// Package proto defines all wire types shared between the daemon and anchor.
// Everything on the wire is newline-delimited JSON.
// Binary data (keys, signatures) is hex-encoded; signaling boxes are base64.
package proto

import (
	"crypto/sha256"
	"fmt"
	"time"
)

// ── Identity ──────────────────────────────────────────────────────────────────

// PeerID is a peer's stable identity: lowercase hex of the 32-byte Ed25519 public key (64 chars).
// This IS the peer — display names are advisory only and unauthenticated.
type PeerID string

// Short returns the first 16 hex chars grouped in 4s: "a1b2 c3d4 e5f6 0718".
func (p PeerID) Short() string {
	s := string(p)
	if len(s) < 16 {
		return s
	}
	return s[0:4] + " " + s[4:8] + " " + s[8:12] + " " + s[12:16]
}

// PeerInfo is a peer's self-description, included in the hello confirmation.
type PeerInfo struct {
	ID        PeerID    `json:"id"`
	Alias     string    `json:"alias"`      // advisory, not authenticated
	PublicKey string    `json:"public_key"` // Ed25519 pubkey, hex
	CreatedAt time.Time `json:"created_at"`
}

// ── Peer-to-peer message types (over the "yaw" DataChannel) ──────────────────

// MsgType identifies the kind of peer message.
type MsgType string

const (
	MsgChat         MsgType = "chat"
	MsgPm           MsgType = "pm"           // private message, §8
	MsgPeerGossip   MsgType = "peer_gossip"
	MsgFileListReq  MsgType = "file_list_req"
	MsgFileListResp MsgType = "file_list_resp"
	MsgFileOffer    MsgType = "file-offer"   // §9, hyphenated per spec
	MsgFileAccept   MsgType = "file-accept"
	MsgFileCancel   MsgType = "file-cancel"
	MsgFileDone     MsgType = "file-done"
	MsgPing            MsgType = "ping"
	MsgPong            MsgType = "pong"
	MsgHistoryRequest  MsgType = "history_request"
	MsgHistoryChunk    MsgType = "history_chunk"
)

// PmMessage is a private message sent directly over a single peer link (§8 "pm").
// The sender/receiver are implicit from the DataChannel; no room or from fields on the wire.
type PmMessage struct {
	Text string `json:"text"`
	Ts   int64  `json:"ts"` // Unix milliseconds
}

// PeerMessage is the top-level container sent over the "yaw" DataChannel.
// The spec types (hello, chat, pm, file-offer …) are flat JSON objects; we
// embed the fields directly using inline structs where needed, but for structured
// types we include the payload pointer. Unknown fields are ignored (forward compat).
// File chunks go over a separate binary DataChannel labeled "f:<xid>".
type PeerMessage struct {
	Type MsgType `json:"type"`

	// chat / pm fields (flat on the wire per spec §8)
	Mid  string `json:"mid,omitempty"`  // optional dedup id; required when relay hops > 0
	Room string `json:"room,omitempty"` // chat only
	Text string `json:"text,omitempty"` // chat and pm
	Ts   int64  `json:"ts,omitempty"`   // chat and pm (Unix ms)

	// Non-spec extensions (unknown types are silently ignored by other impls)
	Gossip       *PeerGossip   `json:"gossip,omitempty"`
	FileListResp *FileListResp `json:"file_list_resp,omitempty"`

	// file transfer (§9) — fields are flat on the wire
	Xid          string `json:"xid,omitempty"`
	Name         string `json:"name,omitempty"`
	Size         int64  `json:"size,omitempty"`
	SHA256       string `json:"sha256,omitempty"`
	ResumeOffset int64  `json:"resume_offset,omitempty"` // waste-go ext: non-zero in file-accept when resuming

	// file-done / file-cancel / file-accept just need xid (already above)
	Reason string `json:"reason,omitempty"` // file-cancel

	Seq *uint64 `json:"seq,omitempty"` // ping/pong

	// history_request fields
	Since int64 `json:"since,omitempty"` // Unix ms; 0 = no lower bound
	Limit int   `json:"limit,omitempty"`

	// history_chunk fields
	History     []HistoryEntry `json:"history,omitempty"`
	HistoryDone bool           `json:"history_done,omitempty"`
}

// ResumableFile describes a partially-downloaded file found on daemon startup.
type ResumableFile struct {
	Name   string `json:"name"`
	SHA256 string `json:"sha256"`
	From   string `json:"from"`    // peer ID hex
	Size   int64  `json:"size"`
	Offset int64  `json:"offset"`  // bytes already received
}

// HistoryEntry is one message in a history_chunk response.
type HistoryEntry struct {
	Mid       string `json:"mid"`
	From      string `json:"from"`       // peer ID hex
	FromAlias string `json:"from_alias"` // advisory
	Text      string `json:"text"`
	Ts        int64  `json:"ts"` // Unix ms
}

// ChatMessage is a group chat message (wire type "chat", §8).
// Also used internally for persisting PMs after they are received.
type ChatMessage struct {
	Mid   string  `json:"mid,omitempty"`   // optional dedup id (required when relay hops > 0)
	MsgID string  `json:"msg_id,omitempty"` // EXT-007: content-addressed gossip ID
	From  PeerID  `json:"from,omitempty"`  // set by receiver from DC context; not on wire for pm
	To    *PeerID `json:"to,omitempty"`    // internal only — not transmitted; set for DMs
	Room  string  `json:"room"`
	Text  string  `json:"text"`
	Ts    int64   `json:"ts"` // Unix milliseconds
}

// ComputeMsgID returns the EXT-007 content-addressed ID for a message.
// sha256(fromID \x00 room \x00 ts_decimal \x00 text)
func ComputeMsgID(fromID PeerID, room string, ts int64, text string) string {
	h := sha256.New()
	fmt.Fprintf(h, "%s\x00%s\x00%d\x00%s", string(fromID), room, ts, text)
	return fmt.Sprintf("sha256:%x", h.Sum(nil))
}

// PeerGossip shares known peer addresses.
type PeerGossip struct {
	Peers []GossipEntry `json:"peers"`
}

// GossipEntry is one peer hint shared via gossip.
type GossipEntry struct {
	Peer     PeerInfo  `json:"peer"`
	AddrHint string    `json:"addr_hint"` // IP:port hint, may be behind NAT
	LastSeen time.Time `json:"last_seen"`
}

// FileEntry describes a single file in a peer's shared directory.
type FileEntry struct {
	Name      string `json:"name"`
	SizeBytes int64  `json:"size_bytes"`
	Path      string `json:"path,omitempty"` // relative path including filename
}

// ShareEntry describes one persistent share root.
type ShareEntry struct {
	Path     string   `json:"path"`
	Networks []string `json:"networks"` // ["*"] = global
}

// FileListResp is the payload for MsgFileListResp.
// MsgFileListReq carries no payload — it is a zero-field request.
type FileListResp struct {
	Files []FileEntry `json:"files"`
}

// FileOffer is used internally when emitting EvtIncomingFile to the IPC layer.
// On the wire, file-offer fields are flat inside PeerMessage (xid/name/size/sha256).
type FileOffer struct {
	Xid    string `json:"xid"`
	Name   string `json:"name"`
	Size   int64  `json:"size"`
	SHA256 string `json:"sha256"`
}

// ── DataChannel hello (YAW/2 §6) ─────────────────────────────────────────────

// HelloMessage is the first message sent on the "yaw" DataChannel.
// The signature binds this identity to the specific DTLS session.
// The Invite field is a waste-go extension (§ waste-go/extensions.md):
// when RequireInvite is enabled on a network, peers that omit or present
// an invalid signed invite are disconnected. YAW/2-only peers ignore this field.
type HelloMessage struct {
	Type   string   `json:"type"`             // always "hello"
	ID     string   `json:"id"`               // hex pubkey
	Nick   string   `json:"nick"`             // alias
	Caps   []string `json:"caps"`             // capability list, e.g. ["chat","file"]
	Sig    string   `json:"sig"`              // hex ed25519 sig over HelloBindString
	Invite string   `json:"invite,omitempty"` // waste-go ext: signed waste: invite string
}

// HelloBindString returns the bytes the hello signature covers:
// "yaw/2 bind" || localDTLSFingerprint(32 bytes) || remoteDTLSFingerprint(32 bytes)
func HelloBindString(localFP, remoteFP []byte) []byte {
	buf := []byte("yaw/2 bind")
	buf = append(buf, localFP...)
	buf = append(buf, remoteFP...)
	return buf
}

// ── Signaling payload (sealed inside nacl/box, exchanged via anchor) ──────────

// SignalingKind identifies the kind of sealed signaling payload.
type SignalingKind string

const (
	SigOffer     SignalingKind = "offer"
	SigAnswer    SignalingKind = "answer"
	SigCandidate SignalingKind = "candidate"
	SigBye       SignalingKind = "bye"
	SigEkey      SignalingKind = "ekey" // YAW/2.1: ephemeral key exchange
)

// SignalingPayload is the JSON plaintext sealed inside a crypto_box (YAW/2 §5 / §5.4′).
type SignalingPayload struct {
	Kind  SignalingKind `json:"kind"`
	SDP   string        `json:"sdp,omitempty"`   // offer / answer
	Cand  string        `json:"cand,omitempty"`  // trickle ICE candidate line
	Mid   string        `json:"mid,omitempty"`   // media stream id for candidate
	MLine int           `json:"mline,omitempty"` // media line index

	// YAW/2.1 ekey fields (sealed under static keys)
	V       string `json:"v,omitempty"`        // "yaw/2.1"
	EPK     string `json:"epk,omitempty"`      // hex-encoded ephemeral X25519 pubkey (32 bytes)
	EkeySig string `json:"ekey_sig,omitempty"` // hex Ed25519 sig over ekey bind bytes
}

// ── Anchor WebSocket wire types (YAW/2 §5) ────────────────────────────────────

// AnchorMsgType identifies anchor WebSocket messages.
type AnchorMsgType string

const (
	AnchorChallenge AnchorMsgType = "challenge"
	AnchorJoin      AnchorMsgType = "join"
	AnchorJoined    AnchorMsgType = "joined"
	AnchorPeerJoin  AnchorMsgType = "peer-join"
	AnchorPeerLeave AnchorMsgType = "peer-leave"
	AnchorTo        AnchorMsgType = "to"
	AnchorFrom      AnchorMsgType = "from"
	AnchorNoPeer    AnchorMsgType = "no-peer"
)

// AnchorMessage covers all WebSocket frames to/from the anchor.
type AnchorMessage struct {
	Type  AnchorMsgType `json:"type"`
	Nonce string        `json:"nonce,omitempty"` // challenge nonce, hex
	ID    string        `json:"id,omitempty"`    // peer hex id
	Net   string        `json:"net,omitempty"`   // hashed network name
	Sig   string        `json:"sig,omitempty"`   // ed25519 sig over (nonce||net), hex
	Peers []string      `json:"peers,omitempty"` // joined: list of peer hex ids in network
	To    string        `json:"to,omitempty"`    // target peer hex id
	From  string        `json:"from,omitempty"`  // sender peer hex id
	Box   string        `json:"box,omitempty"`   // base64 nacl/box sealed payload
}

// ── IPC protocol (daemon ↔ local UI) ─────────────────────────────────────────

// IpcMsgType identifies IPC messages.
type IpcMsgType string

const (
	// Commands (UI → daemon)
	CmdSendMessage  IpcMsgType = "send_message"
	CmdJoinNetwork  IpcMsgType = "join_network"  // fields: network_name (plaintext)
	CmdLeaveNetwork IpcMsgType = "leave_network"
	CmdGetState     IpcMsgType = "get_state"
	CmdSendFile       IpcMsgType = "send_file"
	CmdSetShareDir    IpcMsgType = "set_share_dir"    // set per-network share directory at runtime
	CmdGenerateInvite IpcMsgType = "generate_invite"
	CmdGetFileList    IpcMsgType = "get_file_list"
	CmdExportIdentity IpcMsgType = "export_identity"  // returns encrypted backup blob
	CmdImportIdentity IpcMsgType = "import_identity"  // replaces identity from backup blob
	CmdAddShare       IpcMsgType = "add_share"        // add a share root; fields: path, networks
	CmdRemoveShare    IpcMsgType = "remove_share"      // remove a share root; field: path
	CmdListShares     IpcMsgType = "list_shares"       // returns shares_list event
	CmdCreateRoom       IpcMsgType = "create_room"        // field: room (name)
	CmdSetDownloadDir   IpcMsgType = "set_download_dir"   // set per-network download directory at runtime; fields: network_id, path

	// Events (daemon → UI)
	EvtMessageReceived  IpcMsgType = "message_received"
	EvtPeerConnected    IpcMsgType = "peer_connected"
	EvtPeerDisconnected IpcMsgType = "peer_disconnected"
	EvtSessionReady     IpcMsgType = "session_ready"   // DataChannel open + hello verified
	EvtPeerStatus       IpcMsgType = "peer_status"     // ICE connection state + candidate type
	EvtIncomingFile     IpcMsgType = "incoming_file"
	EvtFileProgress     IpcMsgType = "file_progress"
	EvtStateSnapshot    IpcMsgType = "state_snapshot"
	EvtError            IpcMsgType = "error"
	EvtInviteGenerated  IpcMsgType = "invite_generated"
	EvtFileList         IpcMsgType = "file_list"
	EvtFileComplete     IpcMsgType = "file_complete"
	EvtNetworkJoined    IpcMsgType = "network_joined"
	EvtNetworkLeft      IpcMsgType = "network_left"
	EvtIdentityExported IpcMsgType = "identity_exported"
	EvtIdentityImported IpcMsgType = "identity_imported"
	EvtSharesList       IpcMsgType = "shares_list"
	EvtRoomCreated      IpcMsgType = "room_created"    // field: room (name)
	EvtHistoryLoaded      IpcMsgType = "history_loaded"       // fields: room, messages
	EvtResumableTransfers IpcMsgType = "resumable_transfers"  // field: resumable_files
)

// NetworkInfo summarises one joined network for state_snapshot and network_joined events.
type NetworkInfo struct {
	NetworkID   string    `json:"network_id"`
	NetworkName string    `json:"network_name"`
	LocalPeer   *PeerInfo `json:"local_peer,omitempty"`
	ShareDir    string    `json:"share_dir,omitempty"`    // absolute path; empty = not sharing
	DownloadDir string    `json:"download_dir,omitempty"` // absolute path for received files
}

// IpcMessage covers both commands and events.
type IpcMessage struct {
	Type IpcMsgType `json:"type"`

	// optional: scopes a command/event to a specific network.
	// When absent, defaults to the first (or only) joined network.
	NetworkID string `json:"network_id,omitempty"`

	// send_message
	Room string  `json:"room,omitempty"`
	To   *PeerID `json:"to,omitempty"`
	Body string  `json:"body,omitempty"`

	// join_network / leave_network
	NetworkName   string `json:"network_name,omitempty"`
	NetworkHash   string `json:"network_hash,omitempty"`    // 64-char hex (yaw2 `net` field); alternative to network_name
	ShareDir      string `json:"share_dir,omitempty"`       // optional per-network share directory
	RequireInvite bool   `json:"require_invite,omitempty"`  // waste-go ext: reject peers without valid signed invite
	InviteString  string `json:"invite_string,omitempty"`   // waste-go ext: the invite used to join (stored in mesh)

	// send_file / set_share_dir / file_complete path
	Path string `json:"path,omitempty"`

	// events
	Peer           *PeerInfo    `json:"peer,omitempty"`
	PeerID         *PeerID      `json:"peer_id,omitempty"`
	Nick           string       `json:"nick,omitempty"`
	Message        *ChatMessage `json:"message,omitempty"`
	Offer          *FileOffer   `json:"offer,omitempty"`
	TransferID     string       `json:"transfer_id,omitempty"`
	BytesReceived  int64        `json:"bytes_received,omitempty"`
	TotalBytes     int64        `json:"total_bytes,omitempty"`
	// state_snapshot fields (existing shape preserved for backward compat)
	MasterAlias    string        `json:"master_alias,omitempty"` // daemon's alias (available before any network join)
	MasterID       string        `json:"master_id,omitempty"`    // daemon's master public key hex
	LocalPeer      *PeerInfo     `json:"local_peer,omitempty"`
	ConnectedPeers []PeerInfo    `json:"connected_peers,omitempty"`
	Rooms          []string      `json:"rooms,omitempty"`
	// multi-network: all joined networks (additive)
	Networks       []NetworkInfo `json:"networks,omitempty"`
	ErrorMessage   string       `json:"error_message,omitempty"`
	InviteGenerated string      `json:"invite,omitempty"`
	Files          []FileEntry    `json:"files,omitempty"`
	Messages        []ChatMessage   `json:"messages,omitempty"`          // history_loaded
	ResumableFiles  []ResumableFile `json:"resumable_files,omitempty"`   // resumable_transfers
	Shares         []ShareEntry `json:"shares,omitempty"`
	ShareNetworks  []string     `json:"network_ids,omitempty"` // for add_share command: scope to specific network IDs, or ["*"] for global
	// export_identity / import_identity
	Passphrase     string       `json:"passphrase,omitempty"` // import only; never echoed back
	Backup         string       `json:"backup,omitempty"`     // JSON backup blob
	// peer_status — ICE connection quality
	ConnState     string `json:"conn_state,omitempty"`     // pion PeerConnectionState string
	CandidateType string `json:"candidate_type,omitempty"` // host | srflx | relay | unknown
	RemoteAddress string `json:"remote_address,omitempty"` // remote IP:port of active candidate pair
}