/**
 * Standalone HTML exporter.
 *
 * Emits a single self-contained `.html` file: a full document with the theme
 * stylesheet inlined in a `<style>` block, a title/author header, a table of
 * contents, the body, and a generation timestamp. The body is scoped under
 * `.ps-doc` so the theme CSS never leaks into the page chrome.
 */
import type { Block, FlatProject, Mark } from "./model.js";
import { escapeHtml } from "./model.js";
import type { Theme } from "./themes.js";

export interface HtmlOptions {
  theme?: Theme;
  /** Include a table of contents (default: true). */
  tableOfContents?: boolean;
  /** Fixed ISO timestamp for the footer (deterministic output). */
  generatedAt?: string | undefined;
}

/** Serialize inline text + marks to HTML. */
function serializeInlineHtml(text: string, marks: Mark[]): string {
  if (!marks.length) return escapeHtml(text);
  const boundaries = new Set<number>([0, text.length]);
  for (const m of marks) {
    boundaries.add(Math.max(0, Math.min(text.length, m.start)));
    boundaries.add(Math.max(0, Math.min(text.length, m.end)));
  }
  const points = Array.from(boundaries).sort((a, b) => a - b);
  let out = "";
  for (let i = 0; i < points.length - 1; i++) {
    const start = points[i]!;
    const end = points[i + 1]!;
    const runMarks = marks.filter((m) => m.start <= start && m.end >= end);
    out += runToHtml(text.slice(start, end), runMarks);
  }
  return out;
}

function runToHtml(segment: string, marks: Mark[]): string {
  let out = escapeHtml(segment);
  if (marks.some((m) => m.type === "italic")) out = `<em>${out}</em>`;
  if (marks.some((m) => m.type === "bold")) out = `<strong>${out}</strong>`;
  if (marks.some((m) => m.type === "strike")) out = `<strike>${out}</strike>`;
  if (marks.some((m) => m.type === "code")) out = `<code>${out}</code>`;
  const color = marks.find((m) => m.type === "color");
  if (color?.attrs?.color) {
    out = `<span style="color:${escapeHtml(String(color.attrs.color))}">${out}</span>`;
  }
  const link = marks.find((m) => m.type === "link");
  if (link?.attrs?.href) {
    out = `<a href="${escapeHtml(String(link.attrs.href))}" rel="noopener">${out}</a>`;
  }
  return out;
}

function listToHtml(block: Block): string {
  const items = block.children ?? [];
  const tag = block.listType === "ordered" ? "ol" : "ul";
  const inner = items
    .map(
      (item) =>
        `<li>${serializeInlineHtml(item.text ?? "", item.marks ?? [])}</li>`
    )
    .join("");
  return `<${tag}>${inner}</${tag}>`;
}

function blockToHtml(block: Block): string {
  switch (block.type) {
    case "heading": {
      const level = Math.max(1, Math.min(6, block.level ?? 1));
      return `<h${level}>${serializeInlineHtml(block.text ?? "", block.marks ?? [])}</h${level}>`;
    }
    case "paragraph":
      return `<p>${serializeInlineHtml(block.text ?? "", block.marks ?? [])}</p>`;
    case "sceneBreak":
      return `<div class="scene-break">***</div>`;
    case "blockquote":
      return `<blockquote>${(block.children ?? []).map(blockToHtml).join("")}</blockquote>`;
    case "codeBlock":
      return `<pre><code>${escapeHtml(block.text ?? "")}</code></pre>`;
    case "footnote":
      return `<div class="footnote">${serializeInlineHtml(block.text ?? "", [])}</div>`;
    case "list":
      return listToHtml(block);
    default:
      return "";
  }
}

function tocHtml(project: FlatProject): string {
  const items = project.frontmatter.chapters
    .map((c) => `<li>${c.order}. ${escapeHtml(c.title)}</li>`)
    .join("");
  return `<nav class="ps-toc"><h2>Contents</h2><ul>${items}</ul></nav>`;
}

/**
 * Serialize a flattened project to a standalone HTML document.
 *
 * @param project the flattened project (frontmatter + blocks)
 * @param options theme, table-of-contents toggle
 */
export function exportHtml(
  project: FlatProject,
  options?: HtmlOptions
): string {
  const theme = options?.theme;
  const toc = options?.tableOfContents !== false;
  const fm = project.frontmatter;
  const generated = options?.generatedAt ?? new Date().toISOString();

  const body = project.blocks.map(blockToHtml).join("\n");
  const headerAuthor = fm.author ? `<p class="ps-author">${escapeHtml(fm.author)}</p>` : "";

  return `<!DOCTYPE html>
<html lang="${escapeHtml(fm.language ?? "en")}">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>${escapeHtml(fm.title)}</title>
<style>
* { box-sizing: border-box; }
body { margin: 0; }
${theme?.css ?? ""}
.ps-doc { max-width: 40rem; margin: 0 auto; padding: 2rem 1rem; }
.ps-header { margin-bottom: 2rem; }
.ps-header h1 { margin-top: 0; }
.ps-author { color: #6b6b6b; font-style: italic; }
.ps-toc { margin: 2rem 0; padding: 1rem; border: 1px solid #ddd; border-radius: 6px; }
</style>
</head>
<body>
<div class="ps-doc">
  <header class="ps-header">
    <h1>${escapeHtml(fm.title)}</h1>
    ${headerAuthor}
  </header>
  ${toc ? tocHtml(project) : ""}
  <main>
${body}
  </main>
  <footer class="ps-footer" style="margin-top:3rem;color:#999;font-size:0.8rem;">
    Generated ${escapeHtml(generated)}
  </footer>
</div>
</body>
</html>
`;
}