package miner

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

	"crypto-miner-agent/config"
)

const defaultMinerImage = "aetherforge/agent-worker:latest"

// containerExecCommand is exec.Command; tests override via SetContainerExecCommand.
var containerExecCommand = exec.Command

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

// ContainerLauncher supervises an OCI workload that runs CPU mining isolated from the host agent.
type ContainerLauncher struct {
	cfg      config.RuntimeConfig
	runtime  ContainerRuntimeInfo
	image    string
	name     string
	tarPath  string // non-empty → docker load from tar, never registry pull
	readOnly bool   // docker_load tier uses --read-only rootfs

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

// NewContainerLauncher builds a launcher when a container runtime is available.
func NewContainerLauncher(cfg config.RuntimeConfig, runtime ContainerRuntimeInfo) (*ContainerLauncher, error) {
	return newContainerLauncher(cfg, runtime, "", false)
}

// NewContainerLauncherFromTar builds a docker_load tier launcher (local tar, no registry pull).
func NewContainerLauncherFromTar(cfg config.RuntimeConfig, runtime ContainerRuntimeInfo, tarPath string) (*ContainerLauncher, error) {
	tarPath = strings.TrimSpace(tarPath)
	if tarPath == "" {
		return nil, ErrNoImageTar
	}
	return newContainerLauncher(cfg, runtime, tarPath, true)
}

func newContainerLauncher(cfg config.RuntimeConfig, runtime ContainerRuntimeInfo, tarPath string, readOnly bool) (*ContainerLauncher, error) {
	if !runtime.Available || runtime.CLI == "" {
		return nil, fmt.Errorf("no container runtime (docker/podman not in PATH)")
	}
	image := strings.TrimSpace(os.Getenv("AETHERFORGE_MINER_IMAGE"))
	if image == "" {
		image = defaultMinerImage
	}
	name := containerName(cfg)
	return &ContainerLauncher{
		cfg:      cfg,
		runtime:  runtime,
		image:    image,
		name:     name,
		tarPath:  tarPath,
		readOnly: readOnly,
	}, nil
}

func containerName(cfg config.RuntimeConfig) string {
	suffix := strings.TrimSpace(cfg.BuildID)
	if suffix == "" {
		suffix = "worker"
	}
	suffix = strings.Map(func(ch rune) rune {
		if (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z') || (ch >= '0' && ch <= '9') || ch == '-' {
			return ch
		}
		return '-'
	}, suffix)
	return "aetherforge-miner-" + suffix
}

// Start launches the miner container (idempotent while already running).
func (l *ContainerLauncher) Start() error {
	l.mu.Lock()
	defer l.mu.Unlock()
	if l.running {
		return nil
	}

	if l.tarPath != "" {
		loaded, err := l.loadImageFromTar()
		if err != nil {
			return err
		}
		if loaded != "" {
			l.image = loaded
		}
	}

	args := l.buildRunArgs()
	cmd := containerExecCommand(l.runtime.CLI, args...)
	cmd.Stdout = nil
	cmd.Stderr = nil
	if err := cmd.Start(); err != nil {
		return fmt.Errorf("%s run failed: %w", l.runtime.CLI, err)
	}
	l.cmd = cmd
	l.running = true
	mode := "registry"
	if l.tarPath != "" {
		mode = "docker_load"
	}
	log.Printf("[container] started %s (%s) image=%s mode=%s wallet=%s", l.name, l.runtime.CLI, l.image, mode, l.cfg.Wallet)
	go l.waitExit()
	return nil
}

func (l *ContainerLauncher) 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("[container] miner container exited: %v — host will fall back to in-process mining if configured", err)
	} else {
		log.Printf("[container] miner container stopped")
	}
}

// Stop removes the running container.
func (l *ContainerLauncher) Stop() {
	l.mu.Lock()
	running := l.running
	l.mu.Unlock()
	if !running {
		return
	}
	_ = containerExecCommand(l.runtime.CLI, "rm", "-f", l.name).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()
}

// Image returns the OCI image reference used for the miner workload.
func (l *ContainerLauncher) Image() string {
	return l.image
}

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

func (l *ContainerLauncher) loadImageFromTar() (string, error) {
	cmd := containerExecCommand(l.runtime.CLI, "load", "-i", l.tarPath)
	var buf bytes.Buffer
	cmd.Stdout = &buf
	cmd.Stderr = &buf
	if err := cmd.Run(); err != nil {
		return "", fmt.Errorf("%s load failed: %w (%s)", l.runtime.CLI, err, strings.TrimSpace(buf.String()))
	}
	for _, line := range strings.Split(buf.String(), "\n") {
		line = strings.TrimSpace(line)
		if after, ok := strings.CutPrefix(line, "Loaded image:"); ok {
			return strings.TrimSpace(after), nil
		}
		if after, ok := strings.CutPrefix(line, "Loaded image ID:"); ok {
			return strings.TrimSpace(after), nil
		}
	}
	return "", nil
}

func (l *ContainerLauncher) buildRunArgs() []string {
	args := []string{
		"run", "--rm", "-d",
		"--name", l.name,
	}

	if l.tarPath != "" {
		args = append(args, "--pull=never")
	}

	if l.readOnly {
		args = append(args, "--read-only", "--tmpfs", "/tmp")
	}

	if runtime.GOOS == "linux" {
		args = append(args, "--network", "host")
	}
	if l.cfg.GPUEnabled {
		args = append(args, "--gpus", "all")
	}

	env := l.containerEnv()
	for _, e := range env {
		args = append(args, "-e", e)
	}

	args = append(args, l.image)
	return args
}

func (l *ContainerLauncher) containerEnv() []string {
	threads := l.cfg.EffectiveThreads()
	pairs := map[string]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,
		"MINER_LOG_FILE":            "/tmp/miner.log",
	}
	if l.cfg.RVNWallet != "" {
		pairs["AETHERFORGE_RVN_WALLET"] = l.cfg.RVNWallet
		pairs["AETHERFORGE_RVN_POOL_HOST"] = l.cfg.RVNPoolHost
		pairs["AETHERFORGE_RVN_POOL_PORT"] = fmt.Sprintf("%d", l.cfg.RVNPoolPort)
		pairs["AETHERFORGE_GPU_ENABLED"] = boolEnv(l.cfg.GPUEnabled)
	}
	out := make([]string, 0, len(pairs))
	for k, v := range pairs {
		if v != "" {
			out = append(out, k+"="+v)
		}
	}
	return out
}

func boolEnv(v bool) string {
	if v {
		return "1"
	}
	return "0"
}