import { mkdir, readFile, writeFile } from "node:fs/promises";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";

const repoRoot = join(dirname(fileURLToPath(import.meta.url)), "..");
const pagePath = join(repoRoot, "content", "pages", "home.json");
const templateRoot = join(repoRoot, "templates", "pages", "home");
const shellPath = join(templateRoot, "shell.html");
const blockRoot = join(templateRoot, "blocks");

const REGION_TOKEN = {
  beforeCViz: "{{NODEDC_BLOCKS_BEFORE_CVIZ}}",
  cViz: "{{NODEDC_BLOCKS_CVIZ}}",
  sections: "{{NODEDC_BLOCKS_SECTIONS}}",
};

const page = JSON.parse(await readFile(pagePath, "utf8"));
const shell = await readFile(shellPath, "utf8");
const templateCache = new Map();

async function readTemplate(templateName) {
  if (!templateName || templateName.includes("..") || templateName.includes("/")) {
    throw new Error(`Unsafe template name: ${templateName}`);
  }

  if (!templateCache.has(templateName)) {
    templateCache.set(templateName, await readFile(join(blockRoot, templateName), "utf8"));
  }

  return templateCache.get(templateName);
}

function escapeRegExp(value) {
  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
}

function getByPath(source, path) {
  return path.split(".").reduce((value, key) => value?.[key], source);
}

function isTruthy(value) {
  if (Array.isArray(value)) return value.length > 0;
  return Boolean(value);
}

function cloneValue(value) {
  return value == null ? value : JSON.parse(JSON.stringify(value));
}

function allBlocks(model) {
  return (model.regions ?? []).flatMap((region) => region.blocks ?? []);
}

function applySharedDemoRequest(model) {
  const blocks = allBlocks(model);
  const source = blocks.find((block) => block.id === "hero-waitlist");

  if (!source?.content) return;

  for (const block of blocks) {
    if (block.id === source.id || block.type !== "waitlistFiles") continue;

    block.content ??= {};
    block.content.accessCard = cloneValue(source.content.accessCard);
    block.content.form = cloneValue(source.content.form);
    block.content.legal ??= { enabled: true, html: "" };
    block.content.legal.html = source.content.legalHtml ?? block.content.legal.html ?? "";
  }
}

const LINK_WINDOW_TARGETS = new Set(["_blank", "_self", "_parent", "_top"]);

function isWindowTarget(value) {
  return LINK_WINDOW_TARGETS.has(String(value || "").trim());
}

function isExternalHref(value) {
  return /^(https?:)?\/\//i.test(String(value || "")) || /^(mailto:|tel:)/i.test(String(value || ""));
}

function isInertHref(value) {
  const href = String(value || "").trim();
  return !href || href === "#" || href === "#hero" || href.toLowerCase().startsWith("javascript:");
}

function normalizeLinkForRender(item) {
  if (!item || typeof item !== "object") return;

  let href = item.href ?? "";
  let target = item.target ?? "";
  let linkTarget = item.linkTarget ?? "";

  if (isWindowTarget(target)) {
    linkTarget ||= target;
    target = "";
  }

  const mode = item.linkMode === "href" || item.linkMode === "target" ? item.linkMode : isExternalHref(href) ? "href" : "target";

  if (mode === "target" && !target && href && !isExternalHref(href)) {
    target = href;
    href = "";
  }

  const primaryHref = mode === "href" ? href : target;
  const fallbackHref = mode === "href" ? target : href;
  item.resolvedHref = primaryHref || fallbackHref || "#";
  item.resolvedTarget = mode === "href" ? linkTarget : "";
}

function normalizeDockItemForRender(item) {
  if (!item || typeof item !== "object") return;

  const href = String(item.href || "").trim();
  const opensWindow = !isInertHref(href);

  item.resolvedDockHref = href || "#";
  item.resolvedDockTarget = opensWindow ? "_blank" : "";
  item.resolvedDockRel = opensWindow ? "noopener noreferrer" : "";
}

function applyRenderableLinks(model) {
  const staticLinks = model.staticElements?.content?.navigation?.links;
  if (Array.isArray(staticLinks)) {
    staticLinks.forEach(normalizeLinkForRender);
  }

  const dockItems = model.staticElements?.content?.dock?.items;
  if (Array.isArray(dockItems)) {
    dockItems.forEach(normalizeDockItemForRender);
  }

  for (const block of allBlocks(model)) {
    const footer = block.content?.footer;
    if (!footer) continue;
    if (Array.isArray(footer.navLinks)) footer.navLinks.forEach(normalizeLinkForRender);
    if (Array.isArray(footer.contactLinks)) footer.contactLinks.forEach(normalizeLinkForRender);
  }
}

function escapeHtml(value) {
  return String(value)
    .replaceAll("&", "&")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;");
}

function escapeAttr(value) {
  return escapeHtml(value).replaceAll('"', "&quot;").replaceAll("'", "&#39;");
}

function escapeJsString(value) {
  return String(value)
    .replaceAll("\\", "\\\\")
    .replaceAll('"', '\\"')
    .replaceAll("\n", "\\n")
    .replaceAll("\r", "\\r")
    .replaceAll("\u2028", "\\u2028")
    .replaceAll("\u2029", "\\u2029")
    .replaceAll("</script", "<\\/script");
}

function renderTemplateTokens(html, block) {
  return html.replace(/\{\{\s*(text|html|attr|js):([a-zA-Z0-9_.-]+)\s*\}\}/g, (_match, mode, path) => {
    const value = getByPath(block, path);

    if (value === undefined) {
      throw new Error(`Missing token value "${path}" in block "${block.id}"`);
    }

    if (mode === "html") {
      return value == null ? "" : String(value);
    }

    if (mode === "attr") {
      return value == null ? "" : escapeAttr(value);
    }

    if (mode === "js") {
      return value == null ? "" : escapeJsString(value);
    }

    return value == null ? "" : escapeHtml(value);
  });
}

function renderIfBlocks(html, block) {
  let rendered = html;
  let previous = null;

  while (rendered !== previous) {
    previous = rendered;
    rendered = rendered.replace(
      /\{\{#if\s+([a-zA-Z0-9_.-]+)\s*\}\}((?:(?!\{\{#if|\{\{\/if\}\})[\s\S])*)\{\{\/if\}\}/g,
      (_match, path, innerHtml) => {
        const value = getByPath(block, path);
        return isTruthy(value) ? renderTemplate(innerHtml, block) : "";
      },
    );
  }

  return rendered;
}

function renderEachBlocks(html, block) {
  return html.replace(/\{\{#each\s+([a-zA-Z0-9_.-]+)\s*\}\}([\s\S]*?)\{\{\/each\}\}/g, (_match, path, innerHtml) => {
    const items = getByPath(block, path);

    if (!Array.isArray(items)) {
      throw new Error(`Each token "${path}" in block "${block.id}" must point to an array`);
    }

    return items
      .map((item) => {
        const itemScope = item && typeof item === "object" && !Array.isArray(item) ? item : { value: item };
        return renderTemplate(innerHtml, { ...block, ...itemScope });
      })
      .join("");
  });
}

function renderTemplate(html, block) {
  return renderTemplateTokens(renderIfBlocks(renderEachBlocks(html, block), block), block);
}

function scopeDuplicateIds(html, scope) {
  const ids = [...html.matchAll(/\sid="([^"]+)"/g)].map((match) => match[1]);
  if (!ids.length) {
    return html;
  }

  let scoped = html.replace(/\sid="([^"]+)"/g, (_match, id) => ` id="${scope}-${id}"`);

  for (const id of ids) {
    const escaped = escapeRegExp(id);
    scoped = scoped.replace(
      new RegExp(`\\s(data-target|for|aria-controls|aria-labelledby|aria-describedby)="${escaped}"`, "g"),
      (_match, attr) => ` ${attr}="${scope}-${id}"`,
    );
    scoped = scoped.replace(new RegExp(`(href="[^"]*)#${escaped}(")`, "g"), `$1#${scope}-${id}$2`);
  }

  return scoped;
}

async function renderBlock(block, renderCounts) {
  if (block.enabled === false) {
    return "";
  }

  const templateName = block.template;
  const renderCount = renderCounts.get(templateName) ?? 0;
  renderCounts.set(templateName, renderCount + 1);

  const html = renderTemplate(await readTemplate(templateName), block);

  if (renderCount === 0 && block.scopeIds !== true) {
    return html;
  }

  return scopeDuplicateIds(html, block.id);
}

async function renderRegion(region) {
  const renderCounts = new Map();
  const blocks = [];

  for (const block of region.blocks ?? []) {
    blocks.push(await renderBlock(block, renderCounts));
  }

  return blocks.join("");
}

async function renderSections() {
  const renderCounts = new Map();
  const output = [];
  let cVizRun = [];

  const flushCVizRun = () => {
    if (!cVizRun.length) return;
    output.push(`<div class="c-viz">${cVizRun.join("")}</div>`);
    cVizRun = [];
  };

  for (const region of page.regions ?? []) {
    for (const block of region.blocks ?? []) {
      const html = await renderBlock(block, renderCounts);
      if (!html) continue;

      if (block.region === "cViz") {
        cVizRun.push(html);
      } else {
        flushCVizRun();
        output.push(html);
      }
    }
  }

  flushCVizRun();
  return output.join("");
}

applySharedDemoRequest(page);
applyRenderableLinks(page);

let output = renderTemplate(shell, { id: page.slug, ...page });

if (output.includes(REGION_TOKEN.sections)) {
  output = output.replace(REGION_TOKEN.sections, await renderSections());
} else {
  for (const region of page.regions ?? []) {
    const token = REGION_TOKEN[region.id];
    if (!token) {
      throw new Error(`Unknown region: ${region.id}`);
    }

    output = output.replace(token, await renderRegion(region));
  }
}

for (const token of Object.values(REGION_TOKEN)) {
  if (output.includes(token)) {
    throw new Error(`Unrendered token left in shell: ${token}`);
  }
}

const outputPath = join(repoRoot, page.output || "index.html");
await mkdir(dirname(outputPath), { recursive: true });
await writeFile(outputPath, output);

console.log(`Rendered ${page.slug} -> ${outputPath}`);