import test from "node:test";
import assert from "node:assert/strict";
import fs from "node:fs";
import path from "node:path";

const postsDir = path.resolve("src/posts");

test("Content Contract: All posts in src/posts/ satisfy frontmatter schema", () => {
  if (!fs.existsSync(postsDir)) {
    fs.mkdirSync(postsDir, { recursive: true });
  }
  const postFiles = fs.readdirSync(postsDir).filter((f) => f.endsWith(".md"));

  if (postFiles.length === 0) {
    // When posts are decoupled and mounted externally or ingested via API
    return;
  }

  for (const file of postFiles) {
    const filePath = path.join(postsDir, file);
    const content = fs.readFileSync(filePath, "utf-8");

    // 1. Filename Convention: YYYY-MM-DD-slug.md
    assert.match(
      file,
      /^\d{4}-\d{2}-\d{2}-[a-z0-9-]+\.md$/,
      `Post filename '${file}' must follow 'YYYY-MM-DD-slug.md' naming standard`
    );

    // 2. YAML Frontmatter Boundary check
    assert.match(
      content,
      /^---\n([\s\S]*?)\n---/,
      `Post '${file}' must start with valid YAML frontmatter delimiters`
    );

    // Extract frontmatter block
    const fmMatch = content.match(/^---\n([\s\S]*?)\n---/);
    const fmText = fmMatch[1];

    // 3. Title Invariant
    assert.match(
      fmText,
      /title:\s*"[^"]{5,}"/,
      `Post '${file}' must contain a valid title of at least 5 characters`
    );

    // 4. Date Invariant (ISO Format)
    assert.match(
      fmText,
      /date:\s*\d{4}-\d{2}-\d{2}/,
      `Post '${file}' must define an ISO date (YYYY-MM-DD)`
    );

    // 5. Layout Invariant
    assert.match(
      fmText,
      /layout:\s*layouts\/post\.njk/,
      `Post '${file}' must specify 'layout: layouts/post.njk'`
    );

    // 6. Tags Invariant
    assert.match(
      fmText,
      /tags:\s*\n(\s+-\s+[a-z0-9-]+\n)+/,
      `Post '${file}' must specify a non-empty YAML tags list`
    );

    // 7. Excerpt Invariant
    assert.match(
      fmText,
      /excerpt:\s*"[^"]{20,}"/,
      `Post '${file}' must provide a substantive excerpt of at least 20 characters`
    );
  }
});