package opnsense

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"

	"github.com/ngoduykhanh/wireguard-ui/model"
	"github.com/ngoduykhanh/wireguard-ui/util"
)

// PreviewClient is a single OPNsense client mapped into an admin-editable
// staging structure. It is not a model.Client yet - ToModel performs the
// final conversion at commit time.
type PreviewClient struct {
	SourceUUID          string   `json:"source_uuid,omitempty"`
	Name                string   `json:"name"`
	Email               string   `json:"email,omitempty"`
	Enabled             bool     `json:"enabled"`
	PublicKey           string   `json:"public_key"`
	PresharedKey        string   `json:"preshared_key,omitempty"`
	AllocatedIPs        []string `json:"allocated_ips"`
	AllowedIPs          []string `json:"allowed_ips"`
	PersistentKeepalive int      `json:"persistent_keepalive,omitempty"`
	AdditionalNotes     string   `json:"additional_notes,omitempty"`
	Warnings            []string `json:"warnings,omitempty"`
}

// PreviewServer is a single OPNsense WireGuard server instance mapped into
// an admin-editable staging structure, together with the clients OPNsense
// associated with it via its <peers> uuid list.
type PreviewServer struct {
	SourceUUID      string          `json:"source_uuid,omitempty"`
	ID              string          `json:"id"`
	Name            string          `json:"name"`
	Interface       string          `json:"interface"`
	Addresses       []string        `json:"addresses"`
	ListenPort      int             `json:"listen_port"`
	PrivateKey      string          `json:"private_key,omitempty"`
	PublicKey       string          `json:"public_key,omitempty"`
	EndpointAddress string          `json:"endpoint_address,omitempty"`
	DNSServers      []string        `json:"dns_servers,omitempty"`
	MTU             int             `json:"mtu,omitempty"`
	Enabled         bool            `json:"enabled"`
	Clients         []PreviewClient `json:"clients"`
	Warnings        []string        `json:"warnings,omitempty"`
}

// PreviewResult is the full response of the preview step: every server
// OPNsense defined, mapped and ready for the admin to review/edit before
// confirming the import. It is never written to the store by itself.
type PreviewResult struct {
	Servers []PreviewServer `json:"servers"`
}

var slugInvalidChars = regexp.MustCompile(`[^a-zA-Z0-9_-]+`)

// slugify turns a free-text name into a safe record-id/interface-name
// candidate (see util.ValidateRecordID / util.ValidateInterfaceName).
func slugify(name string) string {
	s := slugInvalidChars.ReplaceAllString(strings.TrimSpace(name), "-")
	s = strings.Trim(s, "-_")
	if s == "" {
		s = "opnsense-server"
	}
	return s
}

// uniqueID returns slug, or slug-2, slug-3, ... until it no longer collides
// with existingIDs or anything already produced in this same batch (used
// so importing several OPNsense servers whose names collide with each
// other, or with already-existing wireguard-ui-multi servers, still
// produces distinct IDs).
func uniqueID(slug string, existingIDs map[string]bool) string {
	candidate := slug
	if !existingIDs[candidate] {
		existingIDs[candidate] = true
		return candidate
	}
	for i := 2; ; i++ {
		candidate = fmt.Sprintf("%s-%d", slug, i)
		if !existingIDs[candidate] {
			existingIDs[candidate] = true
			return candidate
		}
	}
}

// truncateInterfaceName shortens a candidate interface name to fit
// util.ValidateInterfaceName's 15-char limit while staying unique within
// this batch, reusing the numeric suffix strategy from uniqueID.
func truncateInterfaceName(slug string, existingNames map[string]bool) string {
	const maxLen = 15
	base := slug
	if len(base) > maxLen {
		base = base[:maxLen]
	}
	if !existingNames[base] && util.ValidateInterfaceName(base) {
		existingNames[base] = true
		return base
	}
	for i := 2; ; i++ {
		suffix := fmt.Sprintf("-%d", i)
		cut := maxLen - len(suffix)
		if cut < 1 {
			cut = 1
		}
		truncated := slug
		if len(truncated) > cut {
			truncated = truncated[:cut]
		}
		candidate := truncated + suffix
		if !existingNames[candidate] && util.ValidateInterfaceName(candidate) {
			existingNames[candidate] = true
			return candidate
		}
	}
}

// ToPreview maps a ParsedConfig into admin-editable PreviewServer/
// PreviewClient structures. existingServerIDs should list every server ID
// already present in the store (see store.IStore.GetServers), so imported
// IDs never collide with them.
func ToPreview(cfg *ParsedConfig, existingServerIDs []string) *PreviewResult {
	usedIDs := make(map[string]bool, len(existingServerIDs))
	for _, id := range existingServerIDs {
		usedIDs[id] = true
	}
	usedIfaceNames := make(map[string]bool)

	// index clients by their OPNsense uuid so each server's <peers> list
	// (the only place the client<->server association is recorded) can
	// pull in the right ones.
	clientsByUUID := make(map[string]rawClient, len(cfg.Clients))
	for _, c := range cfg.Clients {
		clientsByUUID[c.UUID] = c
	}

	result := &PreviewResult{}

	for _, rs := range cfg.Servers {
		ps := PreviewServer{
			SourceUUID: rs.UUID,
			Name:       rs.Name,
			Enabled:    isTruthy(rs.Enabled),
			DNSServers: splitList(rs.DNS),
		}
		if ps.Name == "" {
			ps.Name = fmt.Sprintf("opnsense-server-%s", rs.Instance)
		}

		slug := slugify(ps.Name)
		ps.ID = uniqueID(slug, usedIDs)
		ps.Interface = truncateInterfaceName(slug, usedIfaceNames)

		ps.Addresses = splitList(rs.TunnelAddress)
		if len(ps.Addresses) == 0 {
			ps.Warnings = append(ps.Warnings, "no tunnel address found; please set the server's address range manually")
		} else if !util.ValidateServerAddresses(ps.Addresses) {
			ps.Warnings = append(ps.Warnings, "tunnel address is not valid CIDR; please fix before importing")
		}

		if rs.Port != "" {
			if port, err := strconv.Atoi(strings.TrimSpace(rs.Port)); err == nil && port > 0 && port <= 65535 {
				ps.ListenPort = port
			} else {
				ps.Warnings = append(ps.Warnings, fmt.Sprintf("invalid listen port %q; please set one manually", rs.Port))
			}
		} else {
			ps.Warnings = append(ps.Warnings, "no listen port found; please set one manually")
		}

		if rs.MTU != "" {
			if mtu, err := strconv.Atoi(strings.TrimSpace(rs.MTU)); err == nil && mtu > 0 {
				ps.MTU = mtu
			}
		}

		if rs.PrivKey == "" {
			ps.Warnings = append(ps.Warnings, "no private key found; a server cannot be imported without one")
		} else {
			ps.PrivateKey = rs.PrivKey
			key, err := wgtypes.ParseKey(rs.PrivKey)
			if err != nil {
				ps.Warnings = append(ps.Warnings, fmt.Sprintf("private key does not parse as a valid WireGuard key: %v", err))
				ps.PrivateKey = ""
			} else {
				// Always derive the public key from the private key rather
				// than trusting the exported <pubkey> blindly.
				ps.PublicKey = key.PublicKey().String()
			}
		}

		peerUUIDs := splitList(rs.Peers)
		ps.EndpointAddress = firstServerAddress(cfg.Clients, peerUUIDs)

		for _, peerUUID := range peerUUIDs {
			rc, ok := clientsByUUID[peerUUID]
			if !ok {
				ps.Warnings = append(ps.Warnings, fmt.Sprintf("referenced peer %q was not found among the parsed clients", peerUUID))
				continue
			}
			ps.Clients = append(ps.Clients, mapClient(rc))
		}

		result.Servers = append(result.Servers, ps)
	}

	return result
}

func mapClient(rc rawClient) PreviewClient {
	pc := PreviewClient{
		SourceUUID:      rc.UUID,
		Name:            rc.Name,
		Enabled:         isTruthy(rc.Enabled),
		PublicKey:       rc.PubKey,
		PresharedKey:    rc.PSK,
		AdditionalNotes: "Imported from OPNsense",
	}
	if pc.Name == "" {
		pc.Name = rc.UUID
	}
	if rc.PubKey == "" {
		pc.Warnings = append(pc.Warnings, "no public key found; this client cannot be imported without one")
	} else if _, err := wgtypes.ParseKey(rc.PubKey); err != nil {
		pc.Warnings = append(pc.Warnings, fmt.Sprintf("public key does not parse as a valid WireGuard key: %v", err))
	}

	pc.AllocatedIPs = splitList(rc.TunnelAddress)
	if len(pc.AllocatedIPs) == 0 {
		pc.Warnings = append(pc.Warnings, "no tunnel address found; please set the client's allocated address manually")
	} else if !util.ValidateAllowedIPs(pc.AllocatedIPs) {
		pc.Warnings = append(pc.Warnings, "tunnel address is not valid CIDR; please fix before importing")
	}
	// OPNsense has no separate "allowed IPs for this peer" field for
	// clients; default to the client's own allocated address(es), same as
	// wireguard-ui-multi's own "new client" default.
	pc.AllowedIPs = append([]string(nil), pc.AllocatedIPs...)

	if rc.Keepalive != "" {
		if ka, err := strconv.Atoi(strings.TrimSpace(rc.Keepalive)); err == nil && ka > 0 {
			pc.PersistentKeepalive = ka
		}
	}

	if rc.ServerAddress != "" {
		// stashed for the caller to optionally fold into the server's
		// EndpointAddress override; not part of the per-client model.
		pc.AdditionalNotes += fmt.Sprintf(" (OPNsense serveraddress: %s)", rc.ServerAddress)
	}

	return pc
}

// firstServerAddress returns the first non-empty serveraddress[:serverport]
// combination found among rc's clients, used to prefill a server's
// EndpointAddress override in the preview.
func firstServerAddress(clients []rawClient, peerUUIDs []string) string {
	wanted := make(map[string]bool, len(peerUUIDs))
	for _, u := range peerUUIDs {
		wanted[u] = true
	}
	for _, c := range clients {
		if !wanted[c.UUID] || c.ServerAddress == "" {
			continue
		}
		if c.ServerPort != "" {
			return fmt.Sprintf("%s:%s", c.ServerAddress, strings.TrimSpace(c.ServerPort))
		}
		return c.ServerAddress
	}
	return ""
}

// ToModel converts an admin-reviewed PreviewServer into the model records
// wireguard-ui-multi actually stores: a Server, its ServerSetting, and the
// Clients that belong to it. It does not touch the store itself - callers
// (the commit handler) are responsible for the actual SaveXxx calls, and
// for checking public-key collisions against clients already in the store.
func ToModel(ps PreviewServer) (model.Server, model.ServerSetting, []model.Client, error) {
	now := time.Now().UTC()

	if !util.ValidateRecordID(ps.ID) {
		return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("invalid server id %q", ps.ID)
	}
	if !util.ValidateInterfaceName(ps.Interface) {
		return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("invalid interface name %q", ps.Interface)
	}
	if !util.ValidateServerAddresses(ps.Addresses) {
		return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("invalid server addresses %v", ps.Addresses)
	}
	if ps.ListenPort <= 0 || ps.ListenPort > 65535 {
		return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("invalid listen port %d", ps.ListenPort)
	}
	if ps.PrivateKey == "" {
		return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("server %q has no private key", ps.ID)
	}
	key, err := wgtypes.ParseKey(ps.PrivateKey)
	if err != nil {
		return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("server %q private key invalid: %w", ps.ID, err)
	}

	server := model.Server{
		ID:   ps.ID,
		Name: ps.Name,
		KeyPair: &model.ServerKeypair{
			PrivateKey: key.String(),
			PublicKey:  key.PublicKey().String(),
			UpdatedAt:  now,
		},
		Interface: &model.ServerInterface{
			Name:       ps.Interface,
			Addresses:  ps.Addresses,
			ListenPort: ps.ListenPort,
			UpdatedAt:  now,
		},
	}

	settings := model.ServerSetting{
		EndpointAddress: ps.EndpointAddress,
		ConfigFilePath:  fmt.Sprintf("/etc/wireguard/%s.conf", ps.Interface),
		FirewallMark:    util.DefaultFirewallMark,
		Table:           util.DefaultTable,
		DNSServers:      ps.DNSServers,
		MTU:             ps.MTU,
		UpdatedAt:       now,
	}

	clients := make([]model.Client, 0, len(ps.Clients))
	for _, pc := range ps.Clients {
		if pc.PublicKey == "" {
			return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("client %q has no public key", pc.Name)
		}
		if _, err := wgtypes.ParseKey(pc.PublicKey); err != nil {
			return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("client %q public key invalid: %w", pc.Name, err)
		}
		if !util.ValidateAllowedIPs(pc.AllocatedIPs) {
			return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("client %q has invalid allocated IPs", pc.Name)
		}
		if !util.ValidateAllowedIPs(pc.AllowedIPs) {
			return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("client %q has invalid allowed IPs", pc.Name)
		}

		presharedKey := pc.PresharedKey
		if presharedKey != "" {
			if _, err := wgtypes.ParseKey(presharedKey); err != nil {
				return model.Server{}, model.ServerSetting{}, nil, fmt.Errorf("client %q preshared key invalid: %w", pc.Name, err)
			}
		}

		clients = append(clients, model.Client{
			ServerID:            ps.ID,
			PublicKey:           pc.PublicKey,
			PresharedKey:        presharedKey,
			Name:                pc.Name,
			Email:               pc.Email,
			AllocatedIPs:        pc.AllocatedIPs,
			AllowedIPs:          pc.AllowedIPs,
			AdditionalNotes:     pc.AdditionalNotes,
			PersistentKeepalive: pc.PersistentKeepalive,
			Enabled:             pc.Enabled,
			CreatedAt:           now,
			UpdatedAt:           now,
		})
	}

	return server, settings, clients, nil
}