feat: add Go migration compatibility foundation

backend/internal/application/application.go

@@ -0,0 +1,79 @@
+// Package application composes the Go backend foundation Modules.
+package application
+
+import (
+	"context"
+	"net/http"
+	"os"
+
+	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/httpapi"
+	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/postgres"
+)
+
+type Options struct {
+	Context  context.Context
+	Getenv   postgres.Getenv
+	ReadFile postgres.ReadFile
+}
+
+type App struct {
+	handler http.Handler
+	db      *postgres.Module
+}
+
+func New(options Options) (*App, error) {
+	ctx := options.Context
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	getenv := options.Getenv
+	if getenv == nil {
+		getenv = os.Getenv
+	}
+	readFile := options.ReadFile
+	if readFile == nil {
+		readFile = os.ReadFile
+	}
+
+	config, err := postgres.ParseConfig(getenv, readFile)
+	if err != nil {
+		return nil, err
+	}
+	database, err := postgres.Open(ctx, config)
+	if err != nil {
+		return nil, err
+	}
+	readiness := databaseReadiness{config: config, store: database.Store}
+	return &App{
+		db:      database,
+		handler: httpapi.NewHandler(readiness),
+	}, nil
+}
+
+func (app *App) Handler() http.Handler {
+	return app.handler
+}
+
+func (app *App) Close() {
+	if app.db != nil {
+		app.db.Close()
+	}
+}
+
+type databaseReadiness struct {
+	config postgres.Config
+	store  *postgres.Store
+}
+
+func (adapter databaseReadiness) Status() httpapi.DatabaseStatus {
+	configured := adapter.config.Backend == postgres.BackendLocal || adapter.config.DatabaseURL != ""
+	return httpapi.DatabaseStatus{
+		Backend:    string(adapter.config.Backend),
+		Configured: configured,
+	}
+}
+
+func (adapter databaseReadiness) Ready(ctx context.Context) (httpapi.DatabaseStatus, error) {
+	status := adapter.Status()
+	return status, adapter.store.Readiness(ctx)
+}