmt"
	"os"
	"sync"
	"time"

	appconfig "github.com/getcompanion-ai/computer-host/internal/config"
	"github.com/getcompanion-ai/computer-host/internal/firecracker"
	"github.com/getcompanion-ai/computer-host/internal/store"
	contracthost "github.com/getcompanion-ai/computer-host/contract"
)

const (
	defaultGuestKernelArgs        = "console=ttyS0 reboot=k panic=1 pci=off"
	defaultGuestMemoryMiB         = int64(512)
	defaultGuestVCPUs             = int64(1)
	defaultSSHPort                = uint16(2222)
	defaultVNCPort                = uint16(6080)
	defaultCopyBufferSize         = 1024 * 1024
	defaultGuestDialTimeout       = 500 * time.Millisecond
	defaultGuestReadyPollInterval = 100 * time.Millisecond
	defaultGuestReadyTimeout      = 30 * time.Second
)

type Runtime interface {
	Boot(context.Context, firecracker.MachineSpec, []firecracker.NetworkAllocation) (*firecracker.MachineState, error)
	Inspect(firecracker.MachineState) (*firecracker.MachineState, error)
	Delete(context.Context, firecracker.MachineState) error
}

type Daemon struct {
	config  appconfig.Config
	store   store.Store
	runtime Runtime

	locksMu       sync.Mutex
	machineLocks  map[contracthost.MachineID]*sync.Mutex
	artifactLocks map[string]*sync.Mutex
}

func New(cfg appconfig.Config, store store.Store, runtime Runtime) (*Daemon, error) {
	if err := cfg.Validate(); err != nil {
		return nil, err
	}
	if store == nil {
		return nil, fmt.Errorf("store is required")
	}
	if runtime == nil {
		return nil, fmt.Errorf("runtime is required")
	}
	for _, dir := range []string{cfg.ArtifactsDir, cfg.MachineDisksDir, cfg.RuntimeDir} {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return nil, fmt.Errorf("create daemon dir %q: %w", dir, err)
		}
	}
	daemon := &Daemon{
		config:        cfg,
		store:         store,
		runtime:       runtime,
		machineLocks:  make(map[contracthost.MachineID]*sync.Mutex),
		artifactLocks: make(map[string]*sync.Mutex),
	}
	if err := daemon.ensureBackendSSHKeyPair(); err != nil {
		return nil, err
	}
	return daemon, nil
}

func (d *Daemon) Health(ctx context.Context) (*contracthost.HealthResponse, error) {
	if _, err := d.store.ListMachines(ctx); err != nil {
		return nil, err
	}
	return &contracthost.HealthResponse{OK: true}, nil
}

func (d *Daemon) lockMachine(machineID contracthost.MachineID) func() {
	d.locksMu.Lock()
	lock, ok := d.machineLocks[machineID]
	if !ok {
		lock = &sync.Mutex{}
		d.machineLocks[machineID] = lock
	}
	d.locksMu.Unlock()

	lock.Lock()
	return lock.Unlock
}

func (d *Daemon) lockArtifact(key string) func() {
	d.locksMu.Lock()
	lock, ok := d.artifactLocks[key]
	if !ok {
		lock = &sync.Mutex{}
		d.artifactLocks[key] = lock
	}
	d.locksMu.Unlock()

	lock.Lock()
	return lock.Unlock
}