package engine

import (
	"fmt"
	"sort"
	"strings"

	"jarl/internal/catalog"
	"jarl/internal/dnsname"
	"jarl/internal/model"
	"jarl/internal/namedconf"
)

type refKind int

const (
	refACL refKind = iota
	refKey
)

func sameRef(kind refKind, a, b string) bool {
	if kind == refKey {
		return model.NormalizeKeyName(a) == model.NormalizeKeyName(b)
	}
	return strings.EqualFold(a, b)
}

// rewriteElements renames references in ACL-style element strings. It
// returns the new list and whether anything matched.
func rewriteElements(list []string, kind refKind, old, new string) ([]string, bool) {
	changed := false
	var fix func(es []namedconf.AMElement) []namedconf.AMElement
	fix = func(es []namedconf.AMElement) []namedconf.AMElement {
		for i := range es {
			e := &es[i]
			switch {
			case kind == refACL && e.Kind == namedconf.AMName && !e.IsBuiltin() && sameRef(kind, e.Name, old):
				e.Name, changed = new, true
			case kind == refKey && e.Kind == namedconf.AMKey && sameRef(kind, e.Name, old):
				e.Name, changed = new, true
			case e.Kind == namedconf.AMNested:
				e.Nested = fix(e.Nested)
			}
		}
		return es
	}
	out := make([]string, len(list))
	for i, s := range list {
		e, err := namedconf.ParseAMElement(s)
		if err != nil {
			out[i] = s
			continue
		}
		res := fix([]namedconf.AMElement{e})
		out[i] = res[0].String()
	}
	return out, changed
}

// walkRefs calls fn for every reference of the given kind in items. fn may
// change the value's text.
func walkRefs(items []namedconf.Item, kind refKind, aml bool, fn func(v *namedconf.Value)) {
	for i := 0; i < len(items); i++ {
		it := items[i]
		if it.Value != nil && !it.Value.Quoted && i+1 < len(items) {
			switch strings.ToLower(it.Value.Text) {
			case "key":
				if kind == refKey && items[i+1].Value != nil {
					fn(items[i+1].Value)
				}
				i++
				continue
			case "keys":
				next := items[i+1]
				if kind == refKey {
					if next.Value != nil {
						fn(next.Value)
					} else if next.Block != nil {
						for _, s := range next.Block.Stmts {
							if len(s.Items) == 1 && s.Items[0].Value != nil {
								fn(s.Items[0].Value)
							}
						}
					}
				}
				i++
				continue
			}
		}
		if it.Block == nil {
			continue
		}
		for _, s := range it.Block.Stmts {
			if kind == refACL && aml {
				var v *namedconf.Value
				switch {
				case len(s.Items) == 1 && s.Items[0].Value != nil:
					v = s.Items[0].Value
				case len(s.Items) == 2 && s.Items[0].Bang && s.Items[1].Value != nil:
					v = s.Items[1].Value
				}
				if v != nil && !namedconf.BuiltinACLs[strings.ToLower(v.Text)] {
					fn(v)
					continue
				}
			}
			walkRefs(s.Items, kind, aml, fn)
		}
	}
}

// optionHasAML reports whether the option's grammar contains address match
// lists (so single words in its blocks are ACL names).
func optionHasAML(st *model.State, o *model.Option) bool {
	cs := catalogScope(st, o.Scope, o.ScopeID)
	stmt, ok := catalog.Default().Lookup(cs, o.Name)
	return ok && strings.Contains(stmt.Grammar, "<address_match_element>")
}

func optionLabel(st *model.State, o *model.Option) string {
	switch o.Scope {
	case model.ScopeView:
		if v := st.Views[o.ScopeID]; v != nil {
			return fmt.Sprintf("view %s option %s", v.Name, o.Name)
		}
	case model.ScopeZone:
		if z := st.Zones[o.ScopeID]; z != nil {
			label := "zone " + dnsname.Display(z.Name)
			if v := st.ViewName(z); v != "" {
				label += " [view " + v + "]"
			}
			return label + " option " + o.Name
		}
	case model.ScopeTopLevel:
		return "top-level statement " + o.Name
	}
	return "server option " + o.Name
}

// FindRefs lists the objects that refer to an ACL or key by name.
func FindRefs(st *model.State, kind refKind, name string) []string {
	var out []string
	for _, a := range st.SortedACLs() {
		if _, hit := rewriteElements(a.Elements, kind, name, name); hit {
			out = append(out, "ACL "+a.Name)
		}
	}
	for _, v := range st.OrderedViews() {
		_, h1 := rewriteElements(v.MatchClients, kind, name, name)
		_, h2 := rewriteElements(v.MatchDestinations, kind, name, name)
		if h1 || h2 {
			out = append(out, "view "+v.Name)
		}
	}
	var opts []string
	for _, o := range st.Options {
		stmt, err := namedconf.ParseOptionValue(o.Name, o.Value)
		if err != nil {
			continue
		}
		hit := false
		walkRefs(stmt.Items, kind, optionHasAML(st, o), func(v *namedconf.Value) {
			if sameRef(kind, v.Text, name) {
				hit = true
			}
		})
		if hit {
			opts = append(opts, optionLabel(st, o))
		}
	}
	sort.Strings(opts)
	return append(out, opts...)
}

// renameRefs rewrites references to an ACL or key after a rename.
func renameRefs(st *model.State, kind refKind, old, new string, c *applyCtx) {
	for _, a := range st.ACLs {
		if l, hit := rewriteElements(a.Elements, kind, old, new); hit {
			a.Elements = l
			a.Touch(c.user(), c.now)
		}
	}
	for _, v := range st.Views {
		l1, h1 := rewriteElements(v.MatchClients, kind, old, new)
		l2, h2 := rewriteElements(v.MatchDestinations, kind, old, new)
		if h1 || h2 {
			v.MatchClients, v.MatchDestinations = l1, l2
			v.Touch(c.user(), c.now)
		}
	}
	for _, o := range st.Options {
		stmt, err := namedconf.ParseOptionValue(o.Name, o.Value)
		if err != nil {
			continue
		}
		hit := false
		walkRefs(stmt.Items, kind, optionHasAML(st, o), func(v *namedconf.Value) {
			if sameRef(kind, v.Text, old) {
				v.Text, hit = new, true
			}
		})
		if hit {
			o.Value = namedconf.Compact(stmt.Items[1:])
			o.Touch(c.user(), c.now)
		}
	}
}

// FindACLRefs lists the objects that use the ACL called name.
func FindACLRefs(st *model.State, name string) []string { return FindRefs(st, refACL, name) }

// FindKeyRefs lists the objects that use the TSIG key called name.
func FindKeyRefs(st *model.State, name string) []string { return FindRefs(st, refKey, name) }