/**

* Utilities for reading and writing NpgsqlRest JSONC config files.

* These files have // comment headers before the JSON body.

*/

/**

* Separate the // comment header from the JSON body.

* Header = all leading lines that are empty or start with //.

*/

export function splitHeaderAndJson(text: string): { header: string; json: string } {

const lines = text.split("\n");

let headerEnd = 0;

for (let i = 0; i < lines.length; i++) {

const trimmed = lines[i].trim();

if (trimmed === "" || trimmed.startsWith("//")) {

headerEnd = i + 1;

} else {

break;

}

}

const header = lines.slice(0, headerEnd).join("\n");

const json = lines.slice(headerEnd).join("\n");

return { header: header ? header + "\n" : "", json };

}

/**

* Strip // and block comments from JSON text (respects string literals).

*/

export function stripJsonComments(text: string): string {

let result = "";

let i = 0;

const len = text.length;

while (i < len) {

// String literal

if (text[i] === '"') {

result += '"';

i++;

while (i < len && text[i] !== '"') {

if (text[i] === "\\") {

result += text[i] + (text[i + 1] ?? "");

i += 2;

} else {

result += text[i];

i++;

}

}

if (i < len) {

result += '"';

i++;

}

continue;

}

// Line comment

if (text[i] === "/" && text[i + 1] === "/") {

while (i < len && text[i] !== "\n") i++;

continue;

}

// Block comment

if (text[i] === "/" && text[i + 1] === "*") {

i += 2;

while (i < len && !(text[i] === "*" && text[i + 1] === "/")) i++;

i += 2;

continue;

}

result += text[i];

i++;

}

return result;

}

/**

* Read a JSONC config file. Returns parsed data and the original header,

* or null if the file doesn't exist.

*/

export async function readJsonConfig(

path: string,

): Promise<{ data: Record<string, unknown>; header: string } | null> {

const file = Bun.file(path);

if (!(await file.exists())) return null;

const text = await file.text();

const { header, json } = splitHeaderAndJson(text);

const clean = stripJsonComments(json);

const data = JSON.parse(clean) as Record<string, unknown>;

return { data, header };

}

/**

* Serialize a JSON value to JSONC with // comments above keys that have descriptions.

* Comments use the NpgsqlRest convention: // wrapped above and below the description text.

*/

function serializeValue(

value: unknown,

descriptions: Record<string, string>,

depth: number,

path: string,

): string {

if (value === null) return "null";

if (typeof value === "boolean" || typeof value === "number") return String(value);

if (typeof value === "string") return JSON.stringify(value);

if (Array.isArray(value)) {

if (value.length === 0) return "[]";

const pad = " ".repeat(depth + 1);

const outer = " ".repeat(depth);

const items = value.map((v) =>

`${pad}${serializeValue(v, descriptions, depth + 1, path)}`,

);

return `[\n${items.join(",\n")}\n${outer}]`;

}

if (typeof value === "object" && value !== null) {

const entries = Object.entries(value as Record<string, unknown>);

if (entries.length === 0) return "{}";

const pad = " ".repeat(depth + 1);

const outer = " ".repeat(depth);

const lines: string[] = [];

for (let i = 0; i < entries.length; i++) {

const [key, val] = entries[i];

const keyPath = path ? `${path}.${key}` : key;

const desc = descriptions[keyPath];

const comma = i < entries.length - 1 ? "," : "";

if (desc) {

lines.push(`${pad}//`);

for (const line of desc.split("\n")) {

lines.push(`${pad}// ${line}`);

}

lines.push(`${pad}//`);

}

const valStr = serializeValue(val, descriptions, depth + 1, keyPath);

lines.push(`${pad}${JSON.stringify(key)}: ${valStr}${comma}`);

}

return `{\n${lines.join("\n")}\n${outer}}`;

}

return JSON.stringify(value);

}

export function serializeJsonc(

data: Record<string, unknown>,

descriptions: Record<string, string>,

): string {

return serializeValue(data, descriptions, 0, "") + "\n";

}

/**

* Write a JSON config file, prepending the original comment header.

* If descriptions are provided, writes JSONC with inline // comments.

* Pretty-prints with 2-space indentation.

*/

export async function writeJsonConfig(

path: string,

data: Record<string, unknown>,

header: string,

descriptions?: Record<string, string>,

): Promise<void> {

const body = descriptions

? serializeJsonc(data, descriptions)

: JSON.stringify(data, null, 2) + "\n";

await Bun.write(path, header + body);

}