package whois

import (
	"context"
	"fmt"
	"io"
	"net"
	"net/url"
	"strconv"
	"strings"
	"sync"
	"time"

	"golang.org/x/net/proxy"
)

const (
	defWhoisServer      = "whois.iana.org"
	defWhoisPort        = "43"
	defTimeout          = 30 * time.Second
	defReferralMaxDepth = 1
	asnPrefix           = "AS"
)

var DefaultClient = NewClient()
var defaultWhoisMap = map[string]string{}
var whoisNegativeCache sync.Map

type Client struct {
	extCache         map[string]string
	mu               sync.Mutex
	dialer           proxy.Dialer
	timeout          time.Duration
	elapsed          time.Duration
	negativeCacheTTL time.Duration
}

type rawQueryResult struct {
	Data    string
	Server  string
	Charset string
}

type rawWhoisStep struct {
	Data    string
	Server  string
	Charset string
}

type negativeCacheEntry struct {
	Result   *Result
	Domain   string
	Code     ErrorCode
	Server   string
	Reason   string
	ExpireAt time.Time
}

func NewClient() *Client {
	return &Client{
		dialer:           &net.Dialer{Timeout: defTimeout},
		extCache:         make(map[string]string),
		timeout:          defTimeout,
		negativeCacheTTL: 0,
	}
}

func (c *Client) SetDialer(d proxy.Dialer) *Client   { c.dialer = d; return c }
func (c *Client) SetTimeout(t time.Duration) *Client { c.timeout = t; return c }
func (c *Client) SetNegativeCacheTTL(ttl time.Duration) *Client {
	c.negativeCacheTTL = ttl
	return c
}

func (c *Client) ClearNegativeCache(keys ...string) {
	clearNegativeCache(keys...)
}

func (c *Client) Whois(domain string, servers ...string) (Result, error) {
	return c.WhoisContext(context.Background(), domain, servers...)
}

func (c *Client) WhoisContext(ctx context.Context, domain string, servers ...string) (Result, error) {
	opt := QueryOptions{Level: QueryAuto, ReferralMaxDepth: defReferralMaxDepth}
	if len(servers) > 0 {
		opt.OverrideServers = normalizeServerList(servers)
		if len(opt.OverrideServers) > 0 {
			opt.OverrideServer = opt.OverrideServers[0]
		}
	}
	return c.WhoisWithOptionsContext(ctx, domain, opt)
}

func (c *Client) WhoisWithOptions(domain string, opt QueryOptions) (Result, error) {
	return c.WhoisWithOptionsContext(context.Background(), domain, opt)
}

func (c *Client) WhoisWithOptionsContext(ctx context.Context, domain string, opt QueryOptions) (Result, error) {
	normalizedDomain, err := normalizeQueryDomainInput(domain)
	if err != nil {
		return Result{}, err
	}
	domain = normalizedDomain

	cacheTTL := c.effectiveNegativeCacheTTL(opt)
	cacheKey := ""
	if cacheTTL > 0 && !hasOverrideWhoisServers(opt) {
		cacheKey = negativeCacheKey(domain, opt)
		if cachedResult, cachedErr, ok := loadNegativeCache(cacheKey, time.Now()); ok {
			if cachedErr != nil {
				return Result{}, cachedErr
			}
			return cachedResult, nil
		}
	}

	raw, err := c.queryRawWithLevelContext(ctx, domain, opt)
	if err != nil {
		if cacheKey != "" && IsCode(err, ErrorCodeNoWhoisServer) {
			storeNegativeCache(cacheKey, cacheTTL, negativeCacheEntry{
				Domain:   domain,
				Code:     ErrorCodeNoWhoisServer,
				Server:   "",
				Reason:   "registry whois server not found",
				ExpireAt: time.Now().Add(cacheTTL),
			})
		}
		return Result{}, err
	}
	out, err := parse(domain, raw.Data)
	if err != nil {
		return Result{}, err
	}
	out.meta = buildResultMeta(out, "whois", raw.Server)
	out.meta.Charset = raw.Charset
	if cacheKey != "" && out.meta.ReasonCode == ErrorCodeNotFound {
		resultCopy := cloneResult(out)
		storeNegativeCache(cacheKey, cacheTTL, negativeCacheEntry{
			Result:   &resultCopy,
			Domain:   domain,
			Code:     ErrorCodeNotFound,
			Server:   out.meta.Server,
			Reason:   out.meta.Reason,
			ExpireAt: time.Now().Add(cacheTTL),
		})
	}
	return out, nil
}

func (c *Client) queryRawWithLevel(domain string, opt QueryOptions) (string, error) {
	out, err := c.queryRawWithLevelContext(context.Background(), domain, opt)
	if err != nil {
		return "", err
	}
	return out.Data, nil
}

func (c *Client) queryRawWithLevelContext(ctx context.Context, domain string, opt QueryOptions) (rawQueryResult, error) {
	if ctx == nil {
		ctx = context.Background()
	}
	normalizedDomain, err := normalizeQueryDomainInput(domain)
	if err != nil {
		return rawQueryResult{}, err
	}
	domain = normalizedDomain

	overrideServers := normalizeServerList(opt.OverrideServers)
	if len(overrideServers) == 0 && opt.OverrideServer != "" {
		overrideServers = []string{opt.OverrideServer}
	}
	if len(overrideServers) > 0 {
		return c.rawQueryFallbackContext(ctx, domain, overrideServers)
	}

	registryServer, registryPort, err := c.resolveRegistryServerContext(ctx, domain)
	if err != nil {
		return rawQueryResult{}, err
	}
	referralDepth := effectiveReferralMaxDepth(opt.ReferralMaxDepth)
	chain, err := c.queryWhoisChainContext(ctx, domain, registryServer, registryPort, referralDepth)
	if err != nil {
		return rawQueryResult{}, err
	}
	if len(chain) == 0 {
		return rawQueryResult{}, newWhoisError(ErrorCodeEmptyResponse, domain, net.JoinHostPort(registryServer, registryPort), "empty whois response", ErrEmptyResponse)
	}

	switch opt.Level {
	case QueryRegistryOnly:
		first := chain[0]
		return rawQueryResult{Data: first.Data, Server: first.Server, Charset: first.Charset}, nil
	case QueryRegistrarOnly:
		if len(chain) == 1 {
			first := chain[0]
			return rawQueryResult{Data: first.Data, Server: first.Server, Charset: first.Charset}, nil
		}
		last := chain[len(chain)-1]
		return rawQueryResult{Data: last.Data, Server: last.Server, Charset: chainCombinedCharset(chain)}, nil
	case QueryBoth:
		if len(chain) == 1 {
			first := chain[0]
			return rawQueryResult{Data: first.Data, Server: first.Server, Charset: first.Charset}, nil
		}
		return rawQueryResult{
			Data:    formatWhoisChainData(chain, true),
			Server:  chainServerPath(chain),
			Charset: chainCombinedCharset(chain),
		}, nil
	case QueryAuto:
		fallthrough
	default:
		if len(chain) == 1 {
			first := chain[0]
			return rawQueryResult{Data: first.Data, Server: first.Server, Charset: first.Charset}, nil
		}
		return rawQueryResult{
			Data:    formatWhoisChainData(chain, false),
			Server:  chainServerPath(chain),
			Charset: chainCombinedCharset(chain),
		}, nil
	}
}

func (c *Client) resolveRegistryServer(domain string) (string, string, error) {
	return c.resolveRegistryServerContext(context.Background(), domain)
}

func (c *Client) resolveRegistryServerContext(ctx context.Context, domain string) (string, string, error) {
	if v, ok := defaultWhoisMap[getExtension(domain)]; ok {
		if host, port := normalizeWhoisServer(v); host != "" {
			return host, port, nil
		}
	}
	ext := getExtension(domain)

	c.mu.Lock()
	cache, ok := c.extCache[ext]
	c.mu.Unlock()
	if ok {
		if host, port, err := net.SplitHostPort(cache); err == nil {
			return host, port, nil
		}
		if host, port := normalizeWhoisServer(cache); host != "" {
			return host, port, nil
		}
	}

	result, _, err := c.rawQueryContext(ctx, ext, defWhoisServer, defWhoisPort)
	if err != nil {
		return "", "", fmt.Errorf("whois: query for whois server failed: %w", err)
	}
	server, port := getServer(result)
	if server == "" {
		return "", "", newWhoisError(ErrorCodeNoWhoisServer, domain, net.JoinHostPort(defWhoisServer, defWhoisPort), "registry whois server not found", ErrNoWhoisServer)
	}
	c.mu.Lock()
	c.extCache[ext] = net.JoinHostPort(server, port)
	c.mu.Unlock()
	return server, port, nil
}

func (c *Client) rawQueryFallback(domain string, servers []string) (string, error) {
	out, err := c.rawQueryFallbackContext(context.Background(), domain, servers)
	if err != nil {
		return "", err
	}
	return out.Data, nil
}

func (c *Client) rawQuery(domain, server, port string) (string, error) {
	data, _, err := c.rawQueryContext(context.Background(), domain, server, port)
	return data, err
}

func (c *Client) rawQueryFallbackContext(ctx context.Context, domain string, servers []string) (rawQueryResult, error) {
	if ctx == nil {
		ctx = context.Background()
	}
	var lastErr error
	for _, server := range normalizeServerList(servers) {
		host, port := normalizeWhoisServer(server)
		if host == "" {
			continue
		}
		data, charset, err := c.rawQueryContext(ctx, domain, host, port)
		if err == nil {
			return rawQueryResult{
				Data:    data,
				Server:  net.JoinHostPort(host, port),
				Charset: charset,
			}, nil
		}
		lastErr = fmt.Errorf("%s:%s: %w", host, port, err)
	}
	if lastErr == nil {
		return rawQueryResult{}, newWhoisError(ErrorCodeNoWhoisServer, domain, "", "no valid whois server", ErrNoWhoisServer)
	}
	return rawQueryResult{}, fmt.Errorf("whois: all whois servers failed: %w", lastErr)
}

func (c *Client) rawQueryContext(ctx context.Context, domain, server, port string) (string, string, error) {
	if ctx == nil {
		ctx = context.Background()
	}
	start := time.Now()
	queryText := domain
	if server == "whois.arin.net" {
		if IsASN(domain) {
			queryText = "a + " + domain
		} else {
			queryText = "n + " + domain
		}
	}
	serverAddr := net.JoinHostPort(server, port)
	conn, err := c.dialContext(ctx, "tcp", serverAddr)
	if err != nil {
		if ctx.Err() != nil {
			return "", "", ctx.Err()
		}
		return "", "", wrapNetworkError(domain, serverAddr, err, "connect failed")
	}
	defer conn.Close()

	cancelWatchDone := make(chan struct{})
	defer close(cancelWatchDone)
	go func() {
		select {
		case <-ctx.Done():
			_ = conn.SetDeadline(time.Now())
			_ = conn.Close()
		case <-cancelWatchDone:
		}
	}()

	if err := conn.SetWriteDeadline(c.effectiveDeadline(ctx)); err != nil {
		return "", "", wrapNetworkError(domain, serverAddr, err, "set write deadline failed")
	}
	if _, err = conn.Write([]byte(queryText + "\r\n")); err != nil {
		if ctx.Err() != nil {
			return "", "", ctx.Err()
		}
		return "", "", wrapNetworkError(domain, serverAddr, err, "write failed")
	}
	if err := conn.SetReadDeadline(c.effectiveDeadline(ctx)); err != nil {
		return "", "", wrapNetworkError(domain, serverAddr, err, "set read deadline failed")
	}
	buf, err := io.ReadAll(conn)
	if err != nil {
		if ctx.Err() != nil {
			return "", "", ctx.Err()
		}
		return "", "", wrapNetworkError(domain, serverAddr, err, "read failed")
	}

	decoded, charset := decodeWhoisPayload(buf)
	data := strings.TrimSpace(decoded)
	if data == "" {
		return "", charset, newWhoisError(ErrorCodeEmptyResponse, domain, serverAddr, "empty whois response", ErrEmptyResponse)
	}
	data = fmt.Sprintf("%s\n\n%% Query time: %d msec\n%% WHEN: %s\n",
		data, time.Since(start).Milliseconds(), start.Format("Mon Jan 02 15:04:05 MST 2006"))
	return data, charset, nil
}

func (c *Client) dialContext(ctx context.Context, network, address string) (net.Conn, error) {
	d := c.dialer
	if d == nil {
		d = &net.Dialer{Timeout: c.timeout}
	}
	if cd, ok := d.(interface {
		DialContext(context.Context, string, string) (net.Conn, error)
	}); ok {
		return cd.DialContext(ctx, network, address)
	}

	type dialRet struct {
		conn net.Conn
		err  error
	}
	ch := make(chan dialRet)
	abandon := make(chan struct{})
	go func() {
		conn, err := d.Dial(network, address)
		select {
		case <-abandon:
			if conn != nil {
				_ = conn.Close()
			}
		case ch <- dialRet{conn: conn, err: err}:
		}
	}()

	select {
	case <-ctx.Done():
		close(abandon)
		return nil, ctx.Err()
	case ret := <-ch:
		return ret.conn, ret.err
	}
}

func (c *Client) effectiveDeadline(ctx context.Context) time.Time {
	timeout := c.timeout
	if timeout <= 0 {
		timeout = defTimeout
	}
	deadline := time.Now().Add(timeout)
	if d, ok := ctx.Deadline(); ok && d.Before(deadline) {
		return d
	}
	return deadline
}

func combineCharset(a, b string) string {
	a = strings.TrimSpace(strings.ToLower(a))
	b = strings.TrimSpace(strings.ToLower(b))
	switch {
	case a == "" && b == "":
		return ""
	case a == "":
		return b
	case b == "":
		return a
	case a == b:
		return a
	default:
		return "mixed"
	}
}

func getExtension(domain string) string {
	ext := domain
	if net.ParseIP(domain) == nil {
		parts := strings.Split(domain, ".")
		ext = parts[len(parts)-1]
	}
	if strings.Contains(ext, "/") {
		ext = strings.Split(ext, "/")[0]
	}
	return ext
}

func getServer(data string) (string, string) {
	lines := strings.Split(data, "\n")
	for _, raw := range lines {
		line := strings.TrimSpace(raw)
		if line == "" {
			continue
		}
		key, val, ok := splitKV(line)
		if !ok {
			continue
		}
		switch strings.ToLower(strings.TrimSpace(key)) {
		case "registrar whois server", "whois server", "whois", "referralserver", "refer":
			if host, port := normalizeWhoisServer(val); host != "" {
				return host, port
			}
		}
	}
	return "", ""
}

func normalizeServerList(servers []string) []string {
	out := make([]string, 0, len(servers))
	seen := make(map[string]struct{}, len(servers))
	for _, s := range servers {
		s = strings.TrimSpace(s)
		if s == "" {
			continue
		}
		k := strings.ToLower(s)
		if _, ok := seen[k]; ok {
			continue
		}
		seen[k] = struct{}{}
		out = append(out, s)
	}
	return out
}

func normalizeWhoisServer(raw string) (string, string) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return "", ""
	}
	raw = strings.Trim(raw, "<>")
	if fields := strings.Fields(raw); len(fields) > 0 {
		raw = fields[0]
	}

	if strings.Contains(raw, "://") {
		if u, err := url.Parse(raw); err == nil && u.Host != "" {
			raw = u.Host
		}
	}

	raw = strings.TrimPrefix(raw, "whois:")
	raw = strings.TrimPrefix(raw, "rwhois:")
	raw = strings.Trim(raw, "/")
	if raw == "" {
		return "", ""
	}

	if host, port, err := net.SplitHostPort(raw); err == nil {
		host = strings.TrimSpace(strings.ToLower(host))
		port = strings.TrimSpace(port)
		if host != "" && port != "" {
			return host, port
		}
	}

	if strings.Count(raw, ":") == 1 {
		v := strings.SplitN(raw, ":", 2)
		host := strings.TrimSpace(strings.ToLower(v[0]))
		port := strings.TrimSpace(v[1])
		if host != "" && port != "" {
			if _, err := strconv.Atoi(port); err == nil {
				return host, port
			}
		}
	}

	return strings.ToLower(raw), defWhoisPort
}

func effectiveReferralMaxDepth(v int) int {
	if v < 0 {
		return 0
	}
	if v == 0 {
		return defReferralMaxDepth
	}
	if v > 16 {
		return 16
	}
	return v
}

func (c *Client) queryWhoisChainContext(ctx context.Context, domain, server, port string, referralMaxDepth int) ([]rawWhoisStep, error) {
	steps := make([]rawWhoisStep, 0, 2)
	visited := make(map[string]struct{}, referralMaxDepth+1)
	host := server
	p := port

	for {
		addr := strings.ToLower(net.JoinHostPort(host, p))
		if _, seen := visited[addr]; seen {
			break
		}
		visited[addr] = struct{}{}

		data, charset, err := c.rawQueryContext(ctx, domain, host, p)
		if err != nil {
			if len(steps) == 0 {
				return nil, err
			}
			return steps, nil
		}
		steps = append(steps, rawWhoisStep{
			Data:    data,
			Server:  net.JoinHostPort(host, p),
			Charset: charset,
		})

		if len(steps)-1 >= referralMaxDepth {
			break
		}
		refHost, refPort := getServer(data)
		if refHost == "" {
			break
		}
		refAddr := strings.ToLower(net.JoinHostPort(refHost, refPort))
		if _, seen := visited[refAddr]; seen {
			break
		}
		host, p = refHost, refPort
	}
	return steps, nil
}

func formatWhoisChainData(chain []rawWhoisStep, withRegistrarMarker bool) string {
	if len(chain) == 0 {
		return ""
	}
	if len(chain) == 1 {
		return chain[0].Data
	}
	parts := make([]string, 0, len(chain))
	parts = append(parts, chain[0].Data)
	for i := 1; i < len(chain); i++ {
		if withRegistrarMarker {
			if i == 1 {
				parts = append(parts, "----- REGISTRAR WHOIS -----")
			} else {
				parts = append(parts, fmt.Sprintf("----- REFERRAL WHOIS #%d -----", i+1))
			}
		}
		parts = append(parts, chain[i].Data)
	}
	sep := "\n"
	if withRegistrarMarker {
		sep = "\n\n"
	}
	return strings.Join(parts, sep)
}

func chainServerPath(chain []rawWhoisStep) string {
	if len(chain) == 0 {
		return ""
	}
	parts := make([]string, 0, len(chain))
	for _, step := range chain {
		s := strings.TrimSpace(step.Server)
		if s == "" {
			continue
		}
		parts = append(parts, s)
	}
	return strings.Join(parts, " -> ")
}

func chainCombinedCharset(chain []rawWhoisStep) string {
	charset := ""
	for _, step := range chain {
		charset = combineCharset(charset, step.Charset)
	}
	return charset
}

func (c *Client) effectiveNegativeCacheTTL(opt QueryOptions) time.Duration {
	if opt.NegativeCacheTTL > 0 {
		return opt.NegativeCacheTTL
	}
	if opt.NegativeCacheTTL < 0 {
		return 0
	}
	if c == nil {
		return 0
	}
	if c.negativeCacheTTL > 0 {
		return c.negativeCacheTTL
	}
	return 0
}

func hasOverrideWhoisServers(opt QueryOptions) bool {
	if strings.TrimSpace(opt.OverrideServer) != "" {
		return true
	}
	for _, s := range opt.OverrideServers {
		if strings.TrimSpace(s) != "" {
			return true
		}
	}
	return false
}

func negativeCacheKey(domain string, opt QueryOptions) string {
	return fmt.Sprintf("whois-neg|level=%d|domain=%s", opt.Level, strings.ToLower(strings.TrimSpace(domain)))
}

func loadNegativeCache(key string, now time.Time) (Result, error, bool) {
	v, ok := whoisNegativeCache.Load(key)
	if !ok {
		return Result{}, nil, false
	}
	entry, ok := v.(negativeCacheEntry)
	if !ok {
		whoisNegativeCache.Delete(key)
		return Result{}, nil, false
	}
	if !entry.ExpireAt.After(now) {
		whoisNegativeCache.Delete(key)
		return Result{}, nil, false
	}
	if entry.Result != nil {
		return cloneResult(*entry.Result), nil, true
	}
	cause := ErrNoWhoisServer
	if entry.Code == ErrorCodeNotFound {
		cause = ErrNotFound
	}
	return Result{}, newWhoisError(entry.Code, entry.Domain, entry.Server, entry.Reason, cause), true
}

func storeNegativeCache(key string, ttl time.Duration, entry negativeCacheEntry) {
	if ttl <= 0 {
		return
	}
	if entry.ExpireAt.IsZero() {
		entry.ExpireAt = time.Now().Add(ttl)
	}
	if entry.Result != nil {
		r := cloneResult(*entry.Result)
		entry.Result = &r
	}
	whoisNegativeCache.Store(key, entry)
}

func clearNegativeCache(keys ...string) {
	if len(keys) == 0 {
		whoisNegativeCache.Range(func(k, _ interface{}) bool {
			whoisNegativeCache.Delete(k)
			return true
		})
		return
	}
	for _, key := range keys {
		key = strings.TrimSpace(key)
		if key == "" {
			continue
		}
		whoisNegativeCache.Delete(key)
	}
}

func cloneResult(in Result) Result {
	out := in
	out.statusRaw = append([]string(nil), in.statusRaw...)
	out.nsServers = append([]string(nil), in.nsServers...)
	out.nsIps = append([]string(nil), in.nsIps...)
	return out
}

func IsASN(s string) bool {
	s = strings.ToUpper(s)
	s = strings.TrimPrefix(s, asnPrefix)
	_, err := strconv.Atoi(s)
	return err == nil
}