package checker

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os/exec"
	"strings"
	"time"

	"github.com/intodns/backend/internal/resolver"
)

// checkDomainWhois checks domain registration and expiry via RDAP.
func checkDomainWhois(domain string, r *resolver.Resolver) Category {
	cat := Category{Name: "registration", Title: "Domain Registration"}

	cleanDomain := strings.TrimSuffix(domain, ".")

	// Get RDAP info, fall back to whois CLI
	rdap := fetchRDAP(cleanDomain)
	var whoisData *whoisInfo
	if rdap == nil {
		whoisData = fetchWhoisCLI(cleanDomain)
	}

	// 1. Domain expiry check
	if rdap != nil {
		cat.Checks = append(cat.Checks, checkDomainExpiry(cleanDomain, rdap))
	} else {
		cat.Checks = append(cat.Checks, checkDomainExpiryWhois(cleanDomain, whoisData))
	}

	// 2. Registration info
	if rdap != nil {
		cat.Checks = append(cat.Checks, checkRegistrationInfo(cleanDomain, rdap))
	} else {
		cat.Checks = append(cat.Checks, checkRegistrationInfoWhois(cleanDomain, whoisData))
	}

	return cat
}

// whoisInfo holds parsed whois CLI output.
type whoisInfo struct {
	Registered string
	Expires    string
	Registrar  string
	RegistrarURL string
	Status     string
	Contact    string
	RawLines   []string
}

func fetchWhoisCLI(domain string) *whoisInfo {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	cmd := exec.CommandContext(ctx, "whois", domain)
	out, err := cmd.Output()
	if err != nil {
		return nil
	}

	info := &whoisInfo{}
	lines := strings.Split(string(out), "\n")
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "%") || line == "" {
			continue
		}
		info.RawLines = append(info.RawLines, line)

		parts := strings.SplitN(line, ":", 2)
		if len(parts) != 2 {
			continue
		}
		key := strings.TrimSpace(strings.ToLower(parts[0]))
		val := strings.TrimSpace(parts[1])

		switch {
		case key == "expires" || key == "expiry date" || key == "registry expiry date" || key == "paid-till" || key == "expire date":
			info.Expires = val
		case key == "registered" || key == "creation date" || key == "created":
			info.Registered = val
		case key == "registrar" || key == "registrar name":
			info.Registrar = val
		case key == "registrar website" || key == "registrar url":
			info.RegistrarURL = val
		case key == "status" || key == "domain status":
			if info.Status == "" {
				info.Status = val
			} else {
				info.Status += ", " + val
			}
		case key == "contact organization" || key == "registrant organization":
			info.Contact = val
		}
	}

	return info
}

func checkDomainExpiryWhois(domain string, w *whoisInfo) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "domain-expiry", Title: "Domain Expiry"}
	defer func() { res.DurationMs = measureDuration(start) }()

	if w == nil || w.Expires == "" {
		res.Status = StatusInfo
		res.Message = "Could not retrieve domain expiry information"
		return res
	}

	expiry, err := parseFlexDate(w.Expires)
	if err != nil {
		res.Status = StatusInfo
		res.Message = fmt.Sprintf("Domain expires: %s", w.Expires)
		return res
	}

	daysLeft := int(time.Until(expiry).Hours() / 24)

	switch {
	case daysLeft < 0:
		res.Status = StatusFail
		res.Message = fmt.Sprintf("Domain %s EXPIRED %d days ago (%s)! Renew immediately.", domain, -daysLeft, expiry.Format("2006-01-02"))
	case daysLeft <= 15:
		res.Status = StatusFail
		res.Message = fmt.Sprintf("Domain %s expires in %d days (%s). Renew urgently!", domain, daysLeft, expiry.Format("2006-01-02"))
	case daysLeft <= 30:
		res.Status = StatusWarn
		res.Message = fmt.Sprintf("Domain %s expires in %d days (%s). Consider renewing soon.", domain, daysLeft, expiry.Format("2006-01-02"))
	default:
		res.Status = StatusPass
		res.Message = fmt.Sprintf("Domain %s expires in %d days (%s)", domain, daysLeft, expiry.Format("2006-01-02"))
	}

	if w.Registered != "" {
		res.Details = append(res.Details, fmt.Sprintf("Registered: %s", w.Registered))
	}
	res.Details = append(res.Details, fmt.Sprintf("Expires: %s (%d days left)", expiry.Format("2006-01-02"), daysLeft))
	return res
}

func checkRegistrationInfoWhois(domain string, w *whoisInfo) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "domain-registrar", Title: "Registrar"}
	defer func() { res.DurationMs = measureDuration(start) }()

	if w == nil {
		res.Status = StatusInfo
		res.Message = "Could not retrieve registrar information"
		return res
	}

	res.Status = StatusInfo
	if w.Registrar != "" {
		res.Message = fmt.Sprintf("Registered through %s", w.Registrar)
		res.Details = append(res.Details, fmt.Sprintf("Registrar: %s", w.Registrar))
	} else {
		res.Message = "Registrar information not available"
	}

	if w.RegistrarURL != "" {
		res.Details = append(res.Details, fmt.Sprintf("Registrar website: %s", w.RegistrarURL))
	}
	if w.Status != "" {
		res.Details = append(res.Details, fmt.Sprintf("Status: %s", w.Status))
	}
	if w.Contact != "" {
		res.Details = append(res.Details, fmt.Sprintf("Registrant: %s", w.Contact))
	}

	return res
}

func parseFlexDate(s string) (time.Time, error) {
	layouts := []string{
		time.RFC3339,
		"2006-01-02T15:04:05Z",
		"2006-01-02",
		"02-Jan-2006",
		"2006.01.02",
		"02/01/2006",
		"01/02/2006",
		"2006-01-02 15:04:05",
	}
	for _, layout := range layouts {
		t, err := time.Parse(layout, s)
		if err == nil {
			return t, nil
		}
	}
	return time.Time{}, fmt.Errorf("cannot parse date: %s", s)
}

type rdapResponse struct {
	Handle     string       `json:"handle"`
	Name       string       `json:"ldhName"`
	Status     []string     `json:"status"`
	Events     []rdapEvent  `json:"events"`
	Entities   []rdapEntity `json:"entities"`
	Nameservers []rdapNS    `json:"nameservers"`
}

type rdapEvent struct {
	Action string `json:"eventAction"`
	Date   string `json:"eventDate"`
}

type rdapEntity struct {
	Roles    []string       `json:"roles"`
	Handle   string         `json:"handle"`
	VcardArr []interface{}  `json:"vcardArray"`
	Entities []rdapEntity   `json:"entities"`
	PublicIDs []rdapPublicID `json:"publicIds"`
}

type rdapPublicID struct {
	Type       string `json:"type"`
	Identifier string `json:"identifier"`
}

type rdapNS struct {
	LdhName string `json:"ldhName"`
}

func fetchRDAP(domain string) *rdapResponse {
	// Determine RDAP server based on TLD
	tld := domain
	if idx := strings.LastIndex(domain, "."); idx >= 0 {
		tld = domain[idx+1:]
	}

	// Try IANA bootstrap first, then known servers
	urls := []string{
		fmt.Sprintf("https://rdap.org/domain/%s", domain),
	}

	// Add known TLD-specific RDAP servers
	switch strings.ToLower(tld) {
	case "com", "net":
		urls = append([]string{fmt.Sprintf("https://rdap.verisign.com/com/v1/domain/%s", domain)}, urls...)
	case "org":
		urls = append([]string{fmt.Sprintf("https://rdap.org/domain/%s", domain)}, urls...)
	case "lt":
		urls = append([]string{fmt.Sprintf("https://rdap.domreg.lt/domain/%s", domain)}, urls...)
	case "eu":
		urls = append([]string{fmt.Sprintf("https://rdap.eu/domain/%s", domain)}, urls...)
	case "io":
		urls = append([]string{fmt.Sprintf("https://rdap.nic.io/domain/%s", domain)}, urls...)
	case "dev":
		urls = append([]string{fmt.Sprintf("https://rdap.nic.google/domain/%s", domain)}, urls...)
	}

	client := &http.Client{Timeout: 5 * time.Second}

	for _, url := range urls {
		req, err := http.NewRequest("GET", url, nil)
		if err != nil {
			continue
		}
		req.Header.Set("Accept", "application/rdap+json")

		resp, err := client.Do(req)
		if err != nil {
			continue
		}
		defer resp.Body.Close()

		if resp.StatusCode != 200 {
			continue
		}

		body, err := io.ReadAll(io.LimitReader(resp.Body, 100*1024))
		if err != nil {
			continue
		}

		var rdap rdapResponse
		if err := json.Unmarshal(body, &rdap); err != nil {
			continue
		}

		return &rdap
	}

	return nil
}

func checkDomainExpiry(domain string, rdap *rdapResponse) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "domain-expiry", Title: "Domain Expiry"}
	defer func() { res.DurationMs = measureDuration(start) }()

	if rdap == nil {
		res.Status = StatusInfo
		res.Message = "Could not retrieve domain registration information"
		return res
	}

	var expiryDate, registrationDate, lastChanged string
	for _, event := range rdap.Events {
		switch event.Action {
		case "expiration":
			expiryDate = event.Date
		case "registration":
			registrationDate = event.Date
		case "last changed", "last update of RDAP database":
			if lastChanged == "" || event.Action == "last changed" {
				lastChanged = event.Date
			}
		}
	}

	if expiryDate == "" {
		res.Status = StatusInfo
		res.Message = "Domain expiry date not available"
		if registrationDate != "" {
			res.Details = append(res.Details, fmt.Sprintf("Registered: %s", formatDate(registrationDate)))
		}
		return res
	}

	expiry, err := time.Parse(time.RFC3339, expiryDate)
	if err != nil {
		// Try other formats
		for _, layout := range []string{"2006-01-02T15:04:05Z", "2006-01-02", "2006-01-02 15:04:05"} {
			expiry, err = time.Parse(layout, expiryDate)
			if err == nil {
				break
			}
		}
	}
	if err != nil {
		res.Status = StatusInfo
		res.Message = fmt.Sprintf("Domain expires: %s (could not parse date)", expiryDate)
		return res
	}

	daysLeft := int(time.Until(expiry).Hours() / 24)

	switch {
	case daysLeft < 0:
		res.Status = StatusFail
		res.Message = fmt.Sprintf("Domain %s EXPIRED %d days ago (%s)! Renew immediately or risk losing the domain.", domain, -daysLeft, formatDate(expiryDate))
	case daysLeft <= 15:
		res.Status = StatusFail
		res.Message = fmt.Sprintf("Domain %s expires in %d days (%s). Renew urgently!", domain, daysLeft, formatDate(expiryDate))
	case daysLeft <= 30:
		res.Status = StatusWarn
		res.Message = fmt.Sprintf("Domain %s expires in %d days (%s). Consider renewing soon.", domain, daysLeft, formatDate(expiryDate))
	default:
		res.Status = StatusPass
		res.Message = fmt.Sprintf("Domain %s expires in %d days (%s)", domain, daysLeft, formatDate(expiryDate))
	}

	if registrationDate != "" {
		res.Details = append(res.Details, fmt.Sprintf("Registered: %s", formatDate(registrationDate)))
	}
	res.Details = append(res.Details, fmt.Sprintf("Expires: %s (%d days left)", formatDate(expiryDate), daysLeft))
	if lastChanged != "" {
		res.Details = append(res.Details, fmt.Sprintf("Last changed: %s", formatDate(lastChanged)))
	}

	return res
}

func checkRegistrationInfo(domain string, rdap *rdapResponse) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "domain-registrar", Title: "Registrar"}
	defer func() { res.DurationMs = measureDuration(start) }()

	if rdap == nil {
		res.Status = StatusInfo
		res.Message = "Could not retrieve registrar information"
		return res
	}

	// Find registrar entity
	var registrarName string
	var registrarHandle string
	for _, entity := range rdap.Entities {
		for _, role := range entity.Roles {
			if strings.ToLower(role) == "registrar" {
				registrarHandle = entity.Handle
				// Try to extract name from vcard
				registrarName = extractVcardName(entity.VcardArr)
				if registrarName == "" {
					registrarName = entity.Handle
				}
			}
		}
	}

	// Domain status
	if len(rdap.Status) > 0 {
		res.Details = append(res.Details, fmt.Sprintf("Status: %s", strings.Join(rdap.Status, ", ")))
	}

	if registrarName != "" {
		res.Status = StatusInfo
		res.Message = fmt.Sprintf("Registered through %s", registrarName)
		if registrarHandle != "" && registrarHandle != registrarName {
			res.Details = append(res.Details, fmt.Sprintf("Registrar: %s (%s)", registrarName, registrarHandle))
		} else {
			res.Details = append(res.Details, fmt.Sprintf("Registrar: %s", registrarName))
		}
	} else {
		res.Status = StatusInfo
		res.Message = "Registrar information not available"
	}

	// Nameservers from RDAP
	if len(rdap.Nameservers) > 0 {
		var nsNames []string
		for _, ns := range rdap.Nameservers {
			nsNames = append(nsNames, ns.LdhName)
		}
		res.Details = append(res.Details, fmt.Sprintf("Nameservers: %s", strings.Join(nsNames, ", ")))
	}

	return res
}

func extractVcardName(vcardArr []interface{}) string {
	if len(vcardArr) < 2 {
		return ""
	}
	entries, ok := vcardArr[1].([]interface{})
	if !ok {
		return ""
	}
	for _, entry := range entries {
		arr, ok := entry.([]interface{})
		if !ok || len(arr) < 4 {
			continue
		}
		propName, ok := arr[0].(string)
		if !ok {
			continue
		}
		if propName == "fn" || propName == "org" {
			if val, ok := arr[3].(string); ok && val != "" {
				return val
			}
		}
	}
	return ""
}

func formatDate(dateStr string) string {
	t, err := time.Parse(time.RFC3339, dateStr)
	if err != nil {
		for _, layout := range []string{"2006-01-02T15:04:05Z", "2006-01-02"} {
			t, err = time.Parse(layout, dateStr)
			if err == nil {
				break
			}
		}
	}
	if err != nil {
		return dateStr
	}
	return t.Format("2006-01-02")
}