feat(webdemo): add database-backed usage dashboard

internal/webdemo/database_handler.go

@@ -0,0 +1,84 @@
+package webdemo
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"path/filepath"
+
+	"billing/internal/plugin"
+)
+
+// DatabaseInput exposes the billing management API against a standalone SQLite copy.
+type DatabaseInput struct {
+	app *plugin.App
+}
+
+func NewDatabaseInput(databasePath string) (*DatabaseInput, error) {
+	absolutePath, err := filepath.Abs(databasePath)
+	if err != nil {
+		return nil, fmt.Errorf("resolve demo database path: %w", err)
+	}
+	app := plugin.NewApp()
+	config := fmt.Sprintf("database_path: %q\nenabled: true\ncodex_only: false\n", absolutePath)
+	lifecycle, err := json.Marshal(plugin.LifecycleRequest{ConfigYAML: []byte(config), SchemaVersion: plugin.SchemaVersion})
+	if err != nil {
+		return nil, fmt.Errorf("encode demo lifecycle request: %w", err)
+	}
+	if _, err := app.HandleMethod(plugin.MethodPluginRegister, lifecycle); err != nil {
+		app.Shutdown()
+		return nil, fmt.Errorf("open demo database: %w", err)
+	}
+	return &DatabaseInput{app: app}, nil
+}
+
+func (input *DatabaseInput) Close() error {
+	input.app.Shutdown()
+	return nil
+}
+
+func (input *DatabaseInput) ServeHTTP(response http.ResponseWriter, request *http.Request) {
+	body, err := io.ReadAll(request.Body)
+	if err != nil {
+		writeJSON(response, http.StatusBadRequest, map[string]any{"error": map[string]string{"code": "request_body_error", "message": err.Error()}})
+		return
+	}
+	wireRequest, err := json.Marshal(plugin.ManagementRequest{
+		Method: request.Method, Path: request.URL.Path, Headers: request.Header.Clone(), Query: request.URL.Query(), Body: body,
+	})
+	if err != nil {
+		writeJSON(response, http.StatusInternalServerError, map[string]any{"error": map[string]string{"code": "request_encode_error", "message": err.Error()}})
+		return
+	}
+	raw, err := input.app.HandleMethod(plugin.MethodManagementHandle, wireRequest)
+	if err != nil {
+		writeJSON(response, http.StatusInternalServerError, map[string]any{"error": map[string]string{"code": "management_error", "message": err.Error()}})
+		return
+	}
+	var envelope plugin.Envelope
+	if err := json.Unmarshal(raw, &envelope); err != nil || !envelope.OK {
+		message := "invalid management response"
+		if envelope.Error != nil {
+			message = envelope.Error.Message
+		}
+		writeJSON(response, http.StatusInternalServerError, map[string]any{"error": map[string]string{"code": "management_envelope_error", "message": message}})
+		return
+	}
+	var result plugin.ManagementResponse
+	if err := json.Unmarshal(envelope.Result, &result); err != nil {
+		writeJSON(response, http.StatusInternalServerError, map[string]any{"error": map[string]string{"code": "response_decode_error", "message": err.Error()}})
+		return
+	}
+	for name, values := range result.Headers {
+		for _, value := range values {
+			response.Header().Add(name, value)
+		}
+	}
+	status := result.StatusCode
+	if status == 0 {
+		status = http.StatusOK
+	}
+	response.WriteHeader(status)
+	_, _ = response.Write(result.Body)
+}