#!/usr/bin/env bun
/**
 * Regenerates src/<feature>/index.ts barrels.
 */

import {
    existsSync,
    readdirSync,
    readFileSync,
    statSync,
    writeFileSync,
} from "node:fs";
import { join } from "node:path";

const PACKAGES_DIR = "packages";

interface NamedExports {
    readonly values: readonly string[];
    readonly types: readonly string[];
    readonly hasDefault: boolean;
}

function parseExports(implPath: string): NamedExports {
    const src = readFileSync(implPath, "utf8");
    const values = new Set<string>();
    const types = new Set<string>();
    let hasDefault = false;

    const cleaned = src
        .replace(/\/\*[\s\S]*?\*\//g, "")
        .replace(/\/\/.*$/gm, "");

    // Captures: 1 = "default" or "", 2 = kind, 3 = name.
    const re =
        /\bexport\s+(default\s+)?(?:abstract\s+)?(?:declare\s+)?(?:async\s+)?(const|let|var|function|class|enum|interface|type)\s+([A-Za-z_$][\w$]*)/g;
    let match: RegExpExecArray | null;
    while ((match = re.exec(cleaned)) !== null) {
        const isDefault = Boolean(match[1]);
        const kind = match[2] as string;
        const name = match[3] as string;
        if (isDefault) {
            hasDefault = true;
            // `export default class X {}` also creates a named binding X locally,
            // but the named export only happens through the default slot.
            continue;
        }
        if (kind === "type" || kind === "interface") types.add(name);
        else values.add(name);
    }

    // Detect bare `export default Identifier;`.
    const bareDefaultRe = /\bexport\s+default\s+([A-Za-z_$][\w$]*)\s*;/g;
    while ((match = bareDefaultRe.exec(cleaned)) !== null) {
        hasDefault = true;
    }

    const listRe = /export\s+(type\s+)?\{([^}]+)\}/g;
    while ((match = listRe.exec(cleaned)) !== null) {
        const blockIsType = Boolean(match[1]);
        const body = match[2] as string;
        for (const piece of body.split(",")) {
            const trimmed = piece.trim();
            if (!trimmed) continue;
            const typeM = trimmed.match(/^type\s+(.+)$/);
            const inner = typeM ? (typeM[1] as string) : trimmed;
            const asM = inner.match(
                /^([A-Za-z_$][\w$]*)\s+as\s+([A-Za-z_$][\w$]*)$/
            );
            const name = asM ? (asM[2] as string) : inner;
            if (!/^[A-Za-z_$][\w$]*$/.test(name)) continue;
            if (blockIsType || typeM) types.add(name);
            else values.add(name);
        }
    }

    values.delete("default");

    return {
        values: [...values].sort(),
        types: [...types].sort(),
        hasDefault,
    };
}

function buildBarrel(feature: string, exports: NamedExports): string {
    const lines: string[] = [];
    if (exports.types.length > 0) {
        lines.push("export type {");
        for (const t of exports.types) lines.push(`    ${t},`);
        lines.push(`} from "./${feature}.js";`);
    }
    if (exports.values.length > 0 || exports.hasDefault) {
        const names = [...exports.values];
        if (exports.hasDefault) names.push("default");
        lines.push("export {");
        for (const v of names) lines.push(`    ${v},`);
        lines.push(`} from "./${feature}.js";`);
    }
    if (lines.length === 0) lines.push(`export {} from "./${feature}.js";`);
    lines.push("");
    return lines.join("\n");
}

function listPackages(): readonly string[] {
    const out: string[] = [];
    for (const cat of readdirSync(PACKAGES_DIR)) {
        const catDir = join(PACKAGES_DIR, cat);
        if (!statSync(catDir).isDirectory()) continue;
        for (const plugin of readdirSync(catDir)) {
            const pluginDir = join(catDir, plugin);
            if (!statSync(pluginDir).isDirectory()) continue;
            for (const pkg of readdirSync(pluginDir)) {
                const pkgDir = join(pluginDir, pkg);
                if (!statSync(pkgDir).isDirectory()) continue;
                if (existsSync(join(pkgDir, "src"))) out.push(pkgDir);
            }
        }
    }
    return out;
}

function main(): void {
    let touched = 0;
    for (const pkgDir of listPackages()) {
        const srcDir = join(pkgDir, "src");
        for (const entry of readdirSync(srcDir)) {
            const featureDir = join(srcDir, entry);
            try {
                if (!statSync(featureDir).isDirectory()) continue;
            } catch {
                continue;
            }
            const impl = join(featureDir, `${entry}.ts`);
            const indexFile = join(featureDir, "index.ts");
            if (!existsSync(impl) || !existsSync(indexFile)) continue;
            const current = readFileSync(indexFile, "utf8");
            const onlyTouchesImpl = current
                .split("\n")
                .filter((l) => l.includes("from "))
                .every((l) => l.includes(`from "./${entry}.js"`));
            if (!onlyTouchesImpl) continue;
            const exports = parseExports(impl);
            const barrel = buildBarrel(entry, exports);
            if (barrel !== current) {
                writeFileSync(indexFile, barrel);
                console.log(`REGEN ${indexFile}`);
                touched++;
            }
        }
    }
    console.log(`\nRegenerated ${touched} barrels.`);
}

main();