package preproc

import (
	"strings"
	"unicode/utf8"

	"github.com/armon/go-radix"
)

type DefineList struct {
	tree *radix.Tree
}

func NewDefineList() *DefineList { return &DefineList{tree: radix.New()} }

// Add inserts or updates a define->value mapping.
func (d *DefineList) Add(define, value string) { d.tree.Insert(define, value) }

// Delete removes a define. Returns true if it existed.
func (d *DefineList) Delete(define string) bool {
	_, ok := d.tree.Delete(define)
	return ok
}

// Defined reports whether a define exists.
func (d *DefineList) Defined(s string) bool {
	_, ok := d.tree.Get(s)
	return ok
}

// typed wrapper to avoid type assertions sprinkled in hot code
func (d *DefineList) longestPrefixString(s string) (key string, val string, ok bool) {
	k, v, ok := d.tree.LongestPrefix(s)
	if !ok {
		return "", "", false
	}
	return k, v.(string), true
}

// ReplaceDefines performs a single-pass, longest-prefix replacement.
// Case-sensitive. Matches anywhere. No recursive re-expansion.
func (d *DefineList) ReplaceDefines(s string) string {
	var b strings.Builder
	b.Grow(len(s)) // baseline; grows if expansions occur

	for i := 0; i < len(s); {
		if key, val, ok := d.longestPrefixString(s[i:]); ok && key != "" {
			b.WriteString(val)
			i += len(key) // advance by matched bytes (UTF-8-safe)
			continue
		}
		_, size := utf8.DecodeRuneInString(s[i:])
		b.WriteString(s[i : i+size])
		i += size
	}
	return b.String()
}