feat: add Agones allocation client

server/agones/allocation.go

@@ -0,0 +1,147 @@
+// Package agones contains the narrow provider adapter used by the allocator.
+// Domain policy and durable allocation records remain outside this package.
+package agones
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/cosmic-clash/cosmic-clash/server/domain"
+)
+
+type Client struct {
+	BaseURL   string
+	Namespace string
+	HTTP      *http.Client
+}
+
+type AllocatedServer struct {
+	Allocation domain.Allocation
+	Endpoint   string
+	GameServer string
+}
+
+type allocationRequest struct {
+	APIVersion string `json:"apiVersion"`
+	Kind       string `json:"kind"`
+	Spec       struct {
+		Selectors []struct {
+			MatchLabels map[string]string `json:"matchLabels"`
+		} `json:"selectors"`
+	} `json:"spec"`
+}
+
+type allocationResponse struct {
+	Status struct {
+		State          string `json:"state"`
+		GameServerName string `json:"gameServerName"`
+		Address        string `json:"address"`
+		Ports          []struct {
+			Name string `json:"name"`
+			Port int    `json:"port"`
+		} `json:"ports"`
+	} `json:"status"`
+}
+
+func (c Client) Allocate(ctx context.Context, request domain.AllocationRequest, labels map[string]string, now time.Time) (AllocatedServer, error) {
+	if c.HTTP == nil {
+		c.HTTP = http.DefaultClient
+	}
+	base, err := c.endpoint()
+	if err != nil {
+		return AllocatedServer{}, err
+	}
+	if request.AllocationID == "" || request.MatchID == "" || (request.Region != "EU" && request.Region != "NA") || request.Build == "" || request.Protocol <= 0 || (request.Transport != "enet" && request.Transport != "steam_sdr") || now.IsZero() {
+		return AllocatedServer{}, domain.ErrAllocationInput
+	}
+	if len(labels) == 0 {
+		return AllocatedServer{}, fmt.Errorf("allocation labels are required")
+	}
+	for key, value := range labels {
+		if key == "" || value == "" || strings.ContainsAny(key+value, "\r\n") {
+			return AllocatedServer{}, fmt.Errorf("invalid allocation label")
+		}
+	}
+	var body allocationRequest
+	body.APIVersion = "allocation.agones.dev/v1"
+	body.Kind = "GameServerAllocation"
+	body.Spec.Selectors = []struct {
+		MatchLabels map[string]string `json:"matchLabels"`
+	}{{MatchLabels: cloneLabels(labels)}}
+	encoded, err := json.Marshal(body)
+	if err != nil {
+		return AllocatedServer{}, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, base+"/apis/allocation.agones.dev/v1/namespaces/"+url.PathEscape(c.Namespace)+"/gameserverallocations", bytes.NewReader(encoded))
+	if err != nil {
+		return AllocatedServer{}, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	response, err := c.HTTP.Do(req)
+	if err != nil {
+		return AllocatedServer{}, err
+	}
+	defer response.Body.Close()
+	if response.StatusCode < 200 || response.StatusCode >= 300 {
+		return AllocatedServer{}, fmt.Errorf("Agones allocation returned %s", response.Status)
+	}
+	var decoded allocationResponse
+	decoder := json.NewDecoder(io.LimitReader(response.Body, 64<<10))
+	if err := decoder.Decode(&decoded); err != nil {
+		return AllocatedServer{}, fmt.Errorf("decode Agones allocation: %w", err)
+	}
+	if decoded.Status.State != "Allocated" || decoded.Status.GameServerName == "" || decoded.Status.Address == "" {
+		return AllocatedServer{}, fmt.Errorf("Agones allocation is incomplete")
+	}
+	port, err := selectPort(decoded.Status.Ports)
+	if err != nil {
+		return AllocatedServer{}, err
+	}
+	return AllocatedServer{Allocation: domain.Allocation{AllocationID: request.AllocationID, MatchID: request.MatchID, ServerID: decoded.Status.GameServerName, Region: request.Region, Build: request.Build, Protocol: request.Protocol, Transport: request.Transport, State: domain.ServerAllocated, AllocatedAt: now}, Endpoint: net.JoinHostPort(decoded.Status.Address, strconv.Itoa(port)), GameServer: decoded.Status.GameServerName}, nil
+}
+
+func (c Client) endpoint() (string, error) {
+	if c.Namespace == "" || strings.ContainsAny(c.Namespace, "/\r\n") {
+		return "", fmt.Errorf("invalid Agones namespace")
+	}
+	u, err := url.Parse(c.BaseURL)
+	if err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" || u.RawQuery != "" || u.Fragment != "" || u.Path != "" {
+		return "", fmt.Errorf("invalid Agones base URL")
+	}
+	return strings.TrimRight(c.BaseURL, "/"), nil
+}
+
+func selectPort(ports []struct {
+	Name string `json:"name"`
+	Port int    `json:"port"`
+}) (int, error) {
+	for _, port := range ports {
+		if port.Name == "default" {
+			if port.Port < 1 || port.Port > 65535 {
+				return 0, fmt.Errorf("Agones returned invalid default port")
+			}
+			return port.Port, nil
+		}
+	}
+	if len(ports) != 1 || ports[0].Port < 1 || ports[0].Port > 65535 {
+		return 0, fmt.Errorf("Agones returned no usable game port")
+	}
+	return ports[0].Port, nil
+}
+
+func cloneLabels(labels map[string]string) map[string]string {
+	copy := make(map[string]string, len(labels))
+	for key, value := range labels {
+		copy[key] = value
+	}
+	return copy
+}