package http

import (
	"fmt"
	"log/slog"
	"net/http"

	"tug/internal/platform/config"
)

const (
	CSP           = "default-src 'none'; style-src 'self'; img-src 'self'; form-action 'self'; frame-ancestors 'none'; base-uri 'none'"
	CSPWithScript = "default-src 'none'; style-src 'self'; img-src 'self'; script-src 'self'; form-action 'self'; frame-ancestors 'none'; base-uri 'none'"
)

func SecurityHeaders(next http.Handler, enhancementJS bool) http.Handler {
	csp := CSP
	if enhancementJS {
		csp = CSPWithScript
	}
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		h := w.Header()
		h.Set("Content-Security-Policy", csp)
		h.Set("Referrer-Policy", "no-referrer")
		h.Set("X-Content-Type-Options", "nosniff")
		next.ServeHTTP(w, r)
	})
}

func Recover(next http.Handler, page ErrorPage) http.Handler {
	if page == nil {
		panic(errNilPage)
	}
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		tw := &startTracker{ResponseWriter: w}
		defer func() {
			v := recover()
			if v == nil {
				return
			}
			if v == http.ErrAbortHandler || tw.started {
				panic(http.ErrAbortHandler)
			}
			slog.Error("handler panic before the response started", "panic", fmt.Sprint(v))
			page(w, r, http.StatusInternalServerError)
		}()
		next.ServeHTTP(tw, r)
	})
}

type startTracker struct {
	http.ResponseWriter
	started bool
}

func (t *startTracker) WriteHeader(code int) {
	t.started = true
	t.ResponseWriter.WriteHeader(code)
}

func (t *startTracker) Write(b []byte) (int, error) {
	t.started = true
	return t.ResponseWriter.Write(b)
}

func (t *startTracker) Flush() {
	t.started = true
	if f, ok := t.ResponseWriter.(http.Flusher); ok {
		f.Flush()
	}
}

func (t *startTracker) Unwrap() http.ResponseWriter {
	t.started = true
	return t.ResponseWriter
}

func Routed(srv config.Server, apps []config.App, h Handlers, page ErrorPage, enhancementJS bool, opts ...RouterOption) http.Handler {
	if page == nil {
		panic(errNilPage)
	}
	return SecurityHeaders(Recover(forwardedClient(NewRouter(srv, apps, h, page, opts...)), page), enhancementJS)
}