package web

import (
	"html/template"
	"net/http"
	"strings"
	"time"

	"gitea.mynodes.xyz/ilker/llmgw/internal/clientip"
)

// LandingData is what the landing page shows. It is deliberately almost
// nothing: this page is served without a key, to anyone who can reach the
// address.
type LandingData struct {
	BaseURL     string
	AuthEnabled bool
	SignupOpen  bool
	Contact     string
	ContactHref string
	// ContactHTML is the contact as the page shows it, a link when it is
	// one, for the sentence that names it to place.
	ContactHTML template.HTML
	Notice      string
	Version     string
	Now         string
}

// Landing serves the page at "/" on the client-facing port.
//
// Without it that path is a 404, which is what someone sees when they paste the
// address into a browser — an endpoint that looks broken rather than one that
// tells them how to use it.
//
// It lists no models and no cluster state. Everything that says what is here
// stays behind the key, including /v1/models.
func Landing(version string, authEnabled, signupOpen bool, contact, notice string) http.HandlerFunc {
	text, href := contactLink(contact)
	return func(w http.ResponseWriter, r *http.Request) {
		// Only the root: a catch-all would turn every mistyped path into this
		// page, hiding genuine 404s from anyone debugging a client.
		if r.URL.Path != "/" {
			http.NotFound(w, r)
			return
		}
		render(w, r, "landing", LandingData{
			BaseURL:     baseURL(r),
			AuthEnabled: authEnabled,
			SignupOpen:  signupOpen,
			Contact:     text,
			ContactHref: href,
			ContactHTML: contactMarkup(text, href),
			Notice:      notice,
			Version:     version,
			Now:         time.Now().UTC().Format(time.RFC3339),
		})
	}
}

// baseURL reconstructs the address the client actually used.
//
// Behind a reverse proxy the scheme and host this process sees are the internal
// ones, so the forwarded headers are what make the copy-pasteable example on
// the page correct. They are attacker-controlled when nothing sets them, which
// is why they are only reflected into a displayed URL and never used for a
// decision.
func baseURL(r *http.Request) string {
	// What a trusted proxy says it was asked for, else what this server was:
	// the address goes into scripts clients pipe to a shell, so it is not
	// taken from whoever sends a header.
	scheme, host := clientip.Proto(r), clientip.Host(r)
	if host == "" {
		host = "localhost:8080"
	}
	return scheme + "://" + host
}

// firstValue takes the first entry of a comma-separated forwarded header: a
// chain of proxies appends rather than replaces.
func firstValue(v string) string {
	if i := strings.IndexByte(v, ','); i >= 0 {
		v = v[:i]
	}
	return strings.TrimSpace(v)
}