// Package catalog knows which named.conf statements are valid where.
//
// It is built at start-up from two files shipped with Jarl: the grammar
// summary printed in named.conf(5) and the statement index from the BIND
// Administrator Reference Manual (both for BIND 9.20). Jarl uses it to
// reject options that are not valid in a scope, to offer the right inputs in
// the web UI, and to show a one-line description of every option.
// named-checkconf remains the final authority on option values.
package catalog

import (
	_ "embed"
	"fmt"
	"regexp"
	"sort"
	"strings"
	"sync"
)

//go:embed data/grammar-9.20.txt
var grammarText string

//go:embed data/statements-9.20.tsv
var statementsTSV string

// Scopes for configuration statements.
const (
	ScopeTop     = "toplevel" // top-level statements (logging, controls, ...)
	ScopeOptions = "options"  // inside options { }
	ScopeView    = "view"     // inside view { }
)

// ZoneScope returns the scope name for statements inside a zone of the
// given type, e.g. "zone:primary".
func ZoneScope(zoneType string) string { return "zone:" + zoneType }

// Kinds of values, used for input widgets and quick validation.
const (
	KindBool     = "bool"
	KindInt      = "integer"
	KindDuration = "duration"
	KindString   = "string" // a quoted string
	KindWord     = "word"   // a single unquoted word
	KindEnum     = "enum"
	KindACL      = "address_match_list"
	KindRaw      = "raw"
)

// Statement describes one configuration statement in one scope.
type Statement struct {
	Name        string   `json:"name"`
	Scope       string   `json:"scope"`
	Grammar     string   `json:"grammar"`
	Kind        string   `json:"kind"`
	Choices     []string `json:"choices,omitempty"`
	Multiple    bool     `json:"multiple"`
	Status      string   `json:"status,omitempty"` // deprecated, obsolete, experimental, test only, not configured
	Description string   `json:"description,omitempty"`
	Tags        []string `json:"tags,omitempty"`
	// Managed statements are represented by first-class Jarl objects or
	// fields (zones, views, ACLs, keys, zone type/file, ...) and cannot be
	// set as free-form options.
	Managed   bool   `json:"managed,omitempty"`
	ManagedBy string `json:"managed_by,omitempty"`
}

// Catalog holds the statements for every scope.
type Catalog struct {
	scopes map[string]map[string]*Statement
	order  map[string][]string
}

var (
	once    sync.Once
	def     *Catalog
	initErr error
)

// Default returns the catalog for BIND 9.20.
func Default() *Catalog {
	once.Do(func() {
		def, initErr = build(grammarText, statementsTSV)
		if initErr != nil {
			panic("catalog: " + initErr.Error())
		}
	})
	return def
}

// managed lists statements that Jarl models itself, per scope.
var managed = map[string]map[string]string{
	ScopeTop: {
		"options": "server options",
		"view":    "views",
		"zone":    "zones",
		"acl":     "ACLs",
		"key":     "TSIG keys",
	},
	ScopeView: {
		"match-clients":        "the view's match-clients field",
		"match-destinations":   "the view's match-destinations field",
		"match-recursive-only": "the view's match-recursive-only field",
		"key":                  "TSIG keys (define keys at the top level)",
		"zone":                 "zones",
		"dnssec-policy":        dnssecManaged,
	},
	ScopeOptions: {
		"dnssec-policy": dnssecManaged,
	},
}

// dnssecManaged: Jarl turns signing on and off per zone, so that it can
// guard the steps (a zone mustn't go unsigned while the parent zone still
// has a DS record for it). dnssec-policy statements that define custom
// policies (at the top level) are still options.
const dnssecManaged = "each zone's DNSSEC setting (jarl zone dnssec enable ZONE; see docs/dnssec.md)"

var zoneManaged = map[string]string{
	"type":          "the zone's type field",
	"file":          "the zone's file (generated by Jarl)",
	"in-view":       "the zone's in-view field",
	"dnssec-policy": dnssecManaged,
	"key-directory": "Jarl (signed zones keep their keys in Jarl's key directory, which its backups include)",
}

// synonyms are older spellings that named 9.20 still accepts.
var synonyms = map[string]map[string]string{
	ScopeTop: {"primaries": "remote-servers", "masters": "remote-servers", "parental-agents": "remote-servers"},
	"zone":   {"masters": "primaries"},
}

// ZoneTypeSynonyms maps old zone type names to their current names.
var ZoneTypeSynonyms = map[string]string{"master": "primary", "slave": "secondary"}

// Canonical returns the current name of a statement, translating older
// synonyms (for example "masters" to "primaries" in zones). The second
// result reports whether name was a synonym.
func Canonical(scope, name string) (string, bool) {
	name = strings.ToLower(name)
	key := scope
	if strings.HasPrefix(scope, "zone:") {
		key = "zone"
	}
	if c, ok := synonyms[key][name]; ok {
		return c, true
	}
	return name, false
}

// Lookup returns the statement name in scope, if it exists. Synonyms are
// resolved to the current statement.
func (c *Catalog) Lookup(scope, name string) (*Statement, bool) {
	n, _ := Canonical(scope, name)
	s, ok := c.scopes[scope][n]
	return s, ok
}

// List returns the statements of a scope in grammar order.
func (c *Catalog) List(scope string) []*Statement {
	var out []*Statement
	for _, n := range c.order[scope] {
		out = append(out, c.scopes[scope][n])
	}
	return out
}

// Scopes returns all known scope names.
func (c *Catalog) Scopes() []string {
	var out []string
	for s := range c.scopes {
		out = append(out, s)
	}
	sort.Strings(out)
	return out
}

// ZoneTypes returns the zone types in the grammar (including "in-view").
func (c *Catalog) ZoneTypes() []string {
	var out []string
	for s := range c.scopes {
		if t, ok := strings.CutPrefix(s, "zone:"); ok {
			out = append(out, t)
		}
	}
	sort.Strings(out)
	return out
}

func build(grammar, tsv string) (*Catalog, error) {
	descs := map[string][2]string{}
	for _, line := range strings.Split(tsv, "\n") {
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		f := strings.Split(line, "\t")
		if len(f) != 3 {
			return nil, fmt.Errorf("bad statements line %q", line)
		}
		descs[f[0]] = [2]string{f[1], f[2]}
	}
	c := &Catalog{scopes: map[string]map[string]*Statement{}, order: map[string][]string{}}
	add := func(scope string, st *Statement) {
		if c.scopes[scope] == nil {
			c.scopes[scope] = map[string]*Statement{}
		}
		if _, dup := c.scopes[scope][st.Name]; dup {
			// The grammar lists some statements twice (e.g. alternative
			// forms); keep the first and merge the grammar text.
			c.scopes[scope][st.Name].Grammar += "\n" + st.Grammar
			return
		}
		st.Scope = scope
		if d, ok := descs[st.Name]; ok {
			st.Description = d[0]
			for _, t := range strings.Split(d[1], ",") {
				if t = strings.TrimSpace(t); t != "" {
					st.Tags = append(st.Tags, t)
				}
			}
		}
		if m, ok := managed[scope][st.Name]; ok {
			st.Managed, st.ManagedBy = true, m
		}
		if strings.HasPrefix(scope, "zone:") {
			if m, ok := zoneManaged[st.Name]; ok {
				st.Managed, st.ManagedBy = true, m
			}
		}
		st.Kind, st.Choices = classify(st.Name, st.Grammar)
		c.scopes[scope][st.Name] = st
		c.order[scope] = append(c.order[scope], st.Name)
	}

	var lines []string
	for _, l := range strings.Split(grammar, "\n") {
		if l == "" || strings.HasPrefix(l, "#") {
			continue
		}
		lines = append(lines, l)
	}
	level := func(l string) int { return (len(l) - len(strings.TrimLeft(l, " "))) / 5 }

	for i := 0; i < len(lines); i++ {
		l := lines[i]
		if level(l) != 0 {
			return nil, fmt.Errorf("unexpected indentation at %q", l)
		}
		name := firstWord(l)
		if !strings.HasSuffix(strings.TrimSpace(stripComment(l)), "{") {
			add(ScopeTop, newStatement(name, l))
			continue
		}
		// A block: collect its body.
		j := i + 1
		for j < len(lines) && level(lines[j]) > 0 {
			j++
		}
		body := lines[i+1 : j]
		closing := ""
		if j < len(lines) {
			closing = lines[j] // "};" possibly with flags
		}
		i = j
		switch name {
		case "options", "view":
			scope := name
			parseScope(body, func(st *Statement) { add(scope, st) })
			st := newStatement(name, l+"\n     ...\n"+closing)
			st.Multiple, st.Status = flags(closing)
			add(ScopeTop, st)
		case "zone":
			if len(body) == 0 {
				return nil, fmt.Errorf("empty zone grammar")
			}
			first := strings.TrimSpace(body[0])
			var zt string
			if t, ok := strings.CutPrefix(first, "type "); ok {
				zt = strings.TrimSuffix(t, ";")
				body = body[1:]
			} else if strings.HasPrefix(first, "in-view ") {
				zt = "in-view"
			} else {
				return nil, fmt.Errorf("zone grammar without type: %q", first)
			}
			scope := ZoneScope(zt)
			if c.scopes[scope] == nil {
				c.scopes[scope] = map[string]*Statement{}
			}
			parseScope(body, func(st *Statement) { add(scope, st) })
			if _, ok := c.scopes[ScopeTop]["zone"]; !ok {
				add(ScopeTop, newStatement("zone", "zone <string> [ <class> ] { ... };"))
			}
		default:
			// Other top-level blocks (logging, controls, ...) are
			// free-form statements; keep their full grammar.
			text := l + "\n" + strings.Join(body, "\n") + "\n" + closing
			st := newStatement(name, text)
			st.Multiple, st.Status = flags(closing)
			add(ScopeTop, st)
		}
	}
	// include is a directive rather than a statement but is valid at the
	// top level (and Jarl uses it for things like rndc.key).
	add(ScopeTop, &Statement{Name: "include", Grammar: "include <quoted_string>;", Multiple: true,
		Description: "Includes another configuration file at this point."})
	return c, nil
}

// parseScope parses the body of options/view/zone into statements; nested
// blocks become part of their statement's grammar.
func parseScope(body []string, emit func(*Statement)) {
	for i := 0; i < len(body); i++ {
		l := strings.TrimPrefix(body[i], "     ")
		name := firstWord(l)
		if strings.HasSuffix(strings.TrimSpace(stripComment(l)), "{") {
			j := i + 1
			for j < len(body) && strings.HasPrefix(body[j], "          ") {
				j++
			}
			text := l
			for _, sub := range body[i+1 : j] {
				text += "\n" + strings.TrimPrefix(sub, "     ")
			}
			closing := ""
			if j < len(body) {
				closing = strings.TrimPrefix(body[j], "     ")
				text += "\n" + closing
			}
			st := &Statement{Name: name, Grammar: strings.TrimSpace(text)}
			st.Multiple, st.Status = flags(closing)
			emit(st)
			i = j
			continue
		}
		emit(newStatement(name, l))
	}
}

func newStatement(name, line string) *Statement {
	st := &Statement{Name: name, Grammar: strings.TrimSpace(stripComment(line))}
	if !strings.Contains(line, "\n") {
		st.Multiple, st.Status = flags(line)
	}
	return st
}

func firstWord(l string) string {
	f := strings.Fields(l)
	if len(f) == 0 {
		return ""
	}
	return strings.TrimSuffix(f[0], ";")
}

func stripComment(l string) string {
	if i := strings.Index(l, " // "); i >= 0 {
		return l[:i]
	}
	return l
}

// flags extracts "may occur multiple times" and the status from a trailing
// grammar comment.
func flags(l string) (multiple bool, status string) {
	i := strings.Index(l, "// ")
	if i < 0 {
		return false, ""
	}
	for _, part := range strings.Split(l[i+3:], ",") {
		switch p := strings.TrimSpace(part); p {
		case "may occur multiple times":
			multiple = true
		case "deprecated", "obsolete", "experimental", "test only", "not configured", "not implemented":
			status = p
		}
	}
	return multiple, status
}

var (
	reSimple = regexp.MustCompile(`^[a-z0-9-]+ (<[a-z_]+>);$`)
	reEnum   = regexp.MustCompile(`^[a-z0-9-]+ \( ([^()]+) \);$`)
	reACL    = regexp.MustCompile(`^[a-z0-9-]+ \{ <address_match_element>; \.\.\. \};$`)
)

func classify(name, grammar string) (string, []string) {
	g := strings.TrimSpace(grammar)
	if strings.Contains(g, "\n") {
		return KindRaw, nil
	}
	if m := reSimple.FindStringSubmatch(g); m != nil {
		switch m[1] {
		case "<boolean>":
			return KindBool, nil
		case "<integer>":
			return KindInt, nil
		case "<duration>":
			return KindDuration, nil
		case "<quoted_string>":
			return KindString, nil
		case "<string>":
			return KindWord, nil
		}
		return KindRaw, nil
	}
	if reACL.MatchString(g) {
		return KindACL, nil
	}
	if m := reEnum.FindStringSubmatch(g); m != nil {
		var choices []string
		for _, alt := range strings.Split(m[1], "|") {
			alt = strings.TrimSpace(alt)
			switch {
			case alt == "<boolean>":
				choices = append(choices, "yes", "no")
			case strings.HasPrefix(alt, "<"):
				// e.g. <integer> or <quoted_string> among the choices:
				// the value is not a pure enum.
				return KindRaw, nil
			case strings.ContainsAny(alt, " []"):
				return KindRaw, nil
			default:
				choices = append(choices, alt)
			}
		}
		return KindEnum, choices
	}
	return KindRaw, nil
}

// listParam matches an optional parameter before a statement's list, such
// as "[ port <integer> ]" in allow-transfer's grammar.
var listParam = regexp.MustCompile(`\[ ([a-z0-9-]+) `)

// WrapList adds the braces to a list value given without them, for
// statements that end in a list ("allow-transfer [ port <integer> ] {
// <address_match_element>; ... }"): "10.0.0.53" becomes "{ 10.0.0.53; }",
// "port 5353 10.0.0.53; key xfer" becomes "port 5353 { 10.0.0.53; key
// xfer; }". Elements are separated by ";", "," or new lines, or by spaces
// when they are all addresses. Values with a brace, and values of other
// statements, are returned as they are.
func (st *Statement) WrapList(v string) string {
	g, _, _ := strings.Cut(st.Grammar, "\n")
	open := strings.Index(g, " {")
	if strings.Contains(v, "{") || open < 0 || !strings.HasSuffix(g, "; ... };") {
		return v
	}
	params := map[string]bool{}
	for _, m := range listParam.FindAllStringSubmatch(g[:open], -1) {
		params[m[1]] = true
	}
	fields := strings.Fields(v)
	i := 0
	for i+1 < len(fields) && params[strings.ToLower(fields[i])] {
		i += 2
	}
	head := strings.Join(fields[:i], " ")
	rest := strings.Join(fields[i:], " ")
	var elems []string
	if !strings.ContainsAny(rest, ";,\n") {
		elems = spaceElements(fields[i:])
	} else {
		for _, e := range strings.FieldsFunc(rest, func(r rune) bool { return r == ';' || r == ',' || r == '\n' }) {
			if e = strings.TrimSpace(e); e != "" {
				elems = append(elems, e)
			}
		}
	}
	if len(elems) == 0 {
		return v
	}
	list := "{ " + strings.Join(elems, "; ") + "; }"
	if head != "" {
		return head + " " + list
	}
	return list
}

// spaceElements splits list elements separated by spaces: "key NAME"
// is one element, and "port N" and "tls NAME" belong to the address
// before them (forwarders { 192.0.2.1 port 53; }).
func spaceElements(fields []string) []string {
	var out []string
	for i := 0; i < len(fields); i++ {
		f := fields[i]
		switch strings.ToLower(f) {
		case "key", "!key", "!":
			if i+1 < len(fields) {
				f += " " + fields[i+1]
				i++
			}
			if f[0] == '!' && strings.HasPrefix(strings.ToLower(f), "! key") && i+1 < len(fields) {
				f += " " + fields[i+1]
				i++
			}
		case "-":
			// A range with spaces around the dash: 10.0.0.1 - 10.0.0.9.
			if len(out) > 0 && i+1 < len(fields) {
				out[len(out)-1] += " - " + fields[i+1]
				i++
				continue
			}
		case "port", "tls":
			if len(out) > 0 && i+1 < len(fields) {
				out[len(out)-1] += " " + f + " " + fields[i+1]
				i++
				continue
			}
		}
		out = append(out, f)
	}
	return out
}