package telegram

import (
	"errors"
	"fmt"
	"strings"

	"dev.narayana.im/narayana/telegabber/e2ee"
	"dev.narayana.im/narayana/telegabber/xmpp/gateway"
)

// OmemoDeviceStatus is one known device of a chat's peer - shared data
// backing both the text "/omemo devices" command and the ad-hoc command's
// form (xmpp/omemo_command.go), so both surfaces always agree.
type OmemoDeviceStatus struct {
	ID      string
	Trusted bool
}

// OmemoChatStatus is a chat's current OMEMO state - shared data backing
// both the text "/omemo" command and the ad-hoc command's form.
type OmemoChatStatus struct {
	Mode        string // account-wide mode: "on"/"auto"/"off" (e2ee.Mode.String())
	OverrideSet bool
	Override    bool // meaningful only if OverrideSet
	Effective   bool // e2ee.ShouldEncrypt's actual verdict right now
	Devices     []OmemoDeviceStatus
}

// GetOmemoChatStatus reports chatID's current OMEMO state.
func (c *Client) GetOmemoChatStatus(chatID int64) (OmemoChatStatus, error) {
	backend, ok := gateway.E2EE.Backend()
	if !ok {
		return OmemoChatStatus{}, errors.New("OMEMO is not enabled on this transport")
	}
	owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(chatID, false))

	mode, err := e2ee.ParseMode(c.Session.OMEMO)
	if err != nil {
		return OmemoChatStatus{}, err
	}
	override, isSet, err := backend.Override(owner)
	if err != nil {
		return OmemoChatStatus{}, err
	}
	active, err := e2ee.ShouldEncrypt(backend, owner, mode)
	if err != nil {
		return OmemoChatStatus{}, err
	}
	devices, err := backend.Devices(owner, e2ee.PeerID(c.jid))
	if err != nil {
		return OmemoChatStatus{}, err
	}

	statuses := make([]OmemoDeviceStatus, len(devices))
	for i, d := range devices {
		statuses[i] = OmemoDeviceStatus{ID: string(d.ID), Trusted: d.Trusted}
	}

	return OmemoChatStatus{
		Mode:        mode.String(),
		OverrideSet: isSet,
		Override:    override,
		Effective:   active,
		Devices:     statuses,
	}, nil
}

// SetOmemoChatOverride forces (on non-nil) or clears (on nil) chatID's
// OMEMO override.
func (c *Client) SetOmemoChatOverride(chatID int64, on *bool) error {
	backend, ok := gateway.E2EE.Backend()
	if !ok {
		return errors.New("OMEMO is not enabled on this transport")
	}
	owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(chatID, false))
	if on == nil {
		return backend.ClearOverride(owner)
	}
	return backend.SetOverride(owner, *on)
}

// SetOmemoDeviceBlocked blocks or unblocks one of chatID's peer's devices.
func (c *Client) SetOmemoDeviceBlocked(chatID int64, deviceID string, blocked bool) error {
	backend, ok := gateway.E2EE.Backend()
	if !ok {
		return errors.New("OMEMO is not enabled on this transport")
	}
	owner := e2ee.OwnedPeer(c.Session.Login, gateway.CHATJID(chatID, false))
	peer := e2ee.PeerID(c.jid)
	if blocked {
		return backend.BlockDevice(owner, peer, e2ee.DeviceID(deviceID))
	}
	return backend.UnblockDevice(owner, peer, e2ee.DeviceID(deviceID))
}

// cmdOmemoChat implements the chat-scoped "/omemo" text command: with no
// arguments, reports this chat's current OMEMO state (account-wide mode,
// any override, and the resulting effective state); "on"/"off" forces this
// specific chat regardless of the account-wide mode; "clear" removes that
// override, reverting to following the account-wide mode; "devices ..."
// manages this chat's peer's device trust (see cmdOmemoDevices). The
// ad-hoc command surface (xmpp/omemo_command.go) offers the same controls
// as a form, built from the same GetOmemoChatStatus/SetOmemoChatOverride/
// SetOmemoDeviceBlocked methods this uses.
func (c *Client) cmdOmemoChat(chatID int64, args []string) (string, bool) {
	if len(args) == 0 {
		return c.omemoChatStatusString(chatID)
	}

	switch args[0] {
	case "on", "off":
		on := args[0] == "on"
		if err := c.SetOmemoChatOverride(chatID, &on); err != nil {
			return err.Error(), false
		}
		return fmt.Sprintf("OMEMO forced %s for this chat", args[0]), true
	case "clear":
		if err := c.SetOmemoChatOverride(chatID, nil); err != nil {
			return err.Error(), false
		}
		return "OMEMO override cleared for this chat, now following the account-wide mode", true
	case "devices":
		return c.cmdOmemoDevices(chatID, args[1:])
	default:
		return "Usage: /omemo [on|off|clear|devices list|devices block <id>|devices accept <id>]", false
	}
}

func (c *Client) omemoChatStatusString(chatID int64) (string, bool) {
	status, err := c.GetOmemoChatStatus(chatID)
	if err != nil {
		return err.Error(), false
	}

	overrideText := "not set (following the account-wide mode)"
	if status.OverrideSet {
		overrideText = fmt.Sprintf("forced %s", onOffString(status.Override))
	}

	return fmt.Sprintf("Account-wide mode: %s\nThis chat's override: %s\nEffective right now: %s",
		status.Mode, overrideText, onOffString(status.Effective)), true
}

// cmdOmemoDevices lists, blocks, or accepts (unblocks) devices of chatID's
// real peer. TOFU trust itself always stays on (a never-before-seen
// device is always trusted automatically) - block/accept only manage a
// manual override layered on top of that, per e2ee.Backend.BlockDevice's
// doc comment.
func (c *Client) cmdOmemoDevices(chatID int64, args []string) (string, bool) {
	sub := "list"
	if len(args) > 0 {
		sub = args[0]
	}

	switch sub {
	case "list":
		status, err := c.GetOmemoChatStatus(chatID)
		if err != nil {
			return err.Error(), false
		}
		if len(status.Devices) == 0 {
			return "No known devices for this chat's peer yet", true
		}
		lines := make([]string, 0, len(status.Devices))
		for _, d := range status.Devices {
			lines = append(lines, fmt.Sprintf("%s: %s", d.ID, trustString(d.Trusted)))
		}
		return strings.Join(lines, "\n"), true
	case "block", "accept":
		if len(args) < 2 {
			return notEnoughArguments, false
		}
		if err := c.SetOmemoDeviceBlocked(chatID, args[1], sub == "block"); err != nil {
			return err.Error(), false
		}
		return fmt.Sprintf("Device %s %sed", args[1], sub), true
	default:
		return "Usage: /omemo devices [list|block <id>|accept <id>]", false
	}
}

func onOffString(b bool) string {
	if b {
		return "on"
	}
	return "off"
}

func trustString(trusted bool) string {
	if trusted {
		return "trusted"
	}
	return "blocked"
}