package yggdrasil

import (
	"context"
	"encoding/hex"
	"errors"
	"net"
	"strconv"
	"strings"
	"time"

	"github.com/yggdrasil-network/yggdrasil-go/src/crypto"
)

// Dialer represents an Yggdrasil connection dialer.
type Dialer struct {
	core *Core
}

// Dial opens a session to the given node. The first parameter should be
// "pubkey" or "nodeid" and the second parameter should contain a hexadecimal
// representation of the target. It uses DialContext internally.
func (d *Dialer) Dial(network, address string) (net.Conn, error) {
	return d.DialContext(nil, network, address)
}

// DialContext is used internally by Dial, and should only be used with a
// context that includes a timeout. It uses DialByNodeIDandMask internally when
// the network is "nodeid", or DialByPublicKey when the network is "pubkey".
func (d *Dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
	var nodeID crypto.NodeID
	var nodeMask crypto.NodeID
	// Process
	switch network {
	case "pubkey":
		dest, err := hex.DecodeString(address)
		if err != nil {
			return nil, err
		}
		if len(dest) != crypto.BoxPubKeyLen {
			return nil, errors.New("invalid key length supplied")
		}
		var pubKey crypto.BoxPubKey
		copy(pubKey[:], dest)
		return d.DialByPublicKey(ctx, &pubKey)
	case "nodeid":
		// A node ID was provided - we don't need to do anything special with it
		if tokens := strings.Split(address, "/"); len(tokens) == 2 {
			l, err := strconv.Atoi(tokens[1])
			if err != nil {
				return nil, err
			}
			dest, err := hex.DecodeString(tokens[0])
			if err != nil {
				return nil, err
			}
			copy(nodeID[:], dest)
			for idx := 0; idx < l; idx++ {
				nodeMask[idx/8] |= 0x80 >> byte(idx%8)
			}
		} else {
			dest, err := hex.DecodeString(tokens[0])
			if err != nil {
				return nil, err
			}
			copy(nodeID[:], dest)
			for i := range nodeMask {
				nodeMask[i] = 0xFF
			}
		}
		return d.DialByNodeIDandMask(ctx, &nodeID, &nodeMask)
	default:
		// An unexpected address type was given, so give up
		return nil, errors.New("unexpected address type")
	}
}

// DialByNodeIDandMask opens a session to the given node based on raw NodeID
// parameters. If ctx is nil or has no timeout, then a default timeout of 6
// seconds will apply, beginning *after* the search finishes.
func (d *Dialer) DialByNodeIDandMask(ctx context.Context, nodeID, nodeMask *crypto.NodeID) (net.Conn, error) {
	startDial := time.Now()
	conn := newConn(d.core, nodeID, nodeMask, nil)
	if err := conn.search(); err != nil {
		// TODO: make searches take a context, so they can be cancelled early
		conn.Close()
		return nil, err
	}
	endSearch := time.Now()
	d.core.log.Debugln("Dial searched for:", nodeID, "in time:", endSearch.Sub(startDial))
	conn.session.setConn(nil, conn)
	var cancel context.CancelFunc
	if ctx == nil {
		ctx = context.Background()
	}
	ctx, cancel = context.WithTimeout(ctx, 6*time.Second)
	defer cancel()
	select {
	case <-conn.session.init:
		endInit := time.Now()
		d.core.log.Debugln("Dial initialized session for:", nodeID, "in time:", endInit.Sub(endSearch))
		d.core.log.Debugln("Finished dial for:", nodeID, "in time:", endInit.Sub(startDial))
		return conn, nil
	case <-ctx.Done():
		conn.Close()
		return nil, errors.New("session handshake timeout")
	}
}

// DialByPublicKey opens a session to the given node based on the public key. If
// ctx is nil or has no timeout, then a default timeout of 6 seconds will apply,
// beginning *after* the search finishes.
func (d *Dialer) DialByPublicKey(ctx context.Context, pubKey *crypto.BoxPubKey) (net.Conn, error) {
	nodeID := crypto.GetNodeID(pubKey)
	var nodeMask crypto.NodeID
	for i := range nodeMask {
		nodeMask[i] = 0xFF
	}
	return d.DialByNodeIDandMask(ctx, nodeID, &nodeMask)
}