package storage

import (
	"context"
	"fmt"
	"net/netip"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"
)

const UserAgentMaxBytes = 256

func CleanUserAgent(s string) string {
	s = strings.Trim(s, " \t")
	if !utf8.ValidString(s) {
		return ""
	}
	for _, r := range s {
		if unicode.IsControl(r) || unicode.Is(unicode.Bidi_Control, r) {
			return ""
		}
	}
	if len(s) <= UserAgentMaxBytes {
		return s
	}
	cut := UserAgentMaxBytes
	for cut > 0 && !utf8.RuneStart(s[cut]) {
		cut--
	}
	return s[:cut]
}

func validClientColumns(in CreateForwardSessionInput) error {
	switch {
	case in.UserAgent != "" && CleanUserAgent(in.UserAgent) != in.UserAgent:
		return fmt.Errorf("user agent is not clean or over %d bytes", UserAgentMaxBytes)
	case in.ClientID != "" && !validClientID(in.ClientID):
		return fmt.Errorf("client id is not an OIDC client id")
	case in.Address.IsValid() && (in.Address.Zone() != "" || in.Address.Is4In6()):
		return fmt.Errorf("address carries a zone or is IPv4-mapped")
	}
	return nil
}

func validClientID(s string) bool {
	if len(s) > 32 {
		return false
	}
	for i := 0; i < len(s); i++ {
		c := s[i]
		if (c < 'a' || c > 'z') && (c < '0' || c > '9') && c != '_' {
			return false
		}
	}
	return true
}

func nullAddress(a netip.Addr) any {
	if !a.IsValid() {
		return nil
	}
	return a.String()
}

type SessionSeen struct {
	ID              string
	At, StaleBefore time.Time
}

func (s *Store) TouchForwardSession(ctx context.Context, id string, at, staleBefore time.Time) (bool, error) {
	changed, err := s.TouchForwardSessions(ctx, []SessionSeen{{ID: id, At: at, StaleBefore: staleBefore}})
	return changed > 0, err
}

func (s *Store) TouchForwardSessions(ctx context.Context, seen []SessionSeen) (int64, error) {
	const operation = "touch forward sessions"
	if err := s.checkOpen(operation); err != nil {
		return 0, err
	}
	tx, err := s.sql.BeginTx(ctx, nil)
	if err != nil {
		return 0, classify("begin "+operation, err)
	}
	defer tx.Rollback()
	var changed int64
	for _, one := range seen {
		n, err := execCount(ctx, tx, operation, `
UPDATE forward_sessions SET last_seen_at = ?
WHERE id = ? AND revoked = 0 AND (last_seen_at IS NULL OR last_seen_at < ?)`, timeToInt(one.At), one.ID, timeToInt(one.StaleBefore))
		if err != nil {
			return 0, err
		}
		changed += n
	}
	return changed, classify("commit "+operation, tx.Commit())
}