#!/usr/bin/env bun

/**
 * generate-subcategory-readmes — for every `packages/<category>/<subcategory>/`
 * folder, write a `README.md` containing:
 *
 *   1. The contents of `packages/<category>/<subcategory>/_intro.md` verbatim,
 *      if present.
 *   2. An auto-generated table of packages in that subcategory, each row
 *      linking to the package's own README and showing the first-paragraph
 *      description of that README as the second column.
 *
 * Re-runs are idempotent. The auto section is enclosed in
 * `<!-- begin:auto-docs -->`…`<!-- end:auto-docs -->` markers; the intro
 * file (when present) is dropped in above.
 *
 * Usage:
 *   bun scripts/generate-subcategory-readmes.ts            # rewrite
 *   bun scripts/generate-subcategory-readmes.ts --check    # exit 1 on drift
 */

import { type Dirent, readdirSync, writeFileSync } from "node:fs";
import { basename, join } from "node:path";
import { CONFIG } from "./lib/config.js";
import {
    AUTO_MARKER_BEGIN,
    AUTO_MARKER_END,
    firstBodyParagraph,
    isDirectorySafe,
    tryRead,
} from "./lib/doc-tree.js";

const ROOT = CONFIG.paths.root;
const PACKAGES_ROOT = join(ROOT, CONFIG.paths.packagesRoot);
const PKG_PREFIX = "@suaveplan/";

interface SubcategoryPackage {
    name: string;
    description: string;
    relPath: string;
}

function describePackageReadme(readmePath: string, fallback: string): string {
    const content = tryRead(readmePath) ?? "";
    if (!content) return fallback;
    return firstBodyParagraph(content, 160) || fallback;
}

function escapeCell(s: string): string {
    return s.replace(/\|/g, "\\|").replace(/\n+/g, " ").trim();
}

function readSuaveplanPackage(
    pkgDir: string,
    relPath: string
): SubcategoryPackage | null {
    const pkgRaw = tryRead(join(pkgDir, "package.json"));
    if (!pkgRaw) return null;
    let pkg: { name?: string; description?: string };
    try {
        pkg = JSON.parse(pkgRaw) as { name?: string; description?: string };
    } catch {
        return null;
    }
    if (!pkg.name?.startsWith(PKG_PREFIX)) return null;
    const shortName = pkg.name.slice(PKG_PREFIX.length);
    const description = describePackageReadme(
        join(pkgDir, "README.md"),
        (pkg.description ?? "").trim()
    );
    return { name: shortName, description, relPath };
}

function collectSubcategoryPackages(subcategoryDir: string): SubcategoryPackage[] {
    const out: SubcategoryPackage[] = [];
    let entries: Dirent[];
    try {
        entries = readdirSync(subcategoryDir, { withFileTypes: true });
    } catch {
        return out;
    }
    for (const entry of entries) {
        if (!entry.isDirectory()) continue;
        if (entry.name.startsWith(".")) continue;
        const pkgDir = join(subcategoryDir, entry.name);
        const record = readSuaveplanPackage(pkgDir, entry.name);
        if (record !== null) out.push(record);
    }
    out.sort((a, b) => a.name.localeCompare(b.name));
    return out;
}

function renderAutoBlock(
    subcategoryName: string,
    packages: readonly SubcategoryPackage[]
): string {
    const rows = packages
        .map((p) => {
            const link = `[\`@suaveplan/${p.name}\`](./${p.relPath}/README.md)`;
            return `| ${link} | ${escapeCell(p.description || "—")} |`;
        })
        .join("\n");
    const lines = [
        `## Packages in \`${subcategoryName}\``,
        "",
        `${packages.length} package${packages.length === 1 ? "" : "s"}.`,
        "",
        "| Package | Description |",
        "|---|---|",
        rows,
    ];
    return lines.join("\n");
}

function buildReadme(
    subcategoryName: string,
    intro: string | undefined,
    packages: readonly SubcategoryPackage[]
): string {
    const introBody = intro?.trim()
        ? intro.trim()
        : `Auto-generated index of the \`@suaveplan/*\` packages under this directory. Drop a hand-authored \`_intro.md\` here to replace this default header.`;
    const header = [`# \`${subcategoryName}\``, "", introBody].join("\n");
    const auto = renderAutoBlock(subcategoryName, packages);
    return `${header}\n\n${AUTO_MARKER_BEGIN}\n${auto}\n${AUTO_MARKER_END}\n`;
}

interface CliOptions {
    check: boolean;
}

function parseArgs(argv: readonly string[]): CliOptions {
    let check = false;
    for (const arg of argv) {
        if (arg === "--check") check = true;
        else throw new Error(`Unknown flag: ${arg}`);
    }
    return { check };
}

function main(): void {
    let options: CliOptions;
    try {
        options = parseArgs(process.argv.slice(2));
    } catch (err) {
        console.error(err instanceof Error ? err.message : String(err));
        process.exit(1);
    }

    if (!isDirectorySafe(PACKAGES_ROOT)) {
        console.error(`Packages root not found: ${PACKAGES_ROOT}`);
        process.exit(2);
    }

    let categoryEntries: Dirent[];
    try {
        categoryEntries = readdirSync(PACKAGES_ROOT, { withFileTypes: true });
    } catch (err) {
        console.error(err instanceof Error ? err.message : String(err));
        process.exit(2);
    }

    let updated = 0;
    let unchanged = 0;
    let empty = 0;

    for (const cat of categoryEntries) {
        if (!cat.isDirectory()) continue;
        if (cat.name.startsWith(".")) continue;
        const categoryDir = join(PACKAGES_ROOT, cat.name);

        let subcategoryEntries: Dirent[];
        try {
            subcategoryEntries = readdirSync(categoryDir, { withFileTypes: true });
        } catch {
            continue;
        }

        for (const sub of subcategoryEntries) {
            if (!sub.isDirectory()) continue;
            if (sub.name.startsWith(".")) continue;
            const subcategoryDir = join(categoryDir, sub.name);
            const packages = collectSubcategoryPackages(subcategoryDir);
            if (packages.length === 0) {
                empty++;
                continue;
            }
            const introPath = join(subcategoryDir, "_intro.md");
            const intro = tryRead(introPath);
            const next = buildReadme(basename(subcategoryDir), intro, packages);
            const readmePath = join(subcategoryDir, "README.md");
            const current = tryRead(readmePath) ?? "";
            if (current === next) {
                unchanged++;
                continue;
            }
            if (!options.check) writeFileSync(readmePath, next);
            updated++;
        }
    }

    console.log("");
    console.log(`✏️  Updated:    ${updated}`);
    console.log(`⏭️  Unchanged:  ${unchanged}`);
    if (empty > 0) console.log(`⚠️  Empty:      ${empty}`);

    if (options.check && updated > 0) {
        console.error("");
        console.error("Drift detected — run without --check to rewrite.");
        process.exit(1);
    }
    process.exit(0);
}

main();