Add Peer Model Support (#438)

This PR allows a single llama-swap to be the central proxy for models served by other inference servers. The peer servers can be another llama-swap or any API that supports the /v1/* inference endpoint.

Updates: #433, #299
Closes: #296

proxy/config/peer_test.go

@@ -0,0 +1,139 @@
+package config
+
+import (
+	"testing"
+
+	"gopkg.in/yaml.v3"
+)
+
+func TestPeerConfig_UnmarshalYAML(t *testing.T) {
+	tests := []struct {
+		name    string
+		yaml    string
+		wantErr string
+	}{
+		{
+			name: "valid config",
+			yaml: `
+proxy: http://192.168.1.23
+models:
+  - model_a
+  - model_b
+`,
+			wantErr: "",
+		},
+		{
+			name: "valid config with apiKey",
+			yaml: `
+proxy: https://openrouter.ai/api
+apiKey: sk-test-key
+models:
+  - meta-llama/llama-3.1-8b-instruct
+`,
+			wantErr: "",
+		},
+		{
+			name: "missing proxy",
+			yaml: `
+models:
+  - model_a
+`,
+			wantErr: "proxy is required",
+		},
+		{
+			name: "empty proxy",
+			yaml: `
+proxy: ""
+models:
+  - model_a
+`,
+			wantErr: "proxy is required",
+		},
+		{
+			name: "invalid proxy URL",
+			yaml: `
+proxy: "://invalid"
+models:
+  - model_a
+`,
+			wantErr: "invalid peer proxy URL",
+		},
+		{
+			name: "missing models",
+			yaml: `
+proxy: http://localhost:8080
+`,
+			wantErr: "peer models can not be empty",
+		},
+		{
+			name: "empty models",
+			yaml: `
+proxy: http://localhost:8080
+models: []
+`,
+			wantErr: "peer models can not be empty",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var config PeerConfig
+			err := yaml.Unmarshal([]byte(tt.yaml), &config)
+
+			if tt.wantErr == "" {
+				if err != nil {
+					t.Errorf("unexpected error: %v", err)
+				}
+			} else {
+				if err == nil {
+					t.Errorf("expected error containing %q, got nil", tt.wantErr)
+				} else if !contains(err.Error(), tt.wantErr) {
+					t.Errorf("expected error containing %q, got %q", tt.wantErr, err.Error())
+				}
+			}
+		})
+	}
+}
+
+func TestPeerConfig_ProxyURL(t *testing.T) {
+	yamlData := `
+proxy: http://192.168.1.23:8080/api
+apiKey: sk-test
+models:
+  - model_a
+`
+	var config PeerConfig
+	err := yaml.Unmarshal([]byte(yamlData), &config)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if config.ProxyURL == nil {
+		t.Fatal("ProxyURL should not be nil")
+	}
+
+	if config.ProxyURL.Host != "192.168.1.23:8080" {
+		t.Errorf("expected host %q, got %q", "192.168.1.23:8080", config.ProxyURL.Host)
+	}
+
+	if config.ProxyURL.Scheme != "http" {
+		t.Errorf("expected scheme %q, got %q", "http", config.ProxyURL.Scheme)
+	}
+
+	if config.ProxyURL.Path != "/api" {
+		t.Errorf("expected path %q, got %q", "/api", config.ProxyURL.Path)
+	}
+}
+
+func contains(s, substr string) bool {
+	return len(s) >= len(substr) && searchSubstring(s, substr)
+}
+
+func searchSubstring(s, substr string) bool {
+	for i := 0; i <= len(s)-len(substr); i++ {
+		if s[i:i+len(substr)] == substr {
+			return true
+		}
+	}
+	return false
+}