package validate

import (
	"fmt"
	"strings"

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

// checkLinked checks linked zones (docs/views.md#linked-zones): what can
// be linked, and that their shared records are in step. Jarl keeps them
// in step itself; they can only drift when a change was staged before the
// zones were linked (or by editing the database).
func (c *checker) checkLinked() {
	groups := map[int64][]*model.Zone{}
	for _, z := range c.s.SortedZones() {
		if z.LinkGroup != 0 {
			groups[z.LinkGroup] = append(groups[z.LinkGroup], z)
		}
	}
	for _, g := range sortedGroupIDs(groups) {
		zs := c.s.LinkMembers(g)
		label := func(z *model.Zone) string {
			if v := c.s.ViewName(z); v != "" {
				return dnsname.Display(z.Name) + " [" + v + "]"
			}
			return dnsname.Display(z.Name)
		}
		bad := false
		for _, z := range zs {
			switch {
			case z.Type != model.ZonePrimary:
				c.errf("linked_zone_type", "zone", z.ID, "zone %s is linked, but only primary zones can be: unlink it", label(z))
				bad = true
			case z.Name != zs[0].Name:
				c.errf("linked_zone_name", "zone", z.ID, "zone %s is linked with %s; only zones of the same name can be linked", label(z), label(zs[0]))
				bad = true
			}
		}
		if len(zs) == 1 {
			c.infof("linked_zone_alone", "zone", zs[0].ID, "zone %s is linked with no other zone; unlink it (jarl zone unlink)", label(zs[0]))
			continue
		}
		if bad {
			continue
		}
		// Shared and local records of one name and type can't mix in a zone.
		type key struct{ name, typ string }
		keys := map[key]bool{}
		var order []key
		for _, z := range zs {
			for _, r := range c.s.ZoneRecords(z.ID) {
				k := key{r.Name, r.Type}
				if !keys[k] {
					keys[k] = true
					order = append(order, k)
				}
			}
		}
		for _, k := range order {
			var truth []*model.Record
			var truthZone *model.Zone
			for _, z := range zs {
				rs := c.s.RRset(z.ID, k.name, k.typ)
				local, shared := 0, 0
				for _, r := range rs {
					if r.SharedID == 0 {
						local++
					} else {
						shared++
					}
				}
				if local > 0 && shared > 0 {
					c.errf("linked_mixed", "zone", z.ID, "%s %s in zone %s has both shared and local records; make the set one or the other", dnsname.Display(k.name), k.typ, label(z)).Zone = z.Name
					continue
				}
				if local > 0 {
					continue // an override
				}
				got := c.s.SharedRecords(z.ID, k.name, k.typ)
				if truthZone == nil {
					truth, truthZone = got, z
					continue
				}
				if diff := sharedDiff(truth, got); diff != "" {
					p := c.errf("linked_out_of_sync", "zone", z.ID, "linked zones %s and %s differ at %s %s (%s). Jarl keeps them in step, so a change was probably staged before they were linked: link them again (jarl zone link) to work out what is shared", label(truthZone), label(z), dnsname.Display(k.name), k.typ, diff)
					p.Zone = z.Name
				}
			}
		}
	}
}

func sortedGroupIDs(m map[int64][]*model.Zone) []int64 {
	var out []int64
	for k := range m {
		out = append(out, k)
	}
	for i := range out {
		for j := i + 1; j < len(out); j++ {
			if out[j] < out[i] {
				out[i], out[j] = out[j], out[i]
			}
		}
	}
	return out
}

// sharedDiff says how two zones' copies of a shared set differ ("" when
// they don't).
func sharedDiff(a, b []*model.Record) string {
	idx := map[int64]*model.Record{}
	for _, r := range b {
		idx[r.SharedID] = r
	}
	var out []string
	for _, r := range a {
		o := idx[r.SharedID]
		delete(idx, r.SharedID)
		switch {
		case o == nil:
			out = append(out, "missing "+r.Data)
		case o.Data != r.Data:
			out = append(out, r.Data+" vs "+o.Data)
		case !sameTTLPtr(o.TTL, r.TTL):
			out = append(out, "TTL of "+r.Data)
		case o.Disabled != r.Disabled:
			out = append(out, "disabled "+r.Data)
		}
	}
	for _, r := range idx {
		out = append(out, "extra "+r.Data)
	}
	if len(out) > 3 {
		out = append(out[:3], fmt.Sprintf("and %d more", len(out)-3))
	}
	return strings.Join(out, ", ")
}

func sameTTLPtr(a, b *uint32) bool {
	if a == nil || b == nil {
		return a == nil && b == nil
	}
	return *a == *b
}