package config

import (
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"net"
	"os"
	"strings"

	"github.com/hyprspace/hyprspace/schema"
	"github.com/libp2p/go-libp2p/core/crypto"
	"github.com/libp2p/go-libp2p/core/peer"
	"github.com/multiformats/go-multiaddr"
	"github.com/multiformats/go-multibase"
	"github.com/yl2chen/cidranger"
)

// Config is the main Configuration Struct for Hyprspace.
type Config struct {
	Path                   string                `json:"-"`
	Interface              string                `json:"-"`
	ListenAddresses        []multiaddr.Multiaddr `json:"-"`
	BootstrapPeers         []multiaddr.Multiaddr `json:"-"`
	Peers                  []Peer                `json:"peers"`
	PeerLookup             PeerLookup            `json:"-"`
	PrivateKey             crypto.PrivKey        `json:"-"`
	BuiltinAddr4           net.IP                `json:"-"`
	BuiltinAddr6           net.IP                `json:"-"`
	Services               map[string]Service    `json:"-"`
	FilterPrivateAddresses bool                  `json:"-"`
	Domain                 string                `json:"-"`
}

// Peer defines a peer in the configuration. We might add more to this later.
type Peer struct {
	ID           peer.ID `json:"id"`
	Name         string  `json:"name"`
	BuiltinAddr4 net.IP  `json:"-"`
	BuiltinAddr6 net.IP  `json:"-"`
}

// PeerLookup is a helper struct for quickly looking up a peer based on various parameters
type PeerLookup struct {
	ByRoute cidranger.Ranger
	ByName  map[string]Peer
	ByNetID map[[4]byte]Peer
}

type RouteTableEntry struct {
	Net    net.IPNet
	Target Peer
}

// Service represents the configuration for a specific service provided by this node.
// Whitelist and Blacklist allow fine granularity in access control.
// If Blacklist is set, this will be evaluated first and any client id present in Blacklist will
// have access denied. Whitelist is evaluated after.
type Service struct {
	Target          multiaddr.Multiaddr
	EnableWhitelist bool
	Whitelist       map[peer.ID]struct{}
	Blacklist       map[peer.ID]struct{}
}

func (rte RouteTableEntry) Network() net.IPNet {
	return rte.Net
}

// Read initializes a config from a file.
func Read(path string) (*Config, error) {
	in, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	input := schema.Config{}
	result := Config{}

	// Read in config settings from file.
	err = json.Unmarshal(in, &input)
	if err != nil {
		return nil, err
	}

	_, keyBytes, err := multibase.Decode(input.PrivateKey)
	if err != nil {
		return nil, err
	}

	pk, err := crypto.UnmarshalPrivateKey(keyBytes)
	if err != nil {
		return nil, err
	}

	result.PrivateKey = pk

	peerID, err := peer.IDFromPrivateKey(result.PrivateKey)
	if err != nil {
		return nil, err
	}

	result.BuiltinAddr4 = mkBuiltinAddr4(peerID)
	result.BuiltinAddr6 = mkBuiltinAddr6(peerID)

	for _, addrString := range input.ListenAddresses {
		addr, err := multiaddr.NewMultiaddr(addrString)
		if err != nil {
			return nil, err
		}
		result.ListenAddresses = append(result.ListenAddresses, addr)
	}

	result.PeerLookup.ByRoute = cidranger.NewPCTrieRanger()
	result.PeerLookup.ByName = make(map[string]Peer)
	result.PeerLookup.ByNetID = make(map[[4]byte]Peer)
	result.Peers = make([]Peer, len(input.Peers))

	for i, configPeer := range input.Peers {
		p := Peer{}
		p.ID, err = peer.Decode(configPeer.Id)
		if err != nil {
			return nil, err
		}
		p.Name = configPeer.Name
		p.BuiltinAddr4 = mkBuiltinAddr4(p.ID)
		p.BuiltinAddr6 = mkBuiltinAddr6(p.ID)
		for _, r := range configPeer.Routes {
			_, network, err := net.ParseCIDR(r.Net)
			if err != nil {
				log.Fatal("[!] Invalid network:", r.Net)
			}

			result.PeerLookup.ByRoute.Insert(&RouteTableEntry{
				Net:    *network,
				Target: p,
			})

			fmt.Printf("[+] Route %s via /p2p/%s\n", network.String(), p.ID)
		}
		result.PeerLookup.ByRoute.Insert(&RouteTableEntry{
			Net: net.IPNet{
				IP:   p.BuiltinAddr4,
				Mask: net.CIDRMask(32, 32),
			},
			Target: p,
		})
		result.PeerLookup.ByRoute.Insert(&RouteTableEntry{
			Net: net.IPNet{
				IP:   p.BuiltinAddr6,
				Mask: net.CIDRMask(128, 128),
			},
			Target: p,
		})
		if configPeer.Name != "" {
			result.PeerLookup.ByName[strings.ToLower(configPeer.Name)] = p
		}
		result.PeerLookup.ByNetID[[4]byte(p.BuiltinAddr6[12:16])] = p
		result.Peers[i] = p
	}

	result.Services = make(map[string]Service)
	for name, service := range input.Services {
		addr, err := multiaddr.NewMultiaddr(service.Target)
		if err != nil {
			return nil, err
		}
		whitelist := make(map[peer.ID]struct{})
		blacklist := make(map[peer.ID]struct{})
		for _, p := range service.Acl.Whitelist {
			cfgPeer, err := FindPeerByCLIRef(result.Peers, p)
			if err != nil {
				return nil, err
			}
			if cfgPeer == nil {
				return nil, errors.New("unknown peer: " + p)
			}
			whitelist[cfgPeer.ID] = struct{}{}
		}
		for _, peerStr := range service.Acl.Blacklist {
			cfgPeer, err := FindPeerByCLIRef(result.Peers, peerStr)
			if err != nil {
				return nil, err
			}
			if cfgPeer == nil {
				return nil, errors.New("unknown peer: " + peerStr)
			}
			blacklist[cfgPeer.ID] = struct{}{}
		}
		result.Services[name] = Service{
			Target:          addr,
			EnableWhitelist: service.Acl.EnableWhitelist,
			Whitelist:       whitelist,
			Blacklist:       blacklist,
		}
	}

	result.FilterPrivateAddresses = input.FilterPrivateAddresses

	result.Domain = input.Domain
	if result.Domain == "" {
		result.Domain = "hyprspace"
	}

	for _, addrString := range input.BootstrapPeers {
		addr, err := multiaddr.NewMultiaddr(addrString)
		if err != nil {
			return nil, err
		}
		result.BootstrapPeers = append(result.BootstrapPeers, addr)
	}

	// Overwrite path of config to input.
	result.Path = path
	return &result, nil
}

func FindPeer(peers []Peer, needle peer.ID) (*Peer, bool) {
	for _, p := range peers {
		if p.ID == needle {
			return &p, true
		}
	}
	return nil, false
}

func FindPeerByName(peers []Peer, needle string) (*Peer, bool) {
	for _, p := range peers {
		if p.Name == needle {
			return &p, true
		}
	}
	return nil, false
}

// FindPeerByIDPrefix returns the unique peer whose ID starts with needle.
// Returns (nil, nil) if no peer matches.
// Returns (nil, error) if more than one peer matches (ambiguous prefix).
func FindPeerByIDPrefix(peers []Peer, needle string) (*Peer, error) {
	var match *Peer
	count := 0
	for i := range peers {
		if strings.HasPrefix(peers[i].ID.String(), needle) {
			match = &peers[i]
			count++
		}
	}
	if count > 1 {
		return nil, fmt.Errorf("ambiguous peer prefix %q matches %d peers", needle, count)
	}
	return match, nil
}

// FindPeerByCLIRef resolves a CLI peer reference: "@name" for name lookup,
// otherwise a peer ID prefix. Returns (nil, nil) on no match,
// (nil, error) only on ambiguous ID prefix.
func FindPeerByCLIRef(peers []Peer, needle string) (*Peer, error) {
	if needle == "" {
		return nil, nil
	}
	if strings.HasPrefix(needle, "@") {
		name := strings.TrimPrefix(needle, "@")
		p, _ := FindPeerByName(peers, name)
		return p, nil
	}
	return FindPeerByIDPrefix(peers, needle)
}

func (cfg Config) FindRoute(needle net.IPNet) (*RouteTableEntry, bool) {
	networks, err := cfg.PeerLookup.ByRoute.CoveredNetworks(needle)
	if err != nil {
		fmt.Println(err)
		return nil, false
	} else if len(networks) == 0 {
		return nil, false
	} else if len(networks) > 1 {
		for _, n := range networks {
			fmt.Printf("[!] Found duplicate route %s to /p2p/%s for %s\n", n.Network(), n.(RouteTableEntry).Target.ID, needle)
		}
	}
	return networks[0].(*RouteTableEntry), true
}

func (cfg Config) FindRouteForIP(needle net.IP) (*RouteTableEntry, bool) {
	networks, err := cfg.PeerLookup.ByRoute.ContainingNetworks(needle)
	if err != nil {
		fmt.Println(err)
		return nil, false
	} else if len(networks) == 0 {
		return nil, false
	} else if len(networks) > 1 {
		for _, n := range networks {
			fmt.Printf("[!] Found duplicate route %s to /p2p/%s for %s\n", n.Network(), n.(RouteTableEntry).Target.ID, needle)
		}
	}
	return networks[0].(*RouteTableEntry), true
}