package main

import (
	"archive/zip"
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"sort"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"fission-console/ui"

	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
	"k8s.io/apimachinery/pkg/runtime/schema"
	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/rest"
	"k8s.io/client-go/tools/clientcmd"
)

var (
	environmentGVR = schema.GroupVersionResource{Group: "fission.io", Version: "v1", Resource: "environments"}
	packageGVR     = schema.GroupVersionResource{Group: "fission.io", Version: "v1", Resource: "packages"}
	functionGVR    = schema.GroupVersionResource{Group: "fission.io", Version: "v1", Resource: "functions"}
	httpTrigGVR    = schema.GroupVersionResource{Group: "fission.io", Version: "v1", Resource: "httptriggers"}
	timeTrigGVR    = schema.GroupVersionResource{Group: "fission.io", Version: "v1", Resource: "timetriggers"}
)

const defaultSATokenPath = "/var/run/secrets/kubernetes.io/serviceaccount/token"

type server struct {
	dyn         dynamic.Interface
	ns          string
	routerURL   string
	http        *http.Client
	saTokenPath string

	authUser string
	authPass string

	tokenMu    sync.Mutex
	cachedJWT  string
	tokenExpAt time.Time
}

type createFunctionRequest struct {
	Name        string   `json:"name"`
	Environment string   `json:"environment"`
	Code        string   `json:"code"`
	Entrypoint  string   `json:"entrypoint"`
	Route       string   `json:"route"`
	Methods     []string `json:"methods"`
}

type updateCodeRequest struct {
	Code string `json:"code"`
}

func main() {
	kubeconfig := strings.TrimSpace(os.Getenv("KUBECONFIG"))
	namespace := envDefault("FISSION_NAMESPACE", "default")
	routerURL := strings.TrimRight(envDefault("FISSION_ROUTER_URL", "http://router.fission.svc.cluster.local"), "/")
	port := envDefault("PORT", "8090")

	cfg, err := buildConfig(kubeconfig)
	if err != nil {
		log.Fatalf("build kube config: %v", err)
	}

	dyn, err := dynamic.NewForConfig(cfg)
	if err != nil {
		log.Fatalf("create dynamic client: %v", err)
	}

	authUser := envDefault("FISSION_AUTH_USERNAME", "")
	authPass := envDefault("FISSION_AUTH_PASSWORD", "")
	saTokenPath := envDefault("SA_TOKEN_PATH", defaultSATokenPath)

	s := &server{
		dyn:         dyn,
		ns:          namespace,
		routerURL:   routerURL,
		http:        &http.Client{Timeout: 30 * time.Second},
		saTokenPath: saTokenPath,
		authUser:    authUser,
		authPass:    authPass,
	}

	mux := http.NewServeMux()
	mux.HandleFunc("/health", func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		_, _ = w.Write([]byte("ok\n"))
	})
	mux.HandleFunc("/console/health", func(w http.ResponseWriter, _ *http.Request) {
		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
		_, _ = w.Write([]byte("ok\n"))
	})

	uiHandler := http.StripPrefix("/console", ui.Handler())
	mux.Handle("/console", uiHandler)
	mux.Handle("/console/", uiHandler)

	mux.HandleFunc("/api/environments", s.handleList(environmentGVR))
	mux.HandleFunc("/api/packages", s.handleList(packageGVR))
	mux.HandleFunc("/api/functions", s.handleFunctionsRoot)
	mux.HandleFunc("/api/functions/", s.handleFunctionsAction)
	mux.HandleFunc("/api/httptriggers", s.handleList(httpTrigGVR))
	mux.HandleFunc("/api/timetriggers", s.handleList(timeTrigGVR))

	mux.HandleFunc("/console/api/environments", s.handleList(environmentGVR))
	mux.HandleFunc("/console/api/packages", s.handleList(packageGVR))
	mux.HandleFunc("/console/api/functions", s.handleFunctionsRoot)
	mux.HandleFunc("/console/api/functions/", s.handleFunctionsAction)
	mux.HandleFunc("/console/api/httptriggers", s.handleList(httpTrigGVR))
	mux.HandleFunc("/console/api/timetriggers", s.handleList(timeTrigGVR))

	httpServer := &http.Server{
		Addr:              ":" + port,
		Handler:           withCORS(logRequests(mux)),
		ReadHeaderTimeout: 10 * time.Second,
	}

	log.Printf("fission-console listening on :%s (namespace=%s)", port, namespace)
	log.Fatal(httpServer.ListenAndServe())
}

func (s *server) handleFunctionsRoot(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodGet:
		s.handleList(functionGVR)(w, r)
	case http.MethodPost:
		s.handleCreateFunction(w, r)
	default:
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}

func (s *server) handleFunctionsAction(w http.ResponseWriter, r *http.Request) {
	path := strings.TrimPrefix(r.URL.Path, "/api/functions/")
	if path == r.URL.Path {
		path = strings.TrimPrefix(r.URL.Path, "/console/api/functions/")
	}
	path = strings.Trim(path, "/")
	if path == "" {
		http.NotFound(w, r)
		return
	}

	parts := strings.Split(path, "/")
	name := strings.TrimSpace(parts[0])
	if name == "" {
		writeJSONError(w, http.StatusBadRequest, "function name is required")
		return
	}

	if len(parts) == 1 {
		switch r.Method {
		case http.MethodGet:
			s.handleGetFunction(w, r, name)
		case http.MethodDelete:
			s.handleDeleteFunction(w, r, name)
		default:
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		}
		return
	}

	if len(parts) == 2 && parts[1] == "code" && r.Method == http.MethodPut {
		s.handleUpdateFunctionCode(w, r, name)
		return
	}

	if len(parts) == 2 && parts[1] == "invoke" && r.Method == http.MethodPost {
		s.handleInvokeFunction(w, r, name)
		return
	}

	http.NotFound(w, r)
}

func (s *server) handleCreateFunction(w http.ResponseWriter, r *http.Request) {
	var req createFunctionRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSONError(w, http.StatusBadRequest, fmt.Sprintf("decode request: %v", err))
		return
	}

	req.Name = strings.TrimSpace(req.Name)
	req.Environment = strings.TrimSpace(req.Environment)
	req.Code = strings.TrimSpace(req.Code)
	req.Entrypoint = strings.TrimSpace(req.Entrypoint)
	req.Route = strings.TrimSpace(req.Route)

	if req.Name == "" || req.Environment == "" || req.Code == "" {
		writeJSONError(w, http.StatusBadRequest, "name, environment and code are required")
		return
	}
	if req.Entrypoint == "" {
		req.Entrypoint = "main.main"
	}
	if req.Route == "" {
		req.Route = "/" + req.Name
	}
	if !strings.HasPrefix(req.Route, "/") {
		req.Route = "/" + req.Route
	}
	req.Methods = normalizeMethods(req.Methods)

	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()

	if _, err := s.dyn.Resource(environmentGVR).Namespace(s.ns).Get(ctx, req.Environment, metav1.GetOptions{}); err != nil {
		writeJSONError(w, http.StatusBadRequest, fmt.Sprintf("environment %q not found: %v", req.Environment, err))
		return
	}

	pkgName := req.Name + "-pkg"
	triggerName := req.Name + "-route"
	methodValues := make([]any, 0, len(req.Methods))
	for _, method := range req.Methods {
		methodValues = append(methodValues, method)
	}

	literal := base64.StdEncoding.EncodeToString([]byte(req.Code))
	pkg := &unstructured.Unstructured{Object: map[string]any{
		"apiVersion": "fission.io/v1",
		"kind":       "Package",
		"metadata": map[string]any{
			"name":      pkgName,
			"namespace": s.ns,
		},
		"spec": map[string]any{
			"deployment": map[string]any{
				"type":    "literal",
				"literal": literal,
			},
			"environment": map[string]any{
				"name":      req.Environment,
				"namespace": s.ns,
			},
			"source": map[string]any{},
		},
	}}

	if _, err := s.dyn.Resource(packageGVR).Namespace(s.ns).Create(ctx, pkg, metav1.CreateOptions{}); err != nil {
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("create package: %v", err))
		return
	}

	fn := &unstructured.Unstructured{Object: map[string]any{
		"apiVersion": "fission.io/v1",
		"kind":       "Function",
		"metadata": map[string]any{
			"name":      req.Name,
			"namespace": s.ns,
		},
		"spec": map[string]any{
			"environment": map[string]any{
				"name":      req.Environment,
				"namespace": s.ns,
			},
			"InvokeStrategy": map[string]any{
				"ExecutionStrategy": map[string]any{"ExecutorType": "poolmgr"},
				"StrategyType":      "execution",
			},
			"package": map[string]any{
				"packageref":   map[string]any{"name": pkgName, "namespace": s.ns},
				"functionName": req.Entrypoint,
			},
		},
	}}

	if _, err := s.dyn.Resource(functionGVR).Namespace(s.ns).Create(ctx, fn, metav1.CreateOptions{}); err != nil {
		_ = s.dyn.Resource(packageGVR).Namespace(s.ns).Delete(ctx, pkgName, metav1.DeleteOptions{})
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("create function: %v", err))
		return
	}

	httpTrigger := &unstructured.Unstructured{Object: map[string]any{
		"apiVersion": "fission.io/v1",
		"kind":       "HTTPTrigger",
		"metadata": map[string]any{
			"name":      triggerName,
			"namespace": s.ns,
		},
		"spec": map[string]any{
			"relativeurl":   req.Route,
			"methods":       methodValues,
			"createingress": true,
			"functionref": map[string]any{
				"type": "name",
				"name": req.Name,
			},
		},
	}}

	if _, err := s.dyn.Resource(httpTrigGVR).Namespace(s.ns).Create(ctx, httpTrigger, metav1.CreateOptions{}); err != nil {
		_ = s.dyn.Resource(functionGVR).Namespace(s.ns).Delete(ctx, req.Name, metav1.DeleteOptions{})
		_ = s.dyn.Resource(packageGVR).Namespace(s.ns).Delete(ctx, pkgName, metav1.DeleteOptions{})
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("create httptrigger: %v", err))
		return
	}

	writeAnyJSON(w, http.StatusCreated, map[string]any{
		"name":        req.Name,
		"package":     pkgName,
		"httptrigger": triggerName,
		"route":       req.Route,
	})
}

func (s *server) handleGetFunction(w http.ResponseWriter, r *http.Request, name string) {
	ctx, cancel := context.WithTimeout(r.Context(), 10*time.Second)
	defer cancel()

	fn, err := s.dyn.Resource(functionGVR).Namespace(s.ns).Get(ctx, name, metav1.GetOptions{})
	if err != nil {
		status := http.StatusBadGateway
		if apierrors.IsNotFound(err) {
			status = http.StatusNotFound
		}
		writeJSONError(w, status, fmt.Sprintf("get function %q: %v", name, err))
		return
	}

	packageName, _, _ := unstructured.NestedString(fn.Object, "spec", "package", "packageref", "name")
	environment, _, _ := unstructured.NestedString(fn.Object, "spec", "environment", "name")
	entrypoint, _, _ := unstructured.NestedString(fn.Object, "spec", "package", "functionName")

	code := ""
	if packageName != "" {
		pkg, pkgErr := s.dyn.Resource(packageGVR).Namespace(s.ns).Get(ctx, packageName, metav1.GetOptions{})
		if pkgErr == nil {
			literal, _, _ := unstructured.NestedString(pkg.Object, "spec", "deployment", "literal")
			if literal != "" {
				if decodedCode, decErr := decodeLiteralToSource(literal); decErr == nil {
					code = decodedCode
				}
			}
		}
	}

	route := ""
	methods := []string{}
	triggers, trigErr := s.dyn.Resource(httpTrigGVR).Namespace(s.ns).List(ctx, metav1.ListOptions{})
	if trigErr == nil {
		for _, trig := range triggers.Items {
			refName, _, _ := unstructured.NestedString(trig.Object, "spec", "functionref", "name")
			if refName != name {
				continue
			}
			route, _, _ = unstructured.NestedString(trig.Object, "spec", "relativeurl")
			methods, _, _ = unstructured.NestedStringSlice(trig.Object, "spec", "methods")
			break
		}
	}

	writeAnyJSON(w, http.StatusOK, map[string]any{
		"name":        name,
		"namespace":   s.ns,
		"environment": environment,
		"package":     packageName,
		"entrypoint":  entrypoint,
		"code":        code,
		"route":       route,
		"methods":     methods,
		"raw":         fn.Object,
	})
}

func (s *server) handleUpdateFunctionCode(w http.ResponseWriter, r *http.Request, name string) {
	var req updateCodeRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSONError(w, http.StatusBadRequest, fmt.Sprintf("decode request: %v", err))
		return
	}
	req.Code = strings.TrimSpace(req.Code)
	if req.Code == "" {
		writeJSONError(w, http.StatusBadRequest, "code is required")
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()

	fn, err := s.dyn.Resource(functionGVR).Namespace(s.ns).Get(ctx, name, metav1.GetOptions{})
	if err != nil {
		status := http.StatusBadGateway
		if apierrors.IsNotFound(err) {
			status = http.StatusNotFound
		}
		writeJSONError(w, status, fmt.Sprintf("get function %q: %v", name, err))
		return
	}

	pkgName, _, _ := unstructured.NestedString(fn.Object, "spec", "package", "packageref", "name")
	if pkgName == "" {
		writeJSONError(w, http.StatusBadGateway, "function has no package reference")
		return
	}

	pkg, err := s.dyn.Resource(packageGVR).Namespace(s.ns).Get(ctx, pkgName, metav1.GetOptions{})
	if err != nil {
		status := http.StatusBadGateway
		if apierrors.IsNotFound(err) {
			status = http.StatusNotFound
		}
		writeJSONError(w, status, fmt.Sprintf("get package %q: %v", pkgName, err))
		return
	}

	literal := base64.StdEncoding.EncodeToString([]byte(req.Code))
	if err := unstructured.SetNestedField(pkg.Object, literal, "spec", "deployment", "literal"); err != nil {
		writeJSONError(w, http.StatusInternalServerError, fmt.Sprintf("set package literal: %v", err))
		return
	}

	if _, err := s.dyn.Resource(packageGVR).Namespace(s.ns).Update(ctx, pkg, metav1.UpdateOptions{}); err != nil {
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("update package %q: %v", pkgName, err))
		return
	}

	updatedPkg, err := s.dyn.Resource(packageGVR).Namespace(s.ns).Get(ctx, pkgName, metav1.GetOptions{})
	if err != nil {
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("get updated package %q: %v", pkgName, err))
		return
	}

	if err := unstructured.SetNestedField(fn.Object, updatedPkg.GetResourceVersion(), "spec", "package", "packageref", "resourceversion"); err != nil {
		writeJSONError(w, http.StatusInternalServerError, fmt.Sprintf("set function package resourceversion: %v", err))
		return
	}

	if _, err := s.dyn.Resource(functionGVR).Namespace(s.ns).Update(ctx, fn, metav1.UpdateOptions{}); err != nil {
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("update function %q package ref: %v", name, err))
		return
	}

	writeAnyJSON(w, http.StatusOK, map[string]any{"updated": true, "package": pkgName, "package_resourceversion": updatedPkg.GetResourceVersion()})
}

func (s *server) handleInvokeFunction(w http.ResponseWriter, r *http.Request, name string) {
	bodyBytes, err := io.ReadAll(r.Body)
	if err != nil {
		writeJSONError(w, http.StatusBadRequest, fmt.Sprintf("read request body: %v", err))
		return
	}
	if len(bytes.TrimSpace(bodyBytes)) == 0 {
		bodyBytes = []byte("{}")
	}

	ctx, cancel := context.WithTimeout(r.Context(), 25*time.Second)
	defer cancel()

	invokeURL := fmt.Sprintf("%s/fission-function/v2/functions/%s", s.routerURL, name)
	invokeMethod := http.MethodPost
	triggers, err := s.dyn.Resource(httpTrigGVR).Namespace(s.ns).List(ctx, metav1.ListOptions{})
	if err == nil {
		for _, trig := range triggers.Items {
			refName, _, _ := unstructured.NestedString(trig.Object, "spec", "functionref", "name")
			if refName != name {
				continue
			}
			route, _, _ := unstructured.NestedString(trig.Object, "spec", "relativeurl")
			methods, _, _ := unstructured.NestedStringSlice(trig.Object, "spec", "methods")
			hasPost := false
			hasGet := false
			for _, method := range methods {
				m := strings.ToUpper(strings.TrimSpace(method))
				if m == http.MethodPost {
					hasPost = true
				}
				if m == http.MethodGet {
					hasGet = true
				}
			}
			if route != "" {
				if !strings.HasPrefix(route, "/") {
					route = "/" + route
				}
				invokeURL = s.routerURL + route
				if !hasPost && hasGet {
					invokeMethod = http.MethodGet
				}
				break
			}
		}
	}

	start := time.Now()
	var invokeBody io.Reader
	if invokeMethod == http.MethodPost {
		invokeBody = bytes.NewReader(bodyBytes)
	}
	req, err := http.NewRequestWithContext(ctx, invokeMethod, invokeURL, invokeBody)
	if err != nil {
		writeJSONError(w, http.StatusInternalServerError, fmt.Sprintf("build invoke request: %v", err))
		return
	}
	if invokeMethod == http.MethodPost {
		req.Header.Set("Content-Type", "application/json")
	}
	if token := s.getRouterToken(); token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}

	resp, err := s.http.Do(req)
	if err != nil {
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("invoke %q: %v", name, err))
		return
	}
	defer resp.Body.Close()

	respBody, _ := io.ReadAll(resp.Body)
	writeAnyJSON(w, http.StatusOK, map[string]any{
		"status":       resp.StatusCode,
		"latency_ms":   time.Since(start).Milliseconds(),
		"invoke_url":   invokeURL,
		"response_raw": string(respBody),
	})
}

func (s *server) readSAToken() string {
	if s.saTokenPath == "" {
		return ""
	}
	data, err := os.ReadFile(s.saTokenPath)
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(data))
}

func (s *server) getRouterToken() string {
	if s.authUser == "" || s.authPass == "" {
		return s.readSAToken()
	}

	s.tokenMu.Lock()
	defer s.tokenMu.Unlock()

	if s.cachedJWT != "" && time.Now().Before(s.tokenExpAt) {
		return s.cachedJWT
	}

	loginURL := s.routerURL + "/auth/login"
	body, _ := json.Marshal(map[string]string{"username": s.authUser, "password": s.authPass})
	resp, err := s.http.Post(loginURL, "application/json", bytes.NewReader(body))
	if err != nil {
		log.Printf("router login failed: %v", err)
		return s.readSAToken()
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
		respBody, _ := io.ReadAll(resp.Body)
		log.Printf("router login %d: %s", resp.StatusCode, string(respBody))
		return s.readSAToken()
	}

	var result struct {
		AccessToken string `json:"accesstoken"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil || result.AccessToken == "" {
		log.Printf("router login decode error: %v", err)
		return s.readSAToken()
	}

	s.cachedJWT = result.AccessToken
	s.tokenExpAt = time.Now().Add(100 * time.Second)
	log.Printf("router JWT obtained, expires in 100s")
	return s.cachedJWT
}

func (s *server) handleDeleteFunction(w http.ResponseWriter, r *http.Request, name string) {
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()

	var pkgName string
	fn, err := s.dyn.Resource(functionGVR).Namespace(s.ns).Get(ctx, name, metav1.GetOptions{})
	if err == nil {
		pkgName, _, _ = unstructured.NestedString(fn.Object, "spec", "package", "packageref", "name")
	}

	triggers, err := s.dyn.Resource(httpTrigGVR).Namespace(s.ns).List(ctx, metav1.ListOptions{})
	if err == nil {
		for _, trig := range triggers.Items {
			refName, _, _ := unstructured.NestedString(trig.Object, "spec", "functionref", "name")
			if refName == name {
				_ = s.dyn.Resource(httpTrigGVR).Namespace(s.ns).Delete(ctx, trig.GetName(), metav1.DeleteOptions{})
			}
		}
	}

	if err := s.dyn.Resource(functionGVR).Namespace(s.ns).Delete(ctx, name, metav1.DeleteOptions{}); err != nil && !apierrors.IsNotFound(err) {
		writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("delete function %q: %v", name, err))
		return
	}

	if pkgName != "" {
		if err := s.dyn.Resource(packageGVR).Namespace(s.ns).Delete(ctx, pkgName, metav1.DeleteOptions{}); err != nil && !apierrors.IsNotFound(err) {
			writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("delete package %q: %v", pkgName, err))
			return
		}
	}

	writeAnyJSON(w, http.StatusOK, map[string]any{"deleted": true, "name": name, "package": pkgName})
}

func buildConfig(kubeconfig string) (*rest.Config, error) {
	if kubeconfig != "" {
		cfg, err := clientcmd.BuildConfigFromFlags("", kubeconfig)
		if err == nil {
			return cfg, nil
		}
		return nil, fmt.Errorf("kubeconfig %s: %w", kubeconfig, err)
	}

	cfg, err := rest.InClusterConfig()
	if err == nil {
		return cfg, nil
	}

	loadingRules := &clientcmd.ClientConfigLoadingRules{}
	clientCfg := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(loadingRules, &clientcmd.ConfigOverrides{})
	return clientCfg.ClientConfig()
}

func (s *server) handleList(gvr schema.GroupVersionResource) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}

		ctx, cancel := context.WithTimeout(r.Context(), 10*time.Second)
		defer cancel()

		list, err := s.dyn.Resource(gvr).Namespace(s.ns).List(ctx, metav1.ListOptions{})
		if err != nil {
			writeJSONError(w, http.StatusBadGateway, fmt.Sprintf("list %s: %v", gvr.Resource, err))
			return
		}

		writeJSON(w, http.StatusOK, list.Items)
	}
}

func writeJSON(w http.ResponseWriter, status int, data []unstructured.Unstructured) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(data)
}

func writeAnyJSON(w http.ResponseWriter, status int, data any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(data)
}

func writeJSONError(w http.ResponseWriter, status int, msg string) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(map[string]any{"error": msg})
}

func logRequests(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s", r.Method, r.URL.Path)
		next.ServeHTTP(w, r)
	})
}

func withCORS(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET,POST,PUT,PATCH,DELETE,OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

func envDefault(key, fallback string) string {
	if v := strings.TrimSpace(os.Getenv(key)); v != "" {
		return v
	}
	return fallback
}

func normalizeMethods(in []string) []string {
	if len(in) == 0 {
		return []string{"GET"}
	}
	out := make([]string, 0, len(in))
	seen := map[string]bool{}
	for _, method := range in {
		m := strings.ToUpper(strings.TrimSpace(method))
		if m == "" || seen[m] {
			continue
		}
		seen[m] = true
		out = append(out, m)
	}
	if len(out) == 0 {
		return []string{"GET"}
	}
	return out
}

func decodeLiteralToSource(literal string) (string, error) {
	decoded, err := base64.StdEncoding.DecodeString(literal)
	if err != nil {
		return "", err
	}

	if utf8.Valid(decoded) {
		return string(decoded), nil
	}

	if len(decoded) >= 4 && bytes.Equal(decoded[:4], []byte{'P', 'K', 3, 4}) {
		if src, zipErr := decodeZipSource(decoded); zipErr == nil {
			return src, nil
		}
	}

	return string(decoded), nil
}

func decodeZipSource(zipBytes []byte) (string, error) {
	reader, err := zip.NewReader(bytes.NewReader(zipBytes), int64(len(zipBytes)))
	if err != nil {
		return "", err
	}

	preferred := []string{"main.py", "main.js", "main.go"}
	for _, name := range preferred {
		for _, file := range reader.File {
			if strings.EqualFold(file.Name, name) {
				content, readErr := readZipFile(file)
				if readErr != nil {
					return "", readErr
				}
				if utf8.Valid(content) {
					return string(content), nil
				}
			}
		}
	}

	files := make([]*zip.File, 0, len(reader.File))
	for _, file := range reader.File {
		if file.FileInfo().IsDir() {
			continue
		}
		files = append(files, file)
	}
	sort.Slice(files, func(i, j int) bool {
		return files[i].Name < files[j].Name
	})

	for _, file := range files {
		content, readErr := readZipFile(file)
		if readErr != nil {
			continue
		}
		if utf8.Valid(content) {
			return string(content), nil
		}
	}

	return "", fmt.Errorf("zip archive does not contain utf-8 source files")
}

func readZipFile(file *zip.File) ([]byte, error) {
	rc, err := file.Open()
	if err != nil {
		return nil, err
	}
	defer rc.Close()

	return io.ReadAll(rc)
}