// Package tlsrptdb stores reports from "SMTP TLS Reporting" in its database.
package tlsrptdb

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promauto"

	"github.com/mjl-/bstore"

	"github.com/mjl-/mox/dns"
	"github.com/mjl-/mox/mlog"
	"github.com/mjl-/mox/mox-"
	"github.com/mjl-/mox/tlsrpt"
)

var (
	xlog = mlog.New("tlsrptdb")

	tlsrptDB *bstore.DB
	mutex    sync.Mutex

	metricSession = promauto.NewCounterVec(
		prometheus.CounterOpts{
			Name: "mox_tlsrptdb_session_total",
			Help: "Number of sessions, both success and known result types.",
		},
		[]string{"type"}, // Known result types, and "success"
	)

	knownResultTypes = map[tlsrpt.ResultType]struct{}{
		tlsrpt.ResultSTARTTLSNotSupported:    {},
		tlsrpt.ResultCertificateHostMismatch: {},
		tlsrpt.ResultCertificateExpired:      {},
		tlsrpt.ResultTLSAInvalid:             {},
		tlsrpt.ResultDNSSECInvalid:           {},
		tlsrpt.ResultDANERequired:            {},
		tlsrpt.ResultCertificateNotTrusted:   {},
		tlsrpt.ResultSTSPolicyInvalid:        {},
		tlsrpt.ResultSTSWebPKIInvalid:        {},
		tlsrpt.ResultValidationFailure:       {},
		tlsrpt.ResultSTSPolicyFetch:          {},
	}
)

// TLSReportRecord is a TLS report as a database record, including information
// about the sender.
//
// todo: should be named just Record, but it would cause a sherpa type name conflict.
type TLSReportRecord struct {
	ID         int64  `bstore:"typename Record"`
	Domain     string `bstore:"index"` // Domain to which the TLS report applies.
	FromDomain string
	MailFrom   string
	Report     tlsrpt.Report
}

func database() (rdb *bstore.DB, rerr error) {
	mutex.Lock()
	defer mutex.Unlock()
	if tlsrptDB == nil {
		p := mox.DataDirPath("tlsrpt.db")
		os.MkdirAll(filepath.Dir(p), 0770)
		db, err := bstore.Open(p, &bstore.Options{Timeout: 5 * time.Second, Perm: 0660}, TLSReportRecord{})
		if err != nil {
			return nil, err
		}
		tlsrptDB = db
	}
	return tlsrptDB, nil
}

// Init opens and possibly initializes the database.
func Init() error {
	_, err := database()
	return err
}

// Close closes the database connection.
func Close() {
	mutex.Lock()
	defer mutex.Unlock()
	if tlsrptDB != nil {
		err := tlsrptDB.Close()
		xlog.Check(err, "closing database")
		tlsrptDB = nil
	}
}

// AddReport adds a TLS report to the database.
//
// The report should have come in over SMTP, with a DKIM-validated
// verifiedFromDomain. Using HTTPS for reports is not recommended as there is no
// authentication on the reports origin.
//
// The report is currently required to only cover a single domain in its policy
// domain. Only reports for known domains are added to the database.
//
// Prometheus metrics are updated only for configured domains.
func AddReport(ctx context.Context, verifiedFromDomain dns.Domain, mailFrom string, r *tlsrpt.Report) error {
	log := xlog.WithContext(ctx)

	db, err := database()
	if err != nil {
		return err
	}

	if len(r.Policies) == 0 {
		return fmt.Errorf("no policies in report")
	}

	var reportdom, zerodom dns.Domain
	record := TLSReportRecord{0, "", verifiedFromDomain.Name(), mailFrom, *r}

	for _, p := range r.Policies {
		pp := p.Policy

		// Check domain, they must all be the same for now (in future, with DANE, this may
		// no longer apply).
		d, err := dns.ParseDomain(pp.Domain)
		if err != nil {
			log.Errorx("invalid domain in tls report", err, mlog.Field("domain", pp.Domain), mlog.Field("mailfrom", mailFrom))
			continue
		}
		if _, ok := mox.Conf.Domain(d); !ok {
			log.Info("unknown domain in tls report, not storing", mlog.Field("domain", d), mlog.Field("mailfrom", mailFrom))
			return fmt.Errorf("unknown domain")
		}
		if reportdom != zerodom && d != reportdom {
			return fmt.Errorf("multiple domains in report %v and %v", reportdom, d)
		}
		reportdom = d

		metricSession.WithLabelValues("success").Add(float64(p.Summary.TotalSuccessfulSessionCount))
		for _, f := range p.FailureDetails {
			var result string
			if _, ok := knownResultTypes[f.ResultType]; ok {
				result = string(f.ResultType)
			} else {
				result = "other"
			}
			metricSession.WithLabelValues(result).Add(float64(f.FailedSessionCount))
		}
	}
	record.Domain = reportdom.Name()
	return db.Insert(&record)
}

// Records returns all TLS reports in the database.
func Records(ctx context.Context) ([]TLSReportRecord, error) {
	db, err := database()
	if err != nil {
		return nil, err
	}
	return bstore.QueryDB[TLSReportRecord](db).List()
}

// RecordID returns the report for the ID.
func RecordID(ctx context.Context, id int64) (TLSReportRecord, error) {
	db, err := database()
	if err != nil {
		return TLSReportRecord{}, err
	}

	e := TLSReportRecord{ID: id}
	err = db.Get(&e)
	return e, err
}

// RecordsPeriodDomain returns the reports overlapping start and end, for the given
// domain. If domain is empty, all records match for domain.
func RecordsPeriodDomain(ctx context.Context, start, end time.Time, domain string) ([]TLSReportRecord, error) {
	db, err := database()
	if err != nil {
		return nil, err
	}

	q := bstore.QueryDB[TLSReportRecord](db)
	if domain != "" {
		q.FilterNonzero(TLSReportRecord{Domain: domain})
	}
	q.FilterFn(func(r TLSReportRecord) bool {
		dr := r.Report.DateRange
		return !dr.Start.Before(start) && dr.Start.Before(end) || dr.End.After(start) && !dr.End.After(end)
	})
	return q.List()
}