feat: ModelRouter — unified OpenAI-compatible multi-source LLM gateway

- Lua adapters per upstream (transform_request/response/stream_chunk, build_headers signing hooks)
- AUTO priority routing with per-model kind (chat/image), explicit source/model routing
- Per-source concurrency caps with queueing, exponential backoff, AUTO failover
- OpenAI-compatible API: chat completions, SSE streaming, image generations, models
- Gateway key auth, web UI for adapter/source management, runtime persistence
- e2e test running the real binary against mocked upstreams

internal/core/core.go

@@ -0,0 +1,194 @@
+// Package core wires together the Lua VM, provider registry, scheduler and
+// runtime store and exposes management operations (hot reload, adapters,
+// sources) for the web UI and gateway.
+package core
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"llmsproxy/internal/config"
+	"llmsproxy/internal/lua"
+	"llmsproxy/internal/provider"
+	"llmsproxy/internal/scheduler"
+)
+
+// Core owns the running configuration and adapters.
+type Core struct {
+	cfg       *config.Config
+	vm        *lua.VM
+	store     *config.Store
+	scheduler *scheduler.Scheduler
+	registry  *provider.Registry
+}
+
+// New builds the core from a config file plus runtime overlay.
+func New(cfgPath string) (*Core, error) {
+	cfg, err := config.Load(cfgPath)
+	if err != nil {
+		return nil, err
+	}
+	return NewFromConfig(cfg)
+}
+
+// NewFromConfig builds the core from an already-loaded config.
+func NewFromConfig(cfg *config.Config) (*Core, error) {
+	c := &Core{cfg: cfg}
+	c.vm = lua.NewVM(cfg.AdapterDir)
+	if err := c.vm.Start(); err != nil {
+		return nil, fmt.Errorf("lua vm: %w", err)
+	}
+	c.store = config.NewStore(cfg.RuntimeFile)
+	if err := c.store.Load(); err != nil {
+		return nil, fmt.Errorf("runtime store: %w", err)
+	}
+	c.scheduler = scheduler.New(buildRetries(cfg))
+	if err := c.rebuildRegistry(); err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+func buildRetries(cfg *config.Config) int {
+	return len(cfg.Sources) // allow fallback across all sources
+}
+
+// VM exposes the Lua adapter runtime.
+func (c *Core) VM() *lua.VM { return c.vm }
+
+func (c *Core) Scheduler() *scheduler.Scheduler { return c.scheduler }
+
+func (c *Core) Registry() *provider.Registry { return c.registry }
+
+func (c *Core) DefaultModel() string { return c.cfg.DefaultModel }
+
+func (c *Core) GatewayKeys() []string { return c.cfg.GatewayKeys }
+
+func (c *Core) Listen() string { return c.cfg.Listen }
+
+// Config exposes the underlying configuration (read-only usage).
+func (c *Core) Config() *config.Config { return c.cfg }
+
+// mergedSources = base YAML sources + runtime sources (runtime wins by name).
+func (c *Core) mergedSources() []config.Source {
+	byName := map[string]config.Source{}
+	order := []string{}
+	for _, s := range c.cfg.Sources {
+		byName[s.Name] = s
+		order = append(order, s.Name)
+	}
+	for _, s := range c.store.List() {
+		if _, ok := byName[s.Name]; !ok {
+			order = append(order, s.Name)
+		}
+		byName[s.Name] = s
+	}
+	out := make([]config.Source, 0, len(order))
+	seen := map[string]bool{}
+	for _, n := range order {
+		if !seen[n] {
+			seen[n] = true
+			out = append(out, byName[n])
+		}
+	}
+	return out
+}
+
+func (c *Core) rebuildRegistry() error {
+	srcs := c.mergedSources()
+	providers := make([]*provider.Provider, 0, len(srcs))
+	for _, s := range srcs {
+		providers = append(providers, provider.New(s, c.vm))
+	}
+	if c.registry == nil {
+		c.registry = provider.NewRegistry(providers, c.cfg.DefaultModel)
+	} else {
+		c.registry.Replace(providers)
+	}
+	return nil
+}
+
+// Reload re-reads the runtime store and rebuilds sources (adapter reload is not
+// strictly needed since adapters are loaded into the VM at startup; uploaded
+// adapters are placed in the adapter dir and loaded by the web UI).
+func (c *Core) Reload() error {
+	if err := c.store.Load(); err != nil {
+		return err
+	}
+	return c.rebuildRegistry()
+}
+
+// ---- adapter management (web UI) ----
+
+func (c *Core) ListAdapters() []lua.APIAdapter { return c.vm.ListAdapters() }
+
+// UploadAdapter saves a new Lua adapter script to the adapter dir and loads it.
+func (c *Core) UploadAdapter(name, code string) error {
+	if name == "" {
+		return fmt.Errorf("adapter name required")
+	}
+	if err := os.MkdirAll(c.cfg.AdapterDir, 0755); err != nil {
+		return err
+	}
+	path := filepath.Join(c.cfg.AdapterDir, name+".lua")
+	if err := os.WriteFile(path, []byte(code), 0644); err != nil {
+		return err
+	}
+	if err := c.vm.LoadAdapter(path); err != nil {
+		return fmt.Errorf("load adapter: %w", err)
+	}
+	return nil
+}
+
+// RemoveAdapter deletes an adapter script and evicts it from the VM.
+func (c *Core) RemoveAdapter(name string) error {
+	path := filepath.Join(c.cfg.AdapterDir, name+".lua")
+	_ = os.Remove(path)
+	c.vm.RemoveAdapter(name)
+	return nil
+}
+
+// ---- source management (web UI) ----
+
+func (c *Core) AddSource(src config.Source) error {
+	if err := normalizeSource(&src); err != nil {
+		return err
+	}
+	if err := c.store.Upsert(src); err != nil {
+		return err
+	}
+	return c.rebuildRegistry()
+}
+
+func (c *Core) RemoveSource(name string) error {
+	if _, err := c.store.Remove(name); err != nil {
+		return err
+	}
+	return c.rebuildRegistry()
+}
+
+func (c *Core) Sources() []config.Source { return c.mergedSources() }
+
+func normalizeSource(s *config.Source) error {
+	if s.Name == "" || s.BaseURL == "" {
+		return fmt.Errorf("source requires name and base_url")
+	}
+	if len(s.Models) == 0 {
+		return fmt.Errorf("source requires at least one model")
+	}
+	if s.Adapter == "" {
+		s.Adapter = "openai"
+	}
+	if s.MaxConcurrent == 0 {
+		s.MaxConcurrent = 8
+	}
+	return nil
+}
+
+// Close releases resources.
+func (c *Core) Close() {
+	if c.vm != nil {
+		c.vm.Stop()
+	}
+}