package docker

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"os/exec"
	"strings"
	"time"
)

// DockerClient communicates with the Docker daemon via Unix socket.
type DockerClient struct {
	httpClient *http.Client
	baseURL    string
}

// NewDockerClient creates a client talking to /var/run/docker.sock.
func NewDockerClient() *DockerClient {
	transport := &http.Transport{
		DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
			return (&net.Dialer{Timeout: 5 * time.Second}).DialContext(ctx, "unix", "/var/run/docker.sock")
		},
	}
	return &DockerClient{
		httpClient: &http.Client{Transport: transport, Timeout: 30 * time.Second},
		baseURL:    "http://localhost",
	}
}

// ─── HTTP helpers ─────────────────────────────────────────────────────────────

func (c *DockerClient) get(path string, out interface{}) error {
	resp, err := c.httpClient.Get(c.baseURL + path)
	if err != nil {
		return fmt.Errorf("docker GET %s: %w", path, err)
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode >= 400 {
		return fmt.Errorf("docker GET %s: status %d: %s", path, resp.StatusCode, string(body))
	}
	return json.Unmarshal(body, out)
}

func (c *DockerClient) post(path string, payload interface{}, out interface{}) error {
	b, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	resp, err := c.httpClient.Post(c.baseURL+path, "application/json", bytes.NewReader(b))
	if err != nil {
		return fmt.Errorf("docker POST %s: %w", path, err)
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode >= 400 {
		return fmt.Errorf("docker POST %s: status %d: %s", path, resp.StatusCode, string(body))
	}
	if out != nil && len(body) > 0 {
		return json.Unmarshal(body, out)
	}
	return nil
}

func (c *DockerClient) postUpdate(path string, version int, payload interface{}) error {
	b, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	url := fmt.Sprintf("%s%s?version=%d", c.baseURL, path, version)
	req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(b))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("docker POST(update) %s: %w", path, err)
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode >= 400 {
		return fmt.Errorf("docker POST(update) %s: status %d: %s", path, resp.StatusCode, string(body))
	}
	return nil
}

// ─── Swarm Node Types ─────────────────────────────────────────────────────────

type SwarmNode struct {
	ID          string         `json:"ID"`
	Description NodeDescription `json:"Description"`
	Status      NodeStatus     `json:"Status"`
	ManagerStatus *ManagerStatus `json:"ManagerStatus,omitempty"`
	Spec        NodeSpec       `json:"Spec"`
	UpdatedAt   time.Time      `json:"UpdatedAt"`
	CreatedAt   time.Time      `json:"CreatedAt"`
	Version     VersionInfo    `json:"Version"`
}

type VersionInfo struct {
	Index int `json:"Index"`
}

type NodeDescription struct {
	Hostname  string    `json:"Hostname"`
	Platform  Platform  `json:"Platform"`
	Resources Resources `json:"Resources"`
	Engine    Engine    `json:"Engine"`
}

type Platform struct {
	Architecture string `json:"Architecture"`
	OS           string `json:"OS"`
}

type Resources struct {
	NanoCPUs    int64 `json:"NanoCPUs"`
	MemoryBytes int64 `json:"MemoryBytes"`
}

type Engine struct {
	EngineVersion string `json:"EngineVersion"`
}

type NodeStatus struct {
	State   string `json:"State"`
	Addr    string `json:"Addr"`
	Message string `json:"Message"`
}

type ManagerStatus struct {
	Addr         string `json:"Addr"`
	Leader       bool   `json:"Leader"`
	Reachability string `json:"Reachability"`
}

type NodeSpec struct {
	Role         string            `json:"Role"`
	Availability string            `json:"Availability"`
	Labels       map[string]string `json:"Labels"`
}

// ─── Swarm Service Types ──────────────────────────────────────────────────────

type SwarmService struct {
	ID          string          `json:"ID"`
	Spec        ServiceSpec     `json:"Spec"`
	ServiceStatus *ServiceStatus `json:"ServiceStatus,omitempty"`
	UpdatedAt   time.Time       `json:"UpdatedAt"`
	CreatedAt   time.Time       `json:"CreatedAt"`
	Version     VersionInfo     `json:"Version"`
}

type ServiceSpec struct {
	Name         string            `json:"Name"`
	Mode         ServiceMode       `json:"Mode"`
	TaskTemplate TaskTemplate      `json:"TaskTemplate"`
	EndpointSpec *EndpointSpec     `json:"EndpointSpec,omitempty"`
	Labels       map[string]string `json:"Labels"`
	Networks     []NetworkAttachment `json:"Networks,omitempty"`
}

type NetworkAttachment struct {
	Target  string   `json:"Target"`
	Aliases []string `json:"Aliases,omitempty"`
}

type ServiceMode struct {
	Replicated *ReplicatedService `json:"Replicated,omitempty"`
	Global     *struct{}          `json:"Global,omitempty"`
}

type ReplicatedService struct {
	Replicas int `json:"Replicas"`
}

type TaskTemplate struct {
	ContainerSpec ContainerSpec `json:"ContainerSpec"`
	Resources     *TaskResources `json:"Resources,omitempty"`
	Placement     *Placement    `json:"Placement,omitempty"`
}

type ContainerSpec struct {
	Image  string   `json:"Image"`
	Env    []string `json:"Env,omitempty"`
	Labels map[string]string `json:"Labels,omitempty"`
}

type TaskResources struct {
	Limits       *ResourceSpec `json:"Limits,omitempty"`
	Reservations *ResourceSpec `json:"Reservations,omitempty"`
}

type ResourceSpec struct {
	NanoCPUs    int64 `json:"NanoCPUs,omitempty"`
	MemoryBytes int64 `json:"MemoryBytes,omitempty"`
}

type Placement struct {
	Constraints []string `json:"Constraints,omitempty"`
}

type EndpointSpec struct {
	Ports []PortConfig `json:"Ports,omitempty"`
}

type PortConfig struct {
	Protocol      string `json:"Protocol"`
	TargetPort    int    `json:"TargetPort"`
	PublishedPort int    `json:"PublishedPort"`
	PublishMode   string `json:"PublishMode"`
}

type ServiceStatus struct {
	RunningTasks   int `json:"RunningTasks"`
	DesiredTasks   int `json:"DesiredTasks"`
	CompletedTasks int `json:"CompletedTasks"`
}

// ─── Swarm Task Types ─────────────────────────────────────────────────────────

type SwarmTask struct {
	ID          string      `json:"ID"`
	ServiceID   string      `json:"ServiceID"`
	NodeID      string      `json:"NodeID"`
	Spec        TaskSpec    `json:"Spec"`
	Status      TaskStatus  `json:"Status"`
	Slot        int         `json:"Slot"`
	UpdatedAt   time.Time   `json:"UpdatedAt"`
	CreatedAt   time.Time   `json:"CreatedAt"`
}

type TaskSpec struct {
	ContainerSpec ContainerSpec `json:"ContainerSpec"`
}

type TaskStatus struct {
	Timestamp   time.Time       `json:"Timestamp"`
	State       string          `json:"State"`
	Message     string          `json:"Message"`
	ContainerStatus *ContainerTaskStatus `json:"ContainerStatus,omitempty"`
}

type ContainerTaskStatus struct {
	ContainerID string `json:"ContainerID"`
	PID         int    `json:"PID"`
}

// ─── Swarm Info / Tokens ──────────────────────────────────────────────────────

type DockerInfo struct {
	Swarm SwarmInfo `json:"Swarm"`
}

type SwarmInfo struct {
	NodeID           string `json:"NodeID"`
	LocalNodeState   string `json:"LocalNodeState"`
	ControlAvailable bool   `json:"ControlAvailable"`
	Managers         int    `json:"Managers"`
	Nodes            int    `json:"Nodes"`
	RemoteManagers   []RemoteManager `json:"RemoteManagers"`
}

type RemoteManager struct {
	NodeID string `json:"NodeID"`
	Addr   string `json:"Addr"`
}

type SwarmSpec struct {
	JoinTokens JoinTokens `json:"JoinTokens"`
	ID         string     `json:"ID"`
}

type JoinTokens struct {
	Worker  string `json:"Worker"`
	Manager string `json:"Manager"`
}

// ─── Container types ──────────────────────────────────────────────────────────

type Container struct {
	ID      string            `json:"Id"`
	Names   []string          `json:"Names"`
	Image   string            `json:"Image"`
	State   string            `json:"State"`
	Status  string            `json:"Status"`
	Labels  map[string]string `json:"Labels"`
}

type ContainerStats struct {
	CPUStats    CPUStats    `json:"cpu_stats"`
	PreCPUStats CPUStats    `json:"precpu_stats"`
	MemoryStats MemoryStats `json:"memory_stats"`
}

type CPUStats struct {
	CPUUsage       CPUUsage `json:"cpu_usage"`
	SystemCPUUsage int64    `json:"system_cpu_usage"`
	OnlineCPUs     int      `json:"online_cpus"`
}

type CPUUsage struct {
	TotalUsage  int64   `json:"total_usage"`
	PercpuUsage []int64 `json:"percpu_usage"`
}

type MemoryStats struct {
	Usage    int64            `json:"usage"`
	MaxUsage int64            `json:"max_usage"`
	Limit    int64            `json:"limit"`
	Stats    map[string]int64 `json:"stats"`
}

// ─── Methods: Swarm info ──────────────────────────────────────────────────────

func (c *DockerClient) IsSwarmActive() bool {
	var info DockerInfo
	if err := c.get("/v1.44/info", &info); err != nil {
		return false
	}
	return info.Swarm.LocalNodeState == "active"
}

func (c *DockerClient) GetSwarmInfo() (*DockerInfo, error) {
	var info DockerInfo
	if err := c.get("/v1.44/info", &info); err != nil {
		return nil, err
	}
	return &info, nil
}

// GetJoinTokens returns the Swarm worker and manager join tokens.
// Requires this node to be a swarm manager.
func (c *DockerClient) GetJoinTokens() (*SwarmSpec, error) {
	var spec SwarmSpec
	if err := c.get("/v1.44/swarm", &spec); err != nil {
		return nil, err
	}
	return &spec, nil
}

// GetManagerAddr returns the advertise address (IP:2377) for joining this swarm.
func (c *DockerClient) GetManagerAddr() string {
	info, err := c.GetSwarmInfo()
	if err != nil || len(info.Swarm.RemoteManagers) == 0 {
		return ""
	}
	return info.Swarm.RemoteManagers[0].Addr
}

// ─── Methods: Nodes ───────────────────────────────────────────────────────────

func (c *DockerClient) ListNodes() ([]SwarmNode, error) {
	var nodes []SwarmNode
	if err := c.get("/v1.44/nodes", &nodes); err != nil {
		return nil, err
	}
	return nodes, nil
}

// UpdateNodeAvailability sets a node's availability (active|pause|drain).
func (c *DockerClient) UpdateNodeAvailability(nodeID, availability string) error {
	// First get current node spec + version
	var node SwarmNode
	if err := c.get("/v1.44/nodes/"+nodeID, &node); err != nil {
		return err
	}
	node.Spec.Availability = availability
	return c.postUpdate("/v1.44/nodes/"+nodeID+"/update", node.Version.Index, node.Spec)
}

// AddNodeLabel adds a label to a swarm node.
func (c *DockerClient) AddNodeLabel(nodeID, key, value string) error {
	var node SwarmNode
	if err := c.get("/v1.44/nodes/"+nodeID, &node); err != nil {
		return err
	}
	if node.Spec.Labels == nil {
		node.Spec.Labels = map[string]string{}
	}
	node.Spec.Labels[key] = value
	return c.postUpdate("/v1.44/nodes/"+nodeID+"/update", node.Version.Index, node.Spec)
}

// ─── Methods: Services ────────────────────────────────────────────────────────

// ListServices returns all swarm services, optionally filtered by label.
func (c *DockerClient) ListServices() ([]SwarmService, error) {
	var services []SwarmService
	// Include ServiceStatus so running/desired replicas are returned
	if err := c.get("/v1.44/services?status=true", &services); err != nil {
		return nil, err
	}
	return services, nil
}

// GetService returns a single service by ID or name.
func (c *DockerClient) GetService(idOrName string) (*SwarmService, error) {
	var svc SwarmService
	if err := c.get("/v1.44/services/"+idOrName+"?status=true", &svc); err != nil {
		return nil, err
	}
	return &svc, nil
}

// ScaleService updates the replica count for a replicated service.
func (c *DockerClient) ScaleService(idOrName string, replicas int) error {
	svc, err := c.GetService(idOrName)
	if err != nil {
		return err
	}
	if svc.Spec.Mode.Replicated == nil {
		return fmt.Errorf("service %s is not in replicated mode", idOrName)
	}
	svc.Spec.Mode.Replicated.Replicas = replicas
	return c.postUpdate(
		"/v1.44/services/"+svc.ID+"/update",
		svc.Version.Index,
		svc.Spec,
	)
}

// ListServiceTasks returns all tasks for a given service.
func (c *DockerClient) ListServiceTasks(serviceID string) ([]SwarmTask, error) {
	var tasks []SwarmTask
	filter := fmt.Sprintf(`{"service":["%s"]}`, serviceID)
	path := "/v1.44/tasks?filters=" + urlEncode(filter)
	if err := c.get(path, &tasks); err != nil {
		return nil, err
	}
	return tasks, nil
}

// ListAllTasks returns all swarm tasks (across services).
func (c *DockerClient) ListAllTasks() ([]SwarmTask, error) {
	var tasks []SwarmTask
	if err := c.get("/v1.44/tasks", &tasks); err != nil {
		return nil, err
	}
	return tasks, nil
}

// CreateAgentService deploys a new swarm service for an AI agent.
// image: container image, name: service name, replicas: initial count,
// env: environment variables, port: optional published port (0 = none).
// CreateAgentServiceOpts holds options for deploying an agent Swarm service.
type CreateAgentServiceOpts struct {
	Name     string
	Image    string
	Replicas int
	Env      []string
	Port     int
	Networks []string // overlay network names/IDs to attach
	Labels   map[string]string
}

func (c *DockerClient) CreateAgentService(name, image string, replicas int, env []string, port int) (*SwarmService, error) {
	return c.CreateAgentServiceFull(CreateAgentServiceOpts{
		Name:     name,
		Image:    image,
		Replicas: replicas,
		Env:      env,
		Port:     port,
	})
}

func (c *DockerClient) CreateAgentServiceFull(opts CreateAgentServiceOpts) (*SwarmService, error) {
	labels := map[string]string{
		"goclaw.agent": "true",
		"goclaw.name":  opts.Name,
	}
	for k, v := range opts.Labels {
		labels[k] = v
	}
	spec := ServiceSpec{
		Name: opts.Name,
		Mode: ServiceMode{
			Replicated: &ReplicatedService{Replicas: opts.Replicas},
		},
		TaskTemplate: TaskTemplate{
			ContainerSpec: ContainerSpec{
				Image: opts.Image,
				Env:   opts.Env,
			},
		},
		Labels: labels,
	}
	if opts.Port > 0 {
		spec.EndpointSpec = &EndpointSpec{
			Ports: []PortConfig{
				{
					Protocol:    "tcp",
					TargetPort:  opts.Port,
					PublishMode: "ingress",
				},
			},
		}
	}
	if len(opts.Networks) > 0 {
		for _, net := range opts.Networks {
			spec.Networks = append(spec.Networks, NetworkAttachment{
				Target:  net,
				Aliases: []string{opts.Name},
			})
		}
	}
	var created struct {
		ID string `json:"ID"`
	}
	if err := c.post("/v1.44/services/create", spec, &created); err != nil {
		return nil, err
	}
	return c.GetService(created.ID)
}

// RemoveService removes a swarm service by ID or name.
func (c *DockerClient) RemoveService(idOrName string) error {
	req, err := http.NewRequest(http.MethodDelete, c.baseURL+"/v1.44/services/"+urlEncode(idOrName), nil)
	if err != nil {
		return err
	}
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("docker DELETE service %s: %w", idOrName, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 400 {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("docker DELETE service %s: status %d: %s", idOrName, resp.StatusCode, string(body))
	}
	return nil
}

// GetServiceLastActivity returns the most recent task update time for a service.
// Used to determine whether a service is idle.
func (c *DockerClient) GetServiceLastActivity(serviceID string) (time.Time, error) {
	tasks, err := c.ListServiceTasks(serviceID)
	if err != nil {
		return time.Time{}, err
	}
	var latest time.Time
	for _, t := range tasks {
		if t.UpdatedAt.After(latest) {
			latest = t.UpdatedAt
		}
	}
	return latest, nil
}

// ─── Methods: Containers ─────────────────────────────────────────────────────

func (c *DockerClient) ListContainers() ([]Container, error) {
	var containers []Container
	if err := c.get("/v1.44/containers/json?all=false", &containers); err != nil {
		return nil, err
	}
	return containers, nil
}

func (c *DockerClient) GetContainerStats(containerID string) (*ContainerStats, error) {
	var stats ContainerStats
	if err := c.get(fmt.Sprintf("/v1.44/containers/%s/stats?stream=false", containerID), &stats); err != nil {
		return nil, err
	}
	return &stats, nil
}

// ─── Host Shell execution ─────────────────────────────────────────────────────
// The gateway runs inside a container but has /var/run/docker.sock mounted.
// We use `docker exec` against the host PID namespace via a privileged helper,
// OR simply run commands via the docker socket by exec-ing into the gateway
// container's own shell with nsenter to reach PID 1 on the host.
//
// Approach: use `nsenter -t 1 -m -u -i -n -p -- <cmd>` via the host PID namespace.
// This requires the container to run with --privileged or SYS_PTRACE capability
// and PID namespace sharing. We add that to docker-compose.yml.
//
// Alternative (safer): exec into host via SSH or a privileged sidecar.
// For now we use nsenter which works when pid:host and privileged: true.

// ExecOnHost runs a shell command on the host via nsenter into PID 1.
// Returns combined stdout+stderr.
func ExecOnHost(command string) (string, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	// Try nsenter (requires pid:host + SYS_ADMIN or privileged)
	cmd := exec.CommandContext(ctx, "nsenter", "-t", "1", "-m", "-u", "-i", "-n", "-p", "--",
		"sh", "-c", command)
	var out bytes.Buffer
	var stderr bytes.Buffer
	cmd.Stdout = &out
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		// If nsenter fails, fall back to running in container scope
		cmd2 := exec.CommandContext(ctx, "sh", "-c", command)
		var out2 bytes.Buffer
		var stderr2 bytes.Buffer
		cmd2.Stdout = &out2
		cmd2.Stderr = &stderr2
		if err2 := cmd2.Run(); err2 != nil {
			combined := out2.String() + stderr2.String()
			if combined == "" {
				combined = err2.Error()
			}
			return combined, err2
		}
		return out2.String() + stderr2.String(), nil
	}
	return out.String() + stderr.String(), nil
}

// ExecDockerCLI runs `docker <args>` on the host by calling the docker socket.
// Since we have the socket mounted, we can exec docker commands directly
// using the docker CLI binary if available.
func ExecDockerCLI(args ...string) (string, error) {
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	cmd := exec.CommandContext(ctx, "docker", args...)
	var out, stderr bytes.Buffer
	cmd.Stdout = &out
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		return out.String() + stderr.String(), err
	}
	return out.String(), nil
}

// CalcCPUPercent computes CPU% from stats snapshot.
func CalcCPUPercent(stats *ContainerStats) float64 {
	cpuDelta := float64(stats.CPUStats.CPUUsage.TotalUsage) - float64(stats.PreCPUStats.CPUUsage.TotalUsage)
	systemDelta := float64(stats.CPUStats.SystemCPUUsage) - float64(stats.PreCPUStats.SystemCPUUsage)
	numCPU := float64(stats.CPUStats.OnlineCPUs)
	if numCPU == 0 {
		numCPU = float64(len(stats.CPUStats.CPUUsage.PercpuUsage))
	}
	if systemDelta > 0 && cpuDelta > 0 {
		return (cpuDelta / systemDelta) * numCPU * 100.0
	}
	return 0
}

// ─── Helpers ──────────────────────────────────────────────────────────────────

func urlEncode(s string) string {
	var b strings.Builder
	for _, r := range s {
		switch {
		case r >= 'A' && r <= 'Z', r >= 'a' && r <= 'z', r >= '0' && r <= '9',
			r == '-', r == '_', r == '.', r == '~':
			b.WriteRune(r)
		default:
			b.WriteString(fmt.Sprintf("%%%02X", r))
		}
	}
	return b.String()
}