feat(config): env-driven config with validation

internal/config/config_test.go

@@ -0,0 +1,58 @@
+package config
+
+import (
+	"testing"
+	"time"
+)
+
+func TestLoad(t *testing.T) {
+	tests := []struct {
+		name    string
+		env     map[string]string
+		want    Config
+		wantErr bool
+	}{
+		{
+			name: "valid anthropic",
+			env: map[string]string{
+				"CAPTCHA_LLM_PROVIDER": "anthropic",
+				"CAPTCHA_LLM_API_KEY":  "k",
+				"CAPTCHA_LLM_MODEL":    "claude-opus-4-8",
+			},
+			want: Config{
+				Provider: "anthropic", APIKey: "k", Model: "claude-opus-4-8",
+				LogLevel: "info", MaxTokens: 1024, Timeout: 60 * time.Second,
+			},
+		},
+		{
+			name:    "missing model",
+			env:     map[string]string{"CAPTCHA_LLM_PROVIDER": "openai", "CAPTCHA_LLM_API_KEY": "k"},
+			wantErr: true,
+		},
+		{
+			name:    "bad provider",
+			env:     map[string]string{"CAPTCHA_LLM_PROVIDER": "nope", "CAPTCHA_LLM_API_KEY": "k", "CAPTCHA_LLM_MODEL": "m"},
+			wantErr: true,
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			for k, v := range tc.env {
+				t.Setenv(k, v)
+			}
+			got, err := Load()
+			if tc.wantErr {
+				if err == nil {
+					t.Fatal("want error, got nil")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			if got != tc.want {
+				t.Fatalf("got %+v want %+v", got, tc.want)
+			}
+		})
+	}
+}