/**
* @fileoverview Git-Compatible Hash Utilities
*
* FORMAT: sha1("blob " + size + "\0" + content) - matches `git hash-object`
* USED BY: cat | write | ls | edit | conflict detection | sync check
* HASH ON: WRAPPED content (full file with CommonJS), NOT unwrapped user code
* NORMALIZATION: CRLF→LF | UTF-8 BOM stripped | consistent across all tools
*/
import { createHash } from 'crypto';
/**
* Compute Git-compatible SHA-1 checksum for content
*
* Uses Git's blob format: sha1("blob " + <size> + "\0" + <content>)
* This matches the output of `git hash-object <file>`
*
* IMPORTANT: For GAS files, content should be the FULL file as stored in GAS
* (including CommonJS wrappers), NOT unwrapped user code.
*
* @param content - Content as string (normalized to LF line endings, UTF-8 BOM stripped)
* @returns Git-compatible SHA-1 hash as 40-character hex string
*/
export function computeGitSha1(content: string): string {
// Normalize content for consistent hashing:
// 1. Normalize line endings to LF (Unix style)
// 2. Strip UTF-8 BOM if present
const normalizedContent = normalizeForHashing(content);
const size = Buffer.byteLength(normalizedContent, 'utf8');
const header = `blob ${size}\0`;
return createHash('sha1')
.update(header)
.update(normalizedContent, 'utf8')
.digest('hex');
}
/**
* Compute SHA-256 hash for content
*
* @param content - Content as string
* @returns SHA-256 hash as 64-character hex string
*/
export function computeSha256(content: string): string {
const normalizedContent = normalizeForHashing(content);
return createHash('sha256')
.update(normalizedContent, 'utf8')
.digest('hex');
}
/**
* Compute MD5 hash for content (legacy compatibility)
*
* @param content - Content as string
* @returns MD5 hash as 32-character hex string
*/
export function computeMd5(content: string): string {
const normalizedContent = normalizeForHashing(content);
return createHash('md5')
.update(normalizedContent, 'utf8')
.digest('hex');
}
/**
* Normalize content for consistent hashing across platforms
*
* - Normalizes CRLF to LF (consistent with Git)
* - Strips UTF-8 BOM if present
* - Does NOT modify trailing newlines (document behavior)
*/
export function normalizeForHashing(content: string): string {
// Strip UTF-8 BOM if present (0xEF 0xBB 0xBF = \uFEFF)
let normalized = content.startsWith('\uFEFF') ? content.slice(1) : content;
// Normalize CRLF to LF (Windows -> Unix line endings)
normalized = normalized.replace(/\r\n/g, '\n');
return normalized;
}
/**
* Validate that a string looks like a valid Git SHA-1 hash
*
* @param hash - String to validate
* @returns true if hash is 40 lowercase hex characters
*/
export function isValidGitSha1(hash: string): boolean {
return /^[a-f0-9]{40}$/.test(hash);
}
/**
* Compare two hashes for equality (case-insensitive)
*
* @param hash1 - First hash
* @param hash2 - Second hash
* @returns true if hashes are equal
*/
export function hashesEqual(hash1: string, hash2: string): boolean {
return hash1.toLowerCase() === hash2.toLowerCase();
}
