package text

import (
	"strings"

	"golang.org/x/text/unicode/norm"
)

// source.go: the canonical form of a SOURCE text. Applied once at ingest and again by the
// renderer before hashing, so the same book text produces the same request_hash regardless of
// the editor, the OS line endings or the Unicode composition it was authored with.

// NormalizeSource canonicalizes the source chunk so the request-hash is stable
// across editors and operating systems (review finding): strip a UTF-8 BOM,
// CRLF/CR → LF, Unicode NFC, trim surrounding whitespace. Without this a file
// saved in a different editor (BOM) or on Windows (CRLF) would produce a different
// hash and silently re-translate a book already paid for.
func NormalizeSource(s string) string {
	s = strings.TrimPrefix(s, "\uFEFF") // UTF-8 BOM
	s = strings.ReplaceAll(s, "\r\n", "\n")
	s = strings.ReplaceAll(s, "\r", "\n")
	// Replace invalid UTF-8 with U+FFFD exactly ONCE, here, so all downstream
	// segmentation sees byte-valid text. Without this the chunker diverges from itself: its
	// []rune-path over sentences (chunker.go) would silently replace a stray byte with U+FFFD,
	// while the string path over paragraphs would keep it raw — a size-dependent corruption
	// leaking into {{text}} and request_hash (external review #3). This is an ingest rule →
	// covered by chunkerVersion (a deliberate re-translation, not a silent one).
	s = strings.ToValidUTF8(s, "\uFFFD")
	s = norm.NFC.String(s)
	return strings.TrimSpace(s)
}