package understand

import (
	"regexp"
	"strings"
)

// MatchPerson returns the household name from people that appears as a whole
// word in the question, or "" when no name matches.
//
// It is deterministic: no LLM is in this path (AGENTS.md rule 4). The Hub uses
// it to set the /ask person field from the question when the caller did not
// name a person. A caller-supplied person always wins; the caller does not call
// this function in that case.
//
// The match is case-insensitive and whole-word, so "harry" matches "What does
// Harry have on today?" but not "harrypotter". The matched name is returned as
// the project published it, trimmed.
func MatchPerson(question string, people []string) string {
	if strings.TrimSpace(question) == "" || len(people) == 0 {
		return ""
	}
	q := strings.ToLower(question)
	for _, p := range people {
		name := strings.TrimSpace(p)
		if name == "" {
			continue
		}
		// \b is a word boundary in Go's RE2. QuoteMeta keeps a name that
		// holds a regexp character literal.
		re := regexp.MustCompile(`\b` + regexp.QuoteMeta(strings.ToLower(name)) + `\b`)
		if re.MatchString(q) {
			return name
		}
	}
	return ""
}