import { renderInline } from "../inline/render.js";
import type { BlockHandler, IdentifyResult } from "./handler.type.js";
import { ITEM_SEPARATOR } from "./identify.js";

const FOOTNOTE_DEF = /^\[\^([\w-]+)\]:\s*(.*)$/;

export const footnoteHandler = {
  identify(lines: string[], index: number): IdentifyResult | null {
    const firstMatch = lines[index].match(FOOTNOTE_DEF);
    if (!firstMatch) return null;

    const items: string[] = [];
    let i = index;

    while (i < lines.length) {
      const match = lines[i].match(FOOTNOTE_DEF);
      if (!match) break;

      const id = match[1];
      const textParts = [match[2]];

      i++;
      // Gather continuation lines (indented)
      while (i < lines.length) {
        const cur = lines[i];
        if (cur.startsWith("  ") || cur.startsWith("\t")) {
          textParts.push(cur.replace(/^[ \t]+/, ""));
          i++;
        } else {
          break;
        }
      }

      items.push(`${id}:${textParts.join("\n")}`);
    }

    return {
      raw: items.join(ITEM_SEPARATOR),
      nextIndex: i,
    };
  },

  render(raw: string): string {
    const items = raw.split(ITEM_SEPARATOR);
    const listItems = items.map((item) => {
      const colonIdx = item.indexOf(":");
      const id = item.slice(0, colonIdx);
      const text = item.slice(colonIdx + 1);
      return `<li id="fn-${id}"><p>${renderInline(text)} <a href="#fnref-${id}" class="footnote-backref">\u21A9\uFE0E</a></p></li>`;
    });

    return `<section class="footnotes"><ol>${listItems.join("")}</ol></section>`;
  },

  serialize(raw: string): string {
    const items = raw.split(ITEM_SEPARATOR);
    return items
      .map((item) => {
        const colonIdx = item.indexOf(":");
        const id = item.slice(0, colonIdx);
        const text = item.slice(colonIdx + 1);
        return `[^${id}]: ${text}`;
      })
      .join("\n");
  },
} satisfies BlockHandler;