package internals

import (
	"embed"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/creack/pty"
	"github.com/gorilla/websocket"
)

//go:embed web/shell.html
var shellPageHTML string

//go:embed web/login.html
var loginPageHTML string

//go:embed web/favicon.svg
var faviconSVG string

//go:embed web/*.css web/*.js
var staticAssets embed.FS

var upgrader = websocket.Upgrader{CheckOrigin: func(r *http.Request) bool { return true }}

// handleFavicon serves a terminal-themed SVG favicon.
func handleFavicon(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "image/svg+xml")
	w.Header().Set("Cache-Control", "public, max-age=86400")
	w.Write([]byte(faviconSVG))
}

// handleStaticCSS serves the embedded app.css stylesheet.
func handleStaticCSS(w http.ResponseWriter, r *http.Request) {
	data, err := staticAssets.ReadFile("web/app.css")
	if err != nil {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "text/css; charset=utf-8")
	w.Header().Set("Cache-Control", "public, max-age=3600")
	w.Write(data)
}

// handleStaticJS serves the embedded app.js script.
func handleStaticJS(w http.ResponseWriter, r *http.Request) {
	data, err := staticAssets.ReadFile("web/app.js")
	if err != nil {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "application/javascript; charset=utf-8")
	w.Header().Set("Cache-Control", "public, max-age=3600")
	w.Write(data)
}

// handleLogin serves the standalone login page (GET) or redirects authed users.
func handleLogin(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/login" {
		http.NotFound(w, r)
		return
	}
	if isAuthed(r) {
		http.Redirect(w, r, "/", http.StatusFound)
		return
	}
	next := r.URL.Query().Get("next")
	if !isValidNext(next) {
		next = "/"
	}
	tok := setCSRFCookie(w)
	html := strings.NewReplacer(
		"[[CSRF_TOKEN]]", tok,
		"[[NEXT]]",       next,
	).Replace(loginPageHTML)
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	w.Write([]byte(html)) //nolint:errcheck
}

// isValidNext rejects open-redirect targets; only "/" and "/s/<hex>" allowed.
func isValidNext(next string) bool {
	if next == "" || next == "/" {
		return true
	}
	if strings.HasPrefix(next, "/s/") {
		return validID(strings.TrimPrefix(next, "/s/"))
	}
	return false
}

// handleIndex: creates a fresh workspace and redirects to its stable URL.
// Unauthenticated requests are sent to the login page first.
func handleIndex(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	if !isAuthed(r) {
		http.Redirect(w, r, "/login", http.StatusFound)
		return
	}
	http.Redirect(w, r, "/s/"+randHex(16), http.StatusFound)
}

// handleShell: serves the terminal page for a workspace ID.
// Unauthenticated requests are redirected to /login?next=...
func handleShell(w http.ResponseWriter, r *http.Request) {
	id := strings.TrimPrefix(r.URL.Path, "/s/")
	if !validID(id) {
		http.NotFound(w, r)
		return
	}
	if !isAuthed(r) {
		http.Redirect(w, r, "/login?next=/s/"+id, http.StatusFound)
		return
	}
	serveTerminalPage(w, id, true)
}

func serveTerminalPage(w http.ResponseWriter, workspaceID string, authed bool) {
	authedStr := "false"
	if authed {
		authedStr = "true"
	}
	html := strings.NewReplacer(
		"[[WORKSPACE_ID]]", workspaceID,
		"[[AUTHED]]",       authedStr,
	).Replace(shellPageHTML)
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.Write([]byte(html))
}

func handleAuth(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	if r.Method != http.MethodPost {
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte(`{"error":"POST only"}`)) //nolint:errcheck
		return
	}
	if err := r.ParseForm(); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(`{"error":"bad form"}`)) //nolint:errcheck
		return
	}

	// CSRF validation (skipped in -nopw mode which never shows the login page)
	if !nopwMode && !checkCSRF(r) {
		logAuthAttempt(r, "", false, "csrf_invalid")
		w.WriteHeader(http.StatusForbidden)
		w.Write([]byte(`{"error":"invalid request"}`)) //nolint:errcheck
		return
	}

	username := strings.TrimSpace(r.FormValue("username"))
	password := r.FormValue("password")

	// Input bounds — reject obviously bad values before touching the hasher
	if len(username) == 0 || len(username) > 64 || len(password) == 0 || len(password) > 1024 {
		time.Sleep(500 * time.Millisecond)
		logAuthAttempt(r, username, false, "invalid_input")
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(`{"error":"invalid input"}`)) //nolint:errcheck
		return
	}

	if checkCreds(username, password) {
		http.SetCookie(w, &http.Cookie{
			Name:     authCookieName,
			Value:    makeAuthToken(),
			Path:     "/",
			HttpOnly: true,
			Secure:   true,
			SameSite: http.SameSiteLaxMode,
			MaxAge:   int(authTokenTTL.Seconds()),
		})
		logAuthAttempt(r, username, true, "login_success")
		w.Write([]byte(`{"ok":true}`)) //nolint:errcheck
	} else {
		time.Sleep(500 * time.Millisecond) // blunt brute-force deterrent
		logAuthAttempt(r, username, false, "invalid_credentials")
		w.WriteHeader(http.StatusUnauthorized)
		w.Write([]byte(`{"error":"Invalid username or password"}`)) //nolint:errcheck
	}
}

func handleWS(w http.ResponseWriter, r *http.Request) {
	if !isAuthed(r) {
		http.Error(w, "unauthorized", http.StatusUnauthorized)
		return
	}
	id := strings.TrimPrefix(r.URL.Path, "/ws/")
	if !validID(id) {
		http.Error(w, "invalid session id", http.StatusBadRequest)
		return
	}
	s := getOrCreate(id)
	if s == nil {
		http.Error(w, "failed to start shell", http.StatusInternalServerError)
		return
	}
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		return
	}
	cl := &client{conn: conn}

	s.mu.Lock()
	s.clients[cl] = struct{}{}
	s.lastSeen = time.Now()
	isNew := len(s.buf) == 0
	replay := make([]byte, len(s.buf))
	copy(replay, s.buf)
	s.mu.Unlock()

	if len(replay) > 0 {
		cl.write(websocket.BinaryMessage, replay)
	}
	cl.write(websocket.TextMessage, []byte(
		fmt.Sprintf(`{"type":"session","id":"%s","new":%v}`, id[:8], isNew),
	))

	defer func() {
		s.mu.Lock()
		delete(s.clients, cl)
		s.mu.Unlock()
		conn.Close()
	}()

	for {
		mt, data, err := conn.ReadMessage()
		if err != nil {
			break
		}
		s.mu.Lock()
		s.lastSeen = time.Now()
		s.mu.Unlock()

		if mt == websocket.TextMessage {
			var msg struct {
				Type string `json:"type"`
				Cols int    `json:"cols"`
				Rows int    `json:"rows"`
			}
			if json.Unmarshal(data, &msg) == nil && msg.Type == "resize" {
				pty.Setsize(s.ptty, &pty.Winsize{Cols: uint16(msg.Cols), Rows: uint16(msg.Rows)})
				continue
			}
		}
		s.ptty.Write(data) //nolint:errcheck
	}
}

func handleUpload(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	if !isAuthed(r) {
		w.WriteHeader(http.StatusUnauthorized)
		w.Write([]byte(`{"error":"unauthorized"}`))
		return
	}
	if r.Method != http.MethodPost {
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte(`{"error":"POST only"}`))
		return
	}
	r.Body = http.MaxBytesReader(w, r.Body, maxUploadSize)
	if err := r.ParseMultipartForm(32 << 20); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		fmt.Fprintf(w, `{"error":"parse error: %s"}`, err.Error())
		return
	}
	id := r.FormValue("sid")
	if !validID(id) {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(`{"error":"missing or invalid session id"}`))
		return
	}
	s := sessionByID(id)
	if s == nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(`{"error":"session not found — reopen the terminal"}`))
		return
	}
	file, header, err := r.FormFile("file")
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(`{"error":"missing file field"}`))
		return
	}
	defer file.Close()

	tmp, err := os.CreateTemp("", "gws-upload-*")
	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(`{"error":"temp file error"}`))
		return
	}
	tmpName := tmp.Name()
	if _, err := io.Copy(tmp, file); err != nil {
		tmp.Close()
		os.Remove(tmpName)
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(`{"error":"write error"}`))
		return
	}
	tmp.Close()

	destDir := strings.TrimSpace(r.FormValue("dest"))
	if destDir == "" {
		destDir = initialCwd
	}
	destPath := filepath.Join(filepath.Clean(destDir), filepath.Base(header.Filename))

	// Inject mv into the shell — inherits the shell's effective user (e.g. root after sudo su).
	mvCmd := fmt.Sprintf("\nmv %s %s && echo 'Uploaded: %s'\n",
		shellQuote(tmpName), shellQuote(destPath), filepath.Base(header.Filename))
	s.mu.Lock()
	s.ptty.Write([]byte(mvCmd)) //nolint:errcheck
	s.mu.Unlock()

	fmt.Fprintf(w, `{"ok":true,"dest":%q}`, destPath)
}

func handleDownload(w http.ResponseWriter, r *http.Request) {
	if !isAuthed(r) {
		http.Error(w, "unauthorized", http.StatusUnauthorized)
		return
	}
	path := r.URL.Query().Get("path")
	if path == "" {
		http.Error(w, "missing ?path=", http.StatusBadRequest)
		return
	}
	full := filepath.Clean(path)
	if !filepath.IsAbs(full) {
		full = filepath.Join(initialCwd, full)
	}
	if _, err := os.Stat(full); err != nil {
		http.Error(w, "file not found", http.StatusNotFound)
		return
	}
	w.Header().Set("Content-Disposition", `attachment; filename="`+filepath.Base(full)+`"`)
	http.ServeFile(w, r, full)
}