package validate

import (
	"fmt"
	"path/filepath"
	"strings"

	"jarl/internal/dnsname"
	"jarl/internal/model"
)

const maxTTL = 2147483647

func (c *checker) zoneProblem(z *model.Zone, sev Severity, code, format string, args ...any) *Problem {
	var p *Problem
	switch sev {
	case Error:
		p = c.errf(code, "zone", z.ID, format, args...)
	case Warning:
		p = c.warnf(code, "zone", z.ID, format, args...)
	default:
		p = c.infof(code, "zone", z.ID, format, args...)
	}
	p.Zone = z.Name
	p.View = c.s.ViewName(z)
	return p
}

func (c *checker) checkZones() {
	hasViews := len(c.s.Views) > 0
	type zkey struct {
		view int64
		name string
	}
	seen := map[zkey]bool{}
	viewPos := map[int64]int{}
	for i, v := range c.s.OrderedViews() {
		viewPos[v.ID] = i
	}
	for _, z := range c.s.SortedZones() {
		if z.ViewID != 0 && c.s.Views[z.ViewID] == nil {
			c.zoneProblem(z, Error, "zone_view_missing", "the zone's view (id %d) does not exist", z.ViewID)
			continue
		}
		if hasViews && z.ViewID == 0 {
			c.zoneProblem(z, Error, "zone_outside_view", "when views are used, every zone must be inside a view (named requires this); move the zone into a view")
		}
		if err := dnsname.CheckZoneName(z.Name); err != nil {
			c.zoneProblem(z, Error, "zone_name_invalid", "invalid zone name: %v", err)
		}
		k := zkey{z.ViewID, z.Name}
		if seen[k] {
			c.zoneProblem(z, Error, "zone_duplicate", "the zone is defined more than once in the same view")
		}
		seen[k] = true

		switch z.Type {
		case model.ZonePrimary:
			c.checkPrimary(z)
		case model.ZoneSecondary, model.ZoneStub:
			if c.s.FindOption(model.ScopeZone, z.ID, "primaries") == nil {
				c.zoneProblem(z, Error, "zone_missing_option", "%s zones need a primaries option listing the primary servers", z.Type)
			}
		case model.ZoneMirror:
			if z.Name != dnsname.Root && c.s.FindOption(model.ScopeZone, z.ID, "primaries") == nil {
				c.zoneProblem(z, Error, "zone_missing_option", "mirror zones other than the root zone need a primaries option")
			}
		case model.ZoneForward:
			if c.s.FindOption(model.ScopeZone, z.ID, "forwarders") == nil {
				c.zoneProblem(z, Info, "zone_no_forwarders", "the forward zone has no forwarders option, so names in it are resolved normally (forwarding is disabled for this domain)")
			}
		case model.ZoneHint:
			if z.File == "" {
				c.zoneProblem(z, Error, "zone_file_required", "hint zones need a file (for example /usr/share/dns/root.hints)")
			}
			if z.Name != dnsname.Root {
				c.zoneProblem(z, Warning, "zone_hint_name", "hint zones are normally the root zone \".\"")
			}
		case model.ZoneRedirect:
			if z.Name != dnsname.Root {
				c.zoneProblem(z, Error, "zone_name_invalid", "redirect zones must be named \".\"")
			}
			if z.File == "" && c.s.FindOption(model.ScopeZone, z.ID, "primaries") == nil {
				c.zoneProblem(z, Error, "zone_file_required", "redirect zones need a file or a primaries option")
			}
		case model.ZoneStaticStub:
			if c.s.FindOption(model.ScopeZone, z.ID, "server-addresses") == nil && c.s.FindOption(model.ScopeZone, z.ID, "server-names") == nil {
				c.zoneProblem(z, Error, "zone_missing_option", "static-stub zones need server-addresses or server-names")
			}
		case model.ZoneInView:
			c.checkInView(z, viewPos)
		default:
			c.zoneProblem(z, Error, "zone_type_invalid", "unknown zone type %q", z.Type)
		}

		if z.File != "" {
			switch z.Type {
			case model.ZonePrimary:
				c.zoneProblem(z, Error, "zone_file_managed", "the file of a primary zone is generated by Jarl and can't be set")
			case model.ZoneForward, model.ZoneStaticStub, model.ZoneInView:
				c.zoneProblem(z, Error, "zone_file_invalid", "%s zones have no file", z.Type)
			default:
				if !filepath.IsAbs(z.File) {
					c.zoneProblem(z, Error, "zone_file_invalid", "zone file %q must be an absolute path", z.File)
				}
			}
		}
		if !z.HasRecords() && len(c.zoneRecords[z.ID]) > 0 {
			c.zoneProblem(z, Error, "zone_records_unmanaged", "%s zones can't have records managed by Jarl (they get their data from elsewhere); delete the %d records or change the type to primary", z.Type, len(c.zoneRecords[z.ID]))
		}
	}
}

func (c *checker) checkInView(z *model.Zone, viewPos map[int64]int) {
	if z.ViewID == 0 {
		c.zoneProblem(z, Error, "zone_inview_invalid", "in-view zones can only be used inside views")
		return
	}
	target := c.s.ViewByName(z.InView)
	if target == nil {
		c.zoneProblem(z, Error, "zone_inview_invalid", "in-view refers to view %q, which does not exist", z.InView)
		return
	}
	if target.ID == z.ViewID {
		c.zoneProblem(z, Error, "zone_inview_invalid", "in-view can't refer to the zone's own view")
		return
	}
	if viewPos[target.ID] > viewPos[z.ViewID] {
		c.zoneProblem(z, Error, "zone_inview_invalid", "in-view refers to view %q, which comes after this view; named only allows references to earlier views (reorder the views)", target.Name)
	}
	src := c.s.FindZone(z.Name, target.ID)
	if src == nil {
		c.zoneProblem(z, Error, "zone_inview_invalid", "view %q has no zone %s to share", target.Name, dnsname.Display(z.Name))
	} else if src.Type != model.ZonePrimary && src.Type != model.ZoneSecondary {
		c.zoneProblem(z, Error, "zone_inview_invalid", "in-view can only share primary or secondary zones, but %s in view %q is %s", dnsname.Display(z.Name), target.Name, src.Type)
	}
	for _, o := range c.s.ScopedOptions(model.ScopeZone, z.ID) {
		if o.Name != "forward" && o.Name != "forwarders" {
			c.zoneProblem(z, Error, "zone_inview_option", "in-view zones may only set forward and forwarders, not %s (set it on the zone in view %q)", o.Name, z.InView)
		}
	}
}

func (c *checker) checkPrimary(z *model.Zone) {
	soa := z.SOA
	if soa.MName == "" || !dnsname.IsHostname(soa.MName, false) {
		c.zoneProblem(z, Error, "soa_invalid", "SOA primary name server (mname) %q is not a valid host name", dnsname.Display(soa.MName))
	}
	if soa.RName == "" || !dnsname.IsMailbox(soa.RName) {
		c.zoneProblem(z, Error, "soa_invalid", "SOA contact (rname) %q is not a valid mailbox (use hostmaster.example.com. or an email address)", soa.RName)
	}
	for name, v := range map[string]uint32{"refresh": soa.Refresh, "retry": soa.Retry, "expire": soa.Expire, "minimum": soa.Minimum} {
		if v > maxTTL {
			c.zoneProblem(z, Error, "soa_invalid", "SOA %s %d is larger than 2147483647", name, v)
		}
	}
	if soa.Refresh < 60 {
		c.zoneProblem(z, Warning, "soa_warning", "SOA refresh %ds is very short; secondaries will poll constantly", soa.Refresh)
	}
	if soa.Retry >= soa.Refresh && soa.Refresh > 0 {
		c.zoneProblem(z, Warning, "soa_warning", "SOA retry (%d) should be shorter than refresh (%d)", soa.Retry, soa.Refresh)
	}
	if soa.Expire < soa.Refresh+soa.Retry {
		c.zoneProblem(z, Warning, "soa_warning", "SOA expire (%d) should be longer than refresh + retry", soa.Expire)
	} else if soa.Expire < 604800 {
		c.zoneProblem(z, Warning, "soa_warning", "SOA expire is under a week (%d); 2-4 weeks is recommended so secondaries survive a primary outage", soa.Expire)
	}
	// Resolvers cache "no such name/type" answers for the smaller of the
	// SOA minimum and the SOA record's own TTL (RFC 2308 section 5); the
	// SOA record uses the zone's default TTL.
	if neg := min(soa.Minimum, z.DefaultTTL); neg > 10800 {
		cmd := "jarl zone update " + dnsname.Display(z.Name)
		if v := c.s.ViewName(z); v != "" {
			cmd += " --view " + v
		}
		c.zoneProblem(z, Warning, "soa_warning", "resolvers may cache negative answers (\"no such name\") from this zone for %s (the smaller of the SOA minimum, %d, and the zone's default TTL, %d), so a name you add can stay invisible that long to anyone who looked it up before; RFC 2308 recommends 1 to 3 hours (lower it with '%s --minimum 3600')",
			humanSeconds(neg), soa.Minimum, z.DefaultTTL, cmd)
	}
	if z.DefaultTTL > maxTTL {
		c.zoneProblem(z, Error, "ttl_invalid", "default TTL %d is larger than 2147483647", z.DefaultTTL)
	}
	switch z.SerialPolicy {
	case "", model.SerialDate, model.SerialIncrement, model.SerialUnixtime:
	default:
		c.zoneProblem(z, Error, "zone_serial_policy", "unknown serial policy %q (use date, increment or unixtime)", z.SerialPolicy)
	}
	if strings.Contains(z.Name, "/") {
		c.zoneProblem(z, Info, "zone_name_slash", "zone names with '/' (RFC 2317) are supported, but the file name is escaped")
	}
	c.checkZoneRecords(z)
}

// humanSeconds formats a duration in seconds as e.g. "1 day" or "12 hours".
func humanSeconds(n uint32) string {
	for _, u := range []struct {
		secs uint32
		name string
	}{{604800, "week"}, {86400, "day"}, {3600, "hour"}, {60, "minute"}} {
		if n >= u.secs && n%u.secs == 0 {
			if v := n / u.secs; v != 1 {
				return fmt.Sprintf("%d %ss", v, u.name)
			}
			return "1 " + u.name
		}
	}
	return fmt.Sprintf("%d seconds", n)
}