package checker

import (
	"fmt"
	"strings"
	"time"

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

// checkSOA runs the 7 SOA checks.
func checkSOA(domain string, r *resolver.Resolver) Category {
	cat := Category{Name: "soa", Title: "SOA Record"}

	domain = dns.Fqdn(domain)

	// Get the SOA record.
	resp, err := r.Query(domain, "8.8.8.8", dns.TypeSOA)
	if err != nil || resp == nil {
		cat.Checks = append(cat.Checks, CheckResult{
			ID: "soa-present", Title: "SOA Present",
			Status: StatusFail, Message: fmt.Sprintf("Failed to query SOA: %v", err),
		})
		return cat
	}

	var soa *dns.SOA
	for _, rr := range resp.Answer {
		if s, ok := rr.(*dns.SOA); ok {
			soa = s
			break
		}
	}

	// 1. soa-present
	cat.Checks = append(cat.Checks, checkSOAPresent(soa))

	if soa == nil {
		// Remaining checks require a SOA record.
		return cat
	}

	// Get NS list for serial consistency check.
	nsResp, _ := r.Query(domain, "8.8.8.8", dns.TypeNS)
	var nsNames []string
	if nsResp != nil {
		for _, rr := range nsResp.Answer {
			if ns, ok := rr.(*dns.NS); ok {
				nsNames = appendUniqLower(nsNames, ns.Ns)
			}
		}
	}

	// 2. soa-serial-consistent
	cat.Checks = append(cat.Checks, checkSOASerialConsistent(domain, nsNames, r))

	// 3. soa-mname-valid
	cat.Checks = append(cat.Checks, checkSOAMnameValid(soa, r))

	// 4. soa-rname-valid
	cat.Checks = append(cat.Checks, checkSOARnameValid(soa))

	// 5. soa-refresh
	cat.Checks = append(cat.Checks, checkSOARefresh(soa))

	// 6. soa-retry
	cat.Checks = append(cat.Checks, checkSOARetry(soa))

	// 7. soa-expire
	cat.Checks = append(cat.Checks, checkSOAExpire(soa))

	return cat
}

func checkSOAPresent(soa *dns.SOA) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-present", Title: "SOA Present"}
	defer func() { res.DurationMs = measureDuration(start) }()

	if soa == nil {
		res.Status = StatusFail
		res.Message = "No SOA record found"
		return res
	}

	res.Status = StatusPass
	res.Message = "SOA record found"
	res.Details = []string{
		fmt.Sprintf("MNAME: %s", soa.Ns),
		fmt.Sprintf("RNAME: %s", soa.Mbox),
		fmt.Sprintf("Serial: %d", soa.Serial),
		fmt.Sprintf("Refresh: %d", soa.Refresh),
		fmt.Sprintf("Retry: %d", soa.Retry),
		fmt.Sprintf("Expire: %d", soa.Expire),
		fmt.Sprintf("Minimum TTL: %d", soa.Minttl),
	}
	return res
}

func checkSOASerialConsistent(domain string, nsNames []string, r *resolver.Resolver) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-serial-consistent", Title: "SOA Serial Consistency"}
	defer func() { res.DurationMs = measureDuration(start) }()

	if len(nsNames) == 0 {
		res.Status = StatusWarn
		res.Message = "No nameservers to compare serials"
		return res
	}

	serials := make(map[uint32][]string)
	for _, ns := range nsNames {
		ips := resolveNS(ns, r)
		for _, ip := range ips {
			resp, err := r.QueryNoRecurse(domain, ip, dns.TypeSOA)
			if err != nil {
				res.Details = append(res.Details, fmt.Sprintf("%s (%s): error", ns, ip))
				continue
			}
			for _, rr := range resp.Answer {
				if soa, ok := rr.(*dns.SOA); ok {
					serials[soa.Serial] = append(serials[soa.Serial], fmt.Sprintf("%s (%s)", ns, ip))
					res.Details = append(res.Details, fmt.Sprintf("%s (%s): serial %d", ns, ip, soa.Serial))
				}
			}
			break // only first IP per NS
		}
	}

	if len(serials) == 0 {
		res.Status = StatusWarn
		res.Message = "Could not retrieve SOA serial from any nameserver"
	} else if len(serials) == 1 {
		res.Status = StatusPass
		for serial := range serials {
			res.Message = fmt.Sprintf("All nameservers have consistent serial %d", serial)
		}
	} else {
		res.Status = StatusFail
		res.Message = fmt.Sprintf("Inconsistent SOA serials across nameservers (%d different values)", len(serials))
	}
	return res
}

func checkSOAMnameValid(soa *dns.SOA, r *resolver.Resolver) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-mname-valid", Title: "SOA MNAME Valid"}
	defer func() { res.DurationMs = measureDuration(start) }()

	mname := soa.Ns
	if mname == "" || mname == "." {
		res.Status = StatusFail
		res.Message = "MNAME is empty or root"
		return res
	}

	res.Details = append(res.Details, fmt.Sprintf("MNAME: %s", mname))

	// Check if it resolves to an A record.
	resp, err := r.Query(mname, "8.8.8.8", dns.TypeA)
	if err != nil {
		res.Status = StatusWarn
		res.Message = fmt.Sprintf("MNAME %s could not be resolved", mname)
		return res
	}

	hasA := false
	for _, rr := range resp.Answer {
		if a, ok := rr.(*dns.A); ok {
			hasA = true
			res.Details = append(res.Details, fmt.Sprintf("Resolves to: %s", a.A.String()))
		}
	}

	if hasA {
		res.Status = StatusPass
		res.Message = fmt.Sprintf("MNAME %s is valid and resolves", mname)
	} else {
		res.Status = StatusWarn
		res.Message = fmt.Sprintf("MNAME %s does not have an A record", mname)
	}
	return res
}

func checkSOARnameValid(soa *dns.SOA) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-rname-valid", Title: "SOA RNAME Valid"}
	defer func() { res.DurationMs = measureDuration(start) }()

	rname := soa.Mbox
	if rname == "" || rname == "." {
		res.Status = StatusFail
		res.Message = "RNAME is empty"
		return res
	}

	// RNAME should be an email address encoded as DNS name.
	// The first "." that is not escaped represents the "@".
	parts := dns.SplitDomainName(rname)
	if len(parts) < 2 {
		res.Status = StatusWarn
		res.Message = fmt.Sprintf("RNAME %s appears malformed", rname)
		return res
	}

	// Convert to email format for display.
	email := parts[0] + "@" + strings.Join(parts[1:], ".")
	res.Details = append(res.Details, fmt.Sprintf("RNAME: %s (email: %s)", rname, email))

	res.Status = StatusPass
	res.Message = fmt.Sprintf("RNAME is properly formatted (%s)", email)
	return res
}

func checkSOARefresh(soa *dns.SOA) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-refresh", Title: "SOA Refresh"}
	defer func() { res.DurationMs = measureDuration(start) }()

	val := soa.Refresh
	res.Details = append(res.Details, fmt.Sprintf("Refresh: %d seconds (%s)", val, humanDuration(val)))

	if val >= 1200 && val <= 43200 {
		res.Status = StatusPass
		res.Message = fmt.Sprintf("Refresh value %d is within recommended range (1200-43200)", val)
	} else {
		res.Status = StatusWarn
		if val < 1200 {
			res.Message = fmt.Sprintf("Refresh value %d is too low (recommended minimum 1200)", val)
		} else {
			res.Message = fmt.Sprintf("Refresh value %d is too high (recommended maximum 43200)", val)
		}
	}
	return res
}

func checkSOARetry(soa *dns.SOA) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-retry", Title: "SOA Retry"}
	defer func() { res.DurationMs = measureDuration(start) }()

	val := soa.Retry
	res.Details = append(res.Details, fmt.Sprintf("Retry: %d seconds (%s)", val, humanDuration(val)))

	if val >= 120 && val <= 7200 {
		res.Status = StatusPass
		res.Message = fmt.Sprintf("Retry value %d is within recommended range (120-7200)", val)
	} else {
		res.Status = StatusWarn
		if val < 120 {
			res.Message = fmt.Sprintf("Retry value %d is too low (recommended minimum 120)", val)
		} else {
			res.Message = fmt.Sprintf("Retry value %d is too high (recommended maximum 7200)", val)
		}
	}
	return res
}

func checkSOAExpire(soa *dns.SOA) CheckResult {
	start := time.Now()
	res := CheckResult{ID: "soa-expire", Title: "SOA Expire"}
	defer func() { res.DurationMs = measureDuration(start) }()

	val := soa.Expire
	res.Details = append(res.Details, fmt.Sprintf("Expire: %d seconds (%s)", val, humanDuration(val)))

	if val >= 604800 && val <= 4838400 {
		res.Status = StatusPass
		res.Message = fmt.Sprintf("Expire value %d is within recommended range (604800-4838400)", val)
	} else {
		res.Status = StatusWarn
		if val < 604800 {
			res.Message = fmt.Sprintf("Expire value %d is too low (recommended minimum 604800 = 1 week)", val)
		} else {
			res.Message = fmt.Sprintf("Expire value %d is too high (recommended maximum 4838400 = 8 weeks)", val)
		}
	}
	return res
}

func humanDuration(seconds uint32) string {
	if seconds < 60 {
		return fmt.Sprintf("%d seconds", seconds)
	}
	if seconds < 3600 {
		return fmt.Sprintf("%d minutes", seconds/60)
	}
	if seconds < 86400 {
		return fmt.Sprintf("%.1f hours", float64(seconds)/3600)
	}
	return fmt.Sprintf("%.1f days", float64(seconds)/86400)
}