#!/usr/bin/env node

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

process.stdout.on("error", (error) => {
  if (error?.code === "EPIPE") {
    process.exit(0);
  }
  throw error;
});

const DOCS_DIR = join(process.cwd(), "docs");
if (!existsSync(DOCS_DIR)) {
  console.error("docs:list: missing docs directory. Run from repo root.");
  process.exit(1);
}
if (!statSync(DOCS_DIR).isDirectory()) {
  console.error("docs:list: docs path is not a directory.");
  process.exit(1);
}

const EXCLUDED_DIRS = new Set(["archive", "research"]);

/**
 * @param {unknown[]} values
 * @returns {string[]}
 */
function compactStrings(values) {
  const result = [];
  for (const value of values) {
    if (value === null || value === undefined) {
      continue;
    }
    const normalized =
      typeof value === "string"
        ? value.trim()
        : typeof value === "number" || typeof value === "boolean"
          ? String(value).trim()
          : null;

    if (normalized?.length > 0) {
      result.push(normalized);
    }
  }
  return result;
}

/**
 * @param {string} dir
 * @param {string} base
 * @returns {string[]}
 */
function walkMarkdownFiles(dir, base = dir) {
  const entries = readdirSync(dir, { withFileTypes: true });
  const files = [];
  for (const entry of entries) {
    if (entry.name.startsWith(".")) {
      continue;
    }
    const fullPath = join(dir, entry.name);
    if (entry.isDirectory()) {
      if (EXCLUDED_DIRS.has(entry.name)) {
        continue;
      }
      files.push(...walkMarkdownFiles(fullPath, base));
    } else if (entry.isFile() && entry.name.endsWith(".md")) {
      files.push(relative(base, fullPath));
    }
  }
  return files.toSorted((a, b) => a.localeCompare(b));
}

/**
 * @param {string} fullPath
 * @returns {{ summary: string | null; readWhen: string[]; error?: string }}
 */
function extractMetadata(fullPath) {
  const content = readFileSync(fullPath, "utf8");

  if (!content.startsWith("---")) {
    return { summary: null, readWhen: [], error: "missing front matter" };
  }

  const endIndex = content.indexOf("\n---", 3);
  if (endIndex === -1) {
    return { summary: null, readWhen: [], error: "unterminated front matter" };
  }

  const frontMatter = content.slice(3, endIndex).trim();
  const lines = frontMatter.split("\n");

  let summaryLine = null;
  const readWhen = [];
  let collectingField = null;

  for (const rawLine of lines) {
    const line = rawLine.trim();

    if (line.startsWith("summary:")) {
      summaryLine = line;
      collectingField = null;
      continue;
    }

    if (line.startsWith("read_when:")) {
      collectingField = "read_when";
      const inline = line.slice("read_when:".length).trim();
      if (inline.startsWith("[") && inline.endsWith("]")) {
        try {
          const parsed = JSON.parse(inline.replace(/'/g, '"'));
          if (Array.isArray(parsed)) {
            readWhen.push(...compactStrings(parsed));
          }
        } catch {
          // ignore malformed inline arrays
        }
      }
      continue;
    }

    if (collectingField === "read_when") {
      if (line.startsWith("- ")) {
        const hint = line.slice(2).trim();
        if (hint) {
          readWhen.push(hint);
        }
      } else if (line === "") {
        // allow blank lines inside the list
      } else {
        collectingField = null;
      }
    }
  }

  if (!summaryLine) {
    return { summary: null, readWhen, error: "summary key missing" };
  }

  const summaryValue = summaryLine.slice("summary:".length).trim();
  const normalized = summaryValue
    .replace(/^['"]|['"]$/g, "")
    .replace(/\s+/g, " ")
    .trim();

  if (!normalized) {
    return { summary: null, readWhen, error: "summary is empty" };
  }

  return { summary: normalized, readWhen };
}

console.log("Listing all markdown files in docs folder:");

const markdownFiles = walkMarkdownFiles(DOCS_DIR);

for (const relativePath of markdownFiles) {
  const fullPath = join(DOCS_DIR, relativePath);
  const { summary, readWhen, error } = extractMetadata(fullPath);
  if (summary) {
    console.log(`${relativePath} - ${summary}`);
    if (readWhen.length > 0) {
      console.log(`  Read when: ${readWhen.join("; ")}`);
    }
  } else {
    const reason = error ? ` - [${error}]` : "";
    console.log(`${relativePath}${reason}`);
  }
}

console.log(
  '\nReminder: keep docs up to date as behavior changes. When your task matches any "Read when" hint above (React hooks, cache directives, database work, tests, etc.), read that doc before coding, and suggest new coverage when it is missing.',
);
