#!/usr/bin/env node
/* eslint-disable no-console */
import { readFile } from "node:fs/promises";
import path from "node:path";
import { fileURLToPath } from "node:url";

const __dirname = path.dirname(fileURLToPath(import.meta.url));
const repoRoot = path.resolve(__dirname, "..");
const guideRelativePath = "docs/porting-guide.md";
const guidePath = path.join(repoRoot, guideRelativePath);

const requiredHeadings = [
  "# Porting Guide",
  "## Rename/Replace Map",
  "## Do-Not-Replace Rules",
  "## Verification",
];
const unresolvedMarkerPattern = /^(?!.*(?:inline TODO markers|node -e )).*\b(?:TODO|TBD|FIXME)\b.*$/m;
const minimumMapRows = 12;

function fail(message) {
  console.error(`Porting Docs porting guide verification failed: ${message}`);
  process.exit(1);
}

function headingPattern(heading) {
  const escapedHeading = heading.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
  if (heading === "# Porting Guide") return /^# .*Porting Guide\s*$/m;
  return new RegExp(`^${escapedHeading}\\s*$`, "m");
}

function hasHeading(text, heading) {
  return headingPattern(heading).test(text);
}

function sectionBody(text, heading) {
  const lines = text.split(/\r?\n/);
  const startIndex = lines.findIndex((line) => line.trim() === heading);
  if (startIndex === -1) return "";
  const currentLevel = heading.match(/^#+/)?.[0].length ?? 1;
  const endIndex = lines.findIndex((line, index) => {
    if (index <= startIndex) return false;
    const match = line.match(/^(#+)\s+/);
    return Boolean(match && match[1].length <= currentLevel);
  });
  return lines.slice(startIndex + 1, endIndex === -1 ? undefined : endIndex).join("\n");
}

function countUsefulTableRows(section) {
  return section
    .split(/\r?\n/)
    .map((line) => line.trim())
    .filter((line) => {
      if (!line.startsWith("|") || !line.endsWith("|")) return false;
      const cells = line
        .split("|")
        .slice(1, -1)
        .map((cell) => cell.trim());
      if (cells.length < 4) return false;
      if (cells.every((cell) => /^:?-{3,}:?$/.test(cell))) return false;
      return cells.every((cell) => cell.length > 0);
    }).length;
}

let text;
try {
  text = await readFile(guidePath, "utf8");
} catch (error) {
  if (error?.code === "ENOENT") fail(`missing ${guideRelativePath}`);
  throw error;
}

if (!text.trim()) fail(`${guideRelativePath} is empty`);
if (unresolvedMarkerPattern.test(text)) fail(`${guideRelativePath} contains unresolved TODO/TBD/FIXME markers`);

for (const heading of requiredHeadings) {
  if (!hasHeading(text, heading)) fail(`missing required heading \`${heading}\``);
}

const mapRows = countUsefulTableRows(sectionBody(text, "## Rename/Replace Map"));
if (mapRows < minimumMapRows) {
  fail(`Rename/Replace Map has ${mapRows} useful table rows; expected at least ${minimumMapRows}`);
}

console.log(`Verified ${guideRelativePath}: ${mapRows} Rename/Replace Map table rows.`);