homelab-frontend/internal/serviceadapter/router.go

package serviceadapter

import (
	"fmt"
	"net"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"

	"forgejo.riotpiao.com/rock/homelab-frontend/internal/auth"
	"forgejo.riotpiao.com/rock/homelab-frontend/internal/problem"
)

// Dispatcher handles X-Service based routing to service adapters.
type Dispatcher struct {
	registry   *Registry
	validators map[string]*auth.Validator // Per-service JWT validators
}

// NewDispatcher creates a new service adapter dispatcher with Authentik JWT validators.
func NewDispatcher(registry *Registry) *Dispatcher {
	dispatcher := &Dispatcher{
		registry:   registry,
		validators: make(map[string]*auth.Validator),
	}

	// Create validators for all registered services
	for _, adapter := range registry.List() {
		dispatcher.validators[adapter.ServiceName] = auth.NewValidator(adapter.ServiceName)
	}

	return dispatcher
}

// Matches returns true if the request should be dispatched based on X-Service header.
func (d *Dispatcher) Matches(r *http.Request) bool {
	return r.Header.Get("X-Service") != ""
}

// Dispatch routes a request to the appropriate adapter.
// Returns a problem document if the adapter or resource is not found.
func (d *Dispatcher) Dispatch(w http.ResponseWriter, r *http.Request) {
	serviceName := r.Header.Get("X-Service")
	if serviceName == "" {
		// No X-Service header — this shouldn't happen if Matches() was called
		d.writeError(w, problem.BadRequest("X-Service header required"))
		return
	}

	// Look up service adapter
	adapter := d.registry.Get(serviceName)
	if adapter == nil {
		p := problem.NotFound(fmt.Sprintf("service '%s' not found", serviceName))
		_ = p.Write(w)
		return
	}

	// Get resource and method from request
	resourceName := r.Header.Get("X-Resource")
	if resourceName == "" {
		d.writeError(w, problem.BadRequest("X-Resource header required"))
		return
	}

	// Find resource
	var resource *Resource
	for i := range adapter.Spec.Resources {
		if adapter.Spec.Resources[i].Name == resourceName {
			resource = &adapter.Spec.Resources[i]
			break
		}
	}

	if resource == nil {
		p := problem.NotFound(fmt.Sprintf("resource '%s' not found in service '%s'", resourceName, serviceName))
		_ = p.Write(w)
		return
	}

	// Find method matching HTTP verb
	var method *Method
	for i := range resource.Methods {
		if resource.Methods[i].Verb == r.Method {
			method = &resource.Methods[i]
			break
		}
	}

	if method == nil {
		p := problem.NotFound(fmt.Sprintf("method %s not defined for resource '%s'", r.Method, resourceName))
		_ = p.Write(w)
		return
	}

	// Check auth requirements using JWT validation
	requiredCapability := ""
	auth := resource.Auth
	if auth == nil {
		auth = &adapter.Spec.Auth
	}
	if method.Auth != nil {
		auth = method.Auth
	}

	if auth != nil && auth.Required && auth.Capability != "" {
		requiredCapability = auth.Capability

		// Validate JWT token
		validator := d.validators[serviceName]
		if validator == nil {
			p := problem.NewProblem(http.StatusInternalServerError, "about:blank#server-error",
				"Internal Server Error", fmt.Sprintf("no validator for service '%s'", serviceName))
			_ = p.Write(w)
			return
		}

		claims, err := validator.ValidateToken(r.Header.Get("Authorization"))
		if err != nil {
			p := problem.NewProblem(http.StatusForbidden, "about:blank#forbidden",
				"Forbidden", fmt.Sprintf("authentication failed: %v", err))
			_ = p.Write(w)
			return
		}

		// Check permission
		if !validator.HasPermission(claims, requiredCapability) {
			p := problem.NewProblem(http.StatusForbidden, "about:blank#forbidden",
				"Forbidden", fmt.Sprintf("permission '%s' required", requiredCapability))
			_ = p.Write(w)
			return
		}
	}

	// Build upstream URL
	upstreamURL, err := url.Parse(adapter.Spec.Upstream.URL)
	if err != nil {
		d.writeError(w, problem.NewProblem(http.StatusInternalServerError, "about:blank#server-error",
			"Internal Server Error", fmt.Sprintf("invalid upstream URL: %v", err)))
		return
	}

	// Create reverse proxy with director that rewrites the path
	proxy := httputil.NewSingleHostReverseProxy(upstreamURL)
	proxy.Director = func(req *http.Request) {
		req.URL.Scheme = upstreamURL.Scheme
		req.URL.Host = upstreamURL.Host
		req.URL.Path = method.UpstreamPath
		req.RequestURI = ""
		req.Host = upstreamURL.Host
	}

	// Set timeout
	timeout := adapter.Spec.Upstream.TimeoutSeconds
	if timeout <= 0 {
		timeout = 30
	}
	proxy.Transport = &http.Transport{
		DialContext:         (&net.Dialer{Timeout: time.Duration(timeout) * time.Second}).DialContext,
		TLSHandshakeTimeout: time.Duration(timeout) * time.Second,
	}

	// Forward the request
	proxy.ServeHTTP(w, r)
}



func (d *Dispatcher) writeError(w http.ResponseWriter, p *problem.Problem) {
	_ = p.Write(w)
}