/**
* Minimal parser for Vitest `.snap` files.
*
* A .snap file is a JavaScript module that assigns template-literal
* strings to numbered keys, for example:
*
* exports[`scenario 1 — day 0 1`] = `""`;
*
* We only need to extract { key -> string } pairs. The values produced
* by `toMatchSnapshot(string)` are themselves JSON-stringified, i.e.
* the stored template literal contains a double-quoted JSON string.
* parseSnapFile returns the underlying string (JSON-decoded) per key.
*/
import { existsSync, readFileSync } from 'node:fs'
/**
* Parses a Vitest .snap file and returns a map of snapshot keys to
* their decoded string values. Non-string snapshots are returned as raw
* template-literal bodies (we only use string snapshots in this project,
* but the fallback keeps the parser forgiving).
*/
export function parseSnapFile(path: string): Map {
const map = new Map()
if (!existsSync(path)) return map
const source = readFileSync(path, 'utf8')
// Match: exports[``] = ``;
// Key may contain backticks only if escaped (\`); body likewise.
// Snapshots end with `;` on its own line, which is our terminator.
const pattern = /exports\[`((?:\\[\s\S]|[^\\`])*)`\]\s*=\s*`((?:\\[\s\S]|[^\\`])*)`;/g
let match: RegExpExecArray | null
while ((match = pattern.exec(source)) != null) {
const rawKey = match[1] ?? ''
const rawBody = match[2] ?? ''
const key = unescapeTemplate(rawKey)
const body = unescapeTemplate(rawBody)
map.set(key, decodeSnapshotBody(body))
}
return map
}
function unescapeTemplate(s: string): string {
return s
.replace(/\\`/g, '`')
.replace(/\\\$/g, '$')
.replace(/\\\\/g, '\\')
}
/**
* Vitest's pretty-format serializer wraps plain-string snapshots in
* double quotes but, unlike JSON, does not escape the inner characters
* (so `id="finland-large"` remains literally `id="finland-large"`).
* Template-literal syntax on the outside takes care of backticks and
* `${}` sequences, but the contents of the quoted string are otherwise
* byte-for-byte identical to the value passed to toMatchSnapshot.
*
* We therefore strip the outer double quotes without any unescape step.
* Non-string snapshots (objects / arrays) are returned as raw pretty-JS
* and never consumed by the review HTML pipeline.
*/
function decodeSnapshotBody(body: string): string {
const trimmed = body.trim()
if (trimmed.length >= 2 && trimmed.startsWith('"') && trimmed.endsWith('"')) {
return trimmed.slice(1, -1)
}
return trimmed
}