package api

import (
	"encoding/json"
	"errors"
	"net/http"
	"strings"

	"github.com/ponzischeme89/memby/server/internal/cache"
	"github.com/ponzischeme89/memby/server/internal/emby"
	"github.com/ponzischeme89/memby/server/internal/store"
)

type loginRequest struct {
	Username   string `json:"username"`
	Password   string `json:"password"`
	DeviceID   string `json:"deviceId"`
	DeviceName string `json:"deviceName"`
}

type loginResponse struct {
	Token             string `json:"token"`
	UserID            string `json:"userId"`
	Username          string `json:"username"`
	ServerID          string `json:"serverId"`
	ActiveClients     int    `json:"activeClients,omitempty"`
	MaxClientsPerUser int    `json:"maxClientsPerUser"`
}

type authPolicyResponse struct {
	MaxClientsPerUser int `json:"maxClientsPerUser"`
}

func (s *Server) handleAuthPolicy(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, authPolicyResponse{
		MaxClientsPerUser: s.cfg.MaxClientsPerUser,
	})
}

// handleLogin exchanges Emby credentials for a gateway token.
//
// The Emby access token stays here: the TV only ever holds the gateway token, so
// revoking a device is a DELETE in Postgres rather than an Emby-side cleanup.
func (s *Server) handleLogin(w http.ResponseWriter, r *http.Request) {
	var req loginRequest
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 8<<10)).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "malformed request body")
		return
	}
	req.Username = strings.TrimSpace(req.Username)
	if req.Username == "" {
		writeError(w, http.StatusBadRequest, "username is required")
		return
	}
	if req.DeviceID == "" {
		req.DeviceID = "memby-tv"
	}
	req.DeviceName = strings.TrimSpace(req.DeviceName)
	if req.DeviceName == "" {
		// Compatibility for APKs released before device naming. New clients require an
		// editable name in their UI, but an older TV must still be able to sign in while
		// the household rollout is in progress.
		req.DeviceName = "Memby TV"
	}
	if len([]rune(req.DeviceName)) > 80 {
		writeError(w, http.StatusBadRequest, "device name is too long")
		return
	}

	auth, err := s.emby.Authenticate(
		r.Context(), req.Username, req.Password, req.DeviceID, req.DeviceName,
	)
	if err != nil {
		// Never echo Emby's body here: a failed sign-in is the one place a wrong
		// password could be reflected back.
		s.log.Warn("emby authentication failed", "username", req.Username)
		writeError(w, http.StatusUnauthorized, "sign-in failed")
		return
	}

	token, err := newToken()
	if err != nil {
		s.log.Error("token generation failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not issue a token")
		return
	}

	sess := store.Session{
		TokenHash:  hashToken(token),
		EmbyUserID: auth.User.ID,
		EmbyToken:  auth.AccessToken,
		Username:   auth.User.Name,
		ServerID:   auth.ServerID,
		DeviceID:   req.DeviceID,
		DeviceName: req.DeviceName,
	}
	if sess.Username == "" {
		sess.Username = req.Username
	}
	replacedHash, activeClients, err := s.store.CreateSession(
		r.Context(), sess, s.cfg.MaxClientsPerUser,
	)
	if errors.Is(err, store.ErrDeviceLimit) {
		if revokeErr := s.emby.Logout(r.Context(), emby.Credentials{
			UserID: auth.User.ID, Token: auth.AccessToken,
			DeviceID: req.DeviceID, DeviceName: req.DeviceName,
		}); revokeErr != nil {
			s.log.Warn("could not retire refused emby session", "error", revokeErr)
		}
		s.log.Warn("device allowance reached",
			"username", sess.Username,
			"active_clients", activeClients,
			"max_clients", s.cfg.MaxClientsPerUser,
		)
		writeJSON(w, http.StatusConflict, map[string]any{
			"error":             "device_limit_reached",
			"message":           "This account has reached its Memby device allowance.",
			"activeClients":     activeClients,
			"maxClientsPerUser": s.cfg.MaxClientsPerUser,
		})
		return
	}
	if err != nil {
		_ = s.emby.Logout(r.Context(), emby.Credentials{
			UserID: auth.User.ID, Token: auth.AccessToken,
			DeviceID: req.DeviceID, DeviceName: req.DeviceName,
		})
		s.log.Error("session persist failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not start a session")
		return
	}
	if len(replacedHash) > 0 {
		_ = s.cache.Delete(r.Context(), cache.SessionKey(hexHash(replacedHash)))
	}

	writeJSON(w, http.StatusOK, loginResponse{
		Token:             token,
		UserID:            sess.EmbyUserID,
		Username:          sess.Username,
		ServerID:          sess.ServerID,
		ActiveClients:     activeClients,
		MaxClientsPerUser: s.cfg.MaxClientsPerUser,
	})
}

func (s *Server) handleLogout(w http.ResponseWriter, r *http.Request, sess store.Session) {
	if err := s.store.DeleteSession(r.Context(), sess.TokenHash); err != nil {
		s.log.Error("session delete failed", "error", err)
	}
	_ = s.cache.Delete(r.Context(), cache.SessionKey(hexHash(sess.TokenHash)))
	_ = s.cache.InvalidateUser(r.Context(), sess.EmbyUserID)
	w.WriteHeader(http.StatusNoContent)
}

// handleSession lets the TV confirm a stored token is still good before rendering.
func (s *Server) handleSession(w http.ResponseWriter, _ *http.Request, sess store.Session) {
	writeJSON(w, http.StatusOK, loginResponse{
		UserID:            sess.EmbyUserID,
		Username:          sess.Username,
		ServerID:          sess.ServerID,
		MaxClientsPerUser: s.cfg.MaxClientsPerUser,
	})
}