jarl/internal/namedconf/ast.go

package namedconf

import (
	"fmt"
	"strings"
)

// Value is a single word or quoted string.
type Value struct {
	Text   string // unescaped text
	Quoted bool
	Pos    Pos
}

// Block is a brace-enclosed list of statements.
type Block struct {
	Stmts []*Stmt
	Pos   Pos
}

// Item is one element of a statement: either a value, a "!" negation
// marker, or a block.
type Item struct {
	Value *Value
	Block *Block
	Bang  bool
}

// Stmt is a statement: a sequence of items terminated by a semicolon.
type Stmt struct {
	Items []Item
	Pos   Pos
}

// Keyword returns the statement's first word, lowercased, or "" if the
// statement doesn't start with a value.
func (s *Stmt) Keyword() string {
	if len(s.Items) == 0 || s.Items[0].Value == nil {
		return ""
	}
	return strings.ToLower(s.Items[0].Value.Text)
}

// Arg returns the text of the n-th value after the keyword (0-based), or "".
func (s *Stmt) Arg(n int) string {
	idx := 0
	for _, it := range s.Items[1:] {
		if it.Value == nil {
			break
		}
		if idx == n {
			return it.Value.Text
		}
		idx++
	}
	return ""
}

// Values returns the texts of the leading values after the keyword, up to
// the first block.
func (s *Stmt) Values() []string {
	var out []string
	for _, it := range s.Items[1:] {
		if it.Value == nil {
			break
		}
		out = append(out, it.Value.Text)
	}
	return out
}

// FirstBlock returns the statement's first block, or nil.
func (s *Stmt) FirstBlock() *Block {
	for _, it := range s.Items {
		if it.Block != nil {
			return it.Block
		}
	}
	return nil
}

// Rest returns a copy of the statement without its keyword.
func (s *Stmt) Rest() *Stmt {
	if len(s.Items) == 0 {
		return &Stmt{Pos: s.Pos}
	}
	return &Stmt{Items: append([]Item(nil), s.Items[1:]...), Pos: s.Pos}
}

// Find returns the statements in stmts with the given keyword.
func Find(stmts []*Stmt, keyword string) []*Stmt {
	var out []*Stmt
	for _, s := range stmts {
		if s.Keyword() == keyword {
			out = append(out, s)
		}
	}
	return out
}

// FindOne returns the first statement with the given keyword, or nil.
func FindOne(stmts []*Stmt, keyword string) *Stmt {
	for _, s := range stmts {
		if s.Keyword() == keyword {
			return s
		}
	}
	return nil
}

// NewStmt builds a statement from values: strings become unquoted words and
// *Block become blocks. Use Q to make a quoted string.
func NewStmt(items ...any) *Stmt {
	st := &Stmt{}
	for _, it := range items {
		switch v := it.(type) {
		case string:
			st.Items = append(st.Items, Item{Value: &Value{Text: v}})
		case Quoted:
			st.Items = append(st.Items, Item{Value: &Value{Text: string(v), Quoted: true}})
		case *Block:
			st.Items = append(st.Items, Item{Block: v})
		case Item:
			st.Items = append(st.Items, v)
		default:
			panic(fmt.Sprintf("namedconf.NewStmt: unsupported item %T", it))
		}
	}
	return st
}

// Quoted marks a string for NewStmt as a quoted string.
type Quoted string

// NewBlock builds a block from statements.
func NewBlock(stmts ...*Stmt) *Block { return &Block{Stmts: stmts} }

// Clone returns a deep copy of the statement.
func (s *Stmt) Clone() *Stmt {
	out := &Stmt{Pos: s.Pos, Items: make([]Item, len(s.Items))}
	for i, it := range s.Items {
		switch {
		case it.Value != nil:
			v := *it.Value
			out.Items[i] = Item{Value: &v}
		case it.Block != nil:
			b := &Block{Pos: it.Block.Pos}
			for _, st := range it.Block.Stmts {
				b.Stmts = append(b.Stmts, st.Clone())
			}
			out.Items[i] = Item{Block: b}
		default:
			out.Items[i] = it
		}
	}
	return out
}