import { execSync } from "node:child_process";
import fs from "node:fs";
import path from "node:path";
import crypto from "node:crypto";

const ROOT = process.cwd();
const DOCS_DIR = path.resolve(ROOT, "docs");
const OUT_DIR = path.resolve(ROOT, ".vitepress/.generated");
const OUT_FILE = path.join(OUT_DIR, "contributors.json");

function walk(dir) {
    const out = [];
    for (const name of fs.readdirSync(dir)) {
        const p = path.join(dir, name);
        const st = fs.statSync(p);
        if (st.isDirectory()) out.push(...walk(p));
        else if (p.endsWith(".md")) out.push(p);
    }
    return out;
}

function md5(s) {
    return crypto.createHash("md5").update(s.trim().toLowerCase()).digest("hex");
}

function parseGithubUsernameFromNoreply(email = "") {
    // 1) 12345+username@users.noreply.github.com
    // 2) username@users.noreply.github.com
    const m1 = email.match(/^[^+]+\+([^@]+)@users\.noreply\.github\.com$/i);
    if (m1?.[1]) return m1[1];
    const m2 = email.match(/^([^@]+)@users\.noreply\.github\.com$/i);
    if (m2?.[1]) return m2[1];
    return null;
}

function avatarUrlFor(email = "") {
    const gh = parseGithubUsernameFromNoreply(email);
    if (gh) {
        return `https://unavatar.io/github/${encodeURIComponent(gh)}`;
    }
    if (email) {
        return `https://www.gravatar.com/avatar/${md5(email)}?d=identicon&s=64`;
    }
    return `https://www.gravatar.com/avatar/?d=identicon&s=64`;
}

function gitContributors(fileAbsPath) {
    const rel = path.relative(process.cwd(), fileAbsPath).replaceAll("\\", "/");
    let raw = "";
    try {
        raw = execSync(`git log --follow --format="%aN|%aE" -- "${rel}"`, {
            encoding: "utf8",
        });
    } catch {
        return [];
    }

    const map = new Map();
    raw
        .split("\n")
        .map((s) => s.trim())
        .filter(Boolean)
        .forEach((line) => {
            const [name, email] = line.split("|");
            const key = (email || name || "").toLowerCase();
            if (!map.has(key)) {
                const github = parseGithubUsernameFromNoreply(email);
                map.set(key, {
                    name,
                    email,
                    github,
                    avatarUrl: avatarUrlFor(email),
                    commits: 0,
                });
            }
            map.get(key).commits += 1;
        });

    return [...map.values()].sort((a, b) => b.commits - a.commits);
}

const files = walk(DOCS_DIR);
const data = {};

for (const abs of files) {
    const relToDocs = path.relative(DOCS_DIR, abs).replaceAll("\\", "/");
    let route = "/" + relToDocs.replace(/\.md$/, "");
    route = route.replace(/\/index$/, "/"); // docs/a/index.md -> /a/
    data[route] = gitContributors(abs);
}

fs.mkdirSync(OUT_DIR, { recursive: true });
fs.writeFileSync(OUT_FILE, JSON.stringify(data, null, 2), "utf8");
console.log(`Generated contributors for ${files.length} pages -> ${OUT_FILE}`);