// ---------------------------------------------------------------------------
// Source-reference helpers (browser-only)
//
// These functions access `window` and `document` and therefore can only run in
// the browser.  They are intentionally NOT marked "use client" because they are
// plain utility functions, not React components or hooks.  Any React component
// that calls them must itself be a client component.
// ---------------------------------------------------------------------------

import { BOOK_NAMES, CC_LILAS } from "@/lib/constants";
import { buildHighlightUrl } from "@/lib/text-highlight";

/**
 * Parse the current page URL into a human-readable source reference.
 * Returns { title, detail, url } or null if on a non-content page.
 */
export function getSourceReference(): {
  title: string;
  detail: string | null;
  url: string;
} | null {
  const url = window.location.href;
  const path = window.location.pathname;
  const parts = path.split("/").filter(Boolean);

  // /books/bg/1/1 → Bhagavad-gītā As It Is, Chapter 1, Verse 1
  if (parts[0] === "books" && parts.length >= 2) {
    const code = parts[1];
    const bookName = BOOK_NAMES[code] || code.toUpperCase();

    // Verse-based: /books/bg/[chapter]/[verse]
    if (code === "bg" && parts.length >= 4) {
      return {
        title: bookName,
        detail: `Chapter ${parts[2]}, Verse ${parts[3]}`,
        url,
      };
    }
    // SB: /books/sb/[canto]/[chapter]/[verse]
    if (code === "sb" && parts.length >= 5) {
      return {
        title: bookName,
        detail: `Canto ${parts[2]}, Chapter ${parts[3]}, Verse ${parts[4]}`,
        url,
      };
    }
    // CC: /books/cc/[lila]/[chapter]/[verse]
    if (code === "cc" && parts.length >= 5) {
      const lila = CC_LILAS[parts[2]] || parts[2];
      return {
        title: bookName,
        detail: `${lila}, Chapter ${parts[3]}, Verse ${parts[4]}`,
        url,
      };
    }
    // CC lila index: /books/cc/[lila]
    if (code === "cc" && parts.length === 3) {
      const lila = CC_LILAS[parts[2]] || parts[2];
      return { title: bookName, detail: lila, url };
    }
    // SB1962: /books/sb1962/[chapter]/[verse]
    if (code === "sb1962" && parts.length >= 4) {
      return {
        title: bookName,
        detail: `Chapter ${parts[2]}, Verse ${parts[3]}`,
        url,
      };
    }
    // ISO/NOI: /books/iso/[mantra]
    if ((code === "iso" || code === "noi") && parts.length >= 3) {
      const num = parts[2];
      const label = code === "iso" ? "Mantra" : "Text";
      return { title: bookName, detail: `${label} ${num}`, url };
    }
    // BS/MM/NBS: /books/{code}/[chapter]/[verse]
    if (
      (code === "bs" || code === "mm" || code === "nbs") &&
      parts.length >= 4
    ) {
      return {
        title: bookName,
        detail: `Chapter ${parts[2]}, Verse ${parts[3]}`,
        url,
      };
    }
    // KB: /books/kb/[volume]/[slug]
    if (code === "kb" && parts.length >= 4) {
      return {
        title: bookName,
        detail: `Volume ${parts[2]}, Chapter ${parts[3]}`,
        url,
      };
    }
    // Generic prose: /books/{code}/[chapter]
    if (parts.length >= 3) {
      const chSlug = parts[2];
      const chNum = parseInt(chSlug, 10);
      const detail = isNaN(chNum)
        ? chSlug.replace(/-/g, " ")
        : `Chapter ${chNum}`;
      return { title: bookName, detail, url };
    }
    // Book index page
    return { title: bookName, detail: null, url };
  }

  // /letters/[slug]
  if (
    parts[0] === "letters" &&
    parts.length === 2 &&
    parts[1] !== "year" &&
    parts[1] !== "recipient" &&
    parts[1] !== "location"
  ) {
    // h1 contains "Letter to Mukunda" — use it as the title
    const h1 = document.querySelector("h1");
    const title = h1?.textContent?.trim() || "Letter";

    // The <p> sibling after h1 contains "15 January, 1968 · Calcutta"
    const metaP = document.querySelector(
      "header p.text-muted-foreground, header p[class*='muted']",
    );
    const meta = metaP?.textContent?.trim() || null;

    return { title, detail: meta, url };
  }

  // /essays/[slug]
  if (parts[0] === "essays" && parts.length === 2) {
    const h1 = document.querySelector("h1");
    const title = h1?.textContent?.trim() || parts[1].replace(/-/g, " ");
    return { title, detail: "Essay by Śrīla Prabhupāda", url };
  }

  // /journals/[slug]/[chapter]
  if (parts[0] === "journals" && parts.length >= 3) {
    const backLink = document.querySelector("header a[href^='/journals/']");
    const parentTitle =
      backLink?.textContent?.replace(/^←\s*/, "").trim() || "Journal";
    const h1 = document.querySelector("h1");
    const chapterTitle = h1?.textContent?.trim() || null;
    return { title: parentTitle, detail: chapterTitle, url };
  }

  // /magazines/[slug]/[issue]
  if (parts[0] === "magazines" && parts.length >= 3) {
    const backLink = document.querySelector("header a[href^='/magazines/']");
    const parentTitle =
      backLink?.textContent?.replace(/^←\s*/, "").trim() || "Magazine";
    const h1 = document.querySelector("h1");
    const issueTitle = h1?.textContent?.trim() || null;
    return { title: parentTitle, detail: issueTitle, url };
  }

  // /other-documents/[slug]/[chapter]
  if (parts[0] === "other-documents" && parts.length >= 3) {
    const backLink = document.querySelector(
      "header a[href^='/other-documents/']",
    );
    const parentTitle =
      backLink?.textContent?.replace(/^←\s*/, "").trim() || "Document";
    const h1 = document.querySelector("h1");
    const chapterTitle = h1?.textContent?.trim() || null;
    return { title: parentTitle, detail: chapterTitle, url };
  }

  // /glossary — general
  if (parts[0] === "glossary") {
    return { title: "Glossary", detail: null, url };
  }

  // Fallback: try the h1
  const h1 = document.querySelector("h1");
  if (h1) {
    return {
      title: h1.textContent?.trim() || "Prabhupāda Says",
      detail: null,
      url,
    };
  }

  return null;
}

/**
 * Format selected text with source attribution appended.
 */
export function formatCopyText(selectedText: string): string {
  const ref = getSourceReference();
  if (!ref) return selectedText;

  const highlightUrl = buildHighlightUrl(selectedText);

  let source = `\n\nSource:\n${ref.title}`;
  if (ref.detail) source += `\n${ref.detail}`;
  source += `\n${highlightUrl}`;

  return selectedText + source;
}