package server

import (
	"encoding/json"
	"log"
	"net/http"

	"github.com/x-grk/longpolling-remote-access/internal/proto"
)

// The browser terminal talks to the server over plain HTTP long-polling (the
// same transport the agent uses), so it works through any reverse proxy without
// WebSocket upgrade support.

// POST /api/panel/term/{agentID}/open - create a terminal session.
func (s *Server) handlePanelOpen(w http.ResponseWriter, r *http.Request) {
	agentID := r.PathValue("agentID")
	agent, err := s.db.GetAgent(agentID)
	if err != nil || agent == nil {
		log.Printf("panel open: agent %q not found (err=%v)", agentID, err)
		http.NotFound(w, r)
		return
	}
	sess := s.hub.CreateSession(agentID, agent.LoginUser)
	if admin := s.currentAdmin(r); admin != nil {
		s.db.Audit(admin.ID, agentID, "open_terminal:"+agent.TerminalUser())
	}
	writeJSON(w, map[string]string{"session_id": sess.ID})
}

// GET /api/panel/term/{sid}/out - long-poll for PTY output.
func (s *Server) handlePanelOut(w http.ResponseWriter, r *http.Request) {
	sess := s.hub.Session(r.PathValue("sid"))
	if sess == nil {
		writeJSON(w, map[string]any{"closed": true})
		return
	}
	msgs, alive := sess.PollOut(pollHold)
	if !alive {
		writeJSON(w, map[string]any{"closed": true})
		return
	}
	writeJSON(w, map[string]any{"frames": msgs})
}

// panelInMsg is what the browser posts for keystrokes/resize.
type panelInMsg struct {
	T    string `json:"t"` // "i" input, "r" resize
	D    string `json:"d,omitempty"`
	Cols uint16 `json:"cols,omitempty"`
	Rows uint16 `json:"rows,omitempty"`
	// Seq numbers the messages of a session from 1; 0 from a page that
	// predates it.
	Seq uint64 `json:"seq,omitempty"`
}

// POST /api/panel/term/{sid}/in - send keystrokes/resize to the agent PTY.
func (s *Server) handlePanelIn(w http.ResponseWriter, r *http.Request) {
	sess := s.hub.Session(r.PathValue("sid"))
	if sess == nil {
		http.Error(w, "closed", http.StatusGone)
		return
	}
	var m panelInMsg
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<20)).Decode(&m); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}
	if m.Seq > 0 && !sess.TakeSeq(m.Seq) {
		w.WriteHeader(http.StatusNoContent) // a repeat of one already taken
		return
	}
	switch m.T {
	case "i":
		sess.PushIn(proto.InFrame{Type: proto.FrameStdin, Data: m.D})
	case "r":
		sess.PushIn(proto.InFrame{Type: proto.FrameResize, Cols: m.Cols, Rows: m.Rows})
	}
	w.WriteHeader(http.StatusNoContent)
}

// POST /api/panel/term/{sid}/close - tear the session down.
func (s *Server) handlePanelClose(w http.ResponseWriter, r *http.Request) {
	s.hub.CloseSession(r.PathValue("sid"))
	w.WriteHeader(http.StatusNoContent)
}