#!/usr/bin/env bun
/**
 * Fails when an implementation+test pair lives flat at a package's `src/`
 * root instead of inside a feature folder.
 *
 * CLAUDE.md §"Package Structure" mandates the 5-files-per-feature layout:
 *
 *   src/<feature>/
 *     index.ts
 *     <feature>.ts
 *     <feature>.test.ts
 *     <feature>.types.ts
 *     <feature>.md
 *
 * The only flat exceptions allowed at `src/` root are:
 *   - `index.ts` (package barrel)
 *   - `types/`, `utils/`, `constants/` (per the documented exemption list)
 *
 * Any other `<name>.ts` paired with `<name>.test.ts` directly under `src/`
 * (without a `<name>/` folder) is a layout violation and fails CI.
 *
 * Exit codes: 0 = clean, 1 = at least one violation.
 */

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

const PACKAGES_DIR = "packages";
const ROOT_FLAT_EXEMPT = new Set(["index.ts"]);
const ROOT_DIR_EXEMPT = new Set(["types", "utils", "constants"]);

interface Violation {
    readonly pkg: string;
    readonly src: string;
    readonly feature: string;
    readonly files: readonly string[];
}

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;
                const srcDir = join(pkgDir, "src");
                try {
                    if (statSync(srcDir).isDirectory()) out.push(pkgDir);
                } catch {
                    // no src/ — skip
                }
            }
        }
    }
    return out;
}

function checkPackage(pkgDir: string): Violation[] {
    const srcDir = join(pkgDir, "src");
    const entries = readdirSync(srcDir);
    const featuresFound = new Map<string, string[]>();

    for (const name of entries) {
        const full = join(srcDir, name);
        if (statSync(full).isDirectory()) continue;
        if (ROOT_FLAT_EXEMPT.has(name)) continue;
        const match = name.match(/^(.+?)(\.test|\.types|\.md|)\.(ts|tsx|md)$/);
        if (!match) continue;
        const feature = match[1] as string;
        const list = featuresFound.get(feature) ?? [];
        list.push(name);
        featuresFound.set(feature, list);
    }

    const violations: Violation[] = [];
    for (const [feature, files] of featuresFound) {
        const hasImpl = files.some((f) => f === `${feature}.ts`);
        const hasTest = files.some((f) => f === `${feature}.test.ts`);
        if (hasImpl && hasTest) {
            violations.push({
                pkg: pkgDir,
                src: srcDir,
                feature,
                files,
            });
        }
    }
    return violations;
}

function main(): void {
    const pkgs = listPackages();
    const allViolations: Violation[] = [];
    for (const pkg of pkgs) {
        allViolations.push(...checkPackage(pkg));
    }
    if (allViolations.length === 0) {
        console.log(
            `OK ${pkgs.length} packages: every <feature>.ts + <feature>.test.ts pair lives in a feature folder.`
        );
        return;
    }
    console.error(
        `Found ${allViolations.length} layout violation${allViolations.length === 1 ? "" : "s"}:\n`
    );
    for (const v of allViolations) {
        console.error(`FAIL ${v.pkg}`);
        console.error(
            `    feature \`${v.feature}\` is flat at src/ root; should live in src/${v.feature}/`
        );
        for (const f of v.files) {
            console.error(`        - src/${f}`);
        }
    }
    console.error(
        `\nCLAUDE.md §"Package Structure" mandates 5-files-per-feature layout. Only ${[...ROOT_DIR_EXEMPT].map((d) => `\`${d}/\``).join(", ")} dirs and \`index.ts\` are exempt at src/ root.`
    );
    console.error(
        "Move each violation into a folder: mkdir src/<feature>/ && git mv src/<feature>.{ts,test.ts,md} src/<feature>/, then add a src/<feature>/index.ts barrel and update sibling imports."
    );
    process.exit(1);
}

main();