fn_registry/apps/dag_engine/api.go

package main

import (
	"io/fs"
	"net/http"
)

// RegisterAPI sets up all HTTP routes on the given mux.
func RegisterAPI(mux *http.ServeMux, executor *Executor, scheduler *Scheduler, hub *DagRunHub, frontendFS fs.FS) {
	// API routes.
	mux.HandleFunc("GET /api/dags", handleListDags(executor))
	mux.HandleFunc("GET /api/dags/{name}", handleGetDag(executor))
	mux.HandleFunc("POST /api/dags/{name}/run", handleRunDag(executor))

	mux.HandleFunc("GET /api/runs", handleListRuns(executor))
	mux.HandleFunc("GET /api/runs/{id}", handleGetRun(executor))

	// Function lookup proxy a registry.db (read-only).
	mux.HandleFunc("GET /api/functions/{id}", handleGetFunction())

	mux.HandleFunc("POST /api/scheduler/start", handleSchedulerStart(scheduler))
	mux.HandleFunc("POST /api/scheduler/stop", handleSchedulerStop(scheduler))
	mux.HandleFunc("GET /api/scheduler/status", handleSchedulerStatus(scheduler))

	// Live updates (WS hub).
	if hub != nil {
		mux.HandleFunc("GET /api/ws/dagruns", handleDagRunsWS(hub))
	}

	// Frontend SPA fallback.
	if frontendFS != nil {
		mux.Handle("/", spaHandler(frontendFS))
	}
}

// spaHandler serves static files from the embedded FS, falling back to index.html
// for unknown paths (SPA client-side routing).
func spaHandler(fsys fs.FS) http.Handler {
	fileServer := http.FileServer(http.FS(fsys))
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Try to serve the file directly.
		path := r.URL.Path
		if path == "/" {
			path = "index.html"
		} else {
			path = path[1:] // strip leading /
		}

		if _, err := fs.Stat(fsys, path); err != nil {
			// File not found — serve index.html for SPA routing.
			r.URL.Path = "/"
		}
		fileServer.ServeHTTP(w, r)
	})
}