// HTML-fragment parsing and inline-island conversion for the Telegram rich
// blocks emitter. Agents author rich content as markdown plus a documented set
// of HTML islands (see agentPrompt.inboundFormattingHints "markdown_telegram_rich");
// this module owns the tolerant parser and inline (RichText-level) mapping,
// while rich-blocks-html-map.ts owns block-level island mapping.
import { tokenizeHtmlTags } from "openclaw/plugin-sdk/text-chunking";
import { decodeTelegramHtmlEntities } from "./format-html.js";
import type { RichText } from "./rich-block-model.js";

export type HtmlNode =
  | { kind: "text"; text: string }
  | { kind: "element"; name: string; raw: string; children: HtmlNode[]; closed: boolean };

export const VOID_TAGS = new Set(["br", "hr", "img", "input", "tg-map"]);

const INLINE_STYLE_TAGS: Record<
  string,
  | "bold"
  | "italic"
  | "underline"
  | "strikethrough"
  | "code"
  | "spoiler"
  | "marked"
  | "subscript"
  | "superscript"
> = {
  b: "bold",
  strong: "bold",
  i: "italic",
  em: "italic",
  u: "underline",
  ins: "underline",
  s: "strikethrough",
  del: "strikethrough",
  strike: "strikethrough",
  code: "code",
  "tg-spoiler": "spoiler",
  mark: "marked",
  sub: "subscript",
  sup: "superscript",
};

const HTML_ATTR_RE = /([a-zA-Z][a-zA-Z0-9-]*)(?:\s*=\s*(?:"([^"]*)"|'([^']*)'|([^\s"'=<>`]+)))?/g;

export function parseHtmlAttrs(raw: string): Map<string, string> {
  const attrs = new Map<string, string>();
  const inner = raw.replace(/^<\/?[a-zA-Z][a-zA-Z0-9-]*/, "").replace(/\/?>$/, "");
  for (const match of inner.matchAll(HTML_ATTR_RE)) {
    const name = match[1]?.toLowerCase();
    if (name) {
      attrs.set(name, decodeTelegramHtmlEntities(match[2] ?? match[3] ?? match[4] ?? ""));
    }
  }
  return attrs;
}

/** Parse an HTML fragment into a light node tree; unmatched tags stay text. */
export function parseHtmlFragment(text: string): HtmlNode[] {
  const root: HtmlNode[] = [];
  const stack: Array<{ name: string; node: Extract<HtmlNode, { kind: "element" }> }> = [];
  const childrenOf = () => (stack.length > 0 ? stack[stack.length - 1]!.node.children : root);
  let cursor = 0;
  const pushText = (from: number, to: number) => {
    if (to > from) {
      childrenOf().push({ kind: "text", text: text.slice(from, to) });
    }
  };
  for (const tag of tokenizeHtmlTags(text)) {
    pushText(cursor, tag.start);
    cursor = tag.end;
    if (tag.closing) {
      const openIndex = stack.findLastIndex((entry) => entry.name === tag.name);
      if (openIndex >= 0) {
        for (let depth = openIndex; depth < stack.length; depth += 1) {
          stack[depth]!.node.closed = depth === openIndex;
        }
        stack.length = openIndex;
      } else {
        childrenOf().push({ kind: "text", text: tag.raw });
      }
      continue;
    }
    const selfContained = tag.selfClosing || VOID_TAGS.has(tag.name);
    const element: Extract<HtmlNode, { kind: "element" }> = {
      kind: "element",
      name: tag.name,
      raw: tag.raw,
      children: [],
      closed: selfContained,
    };
    childrenOf().push(element);
    if (!selfContained) {
      stack.push({ name: tag.name, node: element });
    }
  }
  pushText(cursor, text.length);
  return unwrapUnclosed(root);
}

// An open tag with no matching close is not an island: it stays literal text so
// malformed agent output remains visible instead of silently restyling the rest.
function unwrapUnclosed(nodes: HtmlNode[]): HtmlNode[] {
  const result: HtmlNode[] = [];
  for (const node of nodes) {
    if (node.kind === "text") {
      result.push(node);
      continue;
    }
    const children = unwrapUnclosed(node.children);
    if (node.closed) {
      result.push({ ...node, children });
    } else {
      result.push({ kind: "text", text: node.raw }, ...children);
    }
  }
  return result;
}

export function nodeText(nodes: readonly HtmlNode[]): string {
  return nodes
    .map((node) =>
      node.kind === "text" ? decodeTelegramHtmlEntities(node.text) : nodeText(node.children),
    )
    .join("");
}

function normalizeIslandText(text: string): string {
  return text.replace(/\s+/g, " ").trim();
}

// Raw round-trip of a subtree; keeps unsupported wrappers fully literal.
function serializeHtmlNodes(nodes: readonly HtmlNode[]): string {
  return nodes
    .map((node) => {
      if (node.kind === "text") {
        return node.text;
      }
      const selfContained = VOID_TAGS.has(node.name) || node.raw.trimEnd().endsWith("/>");
      return selfContained
        ? node.raw
        : `${node.raw}${serializeHtmlNodes(node.children)}</${node.name}>`;
    })
    .join("");
}

/** Convert island children into RichText, honoring documented inline tags. */
export function htmlNodesToRichText(nodes: readonly HtmlNode[]): RichText {
  const parts: RichText[] = [];
  for (const node of nodes) {
    if (node.kind === "text") {
      const value = decodeTelegramHtmlEntities(node.text.replace(/\s+/g, " "));
      if (value) {
        parts.push(value);
      }
      continue;
    }
    const style = INLINE_STYLE_TAGS[node.name];
    if (style) {
      parts.push({ type: style, text: htmlNodesToRichText(node.children) });
      continue;
    }
    if (node.name === "a") {
      const href = parseHtmlAttrs(node.raw).get("href");
      const inner = htmlNodesToRichText(node.children);
      if (href?.startsWith("#")) {
        // In-message fragments are RichTextAnchorLink, not RichTextUrl.
        parts.push({ type: "anchor_link", text: inner, anchor_name: href.slice(1) });
      } else {
        parts.push(href ? { type: "url", text: inner, url: href } : inner);
      }
      continue;
    }
    if (node.name === "tg-math") {
      parts.push({ type: "mathematical_expression", expression: nodeText(node.children) });
      continue;
    }
    if (node.name === "tg-emoji") {
      const emojiId = parseHtmlAttrs(node.raw).get("emoji-id");
      const alternative = normalizeIslandText(nodeText(node.children));
      // Wire contract: custom_emoji_id must be a valid Number (live-verified
      // 400 otherwise); unknown-but-numeric IDs degrade server-side.
      if (emojiId && /^\d+$/.test(emojiId) && alternative) {
        parts.push({
          type: "custom_emoji",
          custom_emoji_id: emojiId,
          alternative_text: alternative,
        });
        continue;
      }
      parts.push(alternative);
      continue;
    }
    if (node.name === "br") {
      parts.push("\n");
      continue;
    }
    if (node.name === "p" || node.name === "span" || node.name === "div") {
      // Transparent containers: content only.
      parts.push(htmlNodesToRichText(node.children));
      continue;
    }
    // Unsupported element: its ENTIRE subtree stays literal so agent mistakes
    // remain visible; converting recognized descendants would mix typed nodes
    // into a literal wrapper and lose their markup from the plain projection.
    const selfContained = VOID_TAGS.has(node.name) || node.raw.trimEnd().endsWith("/>");
    parts.push(node.raw, serializeHtmlNodes(node.children));
    if (!selfContained) {
      parts.push(`</${node.name}>`);
    }
  }
  if (parts.length === 0) {
    return "";
  }
  if (parts.length === 1) {
    return parts[0] ?? "";
  }
  return parts;
}

/** Parse inline islands (<sup>, <tg-math>, <tg-emoji>, …) out of a text leaf. */
export function parseInlineHtmlIslands(leaf: string): RichText {
  if (!leaf.includes("<")) {
    return leaf;
  }
  const nodes = parseHtmlFragment(leaf);
  const hasElement = nodes.some((node) => node.kind === "element");
  if (!hasElement) {
    return leaf;
  }
  // Preserve raw whitespace when no islands parse; only island-bearing leaves
  // go through the normalizing HTML text model.
  return htmlNodesToRichText(nodes);
}

// Prompt contract: media islands are https-only.