package validate

import (
	"regexp"
	"strconv"
	"strings"

	"jarl/internal/model"
	"jarl/internal/namedconf"
)

// defaultMaxZoneTTL is max-zone-ttl of BIND's built-in policies (and of
// custom ones that don't set it): named refuses to load a signed zone
// with a longer TTL.
const defaultMaxZoneTTL = 86400

// Policies returns the custom dnssec-policy statements defined at the top
// level, by name.
func Policies(s *model.State) map[string]*namedconf.Stmt {
	out := map[string]*namedconf.Stmt{}
	for _, o := range s.ScopedOptions(model.ScopeTopLevel, 0) {
		if strings.ToLower(o.Name) != "dnssec-policy" {
			continue
		}
		stmt, err := namedconf.ParseOptionValue(o.Name, o.Value)
		if err != nil || stmt.Arg(0) == "" {
			continue
		}
		out[stmt.Arg(0)] = stmt
	}
	return out
}

func (c *checker) checkDNSSEC() {
	policies := Policies(c.s)
	// A custom policy without keys crashes named 9.20 when it loads the
	// configuration (an assertion in kaspconf.c), although named-checkconf
	// accepts it. BIND's built-in "insecure" policy is the way to go
	// unsigned.
	for _, o := range c.s.ScopedOptions(model.ScopeTopLevel, 0) {
		if strings.ToLower(o.Name) != "dnssec-policy" {
			continue
		}
		stmt, err := namedconf.ParseOptionValue(o.Name, o.Value)
		if err != nil {
			continue // reported by checkOptions
		}
		if b := stmt.FirstBlock(); b != nil {
			if keys := namedconf.FindOne(b.Stmts, "keys"); keys != nil {
				if kb := keys.FirstBlock(); kb != nil && len(kb.Stmts) == 0 {
					c.errf("dnssec_policy_no_keys", "option", o.ID, "dnssec-policy %s has an empty keys list, which makes named 9.20 crash when it loads the configuration; to remove signing from a zone, use BIND's built-in insecure policy (jarl zone dnssec disable)", stmt.Arg(0))
				}
			}
		}
	}

	for _, z := range c.s.SortedZones() {
		if z.DNSSECPolicy == "" {
			continue
		}
		if z.Type != model.ZonePrimary {
			c.zoneProblem(z, Error, "dnssec_zone_type", "only primary zones can be signed by Jarl; a %s zone gets its signatures from its primary", z.Type)
			continue
		}
		maxTTL := uint32(defaultMaxZoneTTL)
		switch z.DNSSECPolicy {
		case model.DNSSECDefault, model.DNSSECInsecure:
		default:
			stmt := policies[z.DNSSECPolicy]
			if stmt == nil {
				c.zoneProblem(z, Error, "dnssec_policy_unknown", "dnssec-policy %q doesn't exist: use default (BIND's built-in policy), or define it as a top-level dnssec-policy statement", z.DNSSECPolicy)
				continue
			}
			if b := stmt.FirstBlock(); b != nil {
				if m := namedconf.FindOne(b.Stmts, "max-zone-ttl"); m != nil {
					if v, ok := parseDuration(m.Arg(0)); ok && v > 0 {
						maxTTL = v
					}
				}
			}
		}
		if o := c.s.FindOption(model.ScopeZone, z.ID, "inline-signing"); o != nil && isNo(o.Value) {
			c.zoneProblem(z, Error, "dnssec_inline_signing", "a signed zone needs inline signing: named keeps its signatures in a separate copy of the zone, because Jarl rewrites the zone file (remove the inline-signing option)")
		}
		// named refuses to load a signed zone with a TTL above the
		// policy's max-zone-ttl, and keeps serving the old version.
		if z.DefaultTTL > maxTTL {
			c.zoneProblem(z, Error, "dnssec_ttl_too_long", "the default TTL (%d) is longer than the DNSSEC policy's max-zone-ttl (%d), so named would refuse to load the signed zone; lower it to %d or less", z.DefaultTTL, maxTTL, maxTTL)
		}
		for _, r := range c.zoneRecords[z.ID] {
			if r.TTL != nil && *r.TTL > maxTTL {
				p := c.zoneProblem(z, Error, "dnssec_ttl_too_long", "%s %s has TTL %d, longer than the DNSSEC policy's max-zone-ttl (%d), so named would refuse to load the signed zone; lower it to %d or less", strings.TrimSuffix(r.Name, "."), r.Type, *r.TTL, maxTTL, maxTTL)
				p.ObjectType, p.ObjectID, p.Name = "record", r.ID, r.Name
			}
		}
	}
}

func isNo(v string) bool {
	switch strings.ToLower(strings.Trim(strings.TrimSpace(v), `";`)) {
	case "no", "false", "0":
		return true
	}
	return false
}

var (
	isoDuration = regexp.MustCompile(`^P(?:(\d+)Y)?(?:(\d+)M)?(?:(\d+)W)?(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?$`)
	ttlDuration = regexp.MustCompile(`^(?:\d+[wdhms])+$`)
	ttlPart     = regexp.MustCompile(`(\d+)([wdhms])`)
)

// parseDuration parses a BIND duration: ISO 8601 (P1D, PT12H), seconds, or
// TTL style (1d, 12h30m).
func parseDuration(s string) (uint32, bool) {
	s = strings.ToUpper(strings.TrimSpace(s))
	if n, err := strconv.ParseUint(s, 10, 32); err == nil {
		return uint32(n), true
	}
	if m := isoDuration.FindStringSubmatch(s); m != nil && s != "P" && s != "PT" {
		units := []uint64{31536000, 2592000, 604800, 86400, 3600, 60, 1}
		var total uint64
		for i, u := range units {
			if m[i+1] != "" {
				n, _ := strconv.ParseUint(m[i+1], 10, 32)
				total += n * u
			}
		}
		return uint32(min(total, 1<<32-1)), true
	}
	l := strings.ToLower(s)
	if ttlDuration.MatchString(l) {
		units := map[string]uint64{"w": 604800, "d": 86400, "h": 3600, "m": 60, "s": 1}
		var total uint64
		for _, m := range ttlPart.FindAllStringSubmatch(l, -1) {
			n, _ := strconv.ParseUint(m[1], 10, 32)
			total += n * units[m[2]]
		}
		return uint32(min(total, 1<<32-1)), true
	}
	return 0, false
}