feat: scaffold traefik-llmgateway plugin skeleton with manifest

llmgateway.go

@@ -0,0 +1,134 @@
+// Package traefikllmgateway implements a Traefik Yaegi middleware plugin: a
+// multi-provider LLM gateway with groups, per-user API keys, request/token/
+// cost limits, and an MCP/A2A registry and proxy.
+package traefikllmgateway
+
+import (
+	"context"
+	"errors"
+	"net/http"
+)
+
+// Config is the plugin's dynamic configuration, populated by Traefik from
+// the middleware's YAML/testData. Every limit or list field follows the
+// convention: zero/empty/omitted means unlimited/all.
+type Config struct {
+	Providers          map[string]*ProviderConfig `json:"providers,omitempty"`
+	Groups             map[string]*GroupConfig    `json:"groups,omitempty"`
+	Pricing            map[string]*ModelPricing   `json:"pricing,omitempty"`
+	MCPServers         map[string]*TargetConfig   `json:"mcpServers,omitempty"`
+	Agents             map[string]*AgentConfig    `json:"agents,omitempty"`
+	Users              *UsersConfig               `json:"users,omitempty"`
+	Redis              *RedisConfig               `json:"redis,omitempty"`
+	PassthroughUnknown bool                       `json:"passthroughUnknown,omitempty"`
+}
+
+// ProviderConfig describes one upstream LLM provider.
+type ProviderConfig struct {
+	Type              string   `json:"type"`
+	BaseURL           string   `json:"baseUrl,omitempty"`
+	APIKey            string   `json:"apiKey"`
+	DiscoveryInterval string   `json:"discoveryInterval,omitempty"`
+	Models            []string `json:"models,omitempty"`
+	Discovery         bool     `json:"discovery,omitempty"`
+}
+
+// GroupConfig describes a group's access and limits. Empty/omitted
+// Providers, Models, MCPServers, Agents mean all are allowed.
+type GroupConfig struct {
+	Limits     *LimitsConfig `json:"limits,omitempty"`
+	Providers  []string      `json:"providers,omitempty"`
+	Models     []string      `json:"models,omitempty"`
+	MCPServers []string      `json:"mcpServers,omitempty"`
+	Agents     []string      `json:"agents,omitempty"`
+}
+
+// LimitsConfig holds request/token/cost limits. Zero means unlimited.
+type LimitsConfig struct {
+	RequestsPerMinute int64   `json:"requestsPerMinute,omitempty"`
+	RequestsPerDay    int64   `json:"requestsPerDay,omitempty"`
+	TokensPerDay      int64   `json:"tokensPerDay,omitempty"`
+	TokensPerMonth    int64   `json:"tokensPerMonth,omitempty"`
+	CostPerDayUSD     float64 `json:"costPerDayUSD,omitempty"`
+	CostPerMonthUSD   float64 `json:"costPerMonthUSD,omitempty"`
+}
+
+// UsersConfig combines inline users with an optional file-backed source.
+type UsersConfig struct {
+	File   string        `json:"file,omitempty"`
+	Inline []*UserConfig `json:"inline,omitempty"`
+}
+
+// UserConfig describes one API-key holder.
+type UserConfig struct {
+	Limits *LimitsConfig `json:"limits,omitempty"`
+	Name   string        `json:"name"`
+	Group  string        `json:"group"`
+	APIKey string        `json:"apiKey"`
+}
+
+// RedisConfig configures the distributed limit-state backend.
+type RedisConfig struct {
+	FailOpen *bool  `json:"failOpen,omitempty"`
+	Address  string `json:"address"`
+	Password string `json:"password,omitempty"`
+	DB       int    `json:"db,omitempty"`
+}
+
+// ModelPricing overrides the built-in per-model price table.
+type ModelPricing struct {
+	InputPerM  float64 `json:"inputPerM"`
+	OutputPerM float64 `json:"outputPerM"`
+}
+
+// TargetConfig is a proxied upstream target (MCP server).
+type TargetConfig struct {
+	URL string `json:"url"`
+}
+
+// AgentConfig is a proxied A2A agent.
+type AgentConfig struct {
+	URL  string `json:"url"`
+	Card string `json:"card,omitempty"`
+}
+
+// CreateConfig returns a Config populated with the plugin's defaults.
+func CreateConfig() *Config {
+	return &Config{}
+}
+
+// Gateway is the Traefik middleware handler.
+type Gateway struct {
+	next http.Handler
+	cfg  *Config
+	name string
+	// wired in later tasks: auth *authStore, limiter *limiter,
+	// registry *modelRegistry, adapters map[string]providerAdapter
+}
+
+// New creates the middleware. NOTE: no tail call — Yaegi zeroes
+// multi-value tail-call returns across the reflect boundary.
+func New(ctx context.Context, next http.Handler, config *Config, name string) (http.Handler, error) {
+	g, err := newGateway(ctx, next, config, name)
+	if err != nil {
+		return nil, err
+	}
+	return g, nil
+}
+
+func newGateway(ctx context.Context, next http.Handler, config *Config, name string) (*Gateway, error) {
+	if config == nil || len(config.Providers) == 0 {
+		return nil, errors.New("llmgateway: at least one provider must be configured")
+	}
+	return &Gateway{next: next, name: name, cfg: config}, nil
+}
+
+// ServeHTTP is the internal router. It grows in later tasks.
+func (g *Gateway) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	defer recoverPanic(w, g)
+	if g.cfg.PassthroughUnknown {
+		g.next.ServeHTTP(w, r)
+		return
+	}
+	writeOAIError(w, http.StatusNotFound, "invalid_request_error", "unknown route")
+}