package doccontent

import (
	"crypto/sha256"
	"encoding/hex"
	"strings"

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

// CanonicalizeMarkdown applies LF, UTF-8 NFC, and a single trailing newline.
// It must not trim trailing spaces or tabs: two trailing spaces are Markdown hard breaks.
func CanonicalizeMarkdown(raw string) string {
	s := strings.ReplaceAll(raw, "\r\n", "\n")
	s = strings.ReplaceAll(s, "\r", "\n")
	s = norm.NFC.String(s)
	if s != "" && !strings.HasSuffix(s, "\n") {
		s += "\n"
	}
	return s
}

// LegacyDestructiveCanonicalizeMarkdown reproduces the pre-fix canonicalizer that
// stripped per-line trailing spaces/tabs. Used only to classify historical drift.
func LegacyDestructiveCanonicalizeMarkdown(raw string) string {
	s := strings.ReplaceAll(raw, "\r\n", "\n")
	s = strings.ReplaceAll(s, "\r", "\n")
	s = norm.NFC.String(s)
	lines := strings.Split(s, "\n")
	for i, line := range lines {
		lines[i] = strings.TrimRightFunc(line, func(r rune) bool {
			return r == ' ' || r == '\t'
		})
	}
	s = strings.Join(lines, "\n")
	if s != "" && !strings.HasSuffix(s, "\n") {
		s += "\n"
	}
	return s
}

func SHA256Hex(content string) string {
	sum := sha256.Sum256([]byte(content))
	return hex.EncodeToString(sum[:])
}